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Element distribution and iron speciation in mature wheat grains ( Triticum aestivum L.) using synchrotron X‐ray fluorescence microscopy mapping and X‐ray absorption near‐edge structure (XANES) imaging
Author(s) -
De Brier Niels,
Gomand Sara V.,
Donner Erica,
Paterson David,
Smolders Erik,
Delcour Jan A.,
Lombi Enzo
Publication year - 2016
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.12749
Subject(s) - xanes , aleurone , genetic algorithm , synchrotron , absorption (acoustics) , microscopy , grain boundary , chemistry , analytical chemistry (journal) , x ray absorption spectroscopy , scutellum , materials science , endosperm , absorption spectroscopy , spectroscopy , crystallography , biology , environmental chemistry , optics , microstructure , physics , biochemistry , quantum mechanics , evolutionary biology , composite material
Several studies have suggested that the majority of iron (Fe) and zinc (Zn) in wheat grains are associated with phytate, but a nuanced approach to unravel important tissue‐level variation in element speciation within the grain is lacking. Here, we present spatially resolved Fe‐speciation data obtained directly from different grain tissues using the newly developed synchrotron‐based technique of X‐ray absorption near‐edge spectroscopy imaging, coupling this with high‐definition μ‐X‐ray fluorescence microscopy to map the co‐localization of essential elements. In the aleurone, phosphorus (P) is co‐localized with Fe and Zn, and X‐ray absorption near‐edge structure imaging confirmed that Fe is chelated by phytate in this tissue layer. In the crease tissues, Zn is also positively related to P distribution, albeit less so than in the aleurone. Speciation analysis suggests that Fe is bound to nicotianamine rather than phytate in the nucellar projection, and that more complex Fe structures may also be present. In the embryo, high Zn concentrations are present in the root and shoot primordium, co‐occurring with sulfur and presumably bound to thiol groups. Overall, Fe is mainly concentrated in the scutellum and co‐localized with P. This high resolution imaging and speciation analysis reveals the complexity of the physiological processes responsible for element accumulation and bioaccessibility.