What are phytoliths?
Phytoliths are microscopic silica bodies that precipitate in and around cells in many plants. When plant tissues decompose, the silica is deposited in the soil, forming a record of past vegetation. Phytoliths are known from sediments as old as
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the Cretaceous, and have been recovered from many different types of sediment (e.g., claystone to fine sandstone, diatomite) and facies (limnic, fluvial, aeolian). Unlike macrofossils and pollen, they can often be preserved in well-oxidized sediments along with vertebrate fossils, allowing direct comparisons between plant and animal data (e.g., Strömberg et al. 2007).


Plants deposit silica in their tissues to a varying

Schematic drawing of short cell phytoliths in anatomical position in the grass epidermis and isolated in soil after plant decomposition. Photo of conical rondel short cell for comparison.

degree; some form almost none and other are extremely silica-rich, for example horsetails, palms, and grasses. Phytoliths are also variable in how taxonomically sensitive they are. For example, phytoliths of angiosperm trees are commonly distinctive at the family level at best, whereas certain grass phytoliths (so-called silica short cells) tend to be highly diagnostic (e.g., to the level of genus) (Piperno 2006). As a result of this variability in silica production and distinctiveness, phytoliths generally cannot be used to generate a detailed floral list. However, analysis of phytolith assemblages in soils has shown to be excellent tools for reconstructing overall vegetation type (e.g., forest vs. grassland) (Piperno 2006). In addition, silica short cells can be used to document taxonomic and ecological evolution within the grass family (Poaceae) (Prasad et al. 2005, Strömberg 2005).


 

Phytoliths from modern plants (Strömberg 2003). a. Silicified stomata and epidermis from horsetail (Equisetum). b. Silicified tracheary element from Liquidambar. c. Cross short cell  phytolith from Olyra. Scale bar = 10 micrometers.

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bPhytoliths_files/Tra-2.jpg
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