Worldwide Dataset Demonstrates Importance of CO2 Diffusion in Leaves on Photosynthesis


Oak Ridge National Laboratory scientists used worldwide datasets gathered through an online virtual laboratory for photosynthesis research (leafweb.ornl.gov) to determine the effects of CO2 diffusion inside leaves (i.e., mesophyll conductance) on photosynthesis across all major plant functional types and climates. Molded mesophyll conductance (gm) generally has been assumed to be infinitely large. Synthesis of LeafWeb data from over 130 C3 photosynthetic species in different countries showed that mesophyll conductance of most species is as important as stomatal conductance in affecting photosynthesis. The study found that standard assumptions of an infinite mesophyll conductance resulted in a major underestimation of CO2 assimilation capacities of the photosynthetic machinery and a distortion of relationships between key biochemical processes. Based on the study’s findings, a new functional model is proposed to facilitate the representation of mesophyll conductance in global carbon cycle models. This study will lead to better understanding of photosynthetic processes under natural conditions and development of better global carbon cycle models.  A virtual laboratory like LeafWeb is a cost effective, efficient tool for promoting international collaboration, collecting spatially distributed datasets of global importance, and conducting synthesis research that would otherwise be difficult to carry out.


Sun, Y., L. Gu, R. E. Dickinson, S. G. Pallardy, J. Baker, Y. Cao, F. M. DaMatta, X. Dong, D. Ellsworth, D. Van Goethem, A. M. Jensen, B. E. Law, R. Loos, S. C. Vitor Martins, R. J. Norby, J. Warren, D. Weston, and K. Winter. 2013. “Asymmetrical Effects of Mesophyll Conductance on Fundamental Photosynthetic Parameters and Their Relationships Estimated from Leaf Gas Exchange Measurements,” Plant, Cell and Environment, DOI:10.1111/pce.12213.