Deficiency of mobile elements first appear on:

Options

A. older leaves
B. Apical meristems
C. Younger leaves
D. Flower petals

Answer

To answer the question about where the deficiency of mobile elements first appears in plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Nutrients**:
- There are two categories of nutrients in plants: mobile and immobile elements. Mobile elements can be transported within the plant, while immobile elements cannot.

2. **Identify the Symptoms of Deficiency**:
- When there is a deficiency of mobile elements, the symptoms will first appear in the older leaves of the plant. This is because mobile elements can be relocated from older leaves to support new growth in younger leaves and meristematic tissues.

3. **Reasoning Behind the Location of Symptoms**:
- As the plant grows, nutrients from older leaves are used to support the development of new tissues. When mobile elements are deficient, these nutrients are drawn from the older leaves, leading to visible deficiency symptoms in those leaves.

4. **Conclusion**:
- Therefore, the correct answer to the question is that the deficiency of mobile elements first appears in the older leaves.

### Final Answer:
- The deficiency of mobile elements first appears on **older leaves**.

---