Emerson effect he noticed that at wavelengths of greater than 680 nm the efficiency of photosynthesis decreased abruptly despite the fact that this is a region of the spectrum where chlorophyll still absorbs light (chlorophyll is the green pigment in plants - it absorbs mainly the red and blue wavelengths from light, leaving the green light to bounce back and hit our eyes). When the plants were exposed to short-wavelength light, (less than 660 nm), the efficiency also decreased. Emerson then exposed the plants to both short and long wavelengths at the same time, causing the efficiency to increase greatly. He concluded
Photosynthesis light, oxidize cytochrome f, chlorophyll a (and other pigments) will absorb another light, but will reduce this same oxidized cytochrome, stating the two light reactions are in series. In 1893, Charles Reid Barnes proposed two terms, "photosyntax" and "photosynthesis", for the biological process of "synthesis of complex carbon compounds out of carbonic acid, in the presence of chlorophyll, under the influence of light". Over time, the term "photosynthesis" came into common usage as the term of choice. Later discovery of anoxygenic photosynthetic bacteria and photophosphorylation necessitated redefinition of the term. After WWII at late 1940 at the University of California,