Abstract
The effects of the duration of a 24-hr photoperiod and gibberellin or uniconazole application on inflorescence formation in turnip plants (Brassica rapa L. cv. ‘Hikari’) were investigated using the flower formation index (Saito and Saito, 2001). Plants were grown under 24-hr photoperiods for 0, 10, 20, 30, 40 or 75 days. The percentage of plants with terminal inflorescences and the flower formation index increased as the 24-hr photoperiodic duration was prolonged. The percentage of plants with terminal inflorescences was 100% in all gibberellin treatments and the flower formation index was highest for application of gibberellin throughout the whole period in each photoperiodic treatment. Gibberellin promoted the effect of inflorescence formation. With application of uniconazole, the percentage of plants with terminal inflorescences was suppressed and the flower formation index decreased remarkably. We thought that the effect of flower induction was accumulated by 24-hr photoperiodic treatment but its effect was smaller than that of low temperature. Moreover, we thought that gibberellin substituted for the effect of the long-day treatment on inflorescence formation, although the effect of gibberellin was not strong.
