plant responses

• What should you be able to describe by the end of the video?

  Investigate light or gravity effects on seedlings
• What is the independent variable in the light intensity experiment?

  Light intensity
• What is the dependent variable in the light intensity experiment?

  Height of the seedlings
• What is a control variable in this experiment?

  Volume of water
• How many mustard seeds are placed in each dish?

  10 mustard seeds
• Why is it important to have the same number of seedlings in each dish?

  To ensure a fair comparison
• How should the height of each seedling be measured?

  Hold the stems straight without damaging
• What should you do if one dish has more seedlings than another?

  Remove seedlings to equalize numbers
• Where should one dish be placed for full sunlight?

  On a very bright windowsill
• What is the purpose of measuring seedling height every day?

  To record growth over time
• What do the results show about seedlings in full sunlight versus partial light?

  Height is similar in both conditions
• Why do seedlings grow towards the light source?

  Due to phototropism and auxin concentration
• What happens to seedlings kept in the dark?

  They grow rapidly trying to reach light
• What happens to the leaves of seedlings in the dark?

  They become small and yellow
• Why can't seedlings carry out photosynthesis in the dark?

  They use up all their energy stores
• How can the effects of gravity on seedlings be investigated?

  By placing a dish of seedlings on its side
• What direction do the chutes and roots grow in relation to gravity?

  Chutes grow upwards, roots downwards
• How does auxin affect root growth in relation to gravity?

  Auxin inhibits growth on the lower side
• What is a common resource for questions on this practical?

  The vision workbook
• What are the steps to investigate the effect of light on seedlings?

  1. Place cotton wool in petri dishes.
  2. Soak with equal volumes of water.
  3. Add 10 mustard seeds to each dish.
  4. Leave in a warm place to germinate.
  5. Water daily with the same volume.
  6. Ensure equal number of seedlings in each dish.
  7. Measure height of seedlings.
  8. Place dishes in different light conditions.
  9. Record height daily for at least five days.
  10. Calculate mean height and draw diagrams.
• What are the effects of light intensity on seedling growth?

  • Similar height in full sunlight and partial light
  • Seedlings grow towards light due to phototropism
  • Dark seedlings grow rapidly but have small yellow leaves
• What are the effects of gravity on seedlings?

  • Chutes grow upwards against gravity
  • Roots grow downwards towards gravity
  • Auxin inhibits growth on the lower side of roots