Turgor pressure

Turgor pressure is the force exerted by a cell’s contents against its enclosing membrane or wall. In plants, water entering the vacuole presses the plasma membrane against the cell wall, helping tissues stay firm.

Osmosis: The net movement of water across a selectively permeable membrane toward a region of lower water potential. Water entering a plant cell by osmosis raises internal pressure against its wall.
Stomatal movement: The opening and closing of pores in the leaf epidermis through changes in guard-cell shape. Guard cells open stomata when their turgor rises and close them as it falls.
Plasma membrane: A selectively permeable lipid bilayer surrounding a cell and regulating exchange with its environment. The membrane encloses the cell contents and transmits their pressure to the surrounding wall.
Turgidity: The firm, swollen state of a cell or tissue caused by high internal water pressure. Turgidity is the resulting cell state; turgor pressure is the force contributing to it.
Vacuole: A membrane-bound compartment in a cell that stores water, ions, and other substances. The large central vacuole expands with water and presses the cytoplasm toward the cell wall.
Wilting: The drooping of plant organs when water loss reduces tissue firmness. Wilting is a visible consequence of cells losing enough turgor to support leaves and stems.
Cell wall: A structural layer outside the plasma membrane that supports and protects cells in many organisms. Plant turgor is commonly discussed as pressure contained by this broader class of cellular enclosure.
Turgor loss point: The water status at which a plant cell or tissue loses positive turgor pressure. This threshold marks when water deficit removes the pressure that keeps tissues firm.
Plant cell wall: A stiff extracellular layer, composed mainly of cellulose in plants, that surrounds the plasma membrane. Its resistance to expansion turns water uptake into pressure rather than unlimited cell swelling.
Nastic movement: A plant movement whose direction is independent of the direction of the stimulus. Rapid turgor changes power movements such as leaf folding in sensitive plants.

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