Melatonin's Physiological Functions in Plants

*Melatonin - The Hormone of Darkness and Its Therapeutic Potential and Perspectives*

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Pharmaceutica. 2020 In press

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**Chapter 7**

**Abstract**

nin in horticultural production.

**1. Introduction**

Review of Melatonin in

*Yanyan Yan, Qinghua Shi and Biao Gong*

Melatonin is an indoleamine, abundant in animals and plants, which has the functions of regulating circadian rhythm, improving immunity and anti-aging in animals, and is a good health care product beneficial to human health. Recent studies have shown that melatonin has physiological functions including regulating plant growth, promoting seed germination, controlling root development and delaying leaf senescence. The antioxidant properties of melatonin give it the ability to strengthen plants' resistance to stress. The comprehensive researches in recent years, involving five aspects of "the biosynthetic pathway of melatonin in plants, the melatonin in horticultural crops and its influencing factors, the roles of melatonin in the growth and development of horticultural crops, in the response to stress of horticultural crops, the signal transduction network of melatonin in regulating plant growth and the development and stress resistance," are reviewed in the present paper. The application of melatonin in horticulture production is also discussed, which can provide a theoretical reference for the application of melato-

**Keywords:** development, growth, horticultural crops, melatonin, stress tolerance

Melatonin, *N*-acetyl-5-methoxytryptamine, is an indole-like tryptamine. In 1958, Lerner et al. [1] extracted melatonin from the pineal gland of cattle and found that it was a kind hormone-like substance, which was widely involved in the growth and development regulation, as well as signal transduction, in animals. Before the 1990s, melatonin was recognized as an animal hormone. However, Balzer and Hardeland [2] successfully isolated and identified melatonin from single-celled algae, indicating the existence of natural melatonin in the plant kingdom. Since then, melatonin has become a research hotspot and received extensive attention from researchers in the field of plant and agricultural science. With the rapid development of material separation and identification technology, plant physiology and cell biology, molecular biology, sequencing technology and other research methods, scientists have conducted more comprehensive and in-depth studies on the synthesis pathway, concentration, distribution and biological function of melatonin in plants. Moreover, melatonin has a variety of regulatory effects in plants and has many benefits for human health. Therefore, the research on melatonin in horticultural crops is fast increasing, which is no less than that in model plants of *Arabidopsis thaliana*. Therefore, this review comprehensively and systematically introduced the research progress on melatonin and its function in horticultural

Horticultural Crops
