Plant hormones

• What is phototropism?

  Growth of plant shoots towards light
• What hormone is suggested to control phototropism?

  Auxin
• What happened when scientists removed the tips of the shoots?

  The shoots did not go towards the light
• What does covering the tips of the shoots with foil indicate?

  Tips are sensitive to light
• What was the result when the lower parts of the shoots were covered with foil?

  The shoots grew towards the light as normal
• How do shoots use auxin to grow towards light?

  • Auxin produced at the tip
  • Auxin triggers cell growth
  • Light causes auxin to concentrate on the darker side
  • Cells on the darker side grow faster
  • Shoots bend towards the light
• What is gravitropism also known as?

  Geotropism
• How does gravity affect auxin in roots?

  Auxin concentrates on the lower side
• What effect does auxin have on root cell growth?

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

  • Gibberellins: Start germination of seeds
  • Ethylene: Controls cell division and fruit ripening