THE RESPONSE OF FLOWERING DATE AND CROPPING OF PYRUS-COMMUNIS CV CONCORDE TO AUTUMN WARMING

The effect of autumn temperature on the flowering date and cropping of Pyrus communis cv. Concorde was examined. Trees were given artificial ly warm nights, designed to mimic autumn daily mean maximum temperatur es by enclosing them in mobile greenhouses at night in October and Nov ember. Warming potted trees in both months delayed the time at which f lower buds began to swell and subsequently influenced the developmenta l sequence of flowering. Treatment differences in the phenological dev elopment of the flower clusters became less obvious by full bloom. The re was no evidence to suggest that flower bud number per tree or flowe r number per cluster changed in response to warming. Warmed trees show ed less low-temperature injury due to late spring frost than the unwar med control trees. Despite this, the initial and final fruit sets were very similar. The results of this work are discussed in relation to y ear-to-year variations in the cropping of pear and are compared with e arlier experiments with pear cv. Conference.