Effects of Light Quality on Growth and Physiological Characteristics of Neopyropia yezoensis Free Living Conchocelis

[Objectives] To study the differences of growth rate, morphology, ultrastructure, pigment content and antioxidant enzyme activity of free-living conchocelis of cultivated type of Neopyropia yezoensis under different light qualities (white, red light, blue, and green light). [Methods] The study was carried out through light quality design and culture, growth rate determination, microstructure and ultrastructure observation, chlorophyll a content and carotenoid content determination, phycobiliprotein content determination, malondialdehyde (MDA) content determination, superoxide dismutase (SOD) activity determination. [Results] After 21 d of culture, the specific growth rate (SGR) and chlorophyll a content of free-living conchocelis of N. yezoensis were significantly increased by white light (WL), followed by red light (RL) and green light (GL), and they were the lowest under blue light (BL). Compared with the WL group, the BL group had the highest content of phycoerythrin (PE), and the RL and GL groups had the highest content of phycocyanin (PC). The algal body of WL group was normal black brown, and the cell wall was the thickest. In RL and GL groups, the algal bodies were green, and their diameters and cell wall thicknesses were similar to those in WL group. In BL group, the algal body was bright red, the diameter was the smallest, the cell wall was the thinnest, and the ultrastructure showed that the number of plastoglobulus on the thylakoid was the largest. After BL irradiation, the highest malondialdehyde (MDA) content and the lowest superoxide dismutase (SOD) activity were observed. The results revealed that WL is the most beneficial to the growth of free-living conchocelis, followed by RL and GL, while BL has adverse effects. [Conclusions] This study explored the most suitable light quality conditions for the propagation of free-living conchocelis. It is expected to provide germplasm guarantee for the production and seedling of N. yezoensis.