differential antioxidative responses to water deficit among four barley (hordeum vulgare l.) genotypes

future climate changes are expected to increase risks of drought, which already represent the most common stress factor for stable barley (hordeum vulgare l.) production in iran. up to now, extensive research projects have been done to study effects of drought stress on the antioxidant enzyme activity. while there is a few works of such studies on the field condition. in order to study of water deficit effects on the antioxidant enzymes activities as a secondary stress, we evaluate the effects of mild and severe drought stress on activities of antioxidative enzymes including superoxide dismutases, ascorbate peroxidase, catalase and peroxidase, among four barley genotypes, differing in the capacity to maintain the grain yield under drought condition during beginning on anthesis, kernel watery ripe and late milk stages under field condition. results showed that drought increased the activity of antioxidant enzymes in all genotypes. at beginning of anthesis, pox activity of q22 was higher than it in other genotypes ( p<0.01). accordingly grain yield under drought condition q22 is more tolerant than others. therefore it seems pox has major role in reactive oxygen species (ros) detoxifications under drought condition and can be use as biological marker for selection of tolerant barley genotypes at breeding programs.