What is the relationship between the flow of water into the cell and the maintenance of its shape?

Water is the main part of the cytoplasm and cell sap. Consider a plant cell as an example. These cells have vacuoles. These organelles contain the cell sap, which is 97% water. When the ambient temperature is high, the vacuoles lose cell sap. It is vaporized and used by the cell. From this, the cell loses its shape and, accordingly, the foliage looks sluggish. The same goes for plants that lack water in the soil. But when water comes in, the amount of cell sap is restored and the cells return to their normal shape.