Further studies on the influence of BPDS on the uptake of chelated iron by plants

Abstract Bush bean plants were exposed to 59FeEDDHA (2×l0‐5 M) for 22 hours with and without CaCO3 in the nutrient solution for pH differential (less than 7 and over 7) and also with combinations of 10‐4 M BPDS (bathophenanthroline‐disulfonate), 10‐4 M EDDHA, 10‐4 M EDTA, 10‐2 M H2O2 and 3×10‐5 M FeSO4 and 5×10‐5 M FeSO4. The BPDS and excess EDDHA both inhibited accumulation of the labeled iron in various plant parts but not additively. This implies a pe + pH of 10 or less unless the chelated Fe were absorbed intact. The excess EDDHA and EDTA decreased slightly the inhibiting effect of BPDS at both pH values. This implies a pe + pH of less than 10. When sufficient FeSO4 was applied to chelate all of the BPDS, inhibition of iron uptake still occurred, although the effect was less than with the unchelated BPDS. The high rate of FeSO4 decreased the inhibition more than did the low rate although high pH may decrease the availability of the residual 2 × 10‐5M Fe2+ . Hydrogen peroxide, an oxidizing agent, decre...