Abstract: This paper studied the effects of Ca²⁺ -carrier A23187 and Ca²⁺ -chelator EGTA on the bud differentiation of cut flower chrysanthemum (Dendranthema grandiflorium ‘Shenma’) under photoperiodic induction, as well as the Ca²⁺ distribution and the sucrose, soluble sugar, and starch contents in ‘Shenma’ leaves during the differentiation. In the control, the leaf Ca²⁺ content was lower at the vegetative stage of apical bud (Ⅰ), increased rapidly and reached a peak at the stage of initial differentiation (Ⅱ), and decreased then. At stage Ⅰ, the Ca²⁺ was mainly allocated in vacuole, cell wall, and cell lacuna; while at stage Ⅱ, it was more in cytoplasm. Compared with the control, the leaf Ca²⁺ content of A23187-treated plants increased significantly, and the days of initiation and ending of bud differentiation were advanced by 2 days and 3 days, respectively. On the other hand, the leaf Ca²⁺ content of EGTA-treated plants decreased significantly, and the days of initiation and ending of bud differentiation were postponed by 4 days and 8 days, respectively. For both A23187- and EGTA-treated plants, their leaf Ca²⁺  at stage Ⅱ was more allocated in cytoplasm. The leaf sucrose and soluble sugar contents of A23187-treated plants reached a peak on the 2nd day after treatment, and the time to reach the peak was shortened by 2 days, compared with the control, which was consistent with the peak time of Ca²⁺ . The leaf sucrose and soluble sugar contents of EGTA-treated plants had no significant changes on the 2nd day of treatment, but increased rapidly and reached the peak on the 8th day of treatment (stage Ⅱ), and then decreased. However, the leaf sucrose and soluble sugar contents during the whole period of bud differentiation were higher than those before photoperiodic induction. The leaf starch content of A23187-treated plants and the control decreased 2 days after treatment, while that of EGTA-treated plants began to decrease 8 days after treatment, and maintained at a lower level by the end of bud differentiation. The results indicated that Ca²⁺ and carbohydrates participated in the flower formation of chrysanthemum under photoperiodic induction.

Key words: chrysanthemum, bud differentiation, A23187, EGTA, Ca²⁺ , carbohydrate, Haihe River, reservoir, sediment, heavy metal, ecological risk.