Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (MTech (Agriculture))--Cape Peninsula University of Technology, 2014. / Plants require nitrogen (N) to support desired production levels. Nitrogen fertilization strategy is a major consideration in field management with regard to achieving both economic and environmental objectives. For instance, in potato, insufficient N supply reduces tuber size and overall yield while excessive N supply can reduce tuber quality and increase environmental risk through nitrate (NO3-) leaching and nitrous oxide emission. Selection of an adequate N fertilizer application rate for crops is difficult, due to marked variations in soil N supply and crop N demand in both the field and over time. This research was conducted to characterise the ammonium transporter gene (AMT1) of Bambara groundnut and potato using molecular biology and bioinformatics methods. Nucleotide database sequences were used to design AMT1-specific primers which were used to amplify and sequence the core-region of the gene from Bambara groundnut and potato. Bioinformatics techniques were used to predict the structure and infer properties of the proteins. Nucleotide sequence alignment and phylogenetic analysis indicate that BgAMT1 and PoAMT1 are indeed from the AMT1 family, due to the clade and high similarity they respectively shared with other plant AMT1 genes. Amino acid sequence alignment showed that BgAMT1 is 92%, 89% and 87% similar to PvAMT1.1, GlycineAMT1 and LjAMT1.1 respectively, while PoAMT1 is 92%, 83% and 76% similar to LeAMT1.1, LjAMT1.1 and LeAMT1.2 respectively. BgAMT1 and PoAMT1 fragments were shown to correspond to the 5th - 10th transmembrane spanning-domains. Mutation of Bg W1A-L and S28A (for BgAMT1) and Po S70A (for PoAMT1) is predicted to enhance ammonium (NH4+) transport activity. Residues Bg D23 (for BgAMT1) and Po D16 (for PoAMT1) must be preserved otherwise NH4+ transport activity is inhibited. In all, BgAMT1 and PoAMT1 play a role in N uptake from the root while BgAMT1 may contribute more in different steps of rhizobia interaction. In an investigation of the correlation between AMT1 gene expression levels and leaf chlorophyll content index (CCI) with plant N status, potato plants were grown in a hydroponic greenhouse with 0.75 or 7.5 mM NO3- and 0.75 or 7.5 mM NH4+ as forms of N supply in a completely randomized design. Leaf CCI as measured by chlorophyll content meter, showed that an increase in N supply results in increased leaf CCI in response to both forms of N. Total RNA was isolated from leaf sampled at 28 days after treatment and expression level of the AMT1 gene was determined by reverse transcription-qPCR using a second set of primers designed for qPCR. The results showed that expression levels of AMT1 increased from 8.731 ± 2.606 when NO3- supply was high to 24.655 ± 2.93 when NO3- supply was low. However, there was no significant response in AMT1 expression levels to changes in NH4+. This result suggested that AMT1 transports NO3- less efficiently than NH4+, and thus more transport channels are required in the cell membrane when NO3- levels are low. Such variation in AMT1 expression levels are not necessary for NH4+ transport since the transport mechanism for NH4+ is efficient even at low NH4+ levels.

No description available.

No description available.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1985 S757 / Master of Science

Translocation involves the movement of organisms, by human intervention, from one area to other suitable (receptor) habitats. In a conservation context, translocation can be employed to support species preservation, population restoration and/or for ecological research. Despite decades of internationally published research, translocation remains a controversial endeavour. However, due to continual degradation and fragmentation of natural habitats in the face of human development, translocation is becoming a vital component of conservation efforts. Prior to the development of an Exxaro coal mine in Mpumalanga, a population of an endangered Highveld succulent species, Frithia humilis Burgoyne (Aizoaceae/Mesembryanthemaceae), was saved from extirpation by means of translocation. Three receptor habitats were identified within the distribution range of the species. The largest part of the donor population was transplanted to sandstone outcrops of the Ecca Group (Karoo Supergroup), resulting in four subpopulations residing on geological substrates typical of the species’ habitat. The remaining portion of the donor population was experimentally translocated to two habitats containing non-native geologies, namely sedimentary outcrops of the Wilge River Formation (Waterberg Group) and (igneous) felsite oucrops of the Rooiberg Group (Transvaal Supergroup). A control population was identified, occupying Ecca and Dwyka Group (Karoo Supergroup) sediments, as a measure to compare the response of translocated populations. A monitoring programme, utilising a plant age classification system, was initiated in February of 2010 to elucidate demographic trends and to gauge the response of translocated populations to novel environments. Plant survival, plant growth, flowering, fruiting (representing reproductive response) and seedling emergence were chosen as indicators to measure translocation success over the short term. Furthermore, quantitative and qualitative entomological investigations into the identity of possible F. humilis pollinators, as well as the presence of pollinator species at receptor habitats, were made. A repeatable methodology for post-translocation monitoring and scientifically sound baseline data for future comparative purposes were successfully established. Initial results showed that F. humilis subpopulations replanted on Ecca standstones had positive responses to translocation: Subpopulations survived and all but one increased in size. Individual plant growth increased, higher reproductive output was evident and seedling emergence was pervasive. Positive responses indicated that F. humilis populations translocated onto typical geologies had the potential to establish and persist over three years. Knowledge of this early success is of immense value to the conservation of the species, as a limited number of known natural populations remain. Coal mining, targeting coal seams underlying typical F. humilis habitats, is also likely to remain a threat. The viability of translocating F. humilis populations to non-typical geological substrates has shown limited efficacy. Poor survival along with inferior reproductive response confirmed Wilge River Formation outcrops as poor receptor sites for translocated F. humilis populations. Rooiberg felsite outcrops also proved to be dubious receptor sites, primarily since there was a downward trend in seedling emergence over time, suggesting inferior germination conditions. Nevertheless, translocation to non-native geological substrates did not have disastrous short-term consequences for these populations, since flowering, fruit production and seedling emergence continued, albeit at reduced (or continually declining) rates. Potential pollinator species of F. humilis were not revealed through quantitative surveys of insect diversity. Qualitative surveys proved more efficient and accurate at pinpointing insect pollinator species. This study provided the first evidence of Apidae, Megachilidae (Hymenoptera) and Bombyliidae (Diptera) insect species pollinating F. humilis. The generalist nature of the plant-pollinator relationship, as well as the presence of generalist pollinator species at some receptor habitats, probably contributed to the initial positive response of F. humilis flowering and fruiting after translocation. Results from this study, however promising, should be viewed as initial indications of translocation success. The literature review revealed a plethora of literature recommending post-translocation monitoring programmes for five years to several decades. This study confirmed that successful establishment of F. humilis can be determined after three years, but that long-term monitoring is required to evaluate persistence. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Translocation involves the movement of organisms, by human intervention, from one area to other suitable (receptor) habitats. In a conservation context, translocation can be employed to support species preservation, population restoration and/or for ecological research. Despite decades of internationally published research, translocation remains a controversial endeavour. However, due to continual degradation and fragmentation of natural habitats in the face of human development, translocation is becoming a vital component of conservation efforts. Prior to the development of an Exxaro coal mine in Mpumalanga, a population of an endangered Highveld succulent species, Frithia humilis Burgoyne (Aizoaceae/Mesembryanthemaceae), was saved from extirpation by means of translocation. Three receptor habitats were identified within the distribution range of the species. The largest part of the donor population was transplanted to sandstone outcrops of the Ecca Group (Karoo Supergroup), resulting in four subpopulations residing on geological substrates typical of the species’ habitat. The remaining portion of the donor population was experimentally translocated to two habitats containing non-native geologies, namely sedimentary outcrops of the Wilge River Formation (Waterberg Group) and (igneous) felsite oucrops of the Rooiberg Group (Transvaal Supergroup). A control population was identified, occupying Ecca and Dwyka Group (Karoo Supergroup) sediments, as a measure to compare the response of translocated populations. A monitoring programme, utilising a plant age classification system, was initiated in February of 2010 to elucidate demographic trends and to gauge the response of translocated populations to novel environments. Plant survival, plant growth, flowering, fruiting (representing reproductive response) and seedling emergence were chosen as indicators to measure translocation success over the short term. Furthermore, quantitative and qualitative entomological investigations into the identity of possible F. humilis pollinators, as well as the presence of pollinator species at receptor habitats, were made. A repeatable methodology for post-translocation monitoring and scientifically sound baseline data for future comparative purposes were successfully established. Initial results showed that F. humilis subpopulations replanted on Ecca standstones had positive responses to translocation: Subpopulations survived and all but one increased in size. Individual plant growth increased, higher reproductive output was evident and seedling emergence was pervasive. Positive responses indicated that F. humilis populations translocated onto typical geologies had the potential to establish and persist over three years. Knowledge of this early success is of immense value to the conservation of the species, as a limited number of known natural populations remain. Coal mining, targeting coal seams underlying typical F. humilis habitats, is also likely to remain a threat. The viability of translocating F. humilis populations to non-typical geological substrates has shown limited efficacy. Poor survival along with inferior reproductive response confirmed Wilge River Formation outcrops as poor receptor sites for translocated F. humilis populations. Rooiberg felsite outcrops also proved to be dubious receptor sites, primarily since there was a downward trend in seedling emergence over time, suggesting inferior germination conditions. Nevertheless, translocation to non-native geological substrates did not have disastrous short-term consequences for these populations, since flowering, fruit production and seedling emergence continued, albeit at reduced (or continually declining) rates. Potential pollinator species of F. humilis were not revealed through quantitative surveys of insect diversity. Qualitative surveys proved more efficient and accurate at pinpointing insect pollinator species. This study provided the first evidence of Apidae, Megachilidae (Hymenoptera) and Bombyliidae (Diptera) insect species pollinating F. humilis. The generalist nature of the plant-pollinator relationship, as well as the presence of generalist pollinator species at some receptor habitats, probably contributed to the initial positive response of F. humilis flowering and fruiting after translocation. Results from this study, however promising, should be viewed as initial indications of translocation success. The literature review revealed a plethora of literature recommending post-translocation monitoring programmes for five years to several decades. This study confirmed that successful establishment of F. humilis can be determined after three years, but that long-term monitoring is required to evaluate persistence. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Shen, Jinbo. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 110-119). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.