Abstract: During the development of higher plants, the transition from juvenile phase to adult phase is referred to vegetative phase change（VPC）. VPC is one of the important physiological processes in plant development, which is related to circadian clock regulation. Unfortunately, regulation of circadian clock related genes during this transition remain unknown. In this paper, we investigated characters of VPC in mutants of circadian clock-related gene, LHY and CCA1. Our results showed that onset of abaxial trichomes of rosette leaves, paraffin section of shoot apical meristems and expression of miR156 indicated that vegetative phase change in lhy, cca1 is delayed. This retardation is concomitant with affecting development of SAM（including tunica, corpus and pith meristem zone）, and is regulated via miR156.

Key words: vegetative phase change, lhy, cca1, circadian clock, Arabidopsis thaliana