Changes Of Sugar And Related Enzyme Activities In Apple Bud And Shoot Before Dormancy And Budbreak

Apple is a perennial fruit tree, carbohydrate accumulation and related enzyme activity changes before dormancy play a pivotal role in overall tree nutrition whether it is in dormancy or budbreak. Currently the previous researches mainly concentrate on the tendency of soluble sugar and starch contents, and the related enzymes such as invertase and sucrose synthase in metabolism have not formed a system, so in this aspect we should be further improved. In our experiment we used dwarf ‘Fuji' and ‘Gala' apple trees as test materials, and analyzed the changes of total soluble sugar, reducing sugar, sucrose and starch content before dormancy in xylem, phloem and bud, and the activities of neutral invertase(NI), acid invertase(AI), sucrose phosphate synthase(SPS), sucrose synthase(SS) and amylase in the phloem and bud before dormancy. we also measured the above indexes in apple flower bud during budbreak. The main results are as follows:1.Along with the advancement of dormancy, the distribution of sucrose, reducing sugar and total soluble sugar content infruit trees' different parts was phloem>bud>xylem, and both were significantly positive correlation between any sugars;2.Beforedormancy, starch content in xylem continued to accumulate, other carbohydrate contents changed little, starch and soluble sugarcontent in the xylem was significant negative correlation(correlation coefficient is-0.856*) at the early dormancy.3.During theexperiment, any enzyme activities in bud were higher than phloem, AI and sucrose content in phloem and bud was significant negativecorrelation(correlation coefficient is-0.909**?-0.783**); SPS and sucrose content in the bud was significantly positively related(correlation coefficient is 0.649*).4.During budbreak stage, contents of total soluble sugars, reducing sugars and sucrose in ‘Fuji' and ‘Gala' flower buds all showed a falling trend; starch content increased during the initial stage of budbreak, and decreased rapidly after entering the full break stage.5.During budbreak, AI activity and the contents of total soluble sugars, reducing sugars and sucrose in ‘Fuji' and ‘Gala' flower buds had significant negative correlations(correlation coefficients were-0.871*?-0.904*?-0.877**, and-0.957**?-0.908*?-0.857** in ‘Fuji' and ‘Gala', respectively); Starch content and amylase activity were significantly and negatively correlated(correlation coefficient were-0.908* and-0.861*).In conclusion, before dormancy period, the xylem began to store starch, and then was hydrolyzedwith the coming of dormancy, which increased the soluble sugar content;and at the same time, the content of sucrose in each organwas increased rapidly, which was concerned with rising activity of SPS and falling activity of AI.Soluble sugars in apple floral buds were the main energy source at initial stage of budbreak. During the full break stage, the degradation of stored starch played a vital role in sprouting because of increased material and energy requirements. The key regulating enzymes were AI and amylase, and the nutrient reserve were largely consumed during budbreak.