A phytolith ("Plant stone") is a rigid microscopic body that occurs in many plants. The most common type of phytolith is the silicon phytolith, also called opal phytolith. Silicon phytoliths vary in size and shape depending on the plant taxon and plant part (stem, leaf, root) in which they (naturally) occur. Grasses, including rice, wild rice, maize, wheat, and other various grains); crop plants such as beans, squashes, gourds, manioc, canna, and arrowroot; palms; as well as numerous tree species are just some of the plants which contain phytoliths. Calcium oxalate phytoliths are another common type, occurring in the stems of cacti and baobabs. Phytoliths are mentioned in the writings of Charles Darwin.
FunctionThese objects serve a variety of purposes. In many cases, they appear to lend the plant structure and support, much like the spicules in sponges and leather corals. Others serve to make plants distasteful, lending the plant's tissues a grainy or prickly texture. Finally, calcium oxalate phytoliths serve as a reserve of carbon dioxide. Cacti use these as a reserve for photosynthesis during the day when they close their pores to avoid water loss, while baobabs use this property to make their trunks more flame-resistant.
ArchaeologyPhytoliths are very robust in nature, and are useful in archaeology, since they can be used to reconstruct the plants present at a site or an area within a site even though the rest of the plant parts have been burned up or dissolved. Because they are made of the inorganic substances silica or calcium oxalate, phytoliths don't decay when the rest of the plant decays over time and can survive in conditions that would destroy organic residues. Phytoliths can provide evidence of both economically important plants and those that are indicative of the environment at a particular time period.
Phytoliths may be extracted from residue on many sources: dental calculus (buildup on teeth); food preparation tools like rocks, grinders, and scrapers; cooking or storage containers; ritual offerings; and garden areas.
PalaeontologyPhytoliths are abundant in the fossil record, and have been reported from the late Devonian onwards.
Japanese and Korean archaeologists refer to grass and crop plant phytoliths as 'plant opal' in archaeological literature.
Carbon sequestrationRecent work in 2007 has shown that carbon can be accumulated in many phytoliths, and as such could provide a long term option to sequester carbon in soil in the plant residual silicon.
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- Darwin, C. R. 1846. "An Account of the Fine Dust Which Often Falls on Vessels in the Atlantic Ocean," Quarterly Journal of the Geological Society of London 2 (Read 4 June 1845): 26-30. (http://darwin-online.org.uk/content/frameset?itemID=F1672&viewtype=text&pageseq=3).
- Ecological significance of phytoliths
- Background from St. Cloud laboratory
- Association of Environmental Archaeology
- Steve Archer, "About Phytoliths": http://research.history.org/Archaeological_Research/Collections/CollArchaeoBot/PhytoFAQs.cfm .
- Terry B. Ball, "Phytolith Literature Review": http://www.ou.edu/cas/botany-micro/ben/ben282.html .
- Dr. Sanjay Eksambekar's 'Phytolith Research Institute': http://www.phytolithresearch.com
- Deborah Pearsall's MU Phytolith Database ,http://web.missouri.edu/~umcasphyto/index.shtml
- "What are Phytoliths?" Sandstone Archaeology Paleoethnobotany Laboratory http://www.sandstonearchaeology.com/paleoethnobotany.html
phytolith in Catalan: Fitòlit
phytolith in Spanish: Fitolito
phytolith in French: Phytolithe
phytolith in Japanese: プラント・オパール
phytolith in Swedish: Fytolit