Answer: Auxin.
- A Cytokinin
- B Auxin
- C Gibberellin
- D Ethylene
Correct answer: B. Auxin
Explanation: 2,4-D is a synthetic auxin used as a selective herbicide against dicot weeds.
Geometric growth (where both daughter cells keep dividing) produces this classic S-shaped curve: a slow lag phase, a rapid exponential phase, and a levelling-off stationary phase as nutrients or space become limiting - the same fundamental pattern seen in population growth.
Concept context
Phases of plant growth, the five classical plant hormones plus newer ones, photoperiodism, vernalization, and seed dormancy.