Study On The Relationship Between Chlorophyll Luorescence And Low Temperature Tress Of Apple Fruits

The changes of chlorophyll fluorescence parameters of ’Gala’ apples with lowtemperature stress treatment at0℃,-2℃,-4℃and ‘Honeycrisp’ apples with1-MCP treatment(1.0μL·L-1,24h) and CaCl2-Xanthan gum treatment were determined by FMS-2chlorophyllfluorescence analyzer during room temperature storage. The chlorophyll fluorescenceparameters and traditional physiological and quality indicators were statistically analyzed, inhope to establish the relationship between chlorophyll fluorescence parameters changes andfruit postharvest physiology and quality changes, to provide a certain theoretical basis andtechnical guidance for the further development of the fruit quality and physical healthnon-destructive monitoring. The main research results were as follows:(1)Low-temperature stress treatments resulted in chlorophyll fluorescence parametersdecline. One day after treatments, Fo, Fm, Fv and Fv/Fm values of-2℃treatment groupwere respectively15.2%,20.4%,22.8%,6.3%lower and values of-4℃treatment groupwere respectively26.6%,46.8%,55.9%,20.1%lower than the control group. The chlorophyllfluorescence parameters of-4℃treatment groups were significantly lower than-2℃group，and-2℃group were significantly lower than the control group during storage (P<0.05). Lowtemperature stress accelerated fruit senescence and quality decline. Physiological and qualityindicators response to low temperature stress varied in different degrees. Changes inchlorophyll fluorescence parameters were significantly negatively correlated to the changes ofpeel browning index, a*value and the solid acid ratio, They were negatively correlated to therelative conductivity changes and were significantly positively correlated to changes infirmness, TA content, L*and H°values. This preliminary proved that there is a certaincorrelation between chlorophyll fluorescence parameters changes and low temperature stressof apples. The-2℃treatment significantly affected the chlorophyll fluorescence parameters，but had almost no effects on other related physiological and quality indicators, Chlorophyllfluorescence parameters more sensitively responded to low temperature stress.(2)Fo, Fm, Fv and Fv/Fm values of ’Honeycrisp’ apples decreased along with the naturalaging during room temperature storage. The drop of Chlorophyll fluorescence parameters wasclosely related to senescence process and physiological metabolic state. Compared to CK,1-MCP and Ca-X treatment significantly delayed fruit senescence, at the same time, delayed the declines of chlorophyll fluorescence parameters (P<0.05). At the end of storage, Fo, Fm,Fv and Fv/Fm values of1-MCP treatment group were respectively14.3%,23.4%,55.6%, and26.2%higher than the control group. The values of Ca-X were25.4%,43.1%,106.1%, and44.6%higher than the control group. The physiology and fruit quality decreased with agingduring storage. Physiological and quality indicators had responded to fruit senescence indifferent degrees. The declines of chlorophyll fluorescence parameters were significantlypositively correlated to the decline of firmness, SSC, TA content, L*, a*, chlorophyll content,anthocyanin content, and were significantly negatively correlated to the increase of solid acidratio, b*, H°, carotenoid content, weight loss, the relative conductivity, the incidence of bitterpit disease and the rotting rate of fruit. Chlorophyll fluorescence parameters can effectivelyrespond to the changes in fruit physiology and quality caused by natural aging, reflecting thephysiological state and immanence feature of apple.(3)1-MCP had a certain preservation effect on room temperature stored ’Honeycrisp’apples, but it increased the fruit rotting. Ca-X had better preservation effect than1-MCP, andit could completely suppress the occurrence of bitter pit without aggravating fruit rot.