Plant growth factors

• What is IAA?

  • belongs to a family of hormones
  • produced in tips of shoots and controls cell elongation
  • tropism in plants controlled by substance called auxins
• How does IAA move through plants?

  diffusion
• Describe cell elongation in shoots?

  • IAA produced in meristem and diffused down the meristem
  • light causes IAA to diffuse from light side to shaded side of shoot
  • greater conc. of IAA builds on shaded than light side
  • this causes cell elongation on shaded sight compared to light side
  • this leads to shoot tip to bend towards light
• Describe cell elongation in roots

  • tip of the root produces IAA and diffuses along the root
  • gravity influences diffusion of IAA from upper side to lower side of root
  • greater conc. of IAA buils up on lower side than upper side
  • IAA inhibts elongation of root cells on the lower side
  • this causes root to bend downwards towards the force of gravity