Bark is the outermost layers of stems A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh and roots In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating (growing up above the ground or especially above water). Furthermore, a stem normally occurring below ground is not exceptional either (see rhizome). So, it is of woody plants A woody plant is a plant that uses wood as its structural tissue. They are typically perennial plants that have their stems and larger roots reinforced with wood produced adjacent to the vascular tissues: typically the main stem and larger branches and roots are covered by a layer of thickened bark. Woody plants are usually either trees, shrubs,. Plants with bark include trees A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to 6 m; some authors set a minimum of 10 cm trunk diameter, woody vines A vine in the broad sense refers to any climbing or trailing plant. The narrower and original meaning is the grapevine (Vitis) and shrubs A shrub or bush is distinguished from a tree by its multiple stems and lower height, usually less than 5–6 m tall. A large number of plants can be either shrubs or trees, depending on the growing conditions they experience. Small, low shrubs such as lavender, periwinkle and thyme are often termed subshrubs. Bark refers to all the tissues outside of the vascular cambium The vascular cambium is a lateral meristem in the vascular tissue of plants. The vascular cambium is the source of both the secondary xylem and the secondary phloem (outwards), and is located between these tissues in the stem and root. A few leaf types also have a vascular cambium and is a nontechnical term.[1] It overlays the wood Wood is a hard, fibrous tissue found in many plants. It has been used for centuries for both fuel and as a construction material for several types of living areas such as houses. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression. In the strict sense wood is produced as and consists of the inner bark and the outer bark. The inner bark, which in older stems A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh is living tissue, includes the innermost area of the periderm. The outer bark in older stems, includes the dead tissue on the surface of the stems, along with parts of the innermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees is also called the rhytidome. Products used by people that are derived from bark include: spices A spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. In the kitchen, spices are distinguished from herbs, which are leafy, green plant parts used for flavoring and other flavorings, tannin, resin, latex Latex as found in nature is a milky sap-like fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums that coagulates on exposure to air. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or, 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.[2] 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 In agriculture and gardening, mulch is a protective cover placed over the soil, to retain moisture, reduce erosion, suppress weed growth and seed germination, and provide nutrients as they decay. Mulching in gardens and landscapes mimics leaf cover on forest floors.[3][4]
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Botanic description
Bark of Leucadendron argenteumWhat is commonly called bark includes a number of different tissues. Cork is an external, secondary tissue that is impermeable to water and gases, and is also called the phellem. The cork is produced by the Cork cambium Cork cambium is a tissue found in many vascular plants as part of the periderm. The cork cambium is a lateral meristem and is responsible for secondary growth that replaces the epidermis in roots and stems. It is found in woody and many herbaceous dicots, gymnosperms and some monocots, which usually lack secondary growth which is a layer of meristematically active cells The cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans, which serve as a lateral meristem for the periderm. The cork cambium, which is also called the phellogen, is normally only one cell layer thick and it divides periclinally to the outside producing cork. The phelloderm, which is not always present in all barks, is a layer of cells formed by and interior to the cork cambium. Together, the phellem (cork), phellogen (cork cambium) and phelloderm constitute the periderm.[5] Cork cell walls contain suberin Suberin is a waxy substance found in higher plants. Suberin is a main constituent of cork, and is named after the Cork Oak, Quercus suber, a waxy substance which protects the stem against water loss, the invasion of insects into the stem, and prevents infections by bacteria and fungal spores.[6] The cambium In botany this is a layer or layers of tissue, also known as lateral meristems, that are the source of cells for secondary growth. There are two types of cambium tissues, i.e., the cork cambium and the vascular cambium The vascular cambium is a lateral meristem in the vascular tissue of plants. The vascular cambium is the source of both the secondary xylem and the secondary phloem (outwards), and is located between these tissues in the stem and root. A few leaf types also have a vascular cambium, are the only parts of a woody stem where cell division Cell division is the process by which a parent cell divides into two or more daughter cells. Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort of cell division in prokaryotes is known as binary occurs; undifferentiated cells in the vascular cambium divide rapidly to produce secondary xylem In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek ξυλον , "wood", and indeed the best-known xylem tissue is wood, though it is found throughout the plant. Its basic function is to transport water but it also transports some to the inside and secondary phloem In vascular plants, phloem is the living tissue that carries organic nutrients , particularly sucrose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word φλόος (phloos) "bark". The phloem is concerned mainly with the transport of to the outside. Phloem In vascular plants, phloem is the living tissue that carries organic nutrients , particularly sucrose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word φλόος (phloos) "bark". The phloem is concerned mainly with the transport of is a nutrient A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. They build and repair tissues, give heat and energy, and regulate body processes. Methods for nutrient intake vary, with animals and-conducting tissue composed of sieve tubes or sieve cells mixed with parenchyma Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants and fibers. The Cortex In botany, the cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells often acquire irregularly thickened cell walls, and is the primary tissue of stems A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh 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 The pericycle is a cylinder of parenchyma cells that lies just inside the endodermis and is the outer most part of the stele of plants. From the outside to the inside of a mature woody stem, these layers are arranged: (1) Cork (Phellem) (2) Cork cambium (Phellogen) (3) Phelloderm (4) Cortex (5) Phloem (6) Vascular cambium (7) Xylem. The bark includes (1) through (5), and is composed of periderm and phloem and the cells that produce these tissues.[7] The periderms includes (1),(2) and (3).
Bark of a Pine tree in Tecpan, Guatemala.In young stems, which lack what is commonly called bark, the tissues are from the outside to the inside: epidermis, periderm, cortex, primary phloem, secoundary phloem, vascular cambium and then xylem. As the stem ages and grows, changes occur that transform the surface of the stem into the bark. The epidermis, which 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.
Periderm
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 (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 is a waxy substance found in higher plants. Suberin is a main constituent of cork, and is named after the Cork Oak, Quercus suber 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 The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species. Despite being first introduced outside the Andes region four centuries ago, tuber (which is an underground stem) constitutes the cork of the periderm.[8][9]
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 of the periderm, namely the epidermis, cortex and older secondary phloem die.[10]
Within the periderm are lenticels, 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
Living tree bark enveloping barbed wire Barbed wire, also known as barb wire , is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand(s). It is used to construct inexpensive fences and is used atop walls surrounding secured property. It is also a major feature of the fortifications in trench warfare (as a wire obstacle)The rhytidome is the most familiar part of bark, it is the outer layer that covers the trunks of trees. It is composed mostly of dead lignified cells and is produced by the formation of multiple layers of periderm, cortical and phloem tissue.[5] It is generally thickest and most distinctive at the trunk or bole In botany, trunk refers to the main structural member of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the trunk to the top, depending on the species. The (The area from the ground to where the main branching starts) of the tree.
Uses
Cork, sometimes confused with bark in colloquial speech, is the outermost layer of a woody stem, derived from the cork cambium Cork cambium is a tissue found in many vascular plants as part of the periderm. The cork cambium is a lateral meristem and is responsible for secondary growth that replaces the epidermis in roots and stems. It is found in woody and many herbaceous dicots, gymnosperms and some monocots, which usually lack secondary growth. It serves as protection against damage from parasites Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the host, herbivorous Herbivores are animals that are adapted to eat plants. Herbivory is a form of predation in which an organism consumes principally autotrophs[page needed] such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in general are known as primary consumers animals and diseases A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal disfunctions, such as autoimmune diseases. Ecologically, disease is defined as, as well as dehydration and fire. Cork can contain antiseptics Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Antiseptics are generally distinguished from antibiotics by the latter's ability to be transported through the lymphatic system to destroy bacteria within the body, and from disinfectants, which destroy like tannins Tannins are astringent, bitter plant polyphenols that either bind and precipitate or shrink proteins and various other organic compounds including amino acids and alkaloids. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine. Likewise, the destruction or, that protect against fungal and bacterial attacks that would cause decay Decomposition or rotting is the process by which tissues of a dead organism break down into simpler forms of matter. The process is essential for new growth and development of living organisms because it recycles the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death. It is a.
Backpack A backpack is, in its simplest form, a cloth sack carried on one's back and secured with two straps that go over the shoulders, but there can be exceptions. Light weight types of backpacks are sometimes worn on only one shoulder strap made of birch bark.In some plants, the bark is substantially thicker, providing further protection and giving the bark a characteristically distinctive structure with deep ridges. 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. It is native to southwest Europe and northwest Africa) the bark is thick enough to be harvested as a cork product Cork material is an impermeable, buoyant material, a prime-subset of generic cork tissue that is harvested for commercial use primarily from Quercus suber that is endemic to southwest Europe and northwest Africa. Cork is composed of suberin, a hydrophobic substance, and because of its impermeability, buoyancy, elasticity, and fire resistance, it without killing the tree. Some barks can be removed in long sheets; the smooth surfaced bark of birch Birch is the name of a certain tree of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae trees has been used as a covering in the making of canoes, as the drainage layer in roofs, for shoes, backpacks etc. The most famous example of using birch bark for canoes is the birch canoes of North America.[11]
The bark of some trees is edible; in Finland, pine See Pinus classification for complete taxonomy to species level. See list of pines by region for list of species by geographical distribution bread is made from rye Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskies, some vodkas, and animal fodder. It can also be eaten whole, either as boiled rye berries, or by being rolled, similar to rolled to which the toasted and ground innermost layer of pine bark is added, the Sami The Sami people, also spelled Sámi, or Saami, are one of the indigenous people of northern Europe inhabiting Sápmi, which today encompasses parts of northern Sweden, Norway, Finland and the Kola Peninsula of Russia but also in the border area between south and middle Sweden. Their ancestral lands span an area the size of Sweden in the Nordic people of far northern Europe Europe is one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus region (Specification of borders) and the Black Sea to the southeast. Europe is bordered by the Arctic Ocean and used large sheets of Pinus sylvestris The Scots Pine is a species of pine native to Europe and Asia, ranging from Ireland, Great Britain and Portugal in the west, east to eastern Siberia, south to the Caucasus Mountains, and as far north as Lapland. In the north of its range, it occurs from sea level to 1,000 m, while in the south of its range, it is a high altitude mountain tree, bark that were removed in the spring, prepared and stored for use as a staple food resource and the inner bark was eaten fresh, dried or roasted.[12] Bark contains strong fibres known as bast Bast fibre or skin fibre is plant fibre collected from the phloem or bast surrounding the stem of certain, mainly dicotyledonic, plants. They support the conductive cells of the phloem and provide strength to the stem. Most of the technically important bast fibres are obtained from herbs cultivated in agriculture, as for instance flax, hemp, or, and there is a long tradition in northern Europe of using bark from coppiced Coppicing is a traditional method of woodland management which takes advantage of the fact that many trees reshoot from the stump or roots if cut down. In a coppiced wood young tree stems are repeatedly cut down to near ground level. In subsequent growth years, many new shoots will emerge, and, after a number of years the coppiced tree, or stool, young branches of the small-leaved lime (Tilia cordata It is a deciduous tree growing to 20-38 m tall, with a trunk up to 1-2 m diameter. The leaves are alternately arranged, rounded to triangular-ovate, 3-8 cm long and broad, mostly hairless except for small tufts of brown hair in the leaf vein axils - the leaves are distinctively heart-shaped. The small yellow-green hermaphrodite flowers are) to produce cordage A rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength . Rope is thicker and stronger than similarly constructed cord, line, string, and twine and rope, used for example in the rigging of Viking age longships.[13]
Among the commercial products made from bark are cork, cinnamon, quinine[14] (from the bark of Cinchona)[15] 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 epiphytes.
Bark chip extraction
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
Patches of Bark naturally flaking off the bottom of Roystonea regia palm trunk, Kolkata, IndiaCut 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,[16] 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
Alder bark (Alnus glutinosa) with characteristic lenticels and abnormal lenticels on callused areas. Sun scald damage on Sitka spruceThe 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.
Frost crack and Sun scald (flora) are examples of damage found on tree bark which trees can repair to a degree, depending on the severity.
Gallery
| Eucalypt bark | Acer capillipes (Red Snakebark Maple) | Monterey Pine bark | A rare Black Poplar tree, showing the bark and burrs. |
| The typical appearance of Sycamore bark from an old tree. | Quercus robur bark with a large burr and lichen. | Kauri bark |
Extensive callus growth on a young Ash tree with Frost crack |
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Tree cross section diagram |
See also
| Wikimedia Commons has media related to: Bark |
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