Effects Of High Temperature And Strong Light Stress On Photosynthetic Performance Of Grape Fruits And Leaves

Global warming often causes extreme weather.High temperature and strong light caused widespread air and sunburn in grape leaves and fruits.High temperature and light stress not only affects the photosynthesis of grapes,but also directly affects the growth and development of the fruit,reduces the economic value of the commodity.Therefore,it is of great significance to study the photosynthetic performance and mitigation measures of grape fruits and leaves under high temperature and strong light stress.This paper investigated the effects of high temperature and light stress on photosynthetic performance of green fruit peels and grape peels at different developmental stages.The sensitivity of leaves of different grape varieties to high temperature and light stress was explored.The effects of spraying titanium dioxide and kaolin on leaves to alleviate high temperature and light stress were discussed.Get the following results:1.The effects of high temperature and light stress on the photosynthetic performance of summer black grapes were studied.The results showed that under high light conditions,Under the condition of constant light intensity,Grape green peel adapts to the increase in temperature by increasing the heat dissipation per unit area（DI_O/CS_M）.Under the condition of constant temperature,the increase in light intensity will aggravate the damage to the grape peel.The damage degree was the highest at 1600μmol·m^-2·s^-1 and 45℃.Under suitable light conditions,all three high temperature treatments could significantly reduce the photosynthetic performance of green peels.The difference at 45°C was the most significant compared to the control.V_J,DI_O/CS_M treated at 45℃increased by 61.29%and 42.22%compared to the control,andφ_Eo,ET_O/CS_M,TR_O/CS_M,and ABS/CS_M decreased by 78.58%,94.08%,90.08%,72.36%compared with the control.Under strong light,fluorescence properties of peels treated at 45°C were worsened than those treated at 25°C.V_J,DI_O/CS_M increased by 87.09%and 35.56%over 25℃treatment.In dark conditions,The difference at 45℃was more significant than that of the control.V_J,DI_O/CS_M treated at 45℃increased by 66%,122%compared to the control.φ_Eo,ET_O/CS_M,TR_O/CS_M,ABS/CS_M decreased by 57.48%,36.11%,52.78%and 14.91%compared with the control.2.Verified the high temperature and strong light stress on the green grape fruit burn level.It was found that,as the light intensity increases,the temperature of the peel begins to show symptoms.Under light conditions,the peel treated at 40℃began to appear yellowing symptoms.Under strong light conditions,the peel treated at 35℃first appeared yellowing symptoms.Moreover,under the strong light irradiation,the grape fruit treated at 45℃was the most seriously injured,and the grape peel yellowed in a large area.There are four levels of yellowing.There is no harm when the condition is suitable light with 35℃.Suitable light with 40℃causes first-level damage.Suitable light with 45℃and the strong light with 35°C cause second-level damage.Strong light with 40℃is the third-level damage.Strong light with 45℃is the fourth-level of damage.3.The change of antioxidant enzyme activity in green peel under high temperature and strong light was studied.It was found that POD activity was greatly affected by light intensity.SOD activity is greatly affected by temperature,under high temperature conditions,the increase in light intensity has less effect on the activity with SOD.The change trend of CAT activity is similar to that of POD,interaction of bright light and high temperature significantly increased CAT enzyme activity.4.As grape fruit develops,The content of chlorophyll in the skin of（Chanberein）grape gradually decreased,and the content of total anthocyanins gradually increased.Under the condition of high temperature and strong light,the W_K in the later stage of color transition was reduced by 18.8%and 12.9%compared with the hard-core stage and early stage of color transition,RC/CS_M increased by 185.8%and 32.8%,φ_Eo increased by 88.9%and 31.03%,respectively.Correlation analysis of the pigment content of the peel at different development stages and related photosynthetic fluorescence parameters found that the decrease in chlorophyll content has a significant positive correlation with the decrease in the ratio of light energy absorbed by the PSⅡreaction center,while the increase in total anthocyanin content has a significant positive correlation with the increase in PSⅡphotochemical efficiency.5.Photosynthesis of leaves of Frontenac,Merlot,Moldova,Cabernet Franc,Summer Black and Chanberein grapes under the cross-stress of high temperature and light was studied characteristic.It was found that under high temperature and strong light stress,the actual photochemical efficiency Y（Ⅱ）of grape leaves decreased,non-photochemical quenching NPQ increased.The susceptibility of each variety in order from small to large was Eurasian Cabernet Franc,Merlot>European and American species Summer Black>Interspecific hybrids Moldova,Chanberein,Frontenac.The chlorophyll fluorescence parameters of grape leaves（Frontenac,B2,B5）with different juice colors under high temperature and strong light stress were studied.The results showed that the red juice color grape leaves have strong resistance to high temperature and strong light stress.It was found that under high temperature and strong light stress,the RC/CS_Mof the B5 grape leaves was significantly increased by 16.71%compared to the Frontenac,RT_O/RC increased by 41.15%.6.Study on the mitigating effect of spraying titanium dioxide and kaolin on the leaves to high temperature and light stress,Three days after spraying on July 20,9‰kaolin treated PIABS increased by 195.49%compared with the control,and 0.6g/L titanium dioxide treatment increased by 84.72%compared with the control.And 10 days after spraying,on July 26,9‰kaolin treated PI_ABS increased by 485.56%compared with the control,and 0.6g/L titanium dioxide treatment increased by 221.11%compared with the control.And 10 days after the spray treatment,on July 26,compared with the control,the maximum photochemical efficiency（F_V/F_M）of 9‰kaolin and 0.6g/L titanium dioxide was significantly increased by46.25%and 33.44%,respectively,RC/CS_M increased by 130.58%and 94.35%,respectively.And the net photosynthetic rate（Pn）was significantly increased by 34.47%and 34.89%,respectively.