Pigment acting as a reaction centre during photosynthesis is

Options

A. Carotene
B. Phytochrome
C. `P_(700)`
D. Cytochrome.

Answer

To determine the pigment acting as a reaction center during photosynthesis, we need to analyze the options provided and understand the role of different pigments in the process of photosynthesis.

### Step-by-Step Solution:

1. **Understanding Photosystems**: Photosynthesis occurs in two main photosystems: Photosystem I (PS1) and Photosystem II (PS2). Each of these systems has a specific pigment that acts as the reaction center.

2. **Identifying the Reaction Centers**:
- **Photosystem I (PS1)**: The reaction center of PS1 is known as P700, which has an absorption peak at 700 nanometers.
- **Photosystem II (PS2)**: The reaction center of PS2 is known as P680, which has an absorption peak at 680 nanometers.

3. **Analyzing the Options**:
- **Carotene**: This is an accessory pigment but not the primary reaction center.
- **Phytochrome**: This pigment is involved in plant responses to light but is not the reaction center for photosynthesis.
- **P700**: This is the correct answer as it refers to the reaction center of Photosystem I.
- **Cytochrome**: This is a protein involved in the electron transport chain, not a reaction center.

4. **Conclusion**: Based on the analysis, the pigment acting as the reaction center during photosynthesis is **P700**.

### Final Answer:
The pigment acting as a reaction center during photosynthesis is **P700** (Option 3).

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