Question

Optimum pH for protoplast culture is -

• A. 6.5 to 7.0
• B. 5.5 to 5.9
• C. 4.5 to 4.9
• D. 7.5 to 7.9

Hint:

Remember that almost all standard plant tissue culture media (MS, B5, etc.) are adjusted to a pH of \(\sim\)5.8 before sterilization. This is a crucial number to memorize for any plant biotechnology exam.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
This is a factual question about the specific environmental requirements for in vitro culture of protoplasts (plant cells without cell walls). The pH of the culture medium is a critical factor for cell viability and growth.
Step 2: Detailed Explanation:
Protoplasts are extremely fragile due to the absence of a protective cell wall. The pH of the culture medium affects nutrient uptake, membrane stability, and enzyme activity.
For most plant tissue culture applications, including protoplast culture, the optimal pH of the medium (like MS medium) is adjusted to be slightly acidic before autoclaving.
The generally accepted range is between 5.5 and 5.9. A pH of 5.7 or 5.8 is very commonly used.
pH values below 5.0 can lead to nutrient precipitation and inhibit growth.
pH values above 6.0 can also cause problems with the availability of certain ions and promote the growth of contaminants.
Step 3: Final Answer:
The optimum pH range for protoplast culture is 5.5 to 5.9.