Which of the following is the characteristic of PS-I.

Options

A. it is active only upto 680 nm of light
B. the reaction centre of PS-I is `P_(680)`
C. PS-I is reduced by the electrons released in photolysis of water
D. PS-I in involved in non-cyclic photophos phorylation

Explanation

To solve the question regarding the characteristics of Photosystem I (PS-I), we will analyze each option provided and determine which one accurately describes PS-I.

### Step-by-Step Solution:

1. **Understanding Photosystem I (PS-I)**:
- PS-I is one of the two photosystems in the light-dependent reactions of photosynthesis. It plays a crucial role in converting light energy into chemical energy.

2. **Analyzing Option 1**: "It is active only up to 680 nm of light."
- This statement is incorrect. The reaction center of PS-I is known as P700, which absorbs light most efficiently at a wavelength of 700 nm, not 680 nm.

3. **Analyzing Option 2**: "The reaction center of PS-I is P680."
- This statement is also incorrect. The reaction center of PS-I is indeed P700, while P680 is the reaction center of Photosystem II (PS-II).

4. **Analyzing Option 3**: "PS-I is reduced by the electrons released in photolysis of water."
- This statement is incorrect as well. Photolysis of water occurs in PS-II, and the electrons released are used to replenish the electron deficit in PS-II, not PS-I.

5. **Analyzing Option 4**: "PS-I is involved in non-cyclic photophosphorylation."
- This statement is correct. PS-I participates in both cyclic and non-cyclic photophosphorylation, contributing to the production of ATP and NADPH.

6. **Conclusion**:
- The correct characteristic of PS-I is that it is involved in non-cyclic photophosphorylation.

### Final Answer:
The correct option is: **PS-I is involved in non-cyclic photophosphorylation.**

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