The ideal of two pigment systems in light reaction of photosynthesis was given by

Options

A. Arnon
B. Hill
C. Blackman
D. None of the above.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the scientist who proposed the idea of two pigment systems involved in the light reactions of photosynthesis.

2. **Identifying Key Concepts**: The concept of two pigment systems relates to the absorption of light by different pigments in plants. Specifically, it involves the absorption of red light and far-red light.

3. **Red Drop Effect**: The red drop effect is a phenomenon where there is a significant decline in photosynthetic efficiency when light wavelengths exceed 700 nm. This indicates that pigments become inactive at these wavelengths.

4. **Historical Context**: The red drop effect was first observed by Robert Emerson. He conducted experiments using chlorella plants and demonstrated that alternating red light and far-red light increased the quantum yield of photosynthesis.

5. **Immersion Enhancement Effect**: Emerson's findings led to the identification of two photosystems: one that absorbs red light (around 660 nm) and another that absorbs far-red light (above 700 nm). This phenomenon is known as the Immersion Enhancement Effect.

6. **Evaluating the Options**:
- Arnold: Incorrect, as he did not propose the two pigment systems.
- Hill: Incorrect, as he focused on other aspects of photosynthesis.
- Blackman: Incorrect, as he studied limiting factors in photosynthesis.
- None of the above: Correct, as the idea of two pigment systems was proposed by Robert Emerson.

7. **Conclusion**: The correct answer to the question is "none of the above" since the concept was introduced by Robert Emerson.

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