Effects of 2,4-Epibrassinolide Treatment on Quality, Physiology and Biochemistry of Pakchoi (Brassica chinensis L.) during Storage at Different Temperatures

‘Shanghaiqing’ was sprayed with 1.0 mg/L EBR solution and stored at 20 ℃ and 2 ℃ respectively to study the effects of EBR on the quality, physiology and biochemistry of pakchoi after postharvest. The results showed that EBR treatment could inhibit the increase of L^* and the decrease of hue angle H of pakchoi during storage at 2 ℃ and 20 ℃, and slow down the decrease of total chlorophyll, chlorophyll a and chlorophyll b content. At the end of storage, the total chlorophyll content of pakchoi was 5.57% and 46.25% higher than that of the control at 2 ℃ and 20 ℃ respectively. EBR treatment significantly inhibited the increase of chlorophyll degradation related enzymes (chlorophyllase, Mg-dechelatase and pheophytin pheophorbide hydrolase) of pakchoi during storage at 2 ℃ and 20 ℃, the activities of the three enzymes were more than 28% lower than those of the control at the end of storage. EBR treatment weakened the respiratory intensity of pakchoi, inhibited the decrease of the activities of antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase), decreased the activity of membrane lipid peroxidase (peroxidase and lipoxygenase), and inhibited the increase of superoxide anion, hydrogen peroxide and malondialdehyde content of pakchoi during storage at 2 ℃ and 20 ℃. At the end of storage, the malondialdehyde content of EBR treatment decreased by 8.91% and 19.18%, respectively, compared with the control. The results showed that pakchoi stored at 2 ℃ could maintain better quality and physiological and biochemical indexes than storage at 20 ℃. 1.0 mg/L EBR treatment could effectively delay the yellowing of pakchoi during storage at 2 ℃ and 20 ℃, and reduce the decline of quality and physiology, among them, the effect on the indexes of pakchoi stored at 20 ℃ was more obvious.