Pedosphere 28(1): 59--69, 2018
ISSN 1002-0160/CN 32-1315/P
©2018 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Iron Mobilization and Mineralogical Alterations Induced by Iron-Deficient Cucumber Plants (Cucumis sativus L.) in a Calcareous Soil
Concetta Eliana GATTULLO1, Youry PⅡ2, Ignazio ALLEGRETTA1, Luca MEDICI3, Stefano CESCO2, Tanja MIMMO2, Roberto TERZANO1
1Department of Soil, Plant and Food Sciences, University of Bari “Aldo Moro”, 70126 Bari (Italy)
2Faculty of Science and Technology, Free University of Bozen/Bolzano, 39100 Bolzano (Italy)
3Institute of Methodologies for Environmental Analysis, National Research Council of Italy (I. M. A. A. -C. N. R.), 85050 Tito Scalo (Italy)
Corresponding Author:Concetta Eliana GATTULLO
ABSTRACT
      Dicotyledons cope with ion (Fe) shortage by releasing low-molecular-weight organic compounds into the rhizosphere to mobilize Fe through reduction and complexation mechanisms. The effects induced by these root exudates on soil mineralogy and the connections between Fe mobilization and mineral weathering processes have not been completely clarified. In a batch experiment, we tested two different kinds of organic compounds commonly exuded by Fe-deficient plants, i.e., three organic acids (citrate, malate, and oxalate) and three flavonoids (rutin, quercetin, and genistein), alone or in combination, for their ability to mobilize Fe from a calcareous soil and modify its mineralogy. The effect of root exudates on soil mineralogy was assessed in vivo by cultivating Fe-deficient and Fe-sufficient cucumber plants (Cucumis sativus L.) in a RHIZOtest device. Mineralogical analyses were performed by X-ray powder diffraction. The batch experiment showed that citrate and, particularly, rutin (alone or combined with organic acids or genistein) promoted Fe mobilization from the soil. The combinations of rutin and organic acids modified the soil mineralogy by dissolving the amorphous fractions and promoting the formation of illite. These mineralogical alterations were significantly correlated with the amount of Fe mobilized from the soil. The RHIZOtest experiment revealed a drastic dissolution of amorphous components in the rhizosphere soil of Fe-deficient plants, possibly caused by the intense release of phenolics, amino acids, and organic acids, but without any formation of illite. Both batch and RHIZOtest experiments proved that exudates released by cucumber under Fe deficiency concurred to the rapid modification (on a day-scale) of the mineralogy of a calcareous soil.
Key Words:  flavonoids,mineral weathering,organic acids,rhizosphere,X-ray powder diffraction
Citation: Gattullo C E, Pii Y, Allegretta I, Medici L, Cesco S, Mimmo T, Terzano R. 2018. Iron mobilization and mineralogical alterations induced by iron-deficient cucumber plants (Cucumis sativus L.) in a calcareous soil. Pedosphere. 28(1):59-69.
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