The stability constants of metal-PDMA complexes determined by potentiometric titrations and PHREEQC model results were compared with the results of plant uptake experiment published by Suzuki et al. . Briefly, rice (O. sativa, var. nipponbare) plants were transplanted into calcareous soil (pH 9) and treated with unchelated PDMA and PDMA complexed with Fe2(SO4)3 and ZnSO4. Further details are described by Suzuki et al. .