Question

Hormones that are to be used in tissue culture can be sterilized by

• A. Autoclaving
• B. Flame sterilization
• C. Air (HEPA) filtration
• D. Filter sterilization Correct Answer: (D) Filter sterilization

Hint:

Always filter sterilize thermolabile media additives like plant growth hormones, vitamins, and antibiotics to preserve their structural integrity.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Maintaining sterile conditions is crucial in plant tissue culture to prevent microbial contamination.
The sterilization method depends on the chemical stability of the components when exposed to heat and pressure.

Step 2: Detailed Explanation:
Autoclaving relies on pressurized steam (\(121^\circ\text{C}\) at 15 psi) to denature proteins and sterilize media.
Many plant hormones, such as gibberellic acid, zeatin, and indole-3-acetic acid (IAA), are thermolabile.
Exposing these heat-sensitive growth regulators to autoclaving temperatures destroys their chemical structure and biological activity.
Flame sterilization uses dry heat to sterilize inoculating loops and metal instruments, which is unsuitable for liquid reagents.
HEPA filters sanitize the air flowing through the laminar hood to maintain a clean workspace but do not sterilize solutions.
Filter sterilization is the standard method used for heat-sensitive organic compounds.
Liquid hormone preparations are passed through a membrane filter with a pore size of \(0.22\,\mu\text{m}\).
This size-exclusion membrane physically retains bacterial cells, fungal spores, and viral complexes while letting the active hormone molecules pass through unharmed.

Step 3: Final Answer:
Hence, the correct option is (D).