The Turgor Is the phenomenon of total expansion of a cell when it is swelled by the pressure of the fluids. Through this phenomenon, the cells swell to absorb water, exerting pressure against the cell membranes, tightening them.
When the fluid exerts pressure outwardly on the cell wall it is called a turgor pressure. Whereas, the inward pressure exerted on the contents of the cell by the stretched cell wall is called wall pressure. Usually, both pressures, turgidity pressure and wall pressure, are offset by maintaining balance.
The turgidity of a living cell is influenced by three primary factors:
1- The formation of osmotically active substances within the cell,
2- An adequate supply of water
3 - a semipermeable membrane.
Some previous concepts to understand the turgidity in biology
Osmosis
Water, a vital element for all living beings, has physical properties that are reflected at the cellular level in the way of transporting from one cell to another, as well as entering and exiting the intracellular environment to the external environment.
This process calls osmosis, and consists of the diffusion of water and minerals through a relatively permeable membrane, from a region of higher concentration to one of lower concentration.
When a cell is in its normal state, the concentration of extracellular and intracellular fluids is the same since there is a balance between the internal environment and the external environment.
Upon subjecting the cell to a hypertonic medium, the inner water of the plastid tends to break out to balance the degree of concentration of the external medium with the inner of the cell, causing plasmolysis.
Plasmolysis
Unlike turgidity, this phenomenon occurs when cells, when losing water, contract, separating the protoplast from the cell wall. Plasmolysis is caused by the semipermeability of the cytoplasmic membrane and the permeability of the cell wall in plants.
This is due to the fact that the conditions of the extracellular environment are hypertonic, that is to say that the water contained within the vacuole leaves the hypertonic environment (osmosis) dehydrating the cell.
Finally, the wall of the cell membrane is separated because the cell is plasmolized. If during this process the plant does not get water to fill the vacuole for the cell to recover its turgor, the plant is most likely to die.
Importance of turgor
First, turgor helps move nutrient solutions between cell and cell. This is due to the difference in the concentration of the cellular sap between one cell and the other. On the other hand, the phenomenon of turgor is necessary for the growth of different organs.
Turgidity is essential in plant cells to keep them erect. Plant cells that lose a lot of water have less turgor pressure and tend to become flaccid. The loss of water eventually causes the plant to wither.
When the cell walls relax at a faster rate than the water can cross the membrane, it results in a cell with lower turgidity pressure, with the opposite effect, plasmolysis.
Turgidity in plants
The plants are hydraulic machines; Depend on"turgor pressure"to elongate their cells and regulate perspiration through the opening and closing of stomatal cells.
The cell wall allows plant cells to resist turgor, this process does not occur with other cells, such as erythrocytes, which burst easily due to this phenomenon. Thanks to the turgor pressure, the plants increase their greenish color.
Turgor is caused by the osmotic flow of water from a region of low solute concentration outside the cell vacuole cell that has a higher concentration of solute. Therefore, plants depend on turgor to maintain their gravity.
Turgor is involved in cell metabolism, and is often the regulation of turgor pressure, the key to the plant's response to changes in the environment.
A rupture in the processes that regulate the turgidity can be the cause of a reduced yield when it is exposed to tensions like being drought, contamination and extreme temperatures, reason why its study in agriculture is important.
Most of the time the plant cells receive water from the liquid that fills the spaces between the cells and penetrates the tiny cavities between the cellulosic fibers lining the cell walls.
As most cells are impregnated in this liquid, and as it almost always contains an osmotic potential greater than the cellular sap, the plant will be mostly composed of completely turgid cells.
The cellular turgor gives the plant firmness, helps it maintain its shape, and allows it to function efficiently. All seedlings, as well as herbaceous plants and plant structures such as leaves and flowers, depend entirely on the turgidity of their cells for their support.
The turgor in the laboratory
Turgidity can occur by suspending the cells in dilute solutions and / or by supplying water with low concentrations of solute (eg, tap water or rainwater).
As the water evaporates, they remain solutes, concentrating the aqueous solution. This leads to the solution of one that is hypotonic to one that is isotonic and then hypertonic.
Leaves of plants tend to fall when sufficient water has been evaporated by bathing the cells in an isotonic solution rather than hypotonic.
In contrast, animal cells lack cell walls and are usually bathed in an isotonic solution. That is why animal cells normally do not show turgor, but rather an exposure to a hypotonic solution.
Bacteria also prefer to exist in a turgid state where contrast, plasmolysis, interferes with metabolism and growth.
In fact, one approach to food preservation is to create hypertonicity within foods, such as high salt or sugar concentrations, to prevent turgidity and promote plasmolysis.
The turgor in medicine
By turgor, reference is also made to the normal elasticity of the skin, its ability to expand, due to the outward pressure of the tissues and the interstitial fluid, and to return to its original state.
Through the assessment of turgidity, a physician can determine if a person is dehydrated, so an essential part of physical examination is the evaluation of skin turgor.
References
- Fricke, W."Turgor Pressure". ELS. 1-6. Published Online: January 2017. Retrieved from: Willey Online Library. Wiley.com.
- Agarwal, N."What is Turgidity and its importance?"Retrieved from: Preserve your Article. In: preservearticles.com (2017).
- S. Beckett. "Biology: A Modern Introduction". Oxford University Press (1986).
- Campbell, Reece. "Biology"Pan American Medical Ed. (2007).
- "What is Turgidity?"QSStudy (2017) Recovered from: qsstudy.com.
- "Osmosis"Retrieved from:"The cell: fundamental unit"at: sites.google.com.
- Abedon,"Turgidity"(2016) in: Biology as Poetry: Cell Biology Department of Microbiology, The Ohio State University. Retrieved from: biologyaspoetry.com.
- Pritchard, J."Turgor Pressure". University of Birmingham, Birmingham, UK. Encyclopedia of Life Sciences (2001) Nature Publishing Group els.net.