. study a particular phenomenon in plants
Given below is the diagram of an apparatus used to study a particular phenomenon in plants:
(a) Name the apparatus.
(b) What is it used for?
(c) What is the role played by the air-bubble in this experiment?
(d) What is the use of the reservoir?
(e) What happens to the movement of the air-bubble if the apparatus is kept:
(i) In the dark
(ii) In sunlight
(iii) In front of a fan
Give a reason in each case.
(a) Ganong’s potometer
(b) Ganong’s potometer is used to measure the water intake of a plant which is almost equal to the water lost through transpiration.
(c) The movement of the air bubble and its position in the capillary tube indicates the volume of water lost through transpiration in a given time.
(d) The water in the reservoir can be released into the capillary tube by opening the stop cock. This allows the air bubble to restore back to its original position.
(i) If the apparatus is kept in the dark, there will be no transpiration as the stomata would be closed. As a result, there would be no movement of the air bubble and it would remain stable.
(ii) If the apparatus is kept in bright sunlight, the rate of transpiration will be more. As a result, the movement of the air bubble would be larger since there would be more loss of water due to transpiration.
(iii) If the apparatus is kept in front of a fan, the rate of transpiration will be more. As a result, the movement of the air bubble would be larger since there would be more loss of water due to transpiration as the velocity of wind/air increases.