The carotenoid pigment zeaxanthin is concentrated in the center of the retina in our eyes, in the orange-colored macula. The pigment comes from the leafy green plants we eat and it helps protect our eyes from light radiation. Zeaxanthin also helps protect plants from the sun and is naturally increased when environmental conditions are harsh. However, for the purpose of human food supply, harsh conditions limit biomass or yield. Under ideal conditions, crops grow abundantly but do not contain as much protective pigment. An undergraduate researcher found that several 5-minute bursts of intense light over a background of optimal light elevated zeaxanthin
production without limiting biomass.
University of Colorado, Boulder Newsletter, March 4, 2014 and Acta Astronautica 94(2):799–806.