Question

Which of the following plant growth regulator is NOT used as auxin in plant tissue culture?

• A. IBA
• B. BAP
• C. IAA
• D. 2, 4-D

Hint:

Auxins = Rooting and Callus (IAA, IBA, NAA, 2,4-D).
Cytokinins = Shooting and Division (BAP, Kinetin, Zeatin, TDZ).
Remember: BAP ends with "purine," a base used for cytokinins.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the plant growth regulator (PGR) in the list that does not belong to the Auxin class. Auxins and Cytokinins are the two most critical hormone groups used in plant tissue culture to control morphogenesis.

Step 2: Detailed Explanation:

• Auxins: Auxins are responsible for cell elongation, apical dominance, and root initiation. Common auxins used in the lab include:
- IAA (Indole-3-acetic acid): The primary natural auxin.
- IBA (Indole-3-butyric acid): A natural/synthetic auxin commonly used for root induction.
- 2,4-D (2,4-Dichlorophenoxyacetic acid): A potent synthetic auxin often used to induce callus formation.

• Cytokinins: Cytokinins promote cell division (cytokinesis) and shoot organogenesis. They are chemically distinct from auxins.

• Characterizing BAP: BAP (6-Benzylaminopurine) is a widely used synthetic Cytokinin. It is essential for inducing multiple shoot buds from explants in tissue culture.

• Morphogenesis Balance: In tissue culture, a high Auxin:Cytokinin ratio promotes rooting, while a high Cytokinin:Auxin ratio (like adding more BAP) promotes shooting.

Step 3: Final Answer:
BAP is a cytokinin, whereas IBA, IAA, and 2,4-D are all members of the auxin hormone group.