In mature plant cells, like the staminal hair cells of Tradescantia, the vacuole occupies almost all of the cell volume. It contains the cell sap; the substances dissolved in the sap are responsible for the osmotic potential of the cell.
Sources
Protoplasmaströmung. O. KIERMEYER. W. URL. H.-K. GALLE. Publ.: 1979. Col., com. ger. or engl., 99 m, 9 min. 200 µm; DIC; 24 f/s. IWF, Göttingen: C 1295
