Effects on Cell Growth and Polysaccharide Production in Differ-ent Morphologic Cells of Phaeocystis globosa Under N or P Limitation
In order to explore the effects of nutrients stress on cell growth and polysaccharide production of Phaeocystis globosa with different ploidy in Beibu Gulf of Guangxi,a single factor control experiment was used to set 3 nitrogen and phosphorus limitation ratios of 4.0∶1.0,24.5∶1.0 and 64.0∶1.0 in this study.The haploid and diploid cells of P.globosa were cultured in artificial seawater to compare the growth changes of the two cells and the differences of polysaccharides content and Transparent Exopolymer Particles(TEP)release in each growth period.The results showed that the promoting effect of nitrogen and phosphorus nutri-tion on the early growth of diploid cells was stronger than that of haploid cells,and the growth rate of diploid cells was significantly higher than that of haploid cells(P＜0.05).The Soluble Exopolysaccharide(sEPS)were main polysaccharides secreted by P.globosa cells,followed by Intracellular Polysaccharide(IPS),and Bound Exopolysaccharide(bEPS)accounted for the lowest proportion of total sugars.The secretion of bEPS in haploid cells and diploid cells showed the opposite trend.There were no significant differences in Extracel-lular Polysaccharide(EPS),IPS and TEP yields of haploid single cells in nitrogen and phosphorus limitation groups(P＞0.05).The production of EPS,IPS and TEP in diploid single cells of the phosphorus-limited group was significantly higher than that of the control group and the nitrogen-limited group(P＜0.05).In summary,nutrient stress stimulated the production of EPS and TEP in P.globosa,and the production of TEP in P.globosa was affected by the relative stock of nutrients.The response of diploid cell polysaccharides and TEP to phosphorus limitation was more sensitive than that of haploid cells.
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