Background: The determination of the plant-induced Fe-isotopic fractionation is a promising tool to better quantify their role in the geochemical Fe cycle and possibly to identify the physiological mechanisms of Fe uptake and translocation in plants. Here we explore the isotope fractionation caused by translocation of Fe during growth of bean and oat as representatives of strategy I and II plants. Methods: Plants were grown on a nutrient solution supplemented with Fe(III)-EDTA and harvested at three different ages. We used the technique of multi-collector ICP-MS to resolve the small differences in the stable iron isotope compositions of plants. Results: Total bean plants, regardless of their age, were found to be enriched in the light iron isotopes by -1.2‰ relative to the growth solution throughout. During growth plants internally redistributed isotopes where young leaves increasingly accumulated the lighter isotopes whereas older leaves and the total roots were simultaneously depleted in light iron isotopes. Oat plants were also enriched in the light iron isotopes but during growth the initial isotope ratio maintained in all organs at all growth stages. Conclusions: We conclude that isotope fractionation in bean as a representative of strategy I plants is a result of translocation or re-translocation processes. Furthermore we assume that both uptake and translocation of Fe in oat maintains the irons' ferric state, or that Fe is always bound to high-mass ligands, so that isotope fractionation is virtually absent in these plants. However, in contrast to our previous study in which strategy II plants were grown on soil substrate, oat plants grown on Fe(III)-EDTA contain iron that enriches

The stable isotopes of iron disclose the metabolic pathways of iron within the human food chain. We have measured with precise multicollector ICP-MS the iron concentrations and stable isotope composition of 60 food products that are representative of the average German diet. We find that vegetable falls within the range typical of strategy I plants (-0.1 ‰ to -1.4 ‰ in δ 56 Fe), crop products and processed crop food into the range typical of strategy II plants (-0.6 ‰ to +0.4 ‰), and animal products into the 54 Fe-enriched range known for animal tissue and blood (-1.1 ‰ to -2.7 ‰). Weighting these isotope compositions by the average iron dietary sources, we find a representative composition of European vegetarian diet of -0.45 ‰, while that of omnivores is -0.82 ‰. For human blood, known to be enriched in light iron isotopes, we find a fractionation factor for iron absorption of -2.0 ‰ to -2.3 ‰ for vegetarians (female and male, respectively), and -1.3 ‰ to -1.5 ‰ for omnivores (female and male, respectively). Knowing these fractionation factors is a prerequisite for using stable iron isotope ratios in blood as monitors of intestinal iron uptake regulation.