Study On Effect And Mechanism Of NO Regulation On Respiratory Metabolism In Cottony Softening Of Harvested Wax Apple Fruit

Wax apple(Syzygium samarangenese[Blume]Merrill&L.M.Perry)fruit is rich in nutrition and unique in flavor.However,the vigorous physiological metabolism of harvested wax apple lead to cottony softening,thus resulting in poor quality and loss of commercial value.This study selects Taiwan honey campanula wax apple fruit as experimental materials to explore the effect of Nitric oxide(NO)treatment on cottony softening of harvested wax apple fruit and to investigate the effect of NO regulation of respiratory metabolism on the postharvest cottony softening deterioration and its mechanism,to provide a theoretical basis for postharvest wax apple fruits fresh-keeping technology.The main results of this study are as follows:1.Wax apple treated with the concentration of 10 μL/L and 0 μL/L(control)NO on the harvested wax apple.To study the effects of NO treatment on hardness,cottony softening index,weight loss rate,titratable acid content,total sugar content,and soluble solids content of postharvest wax apple fruit during storage.The results show that the pulp hardness gradually decreases,cottony softening index,the weight loss rate continues to increase,the content of titrable acid content continues to decrease,and the total sugar content and soluble solids content increase first and then decrease.Compared with the control group,the NO treatment can inhibit the increase of fruit weight loss rate,slow down the decrease of fruit firmness,delay the expansion of fruit cottony softening index,and slow down the decrease of soluble solids,total sugar content and titratable acid content.It can be concluded that NO treatment can delay the senescence and softening process of wax apple mist fruit,improve fruit storability and maintain better fruit quality2.By analyzing and measuring the changes of key enzymes and metabolites in the glycolysis pathway tricarboxylic acid cycle pathway,pentose phosphate pathway and respiratory chain related enzyme activities and pyridine nucleotides during storage,explore NO treatment Effects on the respiratory metabolism of postharvest wax apple fruit.The results showed that during the postharvest storage period,the respiration rate of wax apple fruit decreased overall,the activity of fructophosphate kinase first increased and then decreased,the activity of pyruvate kinase showed a downward trend,the activity of hexose phosphate isomerase generally showed a downward trend,and the pyruvate content showed Declining trend,pyruvate dehydrogenase activity increased,citrate synthase activity decreased,α-ketoglutarate dehydrogenase activity was increasing,succinate dehydrogenase activity showed a downward trend during storage,citric acid and fumar acid content is in a downward trend,the activities of 6-phosphate glucose dehydrogenase and 6-phosphate gluconate dehydrogenase are increasing first and then decreasing,the activities of cytochrome C oxidase and ascorbic acid oxidase are increasing,NAD kinase is increasing first and then decreasing Trend,NAD,NADH,NADP and NADPH are in a downward trend.NO treatment can inhibit the respiratory intensity of postharvest wax apple fruit,and inhibit phosphofructose kinase,pyruvate kinase,hexose phosphate isomerase,pyruvate dehydrogenase,citrate synthase,α-ketoglutarate dehydrogenase,The activities of succinate dehydrogenase and glucose 6-phosphate dehydrogenase and 6-phosphate gluconate dehydrogenase increase the activity of cytochrome C oxidase,ascorbate oxidase and NAD kinase.NO treatment can keep the NAD,The content of NADH maintains a high content of NADP and NADPH.It shows that NO treatment can affect the activity of key enzymes and related metabolites in the respiratory metabolism pathway to affect the respiration rate and respiratory metabolism of postharvest wax apple fruit,affect the cottony softening index of the fruit and delay the senescence of the fruit.3.Analyze and determine the changes of soluble sugar and various organic acid contents during the storage of wax apple fruit.The results showed that during storage,the content of fructose and glucose increased first and then decreased,the content of sucrose gradually decreased,and the content of organic acids showed a downward trend during storage.NO treatment can reduce the rate of sucrose decomposition of wax apple mist fruits,slow down the reduction of total sugar content,can reduce the reduction of organic acids,and effectively slow down the fruit ripening and aging process.4.Analyze and determine the changes of energy substances and key enzyme activities during storage of wax apple fruit.The results showed that during storage,the ATP and AMP contents of the wax apple fruit continued to decline,the ADP content showed an upward trend,the energy charge continued to decline,and the activities of H+-ATPase and Ca2+-ATPase decreased.NO treatment can maintain a higher energy level,significantly delay the post-harvest wax apple firuit energy decline,maintain high H+-ATPase and Ca2+-ATPaseATP activity,NO treatment inhibits post-harvest wax apple fruit energy substance reduction and the increase of the cottony softening index is related to the NO treatment delaying the changes of metabolic enzyme activities related to respiratory metabolism of postharvest wax apple fruit,which in turn affects the ripening and senescence of the fruit.5.Analyze and determine the changes of lignin content and key enzyme activity of lignin synthesis pathway during storage of wax apple fruit.Studies have shown that during storage,the activities of PAL,C4H,4CL and POD of wax apple fiuit have increased during storage.The lignin content also continued to increase,and NO treatment inhibited the lignin content,PAL activity,C4H activity,4CL activity,and POD activity of wax apple fruit.Exogenous NO treatment inhibited the increase of key enzyme activities in the lignin synthesis pathway of postharvest wax apple fruit,and NO delaying the cottony softening process of wax apple fiuit was related to the inhibition of key enzyme activities in lignin metabolism pathway.