Browsing by Author "Mafa, Paseka"

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    Phylogenetic relationships of the African species of the genus Merxmuellera Conert (Poaceae: Danthonioideae)
    (2001) Mafa, Paseka; Linder, Peter; Barker, N P
    This study expands on existing molecular (rpoC2 and ITS) and morphological data sets to further test the hypothesis of non-monophyly of Merxmuellera sensu lato. The results reveal that despite high levels of resolution, the morphological data yield poorly supported phylogenies due to high levels of homoplasy in the dataset.
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    Response of Cynodon dactylon (L.) Pers. to ammonium and nitrate nutrition
    (1999) Mafa, Paseka; Stock, WD
    Plants that come early in succession predominantly prefer_ ammonium form of nitrogen than nitrate. The hypothesis that Cynodon dactylon (L.) Pers., a grass in the primary succession stage would respond well when supplied with ammonium than nitrate fertiliser was tested. Seedlings of Cynodon dactylon were grown in culture solution and fertilised with either ammonium sulphate or potassium nitrate at ~ continuous concentrations of 200 ppm, 400 ppm and 600 ppm in the growth chamber. In support of my hypothesis, growth of Cynodon dactylon was greater from ammonium than nitrate nutrition in terms of aboveground and total plants yields at 200 ppm and 400 ppm and this was associated with efficient utilisation of this form of nitrogen by this species. Production from the nitrate treatments was restricted and showed no change with increase in external nitrogen supply. Decreased dry weights from the ammonium nutrition at 600 ppm were associated with toxicity of ammonium ions in plant tissues. High levels of nitrogen measured from the nitrate treatments were associated with the soluble nitrogen that was not assimilated for yield increase by this grass, Uptake of ammonium ion was shown to result· in high of uptake phosphorus. This study shows that Cynodon dactylon has the capacity for increased growth under ammonium nutrition while this was limited in the nitrate nutrition. However, response is restricted when excessively fertilised with ammonium nitrogen.
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    Species limits in the Rhodocoma gigantea (Kunth) Linder complex
    (1999) Mafa, Paseka; Linder, H Peter
    Rhodocoma gigantea and Rhodocoma foliosus have been recognised by earlier authors as separate species on the basis of perianth length and shape. Linder (1985) superficially lumped these two species under Rhodocoma gigantea arguing that the difference between the two appear to be brought by ecological gradient. Numerical phenetic analyses of 19 quantitative floral morphological characters investigated from 33 herbarium specimens reveal that Rhodocoma gigantea complex consists of two groups. One group corresponded to Rhodocoma gigantea, having longer and wider spikelets, perianth segments and bracts, while the other correspond to Rhodocoma foliosus having shorter and thinner female spikelets, bracts and perianth segments than the former. Minimum spanning tree also reveal the two groups are geographically isolated. The former group occur in the western part of the south coast along the Langeberg in Swellendam and Riversdale districts and the latter is widely distributed on the Outeniekwaberg, Tsitsikama mountains to Zuurberg with outliers reaching as far as Uitenhage. The Gouritz river appears to be the geographical barrier between these two species. The species boundaries of this complex are discussed and the two groups are suggested to be separated based on the phenetic species concepts.