Question

The commonly used phytohormone for callus formation is:

• A. ABA
• B. Kinetin
• C. 2,4-D
• D. Zeatin

Hint:

For Callus Induction, always look for 2,4-D. It is the most effective synthetic auxin for making cells "forget" their identity and start dividing as a callus.

Answer 1

The Correct Option is C

Concept: Phytohormones (plant growth regulators) are essential for controlling cell division and differentiation in vitro. Callus induction typically requires a high concentration of auxins to trigger the dedifferentiation of explant tissues.

Step 1: Analyzing the Role of Auxins.
Auxins are primarily responsible for cell elongation and the initiation of cell division. In tissue culture, synthetic auxins are often more stable and potent than natural ones for inducing callus.

Step 2: Identifying 2,4-D.
2,4-D (2,4-Dichlorophenoxyacetic acid) is a powerful synthetic auxin. It is widely regarded as the "standard" hormone for callus induction and the initiation of somatic embryogenesis because it effectively reverts specialized cells back to a meristematic state.

Step 3: Evaluating Other Options.
ABA (Abscisic Acid) is a stress hormone and growth inhibitor. Kinetin and Zeatin are cytokinins, which are generally used for shoot induction or cell division in the presence of auxins, but they are not the primary drivers for initial callus formation like 2,4-D is.