Physiological Effect of Melatonin on Plants.

Melatonin is a well-known agent that plays multiple roles in animals, however, its possible functions in plants is less clear. Several studies have reported its role as an antioxidant especially in plants under various kinds of stress. In the present study, we studied the effect of melatonin (N-acetyl-5-methoxytryptamine) on soybean, cucumber and tomato plants. There were 6 groups in Soybean; Control, 50um, 100um and 200um foliar application and 50um and 100um primed group. Cucumber and tomato seeds had 3 groups, control, 50um and 100um primed seeds. The growth effect was measured in terms of germination and height of the plant. The physiological effect of the treatment was measured on chlorophyll and stomatal conductance in the growing soybean plants. The maximum number of seeds germinated in seeds primed with 50um melatonin in soybean and tomato, whereas, cucumber highest germination rate was found in 100um. In stomatal conductance of primed group, soybean plants the control was the highest in week 1, whereas by week 3, there was no significant difference between the groups. In foliar treatment, by week 3, both 100um (1,922 m^-2/s mol-1) and 200um (1,956 m^-2/s mol-1) stomatal readings were higher when compared to control (1,433 m^-2/s mol-1). We can conclude that melatonin treated plants offers protective measurements in terms of stomatal opening, chlorophyll content and might help induce germination rate, however, we need further studies to confirm.