The large central vacuole in plant cells serves several important functions. One of its primary roles is the storage of water, nutrients, and waste products. The vacuole helps maintain turgor pressure within the cell by storing water, which provides rigidity to the plant. Additionally, the vacuole stores various substances that may be waste products or substances needed for the cell's function, and it plays a role in regulating the internal environment of the cell.
Thus, the primary function of the central vacuole is the storage of water, nutrients, and waste products.