Study Of Plasmolysis In Epidermal Peels: Diagram, Overview

Plasmolysis

Plasmolysis is the process whereby, because of a loss of water in a hypertonic solution, the plant cell contracts towards the centre away from the cell wall. This has been caused by osmotic pressure and may result in a heavy loss of water from the cell, whereby causes a shrink of the cell, and consequently, the cell may die. Two types of plasmolysis can be divided as follows:

• Concave Plasmolysis: This is a reversible form where the plasmalemma can return to its original state if it is reintroduced to a hypotonic solution.

• Convex Plasmolysis: It is an irreversible form where the plasmalemma can't come back. Thus permanent damage of the cell membrane in this process leads to its death.

Aim

The experiment will try to observe plasmolysis in Rhoeo plant leaves epidermal peels with the help of hypertonic and hypotonic solutions. This shall help in understanding how plant cells react to osmotic changes in their environment.

What Is Plasmolysis?

Plasmolysis refers to the process whereby the protoplasm of a plant cell shrinks due to loss of water when put in a hypertonic solution. This is because of a loss of water from the cell towards equilibrating the concentration of solutes, thus leading to a contraction of the cell membrane away from the cell wall.

Why Use Rhoeo Leaves?

Rhoeo leaves will be used because their coloured cell sap will show changes more clearly under the microscope.

How Water Passes Through the Cell Membrane

The cell membrane shows selective movement; water molecules and ions may or may not easily pass while some are blocked. This selective permeability of the cell membrane allows water to enter the cell or leave it for proper cellular activity.

Materials Required

1. Needle

2. Forceps

3. Droppers

4. Glass slides

5. Watch glass

6. Rhoeo leaves

7. Coverslips

8. Compound microscope

9. Sodium chloride 5% solution

10. Sodium chloride 0.1% solution

Procedure

1. Take two clean and dry glass slides on a table.

2. Take fresh leaves of Rhoeo and put it on a watch glass

3. Fold the leaves from top to bottom and tear them from the lower side or with the help of a clean blade.

4. With the forceps, take two small pieces of epidermis from the lower surface of the Rhoeo leaf.

5. Place the epidermal peels on a glass slide.

6. Place 12 drops of a 0.1% solution of sodium chloride on one slide.

7. Add 12 drops of a 5% solution of sodium chloride to the other slide.

8. Then, with the help of a needle, cover the slides with a coverslip.

9. Keep the slides undisturbed for some minutes.

10. Observe under a compound microscope the slides and note changes.

Observation

1. After 30 minutes, cells in the sodium chloride 0.1% solution appear turgid, while in the sodium chloride 5% solution, they show shrinkage and plasmolysis.
2. The cells of the hypertonic solution lose huge amounts of water with a detachment of the membrane from the cell wall.

Precautions

1. Epidermal peels are taken from the lower surface of Rhoeo leaves.

2. The peels should be fresh and not dry.

3. The slide is to be prepared in such a manner that no air bubbles should appear below the coverslips.

Conclusion

When plant cells are put in a concentrated salt solution, plasmolysis will take place. It comprises shrinking away of the protoplasm detaching the cell membrane from the cell wall because of loss of water. Contrary to a dilute solution, 0.1 % sodium chloride, the cells will be turgid as the water will move into the cell to equilibrate the osmotic pressure of the cell.