Study Of Plasmolysis In Epidermal Peels: Diagram, Overview

Aim of the Experiment

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 towards the centre away from the cell wall due to loss of water when put in a hypertonic solution. This is caused by osmotic pressure and may result in a heavy loss of water from the cell, which 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.

Principle of the Experiment

Water moves from lower to higher solute concentration through the cell membrane. When Rhoeo leaf epidermis is placed in 5% NaCl, water exits the cells and plasmolysis occurs. When the leaf epidermis is placed in 0.1% NaCl, the water enters the cells and it becomes turgid.

Why Use Rhoeo Leaves?

Rhoeo leaves are used because:

• The coloured cell sap of Rhoeo makes osmotic changes clearly visible under the microscope.

• Epidermal cells are transparent, allowing clear observation of protoplasmic movement.

Materials Required

Material required for the experiment are:

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

The procedure of the experiment includes following steps:

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

The observation of the experiment includes:

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.

Result / 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.

Precautions

The precautions that should be taken while performing the experiment are:

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

2. The peels should be fresh and not dry to ensure the cells are living.

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

4. Handle the epidermis gently to avoid tearing.

5. Observe the slide immediately after preparation for best results.

Applications and Importance

The applications and importance of the experiment is:

• This experiment demonstrates the osmotic behavior of plant cells

• It explains the turgor pressure and water balance in plants

• It forms the basis for understanding wilting and dehydration

Plasmolysis NEET MCQs (With Answers & Explanations)

The key concepts to be covered under this topic for different exams are:

• Types of Plasmolysis

• Principle and Observation of the Experiment

Practice Questions for NEET

Q1. Why can gargle with salt water help cure a bacterial infection?

1. The salt creates an isotonic environment, where bacteria can no longer control the flow of water into or out of the cell.

2. The salt creates a hypertonic environment, causing bacteria to swell with water and burst.

3. The salt creates a hypotonic environment, causing bacteria to undergo plasmolysis and die.

4. The salt creates a hypertonic environment, causing bacteria to undergo plasmolysis and die

Correct answer: 4) The salt creates a hypertonic environment, causing bacteria to undergo plasmolysis and die

Explanation:

Adding salt or sugar to water creates a hypertonic solution that forces the water out of the cells, into the outer environment through osmosis. This results in partial dehydration of the cells and is termed plasmolysis. The cell's normal functioning is interrupted, and its multiplication is hampered by this process, hence making it an excellent method of food preservation as well as an inhibitor of microbial growth.

Hence, the correct answer is option (4) The salt creates a hypertonic environment, causing bacteria to undergo plasmolysis and die.

Q2. What will happen if a plasmolysed cell is placed in a hypotonic solution?

1. Continuation of evident plasmolysis

2. Continuation of incipient plasmolysis

3. Endosmosis of water

4. Equilibirum is achieved

Correct answer: 3) Endosmosis of water

Explanation:

When a plasmolysed cell is kept in a hypotonic solution, it will regain its original shape and this process is called deplasmolysis. When a plasmolysed cell is kept in a hypotonic solution, it will regain its original shape, and this process is called deplasmolysis. During deplasmolysis, water enters the cell by osmosis, causing the cytoplasm to expand and pushing the plasma membrane back against the cell wall. This reverses the effects of plasmolysis, where the cell shrinks due to water loss in a hypertonic solution. Deplasmolysis is a vital process for the restoration of cell turgidity in plant cells.

Hence, the correct answer is option 3) Endosmosis of water

Q3. What is plasmolysis?

1. The process of water flowing out of cells in a hypotonic solution.

2. The process of water flowing in and out of cells at an equal rate in an isotonic solution.

3. The process of water flowing out of cells in a hypertonic solution

4. The process of water flowing in cells in a hypotonic solution.

Correct answer: 3) The process of water flowing out of cells in a hypertonic solution

Explanation:

Plasmolysis is the process in which the protoplasm of a plant cell contracts and pulls away from the cell wall due to the loss of water through exosmosis. This occurs when the cell is placed in a hypertonic solution, where the concentration of solutes outside the cell is higher than inside, causing water to flow out of the cell. On the other hand, the process of water flowing into cells when they are placed in a hypotonic solution (where the concentration of solutes outside the cell is lower than inside) is called turgor pressure or endosmosis. In this case, water moves into the cell, causing it to swell and become turgid.

Hence, the correct answer is option 3) The process of water flowing out of cells in a hypertonic solution.

Also Read:

• MCQs on Plasmolysis and Deplasmolysis

• Diffusion

• Osmosis