Effect of abscisic acid application on enzymatic and non-enzymatic activity in barley (Hordeum vulgare L. )

Leaves of Hordeum vulgar (line L1911) were sprayed at maximum vegetative growth in four concentrations of abscisic acid (0, 50, 200, 800 µm). The experiment was performed on the research field of Warvick University in UK in 2003. Samples were taken from treated leaves in interval time including 5, 10, 20 and 40h after application. For each sample, the amount of superoxide (O_2­^-) and hydrogen peroxide (H₂O₂) content, the activity of enzymes involved in defense system including superoxide dismutase (SOD), catalase (CAT), ascorbic peroxidase and glutathione reductase were measured and determined. The content of several non-enzymatic antioxidants such as ascorbate, α-tocopherol and carotenoid and the degrees of oxidative damage (TBARM assay) were examined. The obtained results revealed that maximum levels of superoxide and hydrogen peroxide radicals were produced at 10h after ABA spray and declined slightly at 20 and 40h after spray. During the whole process of sampling, the maximum level of these radicals were produced by 800µm ABA concentration. For all of the studied enzymes, despite of minor differences, the activity of all the activity of all enzymes showed significant increase by ABA spray in compare with control (water spray). Also, degrees of oxidative damage (TBARM level) showed significant increase by the effect of ABA concentration. In general the results of this study showed moderate concentration of ABA particularly 50µm induce enzymatic and non enzymatic defense system prevents plant from oxidative damages.