Topic: Light reactions, cyclic and non-cyclic photophosphorylation, chemiosmosis· Plant Physiology

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

1. Photophosphorylation and non-cyclic electron transport

2. Two photosystems operating simultaneously

3. Photophosphorylation and cyclic electron transport

4. Oxidative phosphorylation

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Answer: 2. Two photosystems operating simultaneously

Key idea: Red drop and Emerson's enhancement effect showed that two light reactions work together.

Quantum yield falls sharply in far-red light (beyond about 680 nm), the red drop. Emerson found that adding shorter-wavelength red light restored it, and the combined effect was greater than the sum of each alone. This led to the discovery of two photosystems (PS I and PS II) operating together. Option (2).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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

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