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life processes — Science STD 10 — Question

Gujarat BoardEnglish MediumSTD 10Sciencelife processes4 Marks
Question
How will you demonstrate that sunlight is essential for photosynthesis?
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Answer

 
  • By following simple experiment we demonstrate that sunlight is essential for photosynthesis:
  • Take a potted plant having a few large, simple leaves and keep the plant in total darkness for three days.
  • After three days wrap a strip of thin aluminium foil on any one leaf on both the surfaces or fix the Ganong’s light screen on the leaf as shown in the figure.
  • The aluminium foil should be so wrapped that a part of the leaf remains exposed
  • Keep this plant exposed to sunlight for about three days.
  • Pluck off the leaf and remove the aluminium foil from both of its surface or remove the Ganong’s light screen.
  • Place this leaf in a beaker containing alcohol.
  • Place this beaker in a boiling water bath and keep it there till the leaf becomes colourless.
  • Take out the leaf from the alcohol, wash it and clean it with normal tap water.
  • Place this colourless leaf in a petri dish and cover it with dil.
  • Iodine solution with the help of a dropper.
  • Observe the colour of the leaf after removing it from iodine solution.
  • The part of leaf exposed to light showed presence of starch.
  • From this observation, we can demonstrate, that light is essential for photosynthesis.

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