Question

Mention various growth hormones found in plants

Answer 1

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⭕ The control and coordination in plants is done by plant or phyto hormones.

⭕ Abscisic acid

● It is growth inhibitor.

● It promotes dormancy in seeds and buds.

● It promotes the closing of stomata.

● It promotes wilting and falling of leaves.

● It helps in detachment of flowers and fruits from plants.

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Answer 2

Types of Phytohormones.

The major types of plant hormones which are involved in the control and coordination in plants are as follows:

(i) Auxins are the group of plant hormones synthesised at the shoot-tip of the plant body .

• It promotes cell elongation, root formation, cell division, respiration and other physiological processes like protein synthesis, water uptake and protoplasmic permeability.

• Auxins also play an important role in the development of seedless fruits.

(ii) Gibberellins stimulate stem elongation, seed gennination and flowering.

• The maximum concentration of gibberellins is found in fruits and seeds.

(iii) Cytokinins are produced in dividing cells throughout the plant

• In mature plants, cytokinins are produced in the root tips and are transported to the shoots.

• Cytokinins promote cell division and also helps in breaking the dormacy of seeds and buds and regulate the phloem transport.

• Cytokinins delay the ageing in leaves and promote the opening of stomata.

(iv) Abscisic Acid (ABA) : It is a growth inhibitor which reverses the growth-promoting effects of auxins and gibberellins.

Its effect include wilting of leaves.

• It causes dormancy of seeds, tubers and bulbs.

• It promotes the closing of stomata and is responsible for the loss of RNA, proteins and chlorophylls.