A Semiphenomenological Model for Stomatal Gas Transport

Ordinary diffusion of gases from (or into) a sub-stomatal cavity through a stomatal pore into (or from) the ambient air is considered. The formulation of molar flux densities for trace components (CO2 and e.g. gaseous pollutants) is based on the use of the effective diffusion coefficient and the coupling between transport of water vapour is included. System geometry is simplified and the semiphenomenological, analytical molar flux expressions are presented in terms of the concentration difference between the cavity and the ambient air. The correction factors for the influence of a steady wind and the interference between pores are derived. The interference is found to be important once stomata were not almost closed. The wind reduces the interference. The direct effect of water vapour diffusion on the transport of trace gases is shown to be marginal.