PHOTOBIO: Modeling the Stomatal and Biochemical Control of Plant Gas Exchange

Simulation models are increasingly being used to describe physiological processes in the plant sciences. These models, while useful for research purposes, also offer tremendous potential for demonstrating a wide array of scientific concepts to students. We have developed an educational software package that illustrates the stomatal and biochemical control of transpiration and photosynthesis. The simulation program uses a biochemical model of C assimilation that, when coupled to an empirical submodel describing stomatal conductance, can be solved iteratively for leaf photosynthesis, stomatal conductance, and transpiration. Graphic and tabular presentations, combined with on-screen requests for student input, serve to effectively convey the basic fundamentals of plant gas-exchange, and the diurnal patterns of photosynthesis and transpiration in response to fluctuating environmental conditions. More advanced topics focus on the biochemical limitations imposed on photosynthesis by Rubisco activity, electron transport capacity, and the regeneration of inorganic P. Also included is an exercise that challenges students to use the lessons learned to optimize C assimilation, while minimizing water losses, over a 3-d simulation period. Application of the program can assist instructors in illustrating important concepts regarding stomatal and biochemical control of plant gas-exchange.