Figure 2.

The isotopic composition (‰) of the water at the site of evaporation (δ_e) and the oxygen isotope discrimination (Δ¹⁸O) as a function of the rate constant of leaf CA (k_CA mol m⁻² s⁻¹ Pa⁻¹). Values of δ_e were calculated as described in the text using Equation 1 and source water (δ_s) was −5.3 ± 0.3‰. The line represents a linear regression (R² = 0.87) for all data except the plants with high Δ¹⁸O values. Symbols and gas exchange conditions are as in Figure 1 and δ values are expressed in reference to VSMOW.