Ion channels in vacuoles from halophytes and glycophytes

AbstractThe electrical properties of the vacuolar membrane (tonoplast) of a halophyte, sugar beet, and a glycophyte, tomato, have been investigated using the patch-clamp technique [(1981) Pflügers Arch. 391, 85–100]. Voltage-dependent ion channels were analyzed using isolated membrane patches. Both species displayed channel activities which were nonselective between sodium and potassium. Beet tonoplast channels displayed inward rectification (65 pS and 10 pS for negative and positive potentials, respectively), while tomato tonoplast channels showed a constant conductance (25 pS) in the range −80 to +80 mV potentials. The observed low channel conductance at positive potentials in halophytes would prevent a significant loss of the Na+ accumulated in the vacuole through the operation of the Na+/H+ antiport [(1987) Physiol. Plant. 69, 731–734], while channel rectification in glycophytes would have no physiological significance