Question

4. An activity was designed to show that carbon dioxide is necessary for photosynthesis.
During this activity (a) Which chemical is used and why? (b) Why do we need two plants?
(c) Why do we cover both plants with bell jars? (d) What observation do you expect at the
end of experiment and why? ​

Answer 1

Answer:

To prove the necessity of carbon dioxide in photosynthesis following steps need to do

Insert a part of the leaf of a destarched plant into a conical flask containing potassium hydroxide.

Potassium hydroxide solution absorbs the carbon dioxide gas from the air present in the glass bottle.

Leave the plant sunlight.

After few hours, perform a starch test to this and another leaf of the same plant.

Observation-

Leaf exposed to the atmosphere are bluish black.

Leaf exposed to KOH does not change to blue-black colour

Result- Starch is present in the green part of the leaf.

Conclusion- Presence of starch proves that chlorophyll is necessary for photosynthesis as it traps sunlight.

Explanation: