Question

Which of the following growth regulators is known as stress hormone?
A.Abscisic acid
B.Ethylene
C.GA3
D.Indole Acetic Acid

Answer 1

Plant growth regulators also known as plant hormones, are the chemical entities produced by the plant body that controls the growth and developmental process in plants. They are responsible for various aspects such as tolerance to stress, fruit ripening, and reproductive development.

Complete answer: Abscisic acid is an inhibitory hormone, it is also known as the stress hormone as it functions as a protective factor for the plants under stress, by generating adequate responses. For a plant under water stress, the ABA closes the stomata, during the water stress and the roots become deficient in water, a signal is sent to the leaves, and precursors of the hormones are synthesized at the site and is followed to the roots. ABA is then released by the roots and it then modulates the uptake of potassium and sodium by the guard cells, which makes it lose the turgidity and facilitates the closure of the pores.
Considering the other options:
Ethylene: It is also an inhibitory hormone. It affects the growth of the cell and can also determine the cell shape. Prevents elongation of the stem and causing cell-swelling. It also accelerates the process of fruit ripening.
GA3: Gibberellins aid in the process of germination of seeds. They promote cell elongation and also helps in the process of transition between vegetative and reproductive phases. The hormone is also important for the functioning of pollen during the process of fertilization.
Indole Acetic Acid: It is the most common auxin found in plants. It affects root initiation, cell enlargement, and bud formation processes. They also alter the plasticity of the cell wall. They also stimulate cambium production.
Thus the most appropriate answer given is option A, the Abscisic acid is also known as a stress hormone.

Note: Synthetic auxins such as 2,4- dichloro phenoxy acetic acid are used in the agriculture industry for weed control. They accelerate the defoliation process.