Utilization of iron by oat when supplied as ferrated synthetic chelate or as ferrated hydroxamate siderophore

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Abstract
Utilization of iron by oat (Avena sativa, var. Victory) when supplied as ferrated ethylenediamine[di(o‐hydroxyphenylacetic) acid] (EDDHA), or the ferrated microbially‐produced hydroxamate siderophore, ferrichrome, was examined. Ten‐day‐old iron‐deficient seedlings, grown in aerated Hoagland's nutrient solution (minus iron) buffered at pH 7.0 with CaCO3, were placed in fresh nutrient solution in which 10‐8M 55FeCl3 (23.7 mCi/mg) was added with excess EDDHA (10‐5M), excess ferrichrome (10‐5M), or without chelate, and grown for 6 days. At 2, 4, and 6 days, 55Fe content of shoots from the ferrichrome treatment was significantly greater than from the EDDHA treatment, and at 6 days was nearly 100X greater (10154 vs. 112 dpm mg‐1 dry wt.). Although oat readily utilized iron from ferrichrome relative to EDDHA when ligand was in excess of total iron, uptake of 55Fe by plants was greater in the no chelate treatment. Reduction of chlorosis was evident in both the ferrichrome and no chelate treatments. Results suggest that iron uptake by monocots may be more efficient from naturally‐occurring chelates than from synthetic chelates.