Effects Of Soil Water Contents On Photosynthetic Characteristics And Fruit Quality Of Pear-jujube

Jujube trees in our country's Northern shaan xi play an important role in the fields ofecological protection and local economic development, but low rainfall and unevendistribution of precipitation restrict growth of jujube trees and development of red jujubeindustry at this region. With potted pear-jujube seedlings of three years old, the experimentmeasured effects of normal water supply, moderate drought stress and severe drought stress(Corresponding soil water content is70%,55%and40%of field capacity, respectively) onphotosynthetic characteristics, water consumption and fruit quality of jujube trees at fruitexpanding stage and maturity stage, for the sake of discussing effects of soil watereffectiveness on the growth of jujube trees and the quality of red jujube, and contrast theresults of field trial. Research results obtained are as follows:1) From the result analysis of light response cure and simulated parameters, at fruitexpanding stage, though moderate and severe drought stress both reduced maximum netphotosynthetic rate(Amax), there were no significant differences only between moderatedrought stress and normal water, indicating that moderate drought had little influence onphotosynthetic potential of pear-jujube tree. Moderate drought stress significantly reducedlight compensation point (LCP), which enhanced the ability of utilizing dim light. Significantreduction of LCP and Rdwere both beneficial to accumulation of photosynthetic productunder drought condition. However, at fruit maturity stage,Amaxand light saturation point(LSP)declined remarkably, which indicates that moderate drought stress remarkably influencesphotosynthetic potential of pear-jujube tree and utilization of hard light. Though LCP rose tosome extent, it was not significant. The non significant rise of LCP indicates that moderatedrought stress has little influence on the utilization of dim light. Moreover, severe droughtstress has significant influence on photosynthetic potential, and the utilization ratio of hardand dim light.2) Diurnal variation of photosynthetic parameters indicated that Pnand Gsshowed almostconsistent variation tendency at the same stage under different water treatments, and goodcooperativity existed between Pnand Gs. At fruit expanding stage, The decline of Pnbetween13:00-15:00under normal water supply, accompanied by the reduction of Ciand the ascent ofLs, was possibly mainly influenced by stomatal factors. Moderate drought treatment was ableto enhance stomatal conductance(Gs), which increased net photosynthetic rate(Pn),transpiration rate(Tr) and instantaneous luminous energy utilization ratio(LUE) as well as water utilization ratio(WUE) between11:00-19:00in a day, and the reduction of Pnwasmainly influenced by non-stomatal factors. Severe drought treatment was able to enhanceWUE between11:00-19:00, but reduced Gs, leading Pn, Trand LUE into decreasing in a wholeday, and the reduction of Pnwas mainly influenced by stomatal factors. At fruit maturity stage,moderate drought treatment reduced Gs, Pn, Trand LUE of pear-jujube tree, and the degree ofreduction was the same as that of severe drought treatment, but both water treatmentsenhanced WUE.3)Water consumption of every pear-jujube tree every day decreased with the decline ofsoil water content at fruit expanding stage and maturity stage, which finally resulted in thedecline of total water consumption of every pear-jujube tree with soil water content decliningat these stages. This indicates that drought stress was able to decreased remarkably waterconsumption of pear-jujube tree. What's more, water consumption of every tree every day atfruit expanding stage under the same water condition was bigger than that of fruit maturitystage and water consumption at fruit expanding stage was bigger than that of fruit maturitystage finally. Compared with the normal water supply, moderate stress simultaneouslydecreased water consumption more than30%. Compared with severe stress, moderate stresswas able to enhanced fruit yields significantly.4) Drought stress made soluble protein content and single fruit weight both significantlydecreased, but reducing sugar, soluble sugar, Vcand organic acid content all increasedremarkably with the decline of soil water content.5) Compared with field trial, at fruit expanding stage, though drought stress of mademaximal photosynthetic rate and apparent light quantum efficiency of potted jujube treedecrease, it increased LSP-LCP and decreased Rd. Compared with pot trial, though droughtstress of field trial reduced the capacity of utilizing hard light, increased the capacity ofutilizing dim light. At the same time, with the reduction of soil water content, Amax,LSP-LCPand AQY of jujube tree at field trial were higher than that of potted jujube tree. Jujube tree atfield trial also showed strong drought resistance. Gs, Pnand Trunder different water treatmentsof pot trial and field trial existed good consistency at the stage. At fruit maturity stage, AQYunder different water treatments of pot trial and field trial was almost the same. Among threewater treatments, LSP-LCP under middle stress was maximal at field trial, but LSP-LCPunder normal water supply was maximal at pot trial. Moreover, Rdunder different watertreatments of field trial was lower than Rdat pot trial, indicating that photosynthate consumedby dark respiration under different water treatments of field trial was lower than that of pottrial. Gs, Pnand Trunder different water treatments of pot trial existed good consistency at thestage, but there were no distinct consistency among them under all the water treatments offield trial.