JXB Advance Access originally published online on December 8, 2006
Journal of Experimental Botany 2007 58(3):579-591; doi:10.1093/jxb/erl233
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© 2006 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
Does elevated atmospheric [CO2] alter diurnal C uptake and the balance of C and N metabolites in growing and fully expanded soybean leaves?
1USDA/ARS Photosynthesis Research Unit and Department of Plant Biology, University of Illinois, Urbana, IL 61801, USA
2Institute for Genomic Biology, University of Illinois, Urbana, IL 61801, USA
3Department of Environmental Sciences, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
4Department of Crop Sciences, University of Illinois, Urbana, IL 61801, USA
5Max Planck Institut für Molekulare Pflanzenphysiologie, D-14476 Golm, Germany
6ICG-III, Juelich Research Center, D-52425, Juelich, Germany
* To whom correspondence should be addressed. E-mail: ainswort{at}uiuc.edu
Increases in growth at elevated [CO2] may be constrained by a plant's ability to assimilate the nutrients needed for new tissue in sufficient quantity to match the increase in carbon fixation and/or the ability to transport those nutrients and carbon in sufficient quantity to growing organs and tissues. Analysis of metabolites provides an indication of shifts in carbon and nitrogen partitioning due to rising atmospheric [CO2] and can help identify where bottlenecks in carbon utilization occur. In this study, the carbon and nitrogen balance was investigated in growing and fully expanded soybean leaves exposed to elevated [CO2] in a free air CO2 enrichment experiment. Diurnal photosynthesis and diurnal profiles of carbon and nitrogen metabolites were measured during two different crop growth stages. Diurnal carbon gain was increased by c. 20% in elevated [CO2] in fully expanded leaves, which led to significant increases in leaf hexose, sucrose, and starch contents. However, there was no detectable difference in nitrogen-rich amino acids and ureides in mature leaves. By contrast to mature leaves, developing leaves had high concentrations of ureides and amino acids relative to low concentrations of carbohydrates. Developing leaves at elevated [CO2] had smaller pools of ureides compared with developing leaves at ambient [CO2], which suggests N assimilation in young leaves was improved by elevated [CO2]. This work shows that elevated [CO2] alters the balance of carbon and nitrogen pools in both mature and growing soybean leaves, which could have down-stream impacts on growth and productivity.
Key words: Amino acids, elevated [CO2], FACE, Glycine max, hexose, starch, sucrose, ureide
Received 19 June 2006; Revised 28 September 2006 Accepted 16 October 2006