Plant Hormones

• What are auxins?

  Plant hormones which control growth near the tips of shoots and roots
• What is phototropism?

  Plant response to light
• What is gravitropism?

  Plant response to gravity
• What happens when a shoot grows towards light?

  • More auxin accumulates on the side in the shade
  • Makes the cell grow faster on the shaded side so the shoot bends towards the light
• What happens when a shoot grows away from gravity?

  • Gravity produces unequal distribution so more auxins are on the lower side
  • This causes the lower side to grow faster causing the shoot to bend upwards
• What happens when roots grow towards gravity?

  • More auxin on the lower side
  • But in a root, extra auxin inhibits growth so the root elongates faster on the top, causing the root to bend downwards
• What else are auxins used for?

  • Killing weeds
  • Growing from cutting with rooting powder
  • Growing cells in tissue culture
• What are gibberellin?

  • Plant hormones which stimulate seed germination, stem growth and flowering
• How can gibberellins be used?

  • Controlling dormancy
  • Inducing flowers
  • Growing larger fruit
• What is ethene?

  Gas produced by the aging parts of a plant. Influences the growth of plant by controlling cell division
• What can ethene be used for?

  Speeding up the ripening of a plant