Effect of light quality on growth, ultrastructure, pigments, and membrane lipids of Pyropia haitanensis

Light quality is an important factor on regulating growth and development of algae. Two trials were conducted to evaluate the effect of light quality on filmentous conchocelis (sporophyte in the heteromorphic life cycle) of Pyropia haitanensis. Trial I studied the effect of white, blue, and green light on growth rate, ultrastructure, pigments, and the membrane lipids of P. haitanensis. In trial II, the effect of white, blue, and green light was evaluated on the formation of P. haitanensis conchosporangia. In trial I, growth rate decreased 28.54% under blue light compared with white light, and no difference was observed under green and white light. Compared with white light, chlorophyll a and carotenoid reduced under blue (23.95%, 22.76%) and green (41.21%, 37.90%), and phycoerythrin and phycocyanin under green decreased 53.56% and 45.64%. The content of membrane lipids significantly decreased under blue (81.15%) and green (85.63%), and the ratio of unsaturated to saturated fatty acids decreased under blue and green. The cell wall under green light was thicker (0.153 ± 0.014 μm) than blue (0.117 ± 0.010 μm) and white light (0.121 ± 0.011 μm). Larger size of plastoglobuli exhibited under green (3.23 × 10−4 ± 1.95 × 10−4 μm3) than under white (3.97 × 10−5 ± 1.70 × 10−5 μm3) and blue light (1.41 × 10−4 ± 7.91 × 10−5 μm3). Starch granules occurred only under green light. In trial II, blue light enhanced conchosporangial branch formation, while green light inhibited conchosporangial branch formation compared with white light. Taken together, these findings indicated that light quality effected growth, ultrastructure, pigments, and lipids of P. haitanensis.