In plants the exchange of gases occur across the surface of :

Options

A. Stem
B. Root
C. Leaves
D. All of these.

Answer

**Step-by-Step Solution:**

1. **Understanding Gas Exchange in Plants**:
- In plants, gas exchange is essential for processes like photosynthesis and respiration. The primary gases exchanged are oxygen and carbon dioxide.

2. **Identifying Plant Structures Involved in Gas Exchange**:
- Gas exchange occurs mainly through specific structures in different parts of the plant:
- **Leaves**: The leaves contain tiny openings called stomata, which allow for the exchange of gases.
- **Stems**: Young stems also have stomata for gas exchange. As stems age, they develop structures called lenticels, which serve a similar function.
- **Roots**: While roots do not have stomata or lenticels, they can exchange gases through root hairs, which are extensions of root cells that increase surface area.

3. **Conclusion**:
- Since gas exchange occurs in the leaves (via stomata), young stems (via stomata), older stems (via lenticels), and roots (via root hairs), the correct answer to the question is that gas exchange occurs across the surface of all these parts.

4. **Final Answer**:
- Therefore, the correct option is "all of these" (stems, roots, leaves).

---