Figure 2. (A) Diurnal root zone maximum, (B) minimum, and (C) diurnal temperature range (DTR). Treatments were all charcoal-filtered air (CF) with plants grown in the ground (G) or in 21-L containers (C) at current ambient (370 µmol CO₂ mol^–1 air) or elevated (700 µmol CO₂ mol^–1 air) CO₂ concentrations. All temperatures were measured at a depth of about 20 cm.