P. D. R. Van Heerden

Evaluation of proline accumulation as an indicator of drought tolerance in spring wheat cultivars

The aim of this study was to evaluate proline accumulation as an indicator of drought stress and drought tolerance in spring wheat cultivars (Triticum aestivum L.) grown in the Western Cape. Drought stress was induced in whole plants and leaf discs in two cultivars with known drought tolerance, namely, Gamtoos (drought tolerant) and S ST 66 (slightly drought sensitive), as well as in two cultivars with unknown drought tolerance, namely, Nantes and SST 44. To assess the effect of growth stage on the reaction of the cultivars to drought stress, stress was induced during pre-anthesis and also during anthesis. Proline accumulation in whole plants showed clear genotypical differences during pre-anthesis and, to a lesser extent, during anthesis. A positive correlation between the degree (onset and extent) of proline accumulation and drought tolerance was found for Gamtoos and SST 66. Proline accumulation patterns in leaf discs did not correlate with results obtained with whole plants.

Evaluation of the relative water content and the reduction of 2,3,5-triphenyltetrazoliumchloride as indicators of drought tolerance in spring wheat cultivars

The aim of this study was to evaluate the relative water content and the reduction of 2,3,5-triphenyltetrazoliumchloride, as indicators of drought stress and drought tolerance in spring wheat cultivars (Triticum aestivum L.) grown in the Western Cape. Drought stress was induced in two cultivars with known drought tolerance, namely, Gamtoos (drought tolerant) and SST 66 (slightly drought sensitive), as well as in two cultivars with unknown drought tolerance, namely, Nantes and SST 44. To assess the effect of growth stage on the reaction of the cultivars to drought stress, stress was induced during pre-anthesis and also during anthesis. Relative water content patterns for the different cultivars showed clear genotypical differences during pre-anthesis and, to a lesser extent, during anthesis. A positive correlation between the ability to maintain relative water content levels and drought tolerance was found for Gamtoos and SST 66. The results obtained with the reduction of 2,3,5-triphenyltetrazoliumchloride...

Radioisotope studies in isolated perfused baboon kidneys

Abstract Radioisotopic studies were performed on baboon kidneys during isolated bloodless perfusion. The perfusion was equilibrated with either 100% oxygen or 100% helium gas. The clearance of 133 Xe was found to be a very sensitive method in assessing renal circulation. Oxygen had a vasoconstrictive effect on the cortical vessels resulting in a decreased renal cortical perfusion flow. The distribution of labeled carbon microspheres did not reflect a difference in cortical flow during oxygen and helium exposure. Particles of the size employed did not remain fixed in the vascular tree. In some instances free or unbound isotope was detected. 203 Hg chlormerodrin was poorly concentrated both during oxygen and helium exposure, presumably as a result of the absence of plasma proteins in the perfusate. Helium-exposed kidneys showed a more normal distribution and excretion of 131 I hippuran than oxygen-exposed kidneys.