Its main function is storage. Vacuoles are found in the cytoplasm of most plant cells. They are membrane bound organelles, they perform functions of secretion, excretion and storage. Tonoplast: A vacuole that is surrounded by a membrane is called tonoplast.ell wall: The cell wall is a rigid layer that surrounds the plant cells. It is made up of cellulose. Cell wall is a characteristic feature to cells of plants. Plant cell walls are primarily made up of cellulose.