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Adventitious

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Adventitious has various meanings in various disciplines and in general usage.

Adventitious is from the Latin root advenire, meaning "to come or be superadded" and in correct English the meanings tend to have connections to accidental or casual occurrence. "...of the nature of an addition from without; supervenient, accidental, casual.

People sometimes speak of an event or occurrence as being "random", when the word "adventitious", or perhaps "accidental
Accidental
Accidental may mean:* Accidental * Accidental , by Fred Frith* Accidental , a biological phenomenon more commonly known as vagrancy* Accidental property, a philosophical term-See also:* Accident...

", might be more strictly correct.

Botany


In botany
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

, adventitious refers to structures that develop in an unusual place. This part of the article discusses adventitious root
Root
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 . Furthermore, a stem normally occurring below ground is not exceptional either...

s, bud
Bud
In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots, or may have...

s and shoot
Shoot
Shoots are new plant growth, they can include stems, flowering stems with flower buds, and leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop...

s, which are very common in vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...

s.

Buds and shoots


Adventitious bud
Bud
In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots, or may have...

s develop from places other than a shoot apical meristem, which occurs at the tip of a stem. They may develop on stems, roots or leaves. Shoot apical meristems produce one or more axillary or lateral buds at each node. When stems produce considerable secondary growth
Secondary growth
In many vascular plants, secondary growth is the result of the activity of the two lateral meristems, the cork cambium and vascular cambium. Arising from lateral meristems, secondary growth increases the girth of the plant root or stem, rather than its length. As long as the lateral meristems...

, the axillary buds may be destroyed. Adventitious buds may then develop on stems with secondary growth.

Adventitious buds are often formed after the stem is wounded or pruned
Pruning
Pruning is a horticultural practice involving the selective removal of parts of a plant, such as branches, buds, or roots. Reasons to prune plants include deadwood removal, shaping , improving or maintaining health, reducing risk from falling branches, preparing nursery specimens for...

. The adventitious buds help to replace lost branches. Adventitious buds and shoots also may develop on mature tree trunks when a shaded trunk is exposed to bright sunlight because surrounding trees are cut down. Redwood (Sequoia sempervirens) trees often develop many adventitious buds on their lower trunks. If the main trunk dies, a new one often sprouts from one of the adventitious buds. Small pieces of redwood trunk are sold as souvenirs termed redwood burls. They are placed in a pan of water, and the adventitious buds sprout to form shoots.

Some plants normally develop adventitious buds on their roots, which can extend quite a distance from the plant. Shoots that develop from adventitious buds on roots are termed suckers
Basal shoot
A basal shoot, root sprout, adventitious shoot, water sprout or sucker is a shoot or cane which grows from a bud at the base of a tree or shrub or from its roots. This shoot then becomes, or takes the form of, a singular plant. A plant that produces suckers is referred to as surculose...

. They are a type of natural vegetative reproduction
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...

 in many species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, e.g. many grasses, quaking aspen and Canada thistle. The Pando quaking aspen grew from one trunk to 47,000 trunks via adventitious bud formation on a single root system.

Some leaves develop adventitious buds, which then form adventitious roots, as part of vegetative reproduction
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...

; e.g. piggyback plant (Tolmiea menziesii) and mother-of-thousands (Kalanchoe daigremontiana
Kalanchoe daigremontiana
Kalanchoe daigremontiana syn. Bryophyllum daigremontianum also called Devil's Backbone, Alligator Plant, Mexican Hat Plant or Mother of Thousands is a succulent plant native to Madagascar. This plant is distinguished by its ability to propagate via vegetative propagation...

). The adventitious plantlets then drop off the parent plant and develop as separate clone
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...

s of the parent.

Coppicing
Coppicing
Coppicing is a traditional method of woodland management which takes advantage of the fact that many trees make new growth from the stump or roots if cut down. In a coppiced wood, young tree stems are repeatedly cut down to near ground level...

 is the practice of cutting tree
Tree
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...

 stems to the ground to promote rapid growth of adventitious shoots. It is traditionally used to produce poles, fence material or firewood. It is also practiced for biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 crops grown for fuel, such as poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....

 or willow.

Roots


Adventitious rooting may be a stress-avoidance acclimation for some species, driven by such inputs as hypoxia/anoxia
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...

 or nutrient deficiency. Another ecologically important function of adventitious rooting is the vegetative propagation of tree species such as Salix and Sequoia in riparian settings.

The ability of plant stems to form adventitious roots is utilised in commercial propagation by cutting
Cutting
Cutting is the separation of a physical object, or a portion of a physical object, into two portions, through the application of an acutely directed force. An implement commonly used for cutting is the knife or in medical cases the scalpel...

s. Understanding of the physiological mechanisms behind adventitious rooting has allowed some progress to be made in improving the rooting of cuttings by the application of synthetic auxins as rooting powders and by the use of selective basal wounding. Further progress will be made in future years by applying research into other regulatory mechanisms to commercial propagation and by the comparative analysis of molecular and ecophysiological control of adventitious rooting in 'hard to root' Vs. 'easy to root' species.

Growth


Adventitious roots and buds usually develop near the existing vascular tissues so they can connect to the xylem
Xylem
Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...

 and phloem
Phloem
In vascular plants, phloem is the living tissue that carries organic nutrients , in particular, glucose, 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 "bark"...

. However, the exact location varies greatly. In young stems, adventitious roots often form from parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...

 between the vascular bundle
Vascular bundle
A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in vascular tissue, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues...

s. In stems with secondary growth, adventitious roots often originate in phloem parenchyma near the vascular cambium
Vascular cambium
The vascular cambium is a part of the morphology of plants. It consists of cells that are partly specialized, for the tissues that transport water solutions, but have not reached any of the final forms that occur in their branch of the specialization graph...

. In stem cuttings, adventitious roots sometimes also originate in the callus
Callus
A callus is an especially toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation. Rubbing that is too frequent or forceful will cause blisters rather than allow calluses to form. Since repeated contact is required, calluses...

 cells that form at the cut surface. Leaf cuttings of the Crassula
Crassula
Crassula is a large genus of succulent plants containing many species, including the popular Jade Plant, Crassula ovata. They are native to many parts of the globe, but cultivated varieties are almost exclusively from the Eastern Cape of South Africa....

form adventitious roots in the epidermis.

Modification


Tuberous roots are without any definite shape; example: sweet Potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

.

Fasciculated root (tuberous root) occur in clusters at the base of the stem; example: asparagus
Asparagus
Asparagus officinalis is a spring vegetable, a flowering perennialplant species in the genus Asparagus. It was once classified in the lily family, like its Allium cousins, onions and garlic, but the Liliaceae have been split and the onion-like plants are now in the family Amaryllidaceae and...

, dahlia
Dahlia
Dahlia is a genus of bushy, tuberous, perennial plants native to Mexico, Central America, and Colombia. There are at least 36 species of dahlia, some like D. imperialis up to 10 metres tall. Dahlia hybrids are commonly grown as garden plants...

.

Nodulose roots become swollen near the tips; example: turmeric
Turmeric
Turmeric is a rhizomatous herbaceous perennial plant of the ginger family, Zingiberaceae. It is native to tropical South Asia and needs temperatures between 20 °C and 30 °C and a considerable amount of annual rainfall to thrive...

.

Stilt roots arise from the first few nodes of the stem. These penetrate obliquely down in to the soil and give support to the plant; example: maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

, sugarcane
Sugarcane
Sugarcane refers to any of six to 37 species of tall perennial grasses of the genus Saccharum . Native to the warm temperate to tropical regions of South Asia, they have stout, jointed, fibrous stalks that are rich in sugar, and measure two to six metres tall...

.

Prop roots give mechanical support to the aerial branches. The lateral branches grow vertically downward into the soil and acts as pillars; example: banyan
Banyan
A banyan is a fig that starts its life as an epiphyte when its seeds germinate in the cracks and crevices on a host tree...

.

Climbing roots these roots arising from nodes attach themselves to some support and climb over it; example: money plant
Money plant
Money plant is a common name for a few different plant species, including:* Epipremnum aureum - a tropical vining plant from the Solomon Islands...

.

Propagation


Adventitious roots and buds are very important when people propagate plants via cuttings, layering
Layering
Layering is a means of plant propagation in which a portion of an aerial stem grows roots while still attached to the parent plant and then detaches as an independent plant. Layering has evolved as a common means of vegetative propagation of numerous species in natural environments...

, tissue culture
Plant tissue culture
Plant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues or organs under sterile conditions on a nutrient culture medium of known composition. Plant tissue culture is widely used to produce clones of a plant in a method known as micropropagation...

. Plant hormones, termed auxin
Auxin
Auxins are a class of plant hormones with some morphogen-like characteristics. Auxins have a cardinal role in coordination of many growth and behavioral processes in the plant's life cycle and are essential for plant body development. Auxins and their role in plant growth were first described by...

s, are often applied to stem, shoot
Shoot
Shoots are new plant growth, they can include stems, flowering stems with flower buds, and leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop...

 or leaf
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 cuttings to promote adventitious root formation, e.g. African violet and sedum
Sedum
Sedum is a large genus of flowering plants in the family Crassulaceae, members of which are commonly known as stonecrops. It contains around 400 species of leaf succulents that are found throughout the Northern Hemisphere, varying from annual and creeping herbs to shrubs. The plants have...

 leaves and shoots of poinsettia
Poinsettia
Euphorbia pulcherrima, commonly known as Zack Wood or noche buena, is a species of flowering plant indigenous to Mexico and Central America. The name "poinsettia" is after Joel Roberts Poinsett, the first United States Minister to Mexico, who introduced the plant into the US in 1825...

 and coleus
Coleus
Solenostemon is a genus of perennial plants, native to tropical Africa, Asia, Australia, the East Indies, the Malay Archipelago, and the Philippines...

. Propagation via root cuttings requires adventitious bud formation, e.g. in horseradish
Horseradish
Horseradish is a perennial plant of the Brassicaceae family, which also includes mustard, wasabi, broccoli, and cabbages. The plant is probably native to south eastern Europe and the Arab World , but is popular around the world today...

 and apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

. In layering, adventitious roots are formed on aerial stems before the stem section is removed to make a new plant. Large houseplants are often propagated by air layering. Adventitious roots and buds must develop in tissue culture propagation of plants.

Law


In law, adventitious could mean "falling to a man by mere fortune, or from a stranger..."

Medicine


In medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, adventitious and related words such as adventitia
Adventitia
Adventitia is the outermost connective tissue covering of any organ, vessel, or other structure. It is also called the tunica adventitia or the tunica externa....

 refer in various senses to the basic meanings associated with the Latin root advenire. Typically the general intention is to convey something like: of the nature of a later addition from without, accidental, casual.

On similar principles, adventitious in medical terminology can refer to conditions acquired after birth, particularly if the cause is obscure, casual, or accidental.

In auscultation
Auscultation
Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...

 the term adventitious refers in general to any diagnostic added sound not normally to be expected in the healthy body and likely to indicate an undesirable condition. The terminology is confused, largely for historical reasons, but roughly speaking one listens for crackles and wheezes in the respiratory passages, and rubbings in pleurisy.

A wide variety of other sounds are correspondingly relevant in cardiovascular conditions, fractures, joint problems etc.

Agriculture


Adventitious presence in agriculture refers to the accidental or unintentional appearance of foreign material in a product. This usually happens in the production, harvesting, storage
Food storage
Food storage is both a traditional domestic skill and is important industrially. Food is stored by almost every human society and by many animals...

, and marketing of grains
Food grain
thumb|150px|Barleythumb|150px|LentilGrains are small, hard, dry seeds harvested for human food or animal feed Agronomists also call the plants producing such seeds grains or grain crops....

, seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s, or food products
Food processing
Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...

.

Grain and seed companies argue that virtually all shipments contain some type, and level, of adventitious material, such as weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

 material. Generally, buyers recognize that some level of adventitious material is acceptable, and foreign material limits are specified in purchase contracts.

Adventitious presence is a key issue in the debate over regulation of biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

. As more and more crops, and acres, are devoted to genetically engineered
Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...

 (GE) varieties, it becomes increasingly difficult to segregate these from GE-free varieties, which some buyers and countries demand.

In 2005, the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

was considering a proposal to require GE labeling of any food or feed product that contains more than 0.5% of material derived from genetically modified organisms.