NITROGEN FIXATION IN THE ROOT NODULES OF VICIA FABA L. IN RELATION TO THE ASSIMILATION OF CARBON

Authors


  • *Present address: Department of Biological Sciences, University of Dundee.

SUMMARY

High activity of phosphoenolypyruvate carboxylase, malate dehydrogenase and malic enzyme has been found in extracts from broad bean nodules. Tracer studies of the metabolism of 14CO2 fixed by detached nodules showed that the amino acid fraction sequestered most radioactivity and that no radioactivity was associated with glucose and fructose, the main free sugars in ethanolic extracts of the nodules. The pattern of labelling supports an important role for glutamate, aspartate and asparagine in the metabolism of the fixed carbon, but relatively little radioactivity was associated with glutamine. Most of the radioactivity in the acidic fraction of the nodules was in malic and itaconic acids. Although the latter was not detected immediately on detachment of the nodules, it was present in amounts equal to malic acid 30 min after detachment.

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