Silicification is the process by which plants deposit silica within their tissues after absorbing silicon from the growing medium. Silicon is taken up by roots as monosilicic acid (H₄SiO₄) and is transported through the xylem. As water evaporates during transpiration, dissolved silicon becomes concentrated and is deposited as solid amorphous silica (SiO₂·nH₂O) within or between cells.
Silicification strengthens plant tissues and can improve resistance to mechanical stress, drought, salinity, and some pests and diseases. Silica deposits may occur in cell walls, beneath the cuticle, within specialized cells called silica cells, or in structures known as phytoliths. The extent of silicification varies greatly among species, with grasses, rice, bamboo, horsetails, and many sedges being particularly strong accumulators.
Unlike lignification, which involves the biological synthesis of lignin, silicification is largely a physical deposition process. The silica itself is not metabolically produced by the plant but is precipitated from absorbed silicon as water moves through and evaporates from plant tissues.
Silicification and lignification often complement one another, with both contributing to tissue strength, structural support, and defense against environmental stresses.
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