The concentration of nitrogen (N) in vegetative tissues is largely dependent on the balance among growth, root N uptake, and N assimilation. Elevated CO2 (eCO2) 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 CO2 (400 or 700 ppm) and two temperature regimes (26/21 or 31/26 °C, day/night). Plant dry mass, plant %N, protein concentrations, NO3- and NH4+ root uptake rates (using 15NO3 or 15NH4), and whole-plant N- and NO3--assimilation were measured. Plant growth, %N, protein concentration, and root N-uptake rate were each significantly affected only by CO2, while N- and NO3--assimilation were significantly affected only by temperature. However, plants grown at eCO2 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 eCO2 and warming on wheat tissue N would be to target the maintenance of root N uptake rate at eCO2 and N assimilation at higher growth temperatures.
Keywords: 15N tracer; N assimilation; N uptake; Triticum; climate change; elevated CO2; heat stress; nitrogen metabolism; warming; wheat.