Differential Physiological Response of Pyropia haitanensis Conchocelis to Nitrate and Ammonium

The effects of different nitrogen sources (nitrate, nitrate-ammonium, and ammonium) and concentrations (1 and 5mg L-1) on Pyropia haitanensis conchocelis were investigated. Ammonium as nitrogen source yielded higher growth rates, chlorophyll a, carotenoid, phycoerythrin, phycocyanin, and elemental nitrogen content of P. haitanensis than with nitrate. 5 mg L-1 nitrogen resulted in increase of elemental nitrogen content, decrease of growth rates and triglycerides content with all nitrogen sources. The expression of glutamine synthetase 1 and glutamine synthetase 2 genes were higher with nitrate as nitrogen source than with ammonium, while expression of glutamate synthase gene was higher with ammonium as nitrogen source than with nitrate. Higher total contents of monogalactosyldiacylglycerols, digalactosyldiacylglycerols, sulfoquinovosyldiacylglycerols, and phosphatidylethanolamines of P. haitanensis were found at 5 mg L-1 than at 1 mg L-1 nitrogen with nitrate as nitrogen source. However, the total content of lipids (except phosphatidic acids) of P. haitanensis was less at 5 mg L-1 than at 1 mg L-1 nitrogen with ammonium as nitrogen source. In summary, the study indicated that ammonium was a favorable nitrogen source to P. haitanensis, as it promoted the growth rates and pigments content. 5 mg L-1 nitrogen with nitrate as nitrogen source was benefit for lipids production.