Pigment acting as a reaction centre during photosynthesis is

Options

A. carotene
B. phytochrome
C. `P_(700)`
D. cytochrome

Explanation

To answer the question about which pigment acts as a reaction center during photosynthesis, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Photosynthesis**: Photosynthesis occurs in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). The light-dependent reactions take place in the thylakoid membranes of chloroplasts and involve the absorption of light energy.

2. **Identify the Reaction Centers**: In the light-dependent reactions, there are two primary reaction centers known as Photosystem II (PSII) and Photosystem I (PSI).
- PSII has a reaction center called P680, which absorbs light and initiates the process of electron transport.
- PSI has a reaction center called P700, which also absorbs light and helps in the production of NADPH.

3. **Analyze the Options**: The options provided are:
- A) Carotene
- B) Phytochrome
- C) P700
- D) Cytochrome

4. **Evaluate Each Option**:
- **Carotene**: This is a pigment that assists in capturing light but does not act as a reaction center.
- **Phytochrome**: This pigment is involved in regulating plant responses to light but is not a reaction center in photosynthesis.
- **P700**: This is the reaction center of Photosystem I and is crucial for the light-dependent reactions.
- **Cytochrome**: This is part of the electron transport chain but is not a reaction center.

5. **Select the Correct Answer**: Based on the analysis, the pigment that acts as a reaction center during photosynthesis is **P700**.

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