Question

One of the Synthetic Auxin is
1. PAA
2. IAA
3. NAA
4. GA

Answer 1

Correct Answer - Option 3 : NAA

Concept-

• Plant growth hormones or phytohormones are simple molecules with complex chemical composition, that regulates the growth and physiology of plants.
• Based on their functions on the living plant body, they can be classified into two groups-
  • Plant growth promoters - Eg. Auxins, Gibberellins & cytokinins.
  • Plant growth inhibitors -Eg. Abscisic acid.
• Gaseous PGR like ethylene can be put into both groups, however, it is largely an inhibitor of growth activities.

Explanation-

• Auxins (from Greek ‘auxein’ : to grow) were first isolated from human urine.
• The term ‘auxin’ is applied to the indole-3-acetic acid (IAA), and to other natural and synthetic compounds having certain growth-regulating properties.
• They are generally produced by the growing apices of the stems and roots, from where they migrate to the regions of their action.
• NAA (naphthalene acetic acid) and 2, 4-D (2, 4-dichlorophenoxyacetic) are synthetic auxins.
• All these auxins have been used extensively in agricultural and horticultural practices.

Therefore NAA is one of the synthetic auxins.

IAA

• Auxins like IAA and indole butyric acid (IBA) have been isolated from plants.

GA

• Gibberellins are another kind of promotery PGR. GA denotes gibberellins.