Mechanisms underlying CO2 diffusion in leaves.

Plants provide an excellent system to study CO(2) diffusion because, under light saturated conditions, photosynthesis is limited by CO(2) availability. Recent findings indicate that CO(2) diffusion in leaves can be variable in a short time range. Mesophyll CO(2) conductance could change independently from stomata movement or CO(2) fixing reactions and it was suggested that, beside others, the membranes are mesophyll CO(2) conductance limiting components. Specific aquaporins as membrane intrinsic pore proteins are considered to have a function in the modification of membrane CO(2) conductivity. Because of conflicting data, the mechanism of membrane CO(2) 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 CO(2) 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 CO(2) diffusion.
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