Effect Of Nitric Oxide Treatment On Preservation In Kiwifruit And Its Involved Physiological Mechanism

In order to understand effect of nitric oxide treatment on postharvest kiwifruit and its involved physiological mechanism, the effects of nitric oxide treatment on quality, ethanol metabolism, disease resistance and energy metabolism in kiwifruits (Actinidia deliciosa.cv.Bruno) were investigated in this paper. After harvested, the fruits were dipped in 0.1 mmol·L-1,0.2 mmol·L-1 sodium nitroprusside (SNP) or water (as control) and then stored at room temperature (about 20℃). The main results were as follows:1. Nitric oxide treatment effectively delayed the decrease of the firmness, and inhibited the increase rate of soluble solid content (SSC) and the decrease rate of titratable acid (TA), and also decreased the loss of vitamin C content in kiwifruit during storage. The results showed that nitric oxide treatment delayed the ripening process, which in turn maintained the quality of kiwifruit during storage.2. Nitric oxide treatment decreased the activities of ethanol metabolism enzymes, including pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), and lactic dehydrogenase (LDH). Compared to the 0.1 mmol·L-1 SNP treatment,0.2 mmol·L-1 SNP treatment inhibited the accumulation of ethanol and aldehyde more apparently. The results showed that nitric oxide treatment decreased the accumulation of ethanol and aldehyde according to impacting pyruvate content and the activities of ethanol metabolism enzymes which contributed to inhibition of the bad flavor.3.0.1 mmol·L-1 SNP and 0.2 mmol·L-1 SNP treatment enhanced the activities of defense enzymes, including polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL), chitinase (CHT), P-1,3-glucanase (GLU) and the gene expression of POD, PAL and CHT. NO treatment also increased the contents of lignin, hydroxyproline-rich glycoprotein (HRGP) and phenol. The results showed that nitric oxide treatment enhanced the abilities of disease-resistant attributed increases in both of the activities of defense enzymes and the contents of defense substances.4. ATP, ADP and AMP contents, and energy charge decreased more slowly with 0.1 mmol·L-1 SNP or 0.2 mmol·L-1 SNP treatment. The treatment enhanced the activities of respiratory metabolism enzymes in chondriosome, including succinodehydrogenase (SDH), cytochrome oxidase (CCO), H+-ATPase and Ca2+-ATPase. Thus, nitric oxide treatment enhanced the activities of respiratory metabolism to maintain the high energy charge.