phytoliths

Phytoliths are microscopic bodies of inorganic silica that form within the cells of plants. They are composed mainly of hydrated silica (opal) and are produced when plants take up silicon from the soil as monosilicic acid, transporting and depositing it in various tissues during growth. After plant tissues decay, these silica bodies often persist in soils and sediments as phytoliths, sometimes for thousands of years.

Morphology and distribution vary by plant group and tissue. In grasses (Poaceae) phytoliths are especially diverse and include shapes such as bilobate, saddle, rondel, globular, and cross-like forms. Other plant families exhibit different tissue-specific morphologies. Because certain shapes are diagnostic to particular taxa or plant parts, phytoliths provide taxonomic and anatomical clues even when organic material has decayed.

Functions of phytoliths are not fully resolved, but they are thought to contribute to plant rigidity and protection, influence mechanical strength, and help defend against herbivory or environmental stress. Their durability means they can persist long after the plant has decayed, contributing to soil structure and biogeochemical records.

Significance in science includes their use in archaeology, paleoecology, and paleoagrarian studies. By identifying and counting phytoliths in soils and sediments, researchers infer past vegetation, land use, climate conditions, and the presence of cultivated grasses. They complement pollen data and isotopic analyses, offering insights into ancient environments and human-plant interactions.

Methods commonly involve extracting phytoliths from soil or sediment, followed by microscopic analysis (optical or scanning electron microscopy) and comparison with reference collections. Limitations include preservation biases, identification uncertainty, and uneven phytolith production among taxa.