View article

The key role of cell walls in setting mesophyll conductance to CO₂ (g_m) and, consequently, photosynthesis is reviewed. First, the theoretical properties of cell walls that can affect g_m are presented. Then, we focus on cell wall thickness (T_cw) reviewing empirical evidence showing that T_cw varies strongly among species and phylogenetic groups in a way that correlates with g_m and photosynthesis; that is, the thicker the mesophyll cell walls, the lower the g_m and photosynthesis. Potential interplays of g_m, T_cw, dehydration tolerance, and hydraulic properties of leaves are also discussed. Dynamic variations of T_cw in response to the environment and their implications in the regulation of photosynthesis are discussed, and recent evidence suggesting an influence of cell wall composition on g_m is presented. We then propose a hypothetical mechanism for the influence of cell walls on photosynthesis, combining the …