Answer: abscisic acid.
- A abscisic acid
- B plain auxin
- C plain cytokinin
- D plain gibberellin
Correct answer: A. abscisic acid
Explanation: Abscisic acid and ethylene together promote leaf senescence and shedding.
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.