The exchange of gases in old stems takes place from

Options

A. Stomata
B. hydatodes
C. Lenticels
D. Passage cells

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the mechanism of gas exchange in old stems of plants.

2. **Evaluating the Options**:
- **Option 1: Stomata**: Stomata are small openings primarily found on the leaves of plants. They facilitate gas exchange (like oxygen and carbon dioxide) but are not involved in gas exchange in old stems. Therefore, this option is incorrect.

- **Option 2: Hydathodes**: Hydathodes are specialized structures found on leaves that help in the process of guttation, which is the exudation of water droplets from the leaf margins. They are not involved in gas exchange in stems. Thus, this option is also incorrect.

- **Option 3: Lenticels**: Lenticels are small openings found in the bark of woody plants, especially in older stems. They consist of loosely arranged cells that allow for gas exchange between the internal tissues and the atmosphere. Since old stems have an impermeable bark, lenticels are crucial for allowing gases to enter and exit. This option is correct.

- **Option 4: Passage Cells**: Passage cells are specialized endodermal cells found in roots, not stems. They do not play a role in gas exchange in old stems. Therefore, this option is incorrect.

3. **Conclusion**: After evaluating all the options, the correct answer is that the exchange of gases in old stems takes place from **lenticels**.

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