a) the setup demonstrates the process of transpiration pull. Transpiration pull is the force with which water is pulled upwards from the roots to the leaves from where water is evaporated out via transpiration.

b) If a blower is placed close to the setup it will provide a wind speed due to which the rate of transpiration will increase this the level of water will rise even upwards as the transpiration pull will be more. Since when the wind intensity is more, its humid content is also less so it can carry away more number of water molecules from the aerial surfaces of the plant.

c) Phenyl mercuric acetate is an anti-transpirant. If it is sprayed on leaves, transpirational loss of water will cease or stop and mercy=ury levels will remain stable.