To study the phenomena of plasmolysis in epidermal peels taking Rhoeo Leaves as an example in hypotonic and hypertonic solutions in a salt solution.
What is plasmolysis?
It is a process of contraction or shrinkage of the protoplasm of a plant cell due to loss of water from the cell. It takes place in extreme conditions and hence occurs rarely. Plasmolysis can be carried out in a laboratory by submerging a living cell in a concentrated sugar or salt solution for water loss from the cell.
Why is rheo epidermal cell used in this experiment?
It is because rheo has colored cell sap that is visible clearly.
How does water permeate through the cell membrane?
The cell membrane serves as a semipermeable membrane dividing the inner of all cells from that of its surroundings. This membrane permits movement of a few of the particles, water molecules, ions across the membrane while blocking others. There is continuous movement of water molecules in and out of the cell across the cell membrane which serves as an important attribute for enabling cells to absorb water.
- Glass slides
- Rhoeo leaf
- Compound microscope
- Sodium chloride 5% solution
- Sodium chloride 0.1% solution
- Place two glass slides on a table
- From the Petri dish, take a rhoeo leaf
- Make a fold on the leaf so as to tear it from the lower side of the leaf
- Extract two small fragments of a fine and transparent layer with the help of forceps from the lower surface of the epidermis of the rhoeo leaf.
- Now set up the epidermal peels on each of the glass slides
- With the help of a dropper from the beaker, add some sodium chloride 0.1% solution
- Add 1-2 drops of the solution on one of the slides
- With the help of another dropper from the beaker, add some sodium chloride 5% solution
- Add 1-2 drops of the solution to another slide
- Set a coverslip on the peel of both sides with the help of a needle
- Observe each slide one by one under a compound microscope.
After a period of 30 minutes, we notice that cells placed in the sodium chloride 0.1% solution seem to be turgid. The cells in the sodium chloride 5% solution exhibit the process of plasmolysis.
Plasmolysis is observed when plant cells are submerged in a concentrated salt solution or sodium chloride 5% solution as water passes through the cell membrane into the encircling medium. This occurs as the concentration of water inside the cell is higher than the outside of the cell hence the protoplasm induces shrinkage and takes a spherical shape.
When submerged in a dilute salt solution or sodium chloride 0.1% solution, the water in the plant cells moves from the outside to the inside of the cell as the water concentration is higher outside the cell as compared to the inside of the cell which causes the turgidity of the cell.
- The part of the rhoeo leaf that needs to be extracted for the experiment is the epidermal peel from the lower surface
- Care needs to be taken to ensure that the peel is moist and not dry.
Q.1. What is plasmolysis?
A.1. It is a process wherein the protoplasm of the plant cell turns rounded as a result of contraction when placed in a hypertonic solution due to exosmosis resulting in the decline in the tension of the cell wall.
Q.2. What is incipient plasmolysis?
A.2. It is the initial phase of plasmolysis wherein the protoplasm is just about to leave the cell wall.
Q.3. What is the significance of plasmolysis? List any two.
A.3. Listed below is its importance:
- Helps to better understand and study the nature of a living cell
- It is used in the preservation of food materials such as jellies, meat. Used in pickling as its salting is known to kill bacteria
Q.4. What is Osmotic pressure?
A.4. It is a pressure that checks the osmosis process. It needs to be applied so as to check the passage of the solvent as a result of osmosis.
Q.5. What is turgor pressure?
A.5 It is the pressure that presses the plasma membrane against the cell wall. It is a hydrostatic pressure that arises within the cell as a result of endosmosis on the cell wall.
Q.6. What is wall pressure?
A.6. The turgor pressure on the rigid walls of the cells causes to exert equal pressure in the opposing direction. That is termed as wall pressure.
Q.7. When does the water potential become equal to that of its surroundings?
A.7. It happens when the turgor pressure becomes equal to the wall pressure thereby stopping the entry of water into the cells.
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