Influence of drought stress on the levels of antioxidative defense systems during germination and early tillering stages in wheat genotypes differing in drought susceptibility

V ABSTRACT: Wheat genotypes differing in drought resistance under field conditions were tested for their antioxidative potentials under drought stress both during germination and early tillering stages. The genotypes used were the bread wheats Dagdas (resistant) and SBVD 1-2 (sensitive) and the durum wheat BDMM-19 (sensitive). During the germination stage drought stress was created by PEG-6000 treatment. The PEG-6000 treatment at a rate of 20% (w/v) had resulted in severe depressions in germination and seedling growth. These depressions were associated with decreases in ascorbate peroxidase activity of genotypes, particularly in the drought sensitive wheat genotype. In the early tillering stage, drought stress was initiated by withholding water and lasted for 12 days. The activities of antioxidative enzymes were clearly affected and increased over 12 days of water deficiency. However, no remarkable difference among the genotypes in activities of enzymes was detected. By contrast, with severity of drought stress, the genotypes differed in their membrane permeability (membrane damage), chlorophyll concentration and content of SH-groups. Compared to the drought resistant genotype "Dagdas", the drought sensitive genotype "SBVD 1-2" showed more membrane and chlorophyll damage, and higher levels of SH-groups during the drought stress. The results obtained in this study are not conclusive to explain the genotypical differences in resistance to drought regarding to antioxidative potential and related free radical damage, but can be a basis for further studies.