Biology
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:
- In the dark
- In sunlight
- In front of a fan
Give a reason in each case.
Transpiration
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Answer
(a) Name of the apparatus is Ganong's potometer.
(b) Ganong’s potometer is used to measure the rate of water intake by a plant.
(c) The air bubble which was introduced into the horizontal graduated capillary tube moves along as transpiration proceeds. As the water is lost from the twig, a suction force is set up which pulls the water from the beaker and the bubble in the capillary tube moves along.
(d) Reservoir is used to release the water into the capillary tube by opening the stop cock.
(e) The movement of air bubble is affected as follows:
- 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.
- During the day, the stomata are open to facilitate the inward diffusion of CO2 for photosynthesis. At night they are closed. Therefore, more transpiration occurs during the day. As a result, the movement of the air bubble would be larger since there would be more loss of water due to transpiration.
- 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.
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