Fig. 1.

Left panels: estimation of the effective parameters via regression analysis for the stomatal conductance models in eqns (5a) and (5b), the Ball–Berry model g₁ = m₁ f_cRH/c_a + b₁ (A) and the Leuning model g₂ = m₂ f_c[(1 + D/D₀)c_a]⁻¹ + b₂ (C) using gas exchange data collected under ambient (light circles) and elevated (heavy circles) c_a. The parameters m₁, m₂, b₁ and b₂, determined from linear regression analysis (lines), are shown in Table 1. Right panels: the distributions of m₁ and m₂ (B and D, respectively), computed with fixed b₁, b₂ and D_o, are shown for ambient and elevated c_a.