The Function of a Vacuole in a Cell

Among the features that distinguish plant cells from animal cells is the vacuole, a large membrane-enveloped sac found in cells of plants but not animals. Young plant cells often have more than one vacuole, but these vacuoles fuse to form a single organelle as the cell grows.

Typically the central vacuole will be the largest compartment in a plant cell seen under the microscope. Vacuoles serve primarily as storage units but are versatile and can perform more than one function.

Plants use vacuoles to store food, like proteins that seeds will need in order to germinate. They also break down or store certain wastes in the vacuole -- plants, unlike animal cells, do not have lysosomes. Plants pump ions like potassium and chloride into vacuoles as well. This keeps the concentration of dissolved substances in the vacuole and in the cell's cytoplasm at the correct level to maintain turgor pressure, the osmotic pressure caused by the difference in solute concentration both inside and outside the cell.

Plants also use vacuoles to store pigments that lend color to the cells, like the bright colorful pigments that distinguish flower petals from the rest of the plant and help attract pollinators. Many plants use vacuoles for defense by storing poisonous or foul-tasting compounds in them; herbivores that eat the plant, if they live, learn to avoid doing so in future.