'Leaves dark green or blue green, development of often necrotic spots, lower leaves curved or cupped, stalks slender', are deficiency symptoms of …………………….. element.

Explanation

To solve the question regarding the deficiency symptoms of a specific element in plants, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Symptoms**: The symptoms listed are:
- Leaves that are dark green or blue-green.
- Development of necrotic spots on leaves.
- Lower leaves that are curved or cupped.
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