Exogenous melatonin alleviates damage from drought stress in Brassica napus L. (rapeseed) seedlings

This study investigated the ability of exogenous melatonin (MT) to alleviate drought stress in Brassica napus L. (rapeseed) seedlings. Seedling traits under control condition, drought stress, and drought stress with exogenous MT were evaluated. The results indicated that 0.05 mmol/L exogenous MT had the greatest protective effect against simulated drought stress. Exogenous MT alleviated the seedling growth inhibition under drought stress and significantly increased the leaf area and fresh and dry weights of roots and shoots compared to stress conditions lacking MT. In addition, although the hydrogen peroxide (H2O2) content increased under drought stress, it was decreased by exogenous MT. Moreover, antioxidant enzyme activities were increased in response to drought stress, and the activities of catalase, ascorbate peroxidase, and peroxidase were significantly enhanced by exogenous MT. The results also showed that solute accumulation under stress was enhanced with exogenous MT through increases in the contents of soluble sugars and proteins. These results suggest that exogenous MT can alleviate the negative effects of drought stress and improve the growth of seedlings. The findings indicate that MT possesses antioxidative, osmotic activity-adjusting, and growth-inducing properties, thus making it beneficial for drought acclimatization.