Differential antioxidative response of tolerant and sensitive maize (Zea mays L.) genotypes to drought stress at reproductive stage.

The role of oxidative stress management was evaluated in two maize (Zea mays L.) genotypes - Parkash (drought-resistant) and Paras (drought-sensitive), subjected to drought stress during reproductive stage. Alterations in their antioxidant pools - glutathione (GSH) and ascorbic acid (AsA) combined with activities of enzymes glutathione reductase (GR), ascorbate peroxidase (APX), peroxidase (POX) and catalase (CAT) involved in defense against oxidative stress and stress parameters, namely chlorophyll (Chl), hydrogen peroxide (H2O2) and malondialdehyde (MDA) were investigated in flag leaves from silk emergence till maturity. The drought caused transient increase in GR, APX, POX and CAT activities in drought-tolerant genotype (Parkash) which decreased at later stages with the extended period of drought stress. However, in Paras, drought stress caused decrease in activities of GR and CAT from initial period of stress till the end of experiment, except for POX which showed slight increase in activity. A significant increase in GSH content was observed in Parkash till 35 days after silking (DAS), whereas in Paras, GSH content remained lower than irrigated till maturity. Parkash which had higher AsA and Chl contents, also showed lower H2O2 and MDA levels than Paras under drought stress conditions. However, at the later stages, decline in antioxidant enzyme activities in Parkash due to severe drought stress led to enhanced membrane damage, as revealed by the accumulation of MDA. Our data indicated that significant activation of antioxidant system in Parkash might be responsible for its drought-tolerant behavior under drought stress and helped it to cope with the stress up to a definite period. Thus, the results indicate that antioxidant status and lipid peroxidation in flag leaves can be used as indices of drought tolerance in maize plants and also as potential biochemical targets for the crop improvement programmes to develop drought-tolerant cultivars.