Question

A herbicide which belongs to a synthetic-auxin type is

• A. Glyphocine
• B. Dicamba
• C. Thidiazuron
• D. Atrazine

Hint:

Classic synthetic auxin herbicides include:
2,4-D (2,4-Dichlorophenoxyacetic acid).
Dicamba (Benzoic acid derivative).
Picloram (Pyridinecarboxylic acid derivative).
These selective herbicides are used to control broadleaf weeds in grass crops.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Herbicides are chemical agents used to control unwanted vegetation.
Many selective herbicides mimic natural plant growth hormones.
Synthetic auxin herbicides act by overstimulating auxin signaling pathways, causing rapid, uncontrolled, and disorganized growth (epinasty) that ultimately leads to vascular rupture and plant death.

Step 2: Detailed Explanation:
Let us evaluate each herbicide option:
1. Dicamba (B): Dicamba (3,6-dichloro-2-methoxybenzoic acid) belongs to the benzoic acid chemical family.
It is a highly selective synthetic auxin herbicide.
Upon application, it mimics IAA, causing rapid cell elongation and epinasty in broadleaf weeds (dicots) while leaving monocots (grasses and crops like corn) unaffected, as they can rapidly metabolize or restrict the transport of the chemical.
2. Glyphosate (Glyphocine) (A): This is a broad-spectrum, non-selective systemic herbicide that acts by inhibiting the enzyme EPSP synthase in the shikimate pathway, blocking the synthesis of aromatic amino acids.
3. Thidiazuron (C): This is a synthetic compounds exhibiting cytokinin-like activity, used primarily as a defoliant in cotton harvest and as a plant tissue culture regulator.
4. Atrazine (D): This is a selective triazine herbicide that acts by binding to the plastoquinone-binding site of the D1 protein in Photosystem II, blocking photosynthetic electron transport.

Step 3: Final Answer:
The herbicide that belongs to the synthetic-auxin type is Dicamba, corresponding to option (B).