The modern conversation about lead hyperaccumulation begins with a Brassicaceae from the European Alps. In their survey of European Thlaspi species as geochemical indicators, Reeves & Brooks (1983) reported that Thlaspi rotundifolium — now Noccaea rotundifolia — growing on mineralised alpine screes could reach foliar lead concentrations around 8,200 µg g⁻¹ dry weight. That value is more than eight times the hyperaccumulation threshold and remains one of the highest validated shoot-lead records in the literature.
Why the record matters
Most plants exposed to lead-rich soils store the metal in roots, or fail to exclude it at all. Noccaea rotundifolia appears to translocate lead into above-ground tissue, making it one of the very few species for which a credible foliar lead hyperaccumulation claim can be made. The plant’s association with lead–zinc mineralised screes in the European Alps means it evolved, or at least persists, under severe selective pressure for both tolerance and upward transport.
The caveat that will not go away
Lead’s chemistry makes verification hard. Fine soil particles can adhere to leaves, inflating apparent foliar concentrations unless samples are rigorously washed. The original collections were from rugged alpine sites, where grit and dust are unavoidable. For this reason the hyperaccumulate entry for Noccaea rotundifolia carries a “hypothesized” verification flag and a note that lead records should be treated cautiously.
What it means for the field
Even with the caveat, Noccaea rotundifolia shaped expectations. It showed that foliar lead hyperaccumulation is physiologically possible, set the benchmark against which later claims are judged, and focused attention on the Brassicaceae as a family where lead tolerance repeatedly evolves. Later work on Noccaea rotundifolia subsp. cepaeifolia has reported similarly high foliar lead, but the broader lesson is unchanged: a lead hyperaccumulator claim requires unusually careful proof.
This analysis is grounded in the cited primary source. Verification standards follow the hyperaccumulate methodology.