When plants die and decompose, or are burnt, phytoliths are released directly into the soil. Where, being hard and resistant to destruction. They can be preserved for thousands of years. Because phytoliths tend to take on the shape of living cells, they can be differentiated. Allowing for identification of taxa, sometimes to genus level.

Analysis is a micro-botanical technique
It is mostly used in archaeology to study ancient plant remains. The opaline silica bodies form. During the lifetime of the different plants, and between certain cells. These micro-remains can provide insight into ancient diet. The non-food uses of plants (such as for fuel or weaving). Plant spatial arrangements. Agricultural practices. And, seasonality of site occupations. The durability of these micro-remains makes them particularly interesting and valuable.

Why plants form phytoliths?
Phytoliths strengthen the plant against abiotic stressors. Salt runoff, metal toxicity, extreme temperatures and more. Phytoliths can also protect the plant against biotic threats like insects and fungal diseases. There rigid silica structures make the plants more difficult to consume and digest by certain predators. Even humans. In many cases though, phytoliths appear to lend support and structure to a plant. Kinda like spicules in sponges and leather in ocean corals. Finally, different plants can use the calcium and other minerals in photosynthesis. Like cactus during the day. To close its pores and avoid water loss.

Problems with phytolith analysis of remains

1. Multiplicity: different parts of a single plant may produce different phytoliths;
2. Redundancy: different plants can produce the same kind of phytolith; and
3. Some plants produce large numbers of phytoliths while others produce only few.

History of phytolith research
Scientists have developed a time table for phytoliths, and its research and development

1. 1835 to 1895: Discovery and exploratory stage. The first report on phytoliths was published by a German botanist named Struve in 1835. During this time another German scientist named Christian Gottfried Ehrenberg was one of the leaders in the field of phytolith analysis. He developed the first classification system for phytoliths, and analyzed soil samples that were sent to him from all around the world. Most notably, Ehrenberg recorded phytoliths in samples he received from the famous naturalist, Charles Darwin, who had collected the dust from the sails of his ship, HMS Beagle, off the coast of the Cape Verde Islands.
2. 1895 to 1936: Botanical phase of research. Phytolith structures in plants gained wide recognition and attention throughout Europe. Research on production, taxonomy and morphology exploded. Detailed notes and drawings on plant families that produce silica structures and morphology within families were published.
3. 1955 to 1975: Period of ecological research. Classification systems for differentiation within plant families became popular.
4. 1978 to now: Modern period of archaeological and paleoenvironmental research. Archaeobotanists in the Americas first consider and analyze phytolith assemblages. In order to track prehistoric plant use and domestication. Also for the first time, phytolith data from pottery are used to track clay making history and pottery manufacture. Data was used to reconstruct some vegitation. As a much larger reference collection on phytolith morphology has now been assembled.

Prehistoric diets
Plant stones provide evidence of both economically important plants, and those that are of a particular time period. They can be extracted from residue from things like: buildup on teeth; food preparation tools like rocks, grinders, and scrapers; cooking or storage containers; ritual offerings; and garden areas.

Contribution to archaeobotanical knowledge
Using phytolith remains on ceramics and pottery from the southwest and Mexico has provided modern linages of corn. It typically has been useful in tropical regions because other forms of plant remains are usually not well preserved. Research in Boliva has indicated maize may have been present in the lake Titicaca region (map) earlier than thought. Currently, this is believed at a number of sites on the south American continent. Could there have been an early corn trade route? What did you think.

Plant stone analysis has provided insightful evidence for other early (and, neolithic link) crops like rice; and cucubrbita (squash and gord). In areas like SE asia ; and, Ecuador .

Due to their durability and stability, phytoliths have become important tools for researchers studying plant evolution, past climates, human agricultural practices, and environmental changes throughout history. They are often extracted from soils, sediments, or plant remains and examined under a microscope for identification and analysis. Making them valuable in paleoenvironmental and archaeological studies. Including insightfulness for the pleistocene and neolithic time period(s). Check them out with some more neolithic architecture today.

Bibliography:

Tsartsidou, Georgia; Lev-Yadun, Simcha; Albert, Rosa-Maria; Miller-Rosen, Arlene; Efstratiou, Nikos; Weiner, Steve (2007). “Thephytolith archaeological record: strengths and weaknesses evaluated based on a quantitative modern reference collection from Greece”. Journal of Archaeological Science. 34 (8): 1262–1275. doi:10.1016/j.jas.2006.10.017 (https://doi.org/10.1016%2Fj.jas.2006.10.017). ISSN 0305-4403 (https://www.worldcat.org/issn/0305-4403

Rajendiran et al., (2012).Role of phytolith occluded carbon of crop plants for enhancing soil carbon sequestration in agro-ecosystems. Current Science, 103(8), 911-920.

Epstein, Emanuel (1999). “Silicon”. Annual Review of Plant Physiology and Plant Molecular Biology. Annual Reviews. 50 (1): 641–664. doi:10.1146/annurev.arplant.50.1.641 (https://doi.org/10.1 146%2Fannurev.arplant.50.1.641). ISSN 1040-2519 (https://www.worldcat.org/issn/1040-2519). PMID 15012222 (https://pubmed.ncbi.nlm.nih.gov/15012222).

Piperno, Dolores R. (2006). Phytoliths: A Comprehensive Guide for Archaeologists and Paleoecologists. AltaMira Press ISBN 0759103852.