Explain with activities plants need H2O and co2

Aim: Tp prove carbon dioxide and water are the essential aw materials for plants

Apparatus required:

  • A healthy potted plant
  • A wide-mouthed glass bottle with a split cork
  • Potassium hydroxide solution (KOH)
  • Starch solution.


  • Take a healthy potted plant and place it in the darkroom for two to three days
  • In a wide-mouthed glass bottle add 10-15 ml of potassium hydroxide solution and split the cork vertically
  • Then insert half part of a leaf into a glass bottle through the split cork and the other half of the leaf should be exposed to air
  • Allow this apparatus undisturbed for 4 hours
  • After 4 hours detach the leaf from the plant, remove from the bottle and test it with the starch solution.

Observation from the experiment:

  • The half part of the leaf kept inside the glass bottle (KOH solution) did not show any color change.
  • The other half part exposed to surroundings turned its color to dark brown which shows the presence of starch.


We can conclude that carbon dioxide and water are essential for photosynthesis. Both the portion of leaf received the same amount of water, chloroplasts, and sunlight but the half part which was inside the glass bottle did not receive carbon dioxide and water hence the photosynthesis process did not occur here.

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