In plants opening of stomata is regulated by

Options

A. Red light
B. Blue light
C. Far-red light
D. Ultraviolet light .

Answer

**Step-by-Step Solution:**

1. **Understanding Stomata**: Stomata are small openings on the surfaces of leaves that allow for gas exchange, primarily the intake of carbon dioxide and the release of oxygen. The opening and closing of stomata are crucial for photosynthesis and transpiration in plants.

2. **Role of Light in Stomatal Opening**: The opening of stomata is influenced by different wavelengths of light. Among these, blue light plays a significant role.

3. **Direct Influence of Blue Light**: Blue light acts as a direct signal for stomatal opening. When plants are exposed to blue light, it stimulates the guard cells surrounding the stomata to absorb water, causing them to swell and the stomata to open.

4. **Indirect Influence of Red Light**: While red light also contributes to stomatal opening, it does so indirectly. Red light enhances the process of photosynthesis, which increases the demand for carbon dioxide. As the plant requires more carbon dioxide for photosynthesis, the stomata open to allow more gas exchange.

5. **Other Light Types**: Far red light and ultraviolet (UV) light do not have a significant impact on the opening of stomata. Therefore, they can be ruled out as influencing factors.

6. **Conclusion**: Based on the above points, the correct answer to the question "In plants, the opening of stomata is regulated by" is blue light.

**Final Answer**: Blue light.

---