Figure 3.

(a) Net CO₂ assimilation rate (A_n) as a function of: (a) intercellular CO₂ partial pressure C_i (Pa) and varying V_cmax/J_max at constant leaf temperature of 25°C. (b) Net CO₂ assimilation rate as a function of leaf temperature T(°C) and varying V_cmax/J_max at constant ambient CO₂ partial pressure of 40 Pa. (c) Net CO₂ assimilation rate as a function of V_cmax/J_max and covarying leaf temperature T (°C) and intercellular CO₂ partial pressure C_i (Pa). Temperature was covaried with ambient [CO₂] according to a linear regression (r² = 0.992) between predicted future CO₂ increases and temperature anomalies derived from IPCC predictions (2013). In all simulations leaf nitrogen content was kept constant at 2 g N m⁻². The red broken line indicates optimal V_cmax/J_max ratio for each C_i or T, i.e. where A_n reaches the highest value and photosynthetic nitrogen use efficiency peaks.