Mitigating Effect of Exogenous Melatonin on Salt and Drought Stress in Cyperus esculentus L. during the Tillering Stage

Drought and salt stress are important limiting factors that affect crop growth and yield. As a newly recognized plant hormone, melatonin can participate in the regulation of plant stress tolerance and enhance the tolerance of plants to adversity. In this study, the effects of melatonin (150 mu mol<middle dot>L-1) on agronomic traits, osmotic adjustment substances, antioxidant enzyme activities, and reactive oxygen species content in C. esculentus under different salt (0 and 200 mmol<middle dot>L-1 NaCl), drought (70% field capacity, 50% field capacity), and salt-drought (200 mmol<middle dot>L-1 NaCl + 50% field capacity) stress conditions were determined using a pot experiment. Spraying with 150 mu mol<middle dot>L-1 of melatonin effectively improved the plant height, number of blades, biomass, and root growth of C. esculentus seedlings under salt, drought, and combined stress. In addition, this treatment also increased the relative water content, superoxide dismutase, peroxidase, and catalase activities, and soluble sugar content of the blades and decreased the relative electroconductivity conductivity and proline, malondialdehyde, hydrogen peroxide, and superoxide anion contents. A comprehensive analysis showed that spraying the plants with exogenous melatonin could increase the activity of antioxidant enzymes and the accumulation of osmotic adjustment substances in C. esculentus blades under salt and drought stress, effectively remove excessive reactive oxygen species, alleviate oxidative damage, and enhance the ability of C. esculentus to resist salt and drought stress.