The problem faced by plant cells to maintain their water quantity.

Environment can never be same as the environment inside the cell. So plant cells have a lot of problems to maintain the water quantity.

Water balance problems are somewhat different for plant cells because of the presence of rigid cell walls. In a hypotonic environment, water enters inside the cell and then into vacuole. When vacuole increases in size the cytoplasm presses firmly against the interior of cell wall, which expands a little. Plant cell becomes rigid. The internal pressure of such a rigid cell is known as Turgor pressure and process is called Turgor.

In isotonic environment the plant cell is flaccid (loose / not firm), because the net uptake of water is not enough to make it turgid.

In hypertonic solution, Water is released from the cell and because shrinkage of the cytoplasm but not of cell wall. This shrinkage of cytoplasm is called Plasmolysis.