Why is that in certain plants deficiency symptoms appear first in younger parts of the plant while in others they do so in mature organs ?

Explanation

### Step-by-Step Solution:

1. **Understanding Deficiency Symptoms**: Deficiency symptoms in plants refer to the visible changes that occur when a plant lacks essential mineral nutrients. These symptoms can manifest as morphological changes, indicating which nutrient is deficient.

2. **Mobility of Nutrients**: The key factor that determines where deficiency symptoms appear in a plant is the mobility of the nutrient in question. Nutrients can be classified based on their mobility within the plant.

3. **Mobile Nutrients**: Certain nutrients, such as nitrogen, potassium, and magnesium, are highly mobile. This means that when there is a deficiency, these nutrients can be relocated from older, mature parts of the plant to younger, growing parts. As a result, deficiency symptoms for these nutrients will first appear in the younger parts of the plant.

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