Stable isotope fractionation of cadmium in the soil-rice-human continuum

Zhang, Shengnan; Gu, Yi; Zhu, Zhenli; Hu, Shenghong; Kopittke, Peter M.; Zhao, Fang‐Jie; Wang, Peng

doi:10.1016/j.scitotenv.2020.143262

Cited by 35 publications

(67 citation statements)

References 55 publications

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“…Hence, the Cd isotope fractionation within the plant can strongly contribute to the enrichment of heavy Cd isotopes in the grains. This enrichment of heavy isotopes in rice grains corresponds with previously reported Cd isotope ratios for rice grown on contaminated soils in the field ( Zhang et al, 2021 ) as well as for wheat and barley that grew on non- or moderately contaminated soils ( Wiggenhauser et al, 2016 ; Imseng et al, 2019 ). In addition to isotope ratios, we measured the Cd speciation in the shoot and straw, which may partly control the shoot-to-grain transfer of Cd.…”

Section: Discussionsupporting

confidence: 88%

“…The same pattern was also observed in wheat, barley, and cacao seedlings ( Wiggenhauser et al, 2016 ; Imseng et al, 2019 ; Moore et al, 2020 ). For hydroponically grown rice seedlings that were exposed for 3 days to 0.1 μM Cd, the isotope ratios between root and leaves were isotopically not distinguishable in wild-type plants, but a slight enrichment of heavy isotopes was observed in leaves when the root vacuolar transporter OsHMA3 was overexpressed ( Zhang et al, 2021 ). Our Cd speciation and isotope data strongly suggest that Cd in the roots was bound to chelating thiols such as phytochelatin ( Nocito et al, 2011 ; Wiggenhauser et al, 2021 ) after it was transported into the vacuole by OsHMA3 ( Shao et al, 2017 ).…”

Section: Discussionmentioning

confidence: 99%

“…Binding of Cd to organic ligands may impact the transfer of metals through membranes ( Zhao et al, 2016 ). In a next step, Cd storage forms could be coupled with membrane transporters by comparing wild-type and mutant plants that lack or overexpress specific membrane transporters ( Cadiou et al, 2017 ; Pokharel et al, 2018 ; Lei et al, 2020 ; Moore et al, 2020 ; Wiggenhauser et al, 2021 ; Zhang et al, 2021 ).…”

Section: Implications and Outlookmentioning

confidence: 99%

“…In addition, processes that control the mobility of metals in living organisms can be also partly kinetically controlled through, e.g., fast and unidirectional membrane transport ( Köbberich and Vance, 2017 ). Such a kinetically controlled Cd isotope fractionation may occur during Cd uptake into plants and leads to an enrichment of light isotopes compared to soil solution or nutrient solution in hydroponics ( Wei et al, 2016 ; Imseng et al, 2019 ; Moore et al, 2020 ; Zhang et al, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

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Changes of Cadmium Storage Forms and Isotope Ratios in Rice During Grain Filling

et al. 2021

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Rice poses a major source of the toxic contaminant cadmium (Cd) for humans. Here, we elucidated the role of Cd storage forms (i.e., the chemical Cd speciation) on the dynamics of Cd within rice. In a pot trial, we grew rice on a Cd-contaminated soil in upland conditions and sampled roots and shoots parts at flowering and maturity. Cd concentrations, isotope ratios, Cd speciation (X-ray absorption spectroscopy), and micronutrient concentrations were analyzed. During grain filling, Cd and preferentially light Cd isotopes were strongly retained in roots where the Cd storage form did not change (Cd bound to thiols, Cd–S = 100%). In the same period, no net change of Cd mass occurred in roots and shoots, and the shoots became enriched in heavy isotopes (Δ114/110Cdmaturity–flowering = 0.14 ± 0.04‰). These results are consistent with a sequestration of Cd in root vacuoles that includes strong binding of Cd to thiol containing ligands that favor light isotopes, with a small fraction of Cd strongly enriched in heavy isotopes being transferred to shoots during grain filling. The Cd speciation in the shoots changed from predominantly Cd–S (72%) to Cd bound to O ligands (Cd–O, 80%) during grain filling. Cd–O may represent Cd binding to organic acids in vacuoles and/or binding to cell walls in the apoplast. Despite this change of ligands, which was attributed to plant senescence, Cd was largely immobile in the shoots since only 0.77% of Cd in the shoots were transferred into the grains. Thus, both storage forms (Cd–S and Cd–O) contributed to the retention of Cd in the straw. Cd was mainly bound to S in nodes I and grains (Cd–S > 84%), and these organs were strongly enriched in heavy isotopes compared to straw (Δ114/110Cdgrains/nodes–straw = 0.66–0.72‰) and flag leaves (Δ114/110Cdgrains/nodes–flag leaves = 0.49–0.52‰). Hence, xylem to phloem transfer in the node favors heavy isotopes, and the Cd–S form may persist during the transfer of Cd from node to grain. This study highlights the importance of Cd storage forms during its journey to grain and potentially into the food chain.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Implications and Outlookmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Changes of Cadmium Storage Forms and Isotope Ratios in Rice During Grain Filling

et al. 2021

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“…Isotope geochemistry has been increasingly applied in the past years for tracing anthropogenic Cd pollution (Cloquet et al, 2006;Salmanzadeh et al, 2017;Yang et al, 2019), tracing the source of ore-forming fluids (Zhu et al, 2016), to advance the understanding of the past and present marine biogeochemical cycling of Cd Zhang et al, 2018;, as well as to trace processes that control the Cd homeostasis in unicell organisms and distinct types of plants such as grasses Imseng et al, 2018;Zhang et al, 2021), cacao (Barraza et al, 2019, and Cd accumulating plants Zhou et al, 2020). Cd has eight stable isotopes which atomic masses range from 106-116, their ratios can vary significantly in the environment .…”

Section: Introductionmentioning

confidence: 99%