ABSTRACT
Agricultural crop production is significantly decreased by soil salinity and extreme environmental stress, which interfere with normal plant growth, cellular ion homeostasis, and metabolic pathways. Melatonin (MT), a versatile molecule found in mammals and plants, plays a crucial role in in plant defence against salt stress. MT is a dynamic molecule in plants that regulates various physiological and molecular functions. The MT-mediated responses include leaf senescence, tolerance of abiotic and biotic stressors, and post-harvest quality enhancement such as anthocyanin production. MT significantly enhances antioxidant systems during salt stress as a free radical scavenger and antioxidant. These functions boost photosynthesis and ion homeostasis while also triggering a cascade of downstream signals like hormones, nitric oxide, and polyamine metabolism. Plant salt stress tolerance was reported to be improved by increasing endogenous levels in diverse crop species. In salt-stressed plants, MT improved antioxidant capacity, ion homeostasis, photosynthetic capacity, and the control of ROS (reactive oxygen species), nitric oxide, hormone, and polyamine metabolism. MT is also involved in regulating gene expression in response to salt stress. In this chapter, we review recent literature and summarize the biochemical and molecular regulation of MT in response to salt stress in plants.
