Environmental control of flowering time in Antirrhinum majus

The effect of different environmental conditions on flowering time and the number of leaves produced before the first flower is formed has been invest igated in Antirrhinum majus L. The effect of light quality has been tested by decreasing the red/far-red ratio, generally resulting in a reduced flowe ring time and leaf number. Furthermore, it could be shown that photoperiod, temperature and light intensity are inversely correlated with flowering ti me and leaf number. However, lowering the temperature from 15 to 12 degrees C resulted in a reduction of flowering time. This observation shows that A ntirrhinum can be vernalised. Using defined combinations of the four environmental factors we have been a ble to reduce flowering time to only 42 days or to delay flowering for at l east 2 years. The results obtained allow an optimisation of the screening c onditions for identifying flowering time mutants in Antirrhinum.