WHAT IS TURGOR? (BIOLOGY) - BIOLOGY - 2025

The turgor is the phenomenon of total expansion of a cell swelling by fluid pressure. Through this phenomenon, cells swell by absorbing water, pressing against cell membranes, tightening them.

When fluid exerts outward pressure on the cell wall it is called turgor pressure. Whereas, the inward pressure exerted on the cell contents by the stretched cell wall, is called wall pressure. In general, both pressures, turgor pressure and wall pressure, oppose each other while maintaining equilibrium.

The turgor of a living cell is influenced by three primary factors: the formation of osmotically active substances within the cell, an adequate supply of water, and a semi-permeable membrane.

Some previous concepts to understand turgor in biology

Osmosis

Water, a vital element for all living beings, has physical properties that are reflected at the cellular level in the way it is transported from one cell to another, as well as entering and leaving the intracellular environment to the external environment.

This process called osmosis, and consists of the diffusion of water and minerals through a relatively permeable membrane, from a region of higher concentration to a 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.

When the cell is subjected to a hypertonic medium, the internal water of the plasma tends to come out to balance the degree of concentration of the external medium with the internal one of the cell, producing plasmolysis.

Plasmolysis

Contrary to turgor, this phenomenon occurs when cells, losing water, contract, separating the protoplast from the cell wall. Plasmolysis is caused by the semipermeability of the cytoplasmic membrane and by the permeability of the cell wall in plants.

This is because the conditions of the extracellular environment are hypertonic, that is, the water contained within the vacuole leaves the hypertonic environment (osmosis), dehydrating the cell.

Finally the cell membrane wall is separated because the cell plasmolyses. If during this process the plant does not get water to fill the vacuole so that the cell can regain its turgor, the plant will most likely die.

Importance of turgor

First, turgor helps move nutrient solutions between cell and cell. This is due to the difference in the concentration of cell sap between one cell and the other. On the other hand, the phenomenon of turgor is necessary for the growth of different organs.

Turgor is essential in plant cells to make them stand upright. 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 wilt.

When cell walls relax at a faster rate than water can cross the membrane, it results in a cell with lower turgor pressure, producing the opposite effect, plasmolysis.

Turgor in plants

Plants are hydraulic machines; they 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 easily burst 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 of the cell to the vacuole of the cell that has a higher concentration of solute. For this reason, plants depend on turgor to maintain their gravity.

Turgor participates in cell metabolism, and it is often the regulation of turgor pressure that is the key to the plant's response to changes in the environment.

A breakdown in the processes that regulate turgor can be the cause of reduced performance when exposed to stresses such as drought, pollution and extreme temperatures, which is why its study in agriculture is important.

Most of the time, plant cells receive water from the fluid that fills the spaces between cells and enters the tiny cavities between the cellulose fibers that line the cell walls.

As most of the cells are impregnated in this liquid, and as it almost always contains a higher osmotic potential than the cell sap, the plant will be mostly made up of completely turgid cells.

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 turgor of their cells for support.

Turgor in the laboratory

Turgor can occur by suspending cells in dilute solutions and / or supplying water with low concentrations of solute (eg, tap water or rainwater).

As the water evaporates, solutes remain, concentrating the aqueous solution. This leads the solution from one that is hypotonic to one that is isotonic and then hypertonic.

Plant leaves tend to drop when enough water has evaporated, bathing cells in an isotonic rather than hypotonic solution.

In contrast, animal cells lack cell walls and are normally bathed in an isotonic solution. This is why animal cells do not normally show turgor, but rather an exposure to a hypotonic solution.

Bacteria also prefer to exist in a turgid state where the contrast, plasmolysis, interferes with metabolism and growth.

In fact, one approach to food preservation is to create hypertonicity within foods, such as high concentrations of salt or sugar, to prevent turgor and promote plasmolysis.

Turgor in medicine

Turgor also refers to the normal elasticity of the skin, its ability to expand, due to the outward pressure of the tissues and interstitial fluid, and return to its original state.

Through the assessment of turgor, a doctor can determine if a person is dehydrated, so an essential part of the physical examination is the evaluation of the turgor of the skin.

References

1. Fricke, W. "Turgor Pressure." eLS. 1–6. Published Online: January 2017. Retrieved from: Willey Online Library. wiley.com.
2. Agarwal, N. "What is Turgidity and mention its importance?" Recovered from: Preserve your Article. In: preservearticles.com (2017).
3. S. Beckett. "Biology: A Modern Introduction". Oxford University Press (1986).
4. Campbell, Reece. "Biology" Ed. Médica Panamericana (2007).
5. "What is Turgidity?" QSStudy (2017) Recovered from: qsstudy.com.
6. "Osmosis" Recovered from: "The cell: fundamental unit" in: sites.google.com.
7. Abedon, “Turgidity” (2016) in: Biology as Poetry: Cell Biology Department of Microbiology, The Ohio State University. Recovered from: biologyaspoetry.com.
8. Pritchard, J. "Turgor Pressure." University of Birmingham, Birmingham, UK. Encyclopedia of Life Sciences (2001) Nature Publishing Group els.net.