Photoperiod stimulus is perceived by___pigment.

Options

A. cryptochrome
B. cytochrome
C. phytochrome
D. monochrome

Explanation

To answer the question "Photoperiod stimulus is perceived by___pigment," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Photoperiodism**:
- Photoperiodism refers to the physiological reaction of organisms to the length of day or night. It plays a crucial role in the flowering of plants.

2. **Identify the Pigments Involved**:
- There are several pigments in plants, but the key ones related to light perception include Cryptochrome, Cytochrome, Phytochrome, and Monochrome.

3. **Focus on Phytochrome**:
- Phytochrome is the pigment known to be involved in the photoperiodic response. It helps plants detect the duration of light and dark periods.

4. **Recognize the Role of Phytochrome**:
- Phytochrome is responsible for initiating the flowering response in plants. It is particularly sensitive to red and far-red light wavelengths.

5. **Conclusion**:
- Based on the understanding of photoperiodism and the role of phytochrome, we conclude that the correct answer to the question is "Phytochrome."

### Final Answer:
Photoperiod stimulus is perceived by **Phytochrome**.

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