THE INTERACTION EFFECTS OF Cd~(2+) AND P CONCENTRATIONS ON THE GROWTH AND CHLOROPHYLL FLUORESCENCE CHARTERISTICS OF CHLORELLA SP. AND NANNOCHLORIS OCULATA

The interaction effects of different Cd2+ and P concentrations on the growth and chlorophyll fluorescence parameters(Fv/Fm,Fv/Fo,Yield and rETR) of Chlorella sp.and Nannochloris oculata(obtained from the Microalgae Culture Center(MACC),Ocean university of China) were investigated.The three-factor analysis of variance results indicated that Cd2+ concentrations,P concentrations,stress time and their interaction all had significant effects on the chlorophyll fluorescence parameters,relative chlorophyll content and cell density of Chlorella sp.and N.oculata(P0.05).The correlation results showed that the main fluorescence parameters(Fv/Fm,Fv/Fo,Yield and rETR) were negative correlations with Cd2+ concentrations in Chlorella sp.and N.oculata,both decreased with increasing Cd2+ concentrations.Further more,compared to the control and the high P concentration treatment,the parameters Fv/Fm,Fv/Fo,Yield and rETR,relative chlorophyll content and cell density of the 2 microalgal strains remarkably decreased in low P concentration(2.27μmol/L),which showed obvious phosphorus limitation.Otherwise,the above parameters reached their highest values at high P concentration(290.4μmol/L),which showed high P concentration could reduce toxicity under Cd2+ stress.