Studies On Physiological Mechanism Of Sugar Metablolism In Ziziphus Jujuba Mill Cv.Lingwuchangzao Fruit

In this study, we used Ziziphus jujuba Mill cv.lingwuchangzao as test materials and focus on sugar accumulation and metabolism to research the photosynthetic characteristics of leaves and fruits in the process of fruit development, the sugar accumulation and sucrose metabolizing enzyme activities of leaves, carpopodium and fruit in different stages of fruit development., the effect of shading on pigment content, sugar metabolism and accumulation, and the discrepancies among different strains of Ziziphus jujuba Mill cv.lingwuchangzao in sugar metabolism and accumulation. The result showed that:1) The growth curves of Ziziphus jujuba Mill cv.lingwuchangzao fruit showed double S pattern, there are two rapid growth phases. Sucrose is the main mode of sugar accumulation, the ratio of sucrose/reducing sugar was ahout1.2at ripe stage. In the early of fruit development, acid invertase (AI), neutral invertase (NI)and sucrose synthase (SS) participate in sucrose catabolism,in the late of fruit development, sucrose synthase enzyme synthesis direction(SS-s) and sucrose phosphate synthase (SPS) are important enzymes which catalyze the synthesis of sucrose. Sucrose synthase enzyme synthesis (SS-s) plays a major role in regulating the sugar metabolism of Ziziphus jujuba Mill cv.lingwuchangzao fruit.2) Both leaves and fruits have photosynthetic capacity, but majoring in leaves’ photosynthesis. Photosynthetic efficiency of leaves and fruits are affected by temperature and light, thereby affecting the growth and the related sugar content in fruit. The negative peak of net photosynthetic rate(Pn) in fruit is the result of respiration and photosynthesis. In this study, the pigment content and net photosynthetic rate were negatively correlated. Fruit influence on sink strength by passing a high transpiration rate(Tr), stomatal conductance (Gs)and intercellular co2concentration(Ci) to achieve the adjustment of source leaves photosynthesis.3) Leaves and carpopodium mainly accumulated sucrose and starch respectively. Sucrose in the stalk of the vascular bundles forms a certain concentration gradient from vein to carpopodium, which ensure that the sugar transport from the source to sink. In the entire period of fruits’ growth and development, there is a similarity of enzyme activities on sucrose cleavage between leaves and carpopodium. Activity of enzymes on sucrose synthesis in carpopodium are higher than the leaves. Sugar-metabolizing enzymes activity in leaves and carpopodium mainly manifest as cleavage direction4)Shading does not change variation regulation of growth and sugar accumulation in Ziziphus jujuba Mill cv.lingwuchangzao fruit, but the corresponding indexes have different degrees decline. In the late of fruit development, the volume and accumulation of sucrose are affected mostly, compared with contorl group,the decreased percentages of volume’s and sucrose’s content at ripe stage were38.99%and52.83%respectively,but diameter and shape of the fruit are not affected significantly. The fruits maintain high sink strength through increased invertase and related enzyme activity after shading to meet the material and energy need for its growth and development.5) The different strains of Ziziphus jujuba Mill cv.lingwuchangzao fruits do not accumulated starch which is one of the main sugar accumulation modes. There are significant differences in ratios and accumulation rate among the different kinds of sugar, contents in the same kind of sugar, and enzyme activity of sucrose-metabolism in fruit among four different strains of Ziziphus jujuba Mill cv.lingwuchangzao. The essence leading to differences is related to genetic characteristics among different strains.