Study On Photosynthetic Characteristics Of Leaves Of Summer And Winter Fruit Of Shine Muscat Grape Under Two-harvest-a-year Cultivation

In this experiment,the photosynthetic characteristics of summer and winter leaves of shine muscat grape were studied under the two-harvest-a-year cultivation.The photosynthetic response curve,diurnal variation of photosynthesis,net photosynthetic rate(Pn)and other photosynthetic and environmental parameters of leaves at the fourth node of different leaf ages were measured,as well as fruit quality and yield at ripening stage.The results shows:1.The average daily temperature of shine muscat grape,summer fruit and one harvest cultivation were 26.45-31.69?,25571-41934 lux,11.0-12.9 hours of illumination(>1200 lux),21.15-29.56?,106 71-37 949 lux and 8-10 hours of illumination.2.The maximum net photosynthetic rate(Pnmax),light saturation point(LSP),apparent quantum efficiency(AQE)of leaves of shine muscat grape at different leaf ages were higher,and the period of low persistence of light compensation point(LCP)was 55 days for summer fruit and one harvest cultivation,30 days for winter fruit,during which the photosynthetic capacity of leaves was stronger.3.The time when Pn of leaves of shine muscat grape decreased to the maximum value of 25%from spreading leaves to leaves:124 days for summer fruits and one harvest cultivation,87 days for winter fruits.The Pn of summer fruit,winter fruit and one harvest of cultivated leaves reached the maximum at the expansion stage,which were 19.10 ?mol/m2·s,16.44 ?mol/m2·s and 20.06?mol/m2·s,respectively.The Pn of summer fruit and one harvest of cultivated fruits began to decline sharply at the turn-color stage.The Pn of leaves began to age after harvesting of summer fruit and one harvest of cultivated fruits had dropped to 25%at the peak stage,and that of winter fruit had dropped to 0.There was no significant difference in Pn between summer fruits and one harvest cultivation in most of the leaf development stages,which indicated that the photosynthetic rate of leaves in the following year was not affected by two harvests.4.There was no significant difference between the diurnal variation trend of photosynthesis of summer and winter fruits of shine muscat grape and the control.Pn was positively correlated with environmental light intensity and transpiration rate(E),but negatively correlated with intercellular CO2 concentration(Ci).There was no significant correlation between Pn and temperature in summer fruits and one-harvest cultivation,indicating that temperature was not the limiting factor of Pn for summer fruits and one-harvest cultivation;Pn in winter fruits was positively correlated with temperature,indicating that temperature was the limiting factor of Pn for winter fruits.5.The optimum photosynthetic temperature of shine muscat grape leaves with leaf age of 50 days was 30-40 ? for summer fruit and control leaves,and 20-30 ? for winter fruit leaves.