The main difference between flaccid and plasmolysed is that flaccid is the condition resulting in the suspension of plant cells in an isotonic solution, whereas plasmolysed is the condition resulting in the suspension of plant cells in a hypertonic solution. Furthermore, the protoplast does not exert any pressure on the cell wall in the flaccid condition while the protoplast is shrunken when plant cells are plasmolysed.  

In brief, flaccid and plasmolysed are two conditions of plant cells occurring in the absence of turgor pressure. Generally, turgor pressure is exerting pressure on the cell wall by the protoplasm when it absorbs water through the cell membrane. 

Key Areas Covered 

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

Key Terms 

Concave Plasmolysis, Convex Plasmolysis, Endosmosis, Exosmosis, Flaccid, Plamolysed, Protoplasm

What is Flaccid 

Flaccid is the condition which occurs when a plant cell is placed in an isotonic solution. Therefore, it is the state between turgidity and plasmolysis where the plasma membrane is not pushed against the cell wall. Since the water potential inside the cell is higher than in the surrounding solution, water molecules from the cytoplasm move out of the cell through exosmosis. Hence, this reduces the turgor pressure to some extent. 

Figure 1: Turgor Pressure on Plant Cells

However, the movement of water continues until the water potential on both sides of the plasma membrane becomes equal. Thus, in the flaccid state of a cell, there is no net movement of water across the plasma membrane. Both endosmosis and exosmosis occur at the same rate. Furthermore, the more extreme state of flaccidity is plasmolysis in which the persisting release of water molecules occurs from the cytoplasm when the cells are placed in a hypertonic solution.  

What is Plasmolysed 

Plasmolysed is the condition of plant cells losing water from the cytoplasm when 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 osmosis. Since osmosis occurs towards the outside here, it is exosmosis. Additionally, with the loss of water, the turgor pressure of the cytoplasm gradually drops.  

Figure 2: Rhoeo Plasmolysis

Moreover, based on the effect on the protoplasm, there are two types of plasmolysis. They are the 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 reverses with the replacement of the plant cell in a hypotonic solution with 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. However, it is not reversible.   

Similarities Between Flaccid and Plasmolysed  

• Flaccid and plasmolysed are two conditions of plant cells, resulting in the absence of turgor pressure exerted on the cell wall by the protoplasm.  
• Therefore,  both conditions do not allow the protoplasm to become firmer.  
• Endosmosis and exosmosis are the two driving forces, which lead to each condition. 

Differences Between Flaccid and Plasmolysed 

Definition 

Flaccid refers to the condition resulting in the suspension of plant cells in an isotonic solution, while plasmolysed refers to the condition resulting in the suspension of plant cells in a hypertonic solution.  

Type of Solution 

While flaccid cells occur when placed in an isotonic solution, plasmolysed cells occur when placed in a hypertonic solution. 

Process 

In flaccid cells, both endosmosis and exosmosis occur at the same rate while in plasmolysed cells, exosmosis results in the removal of water from the protoplasm. 

Characteristics of the Protoplasm 

In addition, the protoplasm does not exert any pressure on the cell wall in the flaccid condition while the protoplasm is shrunken when plant cells are plasmolysed.  

Water Potential 

Moreover, the protoplasm of the flaccid cells has the same water potential with respect to the outside solution, while the protoplasm of the plasmolysed cells has less water potential. 

Conclusion 

Flaccid is a condition which occurs when a plant cell is in an isotonic solution. Both exosmosis and endosmosis occur at the same rate. Therefore, the protoplasm does not exert any turgor pressure on the cell wall. In contrast, plasmolysed is another condition which occurs when a plant cell is in a hypertonic solution. However, only exosmosis occurs here, removing water from the protoplasm to the outside solution. Hence, the protoplasm shrinks. Thus, the main difference between flaccid and plasmolysed is the effect of the water potential of the outside solution on the plant cell. 

References:

1. Warith, Azeez. “Turgidity And Plasmolysis Definition: Flaccidity And Active Transport.” Acadel, 20 Nov. 2019, Available Here.

Image Courtesy:

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

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