The introduction of democracy in country of post-Apartheid South Africa precipitated both economic and social changes. These changes have led to the liberalisation of the economy and the movement of the agricultural sector from being highly regulated to a market-based sector. Consequently, the country‟s economy has become exposed to global uncertainties. These changes brought about the need for role players to understand the dynamics of the agricultural sector in order to forecast possible future trends and assess their impact on agricultural production and consumption. Projecting economic and environmental uncertainties in agriculture is essential to make informed decisions and sustain agribusinesses.</li> In an attempt to combat the challenges and to understand the dynamics mentioned above, a system of equations with the ability to simulate the dynamic interaction between production and consumption at a regional level for South African potato producers, policy makers and wholesalers, is developed in this study. Existing methodology on partial equilibrium modelling is applied to develop a tool that can be used to analyse the potential impact of relative environmental shifts on the South African potato industry. Individual equations, which are | vi collapsed into a single system of equations, are estimated by means of Ordinary Least Square (OLS). The specific objectives of this study are as follows: <ul> <li> To estimate the potato area planted, yield and consumption of various categories of potatoes, in order to determine the price elasticity of demand and elasticity of supply.</li> <li> To develop a system of equations that will be used to generate baseline projections of demand and supply in the industry.</li> <li> To undertake impact analysis of various scenarios over the period 2011 to 2015. Although the model developed is mainly South African focusing on regional production and national consumption, the dissertation will recommend the possibility of future studies that use this study as a springboard for further research. These recommended studies include the linking of other models to improve and simulate relations between the potato sector and other sectors, thereby emulating the actual economy.</li> <li> One such requirement is to connect the vegetable and potato industries, a move which agricultural sector experts believe will benefit the outcomes of the potato industry.</li></ul> Consumption is estimated at national level, and is conducted according to the use of informal fresh and formal fresh potatoes for processing and seed potatoes. It is advisable for future research and study to estimate and project production and consumption at regional level. The baseline projection will be developed, and then the study will further undertake several scenarios which will lead to various possible future outcomes, discusses and document the response. Eventually, the model shows possible relationships, uncertainties and interactions between potato productions, consumption and prices. And that the domestic price, quantity demanded, the supply and the net exports actually determine the South African market equilibrium price and the decision to export in the South African potato industry. This is also called the near autarky situation. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Agricultural Economics, Extension and Rural Development / unrestricted

M.Sc. (Biochemistry) / A rich diversity of medicinal plants is found in Southern Africa and approximately 80% of the population still relies on medicinal plants to fulfil its primary health care needs. Many of these medicinal plants are used to treat ailments such as burns, sores, urinary tract infections, colds, flu, rheumatism, gout, cancer, hypertension, diabetes, human immunodeficiency virus infections and acquired immunodeficiency syndrome. An example of such a plant is Hypoxis hemerocallidea (Fisch & CA Mey), formerly known as Hypoxis rooperi and popularly known as the African potato, from the Hypoxidaceae family. This plant is found across five of the South African provinces and corm extracts are reported to contain bioactive compounds that account for the plant’s medicinal and therapeutic properties. This study was conducted to investigate the anti-oesophageal cancer and antimicrobial potential of H. hemerocallidea. In cancer patients, the currently used cancer treatments such as radiotherapy and chemotherapy are ineffective in decreasing disease progression, prolonging survival, providing cure and are associated with side-effects such as cytotoxicity to normal body cells and tumour non-specificity. Therefore, current cancer research is aiming at searching for novel plant-based anticancer compounds that can be used for the development and manufacturing of cancer treatment drugs that will have less side-effects and less toxicity towards the normal human body cells, and ultimately provide cure for cancer. In addition to cancer, infectious diseases still contribute to most premature deaths worldwide and are now becoming more difficult to treat due to multidrug resistance developed by pathogens against many of the currently used antibiotics. This multidrug resistance of human pathogens to antibiotics has led to a search for new antimicrobial compounds from plants sources, for use in the production of new affordable antibiotic drugs to effectively treat infections without posing any unwanted toxicity and harm towards the human body. An oesophageal SNO cancer cell line was treated with H. hemerocallidea extracts and the effect of the extracts on the cancer cells were investigated with cell viability assays (trypan blue dye exclusion and AlamarBlue® viability assays), light microscopy and flow cytometrical analysis (forward and side scatter analysis). The plant extracts were also tested for antimicrobial activities against various microorganisms - Gram-positive and Gram-negative bacteria, yeast and fungi cultures by means of thin layer chromatographic bioautography (TLC-DB), microdilution assays and the BacTiter-GloTM assay. Antimicrobial compounds were then putatively identified and characterised using gas chromatography-mass spectrometry (GC-MS). No morphological changes were observed in the SNO cells and significant cell death did not occur following treatment with either water or ethanolic H. hemerocallidea extracts from fresh or dried corms or leaves. The ethanolic leaf extracts did not show any significant inhibition against any of the microorganisms tested in contrast to the ethanolic extracts from the corms, which showed microbial growth inhibition against Gram-positive bacteria and fungi and partial inhibition of the Gram-negative bacteria. The bioactive compounds responsible for the antibacterial and antifungal activities were identified as levoglucosan (as the major antimicrobial compound), pyrocatechol and hexahydro-3-(2-methylpropyl)-pyrrolo[1,2-α]pyrazine-1,4-dione. These results show that H. hemerocallidea plant extracts possessed no anticancer effects towards the SNO cell line. In addition, the corm extracts of H. hemerocallidea contain a levoglucosan compound, which may work synergistically with other antimicrobial compounds to exert antimicrobial properties. With more research, the antimicrobial compounds in H. hemerocallidea may hold promise for possible candidates for use in the development of antibiotic or antiseptic products (for example, topical creams and lozenges) to be used in the treatment of skin and soft tissue infections caused by bacterial and fungal infections.