Functions of Endogenously Produced and Exogenously Applied Melatonin in Higher Plants.

Significance: The role of melatonin (MEL) in plants has gained significant relevance due to its involvement in a wide range of physiological functions, particularly in response mechanisms to both abiotic and biotic stresses. Recent Advances: Recent progress highlights the significance of the biosynthetic pathway of MEL in plants, which surpasses that of animals. The discovery of specific plant MEL receptors has revealed new signaling mechanisms. Studies also show that applying exogenous MEL offers benefits under stress conditions and helps maintain the organoleptic qualities of fruits and vegetables during postharvest storage. Critical Issues: This review explores MEL's biochemistry, emphasizing its dual role as both an antioxidant and a signaling molecule. It examines how MEL interacts with phytohormones, its role in regulating the metabolism of reactive oxygen and nitrogen species, and its influence on plant growth and stress tolerance. The potential of MEL-based biotechnological applications for enhancing crop resilience and postharvest quality is also discussed. Future Directions: Future research should prioritize molecular mechanisms, high-throughput approaches, and translational studies to bridge the gap between fundamental science and agricultural practices. MEL's role as a sustainable solution in agriculture offers exciting possibilities for addressing global food security challenges. Antioxid. Redox Signal. 43, 151-188.