Cyclic flow of electrons in photophosphorylation in plant involves

Options

A. PS-I only
B. PS-II only
C. both PS-I and PS-II
D. ATP -ase

Answer

**Step-by-Step Solution:**

1. **Understanding Photophosphorylation:**
- Photophosphorylation is the process of synthesizing ATP from ADP and inorganic phosphate using light energy.
- It occurs in two forms: cyclic and non-cyclic photophosphorylation.

2. **Identifying the Cyclic Flow of Electrons:**
- In cyclic photophosphorylation, only Photosystem I (PSI) is involved.
- The electrons excited by light energy in PSI are not transferred to NADP+ but are cycled back to PSI through the electron transport chain.

3. **Role of Photosystem I:**
- The reaction center of Photosystem I is known as P700, which has an absorption peak at 700 nm.
- The cyclic flow of electrons leads to the synthesis of ATP but does not produce NADPH.

4. **Conclusion:**
- Since cyclic photophosphorylation involves only Photosystem I, the correct answer to the question is "Photosystem I only."

**Final Answer:**
The cyclic flow of electrons in photophosphorylation in plants involves **Photosystem I only**.

---