Answer: auxin.
- A auxin
- B abscisic acid
- C ethylene
- D florigen
Correct answer: A. auxin
Explanation: Auxin promotes cell elongation, especially in shoots.
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.