Understanding the distribution of elements in plants is important for researchers across a broad range of fields, including plant molecular biology, agronomy, plant physiology, plant nutrition, and ionomics. However, it is often challenging to evaluate the applicability of the wide range of techniques available, with each having their own strengths and limitations.Here, we compare scanning/transmission electron microscopy-based energy-dispersive X-ray spectroscopy (SEM-EDS, TEM-EDS), X-ray fluorescence microscopy (XFM), particleinduced X-ray emission (microPIXE), laser ablation ICP-MS (LA-ICP-MS), nanoscale secondary ion mass spectroscopy (NanoSIMS), autoradiography, and confocal microscopy with fluorophores. For these various techniques, we compare their accessibility, their ability to analyze hydrated tissues (without sample preparation) and suitability for in vivo analyses, as well as examining their most important analytical merits such as resolution, sensitivity, depth of analysis, and the range of elements that can be analyzed. We hope that this information will assist other researchers to select, access, and evaluate the approach that is most useful in their particular research program or application.

Studies of Li depletion in sections of Li 2 CO 3 -primer comprising a polyurethane binder, MgO, TiO 2 , BaSO 4 in addition to Li 2 CO 3, were performed using a combination of particle induced γ-ray and X-ray emission spectroscopies along with SEM/EDS analysis. A mixture of depletion behaviours were observed. At the earliest stages (to around 48 hours) initial release was confined to the surface. At longer times (168 hours) voids developed deeper into the primer and after 500 hours Li 2 CO 3 dissolution was observed at places throughout the thickness of the primer to the metal/primer interface. Microscopic transport pathways formed which involved all large inorganic particles. SEM showed that rupture of the polyurethane matrix contributed to network formation. Finite element analysis indicated that rupture may be due to internal stresses around particles isolated in the polyurethane matrix and associated with water uptake. Thus the transport network seemed to be generated by chemical dissolution at the particle/polymer interface and may be enhanced by mechanical degradation due to internal mechanical stresses. The release kinetics of Li 2 CO 3 inhibitor from the primer was followed as a function of time and the data analysed according to a release behaviour of t n . There was very rapid initial release of Li followed by a slower release of Mg and to a lesser extent Ba. The value of n varied significant with time, but showed a mixture of Fickian release and direct dissolution for Mg and Ba at intermediate times, but transport through a pore network at longer times. The leaching data was interpreted in terms of local transport networks that developed in the primer with time.

Background The fern Dicranopteris linearis is a hyperaccumulator of rare earth elements (REEs), aluminium (Al) and silicon (Si). However, the physiological mechanisms of tissue-level tolerance to high concentrations of REE and Al, and possible interactions with Si, are currently incompletely known. Methods In this study, particle-induced X-ray emission (μPIXE) microprobe with the Maia detector, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and chemical speciation modelling were used to decipher the localisation and biochemistry of REEs, Al and Si in D. linearis during uptake, translocation and sequestration processes. Results The results show that in the roots more than 80% REEs and Al are in apoplastic fractions, among which the REEs are most significantly co-localised with Si and phosphorus (P) in the epidermis. In the xylem sap, REEs are nearly 100% present as REEH3SiO4  2+, without significant differences between the REEs; while 24–45% Al as Al-citrate, and only 1.7–16% Al as AlH3SiO4  2+. In the pinnules, REEs are mainly concentrated in necrotic lesions and in the epidermis, and REEs and Al are possibly co-deposited within phytoliths (SiO2). Finally, we report that different REEs have similar spatial localisations in the epidermis and exodermis of roots, the necrosis, veins and epidermis of pinnae of D. linearis. Conclusions In conclusion, we posit that Si plays a critical role in REEs and Al tolerance within the root apoplast, transport within vascular bundle, and sequestration within the blade of D. linearis.

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