Plant hormones

• Phototropism


  Plants growing towards light
• How phototropism works


  1. Shoot tips produce auxin hormone

  2. Light causes auxin to concentrate on darker side of shoot tip

  3. Auxin spreads down shoot

  4. Cells on darker side grow faster

  5. Shoot grows towards light
• Gravitropism/Geotropism


  Plant roots growing towards gravity
• How gravitropism works


  1. Auxin produced in root

  2. Gravity causes auxin to concentrate on lower side

  3. Auxin inhibits cell growth on lower side

  4. Upper side grows faster

  5. Root grows towards gravity
• Gibberellins


  • Important for starting seed germination
• Ethylene


  • Controls cell division and fruit ripening