Which is related to light reaction of photosynthesis

Options

A. In PS II light reaction centre is `P_(700)`
B. In PS I light reaction centre is `P_(680)`
C. Photolysis is associated with PS I
D. PS I and PS II are associated in Z-scheme

Answer

To answer the question "Which is related to light reaction of photosynthesis?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Light Reactions**: The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and require light to convert solar energy into chemical energy. This process involves two photosystems: Photosystem I (PSI) and Photosystem II (PSII).

2. **Identify the Photosystems**:
- **Photosystem II (PSII)**: The reaction center of PSII is known as P680, which absorbs light at a wavelength of 680 nm. This is where photolysis (the splitting of water molecules) occurs, producing oxygen.
- **Photosystem I (PSI)**: The reaction center of PSI is known as P700, which absorbs light at a wavelength of 700 nm.

3. **Evaluate the Options**:
- **Option 1**: "In PS II, light reaction center is P700" - This is incorrect because PSII has P680.
- **Option 2**: "In PS I, light reaction center is P680" - This is incorrect because PSI has P700.
- **Option 3**: "Photolysis is associated with PS I" - This is incorrect because photolysis occurs in PSII.
- **Option 4**: "PS I and PS II are associated in the Z-scheme" - This is correct. The Z-scheme describes the flow of electrons during the light reactions, involving both photosystems.

4. **Conclusion**: The correct answer is that the association of PS I and PS II in the Z-scheme is related to the light reactions of photosynthesis.

### Final Answer:
The option related to the light reaction of photosynthesis is **Option 4: PS I and PS II are associated in the Z-scheme**.

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