Bark 170396 224258384 2008-07-08T01:06:11Z Senator Palpatine 7357381 Reverted edits by [[Special:Contributions/65.26.224.229|65.26.224.229]] to last version by Paleorthid (using [[WP:HG|Huggle]]) {{otheruses}} [[Image:Japanese Maple Bark by David Shankbone.jpg|thumb|[[Japanese Maple]] bark.]] [[Image:Pine bark tecpan guatemala.JPG|thumb|Bark of a Pine tree in Tecpan, Guatemala.]] '''Bark''', also known as periderm, is the outermost layer of [[Plant stem|stems]] and [[root]]s of [[woody plant]]s such as [[tree]]s. It overlays the [[wood]] and consists of three layers, the [[Cork (tissue)|cork]], the [[phloem]] and the [[vascular cambium]]. Products used by people that are derived from bark include: [[spice]]s and other flavorings, tannin, resin, [[latex]], medicines, poisons, various hallucinatory chemicals and cork. Bark has been used to make cloths, canoes, ropes and used as a surface for paintings and map making;<ref>Taylor, Luke. 1996. ''Seeing the inside bark painting in western Arnhem Land. Oxford studies in social and cultural anthropology''. Oxford: Clarendon Press.</ref> A number of plants are also grown for their attractive or interesting bark colorations and surface textures.<ref>Sandved, Kjell Bloch, Ghillean T. Prance, and Anne E. Prance. 1993. ''Bark the formation, characteristics, and uses of bark around the world''. Portland, Or: Timber Press.</ref><ref>Vaucher, Hugues, and James E. Eckenwalder. 2003. ''Tree bark a color guide''. Portland: Timber</ref> ==Botanic description== * '''Cork''' - an external, secondary tissue impermeable to water and gases. * '''Cork cambium''' - A layer of [[cell (biology)|cells]], normally one or two cell layers thick that is in a persistent [[meristematic]] state that produces cork. * '''Phelloderm''' - (not always present) A layer of cells formed in some plants from the inner cells of the cork cambium (Cork is produced from the outer layer). * '''Cortex''' - The primary tissue of [[Plant stem|stem]]s and roots. In stems the cortex is between the epidermis layer and the phloem, in roots the inner layer is not phloem but the [[pericycle]]. * '''Phloem''' - [[nutrient]] conducting tissue composed of sieve tube or sieve cells mixed with [[parenchyma]] and fibers. In old stems the epidermal layer, cortex, and primary phloem become separated from the inner tissues by thicker formations of cork. Due to the thickening cork layer these cells die because they do not receive water and nutrients. This dead layer is the rough corky bark that forms around tree trunks and other stems. In smaller stems and on typically non woody plants, sometimes a secondary covering forms called the [[periderm]], which is made up of cork cambian, cork and phelloderm. It replaces the dermal layer and acts as a covering much like the corky bark, it too is made up of mostly dead tissue. The skin on the potato is a periderm. Definitions of the term can vary. In another usage, bark consists of the dead and protective tissue found on the outside of a woody stem, and does not include the vascular tissue. <!-- http://www.caf.wvu.edu/Bark/whatis.htm and many others, some further writing up needed --> The [[Vascular tissue|vascular]] cambium is the only part of a woody stem where [[cell division]] occurs. It contains undifferentiated cells that divide rapidly to produce secondary [[xylem]] to the inside and secondary [[phloem]] to the outside. Along with the [[xylem]], the phloem is one of the two tissues inside a plant that are involved with fluid transport. The phloem transports organic molecules (particularly [[sugar#Chemistry|sugars]]) to wherever they are needed. ==Uses== Cork, sometimes confused with bark in colloquial speech, is the outermost layer of a woody stem, derived from the [[cork cambium]]. It serves as protection against damage, [[parasite]]s and [[disease]]s, as well as dehydration and extreme temperatures. Cork can contain [[antiseptic]]s like [[tannin]]s. Some cork is substantially thicker, providing further insulation and giving the bark a characteristic structure, in some cases thick enough to be harvestable as [[cork (material)|cork product]] without killing the tree. Bark has been used a covering in the making of canoes, the most famous example of this is the birch canoes of North America.<ref>Adney, Tappan, and Howard Irving Chapelle. 1964.'' The bark canoes and skin boats of North America''. Washington: Smithsonian Institution.</ref> The bark of some trees is edible. Among the commercial products made from bark are [[cork (material)|cork]], [[cinnamon]], [[quinine]]<ref>Duran-Reynals, Marie Louise de Ayala. 1946. ''The fever bark tree; the pageant of quinine''. Garden City, N.Y.: Doubleday.</ref> (from the bark of [[Cinchona]])<ref>Markham, Clements R. 1880. ''Peruvian bark. A popular account of the introduction of chinchona cultivation into British India''. London: J. Murray.</ref> and [[aspirin]] (from the bark of [[willow]] trees). The bark of some trees notably oak (''Quercus robur'') is a source of tannic acid, which is used in [[tanning]]. Bark chips generated as a [[by-product]] of [[lumber]] production, are often used in bark [[mulch]] in western [[North America]]. Bark is important to the horticultural industry since in shredded form it is used for plants that do not thrive in ordinary soil, such as [[epiphyte]]s. [http://www1.eere.energy.gov/biomass/fy04/wood_adhesives.pdf Wood Adhesives from Bark-Derived Phenols:] Wood Bark has [[lignin]] content and when it is pyrolyzed (subjected to high temperatures in the absence of oxygen), it yields a liquid [[bio-oil]] product rich in natural phenol derivatives. The phenol derivatives are isolated and recovered for application as a replacement for fossil-based [[phenols]] in phenol-formaldehyde (PF) resins used in [[Oriented Strand Board]] (OSB) and plywood. ==Bark removal== Cut logs used for the production of [[lumber]] or even log cabins generally have the bark removed, either just before cutting or for curing. Such logs and even trunks and branches found in their natural state of decay in forests, where the bark has fallen off, are said to be '''decorticated'''. A number of living organisms live in or on bark, including insects,<ref>Lieutier, François. 2004. ''Bark and wood boring insects in living trees in Europe a synthesis''. Dordrecht: Kluwer Academic Publishers.</ref> fungi and other plants like mosses , algae and other vascular plants. Many of these organisms are pathogens or parasites but some also have symbiotic relationships. == Bark repair == [[Image:Ash callus growth.JPG|right|thumb|<Center>Extensive callus growth on a young Ash tree.]] [[Image:Alder bark and callus.JPG|thumb|left|<Center>Alder bark (Alnus glutinosa) with characteristic lenticels and abnormal lenticels on callused areas.]] The degree to which trees are able to repair gross physical damage to their bark is very variable. Some are able to produce a callus growth which heals over the wound rapidly, but leaves a clear scar, whilst others such as oaks do not produce an extensive callus repair. {{Clear}} ==Gallery== <gallery> Image:Bark nunniong.jpg|<Center>Eucalypt bark Image:Acer capillipes (Snakebark maple).jpg|<Center>''[[Acer capillipes]]'' (Red Snakebark Maple) Image:Pine bark.jpg|<Center>[[Monterey Pine]] bark Image:Black Poplar burrs and bark.JPG|<Center>A rare Black Poplar tree, showing the bark and [[Burr|burrs]]. Image:Bark of an old Sycamore.JPG|<Center>The typical appearance of Sycamore bark from an old tree. </gallery> ==See also== {{commonscat|Bark}} * [[Bark painting]] * [[Bark beetle]] * [[Trunk (botany)]] ==References== {{Reflist}} [[Category:Plant physiology]] [[ca:Escorça (anatomia vegetal)]] [[cs:Borka]] [[da:Bark (plantedel)]] [[de:Rinde]] [[es:Corteza (árbol)]] [[fr:Écorce]] [[gd:Rùsg]] [[hr:Kora (biljke)]] [[is:Börkur]] [[it:Corteccia (vegetale)]] [[lt:Žievė]] [[nl:Schors]] [[ja:樹皮]] [[no:Bark]] [[nn:Bork]] [[oc:Rusca]] [[pl:Kora]] [[pt:Súber]] [[qu:Yura qara]] [[ru:Кора]] [[scn:Scorcia (curteccia)]] [[simple:Bark]] [[fi:Kaarna]] [[sv:Bark]] [[wa:Schoice]] [[tl:Banakal]]