The part of the plant cell that stores water and dissolved materials is the vacuole.

Here's why:

* Storage: Vacuoles are large, fluid-filled sacs that act as storage compartments for water, nutrients, pigments, and waste products.

* Turgor Pressure: The water stored in the vacuole creates turgor pressure, which helps maintain the plant's shape and rigidity.

* Dissolved Materials: Vacuoles also hold dissolved materials like sugars, amino acids, and salts, which are essential for the plant's metabolic processes.

While other parts of the plant cell may store some substances, the vacuole is the primary storage organelle.