Cell wall properties in <i>Oryza sativa</i> influence mesophyll <scp>CO</scp> ₂ conductance

Abstract

Summary Diffusion of CO 2 from the leaf intercellular air space to the site of carboxylation ( g m ) is a potential trait for increasing net rates of CO 2 assimilation ( A net ), photosynthetic efficiency, and crop productivity. Leaf anatomy plays a key role in this process; however, there are few investigations into how cell wall properties impact g m and A net . Online carbon isotope discrimination was used to determine g m and A net in Oryza sativa wild‐type ( WT ) plants and mutants with disruptions in cell wall mixed‐linkage glucan ( MLG ) production ( CslF6 knockouts) under high‐ and low‐light growth conditions. Cell wall thickness ( T cw ), surface area of chloroplast exposed to intercellular air spaces ( S c ), leaf dry mass per area ( LMA ), effective porosity, and other leaf anatomical traits were also analyzed. The g m of CslF6 mutants decreased by 83% relative to the WT , with c . 28% of the reduction in g m explained by S c . Although A net / LMA and A net /Chl partially explained differences in A net between genotypes, the change in cell wall properties influenced the diffusivity and availability of CO 2 . The data presented here indicate that the loss of MLG in CslF6 plants had an impact on g m and demonstrate the importance of cell wall effective porosity and liquid path length on g m .