Question

The figure given below represents an experimental set up with a weighing machine to demonstrate a particular process in plants. The experimental set up was placed in bright sunlight. Study the diagram and answer the following questions:

(i) Name the process intended for study. 

(ii) Define the above mentioned process. 

(iii) When the weight of the test tube (A & B) is taken before and after the experiment, what is observed ? Give reasons to justify your observation in A &B. 

(iv) What is the purpose of keeping the test tube B in the experimental set up ?

Answer 1

(i) Transpiration. 

(ii) It is the process in which water is lost in the form of vapour from the aerial parts of the plant. 

(iii) After the experiment, we observe test tube A is raised up i.e., a loss of weight. In test tube B, the weight remains unchanged. 

Reason: In test tube A, loses weight due to the plant transpires and loses water. In B there is no plant so there is no transpiration and the oil on the surface prevents direct evaporation and so weight remains unchanged. 

(iv) As a control experiment.