Question

What are plant growth hormones? Describe their role in brief.

Answer 1

Plant growth hormones:

1. Plant hormones, or phytohormones, are chemical substances that help the plant respond to various environmental stimuli. They coordinate and regulate various growth and developmental aspects like cell elongation, division, differentiation, reproduction, response to biotic and abiotic stresses and senescence.
2. Phytohormones are synthesised in one part of the plant and transported to their target sites through diffusion, xylem vessels, or phloem tissues.
3. They are classified into two groups broadly based on their action-

a. Plant growth promoters- These phytohormones enhance cell division, cell elongation, formation of flowers, fruits and seeds. Auxins, gibberellins, and cytokinins are examples of plant growth promoters.

b. Plant growth inhibitors- These phytohormones inhibit plant growth. They promote dormancy and abscission in various plant parts like leaves, flowers, fruits, and seeds. Ethylene and abscisic acid are examples of plant growth inhibitors.

Characteristics of phytohormones

1. Phytohormones are simple organic molecules made of different chemical compositions.
2. Phytohormones are required in small amounts to bring about the action of different plant parts.
3. Phytohormones can target immediate sites or act on distant plant parts.

Role of plant growth hormones:

1. Phytohormones regulate developmental aspects in plants like elongation, division, and differentiation of cells.
2. Phytohormones influence the formation of various plant parts like leaves, stems, flowers, fruits, and seeds.
3. Phytohormones modulate longevity and senescence in plants.
4. Phytohormones also play an important role in defence against pathogens and tolerate stress.
5. Synthetic phytohormones play an important role in farming, horticulture, and the food industry. They are used to either delay or speed up the development of plant parts for commercial viability.