A new method to detect the presence of continuous gas-filled pathways for oxygen diffusion in legume nodules

A new method is presented which evaluates the contribution of gas-filled and water-filled pathways across the barrier which restricts O 2 diffusion into infected cells of nodules. Since O 2 will move through air about 104 times faster than through water any continuous gas-filled pathways which traverse the cortex would form a major route for O 2 transport. However, microscopic evidence for the existence of such direct connections is ambiguous. On theoretical grounds, O 2 should diffuse through a He atmosphere about 3.7 times faster than through air or Ar, but O 2 flux across a liquid barrier should be unaffected by changes in the background mixing gas