Protective role of antioxidant enzymes under high temperature stress.

An experiment was conducted to study the effect of high temperature stress on the antioxidant enzyme activity in five wheat genotypes viz., PBW 343, PBW 175, HDR-77, HD 2815 and HD 2865. There was significant increase in the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) in the late and very late planting and at all stages of plant growth, i.e., vegetative, anthesis and 15 days after anthesis (DAA), however glutathione reductase (GR) and peroxidase (POX) activity decreased under late and very late plantings compared to normal planting. In general HD 2815, HDR-77 showed relatively higher SOD, APX, GR, CAT and POX activity in the late plantings compared to PBW 343, PBW 175 and HD 2865. Significant reduction in chlorophyll content and increase in membrane injury index were observed in all genotypes with age, and also under late and very late sowings at all the stages of plant growth. However HD 2815 and HDR-77, which showed highest activity of various antioxidant enzymes under late and very late sowing also showed minimum reduction in chlorophyll content and lower membrane injury index, indicating the amelioration of high temperature stress induced oxidative stress by antioxidant enzymes. Various antioxidant enzymes showed positive correlation (r) with chlorophyll content and negative with membrane injury index at most of the stages in the five wheat genotypes.