Manganese Hyperaccumulation in the Genus Ilex : Discovery of New Hyperaccumulator Species and Elemental Accumulation Patterns

ABSTRACT Manganese (Mn) hyperaccumulator plants are rare in nature but provide important insights into plant–soil interactions, Mn nutritional physiology, and biogeochemical cycling. X‐ray fluorescence (XRF) herbarium analysis of Japanese wild plants was used to investigate Mn concentrations in 25 different Ilex species (totaling 619 specimens). Among the 25 analyzed Ilex species, nine species had leaves containing > 10,000 mg kg −1 Mn (dry weight), and in six of these species, multiple hyperaccumulator‐level specimens were found, representing 8%–21% of the specimens within those six species. Analysis of Mn and six other essential elements (K, Ca, P, S, Fe, and Zn) revealed that Ilex had, on average, four times higher Zn concentrations than those in most other plants, with a significant positive correlation between Mn and Zn. No other elements showed significant correlations with Mn. In contrast to other Mn hyperaccumulators, including Chengiopanax sciadophylloides from Japan, no positive Mn–Ca correlation was observed. These findings identify Ilex as the second Mn hyperaccumulator group reported from Japan and show that, like C. sciadophylloides , hyperaccumulation in Ilex was achieved under ordinary forest soils without known contamination sources (noncontaminated soil). The distinct accumulation pattern observed here in the genus Ilex suggests a physiological mechanism different from the Mn‐Ca co‐accumulation observed in other Mn hyperaccumulators.