The Effect of Abscisic Acid on Stomatal Gases Exchange in Six Barley Genotypes under Water Stress.

The spring barley plants were grown in a physiological greenhouse in pots under controlled conditions. For six genotypes evaluated from various climatic areas mild water stress resulted in reduced gas exchange parameters – rate of photosynthesis (P_N) and rate of transpiration (E). For all (except the Mexican Namoi) there was a fall in the water use efficiency (WUE = P_N/E). The largest fall was recorded for the French genotype Adagio. From the standpoint of WUE the Adagio was the most sensitive variety to a mild water stress, in contrast the Namoi was the least sensitive variety. 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).

Acknowledgements
This work was prepared with the support of Ministry of Education, Youth and Sports grant no. MSM 6046070901.