Question

Prove with the help of an experiment that carbon dioxide is necessary for photosynthesis.

Answer 1

For proving the necessity of carbon dioxide for photosynthesis, the following steps are performed:

1. A potted plant is taken and placed in complete darkness for 24 to 72 hours to destarch it.
   
2. Take potassium hydroxide in a conical flask stoppered with a rubber cork. Insert one leaf (still attached to the parent plant) through a hole in the rubber cork. Potassium hydroxide absorbs all the leftover carbon dioxide from the flask.
3. The entire arrangement is exposed to sunlight for 6 hours.
4. The leaf placed in the conical flask with potassium hydroxide solution is tested with iodine solution. This does not turn blue-black.
   

Inference: The leaf trapped inside the conical flask did not perform photosynthesis as it did not receive any carbon dioxide. This is the reason why it did not answer a positive test for starch.