Shankhdhar, DeeptiMaheshwari, Akshita2019-07-302019-07-302019-07http://krishikosh.egranth.ac.in/handle/1/5810117828Rice is a staple food crop in global food system fulfilling the energy requirement of major part of world population. It is very sensitive to environmental factors such as temperature, light, drought etc. during critical stages of growth, such as flowering and seed development. High temperature can irreversibly damage the rice grain quality, yield and plant processes. Auxin plays a prominent role to mitigate the high temperature stress effects on spikelet fertility and yield attributes. A research investigation was carried out to understand the morpho-physiological and biochemical changes and effect of auxin application under high temperature conditions in N. E. Bourlog crop research center, Pantnagar during kharif season 2018. Heat treatment was given to different rice genotypes during flowering by making a polythene tunnel in one block which traps heat and other block kept open as control. Auxin treatment as 10 ppm IBA was given to one of the replication at anthesis. Among 30 genotypes only nine genotypes, IET 26803, IET 26480, IET26477, IET 26478, PR-124, IET 25713, IET 26806, IET 26794 and IET 26763 were selected for the further research work on the basis of grain yield and harvest index. Daily maximum and minimum temperature was recorded using automatic thermometer installed inside the tunnel. Parameters such as plant height, tiller number, total dry matter, leaf area, chlorophyll content, chlorophyll fluroscence, stem weight primary and secondary branching per panicle, panicle weight, number of filled grains per panicle, number of spikelet, spikelet fertility, thousand grain weight, grain yield, harvest index, carbohydrate, protein, amylose, germination potential of harvested seeds etc were recorded. It was found that chlorophyll content, leaf weight, stem weight and TDM reduced at flowering. At maturity, there was a decrease in shoot weight, TDM, primary and secondary branching per panicle, panicle weight, number of filled grains per panicle, spikelet fertility, grain yield, harvest index, germination potential of the seeds produced, carbohydrates and amylose content due to high temperature which was significantly enhanced by exogenous application of auxin in different rice genotypes. Physiological and biochemical analysis revealed that the carotenoid content superoxide radical accumulation increased in some genotypes. Genetic diversity is responsible for the stress effects and stress mitigation in the crop as different genotypes from diverse backgrounds showed varied results since out of nine genotypes IET 26806, IET 26763 and IET 26477 were found to be tolerant while PR-124, IET 26803 and IET 26480 were sensitive to high temperature in terms of spikelet fertility per panicle, grain yield per unit area, germination potential of harvested seeds and superoxide radical accumulation.ennullThesis