Studies On 1-MCP Delaying Ripening And Senescence Of Harvested ’Furong’ Plum Fruit And Its Physiological Mechanism

Plum(Prunus salicina Lindl.)is famous in China.Plum fruit mature in warm season with vigorous physiological activity,which caused rapid deterioration and decay of fruit after harvest,restricting the development of plum fiuit production in China.In this paper,’Furong’(Prunus salicina Lindl.cv.’Furong’)plum fruit,a major plum cultivar in Fujian province was used as material.The objectives of this study were to clarify the mechanism of delayed ripening and senescence of harvested’Furong’ plum fruit by 1-MCP treatment.The main results are showed as follows:1.The optimum dose of 1-MCP treatment was selected for harvested ’Furong’plum fruit.The effects of 1-MCP treatments with different concentrations(0,0.3,0.6,0.9,1.2,1.5 μL/L)on harvested ’Furong’ plum fruit were studied.The results showed that compared with the control fruits,1-MCP treatment lowered the respiration rate and respiratory peak of ’Furong’ plum fruit,delayed the increase of cell membrane relative leakage rate of fruit,inhibited the decrease of hue angle(h°)value of fruit surface,and it also maintained higher fruit firmness,higher contents of total soluble solids(TSS),titratable acid(TA)in fruit and chlorophyll in peel;in the meanwhile,it could lower the content of anthocyanin in peel,retard the change of apparent color,maintained the higher rate of commercially acceptable fruit and decrease fruit weight loss.Among the different concentrations of 1-MCP,the fruit treated with 1.2 μL/L 1-MCP treatment showed the preferable storage quality.Therefore,1.2 μL/L1-MCP was recognized as the optimum concentration treatment for harvested ’Furong’ plum fruit at(25±1)℃ in this study.2.Effects of 1-MCP treatment on physiology,quality and storability of harvested ’Furong’ plum fruit were investigated.The results showed that compared with the control fruits,1.2 μL/L 1-MCP treatment could effectively reduce fruit respiration rate,respiratory peak and fruit decaying,inhibit the increase of fruit cell membrane relative leakage rate and the decrease of hue angle(h°)value in surface,keep contents of peel chlorophyll,peel carotenoid and lower contents of anthocyanin in peel and pulp,and hold relatively higher contents of total soluble solids(TSS),tinratable acid(TA),reducing sugar,soluble sugar,vitamin C,and fruit firmness,maintain the higher rate of commercially acceptable fruit,decrease fruit weight loss and decay.3.Effects of 1-MCP treatment on cell wall metabolism of harvested ’Furong’plum fruit were evaluated.The results showed that compared with the control fruits,1.2 μL/L1-MCP treatment could reduce the activities of cell wall degrading enzymes like pectinmethylesterase(PME),polygalacturonase(PG),β-galactosidase(β-Gal)and cellulase(Cx),and thus delaying the decrease of contents of cell wall material(CWM),covalent-soluble pectin(CSP),cellulose,hemicellulose,and the increase of the contents of water-soluble pectin(WSP)and ionic-soluble pectin(ISP).Therefore,1-MCP treatment could effectively reduce the activities of cell wall degrading enzymes and decrease the degradation of cell wall components,so as to maintain the integrity of the cell wall structure and higher fruit firmness.4.Effects of 1-MCP treatment on ROS metabolism of harvested ’Furong’ plum fruit were studied.The results showed that compared with the control fruits,1.2μL/L1-MCP treatment maintained higher activities of ROS scavenging enzymes such as superoxide dismutase(SOD),catalase(CAT)and ascorbate peroxidase(APX),and higher contents of endogenous antioxidant substances such as glutathione(GSH)and ascorbic acid(AsA).It also decreased the production rate of superoxide anion radical(O2-·)and malondialdehyde(MDA)content obviously in harvested ’Furong’ plum fruit pulp.Therefore,it could be concluded that 1-MCP treatment enhanced active oxygen scavenging capacity,which inhibited the accumulation of reactive oxygen species that can undermine cell membrane structure,and delayed membrane lipid peroxidation of ’Furong’ plum fruit to retard ripening and senescence.5.Effects of 1-MCP treatment on tissue energy metabolism of harvested’Furong’ plum fruit were studied.The results showed that compared with the control fruits,1.2 μL/L1-MCP treatment maintained a higher level of ATP content and energy charge,kept relatively higher activities of cytochrome c oxidase(CCO)and NAD kinase(NADK),maintained higher activities of H+ATPase,Ca2+-ATPase and Mg2+-ATPase and higher content of NADP(H),and delayed the accumulation of NAD(H).Therefore,it could be suggested that 1-MCP treatment could maintain higher energy level and concentrations of extra and intracellular ions for repairing the cell membrane system,resulting in better of the cell membrane integrity to retard fruit ripening and senescence.6.Effects of 1-MCP treatment on the membrane lipid metabolism of harvested’Furong’ plum frut were analyzed.The results showed that compared with the control fruits,1.2 μL/L 1-MCP treatment decreased activities membrane lipid-degrading enzymes such as phospholipase D,lipase and lipoxygenase(LOX).1-MCP treated fruits inhibited higher relative contents of the unsaturated fatty acids,such as oleic acid(C 18:1),linoleic acid(C18:2)and linolenic acid(C18:3),and a lower relative contents of the saturated fatty acids,such as palmitic acid(C16:0)and stearic acid(C18:0)during storage.As a result,the degradation of index of unsaturated fatty acids(IUFA)and unsaturated degree of fatty acids were inhibited.From the results,it could be concluded that 1-MCP treatment delaying ripening and senescence of’Furong’ plum fruit may be due to decreases of activities of phospholipase D,lipase and LOX,which may reduce the degradation of unsaturated fatty acids of membrane lipids and maintain higher unsaturated degree of fatty acids,in turn,may reward a transition of membrane lipid from predominantly liquid crystalline to gel-phase lipid,and the formation of nonbilayer lipid structures,resulted in maintaining integrity of cell membrane structure and compartmentalization within the cell to retard fruit ripening and senescence.7.Effects of 1-MCP treatment on disease resistance of harvested ’Furong’ plum fruit were analyzed.The results showed that compared with the control fruits,1.2μL/L 1-MCP treatment could effectively increase the activities of chitinase(CHI),β-1,3-glucanase(GLU)and phenylalanine ammonialyase(PAL),decrease the activities of polyphenol oxidase(PPO)and peroxidase(POD),and thus increasing the accumulation of lignin content.Therefore,it could be showed that 1-MCP treatment increased activities of disease defense-related enzymes and contents of disease defense-related material to inhibit enzymatic reaction,which improved disease resistance and decreased decay of ’Furong’ plum fruit.