How does the large central vacuole in plants maintain homeostasis?

Maintaining acidity- In case the pH in the environment drops a lot (becomes very acidic), there is a flux of H ions from the cell's cytoplasm into the cell's vacuole thereby increasing acidity to required level and thus maintaining the specific pH in the cells internal environment as well.

Turgidity- Vacuoles regulate the turgidity by regulating the amount of water inside the cell. 
cell has excessive water: vacuole absorbs the water and then diffuses it out of the cell.
cell lacks water: water from the vacuole gets passed back into the cell thereby maintaining turgidity. 

And here's a video https://youtu.be/3tqjITi8S8s