title: Assessment of the Zn-Co mixtures rhizotoxicity under Ca deficiency: using two conventional mixture models based on the cell membrane surface potential.
abstract: Toxicity assessment of Zn-Co mixtures involves multiple ions interactions. The negative potential (ψ0) at the cell membrane surface (CMs) concentrated cationic toxicants (denoted {M(2+)}0) and influenced the rhizotoxicity of Co(2+) or Zn(2+). The single and joint rhizotoxicity of Co(2+) and Zn(2+) to wheat (Triticum aestivum L.) were examined, coupled with different Ca(2+) levels. Joint effects of Zn(2+), Co(2+) and Ca(2+) were estimated by the linearly extended concentration addition (CA) and response addition (RA) models. Incorporation of Ca(2+) in single metal toxicity assessment significantly enhanced the prediction accuracy (r(2) increased from 0.948 to 0.550 for Zn(2+) and from 0.903 to 0.611 for Co(2+), respectively). ψ0 affected the multiple metals toxicity in both conventional mixture models (r(2)=0.814 for CA model and 0.820 for RA model). Concretely, {Zn(2+)}0 alleviated the toxicity of {Co(2+)}0, while {Co(2+)}0 had non-significant effect on {Zn(2+)}0 toxicity. Growth responses to {Ca(2+)}0 were substantially affected by {Zn(2+)}0 and {Co(2+)}0. Ca addition in medium decreased the {M(2+)}0 by reducing the ψ0 negativity, moreover this addition alleviated Ca deficiency at CMs induced by Zn(2+) (or Co(2+)). These consistent results from both extended CA and RA models indicated that ψ0 provided a novel sight for understanding the rhizotoxicity of multiple metals.
authors.affiliation: Key Laboratory of Soil Environment & Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Wang
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland 4072, Australia.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Key Laboratory of Soil Environment & Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Ling-Fei
authors.initials: LF
authors.lastname: Ni
authors.affiliation: Key Laboratory of Soil Environment & Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Xiu-Zhen
authors.initials: XZ
authors.lastname: Hao
authors.affiliation: Key Laboratory of Soil Environment & Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: dmzhou@issas.ac.cn.
authors.forename: Dong-Mei
authors.initials: DM
authors.lastname: Zhou
mesh_terms: D002118:Calcium / Q000172:deficiency* / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects*; D003035:Cobalt / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D008564:Membrane Potentials / Q000187:drug effects; D008962:Models, Theoretical; D018517:Plant Roots / Q000187:drug effects* / Q000254:growth & development; D014908:Triticum / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D015032:Zinc / Q000633:toxicity*
chemical_list: D003035:Cobalt; D015032:Zinc; D002118:Calcium
keywords: Ca deficiency; Cell membrane surface potential; Rhizotoxicity; Root growth; Zn–Co mixture