Fig. 3.

Light response curves of leaf CO₂ assimilation (A_n, in A–C) and stomatal conductance (g_s, in D–F) in field-grown coffee trees under actual (a[CO₂]) and elevated (e[CO₂]) air CO₂ concentration. Apparent quantum efficiency (α) is shown in (A) and (C). Measurements were taken in three canopy layers: 0–50 cm (L1, in C, F); 50–100 cm (L2, in B, E); >100 cm (L3, in A, D). Each symbol is the mean value of 10–17 replications (± s.e.). ** and different letters (in F) indicate statistical difference between [CO₂] treatments at at P < 0.01.