Turgor (cellular turgidity)

Turgor is the pressure exerted by fluid inside living cells or tissues that makes them firm. It is central to plant rigidity, growth, stomatal function and responses to water availability.

Overview

Turgor refers to the swollen, pressurized condition of living cells or tissues caused by the uptake and retention of water. In simple terms it is the internal hydrostatic pressure that presses the plasma membrane against the cell wall, making non-woody plant organs rigid and maintaining form in many microorganisms and cells. The concept applies across biological scales, from single cells to whole tissues.

How turgor is generated

Turgor arises when water enters a cell by osmosis because the cell interior has a higher solute concentration than the surrounding fluid. Water fills the central vacuole in many plant cells, raising the internal pressure (turgor pressure) until it balances the tendency for further influx. Structural elements such as the cell wall constrain expansion and convert that influx into mechanical stiffness. The process is closely related to water potential and osmotic gradients; changes in external or internal solute levels alter turgor.

Functions and examples

Turgor underpins several important plant functions: it keeps leaves and stems erect, enables rapid movements (for example in some carnivorous plants and closing of stomata), and contributes to cell expansion during growth. Loss of turgor leads to wilting and reduced growth. In horticulture and agriculture, watering and soil salinity affect turgor and therefore crop performance. More broadly, single-celled algae and bacteria also rely on turgor for shape and sometimes motility.

Measurement, management and significance

Researchers and growers assess turgor indirectly by observing wilting or directly with instruments that measure water potential and pressure. Maintaining favorable water availability preserves turgor; conversely, drought, high salinity or freezing can reduce it. Concepts like turgor loss point are used in plant physiology to evaluate drought tolerance. Practical management includes irrigation, mulching and soil amendment to support steady water uptake and prevent osmotic stress.

History, terminology and distinctions

The word turgor derives from terms meaning swollen or inflated and has been part of botanical and cellular vocabulary for centuries. It is distinct from osmotic pressure (a chemical potential difference driving water) and from external hydrostatic pressure; turgor is the resulting mechanical pressure inside a living cell. When a cell loses water and the membrane pulls away from the wall, this is called plasmolysis, a visible sign of turgor loss.