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Solubilization of iron by water‐extractable humic substances
Author(s) -
Cesco Stefano,
Römheld Volker,
Varanini Zeno,
Pinton Roberto
Publication year - 2000
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200006)163:3<285::aid-jpln285>3.0.co;2-z
Subject(s) - chemistry , hydroxide , humic acid , solubilization , ligand (biochemistry) , soil water , environmental chemistry , fraction (chemistry) , adsorption , elution , water soluble , nuclear chemistry , inorganic chemistry , chromatography , fertilizer , organic chemistry , geology , soil science , biochemistry , receptor
The capability of water‐extractable humic substances (WEHS) to solubilize Fe from sparingly soluble Fe‐hydroxide was studied. Addition of WEHS (1.7 mmol organic C l —1 ) to a dialysis tube containing labeled insoluble Fe‐hydroxide caused an increase in the amount of 59 Fe measured in the external solution. The humic fraction was also able to solubilize Fe from soil samples, with levels comparable to those obtained using a solution containing 100μM DTPA. By measuring the amount of 59 Fe eluted from soil columns pre‐loaded with 59 Fe‐WEHS it was possible to evaluate the mobility of Fe complexed to the humic molecules. The recovery of 59 Fe varied from 2% to 25% in respect to the soil type used. The ability of Fe‐WEHS to serve as an Fe source for the phytosiderophore hydroxy‐mugineic acid (HMA) was also analyzed. The removal of 59 Fe from the Fe‐WEHS complex by HMA was demonstrated by adding the phytosiderophore to a dialysis tube containing the 59 Fe‐WEHS complex. The observations suggested a ligand exchange between the phytosiderophore and the humic fraction. The results indicate that WEHS is able to increase the amount of Fe present in the soil solution, possibly by forming mobile complexes with the micronutrient. These complexes could act as easily available Fe sources in Fe acquisition processes by both monocot and dicot plants, playing an important role particularly in soils with low available Fe.