Question

Which of the following substances serve as antitranspirants in plants?
A) Phenyl mercuric acetate
B) Aspirin
C) Silicon oil
D) All of the above.

Answer 1

Hint : The role of antitranspirants is to reduce the amount of transpired water from the plant to the atmosphere in order to prevent them from drying too quickly.

Complete answer : Before going forward to anti-transpirants we should know first about what is transpiration. So, transpiration is that process of water movement where the movement of water is from the plant to the atmosphere and evaporation from the aerial parts of the plants such as leaves, stem and flowers.
Water is necessary for plants but only a small amount of water is used up by the plants for their growth and metabolism, the rest of the remaining water which is about 97 % of the total water absorbed by the roots is lost by the process of transpiration and guttation.
Anti-transpirants are those compounds which are applied to the leaves of the plant to reduce the transpiration they are used on the surface of the leaves to preserve and protect the plants from drying too quickly. In present times, it is also used to protect leaves from fungal diseases.
Anti-transpirants work by blocking the active excretion of the hydrogen cation from the guard cells (recall stomata from guard cells), and this leads to the stomatal closure and hence also the reduced transpiration.
There are basically two types of anti-transpirants
a) Metabolic inhibitors and b) film-forming antitranspirants.
Metabolic inhibitors work by reducing the stomatal opening and increasing the leaf resistance to water vapours diffusion without affecting the carbon dioxide uptake. The anti-transpirants that works by this process are Phenyl Mercury Acetate (given as option A), ABA and Aspirin (given as option B) whereas the film-forming anti-transpirants form a colourless film on the leaf surface that allows only the diffusion of gases and not of the water vapours, for example, silicon oil (given as Option C).
Hence, the correct answer is option D. (All the given options are anti-transpirants).

Note :Anti-transpirants are those compounds which are applied to the leaves of the plant to reduce the transpiration they are used on the surface of the leaves to preserve and protect the plants from drying,