Phototropism

• How does positive phototropic response occur in shoots?

  Light causes IAA to move to the shaded side of the shoot, that side therefore has a higher concentration of IAA so it elongates and bends the plant towards the light.
• How does negative phototropic response occur in roots?

  Light causes IAA to move to the light side of the root, that side therefore has a higher concentration of IAA so it elongates and bends the root away from light.
• What is a tropism response?

  Where plants respond to stimuli via growth.
• What are the three stimuli that plants respond to?

  Light, gravity, and water.
• What is IAA (indoleacetic acid)?


  A type of auxin made in roots and shoots that controls elongation.
• What does a high concentration of IAA do to shoot cells?

  Causes elongation.
• What does a high concentration of IAA do to root cells?

  Inhibits elongation.