Review: Mesophyll conductance: walls, membranes and spatial complexity (New Phytol.)

There’s been a lot of talk lately about how to improve the carboxylation efficiency of Rubisco, but of course this also depends on how much CO₂ reaches the enzyme within the chloroplasts. To do so, it needs to pass through several distinct barriers: the boundary layer to reach the leaf surface, the stomatal pore, and then move within the leaf and into the mesophyll cell chloroplasts. In this Tansley Review, John Evans focusses on factors that affect this latter part, mesophyll conductance; these factors include cell walls and membranes.  He addresses the molecular basis for differential mesophyll conductance, including wall composition and aquaporins, which are membrane channels that facilitate CO₂ diffusion. He also addresses the feasibility of quantifying these factors through experimental and genetic studies as a basis to increase mesophyll conductance and to improve modeling towards the goal of improved photosynthesis. This is an exceptionally thorough and well-written review; instructors, consider adding it to your course reading list. (Summary by Mary Williams @PlantTeaching) New Phytol. 10.1111/nph.16968