Question

Write a note of the functions of abscisic acid.

Answer 1

Hint: Phytohormones or plant hormones are the chemical substances that are essential for the overall growth and development of plants. They are also called plant growth regulators (PGRs). Some phytohormones are growth-promoting hormones e.g. auxin while others are growth-inhibiting hormones e.g. abscisic acid.

Complete answer:
The abscisic acid is produced in the leaves, stems, fruits and seeds of the plant. Abscisic acid is a plant growth regulator that is known for its role in abscission and dormancy. But, it also regulates the growth and development of plants. It inhibits the growth and metabolism of plants.

Important functions of abscisic acid are:
- It inhibits the germination of seeds
- It is also called the stress hormone because it increases the tolerance of plants to various unfavourable conditions or environmental stresses. For example- it helps in the closing of stomata when there is less availability of water, this helps in the conservation of water in plants.
- When there are unfavourable conditions, abscisic acid induces dormancy in seeds. Hence, plays an important role in the development and maturation of seeds. It delays seed germination when there are unfavourable conditions.
- It also plays a major role in the development of buds. During winter, it directs the development of scales to protect the dormant buds.
- The production of abscisic acid increases when there is drought or freezing climatic conditions or excessive pollutants exposure.
- It protects the cells from dehydration by encouraging the roots to readily absorb water from the soil.
- It also controls the size of organs in plants.
- It is sprayed on the trees which regulate the dropping of fruits.

Note: The abscisic acid was discovered during the mid-1960s when three independent types of research were carried out. Three types of inhibitors (inhibitor-B, abscission II and dormin) were isolated and purified from plant cells. Chemically, all three were identified and named as abscisic acid.