Genotypic Variation in Leaf Water Potential, Stomatal Conductance and Abscisic Acid Concentration in Spring Wheat Subjected to Artificial Drought Stress

Abstract

A technique for studying variation in the accumulation of abscisic acid (ABA) in response to drought stress is described. Two experiments, each testing 26 spring wheat genotypes, were carried out using pot grown plants in controlled environment cabinets with nutrient solution culture, though the results of only one experiment are described in detail. Plants were subjected to water stress by withholding water as the fifth or sixth leaf on the main stem was emerging. Two stressed plants of each genotype were harvested 5 and 7 days after the treatment commenced and measurements of leaf water potential, stomatal conductance and ABA concentration were taken. There was considerable genotypic variation in the rate at which water potential decreased, partly explained by variation in plant size. Inia 66 (a genotype common to both experiments) had consistently much lower water potentials than the other genotypes. Stomatal conductances of all genotypes decreased rapidly and after 5 and 7 days they were negatively correlated with the changes in water potential. ABA concentrations varied considerably between genotypes after both 5 and 7 days without water, the variation being associated with genotypic differences in water potential on these occasions. The overall relationship between ABA concentration and water potential was highly significant. Significant differences between the slopes of the regressions for individual genotypes were found. The cultivar Sirius accumulated the most ABA at any water potential and Pelissier, Wascana and Hybrid 46 accumulated the least. The significance for drought resistance of variation in ABA accumulation is discussed.