Deficiency symptom of N,K and Mg appears first in

Options

A. Younger leaves
B. Senescent leaves
C. Roots
D. Both(2) & (3)

Answer

To solve the question regarding the deficiency symptoms of nitrogen (N), potassium (K), and magnesium (Mg), we need to analyze where these symptoms appear first in the plant.

### Step-by-Step Solution:

1. **Understanding Deficiency Symptoms**: Deficiency symptoms occur when a plant lacks essential nutrients. In this case, we are looking at nitrogen, potassium, and magnesium.

2. **Mobility of Nutrients**: It is important to note that nitrogen, potassium, and magnesium are mobile nutrients. This means they can move from older parts of the plant to younger parts when there is a deficiency.

3. **Identifying Affected Plant Parts**: The options given are:
- A) Younger leaves
- B) Senescent leaves (old leaves)
- C) Roots
- D) Both senescent leaves and roots

4. **Analyzing the Options**:
- **Younger Leaves**: These would not show deficiency symptoms first since nutrients are typically moved to them from older parts.
- **Senescent Leaves**: These are older leaves that will show deficiency symptoms first because the nutrients are being redirected to support younger, developing tissues.
- **Roots**: While roots can show symptoms, they are not the first to show deficiency symptoms compared to leaves.
- **Both Senescent Leaves and Roots**: This option is incorrect because senescent leaves will show symptoms before roots.

5. **Conclusion**: Since nitrogen, potassium, and magnesium are mobile and will first be depleted from the older leaves to support the younger ones, the correct answer is **B) Senescent leaves**.

### Final Answer:
The deficiency symptoms of nitrogen, potassium, and magnesium appear first in **senescent leaves** (option B).

---