Visible cellular distribution of cadmium and zinc in the hyperaccumulator Arabidopsis halleri ssp. gemmifera determined by 2-D X-ray fluorescence imaging using high-energy synchrotron radiation
The striking sub-cellular distribution of cadmium (Cd) and zinc (Zn) in the Cd and Zn hyperaccumulator Arabidopsis halleri ssp. gemmifera was revealed by microbeam X-ray microfluorescence analysis (μ-XRF) using high-energy synchrotron radiation. Plants were grown in hydroponics with various Cd and Zn concentrations. The concentration of Cd in the aerial portions of plants increased with increasing Zn exposure and the transportation efficiency of Cd from the root to the shoot was affected by both Cd and Zn concentrations in the nutrient solution. The μ-XRF imaging clearly showed that Cd and Zn were preferentially accumulated in trichomes on the leaf, while the distribution of Cd in the leaf were changed by Zn treatment. It was observed that Cd treated with higher Zn concentration (20 μM Cd + 100 μM Zn) was distributed in the mesophyll tissue at high concentrations. In addition, μ-XRF imaging clarified that the distribution of Zn inside the leaf was different from that of Cd at a cellular level. Zn was primarily distributed in the mesophyll tissue of the leaf blade. In contrast, Cd was localized to the vascular bundle of the main vein. That is, Zn was transported to mesophyll tissue from vascular bundle more and efficiently than Cd. As seen above, it was able to study a difference of the distribution of Cd and Zn, which are congeners and behave similarly, inside plant body at the cellular level in detail by high-energy μ-XRF.
- This article is part of the themed collection: Phytometallomics