Objective  Morphological and physiological changes during flower bud differentiation of a Cymbidium hybrid were studied to decipher the floral formation mechanism.

  Method  The process of flower bud differentiation of Golden Elf 'Sun-dust' was observed by means of paraffin section. The physiological indices, such as soluble sugars, starch and soluble protein, were measured at different stages of the differentiation.

  Result  The differentiation process could be divided into 6 phases as undifferentiated and differentiations of inflorescence primordium, floret primordium, sepal primordium, petal primordium, and column and pollinia. During the process, the contents of soluble sugars and starch in the leaves fluctuated up and down; the soluble protein increased initially followed by a decline; and, the activities of POD and CAT decreased in the beginning and then increased.

  Conclusion  The accumulations of soluble sugars, starch and soluble protein in the leaves prior to flower bud differentiation and the effective utilization at latter stages were found to significantly affect the differentiation process as well as the subsequent flower formation of Cymbidium hybrid.