The Influence of Light Exposure on the Photosynthetic Carbon Utilization of Undaria pinnatifida (Phaeophyceae)

Abstract

The inorganic carbon assimilation mechanisms of photosynthesis were investigated in male gametophytes, female gametophytes and juvenile sporophytes of Undaria pinnatifida after blue light and red light exposure. pH compensation points of the three types with blue light exposure were 8.93, 8.91 and 9.71 respectively. With red light exposure, pH compensation points were lower at 8.70, 8.67 and 8.77. Blue light might promote the accumulation of intracellular HCO–3 or CO2 and supplement the photosynthetic absorption of inorganic carbon. However, this benefit was weakened by the presence of high concentration inorganic carbon. The affinity of photosynthesis for inorganic carbon with blue light exposure was higher than that with red light. U. pinnatifida might primarily rely on CO2(aq) as carbon source in red light.