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27.1 Plant responses
  • Like animals, plants use a reception-transduction-response pathway when they respond to a stimulus.
  • Tropisms are growth responses in plants toward or away from unidirectional stimuli such as light and gravity.
  • Plants sometimes exhibit circadian rhythms (e.g., closing of stomata) that recur approximately every 24 hours.
  1. What is tropism and what does it mean to have a positive or negative tropism?
  2. How does a stem bend in response to light?
  3. How does auxin cause a root to bend in response to gravity?
  4. What are nastic movements and provide an example?
  5. What is a biological clock?
Essential Study Partner Summaries of major points
  1. Organisms respond to stimuli
  2. Tropisms
  3. Phototropism
  4. Gravitropism
  5. Thigmotropism
  6. Nastic movements
  7. Sleep movements
Art Review
27.2 Plant hormones
  • Some plant hormones stimulate growth, and other plant hormones inhibit growth.
  • The biochemical manner in which auxin and gibberellin function has been studied.
  • It now appears that various plant hormones interact to bring about a response to a stimulus.
  1. What is apical dominance and how is it controlled by the hormone auxin?
  2. What are the primary functions of gibberellins?
  3. What hormone promotes cell division in plants?
  4. What is senescence and what hormone can prevent it?
  5. What are the major functions of abscisic acid and ethylene?
Essential Study Partner Summaries of major points
  1. For plants to respond to stimuli....
  2. Auxin
  3. How auxins work
  4. Gibberellins
  5. Cytokinins
  6. Senescence
  7. Inhibitory hormones
  8. Ethylene
Art Review Art Quizzes
27.3 Photoperiodism
  • Plant responses that are controlled by the length of daylight (photoperiod) involve the pigment phytochrome.
  1. The physiological response of a plant to changes in day length is called _____________.
  2. What is the pigment which allows plants to determine day length and how does it function?
  3. What are some other known functions of phytochrome?
Essential Study Partner Summaries of major points
  1. Many physiological changes in plants are related to a seasonal change in day length
  2. Plants can be divided into three groups
  3. A long-day and a short-day plant can have same critical length
  4. Phytochrome and flowering
  5. Other functions of phytochrome
Art Review Art Quizzes

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