The Effect Of Light On Jujube Sugar Accumulation And Transformation Of The Salinization Jujube Orchard In Xinjiang

Soil salinization stress and low light condition can affect plant photosynthesis, which result incorresponding change of fruits sugar metabolism, thereby affecting the quality of fruits. This experimentuses four years old plants Ziziphus jujube cv. Junzao (a cultivar of jujube) as test materials to study thechlorophyll contents, carbohydrate content,photosynthesis characteristics, microstructure and ultrastructureof leaves, and the single fruit weight, the sugars accumulation characteristics and sucrose-metabolizingenzymes activities of fruits, and their relationship under different light intensity, which will reveal theresponse mechanism to different light environment on synthesis and accumulation of jujube assimilationproduct under salinized soils. The results can provide a reference for reasonable close planting and trainingand pruning of salinized soil cultivation of jujube, the theory basis for jujube facility cultivation. The resultshowed as follows:1.The experiment place was mild soil salinization and the salt type was chlorinate-sulfate. With theincreasing of shade degree, the light intensity decreased gradually. The transmittance of light shade was79.0%, and the transmittance of heavy shade was63.2%. The chlorophyll content were increased undershade condition while the ratio of chl a/b decreased, the contents of carotenoid was not influencedobviously. The contents of soluble sugar increased under the light shade condition while decreased underthe heavy shade condition, the contents of starch and cellulose increased gradually with the increasing ofshade degree.2.With the increasing of shade degree and shade time, the leaf area and specific leaf area of Junzaowas increased, while the specific leaf weight, leaf thickness, palisade tissue and spongy tissue thicknesswas decreased, spongy tissue arranged loosely and cell gap grew bigger than control. The chloroplastswelling and deformation, and the number of chloroplast was reduced, the volume and quantity of thestarch grain in leaf cells were increased with the increasing of shade degree and shade time.3.With the increasing of shade degree, the photosynthesis rate gradually decreased, the stomatalconductance (Gs) decreased but the intercellular CO2concentration (Ci) increased, the non-stomatal factorswas the main factor to limit leaf photosynthesis of Junzao. Transpiration rate of the leaf at different extentunder shade treatment, water use efficiency of the leaf decreased under the heavy shade by shade55days,showing that photosynthesis functions of Junzao were restricted. 4.Shading treatments decreased the contents of soluble sugars, but did not affect their change trend.Shading treatments decreased the contents of starch in early stage of fruits development, but the differencein mature was no significant. There was no significant difference in contents of cellulose of Junzao fruitsbetween shading treatment and control under the shade55days, but the shade35days and45daysincreased the contents of cellulose of mature fruits. The shade35days has no affect on the contents ofpectin, with the prolong of treatment time, the pectin content of mature Junzao increased significantlyunder the55days heavy shade treatment.5.The major components of soluble sugars in jujube fruits were sucrose, glucose and fructose.With thegrowth and development of the fruits, reducing sugars content and sucrose content raised gradually. Thefruits mainly accumulated glucose and fructose at the early stage, the content of sucrose was lower and itbegan to accumulate rapidly in late period, and the mature fruits mainly accumulated sucrose, therefore,Junzao was the sucrose prevalent fruit. There was no significant difference in contents of glucose andfructose of mature fruits under the shade35days and45days, but the shade55days decreased thecontents of glucose and fructose of mature fruits. During the early period of shading, there was nosignificant difference in content of sugar between the shade treatment and control, while the sucrosecontents of Junzao was gradually reduced with the increasing degree of shade in the mid and late period offruits development.6.The invertase activity was high at the early stage but dropped rapidly with the fruits developmentuntil the fruits matured, and the acid invertase activity higher than neutral invertase activity in the wholegrowth development period of fruits. While the sucrose synthase and sucrose phosphate synthase activitywas low at the early stage, the activity of sucrose synthase and sucrose phosphate synthase were increasedwith the development of fruits. Shading treatment increased the invertase activity in early stage of fruitsdevelopment and sucrose synthase, sucrose phosphate synthase activity in fruits development mid and lateperiod. Correlation analysis showed that there was a negative correlation between the contents of sucroseand the activity of invertase, the activity of sucrose synthase and sucrose phosphate synthase was asignificant or extremely significant positive correlated with the sucrose accumulation. The sucrose synthaseand sucrose phosphate synthase are the chief enzymes which catalyzed synthesizing sucrose in the fruitsdevelopment mid and late period.7.The setting percentage and single fruit weight of Junzao were significant decreased with theincreasing of shade degree, meanwhile, shading treatment decreased the rate of fruits cracking and thenumber of black spot.