Pear bud metabolism: seasonal changes in glucose utilization.

Utilization of glucose, uracil and valine by flower and leaf buds of seedling pear trees (Pyrus calleryana Decne.) from the time of flower bud initiation to flowering was investigated. A very high rate of glucose utilization through the pentose phosphate pathway was observed throughout the development of buds. There was no difference in the type of glucose metabolism between flower and leaf buds except immediately before flowering, when the metabolism in flower buds was shifted toward the glycolytic pathway. Such a shift did not occur in leaf buds. The incorporation of uracil and valine into the nucleic acid and protein fraction of buds, respectively, was high throughout bud development, perhaps indicating a high rate of turnover in the resting buds. Incorporation of both compounds decreased when buds started to expand prior to flowering.