BotanyLesson 3 of 3 in the course Plant Form and Physiology

Plant Responses to Light, Gravity, Touch, and Biological Stress

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Plants cannot move to find better conditions, so they detect light and adjust their growth and development in place. This lesson introduces the major ways plants use light and explains how the phytochrome system helps them respond to light quality and seasonal timing.

Light provides energy for photosynthesis, but it also supplies information. Plants use light cues to coordinate their form, growth, and life cycle.

All flashcards

How does phytochrome respond to red and far-red light?
Red light converts Pr to physiologically active Pfr; far-red light converts Pfr back to Pr.
What role do cryptochromes play in plants?
They are blue-light receptors that help set the plant's circadian rhythm.
What is photoperiodism?
A biological response to the timing and duration of day and night.
What are two effects of gibberellins?
They can stimulate shoot elongation and promote seed germination.
How do jasmonates contribute to plant defense?
They promote defensive chemicals and volatile signals after wounding or herbivory.

Quiz questions

  1. In Boysen-Jensen's seedling experiment, what result supported the idea that a mobile chemical signal travels from the tip?Answer: Bending continued when permeable gelatin separated the tip from the base.
  2. Which description best defines a thigmonastic response?Answer: A touch-triggered movement that does not depend on the direction of touch.
  3. In a root responding to gravity, what does higher IAA concentration on the lower side do?Answer: It inhibits elongation there, helping the root curve downward.
  4. When soil water is low, what effect does abscisic acid have on stomata?Answer: It promotes stomatal closure, reducing water loss.
  5. Which comparison of thorns and spines is correct?Answer: Thorns are modified branches; spines are modified leaves.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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