Transition of Metabolisms in Living Popular Bark from Growing to Wintering Stages and Vice Versa: Changes in Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenase Activities and in the Levels of Sugar Phosphates 1

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RESUMO

Activities of glucose 6-phosphate, 6-phosphogluconate, and isocitrate dehydrogenases, together with intermediate levels of the glycolytic pathway and the pentose phosphate cycle, were measured throughout a year in the living bark of poplar (Populus gelrica). Shoots, immediately after budding (early May), contained very high levels of the three enzyme activities, which fell gradually by early or mid-July to a level, roughly equivalent to budding (May) or growing (July) 2-year-old twigs. In September, the former two dehydrogenase activities of the new shoots and 2-year-old twigs began to rise, while the latter activity started to decrease. The rise of the two dehydrogenase activities continued until late November (or early December). The high level of the two dehydrogenase activities lasted until early in April of the following year and then the decrease in the activities began prior to the onset of budding, reaching a low, basal level in early May. The profile of changes in the two dehydrogenase activities appeared to coincide with the increase and decrease of soluble proteins.

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