Plant Harmons

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Plant Hormones

Following five hormones are found in plants -
1. Auxins
2. Gibberellins
3. Cytokinins
4. Abscisic Acid or ABA
5. Ethylene


Auxins was discovered by Darwin in the year 1880. This is the hormone which controls the growth of plants. Its formation takes place in the apical parts of the plants.
Its main functions are -
1. It prevents the separation of the leaves.
2. It destroys the straws.
3. It saves the crops from falling


It was discovered by a Japanese scientist Kurosava in the year 1926. The growth hormone gibberellins was first extracted from fungus in 1938 by Yabuta and Sumiki.
Its main functions are -
1. It turns the dwarf plants into long plants. It helps in creating flowering.
2. It help in breaking the dormancy of plant.
3. It motivates the seeds to be sprout.
4. It increases the activity of cambium in the wooden plants.
5. Large sized fruits and flowers can be produced by its scattering


It was discovered by Miller in the year 1955 but it was named by Lethem.
Its main functions are -
1. It naturally works in coordination with auxins.
2. It help in cell division and development in the presence of auxins.
3. It help in breaking the dormancy of seed.
3. It is helpful in making RNA and protein.

Abscisic Acid or ABA

This hormone was initially discovered by Carnes and Adicote and later on by Waring.
Its main functions are -
1. This hormone is against to the growth.
2. It keeps the seeds & bud in dormant condition.
3. It plays main role in separation of leaves.
4. It delays in flowering of long day plant.


This is the only hormone found in gaseous form. In 1962 Burg proven it as harmone.
Its main functions are -
1. It helps in the ripening the fruits.
2. It increases the number of female flowers.
3. It motivates the separation of leaves, flowers and fruits.
» Gas used for artificial ripening of fruit is ethane or ethylene.


It is formed in leaves but helps in blooming of the flowers. Therefore, it is also called flowering hormones.


This is a type of dicarboxylic acid. It is formed in injured cells by which the injury of plants is healed.
» The concept of tissue culture was introduced by Haberlandt.

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