Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 413028
Title Photosynthetic adaptation of soybean due to varying effectiveness of N2 fixation by two distinct Bradyrhizobium japonicum strains
Author(s) Kaschuk, G.; Yin, X.; Hungria, M.; Leffelaar, P.A.; Giller, K.E.; Kuyper, T.W.
Source Environmental and Experimental Botany 76 (2012). - ISSN 0098-8472 - p. 1 - 6.
Department(s) Plant Production Systems
Crop and Weed Ecology
Chair Soil Biology and Biological Soil Quality
Publication type Refereed Article in a scientific journal
Publication year 2012
Keyword(s) glycine-max - temperature response - elevated co2 - leaves - carbon - limitations - merrill - starch - plants - model
Abstract Rhizobial N2 fixation is a costly biochemical process, which takes 6–14% of current photosynthate (C) from legumes, without compromising grain productivity. In addition to the effects of leaf N nutrition, rhizobial symbiosis could stimulate photosynthesis due to the removal of C sink limitation by nodule activity. To test that hypothesis, we compared the photosynthetic capacity of soybean plants inoculated with two different strains of Bradyrhizobium japonicum (CPAC 390 or CPAC 7), varying in the effectiveness to fix N2, with plants fertilized with NO3-. Nodulated plants had 14–31% higher rates of photosynthesis and accumulated less starch in the leaves than N-fertilized plants. There was evidence that B. japonicum CPAC 390 had higher carbon costs of N2 fixation compared with CPAC 7, but the increases in carbon costs were accompanied by higher rates of photosynthesis. By applying a biochemical model of leaf photosynthesis, including the limitations of Rubisco activity (VCmax), electron transport rates (J) and triose-P utilization (TPU), we show that soybean plants adapt their photosynthetic capacity to support the stronger carbon sink created by faster rates of N2 fixation. We observed that plants associated with CPAC 7 (of low effectiveness to fix N2) increased their photosynthesis by removing sink limitation solely (with a constant VCmax) whereas plants associated with CPAC 390 (of high effectiveness to fix N2) increased their photosynthesis by sink stimulation. Based on the model, we propose that sink stimulation is governed by a positive feedback between TPU and Rubisco activation, resulting in an increased VCmax
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