Two Types of Plasmolysis

Plasmolysis is the process by which protoplasm shrinks away from a plant’s or bacterium’s cell wall. Water loss via exosmosis frequently causes protoplasmic shrinkage, resulting in gaps between the cell wall and the plasma membrane. Plasmolysis is classified into two types: concave plasmolysis and convex plasmolysis. Concave plasmolysis occurs when the protoplasm and plasma membrane contract, resulting in concave pockets. There are still attachment points between the cell wall and the protoplasm. As a result, a hypotonic solution can still be used to reverse the condition. Convex plasmolysis is a type of irreversible plasmolysis. The plasmolyzed cell in this case is a spherical protoplast that completely detaches from the cell wall.

Plasmolysis

Plasmolysis is defined in biology as cell contraction caused by protoplast shrinkage when exposed to a hypertonic solution. Crenation is the term used to describe the equivalent condition in animal cells. Similarly, plant and animal cells lose water as water molecules diffuse to the gradient of concentration. However, in animal cells, the net efflux of water causes the cells to wrinkle. Because of the presence of the cell wall, plant cells do not appear wrinkled. Rather, in the case of concave plasmolysis, they form concave pockets, whereas in the case of convex plasmolysis, they form a full sphere.

Types of Plasmolysis

Concave Plasmolysis

Concave plasmolysis is a typically reversible process. Because of the loss of water during concave plasmolysis, the protoplasm and plasma membrane shrink away from the cell wall in places; the protoplasm is then referred to as protoplast once it has begun to detach from the cell walls. As  protoplast peels from the surface of the cell wall, half-moon-shaped “pockets” form in the cell. This is reversed by immersing the cell in a hypotonic solution, which causes water to rush back into the cell.

Convex Plasmolysis

The severity of the convex plasmolysis is greater than that of concave plasmolysis. When a cell undergoes complex plasmolysis, the plasma membrane and protoplasm lose so much water that they detach from the cell wall completely. Cytorrhysis is a process by which the cell wall collapses. Convex plasmolysis is irreversible and results in the cell’s destruction. Essentially, this was what happens when a plant wilts and dies from lack of water.

Defences Against Plasmolysis

Plasmolysis occurs in extreme cases of water loss and is uncommon in nature. Plants have a couple of mechanisms in place to protect themselves from water loss. Stomata, or small holes on the underside of a plant’s leaves, close to help the plant retain water. Plants also produce wax, which acts as another barrier against water loss.

Examples of Plasmolysis

Although plasmolysis occurs more frequently in laboratories, it can also occur in the field. During periods of extreme coastal flooding, for example, ocean water deposits salt onto land. When there is too much salt in the soil, the water drains out of the plants, killing them. Weedicides are also used to kill unwanted plants via plasmolysis. The same process is used to preserve food and make jams, jellies, and pickles when a lot of salt and/or sugar is added. These food items can be preserved because the cells lose water and become less conducive to the growth of microorganisms such as bacteria.

Importance of plasmolysis

The partial separation of the protoplasm from the cell wall indicates that the plant needs to correct the situation, prompting it to take in water from the roots and prevent further water loss through the stomatal mechanism.

Onion cell plasmolysis

Typically, Tradescantia or Rheo plant cells, Elodea plants (known as the elodea plasmolysis experiment), or onion epidermal cells (known as the onion cell plasmolysis experiment) are used in such experiments because they have coloured sap that can be easily observed and identified under a microscope. The video below goes into greater detail about onion plasmolysis.

Process of plasmolysis

The three stages or processes that occur during plasmolysis

Incipient plasmolysis

When water begins to flow out of the cell, this is the first stage of plasmolysis. The cell initially shrinks in volume, and the cell wall becomes visible.

Evident plasmolysis

The cell wall reaches its limit of contraction in this stage of plasmolysis, and the cytoplasm separates from the cell wall, forming a spherical shape.

Final plasmolysis

The third and final stage of plasmolysis occurs when the cytoplasm is completely free of the cell wall and remains in the cell’s centre.

During the Plasmolysis process, the cell membrane separates the plant cell’s interior from the surrounding environment. It allows water molecules, ions, and other selective particles to pass through the membrane while blocking others. Water molecules move in and out of cells via cell membranes, and water flow is required for cells to obtain water.

Plasmolysis can be easily demonstrated in the lab by immersing a living cell in a concentrated salt solution. Osmosis occurs when plant cells are immersed in a concentrated salt solution, allowing water from the cell sap to escape. As a result, water enters the cell membrane and enters the surrounding medium. Finally, the protoplasm separates from the cell and forms a sphere.

Conclusion

Plasmolysis is the process by which protoplasm shrinks away from a plant’s or bacterium’s cell wall. Water loss via exosmosis frequently causes protoplasmic shrinkage, resulting in gaps between the cell wall and the plasma membrane. The plasmolyzed cell in this case is a spherical protoplast that completely detaches from the cell wall. . Crenation is the term used to describe the equivalent condition in animal cells. Similarly, plant and animal cells lose water as water molecules diffuse to the gradient of concentration. Concave plasmolysis is a typically reversible process. Because of the loss of water during concave plasmolysis, the protoplasm and plasma membrane shrink away from the cell wall in places; the protoplasm is then referred to as protoplast once it has begun to detach from the cell walls. Cytorrhysis is a process by which the cell wall collapses. Convex plasmolysis is irreversible and results in the cell’s destruction. Essentially, this was what happens when a plant wilts and dies from lack of water. Plasmolysis occurs in extreme cases of water loss and is uncommon in nature. Plants have a couple of mechanisms in place to protect themselves from water loss. Stomata, or small holes on the underside of a plant’s leaves, close to help the plant retain water. When there is too much salt in the soil, the water drains out of the plants, killing them. Weedicides are also used to kill unwanted plants via plasmolysis. When water begins to flow out of the cell, this is the first stage of plasmolysis. The cell initially shrinks in volume, and the cell wall becomes visible. The cell wall reaches its limit of contraction in this stage of plasmolysis, and the cytoplasm separates from the cell wall, forming a spherical shape. During the Plasmolysis process, the cell membrane separates the plant cell’s interior from the surrounding environment.