Effects of Elevated Carbon Dioxide and Chronic Warming on Nitrogen (N)-Uptake Rate, -Assimilation, and -Concentration of Wheat

The concentration of nitrogen (N) in vegetative tissues is largely dependent on the balance among growth, root N uptake, and N assimilation. Elevated CO(2) (eCO(2)) plus warming is likely to affect the vegetative-tissue N and protein concentration of wheat by altering N metabolism, but this is poorly understood. To investigate this, spring wheat (Triticum aestivum) was grown for three weeks at two levels of CO(2) (400 or 700 ppm) and two temperature regimes (26/21 or 31/26 °C, day/night). Plant dry mass, plant %N, protein concentrations, NO(3)(−) and NH(4)(+) root uptake rates (using (15)NO(3) or (15)NH(4)), and whole-plant N- and NO(3)(-)-assimilation were measured. Plant growth, %N, protein concentration, and root N-uptake rate were each significantly affected only by CO(2), while N- and NO(3)(−)-assimilation were significantly affected only by temperature. However, plants grown at eCO(2) plus warming had the lowest concentrations of N and protein. These results suggest that one strategy breeding programs can implement to minimize the negative effects of eCO(2) and warming on wheat tissue N would be to target the maintenance of root N uptake rate at eCO(2) and N assimilation at higher growth temperatures.