Turgor pressure is hydrostatic pressure generated in plant cells and the cells of bacteria as a result of the uptake of water by osmosis. Water diffuses through the semipermeable membrane of the cell, causing the cell to swell; the increase in volume is resisted by the limited elasticity of the cell wall, which generates the pressure, similar to the way in which pumping air into a bicycle tire causes it to become stiff and resist squeezing. Turgor pressure supports non-woody plants. When water is lost, a plant's cells collapse, and it wilts.