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{{Short description|Part of plant root}} |
{{Short description|Part of plant root}} |
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[[File:NSRW Root-Tip.png|thumb|Root tip, showing young root hairs]]'''Root hairs''' 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 hair cells improve plant water absorption by increasing root surface area to volume ratio which allows the root hair cell to take in more water. The large [[vacuole]] inside root hair cells makes this intake much more efficient. Root hairs are also important for nutrient uptake as they are main interface between plants and [[Mycorrhiza|mycorrhizal fungi]]. |
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[[File:NSRW Root-Tip.png|thumb|Drawing of [[root tip]], showing young root hairs]] |
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{{copy edit|date=November 2021}} |
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'''Root hair''', or '''absorbent hairs''', are tubular outgrowths of an epidermal cell of a root, a hair-forming cell on the [[Epidermis (botany)|epidermis]] of a [[plant root]]. These structures are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, also called the zone of differentiation<ref>https://www.colby.edu/biology/BI237/roots.pdf</ref> of the root. Just prior to and during root hair cell development, there is elevated [[phosphorylase]] activity.<ref>{{Cite journal|last1=Dosier|first1=Larry W.|last2=Riopel|first2=J. L.|title=Differential Enzyme Activity During Trichoblast Differentiation in Elodea Canadensis|journal=American Journal of Botany|volume=64|issue=9|pages=1049–1056|language=en|doi=10.1002/j.1537-2197.1977.tb10794.x|year=1977}}</ref> {{non sequitur|date=November 2021 |reason=relevance unclear to overall explanation of root hair structure/function }} Plants absorb water through the roots from the soil by bulk flow{{Citation needed|date=April 2021}}. Root hair cells are adapted to this process by increasing root surface area for the purpose of taking in more water. The large vacuole inside root hair cells makes this intake much more efficient{{Citation needed|date=April 2021}}. |
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==Function== |
==Function== |
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The function of all root hairs is to collect water and mineral [[nutrient]]s in the soil to be sent throughout the plant. In roots, most water absorption happens through the root hairs. The length of root hairs allows them to penetrate between soil particles and prevents harmful bacterial organisms from entering the plant through the xylem vessels.<ref>{{Cite web|title=Water Balance in Plants|url=https://thewonderofscience.com/water-balance-in-plants|access-date=2021-11-16|website=The Wonder of Science|language=en-US}}</ref> Increasing the surface area of these hairs makes plants more efficient in absorbing nutrients and interacting with microbes.<ref>{{Cite journal|title=Root Hairs|journal=The Arabidopsis Book|volume=1|pages=e0060|pmc=3243358|doi=10.1199/tab.0060|pmid=22303213|year=2002|last1=Grierson|first1=C.|last2=Schiefelbein|first2=J.}}</ref> As root hair cells do not carry out [[photosynthesis]], they do not contain [[chloroplast]]s. |
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Cross-section of root hair cell: a roughly rectangular shape with a long, thin tail extending to the right and a nucleus at the top left. This happens because the water in the soil has a higher water potential than the cytoplasm of the root hairs. The function of root hairs is to collect water and mineral [[nutrient]]s that are present in the soil and take this solution up through the roots to the rest of the plant. As root hair cells do not carry out [[photosynthesis]], they do not contain [[chloroplasts]]. |
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| ⚫ | Root hairs form an important surface as they are needed to [[Absorption of water|absorb]] most of the water and nutrients needed for the plant. They are also directly involved in the formation of [[root nodule]]s in [[Fabaceae|legume]] plants. The root hairs curl around the bacteria, which allows for the formation of an infection thread into the dividing cortical cells to form the nodule.<ref>{{Cite journal|last1=Mergaert|first1=Peter|last2=Uchiumi|first2=Toshiki|last3=Alunni|first3=Benoît|last4=Evanno|first4=Gwénaëlle|last5=Cheron|first5=Angélique|last6=Catrice|first6=Olivier|last7=Mausset|first7=Anne-Elisabeth|last8=Barloy-Hubler|first8=Frédérique|last9=Galibert|first9=Francis|last10=Kondorosi|first10=Adam|last11=Kondorosi|first11=Eva|date=28 March 2006|title=Eukaryotic control on bacterial cell cycle and differentiation in the Rhizobium–legume symbiosis|journal=Proceedings of the National Academy of Sciences|language=en|volume=103|issue=13|pages=5230–5235|bibcode=2006PNAS..103.5230M|doi=10.1073/pnas.0600912103|pmc=1458823|pmid=16547129|doi-access=free}}</ref> |
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[[File:Tomato root hairs.jpg|thumb|Calcofluor White confocal fluorescent image of developing tomato root]] |
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[[File:Arabidopsis root hairs.jpg|thumb|Confocal fluorescence image of Arabidopsis root hairs]] |
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| ⚫ | Having a large surface area, the [[active uptake]] of water and minerals through root hairs is highly efficient. Root hair cells also secrete acids (e.g., [[Malic acid|malic]] and [[Citric acid|citric]] acid), which solubilize minerals by changing their [[oxidation state]], making the ions easier to absorb.<ref>{{Cite journal|last1=Gerke|first1=Jörg|last2=Römer|first2=Wilhelm|last3=Jungk|first3=Albrecht|date=1994|title=The excretion of citric and malic acid by proteoid roots of Lupinus albus L.; effects on soil solution concentrations of phosphate, iron, and aluminum in the proteoid rhizosphere in samples of an oxisol and a luvisol|journal=Zeitschrift für Pflanzenernährung und Bodenkunde|language=en|volume=157|issue=4|pages=289–294|doi=10.1002/jpln.19941570408}}</ref> |
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==Formation== |
==Formation== |
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Root hair cells vary between 15 and 17 micrometers in diameter, and 80 and 1,500 micrometers in length.<ref>Dittmar, cited in Esau, 1965</ref> Root hairs are found only in the zone of maturation, also called the zone of differentiation.<ref>https://www.colby.edu/biology/BI237/roots.pdf {{Bare URL PDF|date=March 2022}}</ref> They are not found in the zone of elongation, possibly because older root hairs are sheared off as the root elongates and moves through the soil.<ref>{{Cite web|title=Roots {{!}} Boundless Biology|url=https://courses.lumenlearning.com/boundless-biology/chapter/roots/|access-date=2021-11-16|website=courses.lumenlearning.com}}</ref> Root hairs grow quickly, at least 1 μm/min, making them particularly useful for research on cell expansion.<ref>{{Cite journal|last1=Grierson|first1=Claire|last2=Schiefelbein|first2=John|title=Root Hairs|journal=The Arabidopsis Book|volume=1|pages=e0060|doi=10.1199/tab.0060|pmid=22303213|pmc=3243358|date=1 January 2002}}</ref> Just prior to and during root hair cell development, there is elevated [[phosphorylase]] activity.<ref>{{Cite journal|last1=Dosier|first1=Larry W.|last2=Riopel|first2=J. L.|year=1977|title=Differential Enzyme Activity During Trichoblast Differentiation in Elodea Canadensis|journal=American Journal of Botany|language=en|volume=64|issue=9|pages=1049–1056|doi=10.1002/j.1537-2197.1977.tb10794.x}}</ref> |
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Root hairs grow quickly, at least 1μm/min, making them particularly useful for research on cell expansion.<ref>{{Cite journal|last1=Grierson|first1=Claire|last2=Schiefelbein|first2=John|title=Root Hairs|journal=The Arabidopsis Book|volume=1|pages=e0060|doi=10.1199/tab.0060|pmid=22303213|pmc=3243358|date=1 January 2002}}</ref> |
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== |
== Fungal interaction == |
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Root hairs are essential for healthy plant nutrition, especially through their interactions with [[Symbiosis|symbiotic]] fungi. Symbiotic fungi and root hairs produce mycorrhizal symbioses like [[arbuscular mycorrhiza]], formed by AM fungi, and [[ectomycorrhiza]], formed by EM fungi.<ref>{{Cite journal|last1=Ezawa|first1=Tatsuhiro|last2=Smith|first2=Sally E.|last3=Smith|first3=F. Andrew|date=2002-07-01|title=P metabolism and transport in AM fungi|url=https://doi.org/10.1023/A:1020258325010|journal=Plant and Soil|language=en|volume=244|issue=1|pages=221–230|doi=10.1023/A:1020258325010|s2cid=25801972|issn=1573-5036|hdl=2115/637|hdl-access=free}}</ref> These are very common,<ref>{{Cite journal|last=Parniske|first=Martin|date=October 2008|title=Arbuscular mycorrhiza: the mother of plant root endosymbioses|url=https://www.nature.com/articles/nrmicro1987|journal=Nature Reviews Microbiology|volume=6|issue=10|pages=763–775|doi=10.1038/nrmicro1987|pmid=18794914|s2cid=5432120}}</ref> occurring in 90% of terrestrial plant species,<ref name=":1">{{Cite journal|last=Frary|first=Amy|title=Plant Physiology and DevelopmentPlant Physiology and Development edited by Lincoln Taiz, Eduardo Zeiger, Ian Max Moller, and Angus Murphy. 2014. . ISBN 978-1-60535-255-8 $123.96 (casebound); $80.58 (looseleaf). Sinauer Associates Inc., Sunderland, MA.|url=http://dx.doi.org/10.3119/0035-4902-117.971.397|journal=Rhodora|year=2015|volume=117|issue=971|pages=397–399|doi=10.3119/0035-4902-117.971.397|s2cid=85738640|issn=0035-4902}}</ref> because of the benefits it brings to both the fungus and plant. |
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Formation of this |
Formation of this relationship for EM fungi begins with the colonization of the root hairs. This process begins when the EM fungus adheres to the root hair from the soil.<ref name=":0">{{Cite journal|last1=Zou|first1=Ying-Ning|last2=Zhang|first2=De-Jian|last3=Liu|first3=Chun-Yan|last4=Wu|first4=Qiang-Sheng|date=2018-10-30|title=Relationships between mycorrhizas and root hairs|url=http://dx.doi.org/10.30848/pjb2019-2(39)|journal=Pakistan Journal of Botany|volume=51|issue=2|doi=10.30848/pjb2019-2(39)|s2cid=91581074 |issn=0556-3321}}</ref> The fungus then secretes diffusible factors, to which root hairs are highly sensitive, allowing the [[hypha]]e to penetrate into the epidermal cells and create a [[Hartig net]] in the first layers of the root cortex.<ref name=":0" /> This highly branched structure serves as an interface between the two organisms as fungal cells adapt to the exchanges that occur between the plant and fungus.<ref>{{Cite journal|last=Nehls|first=U.|date=2008-02-16|title=Mastering ectomycorrhizal symbiosis: the impact of carbohydrates|journal=Journal of Experimental Botany|language=en|volume=59|issue=5|pages=1097–1108|doi=10.1093/jxb/erm334|pmid=18272925|issn=0022-0957|doi-access=free}}</ref> This process is similar to how AM fungi colonize root hairs, but instead of diffusible factors, they secrete hydrolases to relax the cell wall, which allows hyphae to enter, and there is no Hartig net.<ref name=":0" /> |
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Various effects of fungal colonization in root hairs show that this relationship is beneficial to both plant and fungal species, but the main effect is on root hair growth. Fungi actually affect the growth of root hairs if there is water or nutrient deficiency.<ref name=":0" /> Since both of these organisms require nutrients and water, their cooperation is essential to their mutual survival. Upon detection of deficiency, the drought stress response of the plant is triggered, causing growth of the root hairs.<ref name=":1" /> The mycorrhizae of the fungus then uses its extended system to help the plant find the correct area of nutrition, signaling the direction in which the roots should grow.<ref name=":0" /> This makes root growth more efficient, preserving energy for other metabolic processes, which in turn benefits the fungus that feeds off those metabolic products. |
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| ⚫ | |||
| ⚫ | Root hairs form an important surface as they are needed to [[Absorption of water|absorb]] most of the water and nutrients needed for the plant. They are also directly involved in the formation of [[root nodule]]s in [[Fabaceae|legume]] plants. The root hairs curl around the bacteria which allows for the formation of an infection thread |
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Having a large surface area, the [[active uptake]] of water and minerals through root hairs is highly efficient. |
|||
| ⚫ | Root hair cells also secrete |
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==Survival== |
==Survival== |
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When a new root hair cell grows, it excretes a [[hormone]] that inhibits the growth of root hairs in nearby cells. This ensures equal and efficient distribution of the actual hairs on these cells.{{Citation needed|date=October 2018}} |
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Repotting or transplanting a plant can result in root hair cells being pulled off, perhaps to a significant extent, which can cause wilting.<ref>{{Cite web |date=2021-06-03 |title=2.2: The regions of the root |url=https://bio.libretexts.org/Bookshelves/Botany/Botany_in_Hawaii_(Daniela_Dutra_Elliott_and_Paula_Mejia_Velasquez)/02%3A_Roots/2.02%3A_The_regions_of_the_root |access-date=2024-06-27 |website=Biology LibreTexts |language=en}}</ref> |
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==See also== |
==See also== |
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* [[Mycorrhizae]] |
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* [[Trichome]] |
* [[Trichome]] |
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==References== |
==References== |
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{{Reflist}} |
{{Reflist}} |
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==Further reading== |
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{{DEFAULTSORT:Root Hair}} |
{{DEFAULTSORT:Root Hair}} |
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[[Category:Plant anatomy]] |
[[Category:Plant anatomy]] |
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[[Category:Plant roots]] |
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[[Category:Soil biology]] |
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Latest revision as of 14:19, 2 December 2024
Root hairs 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 hair cells improve plant water absorption by increasing root surface area to volume ratio which allows the root hair cell to take in more water. The large vacuole inside root hair cells makes this intake much more efficient. Root hairs are also important for nutrient uptake as they are main interface between plants and mycorrhizal fungi.
Function
[edit]The function of all root hairs is to collect water and mineral nutrients in the soil to be sent throughout the plant. In roots, most water absorption happens through the root hairs. The length of root hairs allows them to penetrate between soil particles and prevents harmful bacterial organisms from entering the plant through the xylem vessels.[1] Increasing the surface area of these hairs makes plants more efficient in absorbing nutrients and interacting with microbes.[2] As root hair cells do not carry out photosynthesis, they do not contain chloroplasts.
Importance
[edit]Root hairs form an important surface as they are needed to absorb most of the water and nutrients needed for the plant. They are also directly involved in the formation of root nodules in legume plants. The root hairs curl around the bacteria, which allows for the formation of an infection thread into the dividing cortical cells to form the nodule.[3]
Having a large surface area, the active uptake of water and minerals through root hairs is highly efficient. Root hair cells also secrete acids (e.g., malic and citric acid), which solubilize minerals by changing their oxidation state, making the ions easier to absorb.[4]
Formation
[edit]Root hair cells vary between 15 and 17 micrometers in diameter, and 80 and 1,500 micrometers in length.[5] Root hairs are found only in the zone of maturation, also called the zone of differentiation.[6] They are not found in the zone of elongation, possibly because older root hairs are sheared off as the root elongates and moves through the soil.[7] Root hairs grow quickly, at least 1 μm/min, making them particularly useful for research on cell expansion.[8] Just prior to and during root hair cell development, there is elevated phosphorylase activity.[9]
Fungal interaction
[edit]Root hairs are essential for healthy plant nutrition, especially through their interactions with symbiotic fungi. Symbiotic fungi and root hairs produce mycorrhizal symbioses like arbuscular mycorrhiza, formed by AM fungi, and ectomycorrhiza, formed by EM fungi.[10] These are very common,[11] occurring in 90% of terrestrial plant species,[12] because of the benefits it brings to both the fungus and plant.
Formation of this relationship for EM fungi begins with the colonization of the root hairs. This process begins when the EM fungus adheres to the root hair from the soil.[13] The fungus then secretes diffusible factors, to which root hairs are highly sensitive, allowing the hyphae to penetrate into the epidermal cells and create a Hartig net in the first layers of the root cortex.[13] This highly branched structure serves as an interface between the two organisms as fungal cells adapt to the exchanges that occur between the plant and fungus.[14] This process is similar to how AM fungi colonize root hairs, but instead of diffusible factors, they secrete hydrolases to relax the cell wall, which allows hyphae to enter, and there is no Hartig net.[13]
Various effects of fungal colonization in root hairs show that this relationship is beneficial to both plant and fungal species, but the main effect is on root hair growth. Fungi actually affect the growth of root hairs if there is water or nutrient deficiency.[13] Since both of these organisms require nutrients and water, their cooperation is essential to their mutual survival. Upon detection of deficiency, the drought stress response of the plant is triggered, causing growth of the root hairs.[12] The mycorrhizae of the fungus then uses its extended system to help the plant find the correct area of nutrition, signaling the direction in which the roots should grow.[13] This makes root growth more efficient, preserving energy for other metabolic processes, which in turn benefits the fungus that feeds off those metabolic products.
Survival
[edit]When a new root hair cell grows, it excretes a hormone that inhibits the growth of root hairs in nearby cells. This ensures equal and efficient distribution of the actual hairs on these cells.[citation needed]
Repotting or transplanting a plant can result in root hair cells being pulled off, perhaps to a significant extent, which can cause wilting.[15]
See also
[edit]References
[edit]- ^ "Water Balance in Plants". The Wonder of Science. Retrieved 2021-11-16.
- ^ Grierson, C.; Schiefelbein, J. (2002). "Root Hairs". The Arabidopsis Book. 1: e0060. doi:10.1199/tab.0060. PMC 3243358. PMID 22303213.
- ^ Mergaert, Peter; Uchiumi, Toshiki; Alunni, Benoît; Evanno, Gwénaëlle; Cheron, Angélique; Catrice, Olivier; Mausset, Anne-Elisabeth; Barloy-Hubler, Frédérique; Galibert, Francis; Kondorosi, Adam; Kondorosi, Eva (28 March 2006). "Eukaryotic control on bacterial cell cycle and differentiation in the Rhizobium–legume symbiosis". Proceedings of the National Academy of Sciences. 103 (13): 5230–5235. Bibcode:2006PNAS..103.5230M. doi:10.1073/pnas.0600912103. PMC 1458823. PMID 16547129.
- ^ Gerke, Jörg; Römer, Wilhelm; Jungk, Albrecht (1994). "The excretion of citric and malic acid by proteoid roots of Lupinus albus L.; effects on soil solution concentrations of phosphate, iron, and aluminum in the proteoid rhizosphere in samples of an oxisol and a luvisol". Zeitschrift für Pflanzenernährung und Bodenkunde. 157 (4): 289–294. doi:10.1002/jpln.19941570408.
- ^ Dittmar, cited in Esau, 1965
- ^ https://www.colby.edu/biology/BI237/roots.pdf [bare URL PDF]
- ^ "Roots | Boundless Biology". courses.lumenlearning.com. Retrieved 2021-11-16.
- ^ Grierson, Claire; Schiefelbein, John (1 January 2002). "Root Hairs". The Arabidopsis Book. 1: e0060. doi:10.1199/tab.0060. PMC 3243358. PMID 22303213.
- ^ Dosier, Larry W.; Riopel, J. L. (1977). "Differential Enzyme Activity During Trichoblast Differentiation in Elodea Canadensis". American Journal of Botany. 64 (9): 1049–1056. doi:10.1002/j.1537-2197.1977.tb10794.x.
- ^ Ezawa, Tatsuhiro; Smith, Sally E.; Smith, F. Andrew (2002-07-01). "P metabolism and transport in AM fungi". Plant and Soil. 244 (1): 221–230. doi:10.1023/A:1020258325010. hdl:2115/637. ISSN 1573-5036. S2CID 25801972.
- ^ Parniske, Martin (October 2008). "Arbuscular mycorrhiza: the mother of plant root endosymbioses". Nature Reviews Microbiology. 6 (10): 763–775. doi:10.1038/nrmicro1987. PMID 18794914. S2CID 5432120.
- ^ a b Frary, Amy (2015). "Plant Physiology and DevelopmentPlant Physiology and Development edited by Lincoln Taiz, Eduardo Zeiger, Ian Max Moller, and Angus Murphy. 2014. . ISBN 978-1-60535-255-8 $123.96 (casebound); $80.58 (looseleaf). Sinauer Associates Inc., Sunderland, MA". Rhodora. 117 (971): 397–399. doi:10.3119/0035-4902-117.971.397. ISSN 0035-4902. S2CID 85738640.
- ^ a b c d e Zou, Ying-Ning; Zhang, De-Jian; Liu, Chun-Yan; Wu, Qiang-Sheng (2018-10-30). "Relationships between mycorrhizas and root hairs". Pakistan Journal of Botany. 51 (2). doi:10.30848/pjb2019-2(39). ISSN 0556-3321. S2CID 91581074.
- ^ Nehls, U. (2008-02-16). "Mastering ectomycorrhizal symbiosis: the impact of carbohydrates". Journal of Experimental Botany. 59 (5): 1097–1108. doi:10.1093/jxb/erm334. ISSN 0022-0957. PMID 18272925.
- ^ "2.2: The regions of the root". Biology LibreTexts. 2021-06-03. Retrieved 2024-06-27.