Zinc and Cadmium Mapping in the Apical Shoot and Hypocotyl Tissues of Radish by High-Resolution Secondary Ion Mass Spectrometry (NanoSIMS) after Short-Term Exposure to Metal Contamination

Abstract

Zinc (as an essential phytonutrient) and cadmium (as a toxic but readily bioavailable nonessential metal for plants) share similar routes for crossing plant biomembranes, although with a substantially different potential for translocation into above-ground tissues. The in situ distribution of these metals in plant cells and tissues (particularly intensively-dividing and fast-growing areas) is poorly understood. In this study, 17-day-old radish (Raphanus sativus L.) plants grown in nutrient solution were subjected to short-term (24 h) equimolar contamination (2.2 µM of each 70Zn and Cd) to investigate their accumulation and distribution in the shoot apex (leaf primordia) and edible fleshy hypocotyl tissues. After 24-h exposure, radish hypocotyl had similar concentration (in µg/g dry weight) of 70Zn (12.1 ± 1.1) and total Cd (12.9 ± 0.8), with relatively limited translocation of both metals to shoots (concentrations lower by 2.5-fold for 70Zn and 4.8-fold for Cd) as determined by inductively-coupled plasma mass spectrometry (ICP-MS). The in situ Zn/Cd distribution maps created by high-resolution secondary ion mass spectrometry (NanoSIMS, Cameca, Gennevilliers, France) imaging corresponded well with the ICP-MS data, confirming a similar pattern and uniform distribution of 70Zn and Cd across the examined areas. Both applied techniques can be powerful tools for quantification (ICP-MS) and localisation and visualisation (NanoSIMS) of some ultra-trace isotopes in the intensively-dividing cells and fast-growing tissues of non-metalophytes even after short-term metal exposure. The results emphasise the importance of the quality of (agro)ecosystem resources (growing media, metal-contaminated soils/waters) in the public health risk, given that, even under low contamination and short-term exposure, some of the most toxic metallic ions (e.g., Cd) can relatively rapidly enter the human food chain.

The Role of 8-Amidoquinoline Derivatives as Fluorescent Probes for Zinc Ion Determination

“…Both studies showed that the micronutrient Zn and the toxic Cd were readily transported to the plants from the polluted soils [16,17]. Both metals have already translocated from the rhizosphere to edible hypocotyl radish and shoot tissues at a comparable pace, also under shortterm exposure [16]. These research types help comprehend plants' physiology and imply irrigation and biomonitoring of water and soil pollution.…”

“…The localization of Zn and Cd in Poplar species (Migeon and co-workers) and radish (Ondrasek and co-workers) grown in metal contaminated soil were analyzed by NanoSIMS. Both studies showed that the micronutrient Zn and the toxic Cd were readily transported to the plants from the polluted soils [16,17]. Both metals have already translocated from the rhizosphere to edible hypocotyl radish and shoot tissues at a comparable pace, also under shortterm exposure [16].…”

“…Secondary ion-MS (SIMS) is another analytical mass-spectrometry method used for imaging trace elements and their isotopes. As for high resolution-SIMS (NanoSIMS), it offers excellent sensing at 50 nm to a few microns [16]. The localization of Zn and Cd in Poplar species (Migeon and co-workers) and radish (Ondrasek and co-workers) grown in metal contaminated soil were analyzed by NanoSIMS.…”

Calcium modulates leaf cell-specific phosphorus allocation in Proteaceae from south-western Australia

“…After coating, samples were transferred under vacuum to a Zeiss field emission scanning electron microscope fitted with a Leica VCT100 cryotransfer and stage, and an Oxford X-Max80 SDD X-ray detector interfaced to Oxford Instruments AZtecEnergy software. This preparation method and this fully integrated Oxford analytical system are highly suitable for elemental analysis and quantitation of biological samples (Huang et al , 1994; Marshall and Xu, 1998; Marshall and Clode, 2009; McCully et al , 2010; Marshall et al , 2012; Jin et al , 2017; Marshall, 2017; Hayes et al , 2018; Ondrasek et al , 2019).…”

First Cryo-Scanning Electron Microscopy Images and X-Ray Microanalyses of Mucoromycotinian Fine Root Endophytes in Vascular Plants

“…All reported concentrations were total element concentration per kg wet weight, from fully hydrated root samples. This method of sample preparation and the fully integrated Oxford analytical system are highly suitable for elemental analysis and quantitation of biological samples (Huang et al, 1994;Marshall and Xu, 1998;Marshall and Clode, 2009;McCully et al, 2010;Marshall et al, 2012;Jin et al, 2017;Marshall, 2017;Hayes et al, 2018;Ondrasek et al, 2019). Due to the relatively low element concentrations in these plant materials, the element maps do not clearly visualize cellular differences across cellular regions, and thus are not included in the manuscript.…”