Drought stress is a major environmental factor limiting crop growth and productivity. Hydrogen peroxide (H₂O₂) plays an essential role during stress response by acting as a signal molecule that activates multiple stress tolerance mechanisms. In this study, the effects of H₂O₂ on agronomic traits were studied in rice (Oryza sativa L.) cv. Khao Dawk Mali 105 (KDML 105) was subjected to drought stress. H₂O₂ was applied by either seed priming or foliar application method with a concentration of 1, 5, and 15 mmol/L. The results showed that both seed priming and foliar application with H₂O₂ improved some yield components. The tiller numbers, number of panicles, number of filled grains, filled grain weight, and harvest index were improved approximately 1.13, 1.04, 1.23, 1.21, and 1.1 times compared to the untreated plants. Foliar application, however, helps the plant by reducing yield loss as indicated by a 0.5-time reduction in the number of unfilled grain and lower unfilled grain weight. It was suggested that 5 mmol/L H₂O₂ was the most effective concentration to alleviate the effect of drought stress during the reproductive stage in rice.

Drought stress is a major factor limiting crop growth and yield. Hydrogen peroxide (H2O2) is known as a signalling molecule in the plant cell in which activates multiple physiological changes that play essential roles in tolerance mechanism. This study investigated the effects of seed priming with H2O2 on growth, some physiological characteristics and antioxidant enzyme activities in rice seedling under drought stress. Rice (Oryza sativa L.) cv. Khao Dawk Mali 105 seeds were primed with 0 (distilled water), 1, 5, 10, and 15 mM H2O2 and grown for 21 days. The seedlings were subjected to drought stress by withholding water for 7 days. The results showed that priming with low concentrations of H2O2 improved plant growth and biomass as well as relative water content, malondialdehyde content, electrolyte leakage. Priming with H2O2, however, had no beneficial effect on chlorophyll content, proline and leaf total soluble sugar. Seed priming with appropriate levels of H2O2 also enhanced antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX). It is concluded that seed priming with 2-10 mM H2O2, is beneficial for enhancing drought tolerance in rice seedling by increasing antioxidant capacity, which in turn reduces oxidative stress and damages to the cellular components.