Question

Which one is an antitranspirant hormone?
a. Auxin
b. Cytokinin
c. Abscisic acid
d. Gibberellin

Answer 1

Hint: An antitranspirant hormone reduces the transpiration process by closing the stomata during the water stress conditions. So, this hormone is also known as a stress hormone in plants.

Complete answer:
Transpiration is the process of loss of water in the form of water vapours, generally occurring in the aerial parts of a plant. In normal conditions, transpiration is found to be necessary for water and nutrient absorption from the cell, reduce the temperature of leaves, etc. During stress conditions such as water scarcity in the soil or drought, this process can lead to the death of the plant. Therefore, there should be a decrease in the transpiration rate.

Transpiration is of four types:
> Stomatal transpiration occurs through stomata which are found on the epidermis of leaves and green stem. These stomata contribute about fifty to ninety-seven percent of the total water transpired.

> Cuticular transpiration is responsible for about three to ten percent of total transpiration.
Lenticular and Bark transpiration, contributes about two percent of total water loss through transpiration from lenticels and bark of wood stem.

Since transpiration is mainly contributed by stomata. abscisic acid (AbA), a plant growth regulator promotes the closure of stomata. This reduces the transpiration rate and increases the water stress resistance capacity of the plant.
- Auxin is a plant growth regulator that is responsible for embryo development, light-sensitive growth of the stem, apical dominance, etc.
- Cytokinin, a plant hormone primarily responsible for cell division and leaf senescence in plants.
- Gibberellin is a phytohormone, responsible for several developmental processes such as seed germination, stem elongation in young plants, trigger floral development, etc.

Hence, The correct answer is option (C).

Note: Abscisic acid is a stress hormone and also controls the bud and seed dormancy along with stomatal opening and closing. It is known as an inhibitory plant growth regulator and works as an antagonist to Gibberellic acid. It helps the seed to fight with desiccation, so it is also called a Desiccation hormone.