**5. Role of melatonin in stress response of horticultural crops**

Large numbers of studies have shown that the endogenous melatonin of plants often changes greatly under the stimulation of stress factors, including light intensity, light quality, temperature, water and oxygen, as well as the stimulation of salinity, ultraviolet (UV-B), paraquat, diseases and insect pests, etc. At the same time, exogenous addition of melatonin or enhancement of plant endogenous melatonin synthesis, through gene editing technology, can improve the plant's resistance to adversity.
