International Journal of Plant & Soil Science

Tolerance strategies under water deficit conditions involve many physiological and biochemical responses which help crops to cope with drought stress. To study wheat response to stress, twenty Iranian wheat genotypes were evaluated in two separate field experiments during 2009-2010 growing season. Each experiment was conducted as randomized complete block design with three replications. The moisture level in one experiment was 100% field capacity while 45% field capacity was applied at the second experiment. Several biochemical (catalase, peroxidase, superoxide dismutase, ascorbate peroxidase and lipid peroxidation) and physiological indices (relative water content, relative water protection, stomatal resistance, chlorophyll and canopy temperature depression) were measured. Drought stress increased activities of lipid peroxidation, relative water protection, relative water content, stomatal resistance, chlorophyll and canopy temperature depression significantly at the pre-anthesis stage (Z34). Higher antioxidant activities, relative water content, relative water protection, chlorophyll, stomatal resistance and canopy temperature depression, and lower lipid peroxidation were observed in tolerant genotypes. The results demonstrated positive correlation of antioxidants with relative water content, relative water protection, chlorophyll, stomatal resistance and canopy temperature depression, and negative correlation with lipid peroxidation. Relative water protection and superoxide dismutase were suitable indices for screening and classifying tolerant genotypes. The results suggested that a combination of traits such as higher antioxidant activity, stomatal resistance and water retention capacity lead to wheat drought tolerance and the cultivars Kavir and Bahar were the most and least tolerant genotypes, respectively.