title: Ultrastructural changes, zinc hyperaccumulation and its relation with antioxidants in two ecotypes of Sedum alfredii Hance.
abstract: Zn phytotoxicity and its possible detoxifying responses in two ecotypes of Sedum alfredii Hance, i.e. hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) were investigated. HE grew better with high Zn concentrations of 29.11gkg(-1) DW in shoots when exposed to 500microM Zn2+. Toxicity symptoms caused by Zn in root cells of both ecotypes mainly included plasmolysis, disruption of plasma membranes and increased cell vacuolation. At high supplied Zn concentration, chloroplasts suffered from structural disorganization in both ecotypes. Zn-induced hydrogen peroxide (H2O2) and superoxide radical (O(2)-) productions in leaves were determined by a histochemical method, which revealed that Zn stress may have involved NADPH oxidase, protein phosphatases and intracellular Ca2+ to activate the reactive oxygen species production. Inhibition of glutathione synthesis may have led to increased H2O2 and O(2)- accumulations in leaves of HE. In response to higher Zn concentrations, ascorbic acid significantly increased in both ecotypes and levels of glutathione increased in both leaves and roots of HE and in roots of NHE without any change in the leaves of NHE. The enzymatic activities like those of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.6.4.2) in leaves of HE were all enhanced at supplied Zn concentration of 500microM, which may account for its better growth.
authors.affiliation: Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, PR China.
authors.forename: Xiao Fen
authors.initials: XF
authors.lastname: Jin
authors.forename: Xiao E
authors.initials: XE
authors.lastname: Yang
authors.forename: Ejazul
authors.initials: E
authors.lastname: Islam
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.forename: Qaisar
authors.initials: Q
authors.lastname: Mahmood
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Junying
authors.initials: J
authors.lastname: Li
mesh_terms: D000975:Antioxidants; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation; D046529:Microscopy, Electron, Transmission; D018384:Oxidative Stress; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D031963:Sedum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015032:Zinc / Q000378:metabolism / Q000633:toxicity*
chemical_list: D000975:Antioxidants; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D015032:Zinc