Iron Requirement and Iron Uptake from Various Iron Compounds by Different Plant Species

The Fe requirements of four monocotyledonous plant species (Avena sativa L., Triticum aestivum L., Oryza sativa L., Zea mays L.) and of three dicotyledonous species (Lycopersicum esculentum Mill., Cucumis sativus L., Glycine maxima (L.) Merr.) in hydroponic cultures were ascertained. Fe was given as NaFe-EDDHA chelate (Fe ethylenediamine di (O-hydroxyphenylacetate). I found that the monocotyledonous species required a substantially higher Fe concentration in the nutrient solution in order to attain optimum growth than did the dicotyledonous species. Analyses showed that the process of iron uptake was less efficient with the monocotyledonous species. When the results obtained by using chelated Fe were compared with those using ionic Fe, it was shown that the inefficient species were equally inefficient in utilizing Fe(3+) ions. However, the differences between the efficient and the inefficient species disappeared when Fe(2+) was used. This confirms the work of others who postulated that Fe(3+) is reduced before uptake of chelated iron by the root. In addition, it was shown that reduction also takes place when Fe is used in ionic form. The efficiency of Fe uptake seems to depend on the efficiency of the root system of the particular plant species in reducing Fe(3+). The removal of Fe from the chelate complex after reduction to Fe(2+) seems to present no difficulties to the various plant species.