[Effects of exogenous melatonin on antioxidant capacity and nutrient uptake of Lolium perenne and Medicago sativa under drought stress].

To explore the effects of exogenous melatonin on antioxidant capacity and nutrient uptake of plants under drought stress, we used and potted seedlings for foliar spraying and root application of 100 μmol·L melatonin, respectively. We measured the biomass, malondialdehyde (MDA) content, relative conductivity, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities, as well as nutrient contents (organic carbon, total nitrogen, total phosphorus) under drought stress. The results showed that the biomass of and decreased significantly under drought stress, and that external melatonin application could effectively alleviate the inhibitory effect of drought stress on and . Foliar spray and root application of melatonin under drought stress enhanced biomass by 14.5% and 29.6%, and that of by 36.6% and 49.1%, respectively. The SOD and POD activities in and SOD activity in significantly decreased under drought stress, and exogenous melatonin significantly increased SOD, POD and CAT activities in and , reduced the accumulation of MDA in leaves, caused a significant decrease in the relative conductivity of leaves, and significantly increased antioxidant capacity. Drought stress and exogenous melatonin did not affect organic carbon content of and Under drought stress, the contents of N and P in leaves and roots and the content of N in roots decreased, while the application of melatonin increased the contents of N and P in roots and leaves of and , indicating that melatonin could regulate the nutrient absorption of and under drought stress. In conclusion, the melatonin application not only improved the antioxidant capacity of plants, but also regulated nutrient uptake to enhance plant resilience to drought stress. Foliar spraying of melatonin was more effective than root application.