Wheat Growth Stimulated by High CO2


Arnold Bloom (Department of Vegetable Crops, University of California, Davis) and coworkers published the paper “Nitrogen assimilation and growth of wheat under elevated atmospheric carbon dioxide” in the February 5 issue of the Proceedings of the National Academy of Sciences (99:1730-1735). Bloom et al. grew wheat (the world’s major food crop) in elevated atmospheric carbon dioxide, a product of energy production. When wheat was grown in an atmosphere containing twice-ambient carbon dioxide (levels that may be realized later in this century) their growth was stimulated as expected. But the researchers found that the form of nitrogen supplied to the plant roots significantly affected their response to elevated carbon dioxide. When wheat was supplied with ammonium nitrogen, the growth stimulation caused by elevated carbon dioxide was about twice the growth stimulation as when plants were given nitrate nitrogen. Bloom et al. discovered that elevated carbon dioxide inhibited the assimilation of nitrate nitrogen by wheat, but not nitrogen in the ammonium form. This may mean that major changes in fertilizer practices in agriculture will be needed in the future as carbon dioxide levels continue to increase. It may also mean that plants in natural ecosystems that prefer nitrate over ammonium as a nitrogen source, will be at a competitive disadvantage in the future because of inhibition of nitrate uptake due to elevated carbon dioxide. The research is supported by BER.