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In
vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of embryophyte, land plants ( accepted known species) that have lignin, lignified tissue (biology), tissues (the xylem) for conducting water and ...
s, 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 surface of the
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organism In biology, an organism () is any life, living system that functions as an individual entity. All organi ...
, but roots can also be aerial or aerating, that is, growing up above the ground or especially above water.


Function

The major functions of roots are
absorption of water In higher plants water and minerals are absorbed through root hairs which are in contact with soil water and from the root hairs zone a little the root tips. Active absorption Active absorption refers to the absorption of water by roots with th ...
,
plant nutrition Plant nutrition is the study of the chemical elements and Chemical compound, compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or ...
and anchoring of the plant body to the ground.


Anatomy

Root morphology is divided into four zones: the root cap, the
apical meristem The meristem is a type of tissue found in plants. It consists of undifferentiated cells (meristematic cells) capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants. These cells conti ...
, the elongation zone, and the hair. The
root cap The root cap is a type of tissue at the tip of a plant root. It is also called calyptra. Root caps contain statocytes which are involved in Gravitropism, gravity perception in plants. If the cap is carefully removed the root will grow randomly. T ...
of new roots helps the root penetrate the soil. These root caps are sloughed off as the root goes deeper creating a slimy surface that provides lubrication. The apical meristem behind the root cap produces new root cells that elongate. Then, root hairs form that absorb water and mineral nutrients from the soil. The first root in seed producing plants is the
radicle In botany, the radicle is the first part of a seedling (a growing plant embryo) to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil (the shoot emerges from the ...
, which expands from the plant embryo after seed germination. When dissected, the arrangement of the cells in a root is
root hair Root hair, or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Root ...
,
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...
, epiblem, cortex,
endodermis The endodermis is the central, innermost layer of Cortex (botany), cortex in land plants. It is a cylinder of compact living cells, the radial walls of which are impregnated with hydrophobe, hydrophobic substances (Casparian strip) to restrict ap ...
,
pericycle The pericycle is a cylinder of Ground tissue#Parenchyma, parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele (biology), stele of plants. Although it is composed of non-vascular parenchyma c ...
and, lastly, the
vascular tissue Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of embryophyte, land plants ( a ...
in the centre of a root to transport the water absorbed by the root to other places of the plant. Perhaps the most striking characteristic of roots that distinguishes them from other plant organs such as stem-branches and leaves is that roots have an ''endogenous'' origin, ''i.e.'', they originate and develop from an inner layer of the mother axis, such as
pericycle The pericycle is a cylinder of Ground tissue#Parenchyma, parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele (biology), stele of plants. Although it is composed of non-vascular parenchyma c ...
. In contrast, stem-branches and leaves are ''exogenous'', ''i.e.'', they start to develop from the cortex, an outer layer. In response to the concentration of nutrients, roots also synthesise
cytokinin Cytokinins (CK) are a class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in Cell (biology), cell growth and cellular differentiation, differentiation, but also affect apical ...
, which acts as a signal as to how fast the shoots can grow. Roots often function in storage of food and nutrients. The roots of most vascular plant species enter into symbiosis with certain
fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
to form
mycorrhiza   A mycorrhiza (from Ancient Greek, Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiosis, symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role ...
e, and a large range of other organisms including
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 micrometre The micrometre (Amer ...
also closely associate with roots.


Root system architecture (RSA)


Definition

In its simplest form, the term root system architecture (RSA) refers to the spatial configuration of a plant's root system. This system can be extremely complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil and the availability of nutrients. Root architecture plays the important role of providing a secure supply of nutrients and water as well as anchorage and support. The configuration of root systems serves to structurally support the plant, compete with other plants and for uptake of nutrients from the soil. Roots grow to specific conditions, which, if changed, can impede a plant's growth. For example, a root system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment, such as seasonal changes.


Terms and components

The main terms used to classify the architecture of a root system are: All components of the root architecture are regulated through a complex interaction between genetic responses and responses due to environmental stimuli. These developmental stimuli are categorised as intrinsic, the genetic and nutritional influences, or extrinsic, the environmental influences and are interpreted by
signal transduction pathways Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a biochemical cascade, series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately re ...
. Extrinsic factors affecting root architecture include gravity, light exposure, water and oxygen, as well as the availability or lack of nitrogen, phosphorus, sulphur, aluminium and sodium chloride. The main hormones (intrinsic stimuli) and respective pathways responsible for root architecture development include:


Growth

Early root growth is one of the functions of the apical meristem located near the tip of the root. The meristem cells more or less continuously divide, producing more meristem,
root cap The root cap is a type of tissue at the tip of a plant root. It is also called calyptra. Root caps contain statocytes which are involved in Gravitropism, gravity perception in plants. If the cap is carefully removed the root will grow randomly. T ...
cells (these are sacrificed to protect the meristem), and undifferentiated root cells. The latter become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium. Gradually these cells differentiate and mature into specialized cells of the root tissues. Growth from apical meristems is known as primary growth, which encompasses all elongation. Secondary growth encompasses all growth in diameter, a major component 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 plant, herbaceous plants that die back to t ...
tissues and many nonwoody plants. For example, storage roots of
sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant that belongs to the Convolvulus, bindweed or morning glory family (biology), family, Convolvulaceae. Its large, starchy, sweet-tasting tuberous roots are used as a r ...
have secondary growth but are not woody. Secondary growth occurs at the lateral meristems, namely the
vascular cambium The vascular cambium is the main growth Tissue (biology), 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 produc ...
and
cork cambium Cork cambium (pl. cambia or cambiums) is a tissue found in many vascular plants as a part of the epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, ...
. The former forms secondary xylem and secondary phloem, while the latter forms the periderm. In plants with secondary growth, the vascular cambium, originating between the xylem and the phloem, forms a
cylinder A cylinder (from ) has traditionally been a Solid geometry, three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a Prism (geometry), prism with a circle as its base. A cylinder ...
of tissue along 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 structure * Stipe (mycology), the stem of a mushro ...
and root. The vascular cambium forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, and those on the outside forming secondary phloem cells. As secondary xylem accumulates, the "girth" (lateral dimensions) of the stem and root increases. As a result, tissues beyond the secondary phloem including the epidermis and cortex, in many cases tend to be pushed outward and are eventually "sloughed off" (shed). At this point, the cork cambium begins to form the periderm, consisting of protective
cork Cork or CORK may refer to: Materials * Cork (material) Cork is an Permeability (earth sciences), impermeable buoyancy, buoyant material, the Cork cambium, phellem layer of bark (botany), bark tissue that is harvested for commercial use prima ...
cells. The walls of cork cells contains
suberin Suberin, cutin and lignins are complex, higher plant Epidermis (botany), epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids ...
thickenings, which is an extra cellular complex biopolymer. The suberin thickenings functions by providing a physical barrier, protection against pathogens and by preventing water loss from the surrounding tissues. In addition, it also aids the process of wound healing in plants. It is also postulated that suberin could be a component of the apoplastic barrier (present at the outer cell layers of roots) which prevents toxic compounds from entering the root and reduces radial oxygen loss (ROL) from the
aerenchyma Aerenchyma or aeriferous parenchyma or lacunae, is a modification of the Ground tissue, parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between t ...
during waterlogging. In roots, the cork cambium originates in the
pericycle The pericycle is a cylinder of Ground tissue#Parenchyma, parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele (biology), stele of plants. Although it is composed of non-vascular parenchyma c ...
, a component of the vascular cylinder. The vascular cambium produces new layers of secondary xylem annually. The xylem vessels are dead at maturity (in some) but are responsible for most water transport through the vascular tissue in stems and roots. Tree roots usually grow to three times the diameter of the branch spread, only half of which lie underneath the trunk and canopy. The roots from one side of a tree usually supply nutrients to the foliage on the same side. Some families however, such as
Sapindaceae The Sapindaceae are a family (biology), family of flowering plants in the order Sapindales known as the soapberry family. It contains 138 genera and 1858 accepted species. Examples include Aesculus, horse chestnut, maples, ackee and lychee. The ...
(the
maple ''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since h ...
family), show no correlation between root location and where the root supplies nutrients on the plant.


Regulation

There is a correlation of roots using the process of plant perception to sense their physical environment to grow, including the sensing of light, and physical barriers. Plants also sense gravity and respond through auxin pathways, resulting in
gravitropism Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general featu ...
. Over time, roots can crack foundations, snap water lines, and lift sidewalks. Research has shown that roots have ability to recognize 'self' and 'non-self' roots in same soil environment. The correct environment of
air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...
, mineral
nutrients A nutrient is a Chemical substance, substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungus, fungi, and protists. Nutrients can be incorporated into cells for me ...
and
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
directs plant roots to grow in any direction to meet the plant's needs. Roots will shy or shrink away from dry or other poor soil conditions.
Gravitropism Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general featu ...
directs roots to grow downward at
germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an flowering plant, angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spor ...
, the growth mechanism of plants that also causes the shoot to grow upward. Different types of roots such as primary, seminal, lateral and crown are maintained at different gravitropic setpoint angles i.e. the direction in which they grow. Recent research show that root angle in cereal crops such as barley and wheat is regulated by a novel gene called Enhanced Gravitropism 1 (EGT1). Research indicates that plant roots growing in search of productive nutrition can sense and avoid soil compaction through diffusion of the gas
ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon-carbon double ...
.


Shade avoidance response

In order to avoid shade, plants utilize a shade avoidance response. When a plant is under dense vegetation, the presence of other vegetation nearby will cause the plant to avoid lateral growth and experience an increase in upward shoot, as well as downward root growth. In order to escape shade, plants adjust their root architecture, most notably by decreasing the length and amount of lateral roots emerging from the primary root. Experimentation of mutant variants of
Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter an ...
found that plants sense the Red to Far Red light ratio that enters the plant through photoreceptors known as
phytochrome Phytochromes are a class of photoreceptor in plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not ...
s. Nearby plant leaves will absorb red light and reflect far- red light which will cause the ratio red to far red light to lower. The phytochrome PhyA that senses this Red to Far Red light ratio is localized in both the root system as well as the shoot system of plants, but through knockout mutant experimentation, it was found that root localized PhyA does not sense the light ratio, whether directly or axially, that leads to changes in the lateral root architecture. Research instead found that shoot localized PhyA is the phytochrome responsible for causing these architectural changes of the lateral root. Research has also found that phytochrome completes these architectural changes through the manipulation of auxin distribution in the root of the plant. When a low enough Red to Far Red ratio is sensed by PhyA, the phyA in the shoot will be mostly in its active form. In this form, PhyA stabilize the
transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding to ...
HY5 causing it to no longer be degraded as it is when phyA is in its inactive form. This stabilized transcription factor is then able to be transported to the roots of the plant through the
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 ...
, where it proceeds to induce its own transcription as a way to amplify its signal. In the roots of the plant HY5 functions to inhibit an auxin response factor known as ARF19, a response factor responsible for the translation of PIN3 and LAX3, two well known auxin transporting
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabo ...
s. Thus, through manipulation of ARF19, the level and activity of
auxin Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...
transporters PIN3 and LAX3 is inhibited. Once inhibited, auxin levels will be low in areas where lateral root emergence normally occurs, resulting in a failure for the plant to have the emergence of the lateral root primordium through the root
pericycle The pericycle is a cylinder of Ground tissue#Parenchyma, parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele (biology), stele of plants. Although it is composed of non-vascular parenchyma c ...
. With this complex manipulation of Auxin transport in the roots, lateral root emergence will be inhibited in the roots and the root will instead elongate downwards, promoting vertical plant growth in an attempt to avoid shade. Research of Arabidopsis has led to the discovery of how this auxin mediated root response works. In an attempt to discover the role that
phytochrome Phytochromes are a class of photoreceptor in plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not ...
plays in lateral root development, Salisbury et al. (2007) worked with ''
Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter an ...
'' grown on agar plates. Salisbury et al. used wild type plants along with varying protein knockout and gene knockout Arabidopsis mutants to observe the results these mutations had on the root architecture, protein presence, and gene expression. To do this, Salisbury et al. used GFP fluorescence along with other forms of both macro and microscopic imagery to observe any changes various mutations caused. From these research, Salisbury et al. were able to theorize that shoot located phytochromes alter auxin levels in roots, controlling lateral root development and overall root architecture. In the experiments of van Gelderen et al. (2018), they wanted to see if and how it is that the shoot of ''
Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter an ...
'' alters and affects root development and root architecture. To do this, they took Arabidopsis plants, grew them in agar gel, and exposed the roots and shoots to separate sources of light. From here, they altered the different wavelengths of light the shoot and root of the plants were receiving and recorded the lateral root density, amount of lateral roots, and the general architecture of the lateral roots. To identify the function of specific photoreceptors, proteins, genes, and hormones, they utilized various Arabidopsis knockout mutants and observed the resulting changes in lateral roots architecture. Through their observations and various experiments, van Gelderen et al. were able to develop a mechanism for how root detection of Red to Far-red light ratios alter lateral root development.


Types

A true root system consists of a primary root and secondary roots (or
lateral roots Lateral roots, emerging from the pericycle The pericycle is a cylinder of Ground tissue#Parenchyma, parenchyma or sclerenchyma cells that lies just inside the endodermis and is the outer most part of the stele (biology), stele of plants. Althoug ...
). * the diffuse root system: the primary root is not dominant; the whole root system is fibrous and branches in all directions. Most common in
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
. The main function of the fibrous root is to anchor the plant.


Specialized

The roots, or parts of roots, of many plant species have become specialized to serve adaptive purposes besides the two primary functions, described in the introduction. * Adventitious roots arise out-of-sequence from the more usual root formation of branches of a primary root, and instead originate from the stem, branches, leaves, or old woody roots. They commonly occur in
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
s and pteridophytes, but also in many
dicot The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...
s, such as
clover Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species In biology, a species is the basic unit of Taxonomy (biology), classification and a ...
(''Trifolium''), ivy (''Hedera''),
strawberry The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid species of the genus ''Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The f ...
(''Fragaria'') and
willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise List of Salix species, around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found ...
(''Salix''). Most aerial roots and stilt roots are adventitious. In some conifers adventitious roots can form the largest part of the root system. * Aerating roots (or knee root or knee or pneumatophores): roots rising above the ground, especially above water such as in some
mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
genera ('' Avicennia,
Sonneratia ''Sonneratia'' is a genus of plants in the Family (biology), family Lythraceae. Formerly the Sonneratia were placed in a family called Sonneratiaceae which included both the ''Sonneratia'' and the ''Duabanga'', but these two are now placed in ...
''). In some plants like ''Avicennia'' the erect roots have a large number of breathing pores for exchange of gases. * Aerial roots: roots entirely above the ground, such as in ivy (''Hedera'') or in
epiphytic 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 Phorophy ...
orchid Orchids are plants that belong to the Family (biology), family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest fam ...
s. Many aerial roots are used to receive water and nutrient intake directly from the air – from fogs, dew or humidity in the air. Some rely on leaf systems to gather rain or humidity and even store it in scales or pockets. Other aerial roots, such as
mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
aerial roots, are used for aeration and not for water absorption. Other aerial roots are used mainly for structure, functioning as prop roots, as in
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...
or anchor roots or as the trunk in strangler fig. In some Epiphytes – plants living above the surface on other plants, aerial roots serve for reaching to water sources or reaching the surface, and then functioning as regular surface roots. * Canopy roots/arboreal roots: roots that form when tree branches support mats of epiphytes and detritus, which hold water and nutrients in the canopy. They grow out into these mats, likely to utilize the available nutrients and moisture. * Contractile roots: roots that pull bulbs or corms of
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
s, such as hyacinth and
lily ''Lilium'' () is a genus of Herbaceous plant, herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in mu ...
, and some
taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...
s, such as
dandelion ''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and Nor ...
, deeper in the soil through expanding radially and contracting longitudinally. They have a wrinkled surface. * Coarse roots: roots that have undergone secondary thickening and have a woody structure. These roots have some ability to absorb water and nutrients, but their main function is transport and to provide a structure to connect the smaller diameter, fine roots to the rest of the plant. * Dimorphic root systems: roots with two distinctive forms for two separate functions * Fine roots: typically primary roots <2 mm diameter that have the function of water and nutrient uptake. They are often heavily branched and support mycorrhizas. These roots may be short lived, but are replaced by the plant in an ongoing process of root 'turnover'. * Haustorial roots: roots of parasitic plants that can absorb water and nutrients from another plant, such as in
mistletoe Mistletoe is the common name for obligate parasite, obligate parasitic plant, hemiparasitic plants in the Order (biology), order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which the ...
(''Viscum album'') and
dodder ''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
. * Propagative roots: roots that form adventitious buds that develop into aboveground shoots, termed suckers, which form new plants, as in
Canada thistle ''Cirsium arvense'' is a perennial species of flowering plant in the family Asteraceae, native throughout Europe and western Asia, northern Africa and widely introduced species, introduced elsewhere.Joint Nature Conservation Committee''Cirsium a ...
,
cherry A cherry is the fruit of many plants of the genus ''Prunus'', and is a fleshy drupe (stone fruit). Commercial cherries are obtained from cultivars of several species, such as the sweet ''Prunus avium'' and the sour ''Prunus cerasus''. The nam ...
and many others. * Proteoid roots or cluster roots: dense clusters of rootlets of limited growth that develop under low
phosphate In chemistry, a phosphate is an anion, salt (chemistry), salt, functional group or ester derived from a phosphoric acids and phosphates, phosphoric acid. It most commonly means orthophosphate, a derivative of phosphoric acid, orthophosphoric a ...
or low
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundance ...
conditions in
Proteaceae The Proteaceae form a family (biology), family of flowering plants predominantly distributed in the Southern Hemisphere. The family comprises 83 genus, genera with about 1,660 known species. Together with the Platanaceae and Nelumbonaceae, they ...
and some plants from the following families
Betulaceae Betulaceae, the birch family, includes six genera of deciduous nut (fruit), nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams, Ostryopsis, hazel-hornbeam, and Ostrya, hop-hornbeams numbering a total of 167 species. ...
,
Casuarinaceae The Casuarinaceae are a family (biology), family of dicotyledonous flowering plants placed in the order Fagales, consisting of four genera and 91 species of trees and shrubs native to eastern Africa, Australia, Southeast Asia, Malesia, Papuasia, ...
, Elaeagnaceae,
Moraceae The Moraceae — often called the mulberry family or fig family — are a family of flowering plants comprising about 38 genera and over 1100 species. Most are widespread in tropical and subtropical regions, less so in temperate climates; however ...
,
Fabaceae The Fabaceae or Leguminosae,International Code of Nomenc ...
and
Myricaceae The Myricaceae are a small family of dicotyledonous shrubs and small trees in the order Fagales. There are three genera in the family, although some botanists separate many species from ''Myrica'' into a fourth genus ''Morella''. About 55 specie ...
. * Stilt roots: adventitious support roots, common among
mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
s. They grow down from lateral branches, branching in the soil. * Storage roots: roots modified for storage of food or water, such as
carrot The carrot (''Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the Daucus carota, wild carrot, ''Daucus ...
s and
beet The beetroot is the taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plant ...
s. They include some
taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...
s and tuberous roots. * Structural roots: large roots that have undergone considerable secondary thickening and provide mechanical support to woody plants and trees. * Surface roots: roots that proliferate close below the soil surface, exploiting water and easily available nutrients. Where conditions are close to optimum in the surface layers of soil, the growth of surface roots is encouraged and they commonly become the dominant roots. * Tuberous roots: fleshy and enlarged lateral roots for food or water storage, e.g.
sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant that belongs to the Convolvulus, bindweed or morning glory family (biology), family, Convolvulaceae. Its large, starchy, sweet-tasting tuberous roots are used as a r ...
. A type of storage root distinct from taproot. *Photosynthetic roots: roots that are green and photosynthesize, providing sugar to the plant. They are similar to phylloclades. Several orchids have these, such as '' Dendrophylax'' and '' Taeniophyllum''. * Root nodules: roots that harbor nitrogen-fixing soil bacteria. These are often very short and rounded. Root nodules are found in virtually all
legumes A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock for ...
. *Coralloid roots: similar to root nodules, these provide nitrogen to the plant. They are often larger than nodules, branched, and located at or near the soil surface, and harbor nitrogen-fixing
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
. They are only found in
cycads Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...
.


Depths

The distribution of vascular plant roots within soil depends on plant form, the spatial and temporal availability of water and nutrients, and the physical properties of the soil. The deepest roots are generally found in deserts and temperate coniferous forests; the shallowest in tundra, boreal forest and temperate grasslands. The deepest observed living root, at least 60 metres below the ground surface, was observed during the excavation of an open-pit mine in Arizona, USA. Some roots can grow as deep as the tree is high. The majority of roots on most plants are however found relatively close to the surface where nutrient availability and aeration are more favourable for growth. Rooting depth may be physically restricted by rock or compacted soil close below the surface, or by anaerobic soil conditions.


Records


Evolutionary history

The fossil record of roots—or rather, infilled voids where roots rotted after death—spans back to the late
Silurian The Silurian ( ) is a period (geology), geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (annum, Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortes ...
, about 430 million years ago. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows. They can be discriminated using a range of features. The evolutionary development of roots likely happened from the modification of shallow
rhizomes In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary bud ...
(modified horizontal stems) which anchored primitive vascular plants combined with the development of filamentous outgrowths (called
rhizoid Rhizoids are protuberances that extend from the lower epidermis (botany), epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular plant, vascular land plants. Similar structures are formed ...
s) which anchored the plants and conducted water to the plant from the soil.


Environmental interactions

Light has been shown to have some impact on roots, but its not been studied as much as the effect of light on other plant systems. Early research in the 1930s found that light decreased the effectiveness of
Indole-3-acetic acid Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists. IAA is a derivative of indole, con ...
on adventitious root initiation. Studies of the pea in the 1950s shows that lateral root formation was inhibited by light, and in the early 1960s researchers found that light could induce positive gravitropic responses in some situations. The effects of light on root elongation has been studied for
monocotyledonous Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
and
dicotyledonous The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...
plants, with the majority of studies finding that light inhibited root elongation, whether pulsed or continuous. Studies of ''
Arabidopsis ''Arabidopsis'' (rockcress) is a genus in the family Brassicaceae. They are small flowering plants related to cabbage and Mustard plant, mustard. This genus is of great interest since it contains thale cress (''Arabidopsis thaliana''), one of th ...
'' in the 1990s showed negative phototropism and inhibition of the elongation of root hairs in light sensed by phyB. Certain plants, namely
Fabaceae The Fabaceae or Leguminosae,International Code of Nomenc ...
, form
root nodules Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known a ...
in order to associate and form a symbiotic relationship with nitrogen-fixing bacteria called
rhizobia Rhizobia are diazotrophic bacteria that Nitrogen fixation, fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant Host (biology), host; they cannot i ...
. Owing to the high energy required to fix nitrogen from the atmosphere, the bacteria take carbon compounds from the plant to fuel the process. In return, the plant takes nitrogen compounds produced from ammonia by the bacteria. Soil temperature is a factor that effects root initiation and length. Root length is usually impacted more dramatically by temperature than overall mass, where cooler temperatures tend to cause more lateral growth because downward extension is limited by cooler temperatures at subsoil levels. Needs vary by plant species, but in temperate regions cool temperatures may limit root systems. Cool temperature species like
oats The oat (''Avena sativa''), sometimes called the common oat, is a species of Cereal, cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). While oats are suitable for h ...
,
rapeseed Rapeseed (''Brassica napus ''subsp.'' napus''), also known as rape, or oilseed rape, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturally contains a ...
, rye,
wheat Wheat is a Poaceae, grass widely Agriculture, cultivated for its seed, a cereal grain that is a worldwide staple food. The Taxonomy of wheat, many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat ...
fare better in lower temperatures than summer annuals like
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...
and
cotton Cotton is a soft, fluffy Staple (textiles), staple fiber that grows in a wikt:boll, boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose ...
. Researchers have found that plants like cotton develop wider and shorter
taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...
s in cooler temperatures. The first root originating from the seed usually has a wider diameter than root branches, so smaller root diameters are expected if temperatures increase root initiation. Root diameter also decreases when the root elongates.Encyclopedia of Soil Science
/ref>


Plant interactions

Plants can interact with one another in their environment through their root systems. Studies have demonstrated that plant-plant interaction occurs among root systems via the soil as a medium. Researchers have tested whether plants growing in ambient conditions would change their behavior if a nearby plant was exposed to drought conditions. Since nearby plants showed no changes in
stoma In botany, a stoma (from Greek language, Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. ...
tal aperture researchers believe the drought signal spread through the roots and soil, not through the air as a volatile chemical signal.


Soil interactions

Soil microbiota can suppress both disease and beneficial root symbionts (mycorrhizal fungi are easier to establish in sterile soil). Inoculation with soil bacteria can increase internode extension, yield and quicken flowering. The migration of bacteria along the root varies with natural soil conditions. For example, research has found that the root systems of wheat seeds inoculated with ''
Azotobacter ''Azotobacter'' is a genus of usually Motility, motile, oval or spherical bacteria that form thick-walled cysts (and also has hard crust) and may produce large quantities of capsular Mucus, slime. They are aerobic, free-living soil Microorganism ...
'' showed higher populations in soils favorable to Azotobacter growth. Some studies have been unsuccessful in increasing the levels of certain microbes (such as '' P. fluorescens'') in natural soil without prior sterilization. Grass root systems are beneficial at reducing
soil erosion Soil erosion is the denudation or wearing away of the Topsoil, upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, Atmosphere of Ea ...
by holding the soil together.
Perennial A perennial plant or simply perennial is a plant that lives more than two years. The term (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annual pl ...
grasses that grow wild in rangelands contribute organic matter to the soil when their old roots decay after attacks by beneficial
fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
,
protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of Unicellular organism, single-celled eukaryotes, either free-living or Parasitism, parasitic, that feed on organic matter such as other microorganisms or o ...
, bacteria, insects and worms release nutrients. Scientists have observed significant diversity of the microbial cover of roots at around 10 percent of three week old root segments covered. On younger roots there was even low coverage, but even on 3-month-old roots the coverage was only around 37%. Before the 1970s, scientists believed that the majority of the root surface was covered by microorganisms.


Nutrient absorption

Researchers studying
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...
seedlings found that calcium absorption was greatest in the apical root segment, and potassium at the base of the root. Along other root segments absorption was similar. Absorbed potassium is transported to the root tip, and to a lesser extent other parts of the root, then also to the shoot and grain. Calcium transport from the apical segment is slower, mostly transported upward and accumulated in stem and shoot. Researchers found that partial deficiencies of K or P did not change the
fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an B ...
composition of phosphatidyl choline in '' Brassica napus L.'' plants. Calcium deficiency did, on the other hand, lead to a marked decline of
polyunsaturated In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...
compounds that would be expected to have negative impacts for integrity of the plant
membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...
, that could effect some properties like its permeability, and is needed for the ion uptake activity of the root membranes.


Economic importance

The term root crops refers to any edible underground plant structure, but many root crops are actually stems, such as
potato The potato is a starch#Food, starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae. Wild potato species can be fo ...
tubers. Edible roots include
cassava ''Manihot esculenta'', common name, commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively ...
,
sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant that belongs to the Convolvulus, bindweed or morning glory family (biology), family, Convolvulaceae. Its large, starchy, sweet-tasting tuberous roots are used as a r ...
,
beet The beetroot is the taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plant ...
,
carrot The carrot (''Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the Daucus carota, wild carrot, ''Daucus ...
,
rutabaga Rutabaga (; North American English) or swede (British English and some Commonwealth English) is a root vegetable, a form of ''Brassica napus'' (which also includes rapeseed). Other names include Swedish turnip, neep (Scots), and Turnip (termin ...
,
turnip The turnip or white turnip (''Brassica rapa'' subsp. ''rapa'') is a root vegetable commonly grown in temperate climates worldwide for its white, fleshy taproot. The word ''turnip'' is a compound (linguistics), compound of ''turn'' as in turned/r ...
,
parsnip The parsnip ('' Pastinaca sativa'') is a root vegetable Root vegetables are underground plant parts eaten by humans as food. Although botany distinguishes true roots (such as taproots and tuberous roots) from non-roots (such as bulbs, corm ...
,
radish The radish (''Raphanus raphanistrum'' subsp. ''sativus'') is an Eating, edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman Empire, Roman times. Radishes are grown and consumed throughout the world, be ...
, yam and
horseradish Horseradish (''Armoracia rusticana'', syn. ''Cochlearia armoracia'') is a perennial plant of the family Brassicaceae (which also includes Mustard plant, mustard, wasabi, broccoli, cabbage, and radish). It is a root vegetable, cultivated and us ...
. Spices obtained from roots include
sassafras ''Sassafras'' is a genus of three Extant taxon, extant and one extinct species of deciduous trees in the family Lauraceae, native to eastern North America and eastern Asia.Wolfe, Jack A. & Wehr, Wesley C. 1987. The sassafras is an ornamental tre ...
,
angelica ''Angelica'' is a genus of about 60 species of tall biennial and perennial herbs in the family Apiaceae, native to temperate and subarctic regions of the Northern Hemisphere, reaching as far north as Iceland, Lapland, and Greenland ...
, sarsaparilla and
licorice Liquorice (British English) or licorice (American English) ( ; also ) is the common name of ''Glycyrrhiza glabra'', a flowering plant of the bean family Fabaceae, from the root of which a sweet, aromatic flavouring can be extracted. The liqu ...
.
Sugar beet A sugar beet is a plant whose root contains a high concentration of sucrose and which is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together wit ...
is an important source of sugar. Yam roots are a source of
estrogen Estrogen or oestrogen is a category of sex steroid, sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogeny (biology), endogenous estrogens th ...
compounds used in
birth control pill The combined oral contraceptive pill (COCP), often referred to as the birth control pill or colloquially as "the pill", is a type of birth control Birth control, also known as contraception, anticonception, and fertility control, is the ...
s. The fish
poison Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...
and
insecticide Insecticides are substances used to kill insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chit ...
rotenone Rotenone is an odorless, colorless, crystalline isoflavone used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the seeds and stems of several plants, such as the jicama vine plant, and the roots of several member ...
is obtained from roots of '' Lonchocarpus'' spp. Important medicines from roots are
ginseng Ginseng () is the root of plants in the genus ''Panax'', such as Korean ginseng (''Panax ginseng, P. ginseng''), South China ginseng (''Panax notoginseng, P. notoginseng''), and American ginseng (''American ginseng, P. quinquefolius''), typically ...
, aconite,
ipecac Syrup of ipecac (), or simply ipecac, is a drug that was once widely used as an expectorant (in low doses) and a rapid-acting emetic (in higher doses). It is obtained from the dried rhizome and roots of the ipecacuanha plant (''Carapichea ipecac ...
,
gentian ''Gentiana'' is a genus of flowering plants belonging to the gentian family (biology), family (Gentianaceae), the tribe Gentianeae, and the Monophyly, monophyletic subtribe Gentianinae. With about 400 species it is considered a large genus. The ...
and
reserpine Reserpine is a drug that is used for the treatment of high blood pressure, usually in combination with a thiazide diuretic or vasodilator. Large clinical trials have shown that combined treatment with reserpine plus a thiazide diuretic reduces ...
. Several legumes that have nitrogen-fixing root nodules are used as green manure crops, which provide nitrogen fertilizer for other crops when plowed under. Specialized
bald cypress ''Taxodium distichum'' (bald cypress, swamp cypress; french: cyprès chauve; ''cipre'' in Louisiana_French, Louisiana) is a deciduous Pinophyta, conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, ...
roots, termed knees, are sold as souvenirs, lamp bases and carved into folk art. Native Americans used the flexible roots of
white spruce White spruce is a common name for several species of spruce (''Picea'') and may refer to: Tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondar ...
roots can heave and destroy
concrete Concrete is a composite material composed of fine and coarse construction aggregate, aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after wa ...
sidewalks and crush or clog buried pipes.Zahniser, David (February 21, 2008
"City to pass the bucks on sidewalks?"
''
Los Angeles Times The ''Los Angeles Times'' (abbreviated as ''LA Times'') is a daily newspaper A newspaper is a Periodical literature, periodical publication containing written News, information about current events and is often typed in black ink with a ...
''
The aerial roots of strangler fig have damaged ancient Mayan
temple A temple (from the Latin ) is a building reserved for spiritual rituals and activities such as prayer and sacrifice. Religions which erect temples include Christianity (whose temples are typically called church (building), churches), Hindui ...
s in
Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. Cen ...
and the temple of
Angkor Wat Angkor Wat (; km, អង្គរវត្ត, "City/Capital of Temples") is a temple complex in Cambodia and is the largest religious monument in the world, on a site measuring . Originally constructed as a Hinduism, Hindu temple dedicated ...
in
Cambodia Cambodia (; also Kampuchea ; km, កម្ពុជា, Romanization of Khmer#UNGEGN, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an ar ...
. Trees stabilize soil on a slope prone to
landslides Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
. The
root hair Root hair, or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Root ...
s work as an anchor on the soil. Vegetative propagation of plants via cuttings depends on adventitious root formation. Hundreds of millions of plants are propagated via cuttings annually including
chrysanthemum Chrysanthemums (), sometimes called mums or chrysanths, are flowering plants of the genus ''Chrysanthemum'' in the family (biology), family Asteraceae. They are native plant, native to East Asia and northeastern Europe. Most species originate ...
,
poinsettia The poinsettia ( or ) (''Euphorbia pulcherrima'') is a commercially important flowering plant species of the diverse spurge family Euphorbiaceae. Indigenous to Mexico and Central America, the poinsettia was first described by Europeans in 1834 ...
,
carnation ''Dianthus caryophyllus'' (), commonly known as the carnation or clove pink, is a species of ''Dianthus ''Dianthus'' () is a genus of about 340 species of flowering plants in the family (biology), family Caryophyllaceae, native plant, nati ...
, ornamental
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 and many
houseplants A houseplant, sometimes known as a pot plant, potted plant, or an indoor plant, is an Ornamental plant, ornamental plant that is grown indoors. As such, they are found in places like House, residences and offices, mainly for decorative purposes. C ...
. Roots can also protect the environment by holding the soil to reduce soil erosion. This is especially important in areas such as
sand dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...
.


See also

*
Absorption of water In higher plants water and minerals are absorbed through root hairs which are in contact with soil water and from the root hairs zone a little the root tips. Active absorption Active absorption refers to the absorption of water by roots with th ...
* Cypress knee * Drought rhizogenesis * Fibrous root system *
Mycorrhiza   A mycorrhiza (from Ancient Greek, Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiosis, symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role ...
– root symbiosis in which individual hyphae extending from the mycelium of a fungus colonize the roots of a host plant. * Mycorrhizal network *
Plant physiology Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (bio ...
*
Rhizosphere The rhizosphere is the narrow region of soil or Substrate (biology), substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Pore space in soil, Soil pores in the rhizosphere can ...
– region of soil around the root influenced by root secretions and microorganisms present *
Root cutting A plant cutting is a piece of a plant that is used in horticulture for vegetative reproduction, vegetative (asexual) plant propagation, propagation. A piece of the Plant stem, stem or root of the source plant is placed in a suitable medium such as ...
* Rooting powder *
Stolon In biology, stolons (from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are ...
* Tanada effect *
Taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...


References


Further reading

* * * * * * * * *


External links


Botany – University of Arkansas at Little Rock
* {{Authority control