title: Effect of cations on copper toxicity to wheat root: implications for the biotic ligand model.
abstract: The extent to which calcium, magnesium, sodium, potassium and hydrogen ions independently mitigate Cu rhizotoxicity to wheat (Triticumaestivum) in nutrient solutions was examined. Increasing activities of Ca2+ and Mg2+ but not Na+, K+ and H+ linearly increased the 2 d EC50 (as Cu2+ activity), supporting the concept that some cations can compete with Cu2+ for binding the active sites at the terrestrial organism-solution interface (i.e., the biotic ligand, BL). According to the biotic ligand model (BLM) concept, the conditional stability constants for the binding of Cu2+, Ca2+ and Mg2+ to the BL were derived from the toxicity data. They were 6.28, 2.43 and 3.34 for logK(CuBL), logK(CaBL) and logK(MgBL), respectively. It was calculated that on average 43.6% of BL sites need to be occupied by Cu2+ to induce 50% root growth inhibition. Using the estimated parameters, a BLM was successfully developed to predict Cu toxicity for wheat as a function of solution characteristics.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; Graduate School of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xiao-San
authors.initials: XS
authors.lastname: Luo
authors.forename: Lian-Zhen
authors.initials: LZ
authors.lastname: Li
authors.forename: Dong-Mei
authors.initials: DM
authors.lastname: Zhou
mesh_terms: D003300:Copper / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D018517:Plant Roots / Q000187:drug effects*; D014908:Triticum / Q000187:drug effects*
chemical_list: D008024:Ligands; D003300:Copper