Plant cells can survive in a wide range of osmotic concentrations in comparison with the animal cell, because of the presence of cell wall which is rigid. When the cells are placed in water or hypotonic solutions, they absorb water and increase their size. As a result, the elastic plasma membrane presses the cell wall. The pressure that is built up by the cytoplasmic membrane is called the turgor pressure.
Turgor pressure will be maximum when the cell is not flaccid i.e., when solvent concentration is maxiumum inside the cell. When the cell has less solvent (as it happens when it is placed in a medium of hypertonic solution), the membrane will not press the cell wall and turgor pressure is lowest at that time. When the cell membrane is applying a pressure, the cell wall being rigid, (in order not to burst and retain the shape), also applies an equal amount of pressure in the opposite direction. This is known as the wall pressure.