4:	Mathematical Plant: Photosynthesis - modeling leaf photosynthesis using a spreadsheet-based computer program.

Authors:	Murphy, Terence, M.(A)Bestman, Hank, D.(B)
Affiliations:	(A): University of California (B): The King
Presenter:	Bestman, Hank D., hbestman@kingsu.ab.ca

The embedding of the Visual Basic for Applications (VBA) development language in Microsoft Excel (97) facilitates the use of this spreadsheet program for complex modeling purposes. The Mathematical Plant: Photosynthesis modeling program is based on the PGEN v2.0 model (Friend, A.D. 1995. PGEN: an integrated model of leaf photosynthesis, transpiration, and conductance. Ecological Modeling 77:233-255). The user interface to the model allows for varying the following input parameters: photosynthetically active radiation, CO2 concentration, air temperature, relative humidity, and windspeed. Any one of these five parameters can be a range of values, while the remaining four are limited to a single value. Based on the supplied values or particular range of values of the input parameters, the model calculates the following eleven output parameters: stomatal conductance, net photosynthesis, water use efficiency, transpiration rate, leaf temperature, leaf water potential, carboxylation-limited rate of photosynthesis, RUBP regeneration-limited rate of photosynthesis, electron transport rate, CO2 concentration in the leaf air spaces, and the ratio of internal to external to leaf boundary CO2 concentration. Any combination of four of these eleven output parameters can be displayed graphically on the computer screen, allowing for easy comparison and interpretation. The results of a particular simulation can be printed or saved to a file.