Editing Tannin (section)

== Occurrence ==
Tannins are distributed in species throughout the [[plant kingdom]]. They are commonly found in both [[gymnosperm]]s and [[angiosperm]]s. Mole (1993) studied the distribution of tannin in 180 families of [[dicotyledon]]s and 44 families of [[monocotyledon]]s (Cronquist). Most families of dicot contain tannin-free species (tested by their ability to precipitate proteins). The best known families of which all species tested contain tannin are: [[Aceraceae]], [[Actinidiaceae]], [[Anacardiaceae]], [[Bixaceae]], [[Burseraceae]], [[Combretaceae]], [[Dipterocarpaceae]], [[Ericaceae]], [[Grossulariaceae]], [[Myricaceae]] for dicot and [[Najadaceae]] and [[Typhaceae]] in Monocot. To the family of the oak, [[Fagaceae]], 73% of the species tested contain tannin. For those of acacias, [[Mimosaceae]], only 39% of the species tested contain tannin, among [[Solanaceae]] rate drops to 6% and 4% for the [[Asteraceae]]. Some families like the [[Boraginaceae]], [[Cucurbitaceae]], [[Papaveraceae]] contain no tannin-rich species.<ref>{{cite journal |author=Simon Mole |title=The Systematic Distribution of Tannins in the Leaves of Angiosperms: A Tool for Ecological Studies |journal=Biochemical Systematics and Ecology |volume=21 |issue=8 |pages=833–846 |year=1993|doi=10.1016/0305-1978(93)90096-A|bibcode=1993BioSE..21..833M }}</ref>

The most abundant polyphenols are the [[condensed tannin]]s, found in virtually all families of plants, and comprising up to 50% of the dry weight of leaves.<ref>{{cite journal |title=Les tannins dans les bois tropicaux |language=fr |last=Doat |first=J. |journal=Bois et Forêts des Tropiques |year=1978 |volume=182 |pages=34–37 |doi=10.19182/bft1978.182.a19337 |doi-access=free |url=http://agritrop.cirad.fr/444167/1/document_444167.pdf }}</ref><ref>{{cite book |last1=Kadam |first1=S. S. |last2=Salunkhe|first2=D. K. |last3=Chavan|first3=J. K. |title=Dietary tannins: consequences and remedies |publisher=CRC Press |location=Boca Raton |year=1990 |page=177 |isbn=978-0-8493-6811-0 }}</ref>

===Cellular localization===
{{more references |section |date=September 2021}}
In all vascular plants studied, tannins are manufactured by a [[chloroplast]]-derived [[organelle]], the [[tannosome]].<ref>{{cite journal |doi=10.1093/aob/mct168 |volume=112 |title=The tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta |year=2013 |journal=Annals of Botany |pages=1003–1014 |last1=Brillouet |first1=J.-M. |issue=6 |pmid=24026439 |pmc=3783233}}</ref> Tannins are mainly physically located in the [[vacuole]]s or surface wax of plants. These storage sites keep tannins active against plant predators, but also keep some tannins from affecting plant metabolism while the plant tissue is alive.

Tannins are classified as [[ergastic substance]]s, i.e., non-protoplasm materials found in cells. Tannins, by definition, precipitate proteins. In this condition, they must be stored in organelles able to withstand the protein precipitation process. [[Idioblast]]s are isolated plant cells which differ from neighboring tissues and contain non-living substances. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin or pigments etc. They also can contain tannins. In Japanese persimmon (''[[Diospyros kaki]]'') fruits, tannin is accumulated in the vacuole of tannin cells, which are idioblasts of parenchyma cells in the flesh.<ref>{{cite journal |last1=Kanzaki |first1=Shinya |last2=Yonemori |first2=Keizo |last3=Sugiura |first3=Akira |last4=Sato |first4=Akihiko |last5=Yamada |first5=Masahiko |year=2001  |title=Identification of Molecular Markers Linked to the Trait of Natural Astringency Loss of Japanese Persimmon (''Diospyros kaki'') Fruit |journal=Journal of the American Society for Horticultural Science |volume=126 |issue=1 |pages=51–55 |doi=10.21273/JASHS.126.1.51 |url=http://journal.ashspublications.org/content/126/1/51.full.pdf+html |archive-url=https://web.archive.org/web/20150904065618/http://journal.ashspublications.org/content/126/1/51.full.pdf+html |archive-date=4 September 2015|doi-access=free }})</ref>

=== Presence in soils ===
{{see also|Soil pH}}
The [[convergent evolution]] of tannin-rich plant communities has occurred on nutrient-poor acidic soils throughout the world. Tannins were once believed to function as anti-herbivore defenses, but more and more ecologists now recognize them as important controllers of decomposition and nitrogen cycling processes. As concern grows about global warming, there is great interest to better understand the role of polyphenols as regulators of carbon cycling, in particular in northern boreal forests.<ref>{{cite journal|pmid=10802549|year=2000|last1=Hättenschwiler|first1=S.|title=The role of polyphenols in terrestrial ecosystem nutrient cycling|journal=Trends in Ecology & Evolution|volume=15|issue=6|pages=238–243|last2=Vitousek|first2=PM|doi=10.1016/S0169-5347(00)01861-9|doi-access=free}}</ref>

[[Leaf litter]] and other decaying parts of kauri (''[[Agathis australis]]''), a tree species found in New Zealand, decompose much more slowly than those of most other species. Besides its acidity, the plant also bears substances such as waxes and phenols, most notably tannins, that are harmful to [[microorganism]]s.<ref>{{cite journal | last1 = Verkaik | first1 = Eric | last2 = Jongkindet | first2 = Anne G. | last3 = Berendse | first3 = Frank | year = 2006 | title = Short-term and long-term effects of tannins on nitrogen mineralisation and litter decomposition in kauri (''Agathis australis'' (D. Don) Lindl.) forests | journal = Plant and Soil | volume = 287 | issue = 1–2| pages = 337–345 | doi = 10.1007/s11104-006-9081-8 | bibcode = 2006PlSoi.287..337V | s2cid = 23420808 }}</ref>

=== Presence in water and wood ===
The [[Leaching (chemistry)|leaching]] of highly [[water]] [[Solubility|soluble]] tannins from decaying vegetation and leaves along a stream may produce what is known as a [[blackwater river]]. Water flowing out of [[bog]]s has a characteristic brown color from dissolved [[peat]] tannins. The presence of tannins (or [[humic acid]]) in [[Water well|well water]] can make it smell bad or taste bitter, but this does not make it unsafe to drink.<ref>{{Cite web|url=http://www.gov.ns.ca/nse/water/docs/droponwaterFAQ_HumicSubstances.pdf|archive-url=https://web.archive.org/web/20130517071315/http://www.gov.ns.ca/nse/water/docs/droponwaterFAQ_HumicSubstances.pdf|url-status=dead|title=Tannins, lignins and humic acids in well water on www.gov.ns.ca|archive-date=17 May 2013}}</ref>

Tannins leaching from an unprepared driftwood decoration in an aquarium can cause pH lowering and coloring of the water to a tea-like tinge. A way to avoid this is to boil the [[wood]] in water several times, discarding the water each time. Using peat as an [[Substrate (aquarium)|aquarium substrate]] can have the same effect. Many hours of boiling the driftwood may need to be followed by many weeks or months of constant soaking and many water changes before the water will stay clear. Raising the water's [[pH level]], e.g. by adding [[Sodium bicarbonate|baking soda]], will accelerate the process of leaching.<ref>[http://www.aqualifesupport.com/getArticle.php?ArtID=413 Preparing Driftwood for Your Freshwater Aquarium] {{webarchive|url=https://web.archive.org/web/20110707154303/http://www.aqualifesupport.com/getArticle.php?ArtID=413 |date=7 July 2011 }}</ref>

Tannins in water can lead to feather staining on wild and domestic [[Anseriformes|waterfowl]] which frequent the water; [[mute swan]]s, which are typically white in colour, can often be observed with reddish-brown staining as a result of coming into contact with dissolved tannins, though dissolved [[iron]] compounds also play a role.<ref>{{Cite web |date=2017-08-23 |title=Mute Swan {{!}} Bird Identification Guide {{!}} Bird Spot |url=https://www.birdspot.co.uk/bird-identification/mute-swan |access-date=2024-12-29 |language=en-GB}}</ref>

[[Softwood]]s, while in general much lower in tannins than hardwoods,<ref>{{cite journal|title=Polyflavonoid tannins ? a main cause of soft-rot failure in CCA-treated timber|first1=A.|last1=Pizzi|first2=W. E.|last2=Conradie|first3=A.|last3=Jansen|date=28 October 1986|journal=Wood Science and Technology|volume=20|issue=1|pages=71–81|doi=10.1007/BF00350695|s2cid=21250123}}</ref> are usually not recommended for use in an aquarium<ref>{{Cite web|url=https://www.petfish.net/kb/entry/194|archive-url=https://web.archive.org/web/20110724003958/http://www.petfish.net/kb/entry/194/|url-status=dead|title=Driftwood Do's & Don'ts – Pet Fish|archive-date=24 July 2011}}</ref> so using a [[hardwood]] with a very light color, indicating a low tannin [[Concentration|content]], can be an easy way to avoid tannins. Tannic [[acid]] is brown in color, so in general white woods have a low tannin content. Woods with a lot of yellow, red, or brown coloration to them (like cedar, redwood, red oak, etc.) tend to contain a lot of tannin.<ref>{{Cite web|url=http://www.houserepairtalk.com/f45/carpet-hardwood-floor-8686/|archive-url=https://web.archive.org/web/20110417042435/http://www.houserepairtalk.com/f45/carpet-hardwood-floor-8686/|url-status=dead|title=Tannin and hardwood flooring|archive-date=17 April 2011}}</ref>

{{Gallery
|align=center
|File:Tannin rich fresh water draining into Cox Bight from Freney Lagoon.jpg|Tannin-rich fresh water draining into Cox Bight from Freney Lagoon, Southwest Conservation Area, Tasmania, Australia
|File:Bogwood Betta.jpg|[[Bog-wood]] (similar to, but not, [[driftwood]]) in an [[aquarium]], turning the [[water]] a tea-like brown
|File:Tête de cygne sur les étangs de Brimeux en vallée de Canche Marais de Marenla 3 aout 2017a 02.jpg|A [[mute swan]] with reddish-brown staining on the top of its head, caused by exposure to dissolved tannins and [[iron]] compounds in water
|File:Upper Tahquamenon falls Panoramic view.jpg|Upper Tahquamenon falls Panoramic view
|File:TWC Ōpārara • Nimmo • MRD 13.jpg|The tannin-rich [[Oparara River]] in the West Coast region of New Zealand|title=}}