Recent Progress on Melatonin-Induced Salinity Tolerance in Plants: An Overview

In this context, it is necessary to select and develop salt-tolerant genotypes that can grow in salty soils and have high yields, and formulate strategies which may enhance the plant survival under salinity stress. Melatonin (N-acetyl-5-methoxytryptamine) is an important biological hormone that provides resistance to abiotic stress conditions and can be secreted by plants. Melatonin concentration in plants varies depending on genotype, temperature and growth period. Increase in melatonin concentration is associated with increased SNAT and HIOMAT/ASMT enzyme activity. It plays an important role in gibberellic acid and abscisic acid biosynthesis during the germination and provides plant growth and development. Exogenous application of melatonin significantly alleviates chlorophyll degradation and stomatal closure caused by salt stress, improves photosynthesis and enhances plants' salt tolerance. Besides it significantly reduces the harmful effects of salinity by regulating plant physiology, improving plant morphology, photosynthesis and activities of antioxidant enzymes. The present review discusses the recent studies on the effect of melatonin on plant growth and physiology against salt stress that have important impacts on plant growth and development have been given according to the findings of various researches. It also highlights the mechanim/s of melatonin-induced salinity stress tolerance in plants.