Abstract
Various tissues in flower buds of Pyrus calleryana Decne. differ in their metabolic activity. Brown outer scales utilized more exogenously supplied glucose, particularly through the pentose phosphate pathway, than did the central axes and the green inner scales. They also contained more endogenous reducing sugars, and glucose leaked out more readily from the brown scales than from the other tissues. In contrast, respiration of the central axes was nine times as great as that of the brown scales, and two to four times as much glucose was metabolized through glycolysis. Membranes of the central axes were less permeable to glucose. Because the brown scales are 75% of the dry weight of the bud, they dominate its pattern of glucose metabolism.