title: Synchrotron-based X-ray absorption near-edge spectroscopy imaging for laterally resolved speciation of selenium in fresh roots and leaves of wheat and rice.
abstract: Knowledge of the distribution of selenium (Se) species within plant tissues will assist in understanding the mechanisms of Se uptake and translocation, but in situ analysis of fresh and highly hydrated plant tissues is challenging. Using synchrotron-based fluorescence X-ray absorption near-edge spectroscopy (XANES) imaging to provide laterally resolved data, the speciation of Se in fresh roots and leaves of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) supplied with 1 μM of either selenate or selenite was investigated. For plant roots exposed to selenate, the majority of the Se was efficiently converted to C-Se-C compounds (i.e. methylselenocysteine or selenomethionine) as selenate was transported radially through the root cylinder. Indeed, even in the rhizodermis which is exposed directly to the bulk solution, only 12-31% of the Se was present as uncomplexed selenate. The C-Se-C compounds were probably sequestered within the roots, whilst much of the remaining uncomplexed Se was translocated to the leaves-selenate accounting for 52-56% of the total Se in the leaves. In a similar manner, for plants exposed to selenite, the Se was efficiently converted to C-Se-C compounds within the roots, with only a small proportion of uncomplexed selenite observed within the outer root tissues. This resulted in a substantial decrease in translocation of Se from the roots to leaves of selenite-exposed plants. This study provides important information for understanding the mechanisms responsible for the uptake and subsequent transformation of Se in plants.
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, 4072, Australia p.wang3@uq.edu.au.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, 4072, Australia.
authors.forename: Neal W
authors.initials: NW
authors.lastname: Menzies
authors.affiliation: University of South Australia, Centre for Environmental Risk Assessment and Remediation, Mawson Lakes, South Australia, 5095, Australia.
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, 4072, Australia.
authors.forename: Brigid A
authors.initials: BA
authors.lastname: McKenna
authors.affiliation: Australian Synchrotron, Clayton, Victoria, 3168, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: James
authors.affiliation: La Trobe University, Centre for AgriBioscience, Bundoora, Victoria, 3086, Australia.
authors.forename: Caixian
authors.initials: C
authors.lastname: Tang
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, 4072, Australia.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kopittke
mesh_terms: D001692:Biological Transport; D001901:Botany / Q000379:methods*; D012275:Oryza / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D064586:Selenic Acid / Q000378:metabolism; D020887:Selenious Acid / Q000378:metabolism; D012643:Selenium / Q000378:metabolism*; D013052:Spectrometry, X-Ray Emission; D017356:Synchrotrons; D014908:Triticum / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D020887:Selenious Acid; D012643:Selenium; D064586:Selenic Acid
keywords: Fluorescence-XANES imaging; laterally resolved speciation; selenium uptake; speciation; transformation; translocation.