Best defined function of manganese in green plants is

Options

A. photolysis of water
B. Calvin cycle
C. Nitrogen fixation
D. water absorption.

Explanation

### Step-by-Step Solution:

1. **Identify the Element**: The question asks about the function of manganese in green plants. Manganese is an essential mineral nutrient for plants.

2. **Understand the Role of Manganese**: Manganese plays a crucial role in various physiological processes in plants, particularly in photosynthesis and respiration.

3. **Focus on Photosynthesis**: Among its functions, manganese is particularly important in the process of photosynthesis. It is involved in the photolysis of water, which is a key step in this process.

4. **Explain Photolysis of Water**: During photosynthesis, manganese aids in the splitting of water molecules (H2O) to release oxygen (O2). This process is known as photolysis, where "lysis" refers to the breaking or splitting of molecules.

5. **Conclude the Main Function**: Therefore, the best-defined function of manganese in green plants is the photolysis of water, which is essential for the production of oxygen during photosynthesis.

### Final Answer:
The best defined function of manganese in green plants is the photolysis of water.

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