Phytomelatonin As an Element of the Plant Hormonal System

Melatonin (N-acetyl-5-methoxytryptamine), an animal hormone, antioxidant, and regulatory molecule, is attracting increasing attention from biologists. Melatonin, discovered in plants in 1995 and later named phytomelatonin (PMT), regulates many stages of plant ontogenesis, from seed germination to the aging process. PMT is one of the most powerful plant cell antioxidants. Numerous experimental data show that PMT increases plant resistance under conditions of both abiotic and biotic stress. In the regulation of physiological processes, it interacts with almost all currently known phytohormones. The biosynthesis of PMT and its multifunctional activity have now been studied quite well; the first receptor and some components of its signaling chain have been discovered. All this allows us to consider PMT a new plant hormone.