The effect of abscisic acid on rate of photosynthesis and transpiration in six barley genotypes under water stress

For six barley genotypes evaluated from various climatic areas mild water stress resulted in reduced gas exchange parameters (P N a E). For all (except the Mexican Namoi) there was a fall in the water use efficiency (WUE). The largest fall was recorded for the French genotype Adagio. Treating the plants with abscisic acid under a mild water stress resulted in all genotypes showing further, statistically significant reductions in P N (except for the wild W 154) and E in comparison with untreated plants. ABA under mild water stress supported the plant’s water conservation and in a number of cases also improved the WUE (for the Czech genotype Maridol, the English Braemar, the French Adagio, the Israeli wild W 154 and partially in the Yugoslavian Novosadski).