1 research outputs found
Geochemical Processes Constraining Iron Uptake in Strategy II Fe Acquisition
Phytosiderophores
(PS) are natural chelating agents, exuded by
graminaceous plants (grasses) for the purpose of Fe acquisition (Strategy
II). They can form soluble Fe complexes with soil-Fe that can be readily
taken up. PS are exuded in a diurnal pulse release, and with the start
of PS release a “window of iron uptake” opens. In the
present study we examined how this window is constrained in time and
concentration by biogeochemical processes. For this purpose, a series
of interaction experiments was done with a calcareous clay soil and
the phytosiderophore 2′-deoxymugineic acid (DMA), in which metal and DMA speciation were examined as a
function of time and DMA concentration. Various kinetically and thermodynamically
controlled processes affected the size of the window of Fe uptake.
Adsorption lowered, but did not prevent Fe mobilization by DMA. Microbial
activity depleted DMA from solution, but not on time scales jeopardizing
Strategy II Fe acquisition. Complexation of competing metals played
an important role in constraining the window of Fe uptake, particularly
at environmentally relevant PS concentrations. Our study provides
a conceptual model that takes into account the chemical kinetics involved
with PS-mediated Fe acquisition. The model can help to explain how
success or failure of PS-mediated Fe acquisition depends on environmental
conditions