Constraints to Synergistic Fe Mobilization from Calcareous Soil by a Phytosiderophore and a Reductant

Abstract

Synergistic effects between ligand- and reductant-based Fe acquisition strategies can enhance the mobilization of Fe, but also of competing metals from soil. For phytosiderophores, this may alter the time and concentration window of Fe uptake during which plants can benefit from elevated Fe concentrations. We examined how the size of this window is affected by the ligand and reductant concentration and by non-simultaneous addition. To this end, a series of kinetic batch experiments was conducted with a calcareous clay soil to which the phytosiderophore 2′-deoxymugineic acid (DMA) and the reductant ascorbate were added at various concentrations, either simultaneously or with a one- or two-day lag time. Both simultaneous and non-simultaneous addition of the reductant and the phytosiderophore induced synergistic Fe mobilization. Furthermore, initial Fe mobilization rates increased with increasing reductant and phytosiderophore concentrations. However, the duration of the synergistic effect and the window of Fe uptake decreased with increasing reductant concentration due to enhanced competitive mobilization of other metals. Rate laws accurately describing synergistic mobilization of Fe and other metals from soil were parameterized. Synergistic Fe mobilization may be vital for the survival of plants and microorganisms in soils of low Fe availability. However, in order to optimally benefit from these synergistic effects, exudation of ligands and reductants in the rhizosphere need to be carefully matched.

Temporal Responses to Direct and Induced Iron Deficiency in Parietaria judaica

“…It is well known that the presence of carbonates in soils causes a decrease in the solubility of Fe and other micronutrients [21,22]. In fact, at a high soil pH there are several essential elements (notably P, Fe, and Mn) that are barely present in soluble or easily available forms.…”

Stable Cu Isotope Ratios Show Changes in Cu Uptake and Transport Mechanisms in Vitis vinifera Due to High Cu Exposure

“…On one hand, this can be used to limit toxicity, durum wheat for example drastically reduced the Cu bioavailability in contaminated soils by rhizosphere alkalization ( Hinsinger et al, 2003 ; Bravin et al, 2009a , 2012 ). On the other hand, the solubility of scarcely available nutrients such as iron (Fe) can be increased by exudation of reducing agents and phytosiderophores ( Kraemer, 2004 ; Schenkeveld and Kraemer, 2018 ). Note that both strategies are not ion-specific and will affect other elements as well ( Hinsinger et al, 2003 ; Bravin et al, 2009a ; Schenkeveld and Kraemer, 2018 ).…”

“…On the other hand, the solubility of scarcely available nutrients such as iron (Fe) can be increased by exudation of reducing agents and phytosiderophores ( Kraemer, 2004 ; Schenkeveld and Kraemer, 2018 ). Note that both strategies are not ion-specific and will affect other elements as well ( Hinsinger et al, 2003 ; Bravin et al, 2009a ; Schenkeveld and Kraemer, 2018 ).…”