Browsing by Author "Milham, PJ"

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    Can synchrotron micro-x-ray fluorescence spectroscopy be used to map the distribution of cadmium in soil particles?
    (CSIRO Publishing, 2007-10-30) Milham, PJ; Payne, TE; Lai, B; Trautman, RL; Cai, ZH; Holford, P; Haigh, AM; Conroy, JP
    Plants take up cadmium (Cd) from the soil, and the concentration of Cd in some plant products is a health concern. Plant uptake of Cd is poorly predicted by its concentration in soils; consequently, there is interest in the binding and distribution of Cd in soil. Synchrotron micro-X-ray fluorescence spectroscopy (micro-XRFS) is the most sensitive method of observing this distribution. We used beam-line 2-ID-D of the Advanced Photon Source (APS), Argonne, to test whether this technique could map the Cd distribution in 5 soils from Greater Sydney that contained 0.3-6.4 mg Cd/kg. A subsample of one soil was spiked to contain similar to 100 mg Cd/kg. Cadmium was readily mapped in the Cd-enriched subsample, whereas in the unamended soils, only one Cd-rich particle was found; that is, sensitivity generally limited Cd mapping. We also examined a sample of Nauru phosphorite, which was a primary source of much of the Cd in farm soils on the peri-urban fringe of Greater Sydney. The phosphorite contained similar to 100 mg Cd/kg and the Cd was relatively uniformly distributed, supporting the findings of an earlier study on an apatite from Africa. The micro-XRFS at beam-line 2-ID-D of the APS can be reconfigured to increase the sensitivity at least 10-fold, which may allow the distribution of Cd and its elemental associations to be mapped in particles of most agricultural soils and facilitate other spectroscopic investigations. © 2007, CSIRO Publishing
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    Genetic biofortification of wheat with zinc: opportunities to fine‐tune zinc uptake, transport and grain loading
    (Wiley, 2021-12-30) Kamaral, C; Neate, SM; Gunasinghe, N; Milham, PJ; Paterson, DJ; Kopittke, PM; Seneweera, S
    Zinc (Zn) is an important micronutrient in the human body, and health complications associated with insufficient dietary intake of Zn can be overcome by increasing the bioavailable concentrations in edible parts of crops (biofortification). Wheat (Triticum aestivum L) is the most consumed cereal crop in the world; therefore, it is an excellent target for Zn biofortification programs. Knowledge of the physiological and molecular processes that regulate Zn concentration in the wheat grain is restricted, inhibiting the success of genetic Zn biofortification programs. This review helps break this nexus by advancing understanding of those processes, including speciation regulated uptake, root to shoot transport, remobilisation, grain loading and distribution of Zn in wheat grain. Furthermore, new insights to genetic Zn biofortification of wheat are discussed, and where data are limited, we draw upon information for other cereals and Fe distribution. We identify the loading and distribution of Zn in grain as major bottlenecks for biofortification, recognising anatomical barriers in the vascular region at the base of the grain, and physiological and molecular restrictions localised in the crease region as major limitations. Movement of Zn from the endosperm cavity into the modified aleurone, aleurone and then to the endosperm is mainly regulated by ZIP and YSL transporters. Zn complexation with phytic acid in the aleurone limits Zn mobility into the endosperm. These insights, together with synchrotron‐X‐ray‐fluorescence microscopy, support the hypothesis that a focus on the mechanisms of Zn loading into the grain will provide new opportunities for Zn biofortification of wheat. © 2021 Scandinavian Plant Physiology Society.