Explanation
The correct answer is D: Two Distinct Pigment Systems.
The Emerson effect is a phenomenon discovered by the American scientist Robert Emerson in 1957, which showed that photosynthesis is driven by two distinct pigment systems. Emerson observed that when a photosynthetic organism is exposed to light of a wavelength that can be absorbed by only one of the two photosystems, the rate of photosynthesis is only about half of what it is when the organism is exposed to light of a wavelength that can be absorbed by both photosystems.
This led Emerson to conclude that there are two distinct pigment systems involved in photosynthesis, which he named Photosystem I (PSI) and Photosystem II (PSII). PSI absorbs light at a wavelength of around 700 nm, while PSII absorbs light at a wavelength of around 680 nm. The two pigment systems work together to capture and convert light energy into chemical energy during photosynthesis.
The discovery of the Emerson effect provided strong evidence for the existence of two distinct pigment systems in photosynthesis and helped to advance our understanding of the mechanisms of photosynthesis. Light and dark reactions, photorespiration, and photophosphorylation are also important processes in photosynthesis, but they are not directly related to the Emerson effect.
