Question

What are plant hormones? Name the plant hormones responsible for the following: (i) Growth of stem (ii) Promotion of cell division (iii) Inhibition of growth

Answer 1

Plant hormones:

1. Plant growth substances, phytohormones, and plant growth regulators describe plant hormones.
2. They are small, simple compounds with a wide range of chemical properties.
3. Examples - Auxins, Gibberellins, Cytokinins, Ethylene, and Abscisic acid.

(i) Growth of stem - Gibberellins

1. Gibberellins promote stem elongation.
2. They are utilized to increase the length of grape stems because of their capacity to promote an increase in axis length.
3. Bolting (internode elongation just prior to blooming) is similarly promoted by gibberellins in beets, cabbages, and many other rosette-forming plants.

(ii) Promotion of cell division - Cytokinin

1. Cytokinins promote cell division.
2. Natural cytokinins are produced in areas with rapid cell division, such as root apices, growing shoot buds, and immature fruits.

(iii) Inhibition of growth - Abscisic acid (ABA)

1. ABA is a plant growth inhibitor.
2. ABA promotes the closing of stomata and increases plant tolerance to various stressors.
3. As a result, it's also known as the stress hormone.