Tools for the discovery of hyperaccumulator plant species in the field and in the herbarium

Globally, the discovery of metal and metalloid hyperaccumulator plants has been hindered by systematic screening of plant species and is highly biased towards Ni hyperaccumulators due to the existence of a paper test that is only specific to Ni (based on dimethylglyoxime reagent). Consequently, more than 500 of the approximately 700 known hyperaccumulators species accumulate Ni. New technological advances now permit massive screening of herbarium specimens using non-destructive multi-element sensitive portable X-Ray Fluorescence Spectroscopy (pXRF) instead of via destructive techniques such as Atomic Absorption Spectrophotometry (AAS) or Inductively-coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). This approach has already led to the discovery of numerous hyperaccumulator species for various elements new to science. This chapter introduces established and novel tools that can be used for discovering hyperaccumulator plant species in the field and in the herbarium.