According to the chemiosmotic hypothesis of ATP formation in the chloroplast, which one does not contribute to the development of proton gradient across the thylakoid membrane?

Options

A. Splitting of water
B. Reduction of `NADP^(+)` to `NADPH + H^(+)`
C. Reduction of `NAD^(+)` to `NADPH + H^(+)`
D. Removal of `H^(+)` from stroma while transporting electron

Answer

To solve the question regarding the chemiosmotic hypothesis of ATP formation in chloroplasts and identify which option does not contribute to the development of the proton gradient across the thylakoid membrane, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Chemiosmotic Hypothesis**:
- The chemiosmotic hypothesis explains how ATP is synthesized in chloroplasts based on the establishment of a proton gradient across the thylakoid membrane. This gradient is essential for ATP synthesis.

2. **Identify the Role of Each Process**:
- **Splitting of Water**: This process occurs during photosynthesis where water (H2O) is split into oxygen (O2), protons (H+), and electrons. The protons contribute to the accumulation of H+ ions in the thylakoid lumen, thus contributing to the proton gradient.
- **Reduction of NAD+ to NADPH and H+**: This process involves the conversion of NADP+ to NADPH, which also produces protons (H+). However, it is important to note that this reduction does not directly contribute to the proton gradient across the thylakoid membrane.
- **Removal of H+ from the Stroma**: During the electron transport chain, H+ ions are removed from the stroma, contributing to the proton gradient as they accumulate in the thylakoid lumen.

3. **Evaluate Each Option**:
- **Option 1: Splitting of Water** - Contributes to the proton gradient.
- **Option 2: Reduction of NAD+ to NADPH and H+** - This option is misleading as it mentions NAD+ instead of NADP+, and it does not contribute to the proton gradient.
- **Option 3: Reduction of NADP+ to NADPH and H+** - This is a correct process but does not contribute to the proton gradient.
- **Option 4: Removal of H+ from the Stroma** - Contributes to the proton gradient.

4. **Conclusion**:
- The option that does not contribute to the development of the proton gradient across the thylakoid membrane is the **reduction of NAD+ to NADPH and H+** (Option 2).

### Final Answer:
The correct answer is **Option 2: Reduction of NAD+ to NADPH and H+**.