Generally, the lower leaves of the tree turn yellow while the leaves in the upper branches remain green. Give reason.

Explanation

### Step-by-Step Solution:

1. **Understanding Leaf Color Change**: The question asks why the lower leaves of a tree turn yellow while the upper leaves remain green. This phenomenon is often observed in many trees and plants.

2. **Identifying the Cause**: The primary reason for the yellowing of leaves is often linked to nutrient deficiencies, particularly a lack of essential minerals required for photosynthesis and overall plant health.

3. **Role of Magnesium**: One of the key nutrients involved in this process is magnesium. Magnesium is crucial for the formation of chlorophyll, the green pigment in leaves that is essential for photosynthesis.

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