Physiological, Biochemical, and Omics Mechanisms Underlying Melatonin‐Mediated Salinity Tolerance and Yield Stability in Adzuki Bean

) by 5.38% and the leaf area index (LAI) by 12.48% compared to SW. Furthermore, melatonin significantly enhanced the antioxidant defense system, with SOD, POD, and CAT activities increasing by 16.50%, 13.19%, and 14.19%, respectively, in the SM treatment. Additionally, melatonin promoted nitrogen assimilation and carbon metabolism, with NR, GS, and GOGAT activities increasing by up to 23.13%, alongside enhanced activities of enzymes related to sucrose metabolism. Integrated transcriptomic and metabolomic analysis revealed that melatonin significantly activated linoleic acid metabolism, arachidonic acid metabolism, and starch and sucrose metabolism pathways. Compared with SW, the SM treatment increased linoleic acid and arachidonic acid contents by 35.2% and 27.6%, respectively. Concurrently, key carbon metabolism genes, including INV, HK, GPI, and scrK, were significantly up-regulated by 31.2%-45.7%, promoting carbon flow redistribution and maintaining C-N metabolic homeostasis. Metabolite supplementation experiments further verified that linoleic acid enhances antioxidant capacity, and its synergistic application with melatonin further promotes plant growth. In conclusion, exogenous melatonin alleviates oxidative damage and metabolic disorders caused by salinity stress by enhancing antioxidant defense, regulating osmotic balance, and promoting nitrogen uptake and transport. Furthermore, melatonin synergistically regulates lipid signaling and energy metabolism with linoleic acid, thereby maintaining C-N metabolism coordination and stabilizing adzuki bean yield.