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Aluminum (Al) toxicity is a major limiting factor for plant growth in acidic soils. Melatonin (MT) is involved in plant responses to various environmental stresses. In this study, the role of exogenous MT in alleviating Al toxicity was investigated in soybean (Glycine max L.). The results demonstrated that MT application alleviated Al-induced inhibition of root elongation, reduced Al accumulation in root tips, and mitigated oxidative damage and cell death in root tips. Under Al stress, MT treatment increased the activities of antioxidant enzymes (SOD, CAT, APX, and POD) and the contents of antioxidants (ASA and GSH) in root tips. Furthermore, Al stress significantly enhanced citrate secretion from soybean roots, while MT application further promoted citrate efflux under Al exposure. Under Al stress, MT treatment significantly increased citric acid levels in root tips by upregulating the expression of citrate synthase gene and downregulating the expression of aconitase gene. In addition, MT application significantly increased the expression of citrate transporter genes (GmMATE13 and GmMATE47) in root tips. Taken together, these findings suggest that MT enhances soybean tolerance to Al stress by activating the antioxidant defense system and promoting citrate secretion. This study provides a theoretical foundation for the application of MT to mitigate Al toxicity in plants.

来源平台：RUSSIAN JOURNAL OF PLANT PHYSIOLOGY