A preliminary model of photosynthesis and growth of field crops was developed to assess the effects of gaseous pollutants, particularly airborne sulfur compounds, resulting from energy production from geothermal resources. The model simulates photosynthesis as a function of such variables as irradiance, CO/sub 2/ diffusion resistances, and internal biochemical processes. The model allocates the products of photosynthesis to structural (leaf, stem, root, and fruit) and storage compartments of the plant. The simulations encompass the entire growing season from germination to senescence. The model is described conceptually and mathematically and examples of model output are provided for various levels of pollutant stress. Also, future developments that would improve this preliminary model are outlined and its applications are discussed.