Synchrotron XRF imaging reveals elemental distribution in the nickel hyperaccumulator Odontarrhena muralis (Brassicaceae) from Serbia

Odontarrhena muralis (Brassicaceae) is a nickel hyperaccumulator species from the Balkans used as a "metal crop" in nickel phytomining. This study aimed to determine the elemental distribution, focusing on nickel, in fresh-hydrated plant tissue (stems, leaves and inflorescences), to clarify where nickel is localized at the tissue and cellular scale-level and to infer the physiological response to its hypertolerance and hyperaccumulation. For the analysis, intact plant organs of O. muralis were subjected to elemental imaging using synchrotron-based micro-X-ray fluorescence (mu XRF). The predominant distribution of nickel occurs in the epidermal tissue and at the base of the trichomes, which are also the main sinks for calcium deposition. The obtained results represent a further contribution to the knowledge of the physiological characteristics of this hyperaccumulating "metal crop" species and, consequently, to its application in sustainable metal extraction using phytomining.