Question

Which of the following are used as osmotic stabilizers for the maintenance of protoplasts?
A. Glucose
B. Mannitol
C. PEG
D. Sorbitol
Choose the correct answer from the options given below:

• A. A, C and D only
• B. B, A and C only
• C. A, B and D only
• D. B, C and D only

Hint:

Protoplasts are like water balloons without a box. Mannitol and Sorbitol are the most common "packing peanuts" used to keep them from popping.

Answer 1

The Correct Option is C

Concept: Because protoplasts have no cell wall, they will immediately burst if placed in pure water due to osmotic pressure. They must be kept in a solution that matches or slightly exceeds their internal solute concentration to prevent lysis.

Step 1: Sugar Alcohols as Stabilizers (B and D).
Mannitol (B) and Sorbitol (D) are the most frequently used osmotic stabilizers. They are ideal because they are "metabolically inactive," meaning the plant cells do not readily eat or break them down, ensuring the osmotic pressure remains constant throughout the experiment.

Step 2: Sugars as Stabilizers (A).
Glucose (A) (and sometimes sucrose) can also act as an osmoticum. While cells *can* metabolize glucose, it is often used in isolation media to provide both stability and an immediate energy source.

Step 3: Eliminating Non-Stabilizers.
PEG (C) is a fusogen used to stick cells together; it is not used as a general osmotic stabilizer for the long-term maintenance or "resting" of protoplasts.