Question

Abscisic is called stress hormone as it is
A. Induces flowering
B. Breaks seed dormancy
C. Promotes leaf fall
D. Promotes stomatal closure

Answer 1

Hint: Plant Growth Regulator: Abscisic Acid (ABA) is regarded as one of the principle accelerators of abscission and bud dormancy. It is a naturally occurring growth inhibitor in plants and also known as stress hormone. But like other PGRs such as Auxins, Gibberellins, Cytokinins, and Ethylene, it also has other wide ranging effects on plant growth and development.

Complete answer:
Option- A – Induces flowering
ABA is known for its function of inhibiting flowering. It inhibits flowering in long day plants and stimulates flowering in some short day plants.
Option- B – Breaks seed dormancy
ABA is known for seed dormancy therefore by inducing dormancy it helps to tolerate desiccation and other factors unfavourable for growth. It ensures seed germination during favourable conditions.
Option- C – Pronotes leaf fall
ABA is produced in leaves during drought conditions to ensure plants conserve more water to withstand stress. Thus ABA promotes senescence of leaves.
Option- D -Promotes stomatal closure
ABA stimulates the partial stomatal closure in the epidermis and thus acts as antitranspirant and helps in tolerance of plants to various kinds of stresses.

So, the correct answer to this question is option – C “ Promotes stomatal closure”.

Note: ABA is known to be a stress hormone as it is involved in various inhibitory activity in plants in seeds, flowers and leaves. Although ABA also belongs to the group of Plant Growth Promoters. This plays an important role in plant responses to wounds and stresses of biotic and abiotic origin.