Growth, mineral content and essential oil quality of buchu (Agathosma betulina) in response to ph under controlled conditions in comparison with plants from its natural habitat

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dc.contributor.advisor Langenhoven, P.
dc.contributor.advisor Agenbag, G. A.
dc.contributor.author Ntwana, Babalwa en_ZA
dc.contributor.other University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy.
dc.date.accessioned 2008-04-10T07:11:05Z en_ZA
dc.date.accessioned 2010-06-01T08:28:59Z
dc.date.available 2008-04-10T07:11:05Z en_ZA
dc.date.available 2010-06-01T08:28:59Z
dc.date.issued 2007-12 en_ZA
dc.identifier.uri http://hdl.handle.net/10019.1/1626
dc.description Thesis (MScAgric (Agronomy)--University of Stellenbosch, 2007.
dc.description.abstract The Cape Floristic Region is a highly distinctive phytogeographical unit which is recognized as a floral Kingdom on its own. Buchu (Agathosma betulina) plants fall under this important Kingdom. Buchu is one of the traditional medicinal plants originating in the Western Cape province of South Africa and the essential oil derived from the leaves is exported in large volumes. Due to high demand, under supply, restrictions of wild harvesting and high prices for Buchu essential oil, growers have started to introduce and commercialize this species as a crop. This commercialization of Buchu necessitated agronomic research to optimize production techniques. The objective of this study was to determine the optimum pH range for the cultivation of high yielding Buchu with acceptable essential oil quality under controlled conditions and compare this with the conditions in the natural habitat. Plant, soil and climatic data were gathered from eleven sites in the natural habitat of Buchu (A. betulina) in the Cederberg Mountains. At all sites most rainfall occurred from May to September, while high temperatures were recorded in summer. Soil analyses indicated low levels of nutrients and low soil pH, ranging from 3.7 to 5.3 at all the sites studied. Low levels of nutrients were also obtained from foliar analysis collected from plants at each of the different sites. Chemical analyses of the essential oil indicated that the plants were from a high quality diosphenol chemotype. In the greenhouse experiment, five different pH levels (pH 33.99, 4-4.99, 5-5.99, 6-6.99 and 7-7.99) were evaluated to determine the effect on growth, yield and quality of A. betulina. Complete nutrient solutions were used to irrigate the plants grown in pots filled with a sand and coco peat mixture. Although the plants subjected to the pH treatment of 4-4.99 tended to have the highest growth rate and yield, this did not differ significantly (P=0.05) from plants subjected to pH values between 3 and 6.99. In contrast, the pH 7-7.99 treatment lead to reduced growth and lower vegetative yields. Levels of nutrients obtained from the leaf mineral analysis differed significantly with different pH treatments. High pH levels resulted in high nitrogen, phosphorus, sodium, manganese and boron contents, but lower contents of copper. Nitrogen, phosphorus, calcium and zinc were higher than those recorded for plants from their natural habitat, but still within the norm reported for most plants. Levels of manganese, sodium, magnesium and copper were found to be more or less similar to the values obtained in plants from the natural habitat. No significant differences were found in essential oil quality in response to the pH treatments. However, high pulegone levels (10.8 to 13.2 %) were obtained from all the treatments in the greenhouse experiment. The high levels of this essential oil constituent could have a negative effect on the marketability of the oil and this aspect may need some attention in future studies. en_ZA
dc.format.extent 1126239 bytes en_ZA
dc.format.mimetype application/pdf en_ZA
dc.language.iso en en_ZA
dc.publisher Stellenbosch : University of Stellenbosch
dc.subject Dissertations -- Agriculture en
dc.subject Theses -- Agriculture en
dc.subject Dissertations -- Agronomy en
dc.subject Greenhouse plants en
dc.subject Essences and essential oils en
dc.subject Buchu -- Growth en
dc.subject Buchu -- Mineral content en
dc.subject Agathosma betulina en
dc.subject Theses -- Agronomy
dc.title Growth, mineral content and essential oil quality of buchu (Agathosma betulina) in response to ph under controlled conditions in comparison with plants from its natural habitat en_ZA
dc.type Thesis en_ZA
dc.rights.holder University of Stellenbosch


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