- A Gibberellins diffusing downward from the shoot apex to suppress lateral buds
- B Cytokinins transported upward from the root tip through the xylem stream
- C Auxin (IAA) from apical bud
- D Ethylene accumulating locally at axillary bud junctions
Correct answer: C. Auxin (IAA) from apical bud
Explanation: Auxin produced by the apical bud inhibits growth of lateral buds (apical dominance). Removing the apex allows lateral growth.
Concept context
Phases of plant growth, the five classical plant hormones plus newer ones, photoperiodism, vernalization, and seed dormancy.