Figure 2.

NO₃⁻ and organic N concentration (milligrams per grams dry weight [mg g_DW^–1]) in the shoot (top left) and root (bottom left) and shoot δ¹⁵N (‰) of organic N (right) for Arabidopsis (A) and wheat (B) receiving NO₃⁻ or NH₄⁺ and exposed to one of four CO₂ treatments: ambient during the day and night (390/390 µmol mol⁻¹), ambient during the day and elevated at night (390/720 µmol mol⁻¹), elevated during the day and ambient at night (720/390 µmol mol⁻¹), or elevated during the day and night (720/720 µmol mol⁻¹). Shown are the mean ± se (n = 8–10). Bars and symbols for one species labeled with different letters differed by P < 0.10.