Microscale gas exchange modelling in leaves using combined gas diffusion and photosynthesis kinetics

Gas exchange in leaves is modelled using combined gas diffusion and photosynthesis kinetics in a 2D cellular structure of a wheat leaf. The microscale model for gas exchange accounted for diffusive mass transport of CO2 in the intercellular space (pores), the cell wall network and the intracellular liquid of cells. The photosynthesis kinetics described by the extended Farquhar, von Caemmerer & Berry model were coupled to the gas exchange inside the mesophyll cells. The coupled model was validated by means of gas exchange and chlorophyll fluorescence measurements. The theoretical model simulations revealed the microscale gas distribution and exchange rates in the leaf. Mesophyll cells that were exposed to air voids showed strong CO2 concentration gradients across the cell. These simulation results explained for the first time why the mesophyll conductance gm is dynamically changing in response to environmental conditions. Likewise, the microscale model provided detailed insight of stomatal conductance in response to changes in CO2 concentration and irradiance around leaves.