Accumulation of cadmium by durum wheat roots: bases for citrate-mediated exceptions to the free ion model.
The accumulation of Cd in durum wheat (Triticum turgidum) roots from hydroponic solutions, with the proportion of total Cd (8.9-445 nM Cd) as Cd2+ varied by the addition of citrate, was determined to test the free-ion model (FIM) of metal bioavailability for higher plants. Calcium, Mg, and K were also varied. Citrate enhanced root-Cd accumulation at higher Cd2+ concentrations but not lower relative to the same Cd2+ concentrations in solutions containing 0 mM citrate. Elevating Ca2+ and Mg2+ concentrations in the citrate solution to the same as those in control solutions alleviated some of the citrate-mediated enhancement but not all. Solutions containing 66% less Ca or Mg than control but the same Cd2+ concentration and no citrate also resulted in increased root Cd. Elevated K+ did not influence Cd accumulation. Regression relationships between root-Cd accumulation and total Cd in solution were similar for the control and pooled amended solutions, whereas they were different for root-Cd accumulation and solution Cd2+. These results contribute to the growing body of evidence that the FIM alone is likely insufficient to predict plant accumulation of metals from soils, although it may be a useful probe for the mechanistic bases of metal bioavailability.
Department of Land Resource Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Edward
E
Berkelaar
Beverley A
BA
Hale
D001682:Biological Availability; D002104:Cadmium / Q000737:chemistry / Q000493:pharmacokinetics*; D002118:Calcium / Q000737:chemistry / Q000494:pharmacology; D002412:Cations; D019343:Citric Acid / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008274:Magnesium / Q000737:chemistry / Q000494:pharmacology; D008954:Models, Biological; D018517:Plant Roots / Q000378:metabolism*; D011188:Potassium / Q000737:chemistry / Q000494:pharmacology; D012044:Regression Analysis; D014908:Triticum / Q000378:metabolism*
D002412:Cations; D002104:Cadmium; D019343:Citric Acid; D008274:Magnesium; D011188:Potassium; D002118:Calcium