Development of a biotic ligand model (BLM) predicting nickel toxicity to barley (Hordeum vulgare)

Abstract A biotic ligand model (BLM) was developed to predict nickel toxicity, affecting root growth of barley ( Hordeum vulgare ), in nutrient solutions. The extent to which Ca 2+ , Mg 2+ , Na + , K + ions and pH each influenced nickel toxicity was determined. Higher activities of Mg 2+ linearly increased the 4 d EC50 Ni 2 + , while Ca 2+ , Na + , K + and H + activities did not significantly influence Ni 2+ toxicity. Stability constants for the binding of Ni 2+ and Mg 2+ to the biotic ligand were obtained: log  K NiBL  = 5.27 and log  K MgBL  = 3.47. Further, it was calculated that on average 57% of the biotic ligand sites needed to be occupied by nickel to induce 50% root growth inhibition. Auto-validation of the BLM indicated that predicted EC50s differed from the observed EC50s by a factor of less than 2, indicating that the BLM concept may also be used to predict metal toxicity to terrestrial plants.