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EFFECTS OF SALT STRESS ON GROWTH AND PHOTOSYNTHESIS OF PYROPIA HAITANENSIS(RHODOPHYTA) CULTURED UNDER DIFFERENT NITROGEN CONDITONS
Author(s): 
Pages: 1210-1217
Year: Issue:  5
Journal: Oceanologia et Limnologia Sinica

Keyword:  Pyropia haitanensissalt stressnitrogenphotosynthesisrapid light response curve;
Abstract: To investigate the coupling effects of nitrogen enrichment and salt stress on growth and photosynthesis in Pyropia haitanensis, thalli were cultured under different nitrogen concentrations(500 and 50μmol/L) at 3 salinity levels(15, 30, and 45) for 7 days. The growth rate, pigment content, photosynthetic O2 evolution rate, and rapid light response curve were determined. The results show that at low nitrogen(50μmol/L) level, relative growth rate(RGR) decreased with salinity increase, while at high nitrogen(500μmol/L) level, the maximal RGR occurred at salinity of 30. Under the low nitrogen concentration(50μmol/L), contents of chlorophyll a(Chl a), carotenoid(Car), phycoerythrin(PE), and phycocyanin(PC) were higher at salinity 15 than at 30 and 45, and the difference was found insignificant between the last two salinity treatments. Under high nitrogen condition(500μmol/L), salinity had no effect on contents of Chl a and Car. However, both salt stresses at 15 and 45 reduced evidently the contents of PE and PC with no difference. Both nitrogen and salinity had negligible impacts on photosynthetic O2 evolution rate of algae, except that a lower rate per unit fresh weight was found in salinity 30 and a higher value per unit Chl a in salinity 45 under high nitrogen condition. The rapid light response curve shows that light saturation point(Ik), electron transfer efficiency(α), and the maximum rate of electron transfer(r ETRmax) were not affected by salt stress, but salinity at 45 remarkably enhanced light inhibition value of algae. In conclusion, high salinity could inhibit the growth and photosynthesis of P. haitanensis regardless of available nitrogen, while low salinity showed no inhibition on the growth and photosynthesis but promoted the growth rate at low nitrogen level. These results may provide a theoretical reference for P. haitanensis cultivation and eutrophication remediation.
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