Turgor pressure
Encyclopedia
Turgor Pressure or turgidity is the main pressure of the cell
contents against the cell wall
in plant cell
s and bacteria cells, determined by the water content of the vacuole
, resulting from osmotic pressure
, i.e. the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane
due to a differential in the concentration of solute.
Turgor Pressure is a force per unit area exerted outward on a plant cell wall by the water contained in the cell vacuole
. In terms of plant water potential
, turgor pressure is usually expressed as the pressure component (
). This force gives the plant rigidity, and keeps it erect.
. When this happens, cells are no longer rigid and the plant loses structure, giving the "wilty" appearance. Wilting might not always be caused by a lack of water, but might be an expression of plants under salt (salinity) stress or can be caused by ethylene (a plant hormone).
"Plants wilt, not only when they lose water through evaporation, but also when they are surrounded by an aqueous solution of common salt, potassium chloride, magnesium chloride, sugar or other substance, if the solution is of higher osmotic pressure
, whereas they do not wilt if the kinetic pressure is lower."
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
contents against the cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
in plant cell
Plant cell
Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic organisms. Their distinctive features include:...
s and bacteria cells, determined by the water content of the vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
, resulting from osmotic pressure
Osmotic pressure
Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....
, i.e. the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane
Semipermeable membrane
A semipermeable membrane, also termed a selectively permeable membrane, a partially permeable membrane or a differentially permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion".The rate of...
due to a differential in the concentration of solute.
Turgor Pressure is a force per unit area exerted outward on a plant cell wall by the water contained in the cell vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
. In terms of plant water potential
Water potential
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension...
, turgor pressure is usually expressed as the pressure component (
). This force gives the plant rigidity, and keeps it erect.Wilting
Plants that lose turgidity (lose water from their cells) undergo plasmolysisPlasmolysis
Plasmolysis is the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis. The reverse process, cytolysis, can occur if the cell is in a hypotonic solution resulting in a higher external osmotic pressure and a net flow of water into the cell...
. When this happens, cells are no longer rigid and the plant loses structure, giving the "wilty" appearance. Wilting might not always be caused by a lack of water, but might be an expression of plants under salt (salinity) stress or can be caused by ethylene (a plant hormone).
"Plants wilt, not only when they lose water through evaporation, but also when they are surrounded by an aqueous solution of common salt, potassium chloride, magnesium chloride, sugar or other substance, if the solution is of higher osmotic pressure
Osmotic pressure
Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....
, whereas they do not wilt if the kinetic pressure is lower."
Further reading
- Campbell, N. A., Reece, J. B. Biology: Sixth Edition; Benjamin Cummings: New York, NY, 2002; Vol. 1.