Thriving against the odds: Unveiling the role of melatonin in Okra germination and seedling traits under PEG-induced osmotic stress

Altered environmental conditions subject plants to abiotic stresses like salinity, drought, temperature fluctuations (heat and cold) and exposure to heavy metals. Frequent stresses prompt the plant defense system to consistently adapt. Biostimulants assist plants in refining their defense strategies, allowing more effective responses to the changing environment and challenges. Melatonin, a neurohormone and antioxidant in mammals, has extended its presence to the plant domain due to its pervasive nature as a signaling molecule. Melatonin acts as a bio-stimulatory molecule in confronting stress in plants by regulating its growth and development. The present study attempts to comprehend the role of melatonin in combating drought stress. Okra genotypes namely, CO 4, Arka Anamika, Arka Abhay and Arka Nikita were subjected to PEG-induced osmotic stress (15 % PEG) in Petri plates supplemented with different doses of melatonin (50, 100, 150, 200, 250 µM). The seedling response varied with respect to genotypes in a dose-dependent manner. Among the genotypes, Arka Anamika performed better followed by Arka Nikita in terms of seedlings traits recorded. Higher concentrations of melatonin exhibited an inhibitory effect on seed germination and seedling growth parameters. However, priming okra seeds with 100 µM of melatonin showed promising results in mitigating the adverse effect of osmotic stress by promoting seed germination and seedling characteristics.