Madan, ShashiDommalapati, Sudhakara Rao2017-06-032017-06-032016http://krishikosh.egranth.ac.in/handle/1/5810014741The present investigation was conducted to study the effect of drought stress on antioxidant and proline metabolism in leaves and developing grains of two wheat varieties viz. WH 1105 and WH 1025. Drought stress was imposed by giving pre-sowing irrigation only and samples were taken at seven days interval from 7th to 28th days after anthesis. The results showed that during grain development, activities of antioxidant enzymes viz. superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase increased more in WH 1025 under drought stress than WH 1105. Antioxidant metabolites such as ascorbate, glutathione, proline and hydrogen peroxide content increased under drought stress in leaves and developing grains while the carotenoid content decreased. The enhancement of antioxidant metabolites was also reflected in concomitant enhancement of total antioxidant activity. Isozyme pattern of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase altered under drought stress with enhanced intensities in leaves and developing grains from 7th to 28th days after anthesis. Alteration in proline level under stress was due to changes in the activities of enzymes involved in proline metabolism. Proline synthesizing enzymes such as Δ1 pyrroline-5-carboxylate synthetase and Δ1 pyrroline-5-carboxylate reductase were also increased under drought stress; however proline degrading enzyme, proline oxidase activity decreased. Physiological parameters related to flag leaf membrane injury like lipoxygenase, malondialdehyde increased while leaf membrane stability, leaf lipids and total soluble protein content decreased under drought stress. Physiological parameters such as relative water content, osmotic potential, chlorophyll content and chlorophyll fluorescence gradually decreased under drought stress while canopy temperature increased. Quality parameters like grain appearance, hectolitre weight, grain hardness, crude fibre, total sugars and starch content decreased under drought stress, but sedimentation value, crude protein and gluten content increased. Phenological parameters like days to heading, days to anthesis, days to maturity and grain filling duration declined under drought stress. Yield attributes such as grain number per spike, grain weight per spike, test weight and grain yield per square meter decreased under the influence of drought stress. The reduction in physiological, biochemical, yield and grain quality traits was found to be more pronounced in WH 1105 in comparison to WH 1025. Drought susceptible index found to be less in WH 1025 than WH 1105.enDrought stress in wheat, Developing grains, Antioxidant enzymes and metabolites, Antioxidant isozymes, Proline metabolizing enzymes, Physiological parameters quality, Phenological parameters and yield attributesThesis