Which one of the following ions is essential for photolysis of water?

Options

A. Mangnaese
B. Zinc
C. Copper
D. Boron

Explanation

To determine which ion is essential for the photolysis of water, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Photolysis of Water**:
- Photolysis refers to the process of splitting water molecules into hydrogen ions (protons), electrons, and oxygen in the presence of light. This process occurs during photosynthesis, specifically in the light-dependent reactions.

2. **Identify the Role of Ions in Photolysis**:
- Various ions play different roles in photosynthesis. However, certain ions are specifically involved in the process of photolysis.

3. **Examine the Given Options**:
- The options provided are manganese, zinc, copper, and boron. We need to analyze which of these ions is crucial for the photolysis of water.

4. **Research the Function of Each Ion**:
- **Manganese (Mn)**: Manganese is known to be a critical component of the oxygen-evolving complex in photosystem II. It helps in the splitting of water molecules.
- **Zinc (Zn)**: Zinc plays a role in various enzymatic functions but is not directly involved in the photolysis of water.
- **Copper (Cu)**: Copper is involved in electron transport but is not essential for the photolysis of water.
- **Boron (B)**: Boron is important for plant growth and development but does not play a direct role in the photolysis of water.

5. **Conclusion**:
- Based on the analysis, manganese is the ion that is essential for the photolysis of water.

### Final Answer:
The ion essential for the photolysis of water is **manganese (Mn)**.