Question

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

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

Answer 1

The Correct Option is A

Emerson's Enhancement Effect and Red Drop Effect 

Emerson's Enhancement Effect and the Red Drop Effect are key phenomena that led to the discovery of the participation of two types of photosystems in the light reaction of photosynthesis.

1. Emerson's Enhancement Effect

In the 1950s, the American scientist Robert Emerson observed an interesting phenomenon called the Enhancement Effect during photosynthesis. When plants were exposed to light of two different wavelengths (red and far-red light) simultaneously, the rate of photosynthesis increased significantly compared to the rate observed when only red or far-red light was used individually. This enhancement suggested that two different wavelengths were involved in the photosynthesis process, pointing toward the presence of two distinct photosystems.

2. Red Drop Effect

The Red Drop Effect was observed by Emerson and his colleagues as a part of their investigation. When plants were exposed to red light alone, the rate of photosynthesis decreased at longer wavelengths, particularly in the red region of the light spectrum. This effect revealed that the efficiency of photosynthesis is not uniform across the entire visible light spectrum, and it showed a significant decrease beyond a certain red wavelength, further supporting the idea of two different types of photosystems.

3. Discovery of Two Photosystems

The two effects, the Enhancement Effect and the Red Drop Effect, led to the conclusion that there are two different photosystems in plants involved in the light-dependent reactions of photosynthesis:

• Photosystem I (PSI): This system absorbs light primarily in the far-red region and is involved in the production of NADPH.
• Photosystem II (PSII): This system absorbs light primarily in the red region and is involved in the splitting of water molecules to produce oxygen and generate ATP.

The two photosystems work together to efficiently harness light energy and convert it into chemical energy during the light reactions of photosynthesis. The discovery of these two distinct photosystems marked a significant advancement in our understanding of the photosynthetic process.