Plant melatonin: roles and regulatory mechanisms in plant growth, development, and responses to biotic and abiotic stresses

Melatonin, a key indoleamine compound intrinsic to life, is ubiquitously distributed across the plant kingdom in plants. As a plant growth regulator and biostimulant, melatonin plays a pivotal role in both increasing plant growth and bolstering resilience to stress. This review provides a comprehensive analysis of regulatory mechanisms plant growth and development and addresses biotic and abiotic stressors. We dissect the biosynthetic and metabolic pathways of melatonin in plants and elaborate on its roles in catalyzing plant growth, development, and antioxidant activities. Furthermore, our discussion delves into the ways in which melatonin manipulates plant morphology, physiology, redox systems, ion homeostasis, biomolecular content levels, and the expression of stress resistance genes or proteins. We additionally highlight its cooperative interaction with other endogenous hormones in mitigating the deleterious impacts of challenging environments. In essence, melatonin, as a multifunctional biological signaling molecule, offers the potential to increase crop yield even under adverse conditions by plant seed germination rates and promoting robust growth. Consequently, it as a compelling candidate for ecofriendly crop production strategies. This review is intended to serve as a theoretical guide to unravel the multifaceted regulatory mechanisms of melatonin in governing plant growth, development, and stress resistance.