Ferric reduction by geum urbanum: A kinetic study

Abstract

The reduction capacity for ferric chelates of Geum urbanum L. showed a marked increase when plants were grown under conditions of iron‐shortage. Ferric ethylenediaminetetraacetate (FeEDTA) was reduced with a pH optimum between 5 and 6. The reaction exhibited a low substrate affinity with a K_m much higher than the expected concentration range of soluble iron in the soil. Analysis of the saturation plots conform to Michaelis‐Menten kinetics. Both V_max and K_m values varied to a broad extent with changing assay and plant culturing conditions. Ferricyanide was reduced at significantly higher rates than FeEDTA and inhibited the reduction of FeEDTA compete‐tively. The kinetic characteristics of iron reduction by plants will be discussed in terms of ecological significance as part of an adaptation to the soil conditions.