Oxidative stress induced by PbCl2 at concentrations range of 0.03–0.22 mM in Chlamydomonas reinhardtii. Data are presented as mean ± SEM. All the results are from at least three independent experiments. Statistical significance was calculated among all the samples and to the controls (P < 0.001). Where no error bars are evident, they are equal to or smaller than the values.