Exogenous Abscisic Acid Modulates Stomatal Regulation and Antioxidant Defence Mechanisms in Rice (Oryza sativa L. cv. IR64) Under Induced Drought Stress

This study elucidates the protective role of exogenous abscisic acid (ABA) in mitigating drought stress responses in rice (Oryza sativa L. cv.IR64).Through controlled application of 4 ppm ABA and 10% PEG 6000-induced drought stress, we investigated physiological and molecular adaptations, including: Morphological modifications (29.4% reduction in plant height, 49.9% shorter roots), Oxidative stress markers (10.2-fold increase in HO, 7-fold higher MDA levels), Photosynthetic efficiency (39.5% chlorophyll reduction), Cellular integrity (44.7% elevated electrolyte leakage), Gene expression patterns of OsSLAC1, OsCatA and Mn-SOD.Notably, ABA application demonstrated significant protective effects: 35.4% reduction in oxidative damage, 28.7% improvement in membrane stability, 22.1% enhancement of photosynthetic capacity.Gene expression analysis revealed treatment-specific activation of the ABA-dependent OsSLAC1 pathway and differential regulation of antioxidant genes.These findings provide mechanistic insights into ABA-mediated drought tolerance, suggesting its potential as a protective agent against water deficit stress in rice cultivation.