Effect of high doses of selenate application on melatonin synthesis, plant growth, sugar content, and reutilization efficiency of nutrition in sweet cherry

Purpose: Root application of low-dose selenate does not significantly influence the melatonin content in potted sweet cherry leaves. We aimed to investigate the effects of high doses of selenate on sweet cherry plants to clarify the physiological and biochemical aspects of adaptive stress. Methods: : Different doses of 5-methoxytryptophan was foliar applied on the long branch leaves of the ‘Russia No. 8’, and the potted and field grown sweet cherry plants were treated with 0, 48, 96, 144, and 196 mg/plant. The substance content and enzyme activity involved in tryptophan metabolism were detected and the growth parameters were detected. The C, N, Se, sugar, and soluble protein contentsin mature, old, and fallen leaves in August, and in yong leaves in March of the following year. Results: : 15 mg/L of 5-methoxytryptophan significantly increased leaf melatonin content. Selenate significantly increased the melatonin content only at a dose of 96 mg/plant. Doses lower than 96 mg/plant increased plant growth parameters, whereas higher doses decreased plant growth parameter. Different leaf ages of sorbitol, amylaceum, fructose, saccharose, rhamnose, and maltose content was influenced by different Se doses treatments. With an increase in the Se dose, the leaf nitrogen content increased, and the carbon content was influenced slightly in field-cultivated trees. Conclusion: Leaf Se content was mainly distributed in mature leaves in response to low doses of Se and in old leaves in response to high doses of Se; The neat year, different Se dose also influence the leaf nutrition and sugar contents.