This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Edie, S. A. Articles by Phillips, D. A. Search for Related Content PubMed PubMed Citation Articles by Edie, S. A. Articles by Phillips, D. A. Agricola Articles by Edie, S. A. Articles by Phillips, D. A.

Articles

Effect of the Host Legume on Acetylene Reduction and Hydrogen Evolution by Rhizobium Nitrogenase ¹

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

The relative efficiency (RE) of N₂ fixation (RE = 1 - [H₂ evolved in air]/[acetylene reduced]) was investigated in a Rhizobium strain lacking uptake hydrogenase activity (Hup^–). Variation in RE of such strains presumably reflects changes in the electron allocation coefficient of nitrogenase. By artificially extending the normal dark period of 24-day-old Pisum sativum L. cv `Alaska' inoculated with the Hup<sup>–</sup>R. leguminosarum strain 3740, reproducible changes in RE were obtained. The RE showed no change during a normal 8-hour night, but a significant increase in RE was measured after 20 hours in the dark. Upon returning to the normal 550 microEinsteins per square meter per second light treatment, RE declined to previous levels within 2 hours. If, after the 20-hour dark treatment, plants were returned to 90 or 190 microEinsteins per square meter per second or maintained in the dark, RE did not decline significantly. The RE varied inversely with changes in soluble sugar content of root nodules. A similar pattern of changes in RE during an extended dark period and subsequent light treatment was measured in 28-day-old Alaska peas and in the Hup<sup>–</sup>R. trifolii strain 162X99 in symbiosis with Trifolium subterraneum L. cv `Woogenellup.' These results suggest that Rhizobium cells may produce short-term alterations in the electron allocation coefficient of nitrogenase in response to physiological changes. The observed changes in the bacterial RE favored N₂ reduction over proton reduction when soluble sugars provided by the host plant declined.

¹ Supported by a postgraduate fellowship from the Natural Sciences and Engineering Research Council of Canada and by United States National Science Foundation Grant No. 78-01146.

This article has been cited by other articles:

				J. Curtis, G. Shearer, and D. H. Kohl Bacteroid Proline Catabolism Affects N2 Fixation Rate of Drought-Stressed Soybeans Plant Physiology, October 1, 2004; 136(2): 3313 - 3318. [Abstract] [Full Text] [PDF]

				B. Pan and J. K. Vessey Response of the Endophytic Diazotroph Gluconacetobacter diazotrophicus on Solid Media to Changes in Atmospheric Partial O2 Pressure Appl. Envir. Microbiol., October 1, 2001; 67(10): 4694 - 4700. [Abstract] [Full Text]

				P.-O. Lundquist Nitrogenase Activity in Alnus incana Root Nodules. Responses to O2 and Short-Term N2 Deprivation Plant Physiology, February 1, 2000; 122(2): 553 - 562. [Abstract] [Full Text]