Hydrogen peroxide generation and antioxidant enzyme activities in the leaves and roots of wheat cultivars subjected to long-term soil drought stress

The dynamics of the activity of catalase, ascorbate peroxidase, guaiacol peroxidase, and benzidine peroxidase, as well as the level of hydrogen peroxide in the vegetative organs of durum wheat (Triticum durum Desf.) cultivars was studied under long-term soil drought conditions. It was established that hydrogen peroxide generation occurred at early stages of stress in the tolerant variety Barakatli-95, whereas in the susceptible variety Garagylchyg-2 its significant amounts were accumulated only at later stages. Garagylchyg-2 shows a larger reduction of photochemical activity of PS II in both genotypes at all stages of ontogenesis under drought stress than Barakatli-95. The highest activity of catalase which plays a leading role in the neutralization of hydrogen peroxide was observed in the leaves and roots of the drought-tolerant variety Barakatli-95. Despite the fact that the protection system also includes peroxidases, the activity of these enzymes even after synthesis of their new portions is substantially lower compared with catalase. Native PAGE electrophoresis revealed the presence of one isoform of CAT, seven isoforms of APX, three isoforms of GPO, and three isoforms of BPO in the leaves, and also three isoforms of CAT, four isoforms of APX, two isoforms of GPO, and six isoforms of BPO in the roots of wheat. One isoform of CAT was found in the roots when water supply was normal and three isoforms were observed under drought conditions. Stress associated with long-term soil drought in the roots of wheat has led to an increase in the heterogeneity due to the formation of two new sedentary forms of catalase: CAT2 and CAT3.