Mechanisms underlying CO2 diffusion in leaves

Plants provide an excellent system to study CO2 diffusion because, under light saturated conditions, photosynthesis is limited by CO2 availability. Recent findings indicate that CO2 diffusion in leaves can be variable in a short time range. Mesophyll CO2 conductance could change independently from stomata movement or CO2 fixing reactions and it was suggested that, beside others, the membranes are mesophyll CO2 conductance limiting components. Specific aquaporins as membrane intrinsic pore proteins are considered to have a function in the modification of membrane CO2 conductivity. Because of conflicting data, the mechanism of membrane CO2 diffusion in plants and animals is a matter of a controversy vivid debate in the scientific community. On one hand, data from biophysics are in favor of CO2 diffusion limiting mechanisms completely independent from membrane structure and membrane components. On the other, there is increasing evidence from physiology that a change in membrane composition has an effect on CO2 diffusion.