Contents of carbohydrates and endogenous hormones from dormancy to sprouting of Toona sinensis buds were measured. Dynamic changes of GA 1/3 , iPA and ABA were detected. GA 1/3 and iPA decreased when the dormancy began, and then increased to the highest value before bud sprouting. The lowest value of GA 1/3 , 358 7 ng·g -1 FW, was observed 21 days after leaf falling, whereas ABA was the highest, 201 5 ng g -1 FW. Thereafter, ABA decreased and GA 1/3 increased with the advent of bud sprouting. Ratios of GA/iPA and iPA/ABA decreased first and then increased from dormancy to sprouting with minor change range compared with GA 1/3 , iPA and ABA. This demonstrated that dormancy break was closely related to hormone change, concurrent with starch degradation and increase in soluble sugars.
