Brown leaf spots surrounded by chlorotic veins are charactersied by :

Options

A. Deficiency of Mn
B. Deficiency of Na
C. Toxicity of Mn
D. Toxicity of Mg

Answer

To solve the question regarding the characteristics of brown leaf spots surrounded by chlorotic veins, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Symptoms**:
- The symptoms described in the question are brown leaf spots surrounded by chlorotic (yellowing) veins. This indicates a specific nutrient-related issue in the plant.

2. **Identifying Nutrient Deficiencies and Toxicities**:
- The options provided include deficiencies and toxicities of various nutrients: manganese, sodium, magnesium, and toxicity of magnesium.

3. **Analyzing Micronutrient Roles**:
- Micronutrients, such as manganese and magnesium, play crucial roles in plant health. Manganese is essential for photosynthesis and enzyme functions, while magnesium is vital for chlorophyll production and enzyme activation.

4. **Linking Symptoms to Nutrient Issues**:
- Brown spots with chlorotic veins are often linked to nutrient imbalances. Specifically, excess magnesium can lead to reduced uptake of other essential nutrients like iron, which can cause chlorosis.

5. **Determining the Correct Answer**:
- Based on the analysis, the symptoms of brown leaf spots surrounded by chlorotic veins are primarily associated with the **toxicity of magnesium**. Excess magnesium can inhibit the uptake of other nutrients and disrupt normal plant functions.

### Final Answer:
The correct answer is **toxicity of magnesium**.