CO2 Diffusion Inside Photosynthetic Organs

Abstract

In the present chapter, we review the current state-of-the-art of knowledge on mesophyll (internal) CO2 diffusion conductance of photosynthetic tissues (for simplification, gm). We show that, despite concerns regarding the methodological approaches currently used for its estimation, a large and consistent body of evidence has accumulated showing that gm is finite and significantly limiting for photosynthesis, as well as being highly variable among photosynthetic organisms and in response to environmental changes. Part of this variation results from different anatomies of the photosynthetic tissues, with a particularly strong influence of chloroplast distribution and cell wall thickness. Besides these, it appears that a biochemical modulation of gm also occurs, likely involving aquaporins and, possibly, carbonic anhydrases and other metabolic components.