Diurnal leaf photosynthesis simulation with a constant boundary layer conductance in a greenhouse.
Steady state leaf photosynthesis simulation with vertical profile of environmental variation in a field crop canopy.
Model schematic
Figure description model: Schematic representation of the leaf-level processes governing heat and gas exchange, integrating a leaf photosynthesis model, an energy balance model, and a stomatal conductance model parametrized at the leaf surface rather than ambient air. The figure illustrates how CO₂ and water vapour move through different compartments, from ambient air to the chloroplast and vice versa, as well as the key physiological parameters affecting these fluxes. Photosynthesis (A) and transpiration (E) are influenced by environmental inputs and the diffusion of CO2 is controlled by the boundary layer conductance (g_b), stomatal conductance (g_s) and mesophyll conductance (g_m), while water vapour exchange is driven by vapour pressure gradients in the intercellular airspace (e_i), the leaf surface (e_s) and in the surrounding air (e_a). The model incorporates photosynthetic and stomatal parameters to predict gas exchange responses to environmental conditions under different boundary layer conductances. Legend: Inputs (climatic variables) are represented with closed circles, while model parameters are shown with open circles. Flows, depicted as solid arrows, indicate substance movement, whereas flow variables describe the rate of change within the system. Level variables, such as CO₂ and H₂O, represent concentrations that change over time due to inflows and outflows. Information channels, illustrated with dashed arrows, convey non-material influences like feedback mechanisms and regulatory processes. Abbreviations: Input: absorbed photosynthetically active radiation (PAR), ambient pressure (Pa) was omitted for clarity, air temperature (T_air), ambient CO2 concentration (C_a), reflected temperature (Trefl); Concentrations and deficits: intercellular CO2 concentration (C_i), surface CO2 concentration (C_s), ambient CO2 concentration (C_i), surface H2O vapour concentration (e_s), ambient H2O vapour concentration (e_a), intercellular H2O vapour concentration (e_i) assumes the leaf to be saturated, leaf vapour pressure deficit surface (D_s); Conductances: mesophyll conductance (g_m), stomatal conductance (g_s), boundary layer conductance (g_b), Rates: photosynthesis (A), transpiration (E); Photosynthetic parameters: maximum carboxylation velocity (〖Vc〗_max), light-saturated potential rate of electron transport (J_max), dark respiration rate (R_d), CO2 compensation point in the absence or presence of R_d (Γ^*,Γ), Michaelis constant CO2 or O2 (K_c,K_o), curvature of J/PAR (Curv); Stomatal parameters: nocturnal stomatal conductance (g_0), slope of A/g_s (g_1), sensitivity factor D_s response (D_s 0); Others: leaf temperature (T_leaf), conversion factor from PAR to W m-2 (k_SUN).