Fig. 5.

Correlations between leaf CO₂ assimilation (A_n) and instantaneous carboxylation efficiency (CE, in A) and between A_n and stomatal conductance (g_s, in B) in field-grown coffee trees under actual (a[CO₂]) and elevated (e[CO₂]) air CO₂ concentration. Measurements were taken in three canopy layers: 0–50 cm (triangles); 50–100 cm (circles); >100 cm (squares). Each symbol is the mean value of 10–17 replications (± s.e.). In (B), the correlations are represented by the following equations: a[CO₂] – L1, y = 274.29x – 3.31, r = 0.94, P = 0.004; L2, y = 390.71x – 3.12, r = 0.95, P = 0.003; L3, y = 482.30x – 5.34, r = 0.90, P = 0.014; e[CO₂] – L1, y = 316.72x – 6.25, r = 0.62, P = 0.191; L2, y = 532.96x – 10.65, r = 0.96, P = 0.002; L3, y = 868.07x – 23.34, r = 0.94, P = 0.005.