Question

The plant hormone used to destroy weeds in a field:

• A. IAA
• B. NAA
• C. IBA
• D. 2, 4-D

Answer 1

The correct option is D

2, 4-D

The correct option is D.

Explanation for the correct option:

1. Mode of Action: As stated by the Environmental Protection Agency of the USA, 2,4-Dichlorophenoxyacetic acid(2,4-D) kills plants in 3 ways:
   1. By altering the plasticity of these cell walls
   2. Increasing production of ethylene in plants
   3. And, influencing protein synthesis.

Explanation for the incorrect options:

Option A:

1. IAA is the main auxin that regulates plant development & growth process by participating in tissue differentiation and responding to gravity and light.
2. Functions of the Auxins:
   • Facilitate flowering in the plants
   • Used in process of plant propagation.

Option B:

1. NAA is 1-Naphthalene Acetic Acid which exhibits auxin activity.
2. It is used by gardeners to keep the lawns free from weeds.
3. It is involved in the initiation of roots in stem cuttings.
   

Option C:

1. IBA is the Indole-3-butyric acid, which induces rooting in stem cuttings of various kinds of plants.
2. It is a natural plant growth regulator.

Final answer: The plant hormone used to destroy weeds in a field 2,4-D.