Vacuoles

Generally vacuoles (except food vacuoles) are nonprotoplasmic liquid filled cavities in the cytoplasm and are surrounded by a membrane called the Tonoplast. The tonoplast is selectivity permeable, it allows certain substances to enter in the vacuole. In animals cells they are temporarily formed at the time of their need. These are conspicuous organelles of plant cells. They are more prominent in mature cells, whereas less prominent in immature cells. THey vacuoles in plant cells, are filled with cell sap and act as store house, which often plays role in plant defence, which is necessary for plant cell enlargement. In animal cells, vacuoles are rich in hydro lytic enzymes, including proteases, ribonucleases and glycosidases. Plant vacuoles sometimes act as lysosome as they contain hydro lytic enzymes and after death of cells tonoplast lose its differential permeability and its enzymes causes lysis of the cell.