"Second Emerson Effect" in the Hill Reaction of Chlorella Cells with Quinone as Oxidant.

The second Emerson effect can be observed not only in photosynthesis but also in the photoreduction of quinone by Chlorella cells. This shows that this effect is not due to respiration and is not associated with the carbon dioxide-reducing phase of photosynthesis. Peaks at 650 and 670 mmicro in the action spectra of this effect, in the case of quinone reductions as well as in that of photosynthesis in Chlorella, show that light absorbed by chlorophyll b as well as that absorbed by chlorophyll a 670 can effectively supplement far-red light (> 680 mmicro) in both reactions; light absorbed by chlorophyll a 680 cannot do so.