Question

list five main groups of natural plant growth regulators. write a note on there discovery​

Answer 1

Answer:

there are five types of plant hormones, namely, auxin, gibberellins (GAs), cytokinins, abscisic acid (ABA) and ethylene. In addition to these, there are more derivative compounds, both natural and synthetic, which also act as plant growth regulators.

Explanation:

hope it will help you

Answer 2

Plant growth regulators are small, simple organic substances of different chemical composition.

Plant growth regulators are of two types, they are (i) plant growth promoters (ii) plant growth inhibitors

Five main groups of plant growth regulators are:

$\bigstar$ Auxin :

• Auxin was discovered by Charles Darwin and his son Francis Darwin.
• They observed the coleoptiles of canary gross bending towards the source of light.
• It was concluded after a series of experiments that some substance produced at tip is responsible for the bending.
• Later this substance was extracted as auxin from the tip of coleoptiles in oat seedlings.

$\bigstar$ Gibberellic acid :

• The foolish rice seedlings disease was first observed by japanese farmer. In this disease the rice seedlings appear to grow taller than the natural plant.
• After several experiments this was isolated and identified by Gibberellic acid.

$\bigstar$ Cytokinins :

• F. Skoog and his co workers observed that the tobacco callus differentiated when extracts of vascular tissue, yeast coconut milk were added to the culture medium. This led to the discovery of Cytokinins.

$\bigstar$ Abscisic acid :

• Three independent researchers discovered inhibitor - B, abscission II and dormin. These were chemically similar and thus they are known as Abscisic acid.

$\bigstar$ Ethylene :

• HH cousins discovered Ethylene.
• It was observed that the unripe banana ripened faster when stored with ripe bananas.
• Later the substance promoting the ripening was found to be ethylene.