The effect of exogenous 24‐epibrassinolide pretreatment on the quality, antioxidant capacity, and postharvest life of wucai (Brassica campestris L.)

The quality of green leafy vegetables is easily lost during the postharvest period. The effect of exogenous 24‐epibrassinolide (EBR) pretreatment on the quality of wucai was evaluated in the present study. Wucai plants were sprayed twice with 0.1 μM EBR before harvesting. Two storage temperatures were tested: 25°C and 4°C. At 4°C, EBR pretreatment significantly delayed the degradation of the pigment and plant water loss. Furthermore, we measured the activity of key enzymes of the ascorbic acid (AsA)‐glutathione (GSH) cycle, the content of the main metabolites, and the expression of the AsA metabolism‐related genes in leaves. The results indicated that all three plants showed stronger antioxidant capacity after EBR pretreatment. At 4°C and 25°C, the storage time of wucai was 20 days and 7 days after EBR treatment, while the samples could be stored for 14 days and 4 days without EBR treatment application, respectively. At 4°C, the nutritional properties of wucai pretreated with EBR, such as total free amino acids, total soluble sugar, and cellulose contents, were higher than those of the control, while the content of nitrite and lignin was lower than that of the control. Hence, EBR pretreatment was able to enhance the antioxidant capacity of wucai, maintain normal leaf color and shape during storage, and delay the decline of nutritional properties; therefore, EBR pretreatment has potential commercial value for prolonging the market life of wucai.