Drought induced stress is one of the most significant environmental challenges. This study was designed to evaluate the effects of drought stress on crop yield and antioxidant systems during the vegetative period of wheat. The study was carried out in a greenhouse using factorial experiment based on complete randomized block design (RCBD) in three replications in Razi University in Iran from 2011 to 2012. In the pot experiment, water stress was applied at vegetative growth stage (soil moisture 50 ± 5% of field capacity from the stemming to flowering periods) and various bread wheat genotypes (‘Pishtaz’, ‘DN-11’, ‘Sivand’, and ‘Marvdasht’) were examined as the second factor. Results showed that drought stress at vegetative growth stage considerably decreased plant height and crop yield. Under drought stress, the lowest and highest reductions in crop yield were noted seen in ‘Marvdasht’ and ‘DN-11’, respectively. The occurrence of drought stress at the vegetative growth stage in the experiment significantly reduced soluble protein content and membrane stability index. While drought stress considerably increased superoxide dismutase (SOD), it had no effect on the catalase (CAT) and peroxidase (POD). The studied parameters suggested that drought resistance of ‘Pishtaz’ and ‘Marvdasht’ might be due to the enhanced activity of antioxidant enzymes and low lipid peroxidation. Finally, antioxidant enzyme responses were found to provide a beneficial tool for depicting drought tolerance in different wheat genotypes in arid and semiarid regions.
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