The effect of temperature on inflorescence initiation and subsequent development in chrysanthemum cv. Snowdon (Chrysanthemum×morifolium Ramat.)

Abstract The relationships between temperature and time to inflorescence initiation and subsequent development in chrysanthemum cv. Snowdon (Chrysanthemum×morifolium Ramat.) were investigated. From pinching, flowering occurred most rapidly in plants grown at a mean temperature of 20.4°C, whilst those grown at 10.9°C had the lowest leaf number at flowering. The final leaf number, from the pinch to the inflorescence, increased with increasing temperature above 10.9°C. This could be attributed to a marked sigmoidal increase in the rate of leaf initiation with temperature, not delayed initiation. Above 20°C temperature had little effect on the time of floral initiation (plants initiating after 8–9 days), although temperatures below this led to a considerable delay in floral initiation (20.5 days at 9.6°C). Once initiated the inflorescences developed most rapidly at 20.2°C, however, unlike the process of flower initiation, subsequent flower development was delayed by both warmer and cooler temperature regimes.