List five main groups of natural plant growth regulators. Write a note on the discovery, physiological functions and agricultural/horticultural applications of any one of them.

Asked by Pragya Singh | 1 year ago |  79

##### Solution :-

The five main groups of natural plant growth regulators are: -

i. Auxins

ii. Gibberellic acid

iii. Cytokinins

iv. Ethylene

v. Abscisic acid

Discovery, physiological functions and agricultural/horticultural applications of Auxins are summarised as follows: -

Charles Darwin and Francis Darwin made the first observations about the effects of auxins when they noticed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source (phototropism). It was determined after a series of experiments that the tip of the coleoptile was the site of transmittable influence which results in the bending of the entire coleoptile. F.W. Went isolated auxin from the tips of the coleoptiles of oat seedlings.

Physiological Functions:

They control plant cell growth.

They cause the phenomenon of apical dominance i.e.; the growing apical buds inhibit the growth of the axillary buds.

They control division in the vascular cambium as well as xylem differentiation.

They also induce parthenocarpy.

They prevent the abscission of leaves and fruits.

Horticulture Application:

They help in the initiation of rooting in stem cuttings, which is a popular method of plant propagation.

They are used as herbicides. Example: - $\text{2-4 D}$ is a weedicide used to kill dicotyledonous weeds.

They induce parthenocarpy. Example: - Tomatoes.

They also promote flowering. Example: - Pineapples.

Answered by Abhisek | 1 year ago

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