Question

Discuss the role of cobalt chloride paper while performing the experiment to demonstrate the process of transpiration.

Answer 1

Transpiration:

The process of loss of water in the form of water vapour from the aerial parts of the plants such as leaves is called transpiration.

Experiment to demonstrate the process of transpiration:

1. A small, well-watered potted plant with broad leaves is taken.
2. The plant used here is a dicot plant which has dorsiventral leaves.
3. The number of stomata varies on both surfaces in such plants.
4. The pot is then completely enclosed within a polythene bag and the mouth is tied tightly around the base of the stem.
5. Dry cobalt chloride paper is placed on the two surfaces of a leaf still attached to a plant.
6. Two glass slides are used to hold the position of paper and are tied together by elastic bands or clips.
7. The plant is then covered with a bell jar.
8. This experiment is performed to demonstrate the rate of transpiration on the two surfaces.
9. After some time, it is observed that water vapour condenses on the inner walls of the jar.
10. Additionally, the cobalt chloride paper turns pink on the lower surface while the cobalt chloride paper on the upper surface takes a longer time to turn pink.

Role of cobalt chloride paper:

1. The color of cobalt chloride paper changes from blue to pink due to transpiration.
2. Therefore, cobalt chloride paper is used to demonstrate transpiration and also the different rates of transpiration on both the surface of the leaves.