Melatonin in vegetable production: Unlocking growth, quality, and stress tolerance

Melatonin (N-acetyl-5-methoxytryptamine) has emerged as an important multifunctional molecule in vegetable crops due to its diverse roles in plant growth, development, stress tolerance, and postharvest preservation. Recent studies have demonstrated that melatonin regulates a wide range of physiological, biochemical, and molecular processes, including seed germination, root development, photosynthesis, nutrient uptake, flowering, and yield enhancement. Its strong antioxidant potential enables efficient scavenging of reactive oxygen species (ROS), thereby protecting plants against oxidative damage caused by abiotic stresses such as drought, salinity, temperature extremes, and heavy metal toxicity. Melatonin also interacts with major phytohormones, including auxins, abscisic acid, gibberellins, ethylene, salicylic acid, and jasmonic acid, contributing to coordinated regulation of plant growth and stress responses. In addition, melatonin enhances resistance against fungal, bacterial, and viral pathogens through activation of defence-related genes and antioxidant systems. Beyond stress mitigation, melatonin improves postharvest quality by delaying senescence, maintaining membrane stability, preserving chlorophyll content, and extending shelf life in highly perishable vegetables. This review comprehensively summarizes current knowledge on melatonin biosynthesis, distribution, mechanisms of action, physiological functions, and its role in biotic and abiotic stress management in vegetable crops. Furthermore, the review highlights recent advances, practical applications, and existing research gaps associated with melatonin use in sustainable vegetable production systems. Overall, melatonin represents a promising eco-friendly strategy for enhancing vegetable productivity, quality, and resilience under changing environmental conditions.