Question

Which of the following is used as herbicidal agent?

• A. DDT
• B. BHC
• C. 2,4 - D
• D. Chloroquene

Hint:

Selectivity is key in weed control.
2,4-D = Selective for Broad-leaved weeds.
Auxin Mimic = "Growth out of control."
Never use 2,4-D in a field of pulse crops (dicots) as it will kill them along with the weeds!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify a chemical compound from the list that is specifically used as a herbicide (a substance used to kill unwanted plants or weeds).
Detailed Explanation:

• Nature of 2,4-D:
2,4-D stands for $2,4$-Dichlorophenoxyacetic acid.
It was developed in the $1940$s and remains one of the most widely used herbicides in the world today.
It is a "systemic" herbicide, meaning the plant absorbs it through its leaves and translocates it throughout its tissues.

• Mechanism of Action:
2,4-D is a synthetic auxin (a plant hormone). It mimics the natural growth hormone indole-$3$-acetic acid (IAA).
When applied, it causes rapid, uncontrolled, and disorganized growth in plants, leading to the twisting of stems (epinasty) and eventually the death of the plant.
It is a "selective" herbicide; it generally kills broad-leaved weeds while leaving narrow-leaved grasses and cereals (like wheat or maize) unharmed.

• Analyzing Other Options:
DDT (Dichlorodiphenyltrichloroethane): This is a notorious insecticide used to kill mosquitoes and agricultural pests. It is an organochlorine and is banned in many countries due to its environmental persistence.
BHC (Benzene Hexachloride): Also known as Lindane, it is another organochlorine insecticide used for controlling soil-borne pests.
Chloroquine: This is a medicinal drug used primarily for the treatment and prevention of malaria in humans; it has no agricultural herbicidal use.

• Significance in Agronomy:
Herbicides like 2,4-D are essential for modern high-intensity farming as they reduce competition for water and nutrients between crops and weeds.

Step 3: Final Answer:
Among the given choices, 2,4-D is the only compound used as a herbicidal agent.