Photosynthetic efficiency is represented by
`X/("Incident total solar radiation.")`
The X ' in this equation represents

Options

A. Gross primary productivity
B. Net primary productivity
C. Secondary productivity
D. None of these

Answer

To solve the question regarding the representation of photosynthetic efficiency, we need to identify what 'X' stands for in the equation given as:

\[ \text{Photosynthetic Efficiency} = \frac{X}{\text{Incident Total Solar Radiation}} \]

### Step-by-Step Solution:

1. **Understanding Photosynthetic Efficiency**:
- Photosynthetic efficiency refers to the effectiveness of plants in converting solar energy into chemical energy through the process of photosynthesis.

2. **Identifying 'X'**:
- In the context of photosynthesis, 'X' represents the total amount of energy captured by plants during photosynthesis, which is often quantified as productivity.

3. **Types of Productivity**:
- **Gross Primary Productivity (GPP)**: This is the total amount of energy captured by photosynthesis before any is used by the plants themselves.
- **Net Primary Productivity (NPP)**: This is the amount of energy that remains after the plants have used some for their own respiration. It is always less than GPP.
- **Secondary Productivity**: This refers to the energy that is transferred to the next trophic level, which is not directly related to photosynthesis.

4. **Conclusion**:
- Since photosynthetic efficiency is concerned with the total energy captured by photosynthesis, 'X' in the equation is best represented by **Gross Primary Productivity (GPP)**. Therefore, the correct answer is:
\[ \text{X} = \text{Gross Primary Productivity} \]

### Final Answer:
- The 'X' in the equation represents **Gross Primary Productivity**.

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