Increased C availability at elevated carbon dioxide concentration improves N assimilation in a legume

Authors

  • ALISTAIR ROGERS,

    Corresponding author
    1. Department of Environmental Sciences, Brookhaven National Laboratory, Upton, NY 11973-5000, USA,
    2. Department of Crop Science and
    Search for more papers by this author
  • YVES GIBON,

    1. Max-Planck-Insitut für Molekulare Pflanzenphysiologie, 14476 Golm, Germany,
    Search for more papers by this author
  • MARK STITT,

    1. Max-Planck-Insitut für Molekulare Pflanzenphysiologie, 14476 Golm, Germany,
    Search for more papers by this author
  • PATRICK B. MORGAN,

    1. USDA/ARS, Plant Science Research Unit, Raleigh, NC 27603, USA
    Search for more papers by this author
  • CARL J. BERNACCHI,

    1. Department of Plant Biology, University of Illinois at Urbana-Champaign, Champaign IL 61801-4798, USA,
    Search for more papers by this author
    • *

      Present address: Center for Atmospheric Sciences, Illinois State Water Survey, Champaign IL 61820-7495, USA.

  • DONALD R. ORT,

    1. Department of Crop Science and
    2. Department of Plant Biology, University of Illinois at Urbana-Champaign, Champaign IL 61801-4798, USA,
    3. Photosynthesis Research Unit, US Department of Agriculture/Agricultural Research Service (USDA/ARS), 1201 West Gregory Drive, Urbana, IL 61801, USA, and
    Search for more papers by this author
  • STEPHEN P. LONG

    1. Department of Crop Science and
    2. Department of Plant Biology, University of Illinois at Urbana-Champaign, Champaign IL 61801-4798, USA,
    Search for more papers by this author

Alistair Rogers. Fax: +1 631 344 2060; e-mail: arogers@bnl.gov

ABSTRACT

Plant growth is typically stimulated at elevated carbon dioxide concentration ([CO2]), but a sustained and maximal stimulation of growth requires acquisition of additional N in proportion to the additional C fixed at elevated [CO2]. We hypothesized that legumes would be able to avoid N limitation at elevated [CO2]. Soybean was grown without N fertilizer from germination to final senescence at elevated [CO2] over two growing seasons under fully open-air conditions, providing a model legume system. Measurements of photosynthesis and foliar carbohydrate content showed that plants growing at elevated [CO2] had a c. 25% increase in the daily integral of photosynthesis and c. 58% increase in foliar carbohydrate content, suggesting that plants at elevated [CO2] had a surplus of photosynthate. Soybeans had a low leaf N content at the beginning of the season, which was a further c. 17% lower at elevated [CO2]. In the middle of the season, ureide, total amino acid and N content increased markedly, and the effect of elevated [CO2] on leaf N content disappeared. Analysis of individual amino acid levels supported the conclusion that plants at elevated [CO2] overcame an early-season N limitation. These soybean plants showed a c. 16% increase in dry mass at final harvest and showed no significant effect of elevated [CO2] on leaf N, protein or total amino acid content in the latter part of the season. One possible explanation for these findings is that N fixation had increased, and that these plants had acclimated to the increased N demand at elevated [CO2].

Ancillary