Browsing by Author "Mitchell, Derek"

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    Aspects of phosphorus nutrition in endomycorrhizal fungi of the Ericaceae
    (1986) Straker, Colin John; Mitchell, Derek
    An investigation was undertaken on the phosphorus nutrition of the ericoid endophytes isolated from the root systems of Vaccinium macrocarpon, Aiton, Rhododendron ponticum L., Calluna vulgaris (L.) Hull, Erica hispidula L., and E. mauritanica L.
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    The biology of poplar rust in the South Western Cape with special reference to the carbon physiology of the host-biotroph relationship
    (1977) Roberts, Sharon Mary; Mitchell, Derek
    An investigation of the host-obligate biotroph relationship of a commonly occurring rust fungus in the South Western Cape, Melampsora sp., infecting Populus canescens (Aiton) Sm., was stimulated by the apparently non-harmful effect of the pathogen on its host. The healthy appearance of the infected poplar tree and the lack of morphological changes in the leaves of infected shoots suggested that the rust was a benign obligate biotroph which, in the absence of its alternate hosts, appears to be adapted to a compatible existence with one host. The ready availability of poplar stands in the South Western Cape which are regularly infected with rust provided the opportunity to study the seasonal changes in carbohydrate levels and composition, total nitrogen levels and dry weight in the healthy and rust-infected poplar leaves. Further information was obtained by feeding entire shoots or single leaves of shoots with ¹⁴CO₂, then assessing levels of ¹⁴C-assimilate and following the translocation of ¹⁴C in the healthy and infected host.
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    Response of a sand-plain lowland fynbos ecosystem to nutrient additions
    (1988) Witkowski, Edward Tadeusz Fernando; Mitchell, Derek
    The effects of a complete factorial fertilizer addition of nitrogen (N), phosphorus (P) and a mixture of all essential nutrients excluding N and P (M) on various components of the soils and vegetation of a sand-plain lowland fynbos ecosystem at Pella, south-western Cape Province, South Africawere studied, namely: 1) Soil nutrient dynamics. 2) Phenology, shoot growth, reproductive output and nutrient acquisition in a proteoid (Leucospermum parile) and an ericoid (Phylica cephalantha) evergreen shrub. 3) Dry mass, phosphorus and nitrogen allocations to the various above and below ground organs of pre-reproductive and reproductive male plants of Thamnochortus punctatus (Restionaceae). 4) Litter production and nutrient return. 5) Above-ground phytomass, nitrogen and phosphorus contents of the representative plant growth forms in response to non-factorial addition of N, P and M. 6) Foliage projective cover of the representative growth forms of sand-plain lowland fynbos.