What conclusion was drawn from red drop and enhanement experiments in the light reaction of photosynthesis

Options

A. Two photosystems are present
B. One photosystem is present
C. Two photosystems are present which work at different wavelengths
D. Two photosystems are present which work at some wavelength.

Answer

### Step-by-Step Solution:

1. **Understanding the Red Drop Phenomenon**:
- The red drop refers to the observation that the rate of photosynthesis decreases when light wavelengths beyond 680 nm (in the red region) are used. This indicates that photosynthesis is less efficient at these longer wavelengths compared to the red light.

2. **Understanding the Enhancement Effect**:
- The enhancement effect is observed when light of 700 nm is used in conjunction with light of shorter wavelengths. This leads to an increase in the rate of photosynthesis, suggesting that there are different responses to different wavelengths of light.

3. **Conclusion from Experiments**:
- Both the red drop and enhancement experiments suggest that there are two distinct photosystems involved in the light reactions of photosynthesis.
- Photosystem I (PSI) is more effective at absorbing light at wavelengths around 700 nm, while Photosystem II (PSII) is more effective at wavelengths around 680 nm.

4. **Final Conclusion**:
- The conclusion drawn from these experiments is that there are **two photosystems present in the light reactions of photosynthesis**, which operate at different wavelengths. This supports the idea that photosynthesis involves a complex interaction between these two systems to maximize light absorption and energy conversion.