HOW OXYGEN INFLUX TO LEGUME ROOT-NODULES IS REGULATED - 4 TYPES OF CONTROL

Already known mechanisms and models are presented to describe the func tion of diffusion barriers in legume nodules and the conditions under which these mechanisms operate. The control over oxygen influx to nodu les is related to nodule structure. Four types of controls, which are set apart for regulating the barrier function with distinct periods an d mechanisms of functioning, satisfactorily match the experimental evi dence. The general pattern of the oxygen concentration gradient is put forward to describe oxygen flow from the rhizosphere to infected nodu le cells.