| To understand the responses of photosynthetic physiology to low light and its performance after regaining normal light,we research the Light reaction and dark reaction stage of the material and physiological metabolic changes in grapevine leaves.In this study,the potted ’Kyoho’ four-year-old grapevine was used as the material,70% shading as the low light treatment after the flower blooming for 20 days,then the light was restored to the control level.The following photosynthesis index was measured and analyzed: Chlorophyll content,SPAD value,leaf sugar content and composition,The gene of light-related enzymes in the Calvin cycle and sucrose phosphate synthase gene expression,the activity of SPS and FBPase and the changes of fruit quality index at maturity.The results turn out:1.Low-light treatment after full-blooming resulted in decreased soluble solids content,titratable acid content increased,anthocyanin contentdecreased,decreased fruit length,and reduced fruit quality and size.2.The chlorophyll a / b value decreased,the photochemical efficiency(Fv/Fm)decreased and the photochemical rate(ΦPSⅡ)decreased,the non-photochemical quenching(NPQ)increased,the apparent quantum yield(AQY)and the maximum net photosynthetic rate(Pm)were both decreased in grapevine leaves Under low light intensity,the up ratio of chlorophyll b content in leaves could promote the capture of light energy in photosynthetic pigments.However,long-term low light stress caused damage to PSⅡ photosynthetic center,and the ability of photoperiod capture and utilization reduced;3.The gene expression of Rubisco,PRKase,and Rubisco activating(RCA)were inhibited;the expression of enzymes related to sucrose metabolism(SPS,FBPase)were down regulated,activity of the enzymes and the content of fructose,glucose and sucrose in the leaves decreased,indicating that the long-term low light stress could inhibit the photosynthetic carbon assimilation by inhibiting the expression and activity of key enzymes in the Calvin cycle of the dark stage of grape leaves.The low light caused the reduction of photosynthetic products accumulation in leaves;4.Fv/Fm and AQY increased slightly,NPQ was reduced and the expression of key enzymes genes in Calvin cycle was partially restored.After 50 days of light restoration to control level,Rbc L1 was still lower than that of the control.The results indicated that long-term low light damage to the photosynthetic center of grapevine leaves was irreversible for a short time,and may have a long-term adverse effect on the expression of key enzyme genes in Calvin cycle.Concluded that,under long-term low light,the photosynthetic center of grape leaves was damaged,the photosynthetic capacity decreased,and the synthesis and accumulation of photosynthetic products decreased,which resulted in the decrease of fruit and fruit quality. |
