Compensation point means

Options

A. No photosynthesis .
B. Beginning of photosynthesis.
C. Equal rate of photosynthesis and respiration .
D. Excess of respiration ti compensate `O_2` production.

Answer

To solve the question "Compensation point means," we will analyze the options provided and understand the concept of the compensation point in the context of photosynthesis and respiration.

### Step-by-Step Solution:

1. **Understanding Photosynthesis and Respiration**:
- Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen.
- Respiration is the process by which organisms convert glucose and oxygen into energy, producing carbon dioxide and water.

2. **Defining the Compensation Point**:
- The compensation point is a specific point in the light intensity or other environmental conditions where the rate of photosynthesis equals the rate of respiration.

3. **Analyzing the Options**:
- **Option 1**: No photosynthesis - This is incorrect as the compensation point occurs during photosynthesis.
- **Option 2**: Beginning of photosynthesis - This is not accurate; the compensation point is not merely the start of photosynthesis.
- **Option 3**: Equal rate of photosynthesis and respiration - This is the correct definition of the compensation point.
- **Option 4**: Excess of respiration to compensate oxygen production - This is incorrect as it does not reflect the balance of processes at the compensation point.

4. **Conclusion**:
- The compensation point is where the rate of photosynthesis equals the rate of respiration, resulting in no net gain or loss of biomass. At this point, the net gaseous exchange is also zero.

### Final Answer:
The correct answer is **Option 3: Equal rate of photosynthesis and respiration**.

---