3:	Mathematical Plant: Transpiration - modeling transpiration 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

Modeling the rate of transpiration of a typical plant under a variety of environmental conditions has been implemented using a Microsoft Excel (97) spreadsheet. This software provides the advantages of both spreadsheet software and visual programming tools because it embeds the Visual Basic for Applications (VBA) development language. As such it provides the highest level of user-programmable access to data analysis functions available in a spreadsheet. The interface of Mathematical Plant: Transpiration allows the user to vary the following environmental parameters: air temperature, photosynthetically active radiation, relative humidity, wind velocity, and soil water potential. The program automatically calculates the resulting transpiration rate, stomatal conductance, leaf temperature, and the water potential of leaf and root as a function of time and it presents the results graphically. In addition the contribution of the various components of the leaf heat balance are presented and their cumulative effect on leaf temperature can be assessed. The results of a particular simulation can be printed or saved to a file. The computer program has been used successfully in an introductory plant physiology course.