Red light-emitting diode irradiation delays the senescence of postharvest pakchoi through promoting antioxidant capacity and regulating ascorbate-glutathione cycle

Suitable light-emitting diode irradiation is a potential strategy for extending the shelf life of postharvest vegetables and fruit. In the present study, we aimed to investigate the potential mechanism by which red light-emitting diode (RL) irradiation regulates senescence in pakchoi by treating the samples with RL, lycorine (an inhibitor of L-galactono-1,4-lactone dehydrogenase enzyme involved in ascorbic acid biosynthesis), and RL combined with lycorine. The results indicated that RL irradiation maintained the chlorophyll content of pakchoi leaf. This treatment also increased the contents of ascorbate acid, glutathione, and ascorbate acid / docosahexaenoic acid and glutathione / glutathione disulfide ratios in pakchoi, reflecting a relatively stable cellular redox state. This could be mainly explained by the improved activities of L-galactono-1,4-lactone dehydrogenase and key enzymes involved in the ascorbate acid-glutathione cycle (ascorbate peroxidase, dehydroascorbate reductase, and gluathione reductase) and upregulated relative expression of the corresponding genes in the treated pakchoi. In addition, RL irradiation promoted the activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase), efficiently scavenged reactive oxygen species, and reduced malondialdehyde content in pakchoi. However, the positive effects of RL irradiation were negated when combined with LYC for the treatment of pakchoi. Therefore, RL irradiation may promote ascorbate acid biosynthesis and stimulate the AsA-GSH cycle to help maintain reactive oxygen species homeostasis, which contribute to the alleviation of postharvest senescence in pakchoi. •Red light treatment delayed yellowing and quality deterioration of pakchoi.•Red light increased ascorbic acid (AsA) biosynthesis in pakchoi.•Quality deterioration of pakchoi was accelerated by AsA biosynthesis inhibitor.•Red light stimulated AsA-GSH cycle for maintaining ROS homeostasis of pakchoi.