Turgidity: Definition, Types, and Examples
Turgidity Definition
The state of being turgid or swollen, especially due to high fluid content, is referred to as turgidity. Turgidity refers to the feeling of being bloated, distended, or swollen in general.
Turgidity, in a biological context, explains how plant cells may remain upright despite the absence of a skeletal structural structure like mammals. Plants gain stiffness as a result of it.
As a result, cell distention is a common occurrence in plants. In fact, if you don’t provide it to the plant, it will appear withered and sick. The existence of the cell wall and the osmoregulatory function of the vacuole in plants allow for turgidity.
The cell wall protects the cell against lysis caused by excessive water inflow, whereas the vacuole controls solute concentration and promotes osmotic water transport into and out of the cell.
Turgidity Etymology
Turgidity is derived from the Latin turgidus, which derives from the Greek turgēre , which means “to swell.”
Turgidity in Plants
Plant turgidity is accounted for by the cell wall, which is one of the most important characteristics of a plant cell. Aside from the plasma membrane, the plant cell wall is another layer that surrounds the cell. It might be made up of one or two layers. The main cell wall is in charge of secreting the secondary cell wall, which is located atop the plasma membrane.
Plant turgidity refers to a situation in which the cells of a plant become turgid owing to turgor pressure, which is the pressure applied by water inside the cell against the cell wall. The cell wall of a plant organism is one of its most essential characteristics. A cell wall is an additional layer that surrounds a cell. They are absent in the animals, leaving just the cell membrane.
Plants possess both of these qualities. The plant’s cells have an extra protective covering called the cell wall. It is made up mostly of cellulose, pectin, and hemicellulose and is robust and stiff. Plant cell walls are made up of one or two layers. The main cell wall is the initial layer. This layer has the potential to generate a layer underneath it. The secondary cell wall is the new layer.
The second layer is a thick lignin-depositing layer. Lignin contributes to the cell’s waterproofing. These characteristics of the cell wall aid the plant cell’s resistance to osmotic pressure, which is caused by a difference in solute concentrations between solutions separated by a semipermeable barrier, such as the cell membrane, during osmosis.
Turgid Cell
The cell wall and the cell membrane of a plasmolyzed plant cell have gaps between them. When a plant cell is put in a hypotonic solution, this happens. The decrease in turgor pressure is caused by water molecules moving out of the cell. The cell membrane of a flaccid plant cell is not inflated and does not push strongly against the cell wall.
When a plant cell is put in an isotonic solution, this happens. Between the cell and the surrounding fluid, there would be no net flow of water molecules. A cell with turgor pressure is referred to as a turgid cell. When a plant cell is submerged in a hypotonic solution, osmosis allows water to enter the cell, resulting in high turgor pressure on the plant cell wall.
A cell with turgor pressure is referred to as a turgid cell. The plant that seems to be healthy (i.e. not wilted) contains turgid cells. Solutes (such as ions and carbohydrates) are stored in the plant cell (particularly, inside its vacuole). Water prefers to flow in because the inside of the cell has a greater solute concentration (and hence fewer water molecules) than the exterior.
Hypotonic refers to a solution (surrounding the cell) with a lower solute concentration than the solution inside the cell. When a plant cell is submerged in a hypotonic solution, osmosis allows water to enter the cell. A high turgor pressure is applied against the plant cell wall as a result of the inflow of water.
The cell becomes turgid as a result of this. Plants have a cell wall, which protects the cell from bursting (osmotic lysis), which occurs when there is no cell wall. In a hypotonic solution, an animal cell, for example, would swell.
If osmosis continues, the pipe will ultimately explode. As a result, the plant cell’s cell wall is required to maintain cell integrity and prevent the cell from bursting. The osmotic pressure exerted by the cell wall prevents excessive osmosis in the plant cells.
The cell wall, on the other hand, is unable to protect a plant cell that has been exposed to an isotonic or hypertonic solution. These solutions might cause the plant to get wilted and lose its vitality.
Flaccid Cell
An isotonic solution is one in which the concentration of solutes in the solution is the same as the concentration of solutes inside the cell. There would be no net movement of water molecules between the two, implying that there would be no net movement of water molecules between the two. If you put a plant cell in an isotonic solution, it will become flaccid. Flaccidity is the medical term for this disorder.
The cell membrane of a flaccid plant cell is not firmly pressed against the cell wall and is not bulging. Thus, the turgor pressure is the difference between turgidity and flaccidity. Because of the turgor pressure applied to the cell wall, a plant cell appears swollen or distended in turgidity, but in flaccidity, the plant cell loses its turgidity and appears limp or flaccid.
Plasmolyzed Cell
A hypotonic solution is one in which the concentration of solutes is higher than the concentration of solutes inside the cell. The turgor pressure of a plant cell in a hypotonic solution decreases as water molecules migrate out of the cell. Plasmolyzed refers to a cell that has lost its turgor pressure. Plant cells that have been plasmolyzed have holes between the cell wall and the cell membrane.
In addition, the cells looked to be shrinking. Plasmolysis is the process or situation in which protoplasm shrinks as a result of water loss through osmosis. Plasmolysis, on the other hand, is an uncommon occurrence in nature. Rather, plant cells are submerged in powerful saline or sugar solutions in the lab to induce them.
Turgidity and Rigidity
As previously stated, turgidity refers to the state of being turgid or bloated as a result of the fluid present. Rigidity, on the other hand, refers to the state of being stiff and unbending. Turgidity and stiffness are key characteristics of plants because they help them stay erect. Both of these characteristics are due to the turgor pressure exerted on the cell wall.
As previously stated, the cell wall protects the cell from osmotic pressure, which, if too high, might cause osmotic lysis in cells without it. By creating a thicker secondary layer containing lignin, the cell wall also offers structural support. Aside from that, cellulose is present in the cell wall, which makes it stiff and durable.
Another layer of pectin-rich intercellular substance lies between the cell walls. The middle lamella is the name given to this stratum. Its main purpose is to hold neighbouring cells together. Overall, the plant’s cellular characteristics allow it to resist gravitational force and remain erect towards the source of light.
Importance of Turgidity in Plants
Plants require turgidity because it offers structural support and strength. Without it, the plant would be unable to maintain its upright position, which is the optimal position for collecting light energy for photosynthesis. Aside from that, it gives plants rigidity.
The plant cells will not be completely dilated if there is not enough water absorbed to generate turgor. If this situation is not corrected, the plant will become wilted and sickly. The drooping caused by turgor loss can be restored by providing enough water for the vacuole to process through osmoregulation.
Turgidity Citations
- The Nanoscale Organization of the Plasma Membrane and Its Importance in Signaling: A Proteolipid Perspective. Plant Physiol . 2020 Apr;182(4):1682-1696.
- Muscle Articulations: Flexible Jaw Joints Made of Soft Tissues. Integr Comp Biol . 2015 Aug;55(2):193-204.
- Nuclear envelope: a new frontier in plant mechanosensing? Biophys Rev . 2017 Aug;9(4):389-403.
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