Most plant cells live in a hypotonic environment because there is a low concentration of solutes in extracellular fluids than in their cells. As a result, water tends to move first inside the cell and then inside the vacuole. When the vacuole increases in size the cytoplasm presses firmly against the interior of the cell wall, which expands a little. Due to the strong cell wall, plant cell does not rupture but instead becomes rigid. The internal pressure of such a rigid cell is known as turgor pressure and this phenomenon is known as turgor.