Physiological Insights of Melatonin Hormone for Alleviation of Drought Stress in Rice

Drought stress significantly hampers crop growth and yield by negatively impacting various biochemical and physiological plant processes. This study aimed to assess drought tolerance in traditional rice varieties using Poly Ethylene Glycol 6000 (PEG 6000) and focused on the effectiveness of melatonin applied through both seed treatment and foliar spray in mitigating the effects of drought stress. The optimal drought screening conditions were determined at a PEG concentration of -4 bars. As the PEG concentration increased, key factors such as germination percentage, vigor index, root length, and shoot length decreased. This indicates that PEG can be a useful tool for early selection of drought tolerant rice varieties. Melatonin (N-acetyl-5-methoxytryptamine), known for alleviating abiotic stress, showed positive effects on seed germination at 200 ppm concentration. The study observed that stomatal closure is a natural response to drought stress, but melatonin application induced partial stomatal opening. Notably, a foliar spray of 100 ppm melatonin demonstrated better recovery from drought stress compared to the 200 ppm concentration. In conclusion, the research suggests that seed treatment with 200 ppm melatonin and foliar spraying with 100 ppm melatonin are the most effective approaches for reducing the adverse effects of drought stress in rice plants.