what is phytohormone
Answers
Answer:
phytohormones refer to signal molecules that are vital to plant development. These molecules occur in very low concentrations and control various stages of development, including reproductive, stress tolerance, pathogen defense, organ size and embryogenesis. While this molecule only controls specialized glands in animals, it has a more crucial role to play in plants.
Explanation:
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.