Abstract:

【Objective】The relationship between floral bud differentiation and endogenous hormones in chrysanthemum (Chrysanthemum morifolium) was studied. 【Method】 The autumn-cutting chrysanthemum ‘Jinba’ was short-day treated, and the dynamic changes of endogenous hormones during floral bud differentiation were studied after measuring the morphological anatomies in flower bud and the endogenous hormones in apical bud and leaves. 【Result】 The results showed that GA3 contents in apical bud decreased and stayed at a low level in most of the time, however, the changes of GA3 contents in leaf were the contrary to the apical bud. The IAA contents in apical bud decreased first and reached the minimum value at the initial stage of floret primordia differentiation, and then reached the maximum value at the metaphase stage of crown formation. The IAA contents in leaf showed an increasing tendency before the initial stage of involucre primordia differentiation, then decreased later, and changed to be steady until the stage of crown formation. The contents of CTK increased greatly and were higher than those at the vegetative stage. The ABA contents in apical bud decreased first and then showed an increasing tendency, while ABA contents in leaves increased first and showed a decreasing tendency after a short steady period. The ratios of CTK to IAA, CTK to GA3, ABA to IAA and ABA to GA3 increased after flower bud differentiation started. 【Conclusion】 The research results showed that increasing in contents of CTK and ABA was related with floral bud differentiation of chrysanthemum. At early stage of flower differentiation, decreasing in contents of IAA and GA3 in apical bud and increasing in contents of IAA and GA3 in leaves were related to converting from vegetative growth to reproductive growth, while accumulating in contents of GA3 and IAA in apical bud was related to crown formation at final stage of flower differentiation. As to the hormones balance, maintaining high ratios of CTK to IAA, CTK to GA3, ABA to IAA and ABA to GA3 were beneficial to flower bud formation.

Key words: Chrysanthemum morifolium, floral bud differentiation, endogenous hormones