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The signaling molecule for flowering might be released earlier than usual in a long-day plant exposed to flashes of
- A. far-red light during the night.
- B. red light during the night.
- C. red light followed by far-red light during the night.
- D. far-red light during the day.
- Correct Answer: Option B
How may a plant respond to severe heat stress?
- A. by reorienting leaves to increase evaporative cooling
- B. by creating air tubes for ventilation
- C. by producing heat-shock proteins, which may protect the plant's proteins from denaturing
- D. by increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity
- Correct Answer: Option C
Charles and Francis Darwin discovered that
- A. auxin is responsible for phototropic curvature.
- B. red light is most effective in shoot phototropism.
- C. light destroys auxin.
- D. light is perceived by the tips of coleoptiles.
- Correct Answer: Option D
Auxin enhances cell elongation in all of these ways except
- A. increased uptake of solutes.
- B. gene activation.
- C. acid-induced denaturation of cell wall proteins.
- D. cell wall loosening.
- Correct Answer: Option C
If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent flowering?
- A. 16 hours light/8 hours dark
- B. 14 hours light/10 hours dark
- C. 4 hours light/8 hours dark/4 hours light/8 hours dark
- D. 8 hours light/8 hours dark/light flash/8 hours dark
- Correct Answer: Option B
A plant mutant that shows normal gravitropic bending but does not store starch in its plastids would require a reevaluation of the role of ________ in gravitropism.
- A. auxin
- B. calcium
- C. statoliths
- D. differential growth
- Correct Answer: Option C
The hormone that helps plants respond to drought is
- A. auxin.
- B. abscisic acid
- C. cytokinin
- D. ethylene
- Correct Answer: Option B
Suppose a plant had a photosynthetic pigment that absorbed far-red wavelengths of light. In which of the following environments could that plant thrive?
- A. on the surface of a lake
- B. on the forest floor, beneath a canopy of taller plants
- C. on the ocean floor, in very deep waters
- D. on mountaintops, closer to the Sun
- Correct Answer: Option B
Mammalian eyes sense light because the photoreceptor cells have molecules called opsins, which change structure when exposed to light. Which of the following plant molecules would be analogous to mammalian opsins in their light-sensing ability?
- A. auxin and phytochrome
- B. auxin and Pfr
- C. Pfr and phytochrome
- D. cytokinins and phototropins
- Correct Answer: Option C
Which of the colors of visible light induces curvature in coleoptile most effectively?
- A. red
- B. blue
- C. violet
- D. orange
- Correct Answer: Option B