Reversion of floral development under adverse ecological conditions in Whytockia bijieensis (Gesneriaceae)

The reversion of floral development in Whytockia bijieensis Y.Z.Wang et Z.Y.Li occurs after the normal initiation of mid-adaxial sepals, which implies that the floral organs are not determined at the initiation of the floral primordium, but progressively determined during its development. Both low humidity (less than 75%) and low night temperature (12-14°C) contribute to the reversion of floral development. However, the low humidity or low night temperature alone do not greatly affect the normal flowering process. The combination of these two ecological factors seems to considerably disturb the normal flowering process, greatly strengthening the reversion process of flowering. High humidity and moderate temperature or at least one of the two are necessary for the normal flowering process of W. bijieensis. It is likely that low humidity and low night temperature trigger the reversal to vegetative growth during floral development. The change of a flower into a bract-like organ in the flower pairs indicates that a transition from pair-flowered to normal cymes is possible.