IS SODIUM PROTON ANTIPORT UBIQUITOUS IN PLANT-CELLS

Excised roots or storage tissue slices from 16 crop plant species were screened for the presence of a Na+/H+ antiporter at the plasma membrane and tonoplast of their cells. The pH-gradient dependent decrease of Na+ uptake by ATP-depleted tissues served as an indication for such antiport at the plasma membrane. Metabolic-energy dependent uptake by the tissues, in the presence of excess K+, indicated the functioning of Na+/H+ antiport at the tonoplast. Evidence for Na+/H+ antiport was found in four species and for its absence in five species. In seven species the evidence was not unequivocal. It was concluded that the presence of a Na+/H+ antiporter is not an ubiquitous characteristic of plant cells.