Which of the following statements regarding cycle flow of electrons during light reactions is false?

Options

A. This process takes place in the stromal lamella
B. ATP synthesis takes place
C. NADPH+`H^+` is synthesised
D. Takes place only when light of wavelength beyond 680 nm is available for excitation.

Answer

To determine which statement regarding the cyclic flow of electrons during light reactions is false, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Cyclic Photophosphorylation**:
- Cyclic photophosphorylation is a process that occurs in photosystem I of the chloroplasts, where electrons are excited by light and then return to the same photosystem after passing through an electron transport chain.

2. **Analyzing the Statements**:
- **Statement 1**: "This process takes place in stromal amyla."
- This statement is misleading. Cyclic photophosphorylation occurs in the thylakoid membranes of the chloroplasts, not in stromal amyla. Therefore, this statement could be considered false.

- **Statement 2**: "ATP synthesis takes place."
- This statement is true. ATP is indeed synthesized during cyclic photophosphorylation as the electrons move through the electron transport chain.

- **Statement 3**: "NADPH and hydrogen ions synthesis takes place."
- This statement is false in the context of cyclic photophosphorylation. In this process, NADPH is not produced; instead, only ATP is generated. NADPH synthesis occurs in non-cyclic photophosphorylation.

- **Statement 4**: "It takes place only when light of wavelength beyond 680 nm is available for excitation."
- This statement is true. Photosystem I is activated by light of wavelengths longer than 680 nm.

3. **Conclusion**:
- The false statement regarding the cyclic flow of electrons during light reactions is: "NADPH and hydrogen ions synthesis takes place."

### Final Answer:
The false statement is: "NADPH and hydrogen ions synthesis takes place."

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