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Cobalt and nitrogen fixation in Lupinus angustifolius L. II. nodule formation and function

Dilworth, M.J., Robson, A.D. and Chatel, D.L. (1979) Cobalt and nitrogen fixation in Lupinus angustifolius L. II. nodule formation and function. New Phytologist, 83 (1). pp. 63-79.

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The effects of cobalt deficiency on nodule formation and function in sweet lupin (Lupinus angustifotius L. cv. Unicrop) were studied in cobalt‐deficient Lancelin sand in the glasshouse. Bacteroid densities in cobalt‐deficient nodules were lower than in normal nodules. Recovery from cobalt deficiency in inoculated treatments was associated with increases in bacteroid density and cobalt accumulation in lateral nodules. Such changes did not occur in treatments infected with rhizobia from the soil. Acetylene‐reducing activity of cobalt‐deficient plants was not initiated until plants were nearly 6 weeks old, at which time cobalt‐treated plants were at their peak of activity. Specific activities of cobalt‐deficient nodules remained very low even when nitrogenase did develop. Their large mass of nodules allowed cobalt‐deficient plants to reach 20 to 50 % of the normal activity per plant, but specific activities were only 5 to 13 % of peak activities in cobalt‐treated nodules. Nodule bacteroid content and leghaemoglobin content were linearly related to cobalamin content, each with a single relationship. Plotting acetylene‐reducing activity against cobalamin content or leghaemoglobin content generated two different linear response curves in each case; the slopes of the lines were different, depending on the presence or absence of cobalt. It is suggested that there may be a function in N, fixation in legume nodules for a non‐cobalamin form of cobalt.

Item Type: Journal Article
Murdoch Affiliation(s): School of Environmental and Life Sciences
Publisher: Blackwell Publishing
Copyright: © 1979 The New Phytologist
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