It has been established that the absence of isocitric dehydrogenase activity in cotyledons ofVigna sesquipedalisin the germination stage is due to the lack of endogenous TPN. It is unlikely that the TCA cycle in the cotyledon is operative.The activities of enzymes of the glyoxylate cycle, a modified TCA cycle, were measured through the germination stage. Their activities were considerably higher in the cotyledon tissue than in the hypocotyl. A dominant metabolic pathway of isocitric acid in the cotyledon may be the glyoxylate cycle.DPN kinase which produces TPN from DPN, ATP and Mg++was localized in the supernatant portion of cell components in the cotyledon. Its activity was low. DPN kinase serves as a control factor for the cotyledon metabolism.
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