4.5 Plant Hormones

• Define Tropism 


  A plant growth response to the environment (directional response)
• Define Phototropism 


  Growth response to light
• What is gravitropism (geotropism)

  Growth response to gravity
• What is gravitropism also known as?

  • positive gravitropism
  • negative phototropism
• What is phototropism also known as?

  • positive phototropism
  • negative gravitropism
• What is Auxin used for?

  Controls growth in plants

  • controls phototropism and geotropism
• What is Ethene used for?

  • Cell division in plants
  • Ripening of fruits
• What is Gibberellins used for?

  Seed germination
• What does auxin do in shoots?

  promotes growth
• What does auxin do in roots?

  Inhibits growth
• Where is Auxin made?

  • plant shoot
  • root tips
• How does Auxin promote growth in plants in response to phototropism?

  1. Auxin moves to the shaded side of the plant
  2. Cells on the shaded side are elongated in the stem
  3. The plant bends and tilts towards the light due to the shaded side being heavier
• What should be soaked in water for the experiment?

  Cotton wool
• How many petri dishes are set up for the experiment?

  Three petri dishes
• How many mustard seeds are placed in each dish?

  Ten mustard seeds
• Where should the petri dishes be placed during the experiment?

  In a warm place
• What should be done daily to the petri dishes?

  Water each dish with equal amounts
• What should be done if a dish has too many seedlings?

  Remove excess seedlings
• What measurement should be taken for each seedling?

  Height in mm
• Where should the first petri dish be placed after germination?

  On a windowsill in full sunlight
• Where should the second petri dish be placed?

  In partial light
• Where should the third petri dish be placed?

  In darkness
• What should be recorded after measuring the seedlings?

  Results in a table
• What is your conclusion from the investigation (required practical)?

  The mean height of the seeds was the highest in dark areas because plant shoots use alot of energy to grow faster, in search for light for photosynthesis
• What are the uses of Auxin?

  • selective weedkillers
  • growth in tissue culture
  • rooting powder
• What are the uses of Ethene?

  Transport in retail
• What are the uses of Gibberellins?

  • end seed dormancy
  • flowering
  • increase fruit size
  • seedless fruit
• How have the artificial uses of plant hormones contributes to global warming?

  Deforestation and loss of biodiversity
• How have the artificial uses of plant hormones contributes to a loss of biodiversity?

  • weedkillers kills unwanted plants which are food for animals
  • seedless fruit cant reproduce meaning it reduces genetic variation