Effect of cations on copper toxicity to wheat root: implications for the biotic ligand model.
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.
Luo
Xiao-San
XS
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.
Li
Lian-Zhen
LZ
Zhou
Dong-Mei
DM
D003300:Copper / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D018517:Plant Roots / Q000187:drug effects*; D014908:Triticum / Q000187:drug effects*
D008024:Ligands; D003300:Copper