Genotypic Differences in Leaf Water Potential, Abscisic Acid and Proline Concentrations in Spring Wheat during Drought Stress

Abstract

Recent work with spring wheat has revealed significant genotypic variation in changes of water potential and abscisic acid (ABA) concentration in response to drought Two experiments with eight spring wheat genotypes have been carried out to check the earlier work on relationships between water potential and ABA concentration and to examine causes of genotypic variation in the rate of decline of water potential during drought Changes in proline concentration were also studied Plants were grown in controlled environment cabinets with nutrient solution culture and were stressed by withholding water as the fifth or sixth leaf on the main stem emerged. Plants were harvested 4, 5 and 6 days after the treatment commenced and measurements of leaf water potential, stomatal conductance, ABA and proline concentrations, and tissue d wts were taken. Significant genotypic variation was found in the decrease of water potential with time and in the slopes of linear regressions of ABA concentration on water potential, confirming earlier results When differences between leaf areas at the start of the treatment were minimised by varying the genotype sowing date significant genotypic variation in water potentials at harvest was still obtained. The change in water potential was significantly positively correlated with shoot root d wt ratios at harvest and pre-treatment stomatal conductances. Proline concentrations were significantly correlated with water potential for every genotype, although there was no clear evidence of genotypic variation in proline concentrations at a given water potential The possible role of ABA concentration in drought resistance of cereals is discussed