Question

Which plant hormone is primarily responsible for apical dominance?

• A. Cytokinin
• B. Auxin
• C. Gibberellin
• D. Ethylene

Hint:

Auxin is produced in the shoot apex and controls apical dominance. Removing the apical bud reduces auxin concentration, allowing lateral buds to grow and form branches.

Answer 1

The Correct Option is B

Concept: Plant hormones (phytohormones) are chemical substances that regulate growth and development in plants. One important growth phenomenon is apical dominance, where the growth of lateral buds is suppressed by the terminal (apical) bud. This occurs due to the action of certain plant hormones that regulate cell elongation and bud growth.

Step 1: Understanding apical dominance. Apical dominance is the phenomenon in which the main growing point of the plant (apical bud) inhibits the growth of lateral or side buds. This ensures that the plant grows vertically and the main stem dominates over side branches.

Step 2: Role of Auxin. The plant hormone Auxin is produced in the apical meristem (tip of the plant). It moves downward through the stem and suppresses the growth of lateral buds. As a result:
• The apical bud grows actively.
• The lateral buds remain dormant. If the apical bud is removed, the level of auxin decreases and the lateral buds start growing, leading to branching.

Step 3: Conclusion. Therefore, the plant hormone primarily responsible for apical dominance is Auxin.