Photosynthetic characteristics of planktonic blue-green algae: Changes in photosynthetic capacity and pigmentation of oscillatoria redekei van goor under high and low light

Abstract

The photosynthetic characteristics and pigment contents of Oscillatoria redekei van Goor were measured under a range of photoperiods (6:18 light-dark to continuous light) and irradiances (13-260 µE m-2 s-1) at 15°C. The light saturated rate of photosynthesis (Pmax) per cell protein was found to be comparatively constant under different light regimes but cells grown under low irradiances and/or short light-dark (LD) cycles showed marked increases in the efficiency with which they harvested low light. The increase in efficiency under low light doses corresponded to an increase in the phycocyanin and chlorophyll a content of the cultures but phycocyanin content was observed to increase by a greater proportion than chlorophyll a. The increase in the ratio of phycocyanin to chlorophyll a was highly correlated with increases in the efficiency of light harvesting. Cells grown under 6:18 LD cycles had a pigment composition similar to low light cultures grown under continuous light. Because of wide differences in the pigment content of continuous light cultures, the light saturation characteristic /k varied over a wide range from 77 to 462 µE m-2 s-1, compared to a range of 78-140 µE m"2 s“1 for cells grown under a 6:18 LD cycle. In addition, the range of compensation irradiances for continuous light cells was 4-82 µEm_2s_1 compared to 3-6 µE m-2 s_1 for 6:18 LD cells. The large difference between continuous light and LD cells was due in part to the high respiration rates of continuous light cells. © 1982 Taylor & Francis Group, LLC.