Salt transport in Valonia: inhibition of potassium uptake by small hydrostatic pressures.

Internally perfused cells of the marine alga Valonia actively transport potassium from external seawater into the cell vacuole. This active uptake of potassium is reduced by restoring the normal turgor pressure of 1 atmosphere by means of a mercury manometer attached to the internal perfusion system. This inhibition of salt uptake by a small hydrostatic pressure suggests that Valonia and other walled cells may regulate their turgor pressures by adjusting their rates of salt uptake.