Tropism

• What type of stimulus does phototropism respond to?

  Light
• What is a tropism?

  A directional response to a stimulus
• What process enables a plant to grow in a particular direction?

  Cell elongation
• What type of stimulus does gravitropism respond to?

  Gravity
• Which chemical controls cell elongation in plants?

  Indoleacetic acid (IAA)
• In shoot tips, where does IAA cause cell elongation?

  Where IAA concentration is highest
• Why does a plant lean towards the light?

  IAA is highest on the dark side
• How does IAA affect cell elongation in root tips?

  It prevents cell elongation
• What effect does gravity have on IAA settling in root tips?

  IAA settles towards gravity
• How does IAA affect root cells with respect to gravitropism?

  It inhibits cell elongation making it positive
• What triggers plant growth factors to regulate plant growth?

  A directional stimulus
• What are plant growth factors?

  Chemicals regulating plant growth
• What is taxis?

  Response to a directional stimulus
• What benefit does taxis provide to mobile organisms?

  Helps stay in a favorable environment
• What is kinesis?

  Response to a non-directional stimulus
• How does kinesis help organisms stay in a favorable environment?

  Via increased speed and turning