Answer: Indole-3-acetic acid.
- A Indole-3-acetic acid
- B Gibberellic acid
- C Abscisic acid
- D Zeatin riboside
Correct answer: A. Indole-3-acetic acid
Explanation: The main natural auxin is indole-3-acetic acid (IAA).
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.