Chiral Selective Toxicity Of Hexabromocyclododecane To Plants

In this study,α-,β-,γ-hexabromocyclododecane（HBCD）was separated by high performance liquid chromatography to obtain three pairs of enantiomers of HBCD.The selective toxicity effects of HBCD enantiomers on maize and wheat were investigated by hydroponic experiments.The germinated maize or wheat seedlings were exposed to different concentrations(0.5、1.0、2.0、3.0 and 5.0μg·L^-1)of HBCDs.1)After exposure of differentα-HBCD enantiomers,early root development was more influenced by（+）α-HBCD.The slope of the dose-effect fitting line of plant growth was the highest in the（+）α-HBCD treatment.The chlorophyll content,superoxide dismutase（SOD）and catalase（CAT）activity,and the number ofγ-H2AX focus of the plant was induced d more significant by（+）α-HBCD,indicating that the toxicity of（+）α-HBCD to maize is more toxic.2)Under the exposure of differentβ-HBCD enantiomers,the effect of（+）β-HBCD on anthocyanin content,SOD and ascorbate peroxidase（APX）activity to maize was more significant.（+）β-HBCD induced the highest content of superoxide anion radicals in maize seedlings.Underβ-HBCD exposure,roots were damaged.Root activity was negatively correlated with exposure concentration,and the damage to roots is more serious in（+）β-HBCD treatment.3)Afterγ-HBCD exposure,the germination rate of maize and wheat seeds was inhibited,and there was a significant linear relationship between concentration and inhibition rate.The order of inhibition rate was（+）γ-HBCD>（rac）γ-HBCD and maize>wheat.The increase of ascorbate（ASA）,glutathione（GSH）and malondialdehyde（MDA）content wasmore significant and the damage to the roots membrane of maize was more serious after（+）γ-HBCD exposure.4)The MDA content,mitochondrial membrane potential changes and transmission electron microscopy analysis were measured after the HBCD isomers and enantiomers exposure.HBCD can increase the content of MDA and decrease the mitochondrial membrane potential of roots,HBCD can destroy the outer wall of the cell,and change the cell morphology and some organelles.And the order of toxicity isα-HBCD>β-HBCD>γ-HBCD,and the（+）-enantiomer is more toxic than the（-）-enantiomer.