Fig. 1.

Schematic of the diffusion of gas exchange between the leaf and atmosphere compared to the conceptual version used in the model. The total conductance to water vapour (g_t) controlling the gradient of H₂O from leaf to atmosphere was composed by the stomatal conductance (g_s) and the boundary layer conductance (g_b). The gradient of CO₂ from the atmosphere to the site of carboxylation was also dependent on mesophyll conductance (g_m). The H₂O concentrations inside and outside the leaf were represented by e_s and e_a respectively. The CO₂ concentrations in three compartments were considered: in the atmosphere (C_a), in the intercellular airspaces (C_i) and at the sites of carboxylation (C_c). The different compartments of the leaf were represented as a standardized volume defined by the thickness of the intercellular airspace (d_a) and the photosynthetic tissues (d_p).