Question

Which of the following combination is effective in the regeneration of plant roots?

• A. High cytokinin low auxin ratio
• B. Low cytokinin high auxin ratio
• C. High cytokinin high auxin ratio
• D. Low auxin low cytokinin ratio

Hint:

Think: Auxin for Anchors (Roots) and Cytokinin for Canopy (Shoots).

Answer 1

The Correct Option is B

Concept: The Skoog and Miller hypothesis established that the type of organogenesis (root vs. shoot formation) is determined by the ratio of two classes of hormones: Auxins and Cytokinins.

Step 1: The Role of Auxin in Rooting.
Auxins are the primary hormones responsible for root initiation. A high concentration of auxin relative to cytokinin triggers the cells in the callus or explant to differentiate into root tissues (rhizogenesis).

Step 2: Comparing the Ratios.

• High Auxin Low Cytokinin: Promotes Root formation.
• Low Auxin High Cytokinin: Promotes Shoot formation.
• Equal Ratios: Typically results in continued Callus growth.

Step 3: Conclusion.
To regenerate roots specifically, one must use a medium where the auxin levels significantly outweigh the cytokinin levels.