A General Expression for the Control of the Rate of Photosynthetic CO2 Fixation by Stomata, the Boundary Layer and Radiation Exchange

Abstract

Previous descriptions of the “limitation” to the rate of photosynthetic CO2 assimilation imposed by the stornata and boundary layer have focused on the basic mechanism of CO2 diffusion and have made use of several simplifying assumptions regarding leaf temperature and transpiration rate. These descriptions are consequently useful under controlled conditions but, in the field, it is impossible to consider the role of the stornata and boundary layer in regulating CO2 uptake without considering their roles in controlling water and heat exchange and leaf temperature. In the following, we examine a complex leaf system that includes CO2, water and heat exchange and present expressions quantifying the degree to which each element of the system “limits” the rate of CO2 assimilation.