Acetylsalicylic acid and salicylic acid alleviate postharvest leaf senescence in Chinese flowering cabbage (Brassica rapa var. parachinensis)

The leaves of ‘Ningxia Chinese flowering cabbage’ readily become yellow and senesce after harvest. To test the effects of acetylsalicylic acid (ASA) and salicylic acid (SA) on postharvest leafy vegetables, Chinese flowering cabbages were sprayed with 2 mmol L−1 ASA and 1.5 mmol L−1 SA, and stored at 15 °C. Compared with the controls, during storage, ASA- and SA-treated cabbages retained higher levels of total chlorophyll (Chl), Chl a, and Chl b, and lower activities of chlorophyllase, Mg dechelatase, pheophytinase, and Chl-degrading peroxidase, and had more intact chloroplasts. Furthermore, ASA and SA repressed respiration intensity, ethylene rate, the activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase, and ACC content, decreased reactive oxygen species (ROS) levels, and increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, phenylalanine ammonia lyase, cinnamate 4-hydroxylase, 4-coumarate-CoA ligase, chalcone synthase, chalcone isomerase, and cinnamyl alcohol dehydrogenase, promoting the accumulation of phenolics and flavonoids. Using principal component and hierarchical clustering analyses, leaf senescence was attributed to higher respiration, ethylene synthesis, and ROS levels, while the delay of senescence in treated cabbages resulted from the cooperation of ROS metabolism and the phenylpropanoid pathway. ASA and SA slowed leaf degreening and senescence. Between the two treatments, 2 mmol L−1 ASA was the most effective.