Vacuolar and cytoplasmic pH, ion composition, and turgor pressure in Lamprothamnium as a function of external pH

Ionic responses to alteration in external and internal pH were examined in an organism from a marine-like environment. Vacuolar pH (pH(v)) is about 4.9-5.1, constant at external pH (pH(o)) 5-8, while cytoplasmic pH (pH(c)) increases from 7.3 to 7.7. pH(c) regulation fails above pH(o) 9, and this is accompanied by failure of turgor regulation. Na(+) increases above pH(o) 9, while K(+) and Cl(-) decrease. These changes alone cannot however explain the alterations in turgor. Agents known to affect internal pH are also tested for their effect on ion relations.