Effects of exogenous melatonin on seed germination and seedling growth of Elymus sibiricus under NaCl stress

To explore the alleviation effect of exogenous melatonin (MT) on Elymus sibiricus under NaCl stress and screen out the optimal MT concentration to promote seed germination and seedling growth of E. sibiricus. In this experiment, the national variety ‘Yajiang’ E. sibiricus was used as the test material to study the effects of concentrations of exogenous MT (50, 100, 300, 500, 800, and 1000 μmol·L^–1) on seed germination rate and seedling growth morphology and physiological characteristics of E. sibiricus under NaCl stress (100 mmol·L^–1). The results showed that the exogenous addition of concentrations of MT was able to alleviate the inhibitory effect of NaCl stress on E. sibiricus, and the comprehensive evaluation analysis showed that the exogenous addition of 100 μmol·L^–1 of MT had the best effect. Under this treatment, the germination rate, germination potential, germination index, and vigor index of E. sibiricus seeds were 12.7%, 61.3%, 37.3%, and 75.0%, respectively, higher than those with NaCl stress without addition. The root/shoot ratio of seedlings increased by 59.9%, and the peroxidase activity and soluble protein content increased by 75.1% and 153.4%, respectively. The malondialdehyde content decreased by 29.3%. These results indicateindicates that under NaCl stress, exogenous MT can enhance the antioxidant enzyme activity of E. sibiricus, remove excessive reactive oxygen species, and inhibit membrane lipid peroxidation, improving the NaCl tolerance of E. sibiricus seedlings. The results of this study provide a theoretical basis for establishing and optimizing the cultivation of ‘Yajiang’ E. sibiricus in a saline-alkali environment.