Effects of an amino acid fertilizer on the leaf photosynthesis and fruit quality of'Summer Black'grape

The experiments were conducted with'Summer Black'grapes to study the effects an amino acid fertilizer diluted 600,800 and 1 000 folds on the leaf photosynthesis and fruit quality.The results showed that all treatments significantly raised the relative content of chlorophyll,the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),apparent quantum yield(AQY),and somewhat decreased light compensation point(LCP)and dark respiration(Rd)of the grape leaves.Compared with the control,the Pn became more than doubled.Measurements of chlorophyll fast fluorescence revealed that,the photosynthetic performance indexes based on absorption(PIABS)or cross section(PICS),or the total including PSⅠand PSⅡ(PITOTAL),the probability of a trapped exciton moves an electron into the electron transport chain beyond Q-A(ψ0)and quantum yield of electron transport(φEo)were all significantly improved but the approximate initial slope of the fluorescence transient(Mo),the amplitude of the K step(Wk)and the proposition of energy dissipation through heat(φDo)were all significantly depressed compared with the control.Fertilizer treatments significantly promoted the leaf areas and fruit quality.The leaf areas,the berry weight,the anthocyanin content,the total soluble solids and the soluble sugars(SS)were all increased,but the titratable acid(TA)decreased.Thus,the treated grapes possessed higher ratio of SS to TA and better quality.The treatment of 800 fold dilution increased anthocyanin content by 119% and soluble sugars by 60.06% respectively,which was considered to be the best.