PLANT RESPONSES

• Independent variable

  Light intensity
• Dependent variable

  Height of seedlings
• Investigating effect of light intensity on seedling height

  1. Place cotton wool in 3 petri dishes

  2. Soak with equal volumes of water

  3. Place 10 mustard seeds in each dish

  4. Allow seeds to germinate

  5. Water seedlings daily with same volume

  6. Ensure same number of seedlings in each dish

  7. Measure height of each seedling daily for 5+ days

  8. Record results in table

  9. Calculate mean seedling height per day

  10. Draw diagrams to show effect of different light intensities
• Control variables

  • Volume of water
  • Type of seed
  • Number of seedlings
• Seedlings in full sunlight and partial light have similar height
• Seedlings in the dark have grown the longest
• Seedlings in the dark

  Grow rapidly to reach light
• Seedlings in the dark

  Leaves are small and yellow
• Investigating effect of gravity on seedlings

  1. Place dish of seedlings on its side in the dark

  2. Shoots grow upwards against gravity

  3. Roots grow downwards towards gravity
• Gravity

  Causes auxin to build up on lower side of root, making it grow more slowly than upper side