Turgor, “the state of turgidity and resulting rigidly of cells or tissues, typically due to the absorption of fluid.” You see, plant cells have high concentrations of molecules in their cytoplasm, or jelly like fluid, which causes water to enter the cell under normal conditions. This causes the central vacuole, the storage structure, to swell and press against the cell wall. With a now healthy supply of water, turgor pressure keeps plant from wilting. So the answer to your question would be central vacuole.
