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Question
Write an experiment to demonstrate that CO2 is necessary for photosynthesis.
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Solution
Take a destarched plant. Insert one of its leaves in a conical flask, which contains potassium hydroxide. Leave it in the sunlight. After a few hours, test this and any other leaf of this plant for starch. The leaf which was exposed to the atmospheric air becomes blue-black, and the one in the flask containing KOH does not become blue-black after the iodine test. The experiment showing that CO2 is necessary for photosynthesis.
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