Cryptochromes control the circadian rhythm of GA2ox1 mRNA expression. mRNA expression of GA2ox1 and GA2ox2 genes in seedlings grown under long day (LD) or short day (SD) for 10 d and then transferred to continuous white light were examined using RT-PCR. Samples were collected every 3 h for 1 d in photoperiod and 2 d in continuous white light (A and B), or every 2 h for 1 d in long-day photoperiod (C and D). The white/black bars indicate light/dark phases, and the dashed bars indicate subjective night phase under continuous light. The time (hour) of light on of the first day of sample collection is set as zero.