Refining a biotic ligand model for nickel toxicity to barley root elongation in solution culture

摘要

The effects of widely ranged pH and some cations on nickel (Ni) toxicity to barley root elongation were determined using a biotic ligand model (BLM) in solution culture. The results showed that Ni toxicity decreased with increases of Mg~(2+) and Ca~(2+) activities, but not for Na~+ and K~+ activities. Higher H~+ activity decreased the toxicity through H~+ competition with Ni~(2+) bound to biotic ligands at pH<7.0 or through the change of Ni species in solution at pH≥7.0. When pH≥7.0 the Ni~(2+) plus NiHCO_3~+ were found to be toxic to barley root elongation. The conditional binding constants for Ni~(2+), NiHCC_3~+, H~+, Mg~(2+) and Ca~(2+) with biotic ligand were obtained: log K_(NiBL). 4.83; log K_(NiHCO_3BL). 5.36; log K_(HBL)L. 4.29; log K_(MgBL), 4.01 and log K_(CaBL), 1.60. It is suggested that in solutions with pH≥7.0 free Ni~(2+) as well as NiHCO_3~+, Mg~(2+) and Ca~(2+) competitions with Ni~(2+), should be considered for BLM development.