What is ABA ? Explain its function in the plant

What is ABA ? Explain its function in the plant.
A. 1) ABA means Abscisic acid. It is the plant growth inhibiting substance.
2) It induces dormancy in buds, tubers and many seeds.
3) ABA is responsible for the formation of separation layer or abscission layer between main plant and the leaf or between plant and flower or fruit. It results in the falling of leaves, fruits and flowers.
4) It prevents the water loss during drought conditions by closing the stomata.