CBSE Class 10 Answered

Aim: To show that carbon dioxide is necessary for photosynthesis

Procedure:

• Take a plant with destarched leaves.
• Insert one of its leaves in a conical flask containing potassium hydroxide.
• Leave the plant in sunlight.
• After a few hours, test the particular leaf and some other leaf of the same plant for the presence of starch.

Observation:

The leaf which was inserted in the conical flask stains brown, and the other leaf which is exposed to sunlight turns blue-black. 

Inference:

Potassium hydroxide in the flask absorbs carbon dioxide; thus, due to the absence of CO₂, the leaf fails to produce starch which proves that carbon dioxide is necessary for photosynthesis.