Author: ["Arnold J. Bloom","Martin Burger","Bruce A. Kimball","Paul J. Pinter, Jr"]
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Abstract
Reductions in the protein and nitrogen content of plants grown under enhanced atmospheric CO2 concentrations could adversely affect the quality of food grown in the future, but the mechanisms of change remain unclear. Now research investigating plant responses to enhanced levels of atmospheric CO2 under field conditions finds that wheat nitrate assimilation was slower for elevated CO2 than for ambient CO2. Total protein and nitrogen concentrations in plants generally decline under elevated CO2 atmospheres1,2. Explanations for this decline include that plants under elevated CO2 grow larger, diluting the protein within their tissues3,4; that carbohydrates accumulate within leaves, downregulating the amount of the most prevalent protein Rubisco2; that carbon enrichment of the rhizosphere leads to progressively greater limitations of the nitrogen available to plants4; and that elevated CO2 directly inhibits plant nitrogen metabolism, especially the assimilation of nitrate into proteins in leaves of C3 plants5. Recently, several meta-analyses have indicated that CO2 inhibition of nitrate assimilation is the explanation most consistent with observations6,7,8. Here, we present the first direct field test of this explanation. We analysed wheat (Triticum aestivum L.) grown under elevated and ambient CO2 concentrations in the free-air CO2 enrichment experiment at Maricopa, Arizona. In leaf tissue, the ratio of nitrate to total nitrogen concentration and the stable isotope ratios of organic nitrogen and free nitrate showed that nitrate assimilation was slower under elevated than ambient CO2. These findings imply that food quality will suffer under the CO2 levels anticipated during this century unless more sophisticated approaches to nitrogen fertilization are employed.Cite this article
J. Bloom, A., Burger, M., A. Kimball, B. et al. Nitrate assimilation is inhibited by elevated CO2 in field-grown wheat. Nature Clim Change 4, 477–480 (2014). https://doi.org/10.1038/nclimate2183 