INFLORESCENCE COMMITMENT AND SUBSEQUENT DEVELOPMENT DIFFER IN THEIR RESPONSES TO TEMPERATURE AND PHOTOPERIOD IN OSTEOSPERMUM-JUCUNDUM

Although Osteospermum is a species which is known to require a period of chilling to induce flowering, the precise form of the relationships between temperature and photoperiod on the phases of flowering has no t been quantified. This study aimed to investigate the effects of temp erature and photoperiod on time to inflorescence commitment and on the rate of subsequent floral development in Osteospermum jucundum cvt Zu lu. To assess how temperature and photoperiod affected the number of d ays needed for inflorescence commitment, plants were transferred from a range of photothermal environments to a non-inductive environment. T he effect of temperature and photoperiod on subsequent inflorescence d evelopment was examined by transferring plants with initiated inflores cences to a range of photothermal environments. Inflorescence commitme nt occurred first in plants grown at a low average diurnal temperature (10.6 degrees C), but no evidence was found to suggest that photoperi od affected the duration of this phase. Once initiated, high temperatu res and long days hastened inflorescence development. The rate of prog ress to flowering from initiation increased linearly with photoperiod and temperature (up to an optimum of 23.5 degrees C).