Abstract:Apple fruits of the ‘cv. Starkrimson’ were artificially wounded, dipped with sodium nitroprusside (SNP) as an exogenous donor of NO at 0.5 mmol/L for 5 minutes. To investigate the weight loss and disease index of apple fruits during healing by SNP treated, we analyzed the activities of key enzymes and content of products in phenylpropanoid metabolism, H2O2 content and peroxidase activity at wound sites, and explored its relevant physiological mechanism, so as to provide a method and theoretical basis for rapid postharvest healing of apple fruits. The results indicated that: (1) SNP treatment effectively reduced the weight loss and disease index of inoculated fruits with Penicillium expansum during healing, which were 40.2% and 31.4% lower than the control at the 5th day after healing. (2) The treatment significantly increased the activities of phenylalanine ammonia lyase, cinnamic acid4hydroxylase and cinnamyl alcohol dehydrogenase, the key enzymes of phenylpropanoid metabolism, and enhanced the contents of cinnamic acid, coffeic acid, ferulic acid, sinapic acid, total phenols, flavonoids, Pcoumaroyl alcohol, coniferyl alcohol, sinapyl alcohol and lignin at wound sites of fruits. SNP treatment also significantly raised H2O2 content and POD activity at wound sites of fruits. It was found that NO could promote the wound healing of apples by activating phenylpropanoid pathway, increasing H2O2 content and POD activity at wound sites.