Physiology and productivity of rice crop influenced by drought stress induced at different developmental stages
Rice is sensitive to moisture stress and in view of the water scarcity in the coming years, it is imperative to evaluate the performance of rice cultivar under moisture deficit. The present study aimed to evaluate the physiological responses of two rice cultivars under drought stress induced at panicle initiation and soft dough stages. The seeds of BAS-385 and KS-282 were soaked in ABA (10-6 M) prior to sowing. Foliar application of ABA (10-6 M) was made at tillering stage, 40 days after sowing (40 DAS) in both cultivars. Drought stress was induced at panicle initiation (PI) (65 DAS) and soft dough (SD) (105 DAS) stages with re-watering at incipient wilting (12% soil moisture). Drought induced significant decrease in endogenous level of IAA, GA, sugar and protein contents in leaves at SD stage, while ABA and proline contents increased significantly as compared to control. In grains, drought induced decreases in IAA, sugar and protein content were greater at PI stage in both cultivars. Stomatal resistance was significantly increased in flag and penultimate leaves at PI stage. ABA treatments ameliorated the adverse effects of drought stress for most of the physiological parameters but were ineffective to restore the drought-induced decrease in GA content. On-rewatering, the recovery of prestressed plants was significantly enhanced under ABA seed soaking and foliar spray treatments as compared to drought alone. It is inferred that the mechanism of ABA-induced tolerance to drought stress appears to be involved in maintenance of water budget by decreasing GA, increasing stomatal resistance and by osmoregulation as observed by increase in proline accumulation, and enhanced grain filling to bring early maturity in rice over control.
Key words: Drought stress, rice cultivars, panicle initiation, soft dough.