Diffusion and reaction of oxygen in the central tissue of ureide‐producing legume nodules

Abstract

ABSTRACTPrevious simulation models for the diffusion and reaction of oxygen in legume nodules were based on infected cells and neglected adjacent uninfected cells. This study uses a three‐dimensional model of the central zone of legume nodules made up of the two cell types represented by a geometrically defined, space‐filling, binary combination of polyhedra, each with bevelled edges to allow for a network of intercellular gas spaces. The model predicted a distinctively compartmentalized distribution of [O2] between uninfected and infected cells; with high O2 concentrations for an uninfected cell being consistent with, and necessary for, efficient operation of uricase and ureide synthesis and low O2 concentrations across most of the infected cell providing a suitable environment for N2‐fixation. Compartmentalization of O2 also predicted significant O2 fluxes between cell types, compromising maintenance of low [O2] in infected cells, as well as high [O2] in uninfected cells. The results predict that there might be significant resistance to O2 diffusion across the cell : cell interface due to the plasmalemma and cell walls.