Emerson's enhancement effect and red drop have been instrumental in the discovery of

Options

A. Two photosystems operating simultaneously
B. Photophosphorylation and cyclic electron transport
C. Oxidative phosphorylation
D. Photophosphorylation & non-cyclic electron transport

Answer

To answer the question regarding Emerson's enhancement effect and the red drop, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understand the Concepts**:
- **Emerson's Enhancement Effect**: This effect refers to the phenomenon where the rate of photosynthesis increases when both red light (around 680 nm) and far-red light (around 700 nm) are used together compared to when only red light is used. This indicates the presence of two distinct photosystems in plants.
- **Red Drop Effect**: This effect describes the decrease in the rate of photosynthesis when only far-red light is used, which is less effective for photosynthesis compared to red light.

2. **Identify the Wavelengths**:
- Red light (680 nm) is absorbed by Photosystem II (PSII).
- Far-red light (700 nm) is absorbed by Photosystem I (PSI).
- The combination of these two wavelengths enhances the overall photosynthetic efficiency.

3. **Link the Effects to Discoveries**:
- The experiments conducted by Emerson demonstrated that both photosystems (PSI and PSII) operate simultaneously during photosynthesis.
- The enhancement effect showed that the presence of both wavelengths leads to a higher rate of photosynthesis than either wavelength alone.

4. **Conclude the Discovery**:
- Based on the understanding of the enhancement effect and the red drop, it can be concluded that these effects were instrumental in discovering that there are two photosystems operating simultaneously in plants.

5. **Select the Correct Option**:
- Among the given options, the correct answer is: "two photo systems operating simultaneously."

### Final Answer:
Emerson's enhancement effect and the red drop have been instrumental in the discovery of **two photo systems operating simultaneously**.

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