Sodium, Potassium, Chloride, and Betaine Concentrations in Isolated Vacuoles from Salt-Grown Atriplex gmelini Leaves

Vacuoles were isolated via protoplasts from the leaves of a halophyte Atriplex gmelini C.A.Mey., grown in culture solution supplemented with 250 millimolar NaCl. Lysis of the protoplasts was induced by lowering the medium osmolarity (1.2 to 1.0 molar sorbitol) and adding a detergent, a synthesized cholate derivative, 3-([3-cholamidopropyl] dimethylammonio)-1-propanesulfonate at a concentration of 0.5 millimolar and the resulting vacuoles were purified by successive dilution and floatation. Isolated vacuoles contained almost the same concentration of sodium (569 millimolar) and chloride (260 millimolar) as recorded in protoplasts (582 and 254 millimolar, respectively), suggesting that the vacuoles are the major sequestration site of NaCl in leaves of halophytes. Betaine concentration in the protoplasts was about 16 millimolar, while that in vacuoles was only about 0.24 millimolar, indicating that betaine is accumulated in the cytoplasm as a compatible solute.