![黑松 Pinus thunbergii 20211007185113 01](https://upload.wikimedia.org/wikipedia/commons/1/1e/%E9%BB%91%E6%9D%BE_Pinus_thunbergii_20211007185113_01.jpg)
Bark is the outermost layers of
stems and
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
s of
woody plant
A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to herbaceous plants that die back to the ground until sp ...
s. Plants with bark include
tree
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
s, woody
vine
A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themselv ...
s, and
shrub
A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...
s. Bark refers to all the
tissues outside the
vascular cambium
The vascular cambium is the main growth tissue in the stems and roots of many plants, specifically in dicots such as buttercups and oak trees, gymnosperms such as pine trees, as well as in certain other vascular plants. It produces secondary xyle ...
and is a nontechnical term.
It overlays the wood and consists of the inner bark and the outer bark. The inner bark, which in older
stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushro ...
s is living tissue, includes the innermost layer of the periderm. The outer bark on older stems includes the dead tissue on the surface of the stems, along with parts of the outermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees which lies external to the living periderm is also called the
rhytidome.
Products derived from bark include bark shingle siding and wall coverings, spices and other flavorings,
tanbark
Tanbark is the bark of certain species of trees, traditionally used for tanning hides into leather.
The words "tannin", "tanning", "tan," and " tawny" are derived from the Medieval Latin ''tannare'', "to convert into leather."
Bark mills are ...
for
tannin
Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids.
The term ''tannin'' (from Anglo-Norman ''tanner'', ...
,
resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
,
latex
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
, medicines, poisons, various
hallucinogen
Hallucinogens are a large, diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mood, and perception as well as other changes. Most hallucinogens can be categorized ...
ic chemicals and
cork
Cork or CORK may refer to:
Materials
* Cork (material), an impermeable buoyant plant product
** Cork (plug), a cylindrical or conical object used to seal a container
***Wine cork
Places Ireland
* Cork (city)
** Metropolitan Cork, also known as G ...
. Bark has been used to make cloth, canoes, and ropes and used as a surface for paintings and map making. A number of plants are also grown for their attractive or interesting bark colorations and surface textures or their bark is used as landscape
mulch
A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area.
A m ...
.
The process of removing bark is decortication and a log or trunk from which bark has been removed is said to be decorticated.
Botanical description
Bark is present only on woody plants - herbaceous plants and stems of young plants lack bark.
![Tree secondary components diagram](https://upload.wikimedia.org/wikipedia/commons/9/9b/Tree_secondary_components_diagram.png)
From the outside to the inside of a mature woody stem, the layers include the following:
# Bark
## Periderm
###
Cork
Cork or CORK may refer to:
Materials
* Cork (material), an impermeable buoyant plant product
** Cork (plug), a cylindrical or conical object used to seal a container
***Wine cork
Places Ireland
* Cork (city)
** Metropolitan Cork, also known as G ...
(phellem or suber), includes the rhytidome
###
Cork cambium
Cork cambium (pl. cambia or cambiums) is a tissue found in many vascular plants as a part of the epidermis. It is one of the many layers of bark, between the cork and primary phloem. The cork cambium is a lateral meristem and is responsible fo ...
(phellogen)
### Phelloderm
##
Cortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
##
Phloem
Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
#
Vascular cambium
The vascular cambium is the main growth tissue in the stems and roots of many plants, specifically in dicots such as buttercups and oak trees, gymnosperms such as pine trees, as well as in certain other vascular plants. It produces secondary xyle ...
#
Wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
(
xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...
)
##
Sapwood (alburnum)
##
Heartwood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin tha ...
(duramen)
#
Pith
Pith, or medulla, is a tissue in the stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other ...
(medulla)
In young stems, which lack what is commonly called bark, the tissues are, from the outside to the inside:
#
Epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
, which may be replaced by periderm
# Cortex
# Primary and secondary phloem
# Vascular cambium
# Secondary and primary xylem.
Cork cell walls contain
suberin
Suberin, cutin and lignins are complex, higher plant epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids called suberin acid ...
, a waxy substance which protects the stem against water loss, the invasion of insects into the stem, and prevents infections by
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
and fungal spores. The cambium tissues, i.e., the cork cambium and the
vascular cambium
The vascular cambium is the main growth tissue in the stems and roots of many plants, specifically in dicots such as buttercups and oak trees, gymnosperms such as pine trees, as well as in certain other vascular plants. It produces secondary xyle ...
, are the only parts of a woody stem where
cell division
Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...
occurs; undifferentiated cells in the vascular cambium divide rapidly to produce secondary
xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...
to the inside and secondary
phloem
Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
to the outside. Phloem is a
nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
-conducting tissue composed of sieve tubes or sieve cells mixed with
parenchyma
Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms.
Etymology
The term ''parenchyma'' is New Latin from the word π ...
and fibers. The
cortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
is the primary tissue of
stem
Stem or STEM may refer to:
Plant structures
* Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang
* Stipe (botany), a stalk to support some other structure
* Stipe (mycology), the stem of a mushro ...
s and roots. In stems the cortex is between the
epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
layer and the phloem, in roots the inner layer is not phloem but the
pericycle
The pericycle is a cylinder of parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants.
Although it is composed of non-vascular parenchyma cells, it's still considered part of the vas ...
.
As the stem ages and grows, changes occur that transform the surface of the stem into the bark. The
epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
is a layer of cells that cover the plant body, including the stems, leaves, flowers and fruits, that protects the plant from the outside world. 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.
Cork, sometimes confused with bark in colloquial speech, is the outermost layer of a woody stem, derived from the
cork cambium
Cork cambium (pl. cambia or cambiums) is a tissue found in many vascular plants as a part of the epidermis. It is one of the many layers of bark, between the cork and primary phloem. The cork cambium is a lateral meristem and is responsible fo ...
. It serves as protection against damage from
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s,
herbivorous
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
animals and diseases, as well as dehydration and fire.
Periderm
![Poskozena borka na tresni 20210821 150436](https://upload.wikimedia.org/wikipedia/commons/a/a1/Poskozena_borka_na_tresni_20210821_150436.jpg)
Often a secondary covering called the periderm forms on small woody stems and many non-woody plants, which is composed of cork (phellem), the
cork cambium
Cork cambium (pl. cambia or cambiums) is a tissue found in many vascular plants as a part of the epidermis. It is one of the many layers of bark, between the cork and primary phloem. The cork cambium is a lateral meristem and is responsible fo ...
(phellogen), and the phelloderm. The periderm forms from the phellogen which serves as a lateral meristem. The periderm replaces the epidermis, and acts as a protective covering like the epidermis. Mature phellem cells have
suberin
Suberin, cutin and lignins are complex, higher plant epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids called suberin acid ...
in their walls to protect the stem from desiccation and pathogen attack. Older phellem cells are dead, as is the case with woody stems. The skin on the potato tuber (which is an underground stem) constitutes the cork of the periderm.
In woody plants, the epidermis of newly grown stems is replaced by the periderm later in the year. As the stems grow a layer of cells form under the epidermis, called the cork cambium, these cells produce cork cells that turn into cork. A limited number of cell layers may form interior to the cork cambium, called the phelloderm.
As the stem grows, the cork cambium produces new layers of cork which are impermeable to gases and water and the cells outside the periderm, namely the epidermis, cortex and older secondary phloem die.
Within the periderm are
lenticel
A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a ...
s, which form during the production of the first periderm layer. Since there are living cells within the cambium layers that need to exchange gases during metabolism, these lenticels, because they have numerous intercellular spaces, allow gaseous exchange with the outside atmosphere. As the bark develops, new lenticels are formed within the cracks of the cork layers.
Rhytidome
The rhytidome is the most familiar part of bark, being the outer layer that covers the trunks of trees. It is composed mostly of dead cells and is produced by the formation of multiple layers of
suberized
Suberin, cutin and lignins are complex, higher plant epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids called suberin acid ...
periderm, cortical and phloem tissue.
[Dickison, WC. 2000. Integrative Plant Anatomy, Academic Press, San Diego, 186–195.] The rhytidome is especially well developed in older stems and roots of trees. In shrubs, older bark is quickly
exfoliated and thick rhytidome accumulates. It is generally thickest and most distinctive at the trunk or
bole (the area from the ground to where the main branching starts) of the tree.
Chemical composition
Bark tissues make up by weight between 10 and 20% of woody vascular plants and consists of various
biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
s,
tannin
Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids.
The term ''tannin'' (from Anglo-Norman ''tanner'', ...
s,
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
,
suberin
Suberin, cutin and lignins are complex, higher plant epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids called suberin acid ...
and
polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
s.
Up to 40% of the bark tissue is made of lignin, which forms an important part of a plant, providing structural support by crosslinking between different polysaccharides, such as cellulose.
Condensed
tannin
Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids.
The term ''tannin'' (from Anglo-Norman ''tanner'', ...
, which is in fairly high concentration in bark tissue, is thought to inhibit
decomposition
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
.
It could be due to this factor that the degradation of lignin is far less pronounced in bark tissue than it is in wood.
It has been proposed that, in the cork layer (the phellogen), suberin acts as a barrier to microbial degradation and so protects the internal structure of the plant.
Analysis of the
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
in bark wall during decay by the white-rot fungi ''Lentinula edodes'' (
Shiitake mushroom
The shiitake (alternate form shitake) (; ''Lentinula edodes'') is an edible mushroom native to East Asia, which is now cultivated and consumed around the globe. It is considered a medicinal mushroom in some forms of traditional medicine.
Tax ...
) using
13C NMR revealed that the lignin polymers contained more Guaiacyl
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
units than Syringyl units compared to the interior of the plant.
Guaiacyl units are less susceptible to degradation as, compared to syringyl, they contain fewer aryl-aryl bonds, can form a condensed lignin structure and have a lower
redox potential
Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respe ...
.
This could mean that the concentration and type of lignin units could provide additional resistance to fungal decay for plants protected by bark.
Damage and repair
Bark can sustain damage from environmental factors, such as
frost crack
Frost crack or Southwest canker is a form of tree bark damage sometimes found on thin barked trees, visible as vertical fractures on the southerly facing surfaces of tree trunks. Frost crack is distinct from sun scald and sun crack and physically d ...
and
sun scald
Sun scald is the freezing of bark following high temperatures in the winter season, resulting in permanent visible damage to bark. Fruits may also be damaged. In the northern hemisphere, it is also called southwest injury.
Causes
The reason the ...
, as well as biological factors, such as
woodpecker
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
and
boring beetle attack. Male
deer
Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the reindeer ...
and other male members of the Cervidae cause extensive bark damage during the rutting season by rubbing their antlers against the tree to remove their velvet.
![BarkAndWire-0308](https://upload.wikimedia.org/wikipedia/commons/3/3a/BarkAndWire-0308.jpg)
Bark is often damaged by being bound to stakes or wrapped with wires. In the past, this damage was called bark-galling, and was treated by applying
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
laid on the galled place and binding up with
hay
Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticated ...
. In modern usage, "galling" most typically refers to a type of
abnormal growth on a plant caused by insects or pathogens.
Bark damage can have a number of detrimental effects on the plant. Bark serves as a physical barrier to disease pressure, especially from fungi, so its removal makes the plant more susceptible to disease. Damage or destruction of the phloem impedes the transport of photosynthetic products throughout the plant; in extreme cases, when a band of phloem all the way around the stem is removed, the plant will usually quickly die. Bark damage in horticultural applications, as in gardening and public landscaping, results in often unwanted aesthetic damage.
The degree to which woody plants are able to repair gross physical damage to their bark is quite variable across species and type of damage. 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.
Sap
Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant.
Sap is distinct from latex, resin, or cell sap; it is a separa ...
is sometimes produced to seal the damaged area against disease and insect intrusion.
A number of living organisms live in or on bark, including insects, 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.
File:Chinese Evergreen Elm after Yellow-Bellied Sapsucker, February 2012.jpg, The patterns left in the bark of a Chinese Evergreen Elm after repeated visits by a Yellow-Bellied Sapsucker (woodpecker) in early 2012.
File:Chinese Evergreen Elm in process of healing, February 2014.jpg, The self-repair of the Chinese Evergreen Elm showing new bark growth, lenticels, and other self-repair of the holes made by a Yellow-Bellied Sapsucker (woodpecker) about two years earlier.
File:Alder bark and callus.JPG, Alder bark (''Alnus glutinosa'') with characteristic lenticels and abnormal lenticels on callused areas.
File:Sun Scald on Sitka Spruce.JPG, Sun scald damage on Sitka spruce
Uses
The inner bark (
phloem
Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
) of some trees is edible. In hunter-gatherer societies and in times of famine, it is harvested and used as a food source. In Scandinavia,
bark bread
Bark bread is a traditional food made with cambium (phloem) flour. It has a history of use as famine food.
History
Bark bread seems to be a primarily Scandinavian tradition. Mention of it is found in medieval literature, and it may have an even ...
is made from
rye
Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat (''Triticum'') and barley (genus ''Hordeum''). Rye grain is u ...
to which the toasted and ground innermost layer of bark of
scots pine
''Pinus sylvestris'', the Scots pine (UK), Scotch pine (US) or Baltic pine, is a species of tree in the pine family Pinaceae that is native to Eurasia. It can readily be identified by its combination of fairly short, blue-green leaves and orang ...
or
birch
A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...
is added. The
Sami
Acronyms
* SAMI, ''Synchronized Accessible Media Interchange'', a closed-captioning format developed by Microsoft
* Saudi Arabian Military Industries, a government-owned defence company
* South African Malaria Initiative, a virtual expertise net ...
people of far northern Europe use large sheets of ''
Pinus sylvestris
''Pinus sylvestris'', the Scots pine (UK), Scotch pine (US) or Baltic pine, is a species of tree in the pine family Pinaceae that is native to Eurasia. It can readily be identified by its combination of fairly short, blue-green leaves and orang ...
'' bark that are removed in the spring, prepared and stored for use as a staple food resource. The inner bark is eaten fresh, dried or roasted.
![Detaching inner bark of pine](https://upload.wikimedia.org/wikipedia/commons/5/5b/Detaching_inner_bark_of_pine.jpg)
Bark can be used as a construction material, and was used widel in pre-industrial societies. Some barks, particularly
Birch
A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...
bark, can be removed in long sheets and other mechanically cohesive structures, allowing the bark to be used in the construction of canoes, as the drainage layer in roofs, for shoes, backpacks, and other useful items.
![Tragekorb aus Birkenleder](https://upload.wikimedia.org/wikipedia/commons/4/4a/Tragekorb_aus_Birkenleder.JPG)
In the cork oak (''
Quercus suber
''Quercus suber'', commonly called the cork oak, is a medium-sized, evergreen oak tree in the section ''Quercus'' sect. ''Cerris''. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the cores ...
'') the bark is thick enough to be harvested as a
cork product without killing the tree; in this species the bark may get very thick (e.g. more than 20 cm has been reported).
Some s have significantly different
phytochemical
Phytochemicals are chemical compounds produced by plants, generally to help them resist fungi, bacteria and plant virus infections, and also consumption by insects and other animals. The name comes . Some phytochemicals have been used as poisons ...
content from other parts. Some of these phytochemicals have
pesticidal
Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lamp ...
, culinary, or medicinally and culturally important
ethnopharmacological
Ethnomedicine is a study or comparison of the traditional medicine based on bioactive compounds in plants and animals and practiced by various ethnic groups, especially those with little access to western medicines, e.g., indigenous peoples. The ...
properties.
Bark contains strong fibres known as
bast, and there is a long tradition in northern Europe of using bark from
coppice
Coppicing is a traditional method of woodland management which exploits the capacity of many species of trees to put out new shoots from their stump or roots if cut down. In a coppiced wood, which is called a copse, young tree stems are repeated ...
d young branches of the small-leaved lime (''
Tilia cordata
''Tilia cordata'', the small-leaved lime or small-leaved linden, is a species of tree in the family Malvaceae, native to much of Europe. Other common names include little-leaf or littleleaf linden, or traditionally in South East England, pry or p ...
'') to produce
cordage
Cordage may refer to:
* Rigging, cords and ropes attached to masts and sails on a ship or boat
* Rope, yarns, plies or strands twisted or braided together into a larger form
See also
* String (disambiguation)
* Cord (disambiguation)
Cord or ...
and
rope
A rope is a group of yarns, plies, fibres, or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similarly ...
, used for example in the
rigging
Rigging comprises the system of ropes, cables and chains, which support a sailing ship or sail boat's masts—''standing rigging'', including shrouds and stays—and which adjust the position of the vessel's sails and spars to which they are ...
of
Viking Age
The Viking Age () was the period during the Middle Ages when Norsemen known as Vikings undertook large-scale raiding, colonizing, conquest, and trading throughout Europe and reached North America. It followed the Migration Period and the Ger ...
longship
Longships were a type of specialised Scandinavian warships that have a long history in Scandinavia, with their existence being archaeologically proven and documented from at least the fourth century BC. Originally invented and used by the Nors ...
s.
Among the commercial products made from bark are
cork
Cork or CORK may refer to:
Materials
* Cork (material), an impermeable buoyant plant product
** Cork (plug), a cylindrical or conical object used to seal a container
***Wine cork
Places Ireland
* Cork (city)
** Metropolitan Cork, also known as G ...
,
cinnamon
Cinnamon is a spice obtained from the inner bark of several tree species from the genus ''Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, breakfa ...
,
quinine
Quinine is a medication used to treat malaria and babesiosis. This includes the treatment of malaria due to ''Plasmodium falciparum'' that is resistant to chloroquine when artesunate is not available. While sometimes used for nocturnal leg cr ...
(from the bark of
Cinchona
''Cinchona'' (pronounced or ) is a genus of flowering plants in the family Rubiaceae containing at least 23 species of trees and shrubs. All are native to the Tropical Andes, tropical Andean forests of western South America. A few species are ...
) and
aspirin
Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
(from the bark of
willow
Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist s ...
trees). The bark of some trees, notably oak (''Quercus robur'') is a source of
tannic acid
Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity ( pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which correspon ...
, which is used in
tanning
Tanning may refer to:
*Tanning (leather), treating animal skins to produce leather
*Sun tanning, using the sun to darken pale skin
**Indoor tanning, the use of artificial light in place of the sun
**Sunless tanning, application of a stain or dye t ...
. Bark chips generated as a
by-product
A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced.
A by-product can be useful and marketable or it can be consid ...
of
lumber
Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
production are often used in bark
mulch
A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area.
A m ...
. 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
An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...
s.
Wood bark contains
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
which when
pyrolyzed
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''pyr ...
yields a liquid
bio-oil
Pyrolysis oil, sometimes also known as bio-crude or bio-oil, is a synthetic fuel under investigation as substitute for petroleum. It is obtained by heating dried biomass without oxygen in a reactor at a temperature of about with subsequent cool ...
product rich in
natural phenol
In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to eco ...
derivatives. These are used as a replacement for fossil-based phenols in phenol-formaldehyde (PF) resins used in
Oriented Strand Board
Oriented strand board (OSB) is a type of engineered wood similar to particle board, formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations. It was invented by Armin Elmendorf in California in 1963. ...
(OSB) and plywood.
Gallery
File:Bark nunniong.jpg, Eucalypt bark
File:Close-up of living bark on a tree in England.JPG, Close-up of living bark on a tree in England
File:Acer capillipes (Snakebark maple).jpg, ''Acer capillipes
''Acer capillipes'' (Kyushu maple or red snakebark maple; ja, ホソエカエデ, translit=hosoekaede), is a maple in the same taxonomic section as other snakebark maples such as '' A. pensylvanicum'', '' A. davidii'' and '' A. rufinerve''. It i ...
'' (Red Snakebark Maple)
File:Pine bark.jpg, Monterey Pine
''Pinus radiata'' ( syn. ''Pinus insignis''), the Monterey pine, insignis pine or radiata pine, is a species of pine native to the Central Coast of California and Mexico (Guadalupe Island and Cedros island). It is an evergreen conifer in the fa ...
bark
File:Black Poplar burrs and bark.JPG, A rare Black Poplar tree, showing the bark and burl
A burl (American English) or burr (British English) is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from do ...
s.
File:Bark of an old Sycamore.JPG, The typical appearance of Sycamore bark from an old tree.
File:Burr on Oak at Kilbirnie.JPG, ''Quercus robur
''Quercus robur'', commonly known as common oak, pedunculate oak, European oak or English oak, is a species of flowering plant in the beech and oak family, Fagaceae. It is a large tree, native plant, native to most of Europe west of the Caucasus ...
'' bark with a large burl and lichen.
File:The_Mc_Kinney_Kauri_Borke.jpg, Kauri
''Agathis'', commonly known as kauri or dammara, is a genus of 22 species of evergreen tree. The genus is part of the ancient conifer family Araucariaceae, a group once widespread during the Jurassic and Cretaceous periods, but now largely res ...
bark
File:Beech tree - recovery from heat damage.jpg, Beech bark with callus growth following fire (heat) damage
File:OakHolly.jpg, Damaged bark
File:Oak bark.jpg, Common oak bark
File:Rainbow Eucalyptus Maui.jpg, "Rainbow" Eucalyptus bark on the Hawaiian island of Maui
The island of Maui (; Hawaiian: ) is the second-largest of the islands of the state of Hawaii at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is the largest of Maui County's four islands, which ...
File:雨豆樹 Samanea saman 20210914102518 05.jpg, The old bark has a metallic luster. In 2016, the height of the tree was 15 meters and the bust circumference was 5.7 meters. ''Samanea saman
''Samanea saman'', also sometimes known as the rain tree, is a species of flowering tree in the pea family, Fabaceae, now in the Mimosoid clade and is native to Central and South America. Its range extends from Mexico south to Peru and Brazil, ...
''
See also
*
Bark beetle
A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the ...
*
Bark painting
Bark painting is an Australian Aboriginal art form, involving painting on the interior of a strip of tree bark. This is a continuing form of artistic expression in Arnhem Land (especially among the Yolngu peoples) and other regions in the Top ...
*
Trunk (botany)
In botany, the trunk (or bole) is the plant stem, stem and main wooden axis of a tree, which is an important feature in tree identification, and which often differs markedly from the bottom of the trunk to the top, depending on the species. The t ...
*
Bark isolate
Bark isolates are chemicals which have been extracted from bark. Prominent medical examples are salicylic acid (active metabolite of aspirin) and paclitaxel (Taxol). The pharmacology
Pharmacology is a branch of medicine, biology and phar ...
*
Bark-binding
Bark-binding is a disease in trees that causes the bark of the plant to become hardened and tough, restricting the growth of the trunk. It is caused by a sudden restriction of the tree's growth, the rubbing of livestock against the trunk, or by l ...
, a diseased condition of tree bark
References
Other references
*Cédric Pollet, ''Bark: An Intimate Look at the World's Trees''. London, Frances Lincoln, 2010. (Translated by Susan Berry)
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Plant physiology
Plant morphology