1. Several answers are possible but most students will correctly observe that our scientific techniques are more sophisticated today.
2. Both act on elongating cells, though gibberellin is slower at this; gibberellin also stimulates cell division.
3. Answers will vary but should include a definition of thigmotropism and thigmonastic movement.
4. Answers will vary.
5. Answers will vary.
6. The experiments using flashes of light in the dark support the term long-night plants.
7. In phototropism, light sends auxin to the shaded portions of the plant. Phytochrome controls response to light. Phytochrome helps direct shoot phototropism.
TO THINK ABOUT
1. Answers will vary.
2. Answers will vary.
3. Ethylene.
4. Two trigger hairs must be touched in succession or one trigger hair must be touched twice within 15 seconds. This precludes the trap closing in the rain.
5. First ask what each plant's night requirement is. Then ask if some other factor, such as temperature, is also crucial to flowering.
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