Answer: The Pfr form.
- A The Pfr form
- B The Pr form
- C No phytochrome
- D An auxin form
Correct answer: A. The Pfr form
Explanation: Red light converts phytochrome to the active Pfr form, which promotes germination of light-sensitive seeds like lettuce.
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.