Studies On The Postharvest Physiology Of Younane Fruit(Prunus Salicina Lindl Var.Cordata)

Changes of some physiological indexes including respiratory rate, ethylene production and its biosynthetic characters, concentrations of endogenous abscisic acid, gibberellin3 and polyamines, the activities of lipoxygenase and protective enzymes (superoxide dismutase and peroxidase) during younane(Prunus salicina Lindl var.Cordata J.Y Zhang et al) fruit postharvest maturation and senescence under various storage temperatures and reagent treatments (ethrel, abscisic acid, gibberellin3, spermindine and calcium) were preliminarily studied. In addition,changes in quality ingredients of younane fruits during storage periuod and the optimal combination of treatments for younane storage and preservation were also studied. The relations between the physiological indexes and both ethylene and fruit ripening and senescening were discussed. The results showed as follows:(l)The changes of younane fruits postharvest respiratory rate showed double climacteric pecks. The changes in respiratory rate were similar to the changes in ethylene production and the activity of ethylene forming enzyme, but differed from the changes in content of I -aminocyclopropane- I -carboxylic acid. The effect of different storage temperature on the above-mentioned indexes was significant. Low temperature significantly inhibited the respiratory rate and ethylene evolution rate during storage, delayed the appearance of climacteric peak.(2) The changes in abscisic acid content of younane flesh at different storage temperature showed single peak. The period of peak appearance agreed with that of ethylene production. ABA decreased quickly after senescence. Exogenous abscisic acid treatment before climacteric period led to the respiratory rate and ethylene production increases.(3)Generally, gibberellin3 content of flesh decreased during storage period, but two little peaks were found at seven and sixty-three days after harvest. The treatment of exogenous gibberellin3 efficiently reduced the respiratory rate andethylene production of fruits, inhibited the accumulation of abscisic acid and lipid peroxidation, delayed fruit ripening and senescence.(4)Three kinds of polyamines(putrescine, spermidine and spermine) were found in younane fruits after harvest. Contents of putrescine and spermidine were far higher than those of spermine. Total polyamines and spernidine, spernine decrease during storage period, however the content of putrescine increased slowly. Suitable low temperature storage led to increase of polyamine synthesis, under room temperature polyamine content decreased slowly.(5)The changes of lipoxygenase activity showed three peaks during the ripening and senescence process of younane fruit. The first peak occurred at 7 days or so after harvest, and the second and third peaks occurred at the first respiratory peak and ethylene production peak, respectively. There was a significant negative correlation between lipoxygenase and fruits firmness.(6)Calcium treatment after harvest led respiratory rate and ethylene release rate increases, suggesting calcium accelerated younane fruit senescence. However, Calcium had no influence on ethylene biosynthesis process.(7)During storage period, the fruits finnness, the contents of flesh titratable acid , vitamin C, chlorophyll decreased, while the content of flesh alcohol increased. Carotenoid content before climatical peak increased, but decreased after climatical peak. The suitable conditions for refrigerated storage and preservation of younane fruits were as follows: polyethylene plastic package of 0.04mm 憲 0.O6mm+ ethylene absorber + 2 C --4 ~ +1 00mg/kg gibberellin3. Seventy days after storage, the rate of good fruits was still 100% and weight losing rate was merely 0.87%, and none of browning fruit was found.