Which photoreceptor controls the opening and closing of stomata?

Options

A. Chlorophyll a
B. Chlorophyll b
C. Phytochrome
D. Carotene

Answer

**Step-by-Step Solution:**

1. **Understanding Photoreceptors**: Photoreceptors are proteins in plants that detect light and regulate various physiological processes. They play a crucial role in how plants respond to light.

2. **Types of Photoreceptors**: There are two main types of photoreceptors in plants:
- **Phytochromes**: These are primarily involved in the response to red and far-red light and play a significant role in the opening and closing of stomata.
- **Blue Light Receptors**: These receptors respond to blue light and also influence various plant processes.

3. **Role of Phytochromes**: Phytochromes are specifically responsible for the regulation of stomatal movement. They help in the opening and closing of stomata in response to light conditions.

4. **Other Options**: The other options provided (chlorophyll A, chlorophyll B, and carotene) are primarily involved in the absorption of light for photosynthesis rather than directly controlling stomatal movement.
- **Chlorophyll A**: Functions as an electron donor in photosynthesis.
- **Chlorophyll B**: Absorbs higher frequencies of blue light and assists chlorophyll A.
- **Carotene**: Aids in light absorption for photosynthesis.

5. **Conclusion**: Since the question specifically asks for the photoreceptor that controls the opening and closing of stomata, the correct answer is **Phytochrome**.

**Final Answer**: The photoreceptor that controls the opening and closing of stomata is **Phytochrome**.

---