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Identification of hydroxyl copper toxicity to barley ( Hordeum vulgare ) root elongation in solution culture
Author(s) -
Wang Xuedong,
Ma Yibing,
Hua Luo,
McLaughlin Mike J.
Publication year - 2009
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/07-641.1
Subject(s) - hordeum vulgare , toxicity , elongation , ec50 , ligand (biochemistry) , chemistry , copper toxicity , zoology , biology , biochemistry , poaceae , botany , receptor , in vitro , materials science , organic chemistry , ultimate tensile strength , metallurgy
The effect of pH on the acute toxicity of Cu to barley ( Hordeum vulgare ) root elongation was investigated in solution culture. The results showed that the median effective concentrations (EC50s; i.e., the concentration that reduced root elongation by 50% based on free Cu 2+ activity) were not significantly different in the low‐pH range from 4.5 to 6.5, but in the high‐pH range from 7.0 to 8.0, a significant effect of pH on EC50s was found. The nonlinear relationship between EC50 and H + activity in the present study indicated that the increased toxicity with increasing pH in solution may not be caused by decreasing H + competition. When we take account of CuOH + activities, a good linear relationship ( r 2 > 0.97) between the ratio of CuOH + activity to free Cu 2+ activity and acute Cu toxicity to barley root elongation was achieved, which indicated that the observed toxicity in the high‐pH range may be caused by CuOH + plus free Cu 2+ in solution. Linear‐regression analysis suggested CuOH + had a greater binding affinity than Cu 2+ at the biotic ligand sites. The logistic dose–response curve showed that expressing the Cu dose as Cu 2+ + 2.92·CuOH + improved the data fit significantly compared to consideration of the free Cu 2+ activity only. Thus, our results suggest CuOH + was highly toxic to barley root elongation. The enhanced toxicity of CuOH + therefore needs to be considered when modeling the effect of pH on Cu toxicity to barley for exposures having pH greater than 6.5.

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