A new powder formulation obtained from bovine blood (Fe-heme) was tested on cucumber (Cucumis sativus L.) to investigate its effectiveness as iron supply in comparison with two synthetic iron-chelates fertilizers: ethylenediaminetetraacetic acid (EDTA/Fe3+) and ethylenediamine-N’N’-bis(2-hydroxyphenyl acetic acid) (o,oEDDHA/Fe3+). Green stressed cucumber plants were evaluated in their recovery (SPAD index and weight variations) and to test the iron reduction capacity of the roots at pH 7.5 and 6.0 using each iron treatment as iron supply. The blood-derived product showed similar effects on decreasing iron-deficiency symptoms: SPAD increments and the weights of plants were similar. Noteworthy, the average of Fe3+ reduction capacity in roots was higher for EDTA/Fe3+, while it was similar for o,oEDDHA/Fe3+, and Fe-heme at pH 7.5. Fe-heme showed a complex behavior due to aggregation and low solubility at pH 6 and showed an unexpectedly high contribution of root exudates to iron reduction.
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