This cell is wanted for storing food or nutrients in animal and plant cells. But they are much larger in plant cells. They also store waste so the cell doesn't get contaminated, and help the plants grow.
Vacuoles are the largest organelle in plant cell and they look like fluid filled sacs.
The tonoplast, is the membrane of the vacuole. It helps separate the contents of the vacuole from the contents of the cytoplasm. It also keeps harmful substances from getting out of the vacuole. It offers support to leaves and other soft structures.
SOURCES http://plantcellsorganelles.weebly.com/ Biology4Kids.com: Cell Structure: Vacuoles