Growth Regulatory Substances of Plant - QS Study
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Growth Regulators There are some biochemical substances, small amount of which regulate the growth of plants. These substances are produced in the plant bodies. As they regulate the plant growth so they are called growth regulators. Earlier they were called Hormone. As they are produced in plants they are now named phytohonnone. Phyto- means plant. Growth regulators are divided mainly into two types: –

(1) Growth promoter and

(2) Growth inhibitor.

Growth promoters are Auxin, Gibberellin, Cytokinin and Flowering honnone. And Growth inhibitors are Donnin or absecic Acid.


Influence of Auxin: (i) Auxin increases the length of the cell, (ii) Produce apical dormancy (iii) Initiates the formation of root, (iv) Help to produce seedless fruits.

Uses of Auxin: (1) Used for germination of seeds (2) As Auxin Initiate root formation so it is used in grafting of mango, litchi, Psidium etc. plants. (3) It used in case of early fruit fall. (4) Auxin also used in production of seedless fruits, in floriculture, tissue culture and in management of weeds.

Influence of Gibberellin: (1) Gibberellin increases the length of stem. Breaks the dormancy of seeds and buds (3) Help to bloom the flower.

Influence of Cytokinin: Cytokinin accelerates cell division. Uses of Cytokinin: (1) Used for production of seedless fruits (2) In tissue culture.

Abscisic Acid: Leaves and buds droped by its influence. inhibit growth of bud.