Question

Hormone antagonistic to ABA is
a. Gibberellin
b. Auxin
c. Ethylene
d. Cytokinin

Answer 1

Hormones are the chemical compounds which regulate various types of physiological process. In case of conditions like drought, plants undergo some osmotic stress where ABA( abscisic acid) is a natural stress hormone, usually produced in stressful situations.

Complete answer:
- Hormones in plants are called phytohormones, which produce in very little quantity.
- Normally plants are exposed to various kinds of situations like heat, drought, salinity, etc.
- Stress hormones are produced in the above given stressful situations so that it will help the plants to adapt to the extreme conditions.
- Some of the phytohormones like salicylate and Abscisic acid(ABA) combine and form the defense system to fight against the extreme environments.
- Along with them, Abscisic acid has some other functions, which include the abscission of leaves and at the same time, it induces the dormancy of the seeds.
- So there is a hormone that behaves as an antagonist to the Abscisic acid which is gibberellins.
- Gibberellins is also a plant hormone, where it Regulates the various developmental processes.
- It includes, elongation of stem, germination and it breaks the dormancy of seeds, and it regulates the flowering, and also in leaf and fruit senescence.
- Generally, gibberellins are produced in a great amount if the plants are exposed to colder environments.
- They promote cell elongation and they break the dormancy and promote the development of seed by acting as a chemical messenger.

Hence, the correct answer is option (A).

Note: Gibberellin acts as a chemical messenger or hormone, where it binds with calcium and receptors, and activates the calmodulin, where this whole complex binds to the DNA and stimulates the growth in embryos.