Physiological and Biochemical Responses of Different Rice (Oryza sativa L.) Genotypes under Terminal Heat Stress

Abstract

Rice is the staple food of more than 60% of the world’s population. It is very sensitive to heat stress during flowering and grain filling stages. Therefore, heat stress is an important constraint for rice productivity under changing climatic conditions. To evaluate the effect of terminal heat stress in different indica rice genotypes a field experiment was conducted in Norman E. Borlaug Crop Research Centre, G. B. Pant University of Agriculture and Technology, Pantnagar during kharif season 2010. These genotypes were transplanted in two blocks, one for control and another block for imposing heat stress by covering the block with low density polythene (LDPE) sheet supported by bamboo sticks. Both the entry ends were open for sufficient ventilation. The heat stress was given during flowering. Daily maximum and minimum temperature was recorded with the help of automatic thermometer inside the LDPE sheet tunnel. In the present investigation, it was found that flag leaf area, total plant dry matter, chlorophyll content, chlorophyll fluorescence and NR activity decreased under heat stress, while proline level significantly increased in all rice genotypes. A significant reduction in grain yield, 1000 grain weight, number of filled spikelet and percent spikelet fertility was recorded. It is evident from the present study that the terminal heat stress may pose severe threat to rice productivity under globally changing climatic conditions.