Question

The figure given below represents an experimental setup with a weighing machine to demonstrate a particular process in plants. The experimental setup 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 setup?

Answer 1

(i) Transpiration
(ii) Transpiration is a process by which water is lost in the form of  water vapour from the aerial parts of the plant.
(iii) Weight of test tube A before the experiment was more than its  weight after the experiment. This is because water from test tube A has evaporated due to transpiration.Weight of test tube B remains the same before and after the experiment, because no loss of water occurs in test tube B.
(iv) Test tube B is used here as a control. This makes the observation of the change in test tube A easy.