THE EFFECT OF TEMPERATURE ON INFLORESCENCE INITIATION AND SUBSEQUENT DEVELOPMENT IN CHRYSANTHEMUM CV SNOWDON (CHRYSANTHEMUM X MORIFOLIUM RAMAT.)

The relationships between temperature and time to inflorescence initia tion and subsequent development in chrysanthemum cv. Snowdon (Chrysant hemum x morifolium Ramat.) were investigated. From pinching, flowering occurred most rapidly in plants grown at a mean temperature of 20.4 d egrees C, whilst those grown at 10.9 degrees C had the lowest leaf num ber at flowering. The final leaf number, from the pinch to the inflore scence, increased with increasing temperature above 10.9 degrees C. Th is could be attributed to a marked sigmoidal increase in the rate of l eaf initiation with temperature, not delayed initiation. Above 20 degr ees C temperature had little effect on the time of floral initiation ( plants initiating after 8-9 days), although temperatures below this le d to a considerable delay in floral initiation (20.5 days at 9.6 degre es C). Once initiated the inflorescences developed most rapidly at 20. 2 degrees C, however, unlike the process of flower initiation, subsequ ent flower development was delayed by both warmer and cooler temperatu re regimes. (C) 1998 Elsevier Science B.V. All rights reserved.