Question

Which of the following can be used for surface sterilization of plant material?

• A. Sodium chloride
• B. Sodium hydroxide
• C. Sodium sulphate
• D. Sodium hypochlorite

Hint:

Other common sterilants include Mercuric Chloride ($HgCl_2$), Calcium Hypochlorite, and Ethanol ($70\%$).
Always rinse the explant with sterile distilled water several times after using these chemicals.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question pertains to plant tissue culture techniques, specifically the process of removing microbial contaminants from the surface of an explant before inoculation.
Detailed Explanation:

• Surface Sterilization: Explants (plant parts like seeds, leaves, or stems) naturally harbor bacteria and fungi on their surfaces. To ensure sterile in vitro growth, these must be eliminated using chemical disinfectants.

• Sodium Hypochlorite ($NaOCl$): This is the most widely used surface sterilant in plant tissue culture. It is the active ingredient in commercial bleach. It acts by releasing chlorine, which effectively kills microbes while being relatively manageable for plant tissues at specific concentrations (usually $1\%$ to $10\%$) and exposure times.

• Comparison with other options:
- Sodium chloride (A): Common salt, not a disinfectant.
- Sodium hydroxide (B): A strong caustic base; it would damage or kill the plant tissue.
- Sodium sulphate (C): A salt used in various industrial processes, but not for sterilization.
Final Answer:
Sodium hypochlorite is the standard chemical agent used for the surface sterilization of explants in labs.