Cell wall thickness and composition are involved in photosynthetic limitation

The key role of cell walls in setting mesophyll conductance to
CO2 (gm) and, consequently, photosynthesis, is reviewed. First,
the theoretical properties of cell walls that can
affect gm are presented. Then, we focus on cell wall
thickness (Tcw) reviewing empirical evidence showing
that Tcw varies strongly among species and phylogenetic
groups in a way that correlates with gm and
photosynthesis i.e. the thicker the mesophyll cell walls, the
lower gm and photosynthesis. Potential interplays
of gm, Tcw, dehydration tolerance and hydraulic
properties of leaves are also discussed. Dynamic variations
of Tcw 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 gm are presented. We then propose a hypothetical
mechanism for the influence of cell walls on photosynthesis, combining the
effects of thickness and composition, particularly pectins. Finally, we
discuss the prospects for using biotechnology for enhancing photosynthesis
by means of altering cell wall-related genes.