Potassium and phosphate absorption by excised ordinary and proteoid roots of the Proteaceae

Potassium and phosphate absorption by excised ordinary and proteoid roots of certain species of the Proteaceae was investigated, using 86Rb (as substitute for 42K) and 32P as tracers. The respiratory uncoupler, 2,4-dinitrophenol (DNP), inhibited the uptake of potassium and phosphate. The greater inhibition obtained with proteoid roots possibly suggests that they possess a greater capacity for metabolic absorption than the ordinary roots. Absorption of potassium and phosphate over a concentration range of 0,005 – 50mmol dm−3 KCI and KH2PO4 respectively, was investigated. Lineweaver-Burk kinetic analysis of the data on potassium absorption in the low concentration range (0,005 – 1,0mmol dm−3 KCI) revealed a more effective absorption mechanism in the case of proteoid roots. Kinetic analysis of the data on phosphate absorption in both the low (0,02 – 1,0mmol dm−3 KH2PO4) and high (1,0 – 50mmol dm−3 KH2PO4) concentration ranges points to a more effective absorption mechanism in proteoid roots. Phosphate absorption by proteoid roots showed a distinct peak between pH 4 and 5,5

Beskrywing van 'n apparaat om gaswisseling oor kort periodes by lammers te bepaal

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Biogeography of prostrate-leaved geophytes in semi-arid South Africa: Hypotheses on functionality

Nowhere is the species diversity of geophytes greater than in the five mediterranean-climate ecosystems of the world. Of these, the Cape mediterranean zone of South Africa is the most speciose. While the relative diversity and importance of geophytes of all of the other four mediterranean regions of the world drops off sharply as one moves into adjacent winter-rainfall desert regions, geophytes in the semi-arid to arid Succulent Karoo (including Namaqualand) remain a very important component of the flora, both in terms of abundance and diversity (comprising 13 to 29% of the regional floras in this region). Apart from species richness, there are also a number of interesting geophyte growth forms in this region. One unusual growth form is geophytes with flattened leaves that lie prostrate on the soil surface. At least eight families (Amaryllidaceae, Colchicaceae, Eriospermaceae, Geraniaceae, Hyacinthaceae, Iridaceae, Orchidaceae and Oxalidaceae) exhibit this growth form. While this growth form is relatively common in many geophyte lineages in the Succulent Karoo biome and the Cape mediterranean zone (Fynbos biome), and occurs infrequently through the summer-rainfall temperate regions of Africa, it is virtually absent in other regions worldwide. A null hypothesis is that the prostrate leaved trait is a neutral characteristic, however biogeographical data do not support this. A neutral trait would be unlikely to show such a clear pattern of distribution. Several alternative hypotheses on the adaptive significance of this growth form are discussed. These include: avoidance of herbivory, reduction in competition from neighbors, creation of a CO2 enriched environment below the leaves, reduction of water loss around the roots, reduction of water loss through transpiration, precipitation of dew on the leaves and maintenance of optimal leaf temperatures for growth.Articl

An electrically operated automatic feeder for sheep

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Stock production in the Karoo Region.

The Karoo Region, an arid to semi-arid extensive small stock grazing area, is described. The main factors concerning stock production are covered. These are elucidated and supported by research data and references. Management aspects and situations generally hampering stock production are degradation of the vegetation, overgrazing, drought, economic vicissitudes, fluctuating forage and nutritional supply, stock diseases, insect pest and detrimental management practices. Measures to promote stock production are discussed. These are sound veld and stock management practices, which include stock reduction, rotational systems, diversification of stock, control of diseases and parasites, reproduction, breeding and supplementary feeding, and proper physical facilities. The future of stock production in the Karoo Region is summarised.Keywords: breeding; degradation; diseases; drought; forage; grazing; karoo; karoo agricultural region; management; overgrazing; parasites; reproduction; semi-arid; small stock; south africa; supplementary feeding; vegetatio