Exogenous application of melatonin improves salt tolerance of sugar beet (Beta vulgaris L.) seedlings

Salt stress usually results in severe physiological damage to plants. Melatonin (N-acetyl-5-methoxytryptamine) is an important growth regulator that adapts plants to abiotic stress. The present study evaluated the role of melatonin application on inducing salt tolerance in sugar beet (Beta vulgaris L.). The protective role of melatonin (0, 30, 60, and 90 mu M) was examined by measuring leaf photosynthetic characteristics, antioxidant system, and osmotic adjustment substances of sugar beet seedlings under salt (300 mM Na+) and non-salt stresses. The results showed that salt stress resulted in significantly reduced biomass, reduced photochemical activity of photosystem II (PSII), and evoked the production of reactive oxygen species (ROS). In contrast, the application of melatonin significantly increased antioxidant enzyme activities (SOD, POD, and CAT) under salt stress, reduced ROS accumulation (MDA and O-2 center dot(-)), and enhanced photosynthesis in seedlings. There was no significant difference in the above indicators of melatonin pretreatment under control condition (non-salinized). On day 1 of stress application, the concentration of sucrose decreased significantly, and the concentration of proline and H2O2 increased significantly under melatonin treatment. On day 7, soluble sugar and betaine concentrations increased significantly. Current research speculates that melatonin enhances cellular energy metabolism and may be involved in activating the antioxidant system to eliminate ROS. In conclusion, these results indicated that the application of 60 mu M melatonin could act as a feasible way to alleviate the salt stress in sugar beet production.

Automated summary

This study evaluated the role of melatonin in inducing salt tolerance in sugar beet seedlings. The findings showed that melatonin application increased antioxidant enzyme activities, reduced ROS accumulation, and enhanced photosynthesis under salt stress, alleviating the negative effects of salt stress on sugar beet production.