The part of a cell that stores water, ions, and wastes, and is found in both animal and plant cells (though larger in plant cells), is the vacuole.

Here's why:

* Water storage: Vacuoles are like storage tanks within the cell, holding a large amount of water. This is especially important in plant cells, where the vacuole contributes to turgor pressure, which helps maintain the plant's rigid structure.

* Ions: Vacuoles also store various ions, which are important for maintaining the cell's pH and overall ion balance.

* Wastes: While the cell has other mechanisms for waste removal, the vacuole can temporarily store some cellular waste products.

Important note: While both animal and plant cells have vacuoles, plant vacuoles are typically much larger and play a more prominent role in the cell's overall function.