Bloom, A. J.; Smart, D. R.; Nguyen, D. T.: Elevated Carbon Dioxide Concentrations Inhibit Nitrate Assimilation in Wheat Shoots

Fluxes of CO₂ and O₂ from the shoots of wheat (Triticum aestivum) demonstrated that exposure to elevated CO₂ concentrations strongly inhibited shoot NO₃^– assimilation. Accordingly, elevated CO₂ concentrations enhanced shoot growth of wheat plants receiving NO₃^– nutrition to only half the extent of plants receiving NH₄⁺ nutrition, and elevated HCO₃^– concentrations interfered with the translocation of NO₂^– into wheat and pea chloroplasts. If CO₂ inhibition of NO₃^– assimilation were common among species, it would provide a mechanistic explanation for several responses of plants to elevated CO₂ including photosynthetic acclimation to CO₂, CO₂ inhibition of respiration, and intraspecific and interspecific variation in plant growth under elevated CO₂.