Effects of Heat Stress on Chlorophyll Fluorescence and Photosynthetic Characteristic Parameters in Grape(Vitisvinifera L.'Manicure finger')

【Objective】 The objective of this research is to study the effects of chlorophyll fluorescence and photosynthetic characteristic parameters of grape leaves under heat stress, and to explore the response mechanism of grapevines to heat stress in the hope of providing a theoretical basis forresearchingheat tolerance mechanism of grape and taking appropriate cultivation managements to reduce the impact of high temperature. 【Methods】 The annual grapevines Manicure finger(VitisviniferaL.cv.)were selected and cultured in the artificial climate chamber, which were treated at 35℃ , 40℃and 45℃ for 16 h, with the plants at 25℃ as the control to determine OJIP curve, chlorophyll fluorescence and gas exchange parameters in grape leaves and analyze the effects of chlorophyll fluorescence and photosynthetic characteristics parameters of grape leaves under heat stress. 【Results】 (1) The P_n decrease of Manicure finger grape were not caused by stomatal factor after 16 h heat stress, and the gas exchange parameters would be restored to normal after heat stress relieved for 8h; (2) When temperature exceeded 40℃, the fluorescence value of Manicure finger grape decreased on the OJIP curve, especially in J-I phase and I-P phase, which was significantly lower than that of CK.(3) The F_v/F_m value of Manicure finger grape were not significantly different at 35℃, but the F_v/F_m value were decreased significantly when it exceeded 40℃; (4) In the high temperatures condition, the F₀, V_j, ABS/RC, DI₀/CS₀ were increased, the F_m,F_v/F₀,F_v/F_m,PI_ABS,TR₀/CS_m,ET₀/CS_m,ψ_o,φE₀ were decreased, which affected the electron capture and transfer in PSII center, leading to the decrease of photochemical conversion efficiency and the increase of heat dissipation ratio in PSII. 【Conclusion】 Under high temperature stress, the grape ‘Manicure finger’ can reduce the photochemical efficiency of PSII by reducing the absorption of light energy, quantum yield and electron transfer, thus reducing the photochemical efficiency of PSII.