Enhancing drought tolerance in okra through melatonin application: A comprehensive study of physiological, biochemical and metabolic responses

As climate change intensifies, drought stress presents a critical challenge for horticultural crops like okra (Abelmoschus esculentus). The effectiveness of melatonin in reducing drought stress is investigated in this study. The treatments include: Absolute control (fully irrigated), control (drought), drought and seed treatment with 100 µM melatonin, drought and foliar spray of 100 µM melatonin, and drought stress with combined effect of seed treatment and foliar spray of 100 µM melatonin. Physiological parameters such as photosynthetic rate, stomatal conductance, transpiration rate, Fv/Fm ratio, and chlorophyll index were evaluated, alongside biochemical parameters including malondialdehyde, proline content, membrane stability index and antioxidant enzyme activities such as catalase and ascorbate peroxidase were quantified. Melatonin supplemented as seed treatment and foliar spray enhanced both physiological and biochemical parameters including antioxidant activity compared to drought control. Metabolite profiling identified bioactive compounds (mainly carbohydrates and amino acids) contributing to drought tolerance in okra. The results highlight that application of 100 µM melatonin via seed treatment and foliar spray enhances drought tolerance in okra, suggesting its potential to enhance crop resilience under water-deficit conditions.