Plant Physiol. Drug Metab Dispos
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Plant Physiology 63:816-820 (1979)
© 1979 American Society of Plant Biologists

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Articles

Variation in Nitrogenase and Hydrogenase Activity of Alaska Pea Root Nodules 1

Gabor J. Bethlenfalvay2 and Donald A. Phillips

a Department of Agronomy and Range Science, University of California, Davis, California 95616

Hydrogenase activity of root nodules in the symbiotic association between Pisum sativum L. and Rhizobium leguminosarum was determined by incubating unexcised nodules with tritiated H2 and measuring tissue HTO. Hydrogenase activity saturated at 0.50 millimolar H2 and was not inhibited by the presence of 0.10 atmosphere C2H2, which prevented H2 evolution from nitrogenase. Total H2 production from nitogenase was estimated as net H2 evolution in air plus H2 exchange in 0.10 atmosphere C2H2. Although such an estimate of nitrogenase function may not be quantitatively exact, due to uncertain relationships between H2 exchange and H2 uptake activity of hydrogenase, differences observed in H2 exchange under various conditions represent an indication of changes in hydrogenase activity. Hydrogenase activity was lower in associations grown under higher photosynthetic photon flux densities and decreased relative to total H2 production by nitrogenase. Total H2 production and hydrogenase activity were maximum 28 days after planting. Thereafter, hydrogenase activity and H2 production declined, but the potential proportion of nitrogenase-produced H2 recovered by the uptake hydrogenase system increased. Of five R. leguminosarum strains tested two possessed hydrogenase activity. Strains which had the potential to reassimilate H2 had significantly higher rates of N2 reduction than those which did not exhibit hydrogenase activity.

2 Present address: Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, La. 70803.

1 This material is based on research supported by National Science Foundation Grants No. PRF 77-07301 A01 and PCM 78-01146. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the National Science Foundation.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1979 by the American Society of Plant Biologists