THE INFLUENCE OF AUTUMN TEMPERATURE ON FLOWERING TIME AND CROPPING OF PYRUS-COMMUNIS CV CONFERENCE

The influence of autumn temperatures on flowering and cropping date was examined for Pyrus communis cv. Conference, Warming potted trees in both October and November delayed bud development and the date of blossoming, relative to unheated control and field-grown trees. The later the warming treatment was applied in the autumn, the more the flowering date was delayed. The delay in flowering date is suggested to be due to an increase in bud dormancy in response to a reduction in winter chilling. Mean fruit yields and fruit number per tree were greater in trees warmed during October compared with unheated control trees, but declined with heating in November. Some evidence is presented which suggests that flower number per cluster may decline with warming. Both the initial and final set increased with warming. Fruit set was also likely to have been influenced by treatment differences in fruit number per tree. The results ofthis work are discussed in relation to attempts to provide a physiological understanding of recently reported effects of temperature on the year-to-year variation in cv. Conference cropping.