ABSTRACT
ABSTRACT: In recent years, the roles of melatonin in plants have become a research highlight. Evidences indicate that exogenously applied melatonin can improve the tolerance of plants to abiotic stresses. This chapter mainly focuses on the regulatory effects of melatonin against osmotic stress, such as drought, salinity, and freezing. Previous efforts have demonstrated that exogenous melatonin can promote seed germination and root rhizogenesis, and regulate plant growth and photosynthesis under osmotic stress. Overexpression of the melatonin biosynthetic genes increases melatonin levels in transgenic plants. The transgenic plants show enhanced tolerance to osmotic stresses. Melatonin also regulates many genes involved in plant hormone biosynthesis and metabolism, ion homeostasis, and ROS scavenging. Possible mechanisms of melatonin against osmotic stress are also discussed herein.
