Turgor pressure is the pressure that water in a cell exerts on cell walls. It is a vital process in plants that makes the plant cell stiff and rigid, providing the needed turgidity and rigidity that could help them stay upright against the force of gravity while poising themselves toward the source of light. Turgor pressure is caused by the osmotic flow of water and occurs in plants, fungi, and bacteria. It is regulated by osmosis, and this also causes the cell wall to expand during growth. Along with size, rigidity of the cell is also caused by turgor pressure; a lower pressure results in a wilted cell or plant structure (i.e. leaf, stalk).

Turgor pressure is also important in stomate formation. The turgid guard cells create an opening for gas exchange. Carbon dioxide could enter and be used for photosynthesis. Other functions of turgor pressure in plants include apical growth, nastic movement, and seed dispersal. Turgor pressure is responsible for apical growth of features such as root tips and pollen tubes. In fruits such as Impatiens parviflora, Oxalia acetosella, and Ecballium elaterium, turgor pressure is the method by which seeds are dispersed. In Ecballium elaterium, or squirting cucumber, turgor pressure builds up in the fruit to the point that it aggressively detaches from the stalk, and seeds and water are squirted everywhere as the fruit falls to the ground.

Turgor pressure is also a large factor for nutrient transport throughout the plant. Cells of the same organism can have differing turgor pressures throughout the organisms structure. Turgor pressure can play a large role in the development, movement, and nature of other organisms besides plants.