- A Acropetal, moving upward from the root tip toward the shoot apex
- B Polar (from shoot apex downward, basipetal)
- C Non-directional, diffusing randomly through ground tissue without polarity
- D Confined entirely to root tissue, absent from the shoot system
Correct answer: B. Polar (from shoot apex downward, basipetal)
Explanation: Auxin has polar (unidirectional) transport: basipetal (away from apex, downward in shoots) via PIN efflux carrier proteins.
Concept context
Phases of plant growth, the five classical plant hormones plus newer ones, photoperiodism, vernalization, and seed dormancy.