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(P105) A method for modeling bioavailability in non-equilibrated systems.
Cypas, Paula*,1, Hale, Beverley1, 1 University of Guelph, Guelph, ON, Canada
ABSTRACT- The BLM: Can it be applied to higher plants? Time-course experiments for durum wheat (Triticum turgidum) were conducted to test the hypothesis that root binding sites equilibrate with copper over time. From these data, methodology was developed and applied to a Langmuir Isotherm, an equation required by the BLM to calculate a conditional stability constant and the number of root binding sites. Roots of live and dead plants were exposed to fixed free copper concentrations ([Cu2+] = 10-7M, 10-6M and 10-5M) in chemically controlled aqueous media (I=0.03M, pe = 15, 20oC). After HNO3 digestion and analysis with F-AAS, multiple regression analysis was performed and tested for best fit. Results demonstrate that copper accumulation by roots continues to increase for both metabolically active (r2=0.979) and inactive (r2>0.960) plants, for 384 and 56 hours, respectively. The null-hypothesis was therefore rejected, a conclusion that opposes the equilibrium concept of the classically applied BLM. To create a Langmuir Isotherm under non-equilibrium conditions, roots exposed to nine [Cu2+] concentrations (0 to 10-3M, I = 0.03M, pe = 15, 20oC) were sampled every four days over a 16 day period. Dose-accumulation data were analyzed by linearization through semi-log transformation and extrapolated to time zero. The calculated conditional stability constant and number of root binding sites accounts for the continually increasing nature of copper uptake in a non-equilibrated system and is a step towards an application of the BLM to higher plants.
Key words: BLM, durum wheat, copper, non-equilibrium systems
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