# Pith > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Pith > Markdown URL: https://mediated.wiki/source/Pith.md > Source: https://en.wikipedia.org/wiki/Pith > Source revision: 1344782066 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Plant tissue}} {{Use American English|date=November 2021}} {{Use mdy dates|date=November 2021}} {{for multi|the helmet used in tropical and subtropical climates|Pith helmet|the slaughtering technique|Pithing}} {{ref improve|date=December 2014}} [[Image:Elder pith.jpg|250px|right|thumb|[Elder](/source/Sambucus) shoot cut longitudinally to show the broad, solid pith (rough textured, white) inside the wood (smooth, yellow tinged). Scale in millimeters.]] [[Image:Walnut pith.jpg|250px|right|thumb|[Walnut](/source/Walnut) shoot cut longitudinally to show the chambered pith found in this genus. Scale in millimeters.]] '''Pith''', or '''medulla''', is a [tissue](/source/Tissue_(biology)) in the [stem](/source/Plant_stem)s of [vascular plant](/source/vascular_plant)s. Pith is composed of soft, spongy [parenchyma](/source/ground_tissue) cells, which in some cases can store [starch](/source/starch). In [eudicotyledon](/source/eudicotyledon)s, pith is located in the center of the stem. In [monocotyledon](/source/monocotyledon)s, it extends only into roots.{{cite book |title=Campbell Biology |isbn=978-0-135-18874-3 |page=770 |last1=Urry |first1=Lisa A. |last2=Cain |first2=Michael Lee |last3=Wasserman |first3=Steven Alexander |last4=Minorsky |first4=Peter V. |last5=Orr |first5=Rebecca B. |date=November 11, 2023 |publisher=Pearson }} The pith is encircled by a ring of [xylem](/source/xylem); the xylem, in turn, is encircled by a ring of [phloem](/source/phloem). While new pith growth is usually white or pale in color, as the tissue ages it commonly darkens to a deeper brown color. In [tree](/source/tree)s pith is generally present in young growth, but in the trunk and older branches the pith often gets replaced – in great part – by xylem. In some plants, the pith in the middle of the stem may dry out and disintegrate, resulting in a hollow stem. A few plants, such as [walnuts](/source/juglans), have distinctive chambered pith with numerous short cavities. The cells in the peripheral parts of the pith may, in some plants, develop to be different from cells in the rest of the pith. This layer of cells is then called ''the perimedullary region of the pithamus''. An example of this can be observed in ''Hedera helix'', a species of [ivy](/source/ivy). The term pith is also used to refer to the pale, spongy inner layer of the rind, more properly called [mesocarp](/source/mesocarp) or albedo, of [citrus](/source/citrus) fruits (such as oranges) and other [hesperidia](/source/hesperidium). The word comes from the [Old English](/source/Old_English) word ''piþa'', meaning substance, akin to [Middle Dutch](/source/Middle_Dutch) ''pitte'' (modern Dutch ''pit''), meaning the pit of a fruit.{{cite web |url=http://dictionary.reference.com/browse/pith |title=Pith |publisher=Random House, Inc |work=Dictionary.com Unabridged |access-date=20 January 2011 }} ==Uses== ===Food=== The pith of the [sago](/source/sago) palm, although highly toxic to animals in its raw form, is an important human food source in [Melanesia](/source/Melanesia) and [Micronesia](/source/Micronesia) by virtue of its starch content and its availability. There is a simple process of starch extraction from sago pith that leaches away a sufficient amount of the toxins and thus only the starch component is consumed. Current processes for starch extraction are generally only about 50% efficient, however, with the other half remaining in residual pith waste.{{cite book |last=Mishima |first=Takashi |date=2018 |editor-last1=Ehara |editor-first1=H. |editor-last2=Toyoda |editor-first2=Y. |editor-last3=Johnson |editor-first3=D. |title=Sago Palm |publisher=Springer |location=Singapore |pages=309–315 |chapter=New Sago Palm Starch Resources and Starch Pith Waste Properties |isbn=978-981-10-5268-2 |doi=10.1007/978-981-10-5269-9_23}} The form of the starch after processing is similar to [tapioca](/source/tapioca). Other foods sometimes mistakenly called piths include [heart of palm](/source/heart_of_palm) (actually the core of the bud) and [banana pith](/source/banana_pith)s (actually the rolled up young leaves). [[Image:Taxus wood.jpg|250px|right|thumb|The tiny central dark spot (diameter: about {{convert|1|mm|sp=us}}) in this [yew](/source/Taxaceae) [wood](/source/wood) is the pith.]] ===Pith helmets=== The spongy wood of the [pith wood plant](/source/Aeschynomene_aspera) or other similar species, often mistakenly called pith, was once used to make [pith helmet](/source/pith_helmet)s.[https://web.archive.org/web/20170729222808/https://en.oxforddictionaries.com/definition/pith_helmet AskOxford.com - Pith helmet]{{cite book |last1=Batello |first1=Caterina |last2=Marzot |first2=Marzio |last3=Touré |first3=Adamou Harouna |date=2004 |chapter=5. Farming Systems |chapter-url=http://www.fao.org/3/y5118e/y5118e05c.pdf |title=The Future is an Ancient Lake |url=http://www.fao.org/3/y5118e/y5118e00.htm |location=Rome |publisher=[Food and Agriculture Organization](/source/Food_and_Agriculture_Organization) Interdepartmental Working Group on Biological Diversity for Food and Agriculture |page=154 |isbn=92-5-105064-3}} ===Watch cleaning=== '''Pith wood''' is a [cleaning tool](/source/cleaning_tool) used in [watchmaking](/source/watchmaking) to clean watch parts{{Citation | last = Britten | first = Frederick James | title = The Watch & Clock Makers' Handbook, Dictionary and Guide | page = 144 | url = https://books.google.com/books?id=5SYJAAAAIAAJ | publisher = Spon | year = 1896 }}{{rp|144}} and tools. It is used to remove oil from the tips of tools to prevent the contamination of watch movements. A pith wood consists of a piece of pith (such as [elder](/source/Sambucus){{rp|281}} or [mullein](/source/Verbascum_thapsus){{Citation | last = Stelle| first = J. Parish | title = The American Watchmaker and Jeweler: A Full and Comprehensive Exposition of all the Latest and most Approved Secrets of the Trade Embracing Watch and Clock Cleaning and Repairing, Tempering in all its Grades, Making Tools, Compounding Metals, Soldering, Plating, Etc. | url = https://books.google.com/books?id=SKcyDwAAQBAJ | year = 2017 | publisher = Read Books | isbn = 9781473339408 }}). ===Light=== Dried pith (which is actually the center of the leaf) of certain [rush plant](/source/Juncaceae)s soaked in fat or grease, held using a [rushlight](/source/rushlight), was used as home lighting. Beginning in the 17th century, it would continue to be used in this method until the mid-20th century. It saw a brief revival during World War 2. == See also == * [Papyrus](/source/Papyrus) ==References== {{Reflist}} {{Wiktionary}} Category:Plant anatomy Category:Plant morphology Category:Plant physiology Category:By-products [ln:Libúbú](/source/ln%3ALib%C3%BAb%C3%BA) --- Adapted from the Wikipedia article [Pith](https://en.wikipedia.org/wiki/Pith) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Pith?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.