Study On Carbohydrate Metabolism During Flower Bud Induction Of ’Fuji’ And Regulating With PBO

Fuji is the most important cultivar in China, while it is difficult to flowering inproduction. In order to clarify the carbohydrate metabolism characteristics of Fuji appleduring the period of flower bud induction and reveal the regulatory mechanism that how PBOpromoting flower bud formation. Experiments were carried out with two cultivars Fuji andGala possessing different flowering habits, with the same rootstock Begonia and interstockM.26, combined with spraying growth regulator PBO on Fuji, carbohydrate metabolicpathways under different treatments were studied during flower bud induction. Results are asfollows:Results of tree growth characteristics and carbohydrates metabolism of Fuji and Galaduring folwer bud induction:(1) Gala flowering rate was significantly greater than Fuji for allshoots. Especially flowering rate of spur terminal buds for Gala was up to80%, which was2times than Fuji and4times for axillary buds than Fuji;(2) The maximum spur growth rate ofGala was30%higher than Fuji. the date forming Spur and medium shoot of Gala were almost10days earlier than Fuji.(3) Coming to the end of flower bud induction, the spur terminalbud dry weight of Gala was greater than Fuji, the average dry weight of Gala was103%higher than Fuji; Spur terminal bud growth rate of Gala was3times than Fuji, and thedifference significantly; Spur terminal bud growth rate of Gala peaked at May30, that was20days earlier than Fuji;(4) Thers were no significant difference for types of monose betweencultivars, while starch concentration in spur terminal bud of Gala was significantly higherthan Fuji during the medium term of flower bud induction(May10-June10) and the peak ofstarch concentration appeared20days in advance when compared to Fuji;(5) There were nosignificant difference in metabolic enzymes activity(sucrose synthase, sucrose phosphatesynthase, neutral invertase, acid invertase) in terminal bud for Gala and Fuji during the earlystage of flower bud induction, while in the middle and later stage of folwer bud induction thefour enzymes activity of Gala were always higher than Fuji.Results of carbohydrate metabolism of Fuji after spraying growth regulator PBO:(1)After spraying PBO, dry weight of spur terminal bud were highter than control(withoutspraying PBO) and bud growth rate was greater than that of the control at the early and middle stage of flower bud induction(May10-June10)(2) The concentration of sucrose(May20-June20) and glucose(May30-June10) in spur terminal bud and ajacent leaf withPBO treatment were significantly greater than that of the control at the middle stage of flowerbud induction(May30-Jun10); The concentration of starch content in spur terminal bud withPBO treatment was higher than that of the control and PBO(June10) accelerated starch peakto appear about10days in anvance when compared to the control(June20).(3) The metabolicfour enzymes activity with PBO were always higher than that of the control at the middle andlate stage of flower bud induction(June10-June30).(4) Whether spraying PBO or not, therewere no correlation between monose and relative metabolic enzymes activity; The bud dryweight change rate was not related to the metabolic four enzymes activity, but with PBO therewas a positive correlation between bud dry weight change rate and acidic conversion enzyme,neutral conversion enzyme activity.In conclusion, the carbohydrate metabolism of Gala conducted earlier and reached thedestination state earlier than Fuji which was benifical to flower bud induction. For Fuji, thelower level of acid invertase, neutral invertase activity in spur terminal buds may have effecton sucrose and starch accumulation in spur terminal buds and its adjacent leaf, thus affectingflower bud induction of Fuji, making it difficult to form flower buds. Spraying PBO promotedrealevant carbohydrate metabolism of flower bud induction in Fuji and these promotion wasgood for bud to induct flower.