Effects of heat stress and exogenous brassinolide on photosynthesis of leaves and berry quality of‘Kyoho'grapevine

【Objective】The research aimed at unraveling the effects of heat stress and exogenous brassino-lide(BR) on photosynthesis physiology and berry quality of table grapevine Kyoho(Vitis vinifera × Vitis labrusca).【Methods】The net photosynthesis rate(Pn),chlorophyll fluorescence parameters,chlorophyllcontent and berry quality of three- year- old potted‘Kyoho'grapevines were investigated under heatstress with 0.1 mg·L- 1exogenous BR application.【Results】Pn,ΦPSII,q P and the chlorophyll contentdecreased,while Fo increased when vine was treated by heat stress for 3 days. Fv/Fm started to decline af-ter 6 days. Moreover,berry weight,the contents of titration acid and anthocyanins were significantly re-duced under heat stress compared with the control. However,the maximum photosynthetic rate(Amax),ΦPSII,q P,Fv/Fm and the chlorophyll content were increased under the treatment with exogenous BR af-ter 20 days heat stress. The content of anthocyanins of the skin under BR treatment was 2.1 times higherthan the control.【Conclusion】Continuous heat stress can reduce the activity of PSII reaction center,dis-rupt normal function of PSII,inhibit the photosynthesis of grape leaf and reduce berry quality. Sprayingexogenous BR can effectively alleviate the photosynthetic system damage caused by high temperaturestress,and it can also greatly improve the content of anthocyanins in the skin.