Turgor pressure is exerted by the fluid inside the cell on the cell wall. It pushes the plasma membrane against the cell wall due to the osmotic flow of water through the permeable membrane. As it acts inside the cell to outside it is positive hydrostatic pressure, which is opposed by equal and opposite wall pressure (negative pressure). Diffusion is the movement of particles of gases, liquids, and solids from a region of higher free energy to a region of lower free energy. It is more rapid in gases, as compared to liquids as the density of gases is lower than that of liquids. Imbibition is the absorption of water by solid particles of an adsorbent substance without forming a solution.