Auxins

• What do auxins control and where?

  Plant growth in shoots and roots
• Where on the shoots and roots are auxins produce and what happens?

  tips, diffuses backwards to stimulate the cell elongation
• Where does auxin promotes growth and inhibit growth?

  growth in shoot, inhibits in roots
• Positively phototropism?

  Grow towards light
• Negatively phototropism?

  grow away from light
• Positively gravitropism?

  grow towards gravity
• Negatively gravitropism?

  grow away from gravity
• Shoots are positively phototropic

  • when shoot tip is exposed to light, more auxin accumulate on shaded region
  • this is to allow shoot to bend more towards light as cells elongate faster on shaded side
• Why is it good that shoot can bend more towards light?

  absorb more light for photosynthesis high enable plant growth
• What happens if a shoot is forced to grow in the dark?

  all shoots will be tall and spindly as auxins have accumulated all around the tip causing them to elongate quick on all side.
• What is the advantage of a taller shoot?

  Increased chances to sunlight.
• shoots are negatively phototropic

  1. when shoot grows sideways, gravity produces unequal amount of distribution of auxin in the tip, more auxin on lower side
  2. causes lower Side to grow faster, bending shoot upwards
• Roots are positively gravitropic:

  1. when root is sideways, there is more auxin on lower side
  2. auxin inhibits growth for shoots so cells on top will elongate and root bends downward
• Roots are negatively phototropic:

  1. if it starts being exposed to light, more auxin accumulates on more shaded side
  2. Auxin inhibits growth on more shaded side so root can bend downwards