Editing Root (section)

==Types==
{{Unreferenced section|date=March 2010}}
A true root system consists of a '''primary root''' and '''secondary roots''' (or [[lateral roots]]).
* 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]]. The main function of the fibrous root is to anchor the plant.

===Specialized===
[[File:Prop roots of Maize plant.jpg|thumb|Stilt roots of maize plant]]
[[File:Pearl Millet Adventitious root.jpg|alt=Microscope image of a ross section of a pearl millet root, a circular fluorescent blue root containing a bright blue inner region (stele) with several smaller lateral roots emerging|thumb|Cross section of an adventitous crown root of pearl millet (''Pennisetum glaucum)'']]
[[File:Adventitious roots on Odontonema aka Firespike.jpg|thumb|Roots forming above ground on a cutting of an ''Odontonema'' ("Firespike")]]
[[File:Mangroves.jpg|thumb|Aerating roots of a [[mangrove]]]]
[[File:Root tip.JPG|thumb|The growing tip of a fine root]]
[[File:Aerial root.jpg|thumb|Aerial root]]
[[File:Socratea exorriza2002 03 12.JPG|thumb|The stilt roots of ''[[Socratea exorrhiza]]'']]
[[File:Visible roots.jpg|thumb|Visible roots]]

The roots, or parts of roots, of many plant species have become specialized to serve adaptive purposes besides the two primary functions{{clarify|reason=there's no intro section|date=March 2016}}, 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]]s and pteridophytes, but also in many [[dicot]]s, such as [[clover]] (''Trifolium''), [[ivy]] (''Hedera''), [[strawberry]] (''Fragaria'') and [[willow]] (''Salix''). Most aerial roots and stilt roots are adventitious. In some conifers adventitious roots can form the largest part of the root system. Adventitious root formation is enhanced in many plant species during (partial) submergence, to increase gas exchange and storage of gases like oxygen.<ref>{{cite journal |last1=Ayi |first1=Qiaoli |last2=Zeng |first2=Bo |last3=Liu |first3=Jianhui |last4=Li |first4=Siqi |last5=van Bodegom |first5=Peter M. |last6=Cornelissen |first6=Johannes H. C. |title=Oxygen absorption by adventitious roots promotes the survival of completely submerged terrestrial plants |journal=Annals of Botany |date=October 2016 |volume=118 |issue=4 |pages=675–683 |doi=10.1093/aob/mcw051|pmid=27063366 |pmc=5055620 }}</ref> Distinct types of adventitious roots can be classified and are dependent on morphology, growth dynamics and function.<ref>{{cite journal |last1=Lin |first1=Chen |last2=Ogorek |first2=Lucas León Peralta |last3=Liu |first3=Dan |last4=Pedersen |first4=Ole |last5=Sauter |first5=Margret |date=11 January 2023 |title=A quantitative trait locus conferring flood tolerance to deepwater rice regulates the formation of two distinct types of aquatic adventitious roots |journal=New Phytologist |volume=238 |issue=4 |pages=1403–1419 |doi=10.1111/nph.18678|pmid=36519256 |doi-access=free |bibcode=2023NewPh.238.1403L }}</ref><ref>{{cite journal |last1=Maric |first1=Aida |last2=Hartman |first2=Sjon |date=11 March 2023 |title=The leaf sheath promotes prolonged flooding protection by giving rise to specialized adventitious roots |journal=New Phytologist |volume=238 |issue=4 |pages=1337–1339 |doi=10.1111/nph.18824|pmid=36905344 |doi-access=free |bibcode=2023NewPh.238.1337M }}</ref>
* '''Aerating roots''' (or '''knee root''' or '''knee''' or '''pneumatophores'''): roots rising above the ground, especially above water such as in some [[mangrove]] genera (''[[Avicennia]], [[Sonneratia]]''). 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 [[epiphyte|epiphytic]] [[orchid]]s. Many aerial roots are used to receive water and nutrient intake directly from the air – from fogs, dew or humidity in the air.<ref name="deficit">{{cite journal|last1=Nowak|first1=Edward J.|last2=Martin|first2=Craig E.| name-list-style = vanc |title=Physiological and anatomical responses to water deficits in the CAM epiphyte ''Tillandsia ionantha'' (Bromeliaceae) |journal=International Journal of Plant Sciences |date=1997 |volume=158 |issue=6 |pages=818–826 |jstor=2475361 |doi=10.1086/297495 |bibcode=1997IJPlS.158..818N |hdl=1808/9858 |hdl-access=free }}</ref> Some rely on leaf systems to gather rain or humidity and even store it in scales or pockets. Other aerial roots, such as [[mangrove]] 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]] 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.<ref name="deficit" />
*'''[[Canopy root]]s/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.<ref>{{cite journal | vauthors = Nadkarni NM | title = Canopy roots: convergent evolution in rainforest nutrient cycles | journal = Science | volume = 214 | issue = 4524 | pages = 1023–4 | date = November 1981 | pmid = 17808667 | doi = 10.1126/science.214.4524.1023 | bibcode = 1981Sci...214.1023N }}</ref>
* '''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.
* '''Contractile roots''': roots that pull bulbs or corms of [[monocot]]s, such as [[hyacinth (plant)|hyacinth]] and [[lily]], and some [[taproot]]s, such as [[dandelion]], deeper in the soil through expanding radially and contracting longitudinally. They have a wrinkled surface.<ref>{{cite book |doi=10.1201/9780203909423 |title=Plant Roots |date=2002 |isbn=978-0-203-90942-3 |editor-last1=Waisel |editor-last2=Eshel |editor-last3=Beeckman |editor-last4=Kafkafi |editor-first1=Yoav |editor-first2=Amram |editor-first3=Tom |editor-first4=Uzi |last1=Pütz |first1=Norbert |chapter=Contractile Roots |pages=975–987 }}</ref> 
* '''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]]. They are only found in [[cycad]]s.
* '''[[Dimorphic root system]]s''': roots with two distinctive forms for two separate functions
* '''[[Fine root]]s''': typically primary roots <2&nbsp;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]] (''Viscum album'') and [[dodder]].
* '''Propagative roots''': roots that form adventitious buds that develop into aboveground shoots, termed [[Basal shoot|suckers]], which form new plants, as in [[Asclepias syriaca|common milkweed (''Asclepias syriaca'')]], [[Cirsium arvense|Canada thistle (''Cirsium arvense'')]], and many others.<ref>{{cite journal|first1=Deana|last1=Namuth-Covert|first2=Amy|last2=Kohmetscher|url=https://ohiostate.pressbooks.pub/crpsoil2422t/chapter/3-3-vegetative-forms-of-reproduction/|title=3.3 Vegetative Forms of Reproduction: Modified Roots|journal=Principles of Weed Control|location=[[Montreal]]|publisher=[[Pressbooks]]|quote=Examples of plants with modified roots: Common milkweed (''Asclepias syriaca'') and Canada thistle (''Cirsium arvense'').|access-date=October 13, 2024}}</ref>
*'''Photosynthetic roots''': roots that are green and photosynthesize, providing sugar to the plant. They are similar to [[phylloclade]]s. Several orchids have these, such as ''[[Dendrophylax]]'' and ''[[Taeniophyllum]]''.
* '''[[Proteoid root]]s''' or cluster roots: dense clusters of rootlets of limited growth that develop under low [[phosphate]] or low [[iron]] conditions in [[Proteaceae]] and some plants from the following families [[Betulaceae]], [[Casuarinaceae]], [[Elaeagnaceae]], [[Moraceae]], [[Fabaceae]] and ''[[Myricaceae]]''.
* [[Root nodule|'''Root nodules''']]: roots that harbor nitrogen-fixing soil bacteria. These are often very short and rounded. Root nodules are found in virtually all [[legume]]s.
* '''Stilt roots''': adventitious support roots, common among [[mangrove]]s. They grow down from lateral branches, branching in the soil.
* '''Storage roots''': roots modified for storage of food or water, such as [[carrot]]s and [[beet]]s. They include some [[taproot]]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]]. A type of storage root distinct from taproot.