| Abstract: | The effect of light quantity (irradiance) on the photosynthetic physiology of seven seaweed species was distinguished from the effect of light quality (color). Plants were grown in outdoor, continuous-flow tanks, at irradiances saturating and limiting to growth, and in spectral distributions that were either broadband (white) or narrowband (green). The green light field complemented the absorptance spectrum of phycoerythrin and approximated the spectral distribution of a submarine light field in turbid coastal water near the compensation depth. Physiological measurements, made after 6–15 days growth, included light-harvesting pigment densities, instantaneous photosynthesis-light relationships and growth rate. In all experiments, these photosynthetic properties were independent of spectral distribution (color) and in most experiments were dependent on irradiance. These data do not conform to the predictions of the theory of complementary chromatic adaptation for seaweeds. |
