Abstract: To investigate an effective way to break dormancy in Lily bulbs, Siberian Lily bulbs were used to study the effects of low temperature and GA₃ on the morphological and physiological changes, the change of endogenous GA₃ in different temperature and different parts of lily bulbs. The results showed that, the ratio of bud length and total height of bulbs reached 67.954%, the bud growth point located at the 2/3 vertical height of bulb, and the time spent on dormancy releasing was minimum under the treatment of low temperature (5℃) and GA₃ (0.15 g·L^-1) for 35 d. Under the condition of low temperature (5℃), the starch degradation rate was fastest in bulbs with the treatment of 0.15 g·L^-1 GA₃ in 0-14 d, moreover, the soluble sugar content and reducing sugar content reached the maximal value at the 35^th d. The endogenous GA₃ content was changed noticeably in inner scales and buds under low temperature condition, and the changes was more visible with the decreasing of temperature. Consequently, low temperature and GA₃ treated together have significant effects on dormancy breaking in bulb of Siberia Lily, the optimum concentration of GA₃ was 0.15 g·L^-1, the optimum temperature was 5℃. The endogenous GA₃ content was higher with low temperature treatment in inner scales and buds, and had the most evident escalating trend; however, the endogenous GA₃ content was lower in outer scales and roots, and had a less change trend. It will be seen from this that, the kernel of dormancy breaking in the whole bulb might be the terminal bud and inner scales.

Key words: low temperature, GA₃, bulb, carbohydrate, dormancy