Stress Effects Of Nano Copper Oxide On Chlamydomonas Rein Hardtii

This study selected Chlamydomonas reinhardtii as the model organism to investigate the impacts of typical nano metals(nano copper oxide) on the growth of Chlamydomonas reinha rdtii, cell structure and photosynthesis. And then we analyzed the ecological toxicity effect of nano copper oxide on the Chlamydomonas reinhardtii to reveal its stress mechanism. Accordi ngly, the results provided theoretical basis to understand the toxic mechanism of nano metal o xide on aquatic organisms, as well as for the safe use of nanomaterials.Experimental results showed that the growth inhibition of Chlamydomonas reinhardtii e nhanced with the increase of concentration of nano copper oxide,and the 96 h EC50 of nano copper oxide on Chlamydomonas reinhardtii was 306.54 mg/L. The Logistic growth dynamic s model fitting results also illustrated that the termination biomass(Bf) and the maximum grow th rate(?max) both gradually decreased with the increase of concentration of nano copper oxid e. In addition, the higher the concentrations of nano copper oxide were, the greater the damag es to Chlamydomonas reinhardtii cell membrane permeability. Morever, the photosynthetic pi gment amounts in single cell also gradually reduced with the concentration of nano copper oxi de increased.Therefore, nano copper oxide had significant stress effects to Chlamydomonas r einhardtii.Furthermore, this study also investigated the stress mechanisms of nano copper oxide to t he Chlamydomonas reinhardtii, which included the mechanism of oxidative stress,free ion re lease mechanism and inhibition of photosynthesis mechanism. The experimental results indic ated:(1) Nano copper oxide released little Cu2+, but the released Cu2+ had influence on the gro wth rate of Chlamydomonas reinhardtii and had significant toxic effects. And furthermore, th e toxicity of Cu2+ enhanced with the increase of Cu2+ concentration. Based on the above analy sis, the Cu2+ released from nano copper oxide may be one of stress mechanisms of nano coppe r oxide to the Chlamydomonas reinhardtii.(2) When the concentration of nano copper oxide incresaed, SOD and POD amounts in C hlamydomonas reinhardtii intracellular both gradually increased, Morever, the activity of CA T and MDA amount first increased and then decreased with the increase of nano copper oxideconcentration. The analysis proved that oxidative stress was also the stress mechanisms of na no copper oxide to the Chlamydomonas reinhardtii.(3) Because of the aggregation performance of nano copper oxide, it was prone to coagul ate and precipitate with Chlamydomonas reinhardtii, which caused camouflage effects to the i ntracellular chloroplast adsorbing light. When the concentration of nano copper oxide increas ed, Chlamydomonas reinhardtii fluid light transmission and absorption efficiency both lowere d. which caused the photosynthetic pigment amounts lessen, abated the depleting ability, and enhanced the inhibition effect for photosynthesis. As a consequently, the inhibition of photosy nthesis might be the stress mechanism.