Mitigating High Temperature Stress in Rice (Oryza sativa L.) with Osmoprotectant Foliar Sprays at Various Phenophases

Pot experiment was conducted to assess the effects of high-temperature stress on rice (Oryza sativa L.) and to identify effective mitigation strategies in kharif season (2023) in the Department of Agricultural Meteorology, Kerala Agricultural University in a factorial CRD layout. The rice variety Jyothi was exposed to high-temperature (HT) in a temperature monitored polyhouse to impart stress and ambient conditions for comparison with the stressed condition. The pots were exposed to high temperature stress in polyhouse at 3 stages: active tillering, heading and milking respectively. Four different treatments were administered as foliar sprays at three stages. Variations were observed in physiological, biochemical, and yield components across the different conditions and treatments. Plants exposed to the high temperature showed lower values of the physiological parameters and also in yield. Temperatures above 29°C during the milking stage reduced the yield and number of filled grains drastically. The external application of osmoprotectants proved effective in mitigating the adverse effects of high temperature. The treatment salicylic acid (400ppm) recorded the highest chlorophyll content and chlorophyll stability. With regards to the yield, highest yield was seen in the salicylic acid (400ppm) treated set of plants. Temperatures above 29°C during the milking stage reduced the yield and number of filled grains drastically.