Elemental composition of phytoliths in modern plants (Ericaceae)

Plants accumulate opaline silica in the form of phytoliths. Species and availability of Si are the main factors that determine the phytolith content in plants. Therefore, several Ericaceae species were tested in different soils. Erica andevalensis is restricted to grow in acid- and metal-enriched soils in the Iberian Pyritic Belt, and therefore it is particularly suitable to study the effects of metals on the phytolith composition. Ericaceae that originate from soils in mining areas were compared with those from unpolluted areas. Species from mining areas included E. andevalensis (Riotinto mines, Andalucia, SW Spain), Erica australis and Calluna vulgaris (Touro mine Galicia, NW Spain). For the unpolluted areas, C. vulgaris was collected on peat (Sapric Histosol), quartzite (Albic Podsol) and serpentinite (Mollic Gleysol) soils. The abundance and elemental composition (Ca, Mg, Al, Fe, Mn, Cu, Zn, Cr, Ni, Pb and As) of phytoliths in leaves were analyzed. Elemental quantification by means of Energy-dispersive Miniprobe Multielement Analyzer (EMMA-XRF) is an innovative method for elemental analysis of phytoliths. Both the highest leaf phytolith production and elemental concentration were found in species from mine soils, with the highest phytolith contents for C vulgaris and highest concentration of elements (Ca, Fe, Mn, Cu, Zn, Pb and As) for E. andevalensis. The highest Cr and Ni concentration in phytoliths was found on serpentinite soils. The lowest values of phytoliths and metal concentrations were found in heathers from quartzite and peaty soils. The abundance of phytoliths agreed with the availability of Si in the studied soils and its elemental composition reflected the geochemical conditions. The results presented here suggest that phytoliths act as alleviates of metal stress in heathers. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.