A lawn is found to be having dicot weeds. The PGR that the gardener must use to obtain weed free lawn is

Options

A. 2,4-D
B. `GA_3`
C. NAA
D. ABA

Answer

To determine the appropriate plant growth regulator (PGR) for eliminating dicot weeds from a lawn, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Type of Weeds**: The question specifies that the lawn has dicot weeds. Dicotyledons (dicots) are a group of flowering plants that have two embryonic leaves or cotyledons.

2. **Understand Plant Growth Regulators (PGRs)**: PGRs are substances that influence the growth and development of plants. They can be natural or synthetic and include auxins, gibberellins, cytokinins, abscisic acid, and ethylene.

3. **Review the Options**: The PGRs mentioned in the transcript are:
- 2,4-D (2,4-Dichlorophenoxyacetic acid)
- GA-3 (Gibberellic acid)
- NAA (Naphthalene acetic acid)
- ABA (Abscisic acid)

4. **Analyze the Function of Each PGR**:
- **2,4-D**: This is a synthetic auxin that is commonly used as a herbicide. It is effective in killing dicot weeds while leaving monocots (like grasses) unharmed.
- **GA-3**: Primarily promotes stem elongation and seed germination, not effective against weeds.
- **NAA**: Used for rooting and as a plant growth regulator but not specifically for weed control.
- **ABA**: Known as a stress hormone, it regulates processes like stomatal closure and dormancy, not for weed control.

5. **Select the Appropriate PGR**: Given that 2,4-D is specifically designed to target and kill dicot weeds without affecting monocots, it is the ideal choice for the gardener to use in order to achieve a weed-free lawn.

### Conclusion:
The plant growth regulator that the gardener must use to obtain a weed-free lawn is **2,4-D (2,4-Dichlorophenoxyacetic acid)**.

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