Question

What are plant hormones? Write their physiological roles in the plants.

Answer 1

Hormones

1. Hormones control the growth and development of a plant.
2. They are organic substances, other than nutrients which increase, decrease or modify the physiological processes in plants.
3. These substances are required in very small quantities.
4. There are five classes of plant hormones, viz., auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
5. They have a characteristic influence on the growth and differentiation of plant cells.
6. They exert their influence on germination, dormancy, flowering, senescence, and growth movements. Some of the plant hormones have similar physiological properties.
7. For instance, both auxins and gibberellins cause stem elongation.
8. Similarly, both abscisic acid and ethylene inhibit stem growth.
9. The growth and development of the plant body is the total of the interaction of different hormones present in the system.