Question

Define the term transpiration. Design an experiment to demonstrate this process.

Answer 1

Transpiration :

1. Transpiration is the process of loss of water in the form of water vapour through the aerial parts of the plant.
2. Most of the transpiration is carried out by the leaves with the help of stomatal pores on it.
3. Transpiration creates a suction force that helps in the upward movement of water and minerals from roots to different parts of the plants.
4. It maintains osmosis and keeps the cells rigid.

Experiment no 1: Bell jar experiment

Procedure :

1. Take a well watered potted plant and keep the plant on the glass plate and cover it with a bell jar.
2. Apply vaseline or grease at the base of the bell jar to prevent outer air from coming inside, making it air tight.
3. Keep the whole apparatus in light for about two to three hours and observe.

Observation :

1. Few waterdrops are observed on the inner side of the bell jar.

Result :

1. Transpiration occurs from potted plants in the form of water vapour which condenses to form water droplets.

Experiment no 2 : Cobalt chloride experiment.

Procedure :

1. A plant with broad leaf is taken and is covered with the polythene bag to escape the water vapour from the pot.
2. The entire set up is placed in the bell jar, containing the piece of cobalt chloride paper.
3. Another control setup is designed as a control experiment without the plant but with cobalt chloride paper.

Observation :

1. The change in the cobalt chloride paper, present in the first bell jar ,having the plant turns from blue to pink. This is because the cobalt chloride paper reacts with water vapour, lost from the plant.
2. But no color change was seen in the second bell jar, without the plant.

Result :

1. The change in the cobalt chloride paper ensures the occurrence of transpiration in the plant.