[Studies on the phloem exudate of Cucurbita pepo L. : I. Enzyme activities of aerobic and anaerobic glycolysis and of the citric acid cycle].

In the phloem exudate of Cucurbita pepo enzyme activities of aerobic and anaerobic glycolysis as well as of citric acid cycle were tested. All enzymes of the aerobic glycolysis and the alcoholic fermentation were present. In the phloem these metabolic pathways should be functioning as well. Since the lactate dehydrogenase could not be detected all the time, lactate fermentation is probably not an obligatory constituent of phloem metabolism. Of the citric acid cycle the enzymes malate dehydrogenase, isocitrate dehydrogenase, aconitase, fumarase and succinate dehydrogenase were analyzed. The activities decrease in the given order of enzymes. Succinate dehydrogenase could not be detected at all. The possibility of finding the citric acid cycle respectively mitochondria in the exudate is discussed. The results do not suggest the presence of such a metabolic pathway in the exudate.