Effect Of Nitric Oxide Treatment On Physiological Metabolisms Of Improving 'Feicheng' Peach And Chinese Gooseberry Storage Capacities

The peach fruits(Prunus persica(L.) Batsch.,cv.Feicheng) were fumigated with 1000μl L^-1 ethylene,10μl L^-1 NO and 1000μl L^-1 ethylene/10μl L^-1 NO for 3 h,then stored at 1℃.Parts of Chinese gooseberry(Actinidia chinensis Planch.) were fumigated with 0,10,20 and 30μl·L^-1 NO for 3 h,then stored at 4 and 22℃.Other Chinese gooseberry were dipped with 0,0.5,1 and 2μmol L^-1 NO solutions for 10 min,then dried with wind,and stored at 4 and 22℃.The effects of different concentrations and ways of NO treatments on physiological indices of post-harvest fruit,including ethylene production rate,soluble protein,contents of sugar and acid,MDA,superoxide rdicals,chlorophyll and ACC contents,and activities of relevant enzymes from the fruits,including ACS,ACO,LOX,SOD,CAT,POD,were investigated.The results showed that fumigation with 1000μl·L^-1 exogenous ethylene promoted ethylene production,increased activities of ACS and ACO.Treatment with 10μl·L^-1 NO significantly inhibited the production of endogenous ethylene in fruit,reduced activities of ACS and ACO.The activities of ACS and ACO and ethylene production in fruit treated with 1000μl·L^-1 ethylene/10μl·L^-1 NO were significantly lower than those in fruit treated with exogenous ethylene,and higher than those in fruit treated with NO,suggesting that there were antagonistic actions between NO and exogenous ethylene.NO could inhibit biosynthesis of ethylene and catalysis of exogenous ethylene during ethylene biosynthesis in peach fruits.Chinese gooseberry fumigated with 20μl L^-1 NO had low content of soluble sugar and high content of titratable acids and Vc.Contents of MDA and superoxide radicals in Chinese gooseberry fumigated with 20μl L^-1 NO were lower than those in Chinese gooseberry fumigated with 10 and 30μl L^-1 NO.Fumigation with 20μl L^-1 NO reduced activities of LOX and POD in Chinese gooseberry,delayed the decrease of CAT activity during the late period of storage,significantly increased SOD activity,and decreased the content of hydrogen peroxide.Similar results were also found in Chinese gooseberry treated with NO solution.There were no significant differences in chlorophyll content in Chinese gooseberry fumigated with different concentrations of NO gas.However,the chlorophyll content in Chinese gooseberry soaked with 1μmol L^-1 NO was higher than that of the control.There were no differences in chlorophyll content in Chinese gooseberry soaked with 0.5 and 2μmol L^-1 NO,which were significant lower than treatment with 1μmol L^-1 NO.The carotenoid content in Chinese gooseberry fumigated with 20μl L^-1 NO was lower than that of the control, ande that in Chinese gooseberry soaked with 1μmol L^-1 NO were also lower than those of the control and treatments with other concentrations of NO。The optimal time of reaction between NO and ACC was 30 min,and proper concentration of ACC is 2 mmol L^-1.As cofactors of the enzymic reaction,the proper concentrations of Vc,NaHCO₃ and Fe²⁺ were 20 mmol L^-1,20 mmol L^-1 and 20μmol L^-1, respectively.The inhibition kinetics of NO analyzed by Based on Lineweaver-Burk' theory, we demonstrated that the inhibition kinetics of NO for the oxidation of ACC in the catalysis of ACCO was expressed as a noncompetitive inhibition model and NO was called a noncompetitive inhibitor.The apparent Michaelis constant K_m and the inhibition constant of noncompetitive reversible inhibitor K_i were determined to be 3.4 mmol L^-1 and 2.34μmol L^-1, respectively.