Plant Hormones (T)

• What is the term for the growth of plant shoots towards light?

  Phototropism
• What hormone is suggested to be produced at the tips of plant shoots?

  Auxin
• Why did scientists cover the tips of the shoots with foil in their experiments?

  To block out light and test sensitivity of the tips
• What conclusion can be drawn from the shoots growing towards the light when the lower parts are covered with foil?

  The lower parts are not sensitive to light
• What is the process by which auxin helps shoots grow towards light?

  • Auxin is produced at the tip of the shoot
  • Auxin triggers cell growth
  • Light causes auxin to concentrate on the darker side
  • Cells on the darker side grow faster than those on the lighter side
  • This causes the shoot to bend towards the light
• What is the term for the growth of plant roots towards gravity?

  Gravitropism (or geotropism)
• How does gravity affect the distribution of auxin in plant roots?

  It causes auxin to concentrate on the lower side
• What effect does auxin have on cell growth in roots?

  Auxin inhibits cell growth in roots
• What are the roles of gibberellins and ethylene in plants?

  • Gibberellins: Important for starting the germination of seeds
  • Ethylene: Controls cell division and the ripening of fruits