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For example, the stems of certain plants will collapse when grown in soil lacking silica.In many cases, phytoliths appear to lend structure and support to the plant, much like the spicules in sponges and leather corals.There is still debate in the scientific community as to why plants form phytoliths, and whether silica should be considered an essential nutrient for plants.Studies that have grown plants in silica-free environments have typically found that plants lacking silica in the environment do not grow well.These plants take up silica from the soil, whereupon it is deposited within different intracellular and extracellular structures of the plant. Although some use "phytolith" to refer to all mineral secretions by plants, it more commonly refers to siliceous plant remains.In contrast, mineralized calcium secretions in cacti are composed of calcium oxalates.
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According to Dolores Piperno, an expert in the field of phytolith analysis, there have been four important stages of phytolith research throughout history.
First, soluble silica, also called monosilicic acid, is taken up from the soil when plant roots absorb groundwater.
Because they are made of the inorganic substances silica or calcium oxalate, phytoliths don't decay with the rest of the plant 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.
Finally, calcium oxalates serve as a reserve of carbon dioxide.