What is the Difference Between Plasmolysis and Turgidity

The main difference between plasmolysis and turgidity is that plasmolysis is the process by which cells lose water when placed in a hypertonic solution, whereas turgidity is the state of cells being swollen when placed in a hypotonic solution. Therefore, plasmolysis occurs through exosmosis, while turgidity occurs through endosmosis. 

Plasmolysis and turgidity are two conditions of plant cells, occurring based on the water potential or tonicity of the surrounding environment. Generally, osmosis is the process by which water moves through the cell membrane in and out. 

Key Areas Covered 

1. What is Plasmolysis
     – Definition, Process, Importance
2. What is Turgidity
     – Definition, Process, Importance
3. What are the Similarities Between Plasmolysis and Turgidity
     – Outline of Common Features
4. What is the Difference Between Plasmolysis and Tirgidity
     – Comparison of Key Differences

Key Terms 

Hypertonic, Hypotonic, Osmosis, Plasmolysis, Plant Cells, Turgor Pressure

What is Plasmolysis 

Plasmolysis is the condition of plant cells losing water from the cytoplasm. Generally, it occurs when a plant cell is placed in a hypertonic solution. Here, the solute concentration of the surrounding solution is higher than that of the cytoplasm. Therefore, the water potential of the cytoplasm is higher. Hence, water molecules move through the cell membrane to the outside solution until the inside and outside water potentials become equal. Furthermore, the process of moving water through a semipermeable membrane such as the cell membrane is known as osmosis. Since this osmosis occurs towards the outside, it is known as exosmosis. Additionally, with the loss of water, the turgor pressure of the cytoplasm gradually drops. 

Figure 1: Plasmolysis

Moreover, based on the effect on the protoplasm, there are two types of plasmolysis. They are concave and convex plasmolysis. In concave plasmolysis, the protoplasm shrinks away from the cell wall, detaching it to form half-moon-shaped pockets in between. Generally, this condition can be reversed with the replacement of the plant cell in a hypotonic solution with the higher water potential. On the other hand, convex plasmolysis is severe than concave plasmolysis. During this, the protoplasm completely detaches from the cell wall in a process called cytorrhysis. Generally, it is not reversible.    

What is Turgidity 

Turgidity is the state of plant cell being turgid or swollen due to high fluid content inside the cell. Moreover, in turgidity, the plant cell is in its fully expanded condition. Generally, turgidity occurs when the plant cell is in a hypotonic solution. Here, the surrounding solution contains a low solute concentration than that of the cytoplasm. Therefore, the water potential of the surrounding solution is high. Hence, water enters into the cell by endosmosis. Furthermore, the entrance of more water into the cell increases the turgor pressure, pushing the cell membrane against the cell wall. 

Figure 2: Different Turgor Pressures in a Plant Cell

Moreover, turgidity is an important factor for plant cells. Basically, it helps to make the plant upright. Therefore, it gives mechanical support to the plant. It is also responsible for the opening and closing of stomata, aiding gas exchange of plants. Actually, the size of the stomata depends on the turgor pressure of guard cells. Additionally, it is important for the dispersal of seeds and spores, germination, etc.  

Similarities Between Plasmolysis and Turgidity 

• Plasmolysis and turgidity are two conditions of plant cells, occurring based on the type of water movement in or out of the cell. 
• Here, the water movement occurs by osmosis through the cell membrane. 
• Moreover, it occurs until the water potential of the cell becomes equal to the water potential of the surrounding environment. 

Difference Between Plasmolysis and Turgidity 

Definition 

Plasmolysis refers to the process in which plant cells lose water in a hypertonic solution, while turgidity refers to the state of plant cells being swollen due to high fluid content. Thus, this is the main difference between plasmolysis and turgidity.

Cause 

While plasmolysis occurs due to exosmosis, turgidity occurs due to endosmosis. 

Protoplasm 

Moreover, protoplasm shrinks during plasmolysis while protoplasm swells during turgidity. 

Type of Solution 

Another difference between plasmolysis and turgidity is that the plasmolysis occurs when cells are in a hypertonic solution, while the turgidity occurs when the cells are in a hypotonic solution. 

Water Movement 

In plasmolysis, water moves from the protoplasm to the surrounding solution while, in turgidity, water moves from the surrounding solution to into the protoplasm. 

Water Potential 

The water potential of the protoplasm is higher in plasmolysis, while the water potential of the surrounding solution is higher in turgidity. 

Turgor Pressure 

Turgor pressure decreases due to plasmolysis, while turgor pressure increases due to turgidity. 

Effect on the Plasma Membrane 

Plasmolysis causes the cell membrane to peels away from the cell wall while turgidity pushes the plasma membrane against the cell wall. 

Effect on the Plant 

Also, another important difference between plasmolysis and turgidity is that plasmolysis causes the plant to wilt while turgidity helps the plant to stand upright. 

Conclusion 

Plasmolysis is the condition of plant cells, arising due to exosmosis. Generally, when a plant cell is placed in a hypertonic solution, it loses water from the protoplasm to the surrounding solution due to the high water potential. However, this makes the plant wilt. On the other hand, turgidity is the condition in plant cells that arises due to endosmosis. Basically, when a plant cell is in a hypotonic solution, it swells by the movement of water from the surrounding solution into the cell. Significantly, this causes to stand the plant upright. Therefore, the main difference between plasmolysis and turgidity is the type of movement of water and its effect on the plant cell. 

References:

1. “Plasmolysis – Definition, Types and Examples.” Biology Dictionary, 29 Mar. 2019, Available Here.
2. “Turgidity: Definition and Importance.” QS Study, 21 Aug. 2017, Available Here. 

Image Courtesy:

1. “Rhoeo Discolor – Plasmolysis” By Mnolf – Photo taken in Innsbruck, Austria (CC BY-SA 3.0) via Commons Wikimedia   
2. “Turgor pressure on plant cells diagram” By LadyofHats (Public Domain) via Commons Wikimedia