Emerson's Enhancement Effect

To follow up on the red-drop puzzle, Emerson modified his experiment by supplying two wavelengths of light together rather than one at a time: a shorter wavelength of red light (650 nm) supplied alongside a longer wavelength of far-red light (710 nm). He found that this combination did more than simply add the two individual effects together - it produced a photosynthetic yield substantially greater than the sum of the two wavelengths given separately, and it also recovered (reversed) the red-drop loss seen with far-red light alone. The actual measured rates make the effect concrete: photosynthetic rate at 710 nm (far red) alone was 10, at 650 nm (red) alone was 43.5, and with both wavelengths supplied together (650+710 nm) the rate reached 72.5 - substantially above the simple sum of 53.5 that would be expected if the two wavelengths were simply acting independently and additively. This synergistic boost in photosynthetic output from combining two wavelengths is called Emerson's Enhancement Effect, and it is regarde …