An investigation into the replication biology of Helicoverpa armigera stunt virus
- Authors: Short, James Roswell
- Date: 2011
- Subjects: Helicoverpa armigera RNA viruses Viruses -- Reproduction Lepidoptera -- Viruses
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3967 , http://hdl.handle.net/10962/d1004026
- Description: Tetraviruses are a family of small non-enveloped positive sense RNA viruses that exclusively infect members of the order Lepidoptera. Their replication biology is poorly studied because, with the exception of Providence virus (PrV), tetraviruses are unable to replicate in tissue culture cells. The overall aim of the research described in this thesis was to develop a fundamental understanding of the replication of tetraviruses, focussing on the site of replication within host cells and in particular, the subcellular localisation of the viral replicase. Helicoverpa armigera stunt virus (HaSV, Genus: Omegatetravirus) was chosen for this study because it is the only tetravirus for which the cDNAs have been shown to be infectious. In the absence of tissue culture cell lines susceptible to HaSV infection, the approach was to use confocal fluorescence microscopy to examine the subcellular localisation of the HaSV replicase fused to enhanced green fluorescent protein (EGFP) in mammalian and insect tissue culture cells. The replicase (with EGFP fused at its C-terminus) localised to punctate structures throughout the cytoplasm of transfected HeLa and Sf9 cells. These structures were then shown – using live cell imaging and time lapse photography – to behave similarly to cellular endocytic organelles and fluorescence partially overlapped with membranes containing the late endosomal marker protein CD63. Biochemical fractionation of Sf9 cells expressing the replicase via a recombinant baculovirus (as well as transfected HeLa and Sf9 cells expressing EGFP-replicase fusion proteins) demonstrated that the replicase was strongly associated with detergentresistant membranes (DRMs) in these cells. Deletion analysis of the replicase coding sequence revealed two regions involved in the generation of the punctuate structures. Firstly, the C-terminal half of the replicase RNAdependant RNA polymerase domain was found to be essential for targeting and the tight association with DRMs while the second region, within the Nterminal 44 amino acids, enhanced localisation through a combination of secondary structural elements and sequence-specific functions. A comparative immunofluorescence study on PrV, which replicates as a persistent infection in an insect midgut cell line, showed that the PrV replicase also localised to punctate structures in the cytoplasm. Biochemical fractionation showed that the replicase was also strongly associated with DRMs. This thesis describes the development of new experimental systems for the study of tetravirus replication biology and the data lead to the conclusion that the HaSV replicase associates with DRMs derived from alternate endocytic pathway organelles.
- Full Text:
- Date Issued: 2011
- Authors: Short, James Roswell
- Date: 2011
- Subjects: Helicoverpa armigera RNA viruses Viruses -- Reproduction Lepidoptera -- Viruses
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3967 , http://hdl.handle.net/10962/d1004026
- Description: Tetraviruses are a family of small non-enveloped positive sense RNA viruses that exclusively infect members of the order Lepidoptera. Their replication biology is poorly studied because, with the exception of Providence virus (PrV), tetraviruses are unable to replicate in tissue culture cells. The overall aim of the research described in this thesis was to develop a fundamental understanding of the replication of tetraviruses, focussing on the site of replication within host cells and in particular, the subcellular localisation of the viral replicase. Helicoverpa armigera stunt virus (HaSV, Genus: Omegatetravirus) was chosen for this study because it is the only tetravirus for which the cDNAs have been shown to be infectious. In the absence of tissue culture cell lines susceptible to HaSV infection, the approach was to use confocal fluorescence microscopy to examine the subcellular localisation of the HaSV replicase fused to enhanced green fluorescent protein (EGFP) in mammalian and insect tissue culture cells. The replicase (with EGFP fused at its C-terminus) localised to punctate structures throughout the cytoplasm of transfected HeLa and Sf9 cells. These structures were then shown – using live cell imaging and time lapse photography – to behave similarly to cellular endocytic organelles and fluorescence partially overlapped with membranes containing the late endosomal marker protein CD63. Biochemical fractionation of Sf9 cells expressing the replicase via a recombinant baculovirus (as well as transfected HeLa and Sf9 cells expressing EGFP-replicase fusion proteins) demonstrated that the replicase was strongly associated with detergentresistant membranes (DRMs) in these cells. Deletion analysis of the replicase coding sequence revealed two regions involved in the generation of the punctuate structures. Firstly, the C-terminal half of the replicase RNAdependant RNA polymerase domain was found to be essential for targeting and the tight association with DRMs while the second region, within the Nterminal 44 amino acids, enhanced localisation through a combination of secondary structural elements and sequence-specific functions. A comparative immunofluorescence study on PrV, which replicates as a persistent infection in an insect midgut cell line, showed that the PrV replicase also localised to punctate structures in the cytoplasm. Biochemical fractionation showed that the replicase was also strongly associated with DRMs. This thesis describes the development of new experimental systems for the study of tetravirus replication biology and the data lead to the conclusion that the HaSV replicase associates with DRMs derived from alternate endocytic pathway organelles.
- Full Text:
- Date Issued: 2011
An investigation into the role of Xhosa male initiation in moral regeneration
- Authors: Ntombana, Luvuyo
- Date: 2011
- Subjects: Xhosa (African people) -- Rites and ceremonies , Initiation rites
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:16132 , http://hdl.handle.net/10948/d1006265 , Xhosa (African people) -- Rites and ceremonies , Initiation rites
- Description: This research study in Mdantsane (East London), Whittlesea (Hewu), Njiveni (Libode) and Cala sought to investigate the role of the amaXhosa male initiation in moral regeneration focusing on socio-cultural, educational and religious aspects related to moral values. The role of the amaXhosa male initiation as a rite of passage from boyhood to manhood, how it was viewed in the past, its impact upon the initiates and its contribution to the moral upholding of values were investigated. It was further intended to establish whether westernisation and urbanisation brought a shift of meaning and emphasis to the current initiation practice and, if so, to what extent has the ceremony departed from traditional norms and what challenges the ceremony has to face at present. A qualitative research method involving an ethnographic study was utilised, which includes in-depth, semi-structured interviews (formal interviews and informal discussions) and participant observation. Research findings suggested that in the past the amaXhosa male initiation played a role in the instruction of moral values. However, this study identified a shift of meaning in the practice which has been more evident in urban than in rural areas. The shift suggested that the instruction role has changed in prominence and there is less emphasis on teaching and appropriate adult behaviour. Moreover that the amakhankatha, who had the major role in teaching of the initiates are now participating in making the role less effective and sometimes introducing influences that are destructive to the initiates. Such negative influences include abuse of alcohol and drugs, promiscuity among the youth and disobedience of elders. It is argued that revisiting the teachings surrounding male initiation may cultivate productive debates on how young males are taught morality in today's society. Furthermore, that if the Xhosa male initiation could be contextualised it can play a role in the instruction of boys as they graduate to manhood and that can contribute to moral regeneration in South Africa.
- Full Text:
- Date Issued: 2011
- Authors: Ntombana, Luvuyo
- Date: 2011
- Subjects: Xhosa (African people) -- Rites and ceremonies , Initiation rites
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:16132 , http://hdl.handle.net/10948/d1006265 , Xhosa (African people) -- Rites and ceremonies , Initiation rites
- Description: This research study in Mdantsane (East London), Whittlesea (Hewu), Njiveni (Libode) and Cala sought to investigate the role of the amaXhosa male initiation in moral regeneration focusing on socio-cultural, educational and religious aspects related to moral values. The role of the amaXhosa male initiation as a rite of passage from boyhood to manhood, how it was viewed in the past, its impact upon the initiates and its contribution to the moral upholding of values were investigated. It was further intended to establish whether westernisation and urbanisation brought a shift of meaning and emphasis to the current initiation practice and, if so, to what extent has the ceremony departed from traditional norms and what challenges the ceremony has to face at present. A qualitative research method involving an ethnographic study was utilised, which includes in-depth, semi-structured interviews (formal interviews and informal discussions) and participant observation. Research findings suggested that in the past the amaXhosa male initiation played a role in the instruction of moral values. However, this study identified a shift of meaning in the practice which has been more evident in urban than in rural areas. The shift suggested that the instruction role has changed in prominence and there is less emphasis on teaching and appropriate adult behaviour. Moreover that the amakhankatha, who had the major role in teaching of the initiates are now participating in making the role less effective and sometimes introducing influences that are destructive to the initiates. Such negative influences include abuse of alcohol and drugs, promiscuity among the youth and disobedience of elders. It is argued that revisiting the teachings surrounding male initiation may cultivate productive debates on how young males are taught morality in today's society. Furthermore, that if the Xhosa male initiation could be contextualised it can play a role in the instruction of boys as they graduate to manhood and that can contribute to moral regeneration in South Africa.
- Full Text:
- Date Issued: 2011
An investigation of the attitudes of South African Police Service management with respect to the viability of computer-assisted training in the Eastern Cape Province
- Authors: Adams, Leinadu
- Date: 2011
- Subjects: Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8190 , http://hdl.handle.net/10948/1410 , Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Description: The South African Police Service (SAPS) as a constituent part of the public service was established to deliver a specific category of services to the public. These services have to conform to requirements that are prescribed by various legislative provisions to promote effective and efficient delivery of public services. The implications of these provisions that are pursued by the study firstly, refer to the emphasis of government on the enhancement of public service delivery, with due consideration given to cost effectiveness and efficiency. Secondly, it refers to government's realisation of the important impact of education, development and training (EDT) on the competency of public service officials with an emphasis on the utilisation of information technology to enhance the effectiveness of EDT. Consequently, the study explores the viability of the utilisation of information technology as a measure to assist EDT interventions within the SAPS of the Eastern Cape Province to equip members of the institution to better fulfil their functions and duties. In this respect the study commenced to ascertain the levels of computer literacy of role-players, access to the appropriate facilities and what the general attitude in the organisation would be towards the utilisation of such an intervention. It was found that the computer literacy levels of role-players may be perceived as a problematic issue in this regard. However, access to suitable facilities was found to be more than sufficient for this intention. Furthermore, role-players agreed that information technology could be optimally applied in the EC SAPS for the mentioned use, thereby portraying an optimistic attitude towards the use thereof to harmonise EDT in the SAPS. The aim of the study has been to develop a model that will incorporate the use of information technology, given the strengths and weaknesses of the SAPS to enhance EDT and learning in the organization.
- Full Text:
- Date Issued: 2011
- Authors: Adams, Leinadu
- Date: 2011
- Subjects: Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8190 , http://hdl.handle.net/10948/1410 , Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Description: The South African Police Service (SAPS) as a constituent part of the public service was established to deliver a specific category of services to the public. These services have to conform to requirements that are prescribed by various legislative provisions to promote effective and efficient delivery of public services. The implications of these provisions that are pursued by the study firstly, refer to the emphasis of government on the enhancement of public service delivery, with due consideration given to cost effectiveness and efficiency. Secondly, it refers to government's realisation of the important impact of education, development and training (EDT) on the competency of public service officials with an emphasis on the utilisation of information technology to enhance the effectiveness of EDT. Consequently, the study explores the viability of the utilisation of information technology as a measure to assist EDT interventions within the SAPS of the Eastern Cape Province to equip members of the institution to better fulfil their functions and duties. In this respect the study commenced to ascertain the levels of computer literacy of role-players, access to the appropriate facilities and what the general attitude in the organisation would be towards the utilisation of such an intervention. It was found that the computer literacy levels of role-players may be perceived as a problematic issue in this regard. However, access to suitable facilities was found to be more than sufficient for this intention. Furthermore, role-players agreed that information technology could be optimally applied in the EC SAPS for the mentioned use, thereby portraying an optimistic attitude towards the use thereof to harmonise EDT in the SAPS. The aim of the study has been to develop a model that will incorporate the use of information technology, given the strengths and weaknesses of the SAPS to enhance EDT and learning in the organization.
- Full Text:
- Date Issued: 2011
Assessing the impact of school governance in the Limpopo Department of Education with specific reference to Mankweng and Polokwane circuits
- Authors: Mothapo, Sentshuhleng Jacob
- Date: 2011
- Subjects: School management and organization -- South Africa -- Limpopo , Leadership -- South Africa -- Limpopo , Responsibility -- South Africa -- Limpopo , Teacher effectiveness -- South Africa -- Limpopo , School boards -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Doctoral , PhD (in Public Administration)
- Identifier: vital:11663 , http://hdl.handle.net/10353/d1007096 , School management and organization -- South Africa -- Limpopo , Leadership -- South Africa -- Limpopo , Responsibility -- South Africa -- Limpopo , Teacher effectiveness -- South Africa -- Limpopo , School boards -- South Africa -- Limpopo
- Description: Education has been identified as a priority area by the South African government, in particular by the African National Congress as the ruling party. To this end, huge amounts of money are being spent on education as a service that has been approved by the legislators. Rules and regulations have been promulgated, and among others, the South African Schools Act, Act No. 84 of 1996, has been enacted. Rich research has also been funded with the sole intention of providing quality education to the people. Education of unacceptably poor quality has, however, been the result, as postulated by Peterson and Hassel (1998:55). The above are attested to by the findings that the political tensions emanating from the conduct of the South African Democratic Teachers’ Union and the Professional Educators’ Union, leading to class disruptions and general instability, erode the ethos of accountability on the part of educators and therefore impact negatively on service delivery. Furthermore, the Limpopo Department of Education is not immune to the challenges ranging from the elements of corrupt activities that often surface, teacher attrition which in the main is caused by lack of discipline. Winkler, Modise and Dawber (1998) indicate that teaching has never been easy, and many teachers are leaving their jobs because of the many problems with children in classrooms. Some of the problems cited are children who do not want to learn and learning that is becoming too difficult for the students because they do not want to listen. This study adopted sequential mixed methods namely, quantitative and qualitative research methods which are viewed as complementary rather than opposing approaches. Information was amassed from the subjects through interviews, observation, documentary survey and observation and the information has since been triangulated to validate the facts. All the methodologies employed proved to be useful in this study. The study sought to test the hypothesis “Good governance is informed by strong accountability and future-oriented organisation, continuously steering it towards its mission and vision, and thereby ensuring that the day-to-day management and administration are always linked with the organisation’s values and goals and thus eventually bringing about effectual and accelerated service delivery” to the South African populace without compromise. After empirically testing the hypothesis, showing mixed reaction informed by the findings of the study, five recommendations were made, based on the conclusions arrived at.
- Full Text:
- Date Issued: 2011
- Authors: Mothapo, Sentshuhleng Jacob
- Date: 2011
- Subjects: School management and organization -- South Africa -- Limpopo , Leadership -- South Africa -- Limpopo , Responsibility -- South Africa -- Limpopo , Teacher effectiveness -- South Africa -- Limpopo , School boards -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Doctoral , PhD (in Public Administration)
- Identifier: vital:11663 , http://hdl.handle.net/10353/d1007096 , School management and organization -- South Africa -- Limpopo , Leadership -- South Africa -- Limpopo , Responsibility -- South Africa -- Limpopo , Teacher effectiveness -- South Africa -- Limpopo , School boards -- South Africa -- Limpopo
- Description: Education has been identified as a priority area by the South African government, in particular by the African National Congress as the ruling party. To this end, huge amounts of money are being spent on education as a service that has been approved by the legislators. Rules and regulations have been promulgated, and among others, the South African Schools Act, Act No. 84 of 1996, has been enacted. Rich research has also been funded with the sole intention of providing quality education to the people. Education of unacceptably poor quality has, however, been the result, as postulated by Peterson and Hassel (1998:55). The above are attested to by the findings that the political tensions emanating from the conduct of the South African Democratic Teachers’ Union and the Professional Educators’ Union, leading to class disruptions and general instability, erode the ethos of accountability on the part of educators and therefore impact negatively on service delivery. Furthermore, the Limpopo Department of Education is not immune to the challenges ranging from the elements of corrupt activities that often surface, teacher attrition which in the main is caused by lack of discipline. Winkler, Modise and Dawber (1998) indicate that teaching has never been easy, and many teachers are leaving their jobs because of the many problems with children in classrooms. Some of the problems cited are children who do not want to learn and learning that is becoming too difficult for the students because they do not want to listen. This study adopted sequential mixed methods namely, quantitative and qualitative research methods which are viewed as complementary rather than opposing approaches. Information was amassed from the subjects through interviews, observation, documentary survey and observation and the information has since been triangulated to validate the facts. All the methodologies employed proved to be useful in this study. The study sought to test the hypothesis “Good governance is informed by strong accountability and future-oriented organisation, continuously steering it towards its mission and vision, and thereby ensuring that the day-to-day management and administration are always linked with the organisation’s values and goals and thus eventually bringing about effectual and accelerated service delivery” to the South African populace without compromise. After empirically testing the hypothesis, showing mixed reaction informed by the findings of the study, five recommendations were made, based on the conclusions arrived at.
- Full Text:
- Date Issued: 2011
Biological control of Pereskia aculeata Miller (Cactaceae)
- Authors: Paterson, Iain Douglas
- Date: 2011
- Subjects: Pereskia -- Biological control -- South Africa Cactus -- Biological control -- South Africa Invasive plants -- Biological control -- South Africa Curculionidae -- South Africa Pyralidae -- South Africa Insects as biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5825 , http://hdl.handle.net/10962/d1007653
- Description: Pereskia aculeata Miller (Cactaceae) is an environmental weed that is damaging to natural ecosystems in South Africa. The plant is native to Central and South America and was first recorded in South Africa in a botanical garden in 1858. In this thesis, research into the biological control of P. aculeata was conducted with the intention of improving the control of the weed. A pre-release study of the relationship between P. aculeata density and native plant biodiversity indicated that P. aculeata has a negative impact on native biodiversity. The native plant biodiversity associated with different P. aculeata densities was used to determine threshold values and goals for the control of the weed. A threshold value of 50% P. aculeata density was calculated, indicating that P. aculeata density must be maintained below 50% in order to conserve native plant biodiversity. The ultimate goal of the control programme should be to maintain P. aculeata densities below 30%. At these densities there was no significant difference in native plant biodiversity from if the weed were absent from the ecosystem. The biological control agent, Phenrica guérini Bechyne (Chrysomelidae), has been released in South Africa but the potential of the agent to impact P. aculeata is not known and no post release evaluation has been conducted. Impact assessment studies indicate that P. guérini does not impact P. aculeata, even at high densities, but the results of greenhouse experiments should be interpreted with caution because of problems with extrapolation into the field. Although observations in the field suggest that P. guérini has reduced P. aculeata densities at one site, it is clear that new biological control agents are needed to reduce the weed to acceptable levels. Identifying the origin of the South African P. aculeata population was believed to be important to the biological control programme due to the disjunct native distribution and intraspecific variation of the species. Natural enemies associated with plant genotypes in different parts of the native distribution may have developed specialised relationships with certain intraspecific variants of the plant, resulting in differences in agent efficacy on certain host plant genotypes. A molecular study indicated that the closest relatives to the South African weed population found in the native distribution were in Rio de Janeiro Province, Brazil. A bioassay experiment in which fitness related traits of the biological control agent, P. guérini, were measured on various P. aculeata genotypes was conducted to determine the importance of host plant intraspecific variation. There was little variation in fitness traits between genotypes and no evidence of intraspecific host plant specialization. Although intraspecific variation had no effect on agent efficacy in the case of P. guérini, it is possible that other natural enemies may be more specialized. Genotype matching is expected to be more important when natural enemies likely to be specialised to individual genotypes are considered for biological control. Potential biological control agents were prioritized from data collected on surveys in the native distribution. The most promising of these, based on the presence of feeding, incidence, predicted host range, climatic matching, genotype matching and mode of damage, are two species of Curculionidae, the current biological control agent P. guérini and the stem boring moth, Maracayia chiorisalis Walker (Crambidae). The two curculionid species and M. chlorisalis should be considered priorities for host specificity studies. Releases of P. guérini and any new biological control agents should be made at sites where the pre-release study was conducted so that post-release evaluation data can be compared with the pre-release data and the impact of biological control can be evaluated. Retrospective analyses of biological control programmes provide important ways of improving aspects of biological control programmes, such as methods of agent selection. The evaluation of success in biological control programmes is essential for retrospective analyses because factors that have lead to successes or failures can be analysed. Retrospective analyses of biological control programmes, such as this thesis, may improve weed management, thereby contributing to the conservation of natural resources.
- Full Text:
- Date Issued: 2011
- Authors: Paterson, Iain Douglas
- Date: 2011
- Subjects: Pereskia -- Biological control -- South Africa Cactus -- Biological control -- South Africa Invasive plants -- Biological control -- South Africa Curculionidae -- South Africa Pyralidae -- South Africa Insects as biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5825 , http://hdl.handle.net/10962/d1007653
- Description: Pereskia aculeata Miller (Cactaceae) is an environmental weed that is damaging to natural ecosystems in South Africa. The plant is native to Central and South America and was first recorded in South Africa in a botanical garden in 1858. In this thesis, research into the biological control of P. aculeata was conducted with the intention of improving the control of the weed. A pre-release study of the relationship between P. aculeata density and native plant biodiversity indicated that P. aculeata has a negative impact on native biodiversity. The native plant biodiversity associated with different P. aculeata densities was used to determine threshold values and goals for the control of the weed. A threshold value of 50% P. aculeata density was calculated, indicating that P. aculeata density must be maintained below 50% in order to conserve native plant biodiversity. The ultimate goal of the control programme should be to maintain P. aculeata densities below 30%. At these densities there was no significant difference in native plant biodiversity from if the weed were absent from the ecosystem. The biological control agent, Phenrica guérini Bechyne (Chrysomelidae), has been released in South Africa but the potential of the agent to impact P. aculeata is not known and no post release evaluation has been conducted. Impact assessment studies indicate that P. guérini does not impact P. aculeata, even at high densities, but the results of greenhouse experiments should be interpreted with caution because of problems with extrapolation into the field. Although observations in the field suggest that P. guérini has reduced P. aculeata densities at one site, it is clear that new biological control agents are needed to reduce the weed to acceptable levels. Identifying the origin of the South African P. aculeata population was believed to be important to the biological control programme due to the disjunct native distribution and intraspecific variation of the species. Natural enemies associated with plant genotypes in different parts of the native distribution may have developed specialised relationships with certain intraspecific variants of the plant, resulting in differences in agent efficacy on certain host plant genotypes. A molecular study indicated that the closest relatives to the South African weed population found in the native distribution were in Rio de Janeiro Province, Brazil. A bioassay experiment in which fitness related traits of the biological control agent, P. guérini, were measured on various P. aculeata genotypes was conducted to determine the importance of host plant intraspecific variation. There was little variation in fitness traits between genotypes and no evidence of intraspecific host plant specialization. Although intraspecific variation had no effect on agent efficacy in the case of P. guérini, it is possible that other natural enemies may be more specialized. Genotype matching is expected to be more important when natural enemies likely to be specialised to individual genotypes are considered for biological control. Potential biological control agents were prioritized from data collected on surveys in the native distribution. The most promising of these, based on the presence of feeding, incidence, predicted host range, climatic matching, genotype matching and mode of damage, are two species of Curculionidae, the current biological control agent P. guérini and the stem boring moth, Maracayia chiorisalis Walker (Crambidae). The two curculionid species and M. chlorisalis should be considered priorities for host specificity studies. Releases of P. guérini and any new biological control agents should be made at sites where the pre-release study was conducted so that post-release evaluation data can be compared with the pre-release data and the impact of biological control can be evaluated. Retrospective analyses of biological control programmes provide important ways of improving aspects of biological control programmes, such as methods of agent selection. The evaluation of success in biological control programmes is essential for retrospective analyses because factors that have lead to successes or failures can be analysed. Retrospective analyses of biological control programmes, such as this thesis, may improve weed management, thereby contributing to the conservation of natural resources.
- Full Text:
- Date Issued: 2011
Characterization and electrocatalytic applications of metallophthalocyanine-single walled carbon nanotube conjugates
- Authors: Mugadza, Tawanda
- Date: 2011 , 2011-03-30
- Subjects: Phthalocyanines Pesticides Nanotubes Electrocatalysis Electrochemistry Transmission electron microscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4419 , http://hdl.handle.net/10962/d1006855
- Description: Metallophthalocyanine-single walled carbon nanotube conjugates were successfully synthesized and applied in the electrochemical characterizations of pesticides (amitrole and diuron) and 2-mercaptoethanol (2-ME). The formation of conjugates was confirmed through the use of the following analytical techniques: UV-vis, FTIR, Raman and XRD spectroscopies, atomic force and transmission electron microscopies and voltammetry. Chemically linking SWCNT to MPcs created platforms that offered efficient transfer of electrons and this was confirmed through electrochemical impedance studies (EIS) and voltammetry as shown by lower ΔEp values observed in conjugates. Carboxy carrying MPcs have very poor electron transfer kinetics (both tetrasubstituted and low symmetry), but the presence of SWCNTs activates their catalysis. All electrochemical studies were done at pH 4. Cyclic voltammetry, rotating disk linear sweep voltammetry, chronoamperometry and EIS were used in the electrochemical characterization of 2-ME and the pesticides on poly-Ni(OH)TAPc and MPc-SWCNT modified glassy carbon electrodes (GCEs). High Tafel slopes were observed for the pesticides relative to 2-ME, an indication of the passivating nature of their oxidation products. However, conjugates showed very high resistances to passivation and were easily regenerated by shaking in methanol. Improved catalysis of the conjugates is also indicated by the high catalytic rate constants for the analytes, observed on these electrodes. Conjugates of low symmetry MPcs with SWCNTs gave the highest catalytic rate constants, confirming better catalysis on these electrode surfaces. The nature of SWCNT functionalization also affected catalysis, with amine functionalized SWCNTs inducing better catalytic properties into the MPcs than carboxylic acid terminated CNTs. The presence of amine functionalized SWCNTs activates the catalysis of non-catalytic carboxy-carrying MPcs and this is more pronounced in conjugates of tetrasubstituted MPcs relative to those of low symmetry Pcs. Ethylene amine (EA) functionalized SWCNTs reduced redox overpotentials of the MPcs more than the phenyl-amine (PA) functionalized counterparts. Poly-NiTAPc was successfully converted to poly-Ni(OH)TAPc through cyclisation in pH 4 buffer and showed very good catalytic properties towards diuron, relative to the former.
- Full Text:
- Date Issued: 2011
- Authors: Mugadza, Tawanda
- Date: 2011 , 2011-03-30
- Subjects: Phthalocyanines Pesticides Nanotubes Electrocatalysis Electrochemistry Transmission electron microscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4419 , http://hdl.handle.net/10962/d1006855
- Description: Metallophthalocyanine-single walled carbon nanotube conjugates were successfully synthesized and applied in the electrochemical characterizations of pesticides (amitrole and diuron) and 2-mercaptoethanol (2-ME). The formation of conjugates was confirmed through the use of the following analytical techniques: UV-vis, FTIR, Raman and XRD spectroscopies, atomic force and transmission electron microscopies and voltammetry. Chemically linking SWCNT to MPcs created platforms that offered efficient transfer of electrons and this was confirmed through electrochemical impedance studies (EIS) and voltammetry as shown by lower ΔEp values observed in conjugates. Carboxy carrying MPcs have very poor electron transfer kinetics (both tetrasubstituted and low symmetry), but the presence of SWCNTs activates their catalysis. All electrochemical studies were done at pH 4. Cyclic voltammetry, rotating disk linear sweep voltammetry, chronoamperometry and EIS were used in the electrochemical characterization of 2-ME and the pesticides on poly-Ni(OH)TAPc and MPc-SWCNT modified glassy carbon electrodes (GCEs). High Tafel slopes were observed for the pesticides relative to 2-ME, an indication of the passivating nature of their oxidation products. However, conjugates showed very high resistances to passivation and were easily regenerated by shaking in methanol. Improved catalysis of the conjugates is also indicated by the high catalytic rate constants for the analytes, observed on these electrodes. Conjugates of low symmetry MPcs with SWCNTs gave the highest catalytic rate constants, confirming better catalysis on these electrode surfaces. The nature of SWCNT functionalization also affected catalysis, with amine functionalized SWCNTs inducing better catalytic properties into the MPcs than carboxylic acid terminated CNTs. The presence of amine functionalized SWCNTs activates the catalysis of non-catalytic carboxy-carrying MPcs and this is more pronounced in conjugates of tetrasubstituted MPcs relative to those of low symmetry Pcs. Ethylene amine (EA) functionalized SWCNTs reduced redox overpotentials of the MPcs more than the phenyl-amine (PA) functionalized counterparts. Poly-NiTAPc was successfully converted to poly-Ni(OH)TAPc through cyclisation in pH 4 buffer and showed very good catalytic properties towards diuron, relative to the former.
- Full Text:
- Date Issued: 2011
Climate change adaptation and economic valuation of local pig genetic resources in communal production systems of South Africa
- Authors: Madzimure, James
- Date: 2011
- Subjects: Swine -- Breeding -- South Africa , Swine -- Feeding and feeds -- South Africa , Swine -- Genetics , Swine -- Nutrition -- Requirements , Climate change mitigation -- Environmental aspects , Swine -- Diseases -- South Africa , Commons -- Conservation --South Africa , Natural resources, Communal -- Management , Genotype-environment interaction -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD (Animal Science)
- Identifier: vital:11805 , http://hdl.handle.net/10353/427 , Swine -- Breeding -- South Africa , Swine -- Feeding and feeds -- South Africa , Swine -- Genetics , Swine -- Nutrition -- Requirements , Climate change mitigation -- Environmental aspects , Swine -- Diseases -- South Africa , Commons -- Conservation --South Africa , Natural resources, Communal -- Management , Genotype-environment interaction -- South Africa
- Description: The broad objective of the study was to determine the economic value of local pigs in marketand subsistence-oriented production systems in communal areas of Southern Africa. Data were collected from 288 households to investigate farmer perceptions, effects on pig production and handling of disease outbreaks such as classical swine fever (CSF) in market- and subsistenceoriented production systems. The utilisation of local pigs in these market- and subsistenceoriented production systems in improving people‟s welfare was evaluated. Climate change was identified by farmers in these production systems as a major constraint to pig production hence an experiment was carried out in the hottest season to determine diurnal heat-related physiological and behavioural responses in Large White (LW) and South African local pigs. The same genotypes were used to determine effects of diurnal heat-related stress on their growth performance. Choice experiment was done to determine farmer preferences for local pig traits and implicit prices for these traits in CSF-affected and unaffected areas that were under subsistence- and market-oriented production systems. In this experiment, the importance of heat tolerance was assessed relative to other productive and climate change adaptation traits. Significantly more pigs were culled in the CSF-affected areas that were market-oriented (8.0 ± 1.76) than subsistence-oriented (4.1 ± 1.00) production system. The risk of parasites and disease challenges was high in subsistence-oriented production system and coastal areas. In both production systems, CSF was perceived as destructive since the culling of pigs affected pork availability and income generation. The high risk of disease outbreaks and threat of climate change caused farmers in subsistence-oriented production system to select local pigs for their adaptive traits while those in the market-oriented production system focused on productive imported pigs. Farmers (83 %) indicated that they wanted pig genotypes that were adapted to climate change effects such as hot conditions. Local pigs were found to have superior heat tolerance over LW pigs (P < 0.05) in terms of lower heart rate and skin surface temperature. Frequency per day and duration for behavioural heat loss activities such as wallowing, sleeping in a prostrate posture and sprawling in slurry were also lower (P < 0.05) for local than LW pigs. The superiority of heat tolerance of local over LW pigs was further confirmed by their uncompromised growth performance under high diurnal temperatures. The Pearson‟s product moment correlation coefficient between temperature and feed conversion ratio for LW pigs was strongly positive (r = 0.50; P < 0.001) unlike the weak and positive correlation for local pigs (r = 0.20; P < 0.05). There was a quadratic relationship between temperature and average daily gain (ADG) for both pig genotypes. The regression coefficients for ADG were higher (P < 0.001) for LW than local pigs. It was concluded that at high ambient temperatures, performance of local pigs was less compromised than for LW pigs. Although local pigs were found to be heat tolerant, results of choice experiment showed that this trait was not selected for relative to other traits. Keeping pigs that required bought-in feeds, fell sick often and produced low pork quality (eating quality based on farmer perceptions) negatively affected farmers‟ livelihoods more in subsistence- than market-oriented production system. Farmers in market-oriented production system derived more benefit from productive traits such as heavier slaughter weights and large litter size than subsistence-oriented farmers. Under the subsistence-oriented production system, farmers in CSF-affected areas placed high prices on adaptive traits than the unaffected areas. Subsistence-oriented farmers who were affected by CSF wanted a total compensation price of R10 944.00 (USD1563.43) for keeping a pig genotype with unfavourable traits when compared to R4235.00 (USD605.00) for their CSF-unaffected counterparts. Implicit prices for traits could not be determined for market-oriented production system. It was concluded that farmers in CSFaffected areas placed high economic values on pig traits than farmers from the CSF-unaffected areas. The findings suggest that adapted local pigs can be promoted in subsistence-oriented production systems while productive imported pigs and their crosses with local pigs can be kept in market-oriented production systems.
- Full Text:
- Date Issued: 2011
- Authors: Madzimure, James
- Date: 2011
- Subjects: Swine -- Breeding -- South Africa , Swine -- Feeding and feeds -- South Africa , Swine -- Genetics , Swine -- Nutrition -- Requirements , Climate change mitigation -- Environmental aspects , Swine -- Diseases -- South Africa , Commons -- Conservation --South Africa , Natural resources, Communal -- Management , Genotype-environment interaction -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD (Animal Science)
- Identifier: vital:11805 , http://hdl.handle.net/10353/427 , Swine -- Breeding -- South Africa , Swine -- Feeding and feeds -- South Africa , Swine -- Genetics , Swine -- Nutrition -- Requirements , Climate change mitigation -- Environmental aspects , Swine -- Diseases -- South Africa , Commons -- Conservation --South Africa , Natural resources, Communal -- Management , Genotype-environment interaction -- South Africa
- Description: The broad objective of the study was to determine the economic value of local pigs in marketand subsistence-oriented production systems in communal areas of Southern Africa. Data were collected from 288 households to investigate farmer perceptions, effects on pig production and handling of disease outbreaks such as classical swine fever (CSF) in market- and subsistenceoriented production systems. The utilisation of local pigs in these market- and subsistenceoriented production systems in improving people‟s welfare was evaluated. Climate change was identified by farmers in these production systems as a major constraint to pig production hence an experiment was carried out in the hottest season to determine diurnal heat-related physiological and behavioural responses in Large White (LW) and South African local pigs. The same genotypes were used to determine effects of diurnal heat-related stress on their growth performance. Choice experiment was done to determine farmer preferences for local pig traits and implicit prices for these traits in CSF-affected and unaffected areas that were under subsistence- and market-oriented production systems. In this experiment, the importance of heat tolerance was assessed relative to other productive and climate change adaptation traits. Significantly more pigs were culled in the CSF-affected areas that were market-oriented (8.0 ± 1.76) than subsistence-oriented (4.1 ± 1.00) production system. The risk of parasites and disease challenges was high in subsistence-oriented production system and coastal areas. In both production systems, CSF was perceived as destructive since the culling of pigs affected pork availability and income generation. The high risk of disease outbreaks and threat of climate change caused farmers in subsistence-oriented production system to select local pigs for their adaptive traits while those in the market-oriented production system focused on productive imported pigs. Farmers (83 %) indicated that they wanted pig genotypes that were adapted to climate change effects such as hot conditions. Local pigs were found to have superior heat tolerance over LW pigs (P < 0.05) in terms of lower heart rate and skin surface temperature. Frequency per day and duration for behavioural heat loss activities such as wallowing, sleeping in a prostrate posture and sprawling in slurry were also lower (P < 0.05) for local than LW pigs. The superiority of heat tolerance of local over LW pigs was further confirmed by their uncompromised growth performance under high diurnal temperatures. The Pearson‟s product moment correlation coefficient between temperature and feed conversion ratio for LW pigs was strongly positive (r = 0.50; P < 0.001) unlike the weak and positive correlation for local pigs (r = 0.20; P < 0.05). There was a quadratic relationship between temperature and average daily gain (ADG) for both pig genotypes. The regression coefficients for ADG were higher (P < 0.001) for LW than local pigs. It was concluded that at high ambient temperatures, performance of local pigs was less compromised than for LW pigs. Although local pigs were found to be heat tolerant, results of choice experiment showed that this trait was not selected for relative to other traits. Keeping pigs that required bought-in feeds, fell sick often and produced low pork quality (eating quality based on farmer perceptions) negatively affected farmers‟ livelihoods more in subsistence- than market-oriented production system. Farmers in market-oriented production system derived more benefit from productive traits such as heavier slaughter weights and large litter size than subsistence-oriented farmers. Under the subsistence-oriented production system, farmers in CSF-affected areas placed high prices on adaptive traits than the unaffected areas. Subsistence-oriented farmers who were affected by CSF wanted a total compensation price of R10 944.00 (USD1563.43) for keeping a pig genotype with unfavourable traits when compared to R4235.00 (USD605.00) for their CSF-unaffected counterparts. Implicit prices for traits could not be determined for market-oriented production system. It was concluded that farmers in CSFaffected areas placed high economic values on pig traits than farmers from the CSF-unaffected areas. The findings suggest that adapted local pigs can be promoted in subsistence-oriented production systems while productive imported pigs and their crosses with local pigs can be kept in market-oriented production systems.
- Full Text:
- Date Issued: 2011
Comparative study of the feeding damage caused by the South African biotypes of the Russian wheat aphid (Diuraphis noxia Kurdjumov) on resistant and non-resistant lines of barley (Hordeum vulgare L.)
- Authors: Jimoh, Mahboob Adekilekun
- Date: 2011
- Subjects: Aphids Russian wheat aphid -- Research -- South Africa Barley -- Diseases and pests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4201 , http://hdl.handle.net/10962/d1003770
- Description: Cereal crop productivity is hampered when these plants are infested by phloem feeding aphids. A great deal of research has been carried out with the direct aim of a clearer understanding of the mechanism involved in the interaction between aphids and their host plants. Research has directly or indirectly been geared towards enhanced plant productivity and achieving sustainable agriculture. Barley (Hordeum vulgare L.) is an important small grain crop in South Africa, whose crop performance is negatively affected by fluctuations in weather patterns as well as by agricultural pests. One of the insect pests infesting barley is the Russian wheat aphid, Diuraphis noxia Kurdjumov (RWA), of which the two South African biotypes, codenamed RWASA1 and RWASA2, were studied in this thesis. During dry spells, RWA infestation becomes a more serious threat to barley productivity. Resistant plants have been used to combat RWA infestation of small grains. In South Africa, 27 RWA-resistant wheat cultivars are currently used in commercial cultivation, but no resistant barley lines have, unfortunately, been developed, in spite of this grain’s significant economic importance. This informed the study in this thesis, and this interest particularly focussed on three RWA-resistant lines developed by the USDA, testing their performance against South African RWA biotypes, for possible adaptation to South Africa. The aim was thus to examine the plant-aphid interactions, aphid breeding rates, plant damage and sustainability, evidence of resistance or tolerance and finally potential performance under elevated CO2 (a very real climate change threat). Two major avenues of research were undertaken. The first aspect involved examination of structural and functional damage caused by RWASA1 and RWASA2 on the three resistant and a non-resistant line. Aphid population growth and damage symptoms (chlorosis and leaf roll) of infestation by these aphid biotypes were evaluated. This was followed by a structural and functional approach in which the effects of feeding on the transport systems (phloem and xylem) of barley were investigated. Fluorescence microscopy techniques (using aniline blue fluorochrome, a specific stain for callose and 5,6-CFDA, a phloem-mobile probe) were applied to investigate the feeding-related damage caused by the aphids, through an examination of wound callose formation and related to this, the resultant reduction in phloem transport capacity. Transmission electron microscopy (TEM) techniques provided evidence of the extent of the feeding-related cell damage. The second aspect involved a study of the effect of changing CO2 concentrations ([CO2]) on the resistant and susceptible barley cultivars to feeding by the two RWA biotypes. Leaves of plants grown at ambient and two elevated levels of [CO2] were analysed to investigate the effect of changing [CO2] on biomass, leaf nitrogen content and C:N ratio of control (uninfested) and infested plants. The population growth studies showed that the populations of the two RWA biotypes as well as bird cherry-oat aphid (BCA, Rhopalosiphum padi L.) increased substantially on the four barley lines. BCA was included here, as it had been the subject of several previous studies. RWASA2 bred faster than RWASA1 on all lines. The breeding rates of the two RWA biotypes were both suppressed and at near-equivalent levels on the three resistant lines, compared to the non-resistant PUMA. This suggests that the resistant lines possessed an antibiosis resistance mechanism against the feeding aphids. Feeding by the aphids manifested in morphological damage symptoms of chlorosis and leaf roll. The two biotypes inflicted severe chlorosis and leaf roll on the non-resistant PUMA. In the resistant plants, leaf rolling was more severe because of RWASA2 feeding compared to RWASA1 feeding. In contrast, chlorosis symptoms were more severe during RWASA1 feeding than was the case with RWASA2 feeding. Investigation of the effect of aphid feeding on the plants showed that callose was deposited within 24h and that this increased with longer feeding exposure. Wound callose distribution is more extensive in the non-resistant PUMA than in the resistant plants. RWASA2 feeding on the resistant lines caused deposition of more callose than was evident with RWASA1 feeding. During long-term feeding, it was evident that variation in the intensity and amount of wound callose was visible in the longitudinal and transverse veins of the resistant plants. Of the three STARS plants, STARS-9301B had the least callose. Interestingly, wound callose occurred in both resistant and non-resistant plants, in sharp contrast to what has been reported on resistant wheat cultivars that were developed in South Africa. The relative reduction in the wound callose deposited in the resistant line, when compared to the non-resistant lines, suggests the presence of a mechanism in the resistant lines, which may prevent excessive callose formation. Alternatively, the mechanism may stimulate callose breakdown. RWASA2 feeding on the resistant lines deposited more wound callose than RWASA1 feeding. This evidence supports the hypothesis that RWASA2 is a resistance breaking and more aggressive feeder than RWASA1 is; and further underscores the urgent need for development of RWA-resistant barley cultivars. The ultrastructural investigation of the feeding damage showed that the two biotypes caused extensive vascular damage in non-resistant plants. There was extensive and severe cell disruption and often obliteration of cell structure of the vascular parenchyma, xylem and phloem elements. In sharp contrast, among the resistant plants, feeding-related cell damage appeared to be substantially reduced compared to the non-resistant PUMA. Low frequency of damaged cells indicated that majority of the cell components of the vascular tissues were intact and presumed functional. There was evidence of salivary material lining the secondary walls of the vascular tissue, which resulted in severe damage. Within xylem vessels, saliva material impregnated half-bordered pit pairs between the vessels and adjacent xylem parenchyma. This is believed to prevent solute exchange through this interface, thereby inducing leaf stress and vi leaf roll. A notable finding is that RWASA2 effectively induced more cell damage to vascular tissues in the resistant lines than did RWASA1. In general the experimental evidence (see Chapter 5) suggests that the resistant lines are possibly more tolerant (or able to cope with) to RWA feeding. Evidence for this is the reduction of wound callose and at the TEM level, a comparatively less obvious cell damage in the resistant lines, which suggests that they possess antibiosis and tolerance capacity. The apparent reduction of feeding-related cell damage from the TEM study confirmed the disruptive action of the feeding aphids in experiments using the phloem-mobile probe, 5,6-CF. Results showed that feeding by RWASA1 and RWASA2 reducedthe transport functionality of the phloem in all cases, but that RWASA2 feeding caused a more obvious reduction in the rate and distance that 5,6-carboxyfluorescein was transported, than did RWASA1. Investigation of the effect of changing [CO2] on the barley cultivars showed that in the absence of aphids and under elevated CO2 conditions, the plants grew more vigorously. In this series of experiments, the infested plants suffered significant reduction in biomass under ambient (as was expected) and under the two elevated CO2 regimes. Biomass loss was greater at elevated CO2 than under ambient [CO2]. The infested nonresistant PUMA plants showed a more significant biomass loss than did the resistant cultivars. Clearly, the benefits derived from elevated CO2 enrichment was thus redirected to the now-advantaged aphids. Uninfested vii plants showed an increase in leaf nitrogen under the experimental conditions. However, feeding aphids depleted leaf nitrogen content and this was more apparent on plants exposed to RWASA2 than was the case with RWASA1. The end result of this was that C:N ratio of infested plants were higher than uninfested plants. Clearly, the faster breeding rates of the aphids at elevated CO2 caused depletion of N and a resultant deficiency exacerbated chlorosis as well as leaf rolling due to the higher aphid population density under elevated CO2 than at ambient. By 28 days after infestation (DAI), majority of the plants exposed to enriched CO2 treatments had died. A major finding here was thus that although this study demonstrated that elevated CO2 resulted in an increase in biomass, this was detrimentally offset in plants infested by the aphids, with a decline in biomass and loss of functionality leading to plant death at 28DAI. The overriding conclusion from this study is a clear signal that the twin effects of CO2 enrichment (a feature of current climate change) and aphid infestations may precipitate potential grain shortages. A disastrous food security threat looms.
- Full Text:
- Date Issued: 2011
- Authors: Jimoh, Mahboob Adekilekun
- Date: 2011
- Subjects: Aphids Russian wheat aphid -- Research -- South Africa Barley -- Diseases and pests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4201 , http://hdl.handle.net/10962/d1003770
- Description: Cereal crop productivity is hampered when these plants are infested by phloem feeding aphids. A great deal of research has been carried out with the direct aim of a clearer understanding of the mechanism involved in the interaction between aphids and their host plants. Research has directly or indirectly been geared towards enhanced plant productivity and achieving sustainable agriculture. Barley (Hordeum vulgare L.) is an important small grain crop in South Africa, whose crop performance is negatively affected by fluctuations in weather patterns as well as by agricultural pests. One of the insect pests infesting barley is the Russian wheat aphid, Diuraphis noxia Kurdjumov (RWA), of which the two South African biotypes, codenamed RWASA1 and RWASA2, were studied in this thesis. During dry spells, RWA infestation becomes a more serious threat to barley productivity. Resistant plants have been used to combat RWA infestation of small grains. In South Africa, 27 RWA-resistant wheat cultivars are currently used in commercial cultivation, but no resistant barley lines have, unfortunately, been developed, in spite of this grain’s significant economic importance. This informed the study in this thesis, and this interest particularly focussed on three RWA-resistant lines developed by the USDA, testing their performance against South African RWA biotypes, for possible adaptation to South Africa. The aim was thus to examine the plant-aphid interactions, aphid breeding rates, plant damage and sustainability, evidence of resistance or tolerance and finally potential performance under elevated CO2 (a very real climate change threat). Two major avenues of research were undertaken. The first aspect involved examination of structural and functional damage caused by RWASA1 and RWASA2 on the three resistant and a non-resistant line. Aphid population growth and damage symptoms (chlorosis and leaf roll) of infestation by these aphid biotypes were evaluated. This was followed by a structural and functional approach in which the effects of feeding on the transport systems (phloem and xylem) of barley were investigated. Fluorescence microscopy techniques (using aniline blue fluorochrome, a specific stain for callose and 5,6-CFDA, a phloem-mobile probe) were applied to investigate the feeding-related damage caused by the aphids, through an examination of wound callose formation and related to this, the resultant reduction in phloem transport capacity. Transmission electron microscopy (TEM) techniques provided evidence of the extent of the feeding-related cell damage. The second aspect involved a study of the effect of changing CO2 concentrations ([CO2]) on the resistant and susceptible barley cultivars to feeding by the two RWA biotypes. Leaves of plants grown at ambient and two elevated levels of [CO2] were analysed to investigate the effect of changing [CO2] on biomass, leaf nitrogen content and C:N ratio of control (uninfested) and infested plants. The population growth studies showed that the populations of the two RWA biotypes as well as bird cherry-oat aphid (BCA, Rhopalosiphum padi L.) increased substantially on the four barley lines. BCA was included here, as it had been the subject of several previous studies. RWASA2 bred faster than RWASA1 on all lines. The breeding rates of the two RWA biotypes were both suppressed and at near-equivalent levels on the three resistant lines, compared to the non-resistant PUMA. This suggests that the resistant lines possessed an antibiosis resistance mechanism against the feeding aphids. Feeding by the aphids manifested in morphological damage symptoms of chlorosis and leaf roll. The two biotypes inflicted severe chlorosis and leaf roll on the non-resistant PUMA. In the resistant plants, leaf rolling was more severe because of RWASA2 feeding compared to RWASA1 feeding. In contrast, chlorosis symptoms were more severe during RWASA1 feeding than was the case with RWASA2 feeding. Investigation of the effect of aphid feeding on the plants showed that callose was deposited within 24h and that this increased with longer feeding exposure. Wound callose distribution is more extensive in the non-resistant PUMA than in the resistant plants. RWASA2 feeding on the resistant lines caused deposition of more callose than was evident with RWASA1 feeding. During long-term feeding, it was evident that variation in the intensity and amount of wound callose was visible in the longitudinal and transverse veins of the resistant plants. Of the three STARS plants, STARS-9301B had the least callose. Interestingly, wound callose occurred in both resistant and non-resistant plants, in sharp contrast to what has been reported on resistant wheat cultivars that were developed in South Africa. The relative reduction in the wound callose deposited in the resistant line, when compared to the non-resistant lines, suggests the presence of a mechanism in the resistant lines, which may prevent excessive callose formation. Alternatively, the mechanism may stimulate callose breakdown. RWASA2 feeding on the resistant lines deposited more wound callose than RWASA1 feeding. This evidence supports the hypothesis that RWASA2 is a resistance breaking and more aggressive feeder than RWASA1 is; and further underscores the urgent need for development of RWA-resistant barley cultivars. The ultrastructural investigation of the feeding damage showed that the two biotypes caused extensive vascular damage in non-resistant plants. There was extensive and severe cell disruption and often obliteration of cell structure of the vascular parenchyma, xylem and phloem elements. In sharp contrast, among the resistant plants, feeding-related cell damage appeared to be substantially reduced compared to the non-resistant PUMA. Low frequency of damaged cells indicated that majority of the cell components of the vascular tissues were intact and presumed functional. There was evidence of salivary material lining the secondary walls of the vascular tissue, which resulted in severe damage. Within xylem vessels, saliva material impregnated half-bordered pit pairs between the vessels and adjacent xylem parenchyma. This is believed to prevent solute exchange through this interface, thereby inducing leaf stress and vi leaf roll. A notable finding is that RWASA2 effectively induced more cell damage to vascular tissues in the resistant lines than did RWASA1. In general the experimental evidence (see Chapter 5) suggests that the resistant lines are possibly more tolerant (or able to cope with) to RWA feeding. Evidence for this is the reduction of wound callose and at the TEM level, a comparatively less obvious cell damage in the resistant lines, which suggests that they possess antibiosis and tolerance capacity. The apparent reduction of feeding-related cell damage from the TEM study confirmed the disruptive action of the feeding aphids in experiments using the phloem-mobile probe, 5,6-CF. Results showed that feeding by RWASA1 and RWASA2 reducedthe transport functionality of the phloem in all cases, but that RWASA2 feeding caused a more obvious reduction in the rate and distance that 5,6-carboxyfluorescein was transported, than did RWASA1. Investigation of the effect of changing [CO2] on the barley cultivars showed that in the absence of aphids and under elevated CO2 conditions, the plants grew more vigorously. In this series of experiments, the infested plants suffered significant reduction in biomass under ambient (as was expected) and under the two elevated CO2 regimes. Biomass loss was greater at elevated CO2 than under ambient [CO2]. The infested nonresistant PUMA plants showed a more significant biomass loss than did the resistant cultivars. Clearly, the benefits derived from elevated CO2 enrichment was thus redirected to the now-advantaged aphids. Uninfested vii plants showed an increase in leaf nitrogen under the experimental conditions. However, feeding aphids depleted leaf nitrogen content and this was more apparent on plants exposed to RWASA2 than was the case with RWASA1. The end result of this was that C:N ratio of infested plants were higher than uninfested plants. Clearly, the faster breeding rates of the aphids at elevated CO2 caused depletion of N and a resultant deficiency exacerbated chlorosis as well as leaf rolling due to the higher aphid population density under elevated CO2 than at ambient. By 28 days after infestation (DAI), majority of the plants exposed to enriched CO2 treatments had died. A major finding here was thus that although this study demonstrated that elevated CO2 resulted in an increase in biomass, this was detrimentally offset in plants infested by the aphids, with a decline in biomass and loss of functionality leading to plant death at 28DAI. The overriding conclusion from this study is a clear signal that the twin effects of CO2 enrichment (a feature of current climate change) and aphid infestations may precipitate potential grain shortages. A disastrous food security threat looms.
- Full Text:
- Date Issued: 2011
Conflict and sustainable development: the case of the great Limpompo Transfrontier Park (GLTP), Southern Africa
- Authors: Muboko, Never
- Date: 2011
- Subjects: Conflict management , Sustainable development -- South Africa -- Limpopo , Great Limpopo Transfrontier Park
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8158 , http://hdl.handle.net/10948/1357 , Conflict management , Sustainable development -- South Africa -- Limpopo , Great Limpopo Transfrontier Park
- Description: Conflict is inevitable but sustainable development is achievable. An analysis of the mix between development and conflict in two communities revealed the imperatives needed to strike a balance between conflict and sustainable development. While conflicts over natural resources are neither a new phenomenon nor are they inevitable, it is the approaches adopted to manage them that generate interests and makes a difference between peace and violence. Thus, conflicts associated with wilderness or TFCA development initiatives such as the Great Limpopo Transfrontier Park (GLTP) have attracted significant interest from various stakeholders. While the GLTP is a flagship conservation initiative in Southern Africa designed to integrate different land uses for socio-economic development, it is littered with conflicts. Through documenting the experiences of two communities involved in development conflicts, a determination was sought to understand the efficacy of approaches used to manage the conflict. Using mainly questionnaires and personal interviews, perceptions and attitudes of key informants were solicited. Unresolved historical problems reincarnated to haunt current conservation projects as memories of unresolved past events reflected negatively on new related initiatives. Different approaches adopted in managing these conflicts resulted in significantly different outcomes. Local stakeholder involvements were inadequate, but were identified as pertinent to successful sustainable conservation and development. Unless local communities are assured of real benefits from new conservation initiatives it became evident that recurrent conflicts would be inevitable. The findings reveal that current conservation initiatives should be underpinned by emerging inclusivity theories in the conservation discourse. A broad range of stakeholders should embrace this new paradigm based on the philosophy that conservation efforts that exclude local communities are bound to be unsustainable. We found out that it is in the interests of all for policy makers to come up with policies that recognise the critical role local communities play, while subscribing to the regional and international standards for best practices in the conservation business.
- Full Text:
- Date Issued: 2011
- Authors: Muboko, Never
- Date: 2011
- Subjects: Conflict management , Sustainable development -- South Africa -- Limpopo , Great Limpopo Transfrontier Park
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8158 , http://hdl.handle.net/10948/1357 , Conflict management , Sustainable development -- South Africa -- Limpopo , Great Limpopo Transfrontier Park
- Description: Conflict is inevitable but sustainable development is achievable. An analysis of the mix between development and conflict in two communities revealed the imperatives needed to strike a balance between conflict and sustainable development. While conflicts over natural resources are neither a new phenomenon nor are they inevitable, it is the approaches adopted to manage them that generate interests and makes a difference between peace and violence. Thus, conflicts associated with wilderness or TFCA development initiatives such as the Great Limpopo Transfrontier Park (GLTP) have attracted significant interest from various stakeholders. While the GLTP is a flagship conservation initiative in Southern Africa designed to integrate different land uses for socio-economic development, it is littered with conflicts. Through documenting the experiences of two communities involved in development conflicts, a determination was sought to understand the efficacy of approaches used to manage the conflict. Using mainly questionnaires and personal interviews, perceptions and attitudes of key informants were solicited. Unresolved historical problems reincarnated to haunt current conservation projects as memories of unresolved past events reflected negatively on new related initiatives. Different approaches adopted in managing these conflicts resulted in significantly different outcomes. Local stakeholder involvements were inadequate, but were identified as pertinent to successful sustainable conservation and development. Unless local communities are assured of real benefits from new conservation initiatives it became evident that recurrent conflicts would be inevitable. The findings reveal that current conservation initiatives should be underpinned by emerging inclusivity theories in the conservation discourse. A broad range of stakeholders should embrace this new paradigm based on the philosophy that conservation efforts that exclude local communities are bound to be unsustainable. We found out that it is in the interests of all for policy makers to come up with policies that recognise the critical role local communities play, while subscribing to the regional and international standards for best practices in the conservation business.
- Full Text:
- Date Issued: 2011
Core self-evaluations, racial evaluation and learning amongst Zulu students at the university of Zululand
- Authors: Dodd Nicole Marguerite
- Date: 2011
- Subjects: Zulu (African people) -- Ethnic identity , Self-evaluation , Ethnicity
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9879 , http://hdl.handle.net/10948/d1008398 , Zulu (African people) -- Ethnic identity , Self-evaluation , Ethnicity
- Description: Core Self-Evaluations [CSE] are a person’s estimation of his/her own worth and ability (Judge & Scott 2009). This in turn, is related to Racial Evaluation which is a person’s internal evaluation of his/her racial identity (Diller, 2010). The Employment Equity Act (55 of 1998) makes provision for the employment of equity candidates who can acquire skills in a reasonable amount of time. This requires individuals to be able to learn and then achieve in outcomes-based assessment. Core Self-Evaluations and Racial Evaluation can have an impact on how individuals perceive themselves, and how they perform in education, training and development (Hanley & Noblit, 2009). This study explored the relationship between Core Self-Evaluation, Racial Evaluation, Learning and Outcomes-Based Assessment using an experimental design. The Core Self-Evaluation scores in this study (n=230) were consistent with levels found internationally (Broucek, 2005). There was positive Racial Evaluation, with a relationship existing between Racial Evaluation and Core Self-Evaluations. This means that part of a person’s identity as an individual is related to Racial Evaluation, with that Racial Evaluation being positive amongst young Zulu students at the University of Zululand. There was a statistically significant, but small correlation between Learning and Core Self- Evaluation and a relationship was also found between CSE and Outcomes-Based Assessment results. When Core Self-Evaluation is higher, Learning tends to be more likely. The same pattern does not hold for Outcomes-Based Assessment results. Among Zulu students, lower CSE is linked to improved Outcomes-Based Assessment results. Racial Evaluation has a small relationship with CSE. However, efforts to remedy apartheid may be directed towards socio-economic development and need not focus on boosting Racial Evaluation when it comes to young Zulu adults.
- Full Text:
- Date Issued: 2011
- Authors: Dodd Nicole Marguerite
- Date: 2011
- Subjects: Zulu (African people) -- Ethnic identity , Self-evaluation , Ethnicity
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9879 , http://hdl.handle.net/10948/d1008398 , Zulu (African people) -- Ethnic identity , Self-evaluation , Ethnicity
- Description: Core Self-Evaluations [CSE] are a person’s estimation of his/her own worth and ability (Judge & Scott 2009). This in turn, is related to Racial Evaluation which is a person’s internal evaluation of his/her racial identity (Diller, 2010). The Employment Equity Act (55 of 1998) makes provision for the employment of equity candidates who can acquire skills in a reasonable amount of time. This requires individuals to be able to learn and then achieve in outcomes-based assessment. Core Self-Evaluations and Racial Evaluation can have an impact on how individuals perceive themselves, and how they perform in education, training and development (Hanley & Noblit, 2009). This study explored the relationship between Core Self-Evaluation, Racial Evaluation, Learning and Outcomes-Based Assessment using an experimental design. The Core Self-Evaluation scores in this study (n=230) were consistent with levels found internationally (Broucek, 2005). There was positive Racial Evaluation, with a relationship existing between Racial Evaluation and Core Self-Evaluations. This means that part of a person’s identity as an individual is related to Racial Evaluation, with that Racial Evaluation being positive amongst young Zulu students at the University of Zululand. There was a statistically significant, but small correlation between Learning and Core Self- Evaluation and a relationship was also found between CSE and Outcomes-Based Assessment results. When Core Self-Evaluation is higher, Learning tends to be more likely. The same pattern does not hold for Outcomes-Based Assessment results. Among Zulu students, lower CSE is linked to improved Outcomes-Based Assessment results. Racial Evaluation has a small relationship with CSE. However, efforts to remedy apartheid may be directed towards socio-economic development and need not focus on boosting Racial Evaluation when it comes to young Zulu adults.
- Full Text:
- Date Issued: 2011
Crime, violence and apartheid in selected works of Richard Wright and Athol Fugard: a study
- Authors: Makombe, Rodwell
- Date: 2011
- Subjects: Apartheid in literature , Politics and literature -- South Africa , Race discrimination -- South Africa , Crime -- South Africa , Violence -- South Africa
- Language: English
- Type: Thesis , Doctoral , DLitt et Phil (English)
- Identifier: vital:11888 , http://hdl.handle.net/10353/525 , Apartheid in literature , Politics and literature -- South Africa , Race discrimination -- South Africa , Crime -- South Africa , Violence -- South Africa
- Description: Different forms of racial segregation have been practiced in different countries the world over. However, the nature of South Africa‟s apartheid system, as it was practiced from 1948 until the dawn of the democratic dispensation in 1994, has been a subject of debate in South Africa and even beyond. Apartheid was a policy that was designed by the then ruling Nationalist Party for purposes of dividing and stratifying South Africa along racial lines - whites, blacks, coloureds and Asians. It thus promoted racial segregation and/or unequal stratification of society. In South Africa‟s hierarchy of apartheid, blacks, who constituted the majority of the population, were ironically the most destitute and segregated. Some historians believe that South Africa‟s racial policy was designed against the backdrop of Jim Crow, a similar system of racial discrimination which was instituted in the American South late in the 1890s through the 20th century. Jim Crow and apartheid are, in this study, considered as sides of the same coin; hence for the sake of convenience, the word apartheid is used to subsume Jim Crow. Although South Africa‟s apartheid system was influenced by different ideologies, for example German missiology as applied by the Dutch Reformed Church, historian Hermann Giliomee (2003: 373) insists that „the segregationist practice of the American South was particularly influential.‟ Given the ideological relationship between apartheid and Jim Crow, the present study investigates the interplay of compatibility between apartheid/Jim Crow and crime and violence as reflected in selected works of Richard Wright (African American novelist) and Athol Fugard (South African playwright). The aim of the study is firstly, to examine the works in order to analyse them as responses to apartheid and by extension colonial domination and secondly to investigate crime and violence. The three criminological theories selected for this study are strain theory (by Robert Merton), subculture theory (Edwin Sutherland) and labelling theory (Howard Becker). While criminological theory provides an empirical dimension to the study, postcolonial theory situates the study within a specified space, which is the postcolonial context. The postcolonial is, however understood, not as a demarcated historical space, but as a continuum, from the dawn of colonization to the unforeseeable future. Three postcolonial theorists have been identified for the purposes of this study. These are: Frantz Fanon, Homi Bhabha and Bill Ashcroft. Fanon‟s psychoanalysis of the colonized, Homi Bhabha‟s Third Space and hybridity as well as Ashcroft‟s postcolonial transformation are key concepts in understanding the different ways in which the colonized deal with the consequences of colonization. It has been suggested particularly in Edward Said‟s Orientalism (1978) that the discourse of orientalism creates the Oriental, as if Orientals were a passive object of the colonial adventure. This study uses Bhabha‟s and Ashcroft‟s theory of colonial discourse to argue that the colonized are not only objects of the colonial enterprise but also active participants in the process of opening survival spaces for self-realization. The various criminal activities that the colonized engage in (as represented in the selected works of Richard Wright and Athol Fugard) are in this study viewed as ways of inscribing their subjectivity within an exclusive colonial system.
- Full Text:
- Date Issued: 2011
- Authors: Makombe, Rodwell
- Date: 2011
- Subjects: Apartheid in literature , Politics and literature -- South Africa , Race discrimination -- South Africa , Crime -- South Africa , Violence -- South Africa
- Language: English
- Type: Thesis , Doctoral , DLitt et Phil (English)
- Identifier: vital:11888 , http://hdl.handle.net/10353/525 , Apartheid in literature , Politics and literature -- South Africa , Race discrimination -- South Africa , Crime -- South Africa , Violence -- South Africa
- Description: Different forms of racial segregation have been practiced in different countries the world over. However, the nature of South Africa‟s apartheid system, as it was practiced from 1948 until the dawn of the democratic dispensation in 1994, has been a subject of debate in South Africa and even beyond. Apartheid was a policy that was designed by the then ruling Nationalist Party for purposes of dividing and stratifying South Africa along racial lines - whites, blacks, coloureds and Asians. It thus promoted racial segregation and/or unequal stratification of society. In South Africa‟s hierarchy of apartheid, blacks, who constituted the majority of the population, were ironically the most destitute and segregated. Some historians believe that South Africa‟s racial policy was designed against the backdrop of Jim Crow, a similar system of racial discrimination which was instituted in the American South late in the 1890s through the 20th century. Jim Crow and apartheid are, in this study, considered as sides of the same coin; hence for the sake of convenience, the word apartheid is used to subsume Jim Crow. Although South Africa‟s apartheid system was influenced by different ideologies, for example German missiology as applied by the Dutch Reformed Church, historian Hermann Giliomee (2003: 373) insists that „the segregationist practice of the American South was particularly influential.‟ Given the ideological relationship between apartheid and Jim Crow, the present study investigates the interplay of compatibility between apartheid/Jim Crow and crime and violence as reflected in selected works of Richard Wright (African American novelist) and Athol Fugard (South African playwright). The aim of the study is firstly, to examine the works in order to analyse them as responses to apartheid and by extension colonial domination and secondly to investigate crime and violence. The three criminological theories selected for this study are strain theory (by Robert Merton), subculture theory (Edwin Sutherland) and labelling theory (Howard Becker). While criminological theory provides an empirical dimension to the study, postcolonial theory situates the study within a specified space, which is the postcolonial context. The postcolonial is, however understood, not as a demarcated historical space, but as a continuum, from the dawn of colonization to the unforeseeable future. Three postcolonial theorists have been identified for the purposes of this study. These are: Frantz Fanon, Homi Bhabha and Bill Ashcroft. Fanon‟s psychoanalysis of the colonized, Homi Bhabha‟s Third Space and hybridity as well as Ashcroft‟s postcolonial transformation are key concepts in understanding the different ways in which the colonized deal with the consequences of colonization. It has been suggested particularly in Edward Said‟s Orientalism (1978) that the discourse of orientalism creates the Oriental, as if Orientals were a passive object of the colonial adventure. This study uses Bhabha‟s and Ashcroft‟s theory of colonial discourse to argue that the colonized are not only objects of the colonial enterprise but also active participants in the process of opening survival spaces for self-realization. The various criminal activities that the colonized engage in (as represented in the selected works of Richard Wright and Athol Fugard) are in this study viewed as ways of inscribing their subjectivity within an exclusive colonial system.
- Full Text:
- Date Issued: 2011
Desegregation and socio-spatial integration in residential suburbs in East London, South Africa (1993-2008)
- Authors: Bwalya, John
- Date: 2011
- Subjects: City planning -- South Africa -- East London , Apartheid -- South Africa -- Eastern Cape , Migration, Internal -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Geography)
- Identifier: vital:11504 , http://hdl.handle.net/10353/336 , City planning -- South Africa -- East London , Apartheid -- South Africa -- Eastern Cape , Migration, Internal -- South Africa -- Eastern Cape
- Description: This study used integration as the overarching conceptual framework to investigate socio-spatial integration in post-apartheid South Africa. The study adopted the embedded case study design to investigate the spatial and social aspects of integration in former white residential suburbs in East London, South Africa. Recognising that integration occurred in different registers, this study used data from the South African Property Transfer Guide (SAPTG) database to investigate spatial-temporal integration in East London‟s residential suburbs from 1993 to 2008. A total of 21,683 residential property transfers were reviewed in 46 suburbs, and transfers to Blacks were identified. The residential property transfers were mapped to identify the nature of spatial integration. To investigate social integration, in-depth personal interviews were conducted on a purposively drawn sample of residents in the three case study suburbs of Southernwood, Cambridge and Gonubie. The interviews focused on three proxy indicators of social capital at neighbourhood level. The results of the study showed that post-apartheid spatial integration in East London closely followed the class-based residential template. Contrary to predictions prior to, and following apartheid‟s demise, the study showed that spatial integration occurred without racial conflicts. The study also found that social integration in the residential suburbs reflected the neighbourhood context and personal preferences, and was highly fluid. Although feelings of racial distance were evident, there were also indications of social cohesion, which were dynamic and uneven in time and space. Based on the data and the dialectical nature of spatial and social integration, the study concluded that fragmentation and integration are likely to continue coexisting in the South African city.
- Full Text:
- Date Issued: 2011
- Authors: Bwalya, John
- Date: 2011
- Subjects: City planning -- South Africa -- East London , Apartheid -- South Africa -- Eastern Cape , Migration, Internal -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Geography)
- Identifier: vital:11504 , http://hdl.handle.net/10353/336 , City planning -- South Africa -- East London , Apartheid -- South Africa -- Eastern Cape , Migration, Internal -- South Africa -- Eastern Cape
- Description: This study used integration as the overarching conceptual framework to investigate socio-spatial integration in post-apartheid South Africa. The study adopted the embedded case study design to investigate the spatial and social aspects of integration in former white residential suburbs in East London, South Africa. Recognising that integration occurred in different registers, this study used data from the South African Property Transfer Guide (SAPTG) database to investigate spatial-temporal integration in East London‟s residential suburbs from 1993 to 2008. A total of 21,683 residential property transfers were reviewed in 46 suburbs, and transfers to Blacks were identified. The residential property transfers were mapped to identify the nature of spatial integration. To investigate social integration, in-depth personal interviews were conducted on a purposively drawn sample of residents in the three case study suburbs of Southernwood, Cambridge and Gonubie. The interviews focused on three proxy indicators of social capital at neighbourhood level. The results of the study showed that post-apartheid spatial integration in East London closely followed the class-based residential template. Contrary to predictions prior to, and following apartheid‟s demise, the study showed that spatial integration occurred without racial conflicts. The study also found that social integration in the residential suburbs reflected the neighbourhood context and personal preferences, and was highly fluid. Although feelings of racial distance were evident, there were also indications of social cohesion, which were dynamic and uneven in time and space. Based on the data and the dialectical nature of spatial and social integration, the study concluded that fragmentation and integration are likely to continue coexisting in the South African city.
- Full Text:
- Date Issued: 2011
Development and testing of liposome encapsulated cyclic dipeptides
- Authors: Kilian, Gareth
- Date: 2011
- Subjects: Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10136 , http://hdl.handle.net/10948/1397 , Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Description: Cyclic dipeptides have been well characterized for their multitude of biological activities, including antimicrobial and anticancer activities. Cyclo(His-Gly) and cyclo(His-Ala) have also recently been shown to possess significant anticancer activity against a range of cell lines, despite the limitations of these two molecules with respect to their physicochemical properties. Low Log P results in poor cell permeability which can often be problematic for drugs with intracellular mechanisms of action. It can also results in poor biodistribution, and theoretical Log P values for cyclo(His-Gly) and cyclo(His-Ala) were extremely low making them ideal candidates for inclusion into a nanoparticulate drug delivery system. The aim of this study was therefore to formulate and evaluate liposome-encapsulated cyclic dipeptides that increase the tumour-suppressive actions of the cyclic dipeptides, while showing a high degree of specificity for tumour cells. While liposomes are relatively simple to prepare, inter batch variation, low encapsulation and poor stability are often problematic in their production and this has lead to very few liposomal products on the market. This study aimed at using a comprehensive statistical methodology in optimizing liposome formulations encapsulating cyclo(His-Gly) and cyclo(His-Ala). Initial screening of potential factors was conducted using a 25-1 fractional factorial design. This design made use of two levels for each of the five factors and abbreviated the design to minimize runs. Although not much information is provided by these types of designs, the design was sufficient in identifying two critical factors that would be studies further in a more robust design. The two factors selected, based on the screening study, were cholesterol and stearylamine content. These two factors were then used in designing a response surface methodology (RSM) design making use of a central composite rotatable vii design (CCRD) at five levels (-1.5, -1, 0, 1, 1.5) for each factor in order to better understand the design space. Various factors influenced the measured responses of encapsulation efficiency, zeta potential, polydispersity index, cellular uptake and leakage, but most notable were the adverse effects of increasing stearylamine levels on encapsulations efficiency and cholesterol levels on leakage for both cyclo(His-Gly) and cyclo(His-Ala) liposomes. Optimized formulations were derived from the data and prepared. Fair correlation between the predicted and measured responses was obtained. The cytotoxic activity of the encapsulated cyclic dipeptides were assessed against HeLa and MCF-7 cells and found to have limited improvement in activity. However, modification of the polyethylene glycol (PEG) grafted to the liposome surface in order to target folate receptors showed good benefit in significantly decreasing the IC50 values recorded in all cells lines tested, particularly low folate HeLa cells with the lowest IC50 being recorded as 0.0962 mM for folate targeted cyclo(His-Ala). The results therefore indicate that hydrophilic cyclic dipeptides are ideal candidates for inclusion into targeted drug delivery systems such as liposomes. Key words: Liposomes, cyclo(His-Gly), cyclo(His-Ala), cyclic dipeptides, HeLa, MCF-7, folate receptors, factorial design, response surface methodology (RSM), central composite rotatable design (CCRD).
- Full Text:
- Date Issued: 2011
- Authors: Kilian, Gareth
- Date: 2011
- Subjects: Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10136 , http://hdl.handle.net/10948/1397 , Peptide antibiotics , Peptide drugs -- Therapeutic use , Peptides -- Synthesis , Antibacterial agents -- Therapeutic use -- Testing , Cyclic peptides , Liposomes
- Description: Cyclic dipeptides have been well characterized for their multitude of biological activities, including antimicrobial and anticancer activities. Cyclo(His-Gly) and cyclo(His-Ala) have also recently been shown to possess significant anticancer activity against a range of cell lines, despite the limitations of these two molecules with respect to their physicochemical properties. Low Log P results in poor cell permeability which can often be problematic for drugs with intracellular mechanisms of action. It can also results in poor biodistribution, and theoretical Log P values for cyclo(His-Gly) and cyclo(His-Ala) were extremely low making them ideal candidates for inclusion into a nanoparticulate drug delivery system. The aim of this study was therefore to formulate and evaluate liposome-encapsulated cyclic dipeptides that increase the tumour-suppressive actions of the cyclic dipeptides, while showing a high degree of specificity for tumour cells. While liposomes are relatively simple to prepare, inter batch variation, low encapsulation and poor stability are often problematic in their production and this has lead to very few liposomal products on the market. This study aimed at using a comprehensive statistical methodology in optimizing liposome formulations encapsulating cyclo(His-Gly) and cyclo(His-Ala). Initial screening of potential factors was conducted using a 25-1 fractional factorial design. This design made use of two levels for each of the five factors and abbreviated the design to minimize runs. Although not much information is provided by these types of designs, the design was sufficient in identifying two critical factors that would be studies further in a more robust design. The two factors selected, based on the screening study, were cholesterol and stearylamine content. These two factors were then used in designing a response surface methodology (RSM) design making use of a central composite rotatable vii design (CCRD) at five levels (-1.5, -1, 0, 1, 1.5) for each factor in order to better understand the design space. Various factors influenced the measured responses of encapsulation efficiency, zeta potential, polydispersity index, cellular uptake and leakage, but most notable were the adverse effects of increasing stearylamine levels on encapsulations efficiency and cholesterol levels on leakage for both cyclo(His-Gly) and cyclo(His-Ala) liposomes. Optimized formulations were derived from the data and prepared. Fair correlation between the predicted and measured responses was obtained. The cytotoxic activity of the encapsulated cyclic dipeptides were assessed against HeLa and MCF-7 cells and found to have limited improvement in activity. However, modification of the polyethylene glycol (PEG) grafted to the liposome surface in order to target folate receptors showed good benefit in significantly decreasing the IC50 values recorded in all cells lines tested, particularly low folate HeLa cells with the lowest IC50 being recorded as 0.0962 mM for folate targeted cyclo(His-Ala). The results therefore indicate that hydrophilic cyclic dipeptides are ideal candidates for inclusion into targeted drug delivery systems such as liposomes. Key words: Liposomes, cyclo(His-Gly), cyclo(His-Ala), cyclic dipeptides, HeLa, MCF-7, folate receptors, factorial design, response surface methodology (RSM), central composite rotatable design (CCRD).
- Full Text:
- Date Issued: 2011
Development of MgZnO-grown MOCVD for UV Photonic applications
- Authors: Talla, Kharouna
- Date: 2011
- Subjects: Photoluminescence , Photonics , Zinc oxide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10537 , http://hdl.handle.net/10948/d1012585 , Photoluminescence , Photonics , Zinc oxide
- Description: MgxZn1-xO has emerged as a material of great technological importance. Having a direct energy band gap that is tunable throughout much of the ultraviolet (UV) region of the spectrum from the near-UV (~370 nm) to the deep-UV (~176 nm), this compound is of interest for a variety of optoelectronic devices operating in this part of the electromagnetic spectrum. MgxZn1-xO offers advantages over the more mature compound semiconductor AlGaN which stem mainly from the unusually high exciton binding energy (60 meV in ZnO). In this study the growth of ZnO and MgxZn1-xO thin films using metal organic chemical vapour deposition (MOCVD) is systematically investigated. The films are mainly grown on c-Al2O3 and Si (100) and characterized using various techniques, such as photoluminescence (PL), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The optical and the structural properties are essentially inspected in order to improve their quality. In this thesis the optimisation of ZnO grown using oxygen gas as a new oxidant in our reactor is investigated. The growth temperature and VI/II ratio are varied in order to find optimum parameters giving high quality layers. The effects of Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO substrates on the optical, structural and morphological properties of ZnO thin films grown with tert-butanol (TBOH) is examined. Similar morphologies are observed for all substrates, with the films comprising hexagonal columns having cone shaped ends. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra. The morphology changes with Mg incorporation, from hexagonal columnar structures to cubic faceted columns. From PL, the full with at half maximum is found to gradually increase with Mg content due to alloy broadening. The deep level emission (DLE) is observed to shift with Mg content. By changing the Mg content, the band gap of MgxZn1-xO film is tuned by ~450 meV, which provides an excellent opportunity for band gap engineering for optoelectronic applications. The c-lattice constant of ZnO (5.205 Å) decreases by only 0.6% when the Mg content reaches x=0.39. The introduction of Mg into ZnO is shown to increase the relative PL intensity of stacking fault-related transitions (at 3.314 eV for ZnO). This becomes the dominant near band edge emission. Using TEM a thin Mg rich layer is observed at the interface between the film and the Si or Al2O3. Temperature dependent PL measurements on layers with low Mg concentration (x=0.05 and 0.1) show that the main bound exciton peak exhibits an “s-shaped” temperature dependence, characteristic of localization in a disordered alloy. The origin of the PL line broadening of MgxZn1-xO (x≤0.04) is also analyzed with respect to alloy broadening, taking into account a random cation distribution and alloy clustering. The influence of various MOCVD growth parameters such as growth temperature and VI/II ratio is studied. Varying the temperature from 280 ˚C to 580 ˚C reveals strong morphological changes and optical degradation of the films. Low (<280 ˚C) and high (>580 ˚C) growth temperatures reduce the Mg incorporation. High VI/II ratios also decrease the Mg incorporation, as evidenced by the red-shift of the donor bound exciton (D°X) line. This is ascribed to a stronger premature reaction between (MeCp)2Mg and the oxidant or a preferential heterogeneous interaction between the Mg and oxygen species on the growth front. For both oxidizing agents (O2 and TBOH), the growth at 420 ˚C and a VI-II ratio of 60 on c-Al2O3 gave optimal quality layers in terms of their optical and structural quality. A comparison of films grown using TBOH and O2 gas as oxidizing agent shows no major difference in terms of Mg incorporation. The effect of annealing, the inclusion of a buffer layer and the influence of growth rate on the properties MgxZn1-xO thin films are also reported.
- Full Text:
- Date Issued: 2011
- Authors: Talla, Kharouna
- Date: 2011
- Subjects: Photoluminescence , Photonics , Zinc oxide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10537 , http://hdl.handle.net/10948/d1012585 , Photoluminescence , Photonics , Zinc oxide
- Description: MgxZn1-xO has emerged as a material of great technological importance. Having a direct energy band gap that is tunable throughout much of the ultraviolet (UV) region of the spectrum from the near-UV (~370 nm) to the deep-UV (~176 nm), this compound is of interest for a variety of optoelectronic devices operating in this part of the electromagnetic spectrum. MgxZn1-xO offers advantages over the more mature compound semiconductor AlGaN which stem mainly from the unusually high exciton binding energy (60 meV in ZnO). In this study the growth of ZnO and MgxZn1-xO thin films using metal organic chemical vapour deposition (MOCVD) is systematically investigated. The films are mainly grown on c-Al2O3 and Si (100) and characterized using various techniques, such as photoluminescence (PL), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The optical and the structural properties are essentially inspected in order to improve their quality. In this thesis the optimisation of ZnO grown using oxygen gas as a new oxidant in our reactor is investigated. The growth temperature and VI/II ratio are varied in order to find optimum parameters giving high quality layers. The effects of Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO substrates on the optical, structural and morphological properties of ZnO thin films grown with tert-butanol (TBOH) is examined. Similar morphologies are observed for all substrates, with the films comprising hexagonal columns having cone shaped ends. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra. The morphology changes with Mg incorporation, from hexagonal columnar structures to cubic faceted columns. From PL, the full with at half maximum is found to gradually increase with Mg content due to alloy broadening. The deep level emission (DLE) is observed to shift with Mg content. By changing the Mg content, the band gap of MgxZn1-xO film is tuned by ~450 meV, which provides an excellent opportunity for band gap engineering for optoelectronic applications. The c-lattice constant of ZnO (5.205 Å) decreases by only 0.6% when the Mg content reaches x=0.39. The introduction of Mg into ZnO is shown to increase the relative PL intensity of stacking fault-related transitions (at 3.314 eV for ZnO). This becomes the dominant near band edge emission. Using TEM a thin Mg rich layer is observed at the interface between the film and the Si or Al2O3. Temperature dependent PL measurements on layers with low Mg concentration (x=0.05 and 0.1) show that the main bound exciton peak exhibits an “s-shaped” temperature dependence, characteristic of localization in a disordered alloy. The origin of the PL line broadening of MgxZn1-xO (x≤0.04) is also analyzed with respect to alloy broadening, taking into account a random cation distribution and alloy clustering. The influence of various MOCVD growth parameters such as growth temperature and VI/II ratio is studied. Varying the temperature from 280 ˚C to 580 ˚C reveals strong morphological changes and optical degradation of the films. Low (<280 ˚C) and high (>580 ˚C) growth temperatures reduce the Mg incorporation. High VI/II ratios also decrease the Mg incorporation, as evidenced by the red-shift of the donor bound exciton (D°X) line. This is ascribed to a stronger premature reaction between (MeCp)2Mg and the oxidant or a preferential heterogeneous interaction between the Mg and oxygen species on the growth front. For both oxidizing agents (O2 and TBOH), the growth at 420 ˚C and a VI-II ratio of 60 on c-Al2O3 gave optimal quality layers in terms of their optical and structural quality. A comparison of films grown using TBOH and O2 gas as oxidizing agent shows no major difference in terms of Mg incorporation. The effect of annealing, the inclusion of a buffer layer and the influence of growth rate on the properties MgxZn1-xO thin films are also reported.
- Full Text:
- Date Issued: 2011
Differential expression and regulation of sucrose transporters in rice (Orzya sativa L, cv Nipponbare) during environmental stress conditions
- Authors: Ibraheem, Omodele
- Date: 2011
- Subjects: Crops -- Effect of stress on , Plant molecular genetics , Gene expression , Sucrose , Rice
- Language: English
- Type: Thesis , Doctoral , PhD (Biochemistry)
- Identifier: vital:11249 , http://hdl.handle.net/10353/330 , Crops -- Effect of stress on , Plant molecular genetics , Gene expression , Sucrose , Rice
- Description: Plant productivity is greatly affected by environmental stresses such as drought, salinity and insect herbivory. Plants respond and adapt to these stresses by exhibiting physiological as well as biochemical changes at the cellular and molecular levels in order to survive. Expression of a variety of genes which encode numerous membrane transporters have been demonstrated to be induced by these stresses in a variety of plants. The nutritional status of plants is controlled by these transporters, which are regulated by the transcription of the corresponding genes. In spite of these adverse stress effects on agricultural yield, only a few studies have focused on gene transcriptional and translational regulation of membrane transporters during environmental stress situations. Rice, like other plants, contains a number of sucrose transporters encoded by a family of genes. However, detailed knowledge of their roles, localization and regulation during environmental stress conditions is lacking. Bioinformatic tools were used to identify putative cis-acting regulatory elements that may be involved in the regulation of rice and Arabidopsis thaliana sucrose transporters. The possible cis-acting regulatory elements were predicted by scanning genomic sequences 1.5 kbp upstream of the sucrose transporter genes translational start sites, using Plant CARE, PLACE and Genomatix Matinspector professional data bases. Several cis-acting regulatory elements that are associated with plant development, plant hormonal regulation and stress response were identified, and were present in varying frequencies within the 1.5 kbp of 5′ regulatory region. The putative cis-acting regulatory elements that possibly are involved in the expression and regulation of sucrose transporter gene families in rice and Arabidopsis thaliana during cellular development or environmental stress conditions were identified as: A-box, RY, CAT, Pyrimidine-box, Sucrose-box, ABRE, ARF, ERE, GARE, Me-JA, ARE, DRE, GA-motif, GATA, GT-1, MYC, MYB, W-box, and I-box. Expression analysis was used to elucidate the role of rice (Oryza sativa L. cv Nipponbare) sucrose transporter (OsSUT) genes during drought and salinity treatments of three week old rice plants ( at four leaf stage) over a 10 days. Among the five rice OsSUT genes identified, only OsSUT2 was observed to be progressively up-regulated during drought and salinity treatments, while OsSUT1, OsSUT4 and OsSUT5 were expressed at low levels, and OsSUT3 showed no detectable transcript expression. Sucrose transport will be essential to meet the cellular energy demands and also for osmoprotectant activities during drought and salinity stresses. It therefore indicates that OsSUT2 which facilitates transport of sucrose from photosynthetic cells will be III essential for rice plants to cope with drought and salinity stresses, and cultivars with a higher OsSUT2 expression should be able to tolerate these environmental stresses better. The role of OsSUT in assimilate transport during rusty plum aphids (Hysteroneura setariae; Thomas) infestation on the leaves of three week old rice (Orzya sativa L. cv Nipponbare) cultivar plants, over a time-course of 1 to 10 days of treatments, was also examined by combination of gene expression and β-glucuronidase (GUS) reporter gene analysis. Real Time PCR analysis of the five OsSUT genes revealed that the expression of OsSUT1 was progressively up-regulated during the course of aphid infestation. OsSUT2 and OsSUT4 expression were comparatively low in both the control and treated plants. OsSUT5 showed no clear difference in transcript expression in both control and treated plants, while no detectable transcript expression of OsSUT3 could be found. The up-regulation of OsSUT1 gene was verified at protein level by western blot analysis in both the control and treated plants. OsSUT1 protein expression was found to increase with time during aphid infestation. A similar trend was noticeable in the control plants, however at a lower expression level. These demonstrate that the cellular expression of OsSUT1is regulated by both developmental and environmental factors. OsSUT1-promoter:::GUS reporter gene expression was observed within the vascular parenchyma and/or companion cells associated with phloem sieve elements of the large and small bundles in the phloem tissues of the flag leaf blade regions where feeding aphids were confined, which progressively increased with time of infestation. It is suggested that OsSUT1 may primarily play an essential role in phloem transport of assimilate to wounded tissues from adjacent health tissues or may be involved in the retrieval of assimilate back into the phloem to minimize loss caused by the infestation. Some OsSUT1-promoter:::GUS expression was also found in the metaxylem at 10 days after infestation, which could signify a recovery system in which sucrose lost into the xylem as a result of aphids feeding are retrieved back into the phloem through the vascular parenchyma. This was supported by the exposure of cut ends of matured OsSUT1-promoter:::GUS rice plant leaf to 2% sucrose solution. OsSUT1-promoter:::GUS expression was observed within the protoxylem, xylem and phloem parenchyma tissues. This indicates that sucrose translocating within the xylem tissues are retrieved into the phloem via the OsSUT1 localized within the parenchyma tissues. In conclusion, the differential expression and regulation of rice (Orzya sativa L. cv Nipponbare) sucrose transporters as reported here suggest that OsSUT2 and OsSUT1 were constitutively expressed compared to other rice sucrose transporters during drought and salinity, and rusty plum aphids (Hysteroneura setariae; Thomas) infestation stresses respectively. Thus, the expression and regulation of the sucrose transporters could be related to the physiological and nutritional requirements of the cells during plant developmental or environmental stress state that allows their differential expression.
- Full Text:
- Date Issued: 2011
- Authors: Ibraheem, Omodele
- Date: 2011
- Subjects: Crops -- Effect of stress on , Plant molecular genetics , Gene expression , Sucrose , Rice
- Language: English
- Type: Thesis , Doctoral , PhD (Biochemistry)
- Identifier: vital:11249 , http://hdl.handle.net/10353/330 , Crops -- Effect of stress on , Plant molecular genetics , Gene expression , Sucrose , Rice
- Description: Plant productivity is greatly affected by environmental stresses such as drought, salinity and insect herbivory. Plants respond and adapt to these stresses by exhibiting physiological as well as biochemical changes at the cellular and molecular levels in order to survive. Expression of a variety of genes which encode numerous membrane transporters have been demonstrated to be induced by these stresses in a variety of plants. The nutritional status of plants is controlled by these transporters, which are regulated by the transcription of the corresponding genes. In spite of these adverse stress effects on agricultural yield, only a few studies have focused on gene transcriptional and translational regulation of membrane transporters during environmental stress situations. Rice, like other plants, contains a number of sucrose transporters encoded by a family of genes. However, detailed knowledge of their roles, localization and regulation during environmental stress conditions is lacking. Bioinformatic tools were used to identify putative cis-acting regulatory elements that may be involved in the regulation of rice and Arabidopsis thaliana sucrose transporters. The possible cis-acting regulatory elements were predicted by scanning genomic sequences 1.5 kbp upstream of the sucrose transporter genes translational start sites, using Plant CARE, PLACE and Genomatix Matinspector professional data bases. Several cis-acting regulatory elements that are associated with plant development, plant hormonal regulation and stress response were identified, and were present in varying frequencies within the 1.5 kbp of 5′ regulatory region. The putative cis-acting regulatory elements that possibly are involved in the expression and regulation of sucrose transporter gene families in rice and Arabidopsis thaliana during cellular development or environmental stress conditions were identified as: A-box, RY, CAT, Pyrimidine-box, Sucrose-box, ABRE, ARF, ERE, GARE, Me-JA, ARE, DRE, GA-motif, GATA, GT-1, MYC, MYB, W-box, and I-box. Expression analysis was used to elucidate the role of rice (Oryza sativa L. cv Nipponbare) sucrose transporter (OsSUT) genes during drought and salinity treatments of three week old rice plants ( at four leaf stage) over a 10 days. Among the five rice OsSUT genes identified, only OsSUT2 was observed to be progressively up-regulated during drought and salinity treatments, while OsSUT1, OsSUT4 and OsSUT5 were expressed at low levels, and OsSUT3 showed no detectable transcript expression. Sucrose transport will be essential to meet the cellular energy demands and also for osmoprotectant activities during drought and salinity stresses. It therefore indicates that OsSUT2 which facilitates transport of sucrose from photosynthetic cells will be III essential for rice plants to cope with drought and salinity stresses, and cultivars with a higher OsSUT2 expression should be able to tolerate these environmental stresses better. The role of OsSUT in assimilate transport during rusty plum aphids (Hysteroneura setariae; Thomas) infestation on the leaves of three week old rice (Orzya sativa L. cv Nipponbare) cultivar plants, over a time-course of 1 to 10 days of treatments, was also examined by combination of gene expression and β-glucuronidase (GUS) reporter gene analysis. Real Time PCR analysis of the five OsSUT genes revealed that the expression of OsSUT1 was progressively up-regulated during the course of aphid infestation. OsSUT2 and OsSUT4 expression were comparatively low in both the control and treated plants. OsSUT5 showed no clear difference in transcript expression in both control and treated plants, while no detectable transcript expression of OsSUT3 could be found. The up-regulation of OsSUT1 gene was verified at protein level by western blot analysis in both the control and treated plants. OsSUT1 protein expression was found to increase with time during aphid infestation. A similar trend was noticeable in the control plants, however at a lower expression level. These demonstrate that the cellular expression of OsSUT1is regulated by both developmental and environmental factors. OsSUT1-promoter:::GUS reporter gene expression was observed within the vascular parenchyma and/or companion cells associated with phloem sieve elements of the large and small bundles in the phloem tissues of the flag leaf blade regions where feeding aphids were confined, which progressively increased with time of infestation. It is suggested that OsSUT1 may primarily play an essential role in phloem transport of assimilate to wounded tissues from adjacent health tissues or may be involved in the retrieval of assimilate back into the phloem to minimize loss caused by the infestation. Some OsSUT1-promoter:::GUS expression was also found in the metaxylem at 10 days after infestation, which could signify a recovery system in which sucrose lost into the xylem as a result of aphids feeding are retrieved back into the phloem through the vascular parenchyma. This was supported by the exposure of cut ends of matured OsSUT1-promoter:::GUS rice plant leaf to 2% sucrose solution. OsSUT1-promoter:::GUS expression was observed within the protoxylem, xylem and phloem parenchyma tissues. This indicates that sucrose translocating within the xylem tissues are retrieved into the phloem via the OsSUT1 localized within the parenchyma tissues. In conclusion, the differential expression and regulation of rice (Orzya sativa L. cv Nipponbare) sucrose transporters as reported here suggest that OsSUT2 and OsSUT1 were constitutively expressed compared to other rice sucrose transporters during drought and salinity, and rusty plum aphids (Hysteroneura setariae; Thomas) infestation stresses respectively. Thus, the expression and regulation of the sucrose transporters could be related to the physiological and nutritional requirements of the cells during plant developmental or environmental stress state that allows their differential expression.
- Full Text:
- Date Issued: 2011
Dryland conservation areas, indigenous people, livelihoods and natural resource values in South Africa: the case of Kgalagadi Transfrontier Park
- Authors: Thondhlana, Gladman
- Date: 2011
- Subjects: Human ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions biodiversity conservation -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions agriculture -- Kgalagadi Transfrontier Park (Botswana and South Africa) Indigenous peoples -- Ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources conservation areas -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Government policy -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Kgalagadi Transfrontier Park (Botswana and South Africa) -- Management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4777 , http://hdl.handle.net/10962/d1011732
- Description: Contemporary conservation and development understanding in both policy and academic circles espouses that natural resources have a significant contribution to the livelihoods of local people and that knowledge of this can better foster conservation policies that are consistent with livelihood and ecological needs. This thesis is based on research conducted in the southern Kalahari region, South Africa among the San and Mier communities bordering Kgalagadi Transfrontier Park. It looks at the importance of natural resources to the San and Mier community groups and ascertains the extent of resource use and its value within broader livelihood portfolios. It also focuses on the cultural values of natural resources and interactions among institutions and actors and how these shape natural resource governance and livelihood outcomes. Overall, natural resources represent an important livelihood source contributing up to 32 % and 9 % of the total income of the San and Mier respectively or up to 46 % and 23 % if livestock incomes are included. However, the dependence on, diversification patterns and distribution of natural resource income vary substantially between and within the two communities. With regards to the cultural values attached to natural resources by the San and Mier, the findings show that these arise from an incredibly diverse and sometimes conflicting array of values that punctuate the two communities’ way of life and they are inextricably linked to resource use. Lastly, governance of natural resources in the co-managed Park and communitymanaged resettlement farms is characterised by complex institutional arrangements, compounded by the existence of multiple actors that have multiple and sometimes conflicting objectives – as shaped by different meanings and interpretations of natural resources. Heightened inter- and intra-community conflicts are common, notably resource use conflicts between the San and Mier and between the San ‘modernist’ and ‘traditionalist’ groups. This demonstrates that the communities’ livelihood dynamics in general and the dependence on natural resources in particular, are closely linked with ecological, economic and social factors including history, culture and present livelihood needs. By exploring the social-environment interactions, the study highlights the complexities and diversity of resource use for livelihoods that should be taken into consideration for both conservation and development policy interventions and research. The main argument of the study is that the contribution of natural resources to local livelihood portfolios in co- and community-managed areas, can be better understood through a consideration of cultural dynamics and institutional arrangements since these condition natural resource access, value and use.
- Full Text:
- Date Issued: 2011
- Authors: Thondhlana, Gladman
- Date: 2011
- Subjects: Human ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions biodiversity conservation -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions agriculture -- Kgalagadi Transfrontier Park (Botswana and South Africa) Indigenous peoples -- Ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources conservation areas -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Government policy -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Kgalagadi Transfrontier Park (Botswana and South Africa) -- Management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4777 , http://hdl.handle.net/10962/d1011732
- Description: Contemporary conservation and development understanding in both policy and academic circles espouses that natural resources have a significant contribution to the livelihoods of local people and that knowledge of this can better foster conservation policies that are consistent with livelihood and ecological needs. This thesis is based on research conducted in the southern Kalahari region, South Africa among the San and Mier communities bordering Kgalagadi Transfrontier Park. It looks at the importance of natural resources to the San and Mier community groups and ascertains the extent of resource use and its value within broader livelihood portfolios. It also focuses on the cultural values of natural resources and interactions among institutions and actors and how these shape natural resource governance and livelihood outcomes. Overall, natural resources represent an important livelihood source contributing up to 32 % and 9 % of the total income of the San and Mier respectively or up to 46 % and 23 % if livestock incomes are included. However, the dependence on, diversification patterns and distribution of natural resource income vary substantially between and within the two communities. With regards to the cultural values attached to natural resources by the San and Mier, the findings show that these arise from an incredibly diverse and sometimes conflicting array of values that punctuate the two communities’ way of life and they are inextricably linked to resource use. Lastly, governance of natural resources in the co-managed Park and communitymanaged resettlement farms is characterised by complex institutional arrangements, compounded by the existence of multiple actors that have multiple and sometimes conflicting objectives – as shaped by different meanings and interpretations of natural resources. Heightened inter- and intra-community conflicts are common, notably resource use conflicts between the San and Mier and between the San ‘modernist’ and ‘traditionalist’ groups. This demonstrates that the communities’ livelihood dynamics in general and the dependence on natural resources in particular, are closely linked with ecological, economic and social factors including history, culture and present livelihood needs. By exploring the social-environment interactions, the study highlights the complexities and diversity of resource use for livelihoods that should be taken into consideration for both conservation and development policy interventions and research. The main argument of the study is that the contribution of natural resources to local livelihood portfolios in co- and community-managed areas, can be better understood through a consideration of cultural dynamics and institutional arrangements since these condition natural resource access, value and use.
- Full Text:
- Date Issued: 2011
Dynamics of macrophytes in the East Kleinemonde, a small temporarily open/closed South Afrcan Estuary
- Authors: Riddin, Taryn
- Date: 2011
- Subjects: Estuaries -- South Africa -- East Kleinemonde
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10605 , http://hdl.handle.net/10948/1529 , Estuaries -- South Africa -- East Kleinemonde
- Description: The East Kleinemonde Estuary is one of 175 temporarily open/closed estuaries (TOCEs) that represent 70 percent of estuaries in South Africa. TOCEs are small (mostly less than 100 ha), shallow estuaries (average depth < 2 m) that respond quickly to freshwater inflow events. Their connection to the sea can be highly variable resulting in considerable changes in abiotic and biotic conditions. Mouth status depends on a balance between freshwater inflow and marine influence, which in turn affects ambient abiotic conditions. The objective of the study was to identify the abiotic variables which influence macrophyte growth and habitat availability. It was hypothesised that water level and salinity were the two main drivers of macrophyte change and macrophyte habitat would respond very rapidly, in less than a month, when habitat was available. Macrophyte habitats would also have high sediment seed reserves to ensure persistence under highly variable abiotic conditions. Macrophyte cover was monitored monthly in the East Kleinemonde Estuary along three permanent transects. The dominant habitats were submerged macrophytes, intertidal salt marsh, supratidal salt marsh, reeds and sedges. The following abiotic variables; water level, water column salinity, water temperature, Secchi depth, air temperature and rainfall were also measured between March 2006 and January 2010. Time-lag responses of the macrophytes to water level and salinity changes up to four months prior to the sampling session were also assessed. The analysis of a one year dataset highlighted only water level as a driver of change in macrophyte cover, whereas the five year dataset identified salinity as an additional important abiotic driver. This is because during September 2008 to January 2010 a series of large marine overwash events maintained high salinity (> 30 ppt) and high water level (> 1.6 m amsl) in the estuary. Water level increased by up to 0.33 m due to large volumetric changes and salinity was significantly higher in the 16 month closed euhaline phase after the breach (31 ± 0.9 ppt) compared to 21.9 ± 0.9 ppt in the closed polyhaline phase before the September 2008 breach. This increase in salinity significantly reduced the cover of the submerged macrophytes Ruppia cirrhosa and Chara vulgaris. They were replaced by macroalgae during this high salinity phase. The cover of supratidal salt marsh and reed habitats was also significantly reduced during the high water level phase, which in turn would lead to the potential for bank destabilisation and erosion. Based on the average elevation above sea level position of the macrophytes in the East Kleinemonde iv Estuary, a threshold water level was identified as 1.55 amsl. This was taken to be the height above sea level at which there was a maximum cover change for each macrophyte habitat. Above this water level emergent macrophyte habitat would mainly be inundated. This, together with 30 ppt salinity, was identified as the two thresholds for macrophyte change in the East Kleinemonde Estuary. From these thresholds and the 5 year dataset four biotic states were identified as State A: open and tidal, State B: closed with a water level below 1.55 m amsl and salinity between 18 to 30 ppt, State C: closed and water level above 1.55 m amsl and salinity between 18 to 30 ppt and State D: closed and water level above 1.55 m amsl and salinity above 30 ppt. Intertidal salt marsh, reeds and sedges were dominant during the open phase. Submerged macrophytes were dominant during the closed polyhaline state and macroalgae during the closed euhaline state. The high variability of abiotic factors common in TOCEs and the response of macrophyte habitat indicated that macrophytes were resilient to changing states provided they were of relatively short (< 3 months) duration. Macrophytes in the East Kleinemonde Estuary were found to have fast growth rates and large seed reserves in the sediment. The seed banks in the East Kleinemonde, as well as the adjacent temporarily open/closed West Kleinemonde Estuary were quantified for the first time in a South African estuary. The averaged data from both estuaries showed that Charophyte öospores represented almost 72 percent of the sexual propagules in the sediment with a mean öospore density of 31 306 ± 2 293 m-2. This was despite the Charophytes being sparsely located and only representing a maximum of 32.5 percent cover in the above ground vegetation. Historically there must have been stands of Charophytes in the East Kleinemonde Estuary, such that öospores could accumulate to such high density found in this study. The second highest seed density was for the intertidal salt marsh plant Sarcocornia tegetaria (18 percent) (7 929 ± 688 seed m-2), followed by the submerged angiosperm Ruppia cirrhosa (7 percent) (2 852 ± 327 seeds m-2). Although seed density did not differ significantly with sediment depth, seeds still occurred at 20 cm below the surface of the sediment providing a regeneration source in the event of sediment scouring during a flood event. Germination studies in the greenhouse showed that most seeds were viable and Sarcocornia tegetaria began to germinate after 3 days to a maximum of 82 percent after 91 days. Submerged species only germinated after 18 days with a low maximum germination of between 11 and 15 percent. This study has made an original contribution to the field of knowledge on macrophyte responses in a small TOCE as it showed that macrophyte habitats in the East Kleinemonde Estuary have a high natural variability in cover over time, they respond quickly after a disturbance event such as a mouth breach and there are large sediment seed reserves that remain viable from 2 to more than 5 years. This ensures habitat persistence even under unfavourable conditions, such as prolonged periods of mouth closure with high water level and flooding which causes loss of salt marsh species. Given this natural variability it is necessary to predict responses both spatially and temporally in order to manage and maintain ecological functioning in TOCEs. This study identified dominant macrophyte habitat for different abiotic states through the use of water level and salinity thresholds. In the determination of the freshwater requirements of any South African estuary freshwater inflow rates are provided for each estuary's past, present and possible future freshwater inflow scenarios. These flow data are generated by hydrological models and simulated monthly inflow volumes for a period of about 72 years are provided. For the East Kleinemonde freshwater requirement study for any year in that 70-odd year period, the number of high flow and low flow mouth breaches were predicted, as well as the closed state periods. The threshold water level of 1.55 m amsl was also used to filter past, present and future inflow monthly volumes to determine the frequency of the four abiotic states identified in this study. It was based on a water level/water volume equation calculation from a digital elevation model. Results showed that the total closed period in the present state was 83 percent, made up of 48 percent of the time in a polyhaline state (State C) and 35 percent in a euahaline state (State D). A second method was used to quantify available spatial habitat under different water level scenarios. A spatial model was written in Model Builder, an application in ArcGIS that allowed a series of processes to be built. A habitat map was overlaid with a bathymetric map and by selecting water level, available habitat areas were determined and empirical equations of water level versus available habitat were produced. These equations were then used to calculate the available habitat areas for monthly water level conditions from the freshwater requirement study for the past, present and two future inflow scenarios. Using both the threshold water level method and the spatial availability model method it was possible to assess the effect of the two future inflow scenarios on macrophyte habitat vi response. Scenario 1 had a 16 percent reduction in mean annual runoff (MAR) generating low flows for 88.6 percent of the time and a 3.5 percent reduction in flood events. In Scenario 2 there would be a 12 percent reduction in MAR with low flows occurring for 87.5 percent of the year, a 5.3 percent reduction in floods and an 11.5 percent reduction in the open mouth state. The model showed that Scenario 1 would have the highest submerged macrophyte area (12.56 ha versus 12.48 ha in Scenario 2), whereas Scenario 2 produced the largest mudflat and intertidal salt marsh area (7.11 ha versus 7.34 ha) due to lower water level in conjunction with the bathymetry of the estuary. A reduction in freshwater inflow to TOCEs either due to anthropogenic influences or natural precipitation cycles is one of the main threats to the optimum functioning of these estuaries. The results from this study and the two methods of assessing the effect of freshwater inflow scenarios on macrophytes in TOCEs can be integrated into the current freshwater inflow assessment methodology in South Africa, as well as adding to our understanding of the ecological functioning of these small, highly variable estuaries. The methods provide a quick assessment of macrophyte habitat associated with abiotic states under past, present and future inflow scenarios. All that is required to predict macrophyte habitat for different freshwater inflow scenarios (present, past and future) is a habitat map, a bathymetric map and the elevation range of macrophytes in the TOCE being assessed. This, together with the knowledge of response rates, provides invaluable information for the management of TOCEs to maintain their ecological functioning under altered freshwater inflow regimes.
- Full Text:
- Date Issued: 2011
- Authors: Riddin, Taryn
- Date: 2011
- Subjects: Estuaries -- South Africa -- East Kleinemonde
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10605 , http://hdl.handle.net/10948/1529 , Estuaries -- South Africa -- East Kleinemonde
- Description: The East Kleinemonde Estuary is one of 175 temporarily open/closed estuaries (TOCEs) that represent 70 percent of estuaries in South Africa. TOCEs are small (mostly less than 100 ha), shallow estuaries (average depth < 2 m) that respond quickly to freshwater inflow events. Their connection to the sea can be highly variable resulting in considerable changes in abiotic and biotic conditions. Mouth status depends on a balance between freshwater inflow and marine influence, which in turn affects ambient abiotic conditions. The objective of the study was to identify the abiotic variables which influence macrophyte growth and habitat availability. It was hypothesised that water level and salinity were the two main drivers of macrophyte change and macrophyte habitat would respond very rapidly, in less than a month, when habitat was available. Macrophyte habitats would also have high sediment seed reserves to ensure persistence under highly variable abiotic conditions. Macrophyte cover was monitored monthly in the East Kleinemonde Estuary along three permanent transects. The dominant habitats were submerged macrophytes, intertidal salt marsh, supratidal salt marsh, reeds and sedges. The following abiotic variables; water level, water column salinity, water temperature, Secchi depth, air temperature and rainfall were also measured between March 2006 and January 2010. Time-lag responses of the macrophytes to water level and salinity changes up to four months prior to the sampling session were also assessed. The analysis of a one year dataset highlighted only water level as a driver of change in macrophyte cover, whereas the five year dataset identified salinity as an additional important abiotic driver. This is because during September 2008 to January 2010 a series of large marine overwash events maintained high salinity (> 30 ppt) and high water level (> 1.6 m amsl) in the estuary. Water level increased by up to 0.33 m due to large volumetric changes and salinity was significantly higher in the 16 month closed euhaline phase after the breach (31 ± 0.9 ppt) compared to 21.9 ± 0.9 ppt in the closed polyhaline phase before the September 2008 breach. This increase in salinity significantly reduced the cover of the submerged macrophytes Ruppia cirrhosa and Chara vulgaris. They were replaced by macroalgae during this high salinity phase. The cover of supratidal salt marsh and reed habitats was also significantly reduced during the high water level phase, which in turn would lead to the potential for bank destabilisation and erosion. Based on the average elevation above sea level position of the macrophytes in the East Kleinemonde iv Estuary, a threshold water level was identified as 1.55 amsl. This was taken to be the height above sea level at which there was a maximum cover change for each macrophyte habitat. Above this water level emergent macrophyte habitat would mainly be inundated. This, together with 30 ppt salinity, was identified as the two thresholds for macrophyte change in the East Kleinemonde Estuary. From these thresholds and the 5 year dataset four biotic states were identified as State A: open and tidal, State B: closed with a water level below 1.55 m amsl and salinity between 18 to 30 ppt, State C: closed and water level above 1.55 m amsl and salinity between 18 to 30 ppt and State D: closed and water level above 1.55 m amsl and salinity above 30 ppt. Intertidal salt marsh, reeds and sedges were dominant during the open phase. Submerged macrophytes were dominant during the closed polyhaline state and macroalgae during the closed euhaline state. The high variability of abiotic factors common in TOCEs and the response of macrophyte habitat indicated that macrophytes were resilient to changing states provided they were of relatively short (< 3 months) duration. Macrophytes in the East Kleinemonde Estuary were found to have fast growth rates and large seed reserves in the sediment. The seed banks in the East Kleinemonde, as well as the adjacent temporarily open/closed West Kleinemonde Estuary were quantified for the first time in a South African estuary. The averaged data from both estuaries showed that Charophyte öospores represented almost 72 percent of the sexual propagules in the sediment with a mean öospore density of 31 306 ± 2 293 m-2. This was despite the Charophytes being sparsely located and only representing a maximum of 32.5 percent cover in the above ground vegetation. Historically there must have been stands of Charophytes in the East Kleinemonde Estuary, such that öospores could accumulate to such high density found in this study. The second highest seed density was for the intertidal salt marsh plant Sarcocornia tegetaria (18 percent) (7 929 ± 688 seed m-2), followed by the submerged angiosperm Ruppia cirrhosa (7 percent) (2 852 ± 327 seeds m-2). Although seed density did not differ significantly with sediment depth, seeds still occurred at 20 cm below the surface of the sediment providing a regeneration source in the event of sediment scouring during a flood event. Germination studies in the greenhouse showed that most seeds were viable and Sarcocornia tegetaria began to germinate after 3 days to a maximum of 82 percent after 91 days. Submerged species only germinated after 18 days with a low maximum germination of between 11 and 15 percent. This study has made an original contribution to the field of knowledge on macrophyte responses in a small TOCE as it showed that macrophyte habitats in the East Kleinemonde Estuary have a high natural variability in cover over time, they respond quickly after a disturbance event such as a mouth breach and there are large sediment seed reserves that remain viable from 2 to more than 5 years. This ensures habitat persistence even under unfavourable conditions, such as prolonged periods of mouth closure with high water level and flooding which causes loss of salt marsh species. Given this natural variability it is necessary to predict responses both spatially and temporally in order to manage and maintain ecological functioning in TOCEs. This study identified dominant macrophyte habitat for different abiotic states through the use of water level and salinity thresholds. In the determination of the freshwater requirements of any South African estuary freshwater inflow rates are provided for each estuary's past, present and possible future freshwater inflow scenarios. These flow data are generated by hydrological models and simulated monthly inflow volumes for a period of about 72 years are provided. For the East Kleinemonde freshwater requirement study for any year in that 70-odd year period, the number of high flow and low flow mouth breaches were predicted, as well as the closed state periods. The threshold water level of 1.55 m amsl was also used to filter past, present and future inflow monthly volumes to determine the frequency of the four abiotic states identified in this study. It was based on a water level/water volume equation calculation from a digital elevation model. Results showed that the total closed period in the present state was 83 percent, made up of 48 percent of the time in a polyhaline state (State C) and 35 percent in a euahaline state (State D). A second method was used to quantify available spatial habitat under different water level scenarios. A spatial model was written in Model Builder, an application in ArcGIS that allowed a series of processes to be built. A habitat map was overlaid with a bathymetric map and by selecting water level, available habitat areas were determined and empirical equations of water level versus available habitat were produced. These equations were then used to calculate the available habitat areas for monthly water level conditions from the freshwater requirement study for the past, present and two future inflow scenarios. Using both the threshold water level method and the spatial availability model method it was possible to assess the effect of the two future inflow scenarios on macrophyte habitat vi response. Scenario 1 had a 16 percent reduction in mean annual runoff (MAR) generating low flows for 88.6 percent of the time and a 3.5 percent reduction in flood events. In Scenario 2 there would be a 12 percent reduction in MAR with low flows occurring for 87.5 percent of the year, a 5.3 percent reduction in floods and an 11.5 percent reduction in the open mouth state. The model showed that Scenario 1 would have the highest submerged macrophyte area (12.56 ha versus 12.48 ha in Scenario 2), whereas Scenario 2 produced the largest mudflat and intertidal salt marsh area (7.11 ha versus 7.34 ha) due to lower water level in conjunction with the bathymetry of the estuary. A reduction in freshwater inflow to TOCEs either due to anthropogenic influences or natural precipitation cycles is one of the main threats to the optimum functioning of these estuaries. The results from this study and the two methods of assessing the effect of freshwater inflow scenarios on macrophytes in TOCEs can be integrated into the current freshwater inflow assessment methodology in South Africa, as well as adding to our understanding of the ecological functioning of these small, highly variable estuaries. The methods provide a quick assessment of macrophyte habitat associated with abiotic states under past, present and future inflow scenarios. All that is required to predict macrophyte habitat for different freshwater inflow scenarios (present, past and future) is a habitat map, a bathymetric map and the elevation range of macrophytes in the TOCE being assessed. This, together with the knowledge of response rates, provides invaluable information for the management of TOCEs to maintain their ecological functioning under altered freshwater inflow regimes.
- Full Text:
- Date Issued: 2011
Economics of land reform models used in Mashonaland Central Province of Zimbabwe
- Authors: Musemwa, Lovemore
- Date: 2011
- Subjects: Land reform -- Zimbabwe , Agricultural productivity -- Zimbabwe , Land tenure -- Zimbabwe , Infrastructure (Economics) -- Government policy -- Zimbabwe , Land reform beneficiaries -- Zimbabwe , Land use -- Economic aspects -- Zimbabwe , Field crops -- Zimbabwe , Data envelopment analysis -- Zimbabwe , Land settlement -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11168 , http://hdl.handle.net/10353/435 , Land reform -- Zimbabwe , Agricultural productivity -- Zimbabwe , Land tenure -- Zimbabwe , Infrastructure (Economics) -- Government policy -- Zimbabwe , Land reform beneficiaries -- Zimbabwe , Land use -- Economic aspects -- Zimbabwe , Field crops -- Zimbabwe , Data envelopment analysis -- Zimbabwe , Land settlement -- Zimbabwe
- Description: The land reform that has unfolded in Zimbabwe since 1980 used different models and had diverse consequences. Since the implementation of the fast tract land reform programme in 2000, Zimbabwe experienced heavy reduction in yield and output at farm level that led to a 70% shortfall in production to meet annual food requirements (Richardson, 2005). The economic crisis in Zimbabwe has been characterized by worsening food insecurity especially in the rural areas where harvests continue to be poor. In the beef sector, Zimbabwe has failed to meet its export quota to the EU. The shortfall in production to meet annual food requirements shows a very grim situation but do not tell us about the performance of resettled farmers who now occupy much of the productive land. The broad objective of the study was to determine and compare the production efficiency of resettled farmers in Zimbabwe across land reform models. In addition, the study determined land use intensity. The study was conducted in the Mashonaland Central Province of Zimbabwe mainly because a wide variety of field crops were grown by resettled farmers. The respondents were stratified into three groups. These were: beneficiaries of land reform before 2000 (resettle scheme), fast track A1 model and fast track A2 model. The three models differ on how they were implemented and supported and this might result in different efficiencies of the models. A total of 245 copies structured questionnaire were administered on the resettled farmers from June to September 2010. Descriptive statistics was applied to the basic characteristics of the sampled households. The effect of model of land reform, gender of the household head, marital status, age of the household head, education, household size, religion, dependence ratio, whether the farmer was fulltime or part-time in farming, experience of the farmers in farming at that environment, total land size owned by the farmers and soil type on revenue per hectare and land use rate were determined using the GLM procedure of SAS (2003). Significance differences between least-square group means were compared using the PDIFF test of SAS (2003). The relationship between Revenue and land utilization was examined using the Pearson‟s correlations analysis. Dependance between response variables that had an effect on either revenue per hectare or land utilization with all the other response variables was tested using the Chi-square test for dependance. To find the effect of arable land used and herd size on revenue per hectare and land use the RSREG Procedure of SAS (2003) was used. Input oriented DEA model under the assumption of constant return to scale was used to estimate efficiency in this study. To identify factors that influence efficiency, a Tobit model censored at zero was selected. The mean land use rate varied significantly (p<0.05) with the land reform model with A2 having highest land use rate of 67%. The A1 and old resettlement households had land use rates of 53% and 46%, respectively. Sex, marital status, age of the household head, education and household size significantly affected land use (P<0.05). Revenue per hectare was not affected by any the factors that were inputted in the model. Results from the DEA approach showed that A2 farmers (large land owners) had an average technical efficiency score of 0.839, while the lowest ranking model (A1) had an average score of 0.618. Small land holders (A1 and the old resettled farmers) are on average less cost-efficient than large land owners, with a score of 0.29 for the former compared with 0.45 for the latter. From the factors that were entered in the Tobit model, age of household head, excellent production knowledge and farmer status affected technical efficiency whereas allocative efficiency was only affected by good production knowledge, farm size, arable land owned and area under cultivation. Factors which affected economic efficiency of the resettled farmers are secondary education, household size, farm size, cultivated area and arable land owned. None of the included socio-economic variables has significant effects on the allocative and economic efficiency of the resettled farmers. Thus, the allocative and economic inefficiencies of the farmers might be accounted for by other natural and environmental factors which were not captured in the model.
- Full Text:
- Date Issued: 2011
- Authors: Musemwa, Lovemore
- Date: 2011
- Subjects: Land reform -- Zimbabwe , Agricultural productivity -- Zimbabwe , Land tenure -- Zimbabwe , Infrastructure (Economics) -- Government policy -- Zimbabwe , Land reform beneficiaries -- Zimbabwe , Land use -- Economic aspects -- Zimbabwe , Field crops -- Zimbabwe , Data envelopment analysis -- Zimbabwe , Land settlement -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11168 , http://hdl.handle.net/10353/435 , Land reform -- Zimbabwe , Agricultural productivity -- Zimbabwe , Land tenure -- Zimbabwe , Infrastructure (Economics) -- Government policy -- Zimbabwe , Land reform beneficiaries -- Zimbabwe , Land use -- Economic aspects -- Zimbabwe , Field crops -- Zimbabwe , Data envelopment analysis -- Zimbabwe , Land settlement -- Zimbabwe
- Description: The land reform that has unfolded in Zimbabwe since 1980 used different models and had diverse consequences. Since the implementation of the fast tract land reform programme in 2000, Zimbabwe experienced heavy reduction in yield and output at farm level that led to a 70% shortfall in production to meet annual food requirements (Richardson, 2005). The economic crisis in Zimbabwe has been characterized by worsening food insecurity especially in the rural areas where harvests continue to be poor. In the beef sector, Zimbabwe has failed to meet its export quota to the EU. The shortfall in production to meet annual food requirements shows a very grim situation but do not tell us about the performance of resettled farmers who now occupy much of the productive land. The broad objective of the study was to determine and compare the production efficiency of resettled farmers in Zimbabwe across land reform models. In addition, the study determined land use intensity. The study was conducted in the Mashonaland Central Province of Zimbabwe mainly because a wide variety of field crops were grown by resettled farmers. The respondents were stratified into three groups. These were: beneficiaries of land reform before 2000 (resettle scheme), fast track A1 model and fast track A2 model. The three models differ on how they were implemented and supported and this might result in different efficiencies of the models. A total of 245 copies structured questionnaire were administered on the resettled farmers from June to September 2010. Descriptive statistics was applied to the basic characteristics of the sampled households. The effect of model of land reform, gender of the household head, marital status, age of the household head, education, household size, religion, dependence ratio, whether the farmer was fulltime or part-time in farming, experience of the farmers in farming at that environment, total land size owned by the farmers and soil type on revenue per hectare and land use rate were determined using the GLM procedure of SAS (2003). Significance differences between least-square group means were compared using the PDIFF test of SAS (2003). The relationship between Revenue and land utilization was examined using the Pearson‟s correlations analysis. Dependance between response variables that had an effect on either revenue per hectare or land utilization with all the other response variables was tested using the Chi-square test for dependance. To find the effect of arable land used and herd size on revenue per hectare and land use the RSREG Procedure of SAS (2003) was used. Input oriented DEA model under the assumption of constant return to scale was used to estimate efficiency in this study. To identify factors that influence efficiency, a Tobit model censored at zero was selected. The mean land use rate varied significantly (p<0.05) with the land reform model with A2 having highest land use rate of 67%. The A1 and old resettlement households had land use rates of 53% and 46%, respectively. Sex, marital status, age of the household head, education and household size significantly affected land use (P<0.05). Revenue per hectare was not affected by any the factors that were inputted in the model. Results from the DEA approach showed that A2 farmers (large land owners) had an average technical efficiency score of 0.839, while the lowest ranking model (A1) had an average score of 0.618. Small land holders (A1 and the old resettled farmers) are on average less cost-efficient than large land owners, with a score of 0.29 for the former compared with 0.45 for the latter. From the factors that were entered in the Tobit model, age of household head, excellent production knowledge and farmer status affected technical efficiency whereas allocative efficiency was only affected by good production knowledge, farm size, arable land owned and area under cultivation. Factors which affected economic efficiency of the resettled farmers are secondary education, household size, farm size, cultivated area and arable land owned. None of the included socio-economic variables has significant effects on the allocative and economic efficiency of the resettled farmers. Thus, the allocative and economic inefficiencies of the farmers might be accounted for by other natural and environmental factors which were not captured in the model.
- Full Text:
- Date Issued: 2011
Effect of alkaline pre-treatments on the synergistic enzymatic hydrolysis of sugarcane (Saccharum officinarum) bagasse by Clostridium cellulovorans XynA, ManA and ArfA
- Authors: Beukes, Natasha
- Date: 2011
- Subjects: Sugarcane -- Biotechnology Lignocellulose -- Biotechnology Renewable energy sources Hydrolysis Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3952 , http://hdl.handle.net/10962/d1004011
- Description: The continual increase in industrialization and global population has increased the dependency and demand on traditional fossil fuels for energy; however, there are limited amounts of fossil fuels available. The slow depletion of fossil fuels has sparked a fresh interest in renewable sources such as lignocellulose to produce a variety of biofuels, such as biogases (e.g. methane), bioethanol, biodiesel and a variety of other solvents and economically valuable by-products. Agricultural crop wastes produced in surplus are typically lignocellulosic in composition and thus partially recalcitrant to enzymatic degradation. The recalcitrant nature of plant biomass and the inability to obtain complete enzymatic hydrolysis has led to the establishment of various pre-treatment strategies. Alkaline pre-treatments increase the accessibility of the exposed surface to enzymatic hydrolysis through the removal of acetyl and uronic acid substituents on hemicellulose. Unlike the use of steam and acid pre-treatments, alkaline pre-treatments solubilize lignin and a small percentage of the hemicellulose, increasing enzyme accessibility and thus the hydrolysis of lignocellulose. The majority of Clostridium cellulovorans associated enzyme synergy studies have been devoted to an understanding of the cellulolytic and hemi-cellulolytic degradation of plant cell walls. However, little is known about the effect of various physical and chemical pre-treatments on the synergistic enzymatic degradation of plant biomass and possible depolymerization of plant cell walls. This study investigates the use of slake lime, sodium hydroxide and ammonium hydroxide to pre-treat sugarcane bagasse under mild conditions and elucidates potentially important synergistic associations between the C. cellulovorans enzymes for the enhanced degradation of lignocellulose. The primary aims of the study were addressed using of a variety of techniques. This included suitable vector constructs for the expression and purification of recombinant C. cellulovorans enzymes, identification of the effects of various pre-treatments on enzyme synergy, and identification of the resultant reducing sugars and phenolic compounds (released during the pre-treatment of the bagasse). This study also made use of physical and chemical pre-treatment methods, protein purification using affinity, high performance liquid and thin layer chromatography, mass spectrometry, sodium dodecyl sulphate and fluorophore-assisted polyacrylamide gel electrophoresis (FACE) , enzymatic degradation and synergy studies with various substrates indirectly using the 3, 4-dinitrosalicylic acid (DNS) reducing sugar assay. From this investigation, the following conclusions were made: alkaline pre-treatment successfully solublised, redistributed and removed lignin from the bagasse, increasing the digestibility of the substrates. In summary, the most effective pre-treatment employed 0.114 M ammonium hydroxide / gram bagasse at 70°C for 36 hours, followed by hydrolysis with an enzyme cocktail containing 25% ManA and 75% XynA. This increased the production of sugars approximately 13-fold. Analysis of the sugars produced by the synergistic hydrolysis of sugarcane bagasse (SCB) indicated the presence of xylose, indicating that the enzymes are potentially bifunctional under certain conditions. This study indicated that the use of mild pre-treatment conditions sufficiently removed a large portion of lignin without affecting the hemicellulose moiety of the SCB. This facilitated the potential use of the hemicellulose component for the production of valuable products (e.g. xylitol) in addition to the production of bioethanol. Thus, the potential use of additional components of holocellulose may generate an additional biotechnological benefit and allow a certain degree of flexibility in the biofuel industry, depending on consumer and industrial needs.
- Full Text:
- Date Issued: 2011
- Authors: Beukes, Natasha
- Date: 2011
- Subjects: Sugarcane -- Biotechnology Lignocellulose -- Biotechnology Renewable energy sources Hydrolysis Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3952 , http://hdl.handle.net/10962/d1004011
- Description: The continual increase in industrialization and global population has increased the dependency and demand on traditional fossil fuels for energy; however, there are limited amounts of fossil fuels available. The slow depletion of fossil fuels has sparked a fresh interest in renewable sources such as lignocellulose to produce a variety of biofuels, such as biogases (e.g. methane), bioethanol, biodiesel and a variety of other solvents and economically valuable by-products. Agricultural crop wastes produced in surplus are typically lignocellulosic in composition and thus partially recalcitrant to enzymatic degradation. The recalcitrant nature of plant biomass and the inability to obtain complete enzymatic hydrolysis has led to the establishment of various pre-treatment strategies. Alkaline pre-treatments increase the accessibility of the exposed surface to enzymatic hydrolysis through the removal of acetyl and uronic acid substituents on hemicellulose. Unlike the use of steam and acid pre-treatments, alkaline pre-treatments solubilize lignin and a small percentage of the hemicellulose, increasing enzyme accessibility and thus the hydrolysis of lignocellulose. The majority of Clostridium cellulovorans associated enzyme synergy studies have been devoted to an understanding of the cellulolytic and hemi-cellulolytic degradation of plant cell walls. However, little is known about the effect of various physical and chemical pre-treatments on the synergistic enzymatic degradation of plant biomass and possible depolymerization of plant cell walls. This study investigates the use of slake lime, sodium hydroxide and ammonium hydroxide to pre-treat sugarcane bagasse under mild conditions and elucidates potentially important synergistic associations between the C. cellulovorans enzymes for the enhanced degradation of lignocellulose. The primary aims of the study were addressed using of a variety of techniques. This included suitable vector constructs for the expression and purification of recombinant C. cellulovorans enzymes, identification of the effects of various pre-treatments on enzyme synergy, and identification of the resultant reducing sugars and phenolic compounds (released during the pre-treatment of the bagasse). This study also made use of physical and chemical pre-treatment methods, protein purification using affinity, high performance liquid and thin layer chromatography, mass spectrometry, sodium dodecyl sulphate and fluorophore-assisted polyacrylamide gel electrophoresis (FACE) , enzymatic degradation and synergy studies with various substrates indirectly using the 3, 4-dinitrosalicylic acid (DNS) reducing sugar assay. From this investigation, the following conclusions were made: alkaline pre-treatment successfully solublised, redistributed and removed lignin from the bagasse, increasing the digestibility of the substrates. In summary, the most effective pre-treatment employed 0.114 M ammonium hydroxide / gram bagasse at 70°C for 36 hours, followed by hydrolysis with an enzyme cocktail containing 25% ManA and 75% XynA. This increased the production of sugars approximately 13-fold. Analysis of the sugars produced by the synergistic hydrolysis of sugarcane bagasse (SCB) indicated the presence of xylose, indicating that the enzymes are potentially bifunctional under certain conditions. This study indicated that the use of mild pre-treatment conditions sufficiently removed a large portion of lignin without affecting the hemicellulose moiety of the SCB. This facilitated the potential use of the hemicellulose component for the production of valuable products (e.g. xylitol) in addition to the production of bioethanol. Thus, the potential use of additional components of holocellulose may generate an additional biotechnological benefit and allow a certain degree of flexibility in the biofuel industry, depending on consumer and industrial needs.
- Full Text:
- Date Issued: 2011
Effect of nanoparticles on the photophysicochemical behaviour of metallophthalocyanines
- Moeno, Sharon Keitumetse Gail Mpheletso
- Authors: Moeno, Sharon Keitumetse Gail Mpheletso
- Date: 2011 , 2011-03-30
- Subjects: Phthalocyanines Nanoparticles Photochemistry Quantum dots
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4310 , http://hdl.handle.net/10962/d1004968
- Description: The synthesis, spectroscopic characterization, and studies of the photophysicochemical behaviour of selective anionic, cationic and neutral metallophthallocyanine (MPc) complexes were carried out and the results are presented herein. Studies on the effect of the central metal ion, the solvent used and the presence of nanoparticles on the photophysicochemical properties were conducted. The findings showed that the photophysicochemical parameters were mostly enhanced in the presence of central metal ions of high atomic numbers and also in the presence of nanoparticles. It was also observed that solvents that encouraged the monomericity of the MPc complexes also lead to improved photophysical and photochemical behaviour. CdTe quantum dots (QDs) stabilized with mercaptocarbonic acids were also observed to cause stimulated emission of the MPcs through Förster resonance energy transfer (FRET) thus acting as energy donors while the respective MPc acted as energy acceptors in all the FRET studies. FRET was observed following the photoexcitation of QDs for all monomeric anionic MPcs but it was also shown to occur for some cationic MPcs in organic media. Both the substituent and solvent used were found to exert a strong influence on the occurrence of FRET. Other cationic MPcs however showed different behaviour in the presence of the meraptocarbonic stabilized CdTe QDs; with the cationic porphyrazine giving clear indications of Pc ring reduction. The rest of the cationic MPcs did not give clear evidence of Pc ring reduction, instead they showed signs of aggregate formation possibly from the assembly of electrostatic ion pair complexes which could result in reduction of the quaternized pyridinium ring of the substituent. Both the QDs and the MPc complex emission spectra were significantly quenched for each in the presence of the other. Stern-Volmer quenching studies indicated that both static and dynamic quenching of the QDs in the presence of MPcs took place. The fluorescence lifetimes of the mercaptopropionic acid (MPA) capped CdTe QDs in the presence of various MPc complexes showed quenching of mostly the longer lifetimes of the QDs in the presence of MPcs suggesting that the surface defects and states are involved in the interaction of the QDs and MPcs. An MPc complex terminating in thio tethers was employed in the conjugation to AuNPs. Spectroscopic and microscopic studies confirmed the formation of the MPc-AuNP conjugate which was also shown to exhibit improved photophysicochemical properties compared to the free MPc.
- Full Text:
- Date Issued: 2011
- Authors: Moeno, Sharon Keitumetse Gail Mpheletso
- Date: 2011 , 2011-03-30
- Subjects: Phthalocyanines Nanoparticles Photochemistry Quantum dots
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4310 , http://hdl.handle.net/10962/d1004968
- Description: The synthesis, spectroscopic characterization, and studies of the photophysicochemical behaviour of selective anionic, cationic and neutral metallophthallocyanine (MPc) complexes were carried out and the results are presented herein. Studies on the effect of the central metal ion, the solvent used and the presence of nanoparticles on the photophysicochemical properties were conducted. The findings showed that the photophysicochemical parameters were mostly enhanced in the presence of central metal ions of high atomic numbers and also in the presence of nanoparticles. It was also observed that solvents that encouraged the monomericity of the MPc complexes also lead to improved photophysical and photochemical behaviour. CdTe quantum dots (QDs) stabilized with mercaptocarbonic acids were also observed to cause stimulated emission of the MPcs through Förster resonance energy transfer (FRET) thus acting as energy donors while the respective MPc acted as energy acceptors in all the FRET studies. FRET was observed following the photoexcitation of QDs for all monomeric anionic MPcs but it was also shown to occur for some cationic MPcs in organic media. Both the substituent and solvent used were found to exert a strong influence on the occurrence of FRET. Other cationic MPcs however showed different behaviour in the presence of the meraptocarbonic stabilized CdTe QDs; with the cationic porphyrazine giving clear indications of Pc ring reduction. The rest of the cationic MPcs did not give clear evidence of Pc ring reduction, instead they showed signs of aggregate formation possibly from the assembly of electrostatic ion pair complexes which could result in reduction of the quaternized pyridinium ring of the substituent. Both the QDs and the MPc complex emission spectra were significantly quenched for each in the presence of the other. Stern-Volmer quenching studies indicated that both static and dynamic quenching of the QDs in the presence of MPcs took place. The fluorescence lifetimes of the mercaptopropionic acid (MPA) capped CdTe QDs in the presence of various MPc complexes showed quenching of mostly the longer lifetimes of the QDs in the presence of MPcs suggesting that the surface defects and states are involved in the interaction of the QDs and MPcs. An MPc complex terminating in thio tethers was employed in the conjugation to AuNPs. Spectroscopic and microscopic studies confirmed the formation of the MPc-AuNP conjugate which was also shown to exhibit improved photophysicochemical properties compared to the free MPc.
- Full Text:
- Date Issued: 2011