Origin of Silica Particles Found in the Cortex of Matteuccia Roots

A root sample from a species of fern ( Matteuccia ) was observed in detail under scanning electron microscopy (SEM), and some micron‐sized particles were observed in the cortex. Energy‐dispersive x‐ray spectroscopy (EDX) analysis of the particles indicated that they were almost pure silica. The concentrations of rare earth elements (REEs) in the silica particles from the roots, and silicate mineral particles from the soil, were analyzed by inductively coupled plasma–mass spectrometry (ICP‐MS). The REE composition of the silica particles from the roots was similar to that of the silicate mineral particles in the soil. The absence of a “Ce anomaly” in the REE patterns implies that the silica particles found in the cortex of Matteuccia roots were produced not by chemical deposition, but most likely by incorporation of silicate minerals into the root cortex and subsequent leaching of nutrient elements from the particles. This process is both a novel mechanism for plants to obtain nutrients and a means whereby plants accelerate the weathering of soil minerals.