Putrescine maintains postharvest pitaya quality by regulating polyamine and reactive oxygen homeostasis and energy metabolism

This paper investigated the polyamine, energy, and effects on ROS of pitaya treated with different concentrations of Put (0, 2, 4, and 6 mM) during storage at 8 °C. The results showed that 4 mM Put inhibited the increase of relative conductivity and malondialdehyde and maintained high levels of total flavonoids and total phenols in the fruit. 4 mM Put treatment significantly increased arginase, arginine decarboxylase, ornithine decarboxylase, and S-adenosylmethionine decarboxylase activities. Inhibition of polyamine oxidase and diamine oxidase activity resulted. in elevated levels of putrescine and spermidine. 4 mM Put significantly increased the activities of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase, reduced the accumulation of superoxide anion and hydrogen peroxide. In addition, adenosine triphosphate, adenosine diphosphate, adenosine monophosphate content and EC were higher, as well as succinate dehydrogenase and cytochrome C oxidase, H + -ATPase, and Ca 2+ -ATPase activities, in the 4 mM Put-treatment as compared to the peel. In conclusion, Put-treatment can maintain pitaya postharvest quality by regulating polyamine, attenuating ROS damage and increasing energy levels in pitaya. • 4 mM Put was the most effective in maintaining the postharvest quality of pitaya. • 4 mM Put promotes polyamine metabolism. • 4 mM Put treatment resulted in a high energy state of pitaya peel during storage. • Put treatment triggered the defense response of pitaya ROS metabolic system.