Flowering and stem growth in the celery-leaved buttercup, Ranunculus sceleratus

The semiaquatic celery-leaved buttercup, Ranunculus sceleratus L. flowers under 18-h photoperiods (long days (LD)) but remains vegetative under 8-h photoperiods (short days (SD)). A minimum of 20-30 LD are required for floral bud initiation which occurs prior to the elongation of the flowering stalk. The effects of LD on flowering and the subsequent growth of the flowering stem can be mimicked with gibberellin (GA3) under SD. When plants which have been induced to flower by 28 LD are submerged, the flower stalk elongates rapidly over the next 48 h. Submergence effects can be mimicked by C2H4, but not by GA3 or indole-3-acetic acid (IAA) applications.