CO2 diffusion in tobacco: a link between mesophyll conductance and leaf anatomy (Interface Focus)

Three key factors affect a plant’s ability to fix carbon: enzymatic activity of Rubisco, stomatal conductance, and the journey from sub-stomatal cavity to Rubisco, also known as mesophyll conductance (gm). This latter is the focus of this new work by Clarke et al. They delightfully compare this journey to that of Princess Leia from Star Wars (see the adjoining illustration; the CO2 molecule works surprisingly well as her head and hair). Here, the authors address how leaf age and leaf position in the canopy affect gm, with the objective of improving models of photosynthesis. To do this, they measured carbon isotope discrimination, gas exchange, Rubisco activity, and leaf anatomy. They found that gm decreases with leaf age, which can largely be attributed to a corresponding increase in cell wall thickness and a decrease in exposure of chloroplasts to intercellular airspace. (Summary by Mary Williams @PlantTeaching) Interface Focus 10.1098/rsfs.2020.0040