Physiological comparisons of root and stem nodules of Aeschynomene scabra and Sesbania rostrata |
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Authors: | Mariangela Hungria Allan R. J. Eaglesham Ralph W. F. Hardy |
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Affiliation: | (1) Boyce Thompson Institute for Plant Research, Cornell University, 14853, NY, USA;(2) Present address: EMBRAPA-CNPSoja, Caixa Postal 1061, 86001 Londrina, Brazil, Parana;(3) Present address: Metapontum Agrobios, I-75010 Metaponto (MT), Italy |
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Abstract: | A few legume species possess the ability to form N2-fixing nodules on stems as well as on roots. Little is known of the functional characteristics of stem nodules, or to what extent they differ from root nodules. Stem and root nodules of greenhouse-grown plants of Aeschynomene scabra (inoculated with the photosynthetic rhizobial strain BTAi 1) and Sesbania rostrata (inoculated with Azorhizobium caulinodans strain BTSr 3) were examined for assimilation of 14CO2 in the light and dark, soluble carbohydrate and starch contents, acetylene reduction activity, relative efficiency of nitrogenase in terms of uptake-hydrogenase activity, glutamine synthetase and glutamate synthase, and reduced N and ureide contents. In general, stem nodules possessed higher enzyme activities and metabolite contents than did root nodules, suggesting that they fix N2 with greater energy efficiency. This greater efficiency correlated with photosynthesis in the cortex of stem nodules. Differences in enzyme activities and metabolite contents between the stem nodules on A. scabra and those on S. rostrata probably result either from legume-species characteristics or from the photosynthetic capability of strain BTAi 1. |
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Keywords: | acetylene reduction glutamate synthase glutamine synthetase PEP carboxylase Photorhizobium thompsonianum strain BTAi 1 photosynthetic Rhizobium relative efficiency |
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