`Q_(10)` of light reaction is

Options

A. temperature coefficient
B. water coefficient
C. respiratory coefficient
D. none

Answer

### Step-by-Step Solution:

1. **Understanding Q10**:
- Q10 is a coefficient that indicates how the rate of a biological process changes with temperature. Specifically, it measures the rate of reaction for every 10 degrees Celsius increase in temperature.

2. **Application to Photosynthesis**:
- In the context of photosynthesis, Q10 reflects how the rate of photosynthesis (or light reactions, in this case) changes as the temperature increases.

3. **Value of Q10**:
- The value of Q10 for photosynthesis is typically around 2. This means that for every 10 degrees Celsius increase in temperature, the rate of photosynthesis doubles.

4. **Conclusion**:
- Therefore, when asked about Q10 in the light reaction, it is referred to as the temperature coefficient, which quantifies the change in the rate of the light reaction with temperature changes.

5. **Final Answer**:
- The Q10 of the light reaction is the temperature coefficient, which is approximately 2.