title: Too much is bad--an appraisal of phytotoxicity of elevated plant-beneficial heavy metal ions.
abstract: Heavy metal ions such as cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) are considered essential/beneficial for optimal plant growth, development, and productivity. However, these ions readily impact functions of many enzymes and proteins, halt metabolism, and exhibit phytotoxicity at supra-optimum supply. Nevertheless, the concentrations of these heavy metal ions are increasing in agricultural soils worldwide via both natural and anthropogenic sources that need immediate attention. Considering recent breakthroughs on Co, Cu, Fe, Mn, Mo, Ni, and Zn in soil-plant system, the present paper: (a) overviews the status in soils and their uptake, transport, and significance in plants; (b) critically discusses their elevated level-mediated toxicity to both plant growth/development and cell/genome; (c) briefly cross talks on the significance of potential interactions between previous plant-beneficial heavy metal ions in plants; and (d) highlights so far unexplored aspects in the current context.
authors.affiliation: Centre for Environmental and Marine Studies (CESAM) and Department of Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal, anjum@ua.pt.
authors.forename: Naser A
authors.initials: NA
authors.lastname: Anjum
authors.forename: Harminder P
authors.initials: HP
authors.lastname: Singh
authors.forename: M Iqbal R
authors.initials: MI
authors.lastname: Khan
authors.forename: Asim
authors.initials: A
authors.lastname: Masood
authors.forename: Tasir S
authors.initials: TS
authors.lastname: Per
authors.forename: Asha
authors.initials: A
authors.lastname: Negi
authors.forename: Daizy R
authors.initials: DR
authors.lastname: Batish
authors.forename: Nafees A
authors.initials: NA
authors.lastname: Khan
authors.forename: Armando C
authors.initials: AC
authors.lastname: Duarte
authors.forename: Eduarda
authors.initials: E
authors.lastname: Pereira
authors.forename: Iqbal
authors.initials: I
authors.lastname: Ahmad
mesh_terms: D000075322:Heavy Metal Poisoning; D019216:Metals, Heavy / Q000032:analysis; D063245:Plant Development / Q000187:drug effects; D010944:Plants / Q000187:drug effects* / Q000378:metabolism; D011041:Poisoning; D012989:Soil Pollutants / Q000032:analysis / Q000633:toxicity*
chemical_list: D019216:Metals, Heavy; D012989:Soil Pollutants