Theoretical Considerations when Estimating the Mesophyll Conductance to CO2 Flux by Analysis of the Response of Photosynthesis to CO2

The conductance for CO2 diffusion in the mesophyll of leaves can limit photosynthesis. We have studied two methods for determining the mesophyll conductance to CO2 diffusion in leaves. We generated an ideal set of photosynthesis rates over a range of partial pressures of CO2 in the stroma and studied the effect of altering the mesophyll diffusion conductance on the measured response of photosysnthesis to intercellular CO2 partial pressure. We used the ideal data set to test the sensitivity of the two methods to small errors in the parameters used to determine mesophyll conductance. The two methods were also used to determine mesophyll conductance of several leaves using measured rather than ideal data sets. It is concluded that both methods can be used to determine mesophyll conductance and each method has particular strengths. We believe both methods will prove useful in the future.