Plant-water relations plasmolysis

Introduction

Although both plant and animal cells are eukaryotic, there are certain variations between them, such as the presence of cell walls in plants and the different sizes of vacuoles. These distinctions reveal the diversity of their functions and the processes that these cells go through. Plasmolysis is one of these crucial mechanisms.

What is Plasmolysis?

Plasmolysis occurs when a plant cell is placed in a hypertonic solution and loses water (a solution having a higher amount of solutes than the cell). The underlying mechanism behind this is osmosis, which causes water to migrate outside, causing the cell to shrink. Plasmolysis becomes an out-of-control process because osmosis takes no energy, despite the fact that excessive water loss might cause the cell membrane to collapse.

Plasmolysis can be reversed by soaking the cell in a hypotonic solution for a while. Stomata helps to keep water in the plant and prevent it from drying out. Wax also aids in the retention of water within the plant. Crenation is the analogous procedure in animal cells.

Internal and external factors have a significant impact on the plasmolysis process, as well as the plasmolysis time. For some cell species, protoplasmic viscosity, cell wall adhesion, and cell wall pore size are the most important parameters affected by the plasmolysis process. As the cell type changes, the plant’s age increases, and the stage of growth the plant is at the time of this procedure, these influencing factors can change dramatically.

Types of Plasmolysis

By observing the gap between the cell wall and the plasma membrane, it is simple to determine that Plasmolysis has happened. Plasmolysis can be classified into two categories based on the appearance of protoplasmic shrinkage: concave and convex plasmolysis.

Concave Plasmolysis-  Both the protoplasm and the plasma membrane shrink and separate from the cell wall in concave plasmolysis. A ‘half-moon-shape’ is created in the cell due to the separation of protoplasm (then called protoplast). However, by immersing the cell in a hypotonic solution, concave plasmolysis can be reversed.

Convex Plasmolysis- This is a process that cannot be reversed. Excessive water loss from the cell loosens the plasma membrane and protoplasts, resulting in cell wall disintegration. The cell is destroyed as a result of this procedure, which cannot be reversed. As a result, when a plant is deprived of water, it withers and dies.

Importance

Plasmolysis is a plant cell’s response to a hypertonic environment, as it is known to the general public. It is the result of protoplasm separation from the surrounding cell wall. The area between the cell wall and the protoplasm becomes packed with solutes when this happens to cells. Water disperses to this area as a result. The plant’s need to correct its state is signaled by the partial detachment of protoplasm from the cell wall, which prompts the plant to absorb water from its roots and avoid more water loss through the stomatal mechanism. Given that cytolysis has not yet happened, this may be regarded as an advantage of plasmolysis. Otherwise, excessive plasmolysis could result in a permanent loss of operational integrity, eventually leading to the cell’s demise.

Plasmolysis Process

The entire plasmolysis process can be broken down into three steps.

Stage 1: This is the first stage of the process, when the cell begins to lose water, shrinks in size, and the cell wall can be detected.

Stage 2- When the cell has reached its maximum level of contraction, the cytoplasm separates from the cell wall, causing the cell to become spherical.

Stage 3- At this point, the cytoplasm has entirely detached from the cell wall and has settled in the middle.

Plasmolysis vs. Flaccidity

Plasmolysis is defined as the shrinking of protoplasm as a result of contact with hypertonic environments. The decrease of turgor caused by a lack of net water flow between the plant cell and the isotonic environment is known as flaccidity. When it comes to losing cell turgor and causing the plant to bend, flaccidity is still analogous to plasmolysis.

Both of these circumstances can be reversed in the plant cell turgor by making the fluid that surrounds the cell hypotonic. A flaccid cell, on the other hand, is never turgid or plasmolyzed.

Plasmolysis Examples

Plasmolysis is characterised by a rapid loss of water from the cell, making it a rare natural occurrence. When plants are subjected to coastal floods or chemical weedicides, it can be seen. The shrinkage of food and pickles that we place in excessive salts to preserve them are two common plasmolysis instances.

Cause of Plasmolysis

• Plasmolysis occurs as a result of the Exosmosis condition, in which water molecules flow from the cell’s highest concentration areas to lower level concentration areas throughout the cell membrane. 
• The cell shrinks when it is placed in a hypotonic solution, which is a solution with increased levels of solute concentration. 
• When a plant cell is kept in a hypotonic solution, it absorbs water through osmosis, and the capacity of the water in the cell rises, causing the pressure to rise, forcing the protoplasm to touch the cell walls. 
• Turgor is a state in which a plant’s cells are forced against one another in a similar manner and counter-attack other water openings to a certain extent, which is known as full turgor. The turgor in the plants that are utilised to push them keeps them standing upright and prevents the plant cell from overflowing. It provides hardness to plant cells, and if that stiffness is lost, the plant will collapse under the weight of its own weight.
•  When there are no longer air spaces around a cell, the turgor burden begins to deteriorate, resulting in a higher osmotic pressure that belongs to the cell.

Conclusion

The water concentration inside the cell is greater than that outside the cell, water passes through the cell membrane into the surrounding medium when plant cells are immersed in a sodium chloride 5 percent solution or a concentrated salt solution. Protoplasm eventually shrinks and takes on a spherical shape. This is referred to as plasmolysis. Because the concentration of water outside the cell is higher than inside the cell, when a plant cell is immersed in sodium chloride 0.1 percent solution or dilute salt solution, water travels inside the cell. The cell swells and becomes turgid as a result.