Zinc hyperaccumulation in Cardamine waldsteinii from the Western Balkans: a field and synchrotron investigation

Abstract Background and aims Zinc hyperaccumulation is a very rare phenomenon on nature known from only 20 taxa around the World, especially in the genus Noccaea (Brassicaceae). Cardamine waldsteinii is a recently discovered (hyper)accumulator of zinc from central Europe and the Balkans. This study aimed to determine the ability of zinc hyperaccumulation in wild populations of C. waldsteinii and to elucidate its internal distribution in plant organs and tissues. Methods Plant and associated soils samples from the native habitat of C. waldsteinii in the Western Balkans were collected and analysed to determine Zn accumulation. This was coupled with synchrotron micro-X-ray fluorescence elemental imaging, to elucidate the distribution of zinc in the plant organs . Results The results confirm that C . waldsteinii is a genuine zinc hyperaccumulator meeting all established criteria for hyperaccumulation. The endodermis and vascular bundles were the main sites of zinc localisation in the roots and in the stem, whereas in the leaves the marginal areas were the most zinc enriched. Conclusions We confirm the hyperaccumulation properties of C . waldsteinii in wild populations, whilst synchrotron micro-X-ray fluorescence elemental imaging reveal the zinc localisation patterns in organs and tissues. This study highlights the need for a comprehensive study of the genus Cardamine with the aim of discovering new metal/metalloid hyperaccumulator species.