exchange of gases between air and the internal tissues of older corky stems takes place through

Options

A. Sive tube
B. Pits
C. Stomata
D. Lenticels

Answer

To answer the question regarding the exchange of gases between air and the internal tissues of older corky stems, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Corky Stems**: Older corky stems are characterized by their outer protective layer, which is formed by the cork cambium (also known as phallogen). This layer is essential for protecting the plant and preventing water loss.

2. **Role of Cork Cambium**: The cork cambium produces cork cells on the outside and phelloderm (parenchyma cells) on the inside. As the plant grows, these cork cells become thickened and dead, forming a protective barrier.

3. **Formation of Lenticels**: In older stems, the parenchymatous cells produced by the cork cambium can become compressed and eventually rupture. This rupture leads to the formation of small openings in the cork layer.

4. **Function of Lenticels**: These small openings are known as lenticels. They are lens-shaped structures that allow for gas exchange between the internal tissues of the stem and the external atmosphere.

5. **Conclusion**: Therefore, the exchange of gases in older corky stems occurs through lenticels.

### Final Answer:
The exchange of gases between air and the internal tissues of older corky stems takes place through **lenticels**.

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