Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 8, 2007) Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2000. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

No description available.

Thesis (M. Env. St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1993. / Includes bibliographical references (leaves 101-107).

Thesis (Ph.D.)--University of Melbourne, School of Forest and Ecosystem Science, 2006. / Typescript. Includes bibliographical references (leaves 184-216).

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 20, 2007) Vita. Includes bibliographical references.

Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2009. / Full text also available online. Scroll down for electronic link.

Thesis (M.Sc. Agriculture (Horticulture)) -- University of Limpopo, 2017 / Artemisia annua L. from the family Asteraceae is an annual medicinal plant and has been used to make herbal remedies in Asia for thousands of years. Artemisinin is a sesquiterpene lactone, isolated from aerial parts of Artemisia annua, with the highest concentrations being in flowers and leaves. In addition to potent anti-malarial activity, artemisinin possesses anti-cancer, anti-schistosomiatic, anti-hepatitis B, anti-HIV, anti-leishmanial and herbicidal activities. Low artemisinin production (0.01-2%) from A. annua is a major constraint in commercialisation of the drug for control of malaria. Worldwide, efforts have been underway to improve the concentration of artemisinin using conventional breeding, biochemical, physiological, molecular and hairy-root culture techniques, however all these methods are not economical. Cultural practices like spacing and pruning have limitation in improving artemisinin concentration and these may help in increasing the concentrations of artemisinin. Study was conducted at the experimental farm of the Agricultural Research Council – Vegetable and Ornamental Plants, Roodeplaat Pretoria. The objective of this study was to determine whether spacing, pruning and their interactions would have any effect on the concentrations of artemisinin, growth and yield of A. annua and whether drying methods would have an effect on the concentrations of artemisinin in A. annua. Since there was only one field trial, all sub-objectives were addressed at once (Chapter 3). Fresh seeds of A. annua were obtained from the ARC-VOP gene bank and sown in seedling trays in September 2014. Uniform eight-week-old seedlings were hardened-off, transplanted in November 2014 in 10 cm deep holes and then pruned ten weeks after transplanting. Treatments for Experiment 1, viz., 3 × 4 factorial experiment were laid out in a randomised complete block design, with four replications (n = 48). The two factors of the experiment were (a) spacing [0.5 × 1 m2 (standard: 0.50 m2), 0.5 × 0.7 m2 (small: 0.35 m2) 0.5 × 0.5 m2 (smaller: 0.25 m2) and 0.3 × 0.7 m2 (smallest: 0.21 m2)] and (b) pruning [no pruning (control), removing the apical bud and removing shoots three nodes from the bottom]. The plants were irrigated using overhead sprinklers system for two hours three times per week. Four readings for growth variables (plant height, stem diameter and chlorophyll content) were collected with one week interval. Plants were harvested after 180 days from planting, and leaves, stems and roots were separated weighed and oven dried at 40 ºC for 72 h. In Experiment 2 (drying methods), treatments, namely, 100% sun, 100% shade, 50% shade, freeze and oven drying were arranged in completely randomised design with four replicates (n = 20). The treatments were exposed for a week, to full sunlight, 50% shade-drying under a shade net that allows 50% light penetration, 100% shade under enclosed room at ambient (24-25 ºC) temperature, oven drying for 24 h at 40 ºC, and freeze-drying for three days. Freeze-drying had significant effect on artemisinin concentration of 1.941%. It was followed by oven (1.738%) and 100% shade drying (1.657%) and the lowest artemisinin concentration (1.412%) was obtained from 50% shade drying. The smaller spacing of 0.25 m2 in combination with apical bud removal had a significant effect on artemisinin concentration, producing artemisinin concentration of 0.193%. Spacing had a significant effect on stem diameter, fresh leaf mass and dry leaf mass but had no effect on plant height and chlorophyll content. Pruning had a significant effect on plant height and chlorophyll content and had no effect on stem diameter. The small spacing of 0.35 m2 had the highest fresh and dry leaf mass of 17.99 and 9.62 t/ha. The interaction of spacing and pruning had no significant effect on the growth and yield of A. annua. The results from this study suggested that cultural and processing practices may have direct effects in the concentration of artemisinin, growth and yield of A. annua. The results xiv provided some understanding on how agronomic and processing practices can be used to increase artemisinin content in A. annua and understand the interaction between different agronomic practices and thereby allowing the development of economic methods for A. annua post-harvest handling. Future work should focus on implementing various pruning techniques to trigger stress and indirectly secondary metabolites

Thesis (PhD (Forest and Wood Science))—University of Stellenbosch, 2007. / Sustainable livestock production in semi-arid Botswana could be improved through tree planting on-farm to provide much needed protein and shade. Such action can be encouraged if the growth, productivity, nutritional value of trees and their contribution to mass gain of livestock are known.. A study at Malotwana investigated two indigenous species, Acacia galpinii and Faidherbia albida, and two exotic species, Leucaena diversifolia and L. leucocephala, at three spacings in a randomised complete block design replicated five times. The three spacings represented 400, 317 and 241 trees per hectare. The study was conducted over 6.5 years. Indigenous trees were sampled biennially and exotics annually to evaluate crown width, height, stem diameter, stem number and stem volume index. Complete plant harvesting of exotic trees at 2.5, 4.5 and 6.5 years evaluated agroforestry production. Leaves from all four species and pods of exotic species were analysed for chemical composition. Two groups of eight lambs were balanced for mass at selection for an on-farm feeding trial. Browse from exotic trees, comprising a 2:1 ratio of pods to leaves, was fed at 30% as supplement to hay to one group whose mean mass was contrasted with that of the control group fed sorghum bran at 30%. A. galpinii was a promising species, adaptable to planting away from its origin. Its crown width ranged from 5.86 m in high density plots to 6.08 m at low density and was significantly different among stands (p = 0.0406) at 6.5 years. Diameter at breast height (dbh) was significantly different among stands aged 6.5 years (p = 0.0003) and ranged between 10.38 cm at high density to 12.48 cm in low density plots, demonstrating a capacity to provide both shade and poles on-farm. At 4.5 years, F. albida attained a mean height of 4.5 m and 4.5 cm in dbh but suffered 67% mortality during a severe drought. Annual fodder production of 0.647 and 0.996 metric tonnes ha-1 for leaves and pods of L. diversifolia and 1.237 and 1.431 for L. leucocephala was recorded in years of average rainfall. Yields of 0.3 and 0.59 metric tonnes ha-1 were recorded for both species in the driest year. Equally good agroforestry production was obtained from both low and high density stands suggesting that low density plantings, which foster higher plant survival and reduce disease incidence, are best suited to the semi-arid conditions of Botswana. The crude protein of leaves ranged between 16.26 (L. diversifolia) and 25.25% (F. albida). They were highly digestible with more than twice the calcium content livestock require. Crude protein and digestibility measures were significantly different among leaves and varied significantly at different spacings (p<0.0001). Pods of the exotic species contained significantly more protein than the leaves (p<0.0001). Lambs supplemented with browse gained 102.33 g per animal per day while the control group gained 83.95 g. There were significant differences between groups during growth (p<0.05). Growing of A. galpinii, complemented with L. diversifolia and L. leucocephala, can supply short and long term feed, and greatly enhance livestock production while diversifying farm feed sources

Sclerocarya birrea (marula, Anacardiaceae) is a highly-valued indigenous tree in most parts of sub-Saharan Africa because of its medicinal and nutritional properties. The marula tree is adapted to the semi-arid conditions that characterise most parts of sub-Saharan Africa and renders them unsuitable for conventional crop agriculture. The unique nutritional properties of marula and its high tolerance to dry conditions provide opportunities for its development into a plantation crop. On the other hand, the demand for marula plant parts, mainly the bark and roots as medicinal remedies, poses a great threat to wild populations. In the long term, the growing demand of marula products in the food, pharmaceutical and cosmetic industries will not be sustainable from wild populations alone. Plant tissue culture technologies can be useful for in vitro manipulation and mass propagation of the plant in the process of domestication and conservation. The aims of the project were to determine the optimum conditions for seed germination, in vitro propagation and plant regeneration, and to evaluate the potential bioactivity of secondary metabolites from its renewable plant parts as an alternative option in the conservation of S. birrea. An ex vitro seed germination study indicated that after-ripening and cold stratification are critical factors. Cold stratification (5 °C) of marula nuts for 14 days improved germination (65%) as compared to non-stratified nuts (32%). Direct shoot organogenesis was achieved from leaf explants through the induction of nodular meristemoids on Murashige and Skoog (MS) (1962) medium and woody plant medium (WPM) supplemented with 6-benzyladenine (BA) in combination with naphthalene acetic acid (NAA), indole-3-butryric acid (IBA) and indole-3-acetic acid (IAA). Induction of nodular meristemoids from 86% of the leaf cultures was achieved on a MS medium with 4.0 ìM BA and 1.0 ìM NAA. High levels (78–100%) of induction were also achieved on WPM with different concentrations of BA (1.0–4.0 ìM) and IBA (1.0–4.0 ìM). The highest conversion of nodular meristemoids into shoots on MS initiation medium was only 22% for 4.0 ìM BA and 1.0 ìM NAA. This was improved to 62% when nodular clusters were cultured in MS liquid medium. Histological studies revealed high numbers of unipolar meristematic buds developing from globular nodules. These embryo-like structures have in the past been mistaken for true somatic embryos. The initiation of high numbers of nodular meristemoids per explant provides potential for automated large-scale clonal propagation in bioreactors, in vitro phytochemical production and the development of synthetic seed technology, similar to somatic embryogenesis. Plant regeneration through nodule culture has potential for application in mass micropropagation and plant breeding of S. birrea. Adventitious shoot and root induction are important phases in micropropagation. Plant growth regulators play an important role in these developmental processes, and the type and concentration used have major influences on the eventual organogenic pathway. Three auxins (IAA, IBA and NAA) and four aromatic cytokinins (6-benzyladenine, meta-topolin, meta-topolin riboside, and meta-methoxytopolin riboside) were evaluated for their potential to induce adventitious shoot and root formation in S. birrea shoots, hypocotyls and epicotyls. Among the evaluated cytokinins, the highest adventitious shoot induction (62%) was achieved on MS medium supplemented with meta-topolin (8.0 ìM). The lowest adventitious shoot induction (2.5%) was obtained on MS basal medium containing 2.0 ìM meta-methoxytopolin riboside. The highest adventitious shoot induction for hypocotyls was 55% on MS medium supplemented with 8.0 ìM meta-topolin. For the tested auxins, IBA induced adventitious rooting in 91% of shoots at a concentration of 4.0 ìM after 8 weeks in culture. However, the in vitro rooted plants only survived for two weeks when transferred ex vitro. A temperature of 25 °C and 16-h photoperiod were optimum for adventitious root induction. Stomatal density (number per mm2) on the abaxial leaf surfaces was higher for the 16-h photoperiod treatment (206.6 ± 15.28) compared to that for a 24-h photoperiod (134.6 ± 12.98). Normal mature stomata with kidney-shaped guard cells and an outer ledge over the stomatal pore were observed for in vitro plants growing under a 16-h photoperiod. Total phenolic content, proanthocyanidins, gallotannins, flavonoids, and antioxidant activities of S. birrea methanolic extracts were evaluated using in vitro bioassays. Methanolic extracts of the young stem bark and leaves contained high levels of these phytochemicals. Sclerocarya birrea young stem extracts contained the highest levels of total phenolics (14.15 ± 0.03 mg GAE g-1), flavonoids (1219.39 ± 16.62 ìg CE g-1) and gallotannins (246.12 ± 3.76 ìg GAE g-1). Sclerocarya birrea leaf extracts had the highest concentration of proanthocyanidins (1.25%). The EC50 values of the extracts in the DPPH free radical scavenging assay ranged from 5.028 to 6.921 ìg ml-1, compared to ascorbic acid (6.868 ìg ml-1). A dose-dependent linear curve was obtained for all extracts in the ferric-reducing power assay. All the extracts exhibited high antioxidant activity comparable to butylated hydroxytoluene based on the rate of â-carotene bleaching (89.6 to 93.9%). Sclerocarya birrea provides a source of secondary metabolites which have potent antioxidant properties and may be beneficial to the health of consumers. Sclerocarya birrea young stem and leaf ethanolic extracts exhibited high bioactivity (MIC < 1.0 mg ml-1) against both Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria. The highest activity (MIC = 0.098 mg ml-1 and total activity = 1609.1 ml g-1) was recorded for young stem extracts against B. subtilis. The highest activity (MIC = 1.56 mg ml-1 and MFC = 1.56 mg ml-1) in the antifungal assay against Candida albicans was observed for young stem ethanolic extracts. Sclerocarya birrea extracts had moderate acetylcholinesterase (AChE) inhibition activity. The dichloromethane (DCM) and methanol (MeOH) fractions exhibited dose-dependent acetylcholinesterase inhibitory activity. The highest AChE inhibitory activities were from leaves (DCM fraction, IC50 = 0.1053 mg ml-1) and young stems (MeOH fraction, IC50 = 0.478 mg ml-1). High inhibitory activity against cyclooxygenase (COX-1 and COX-2) enzymes was observed. All extracts and fractions showed high COX-1 enzyme inhibition (90.7-100%). Petroleum ether (PE) and dichloromethane fractions also exhibited high inhibition against COX-2 enzyme (77.7-92.6%). The pharmacological activities observed suggest that S. birrea renewable plant parts (leaves and young stems) provide a substantial source of medicinal secondary metabolites. Based on these results, plant part substitution can be a practical conservation strategy for this species. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.