Plasmolysis and Deplasmolysis: Definition, Purposes & Examples, Process, Types

What Is Plasmolysis?

Plasmolysis is the contracted state of protoplasm in a plant cell due to loss of water. It occurs when plant cells are placed in a hypertonic solution and causes the water to rush out of the cell, peeling the cell membrane away from the cell wall. The phenomenon of plasmolysis clarifies the effects of osmotic pressure on plant cells. It rarely occurs naturally.

Stages Of Plasmolysis

Plasmolysis takes several successive steps, accompanied by distinct changes in the cell structure. These changes occur during plasmolysis:

Incipient Plasmolysis

The outflow of water from the cell sets in; hence the cell starts to shrink. The cell wall is still intact while the volume of the cell decreases, due to which the cell wall appears more prominent.

Evident Plasmolysis

In this stage, the cell wall is maximally contracted. The cytoplasm starts detaching from the cell wall and becomes roughly spherical as the protoplasm withdraws further.

Final Plasmolysis

The cytoplasm is completely separated from the cell wall in the final stage and centrally lies in a cell. This appears to be a shrunk cell detached from the cell wall.

How Does Water Move Across Cell Membranes?

Osmosis is the process under which water movement across the cell membranes takes place. In osmosis, water molecules move from an area where their concentration is higher to an area where their concentration is less. The cell membrane is semipermeable and only allows the desired amount of water and other essential molecules, that are necessary for the proper functioning of the cell to pass through. This type of movement is required during the process of plasmolysis and deplasmolysis.

Demonstration Of Plasmolysis In Rheo Plant

Plasmolysis can be satisfactorily demonstrated using plant cells from Rheo plants or other materials like Elodea or onion epidermal cells. These cells, when put in a hypertonic salt solution, will lose water and hence shrink. The coloured sap in these cells facilitates observation of the plasmolytic process under the microscope.

Types Of Plasmolysis

But plasmolysis can be classified based on the final shape taken by the cytoplasm as the process ends:

Concave Plasmolysis

In concave plasmolysis, the plasmalemma and protoplasm contract and get separated from the cell wall; however, they do not collapse completely. This type of plasmolysis is reversible, meaning it can be reversed by putting the cell in a hypotonic solution, which will permit water to reenter the cell.

Convex Plasmolysis

The plasmalemma and protoplasm are completely detached from the cell wall in this case. Collapse of the cell wall takes place, causing cell destruction. The process is irreversible and is the cause of the death of a plant due to the loss of an extreme amount of water.

Examples Of Plasmolysis

Plasmolysis takes place in several practical instances, including:

• Shrinkage of vegetables in hypertonic solutions.

• Shrinkage of blood cells in hypertonic conditions

• Salt deposition from coastal flooding.

• Weedicides kill weeds in farms.

• Food preservation in high salt concentrations arresting the growth of microorganisms.

What Is Deplasmolysis?

Deplasmolysis is when a plasmolysed cell is placed in a hypotonic solution. It reenters the cell, and it swells and regains its turgidity. In an isotonic solution, the cell will be in a state of equilibrium; there will be no net movement of water in an isotonic solution, flaccid.

Conclusion

The processes of plasmolysis and deplasmolysis are very important in understanding plant cell responses to osmotic stress. From these phenomena, we understand the nature of water balance maintenance in plant cells and how they adapt to changes in their ambient environment. These processes are central to plant biology but also in practical applications such as agriculture and food preservation.

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