Low intensity white light-emitting diodes (LED) application to delay senescence and maintain quality of postharvest pakchoi (Brassica campestris L. ssp. chinensis (L.) Makino var. communis Tsen et Lee)

In this study, the effect of white LED irradiation on quality, antioxidant, chlorophyll-related enzyme activity and gene expression were evaluated in pakchoi. Results indicated that white LED irradiation (10 mu mol m(-2)s(-1)) significantly suppressed the changes in sensory evaluation, respiration rate, and malondialdehyde content, and also maintained higher chlorophyll and vitamin C content in harvested pakchoi stored at 20 degrees C. Furthermore, LED treatment maintained the levels of gene expression and enzyme activity of peroxidase, catalase, and ascorbate peroxidase, inhibited the activity and expression of several enzymes (chlorophyllase, chlorophyll-degrading peroxidase, Mg-dechelatase, pheophytinase) and chlorophyll-degrading genes (BrChlase1, BrChlase2, and BrPPH), and increased the expression of the chlorophyll synthetase gene, BrHEMAL Collectively, the results demonstrate that LED treatment represents an effective method for delaying senescence and maintaining the quality of pakchoi by enhancing the activity and relative gene expression level of antioxidant enzymes and regulating chlorophyll metabolism.