Effects of High Temperature Stress on Photosynthetic and Fluorescence Characteristics of Centennial Seedless and Wuhe Cuibao Grape Leaves

【Objective】 To investigate the effect of high temperature stress on its photosynthesis and photosynthetic characteristics through the changes of photosynthetic and fluorescence characteristics of Centennial Seedless and Wuhe Cuibao grapes under different light and temperature conditions. 【Methods】 In the experiment, the Centennial Seedless and Wuhe Cuibao grapes were used as materials, and the photosynthetic indexes were measured by instruments such as LI-6400, FMS-2. The effect of high temperature stress on photosynthesis of Centennial Seedless and Wuhe Cuibao grapes were comprehensively analyzed. 【Results】 During the grape growth and development period（April to September） in 2020,the highest temperature in the high temperature environment was 43 ℃,the number of days when the highest daily temperature exceeded 40 ℃was 16 days;the highest temperature in the suitable temperature wasonly 38 ℃.And the highest PAR light radiation intensity values in high and suitable temperature were 1,887 and 1,730 µmol/（m²·s）, respectively. The diurnal variation of net photosynthetic rate of two cultivars both showed bimodal curve. At 10：00 the high temperature environmentPn reached up to 18.9 µmol/（m²·s）, which was higher than that 13.0 µmol/（m²·s） in the suitable temperature. The light compensation point of ‘Centennial Seedless’ was higher in the suitable temperature environment, while Wuhe Cuibao was in the high temperature environment; the apparent quantum efficiency and dark respiration rate of the two varieties were higher in the high temperature environment. The qP and NPQ values of Wuhe Cuibao in high temperature environment were higher than suitable environment; ΦPSⅡ value and electron transfer rate of Centennial Seedless in high temperature environment significantly were greater than the suitable environment. 【Conclusion】 In the high temperature environment, the net photosynthetic rate of Centennial Seedless is the highest, and its photosynthetic capacity is better.The variety can grow well in the high temperature environment because it has adapted to high temperature areas.