Presence of vacuole is the character of plant cell. Vacuoles are liquid filled cavity. The liquid contains watery solution of many inorganic ions such as : K, Cl, Mg, etc and many organic substances such as Sugar,protein,organic acid, fatty acid and some gases. All these are collectively called cell sap. It maintain the osmotic pressure of the cell. The vacuole is surrounded by the thin membrane called vacuolar membrane.
In young cell dividing cells vacuoles are small, many and scattered throughout in the cytoplasm while in mature cell there is single large vacuoles in each cell.