Translocation ofIronfromSoybe Cotyledons1

Soybeanseeds, Glycine max L.Merrill, wereproduced by plants treated fromanthesis toseedmaturity with'Fesupplied as ferric ethylenediaminedi(o-hydroxyphenylacetate). Seed coatsaccounted for7.4%ofdryseedweight andhadFe concentrations 5 timesgreater thantheembryos. After germinating 2 days, cotyledons contained 69.6%andradicles 5.0%oforiginal seedFe.Fractions ofseedFeunavailable to seedlings were:19.8%inseedcoats, 1.7%ingermination paper, 0.1% inthewaterundergerminating seeds, and3.8% unaccounted for.Every 3daysseedlings received nutrient solutionwithout Fe orwith10gMferric ethylenediaminedi(ohydroxyphenylacetate) anddeveloped as-deficient FeornormalFeplants. Thedeficient Fecotyledons onday18retained 13% ofthelabeled Feoriginally present. Cotyledons ofnormal Feplants retained 50to70% oftheir original Fe.Moreover, cotyledons ofthenormalFe plants accumulated externally supplied Fe andfinally contained twicethequantity ofFe originally present. Stemexudate collected abovecotyledons ofdeficient Feplants contained 5.3/M'Fe.Eleetrophoresis of exudate showedthat mostofthe'Femigrated anodically asa single bandandwasintheposition offerric citrate.