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Trichome

Trichomes (/ˈtrkmz, ˈtrɪkmz/; from Ancient Greek τρίχωμα (tríkhōma) 'hair') are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant is an indumentum, and the surface bearing them is said to be pubescent.

Flower bud of a Capsicum pubescens plant, with many trichomes
Fossil stellate hair (trichome) probably of an oak, in Baltic amber; image is about 1 mm wide.

Algal trichomes edit

Certain, usually filamentous, algae have the terminal cell produced into an elongate hair-like structure called a trichome.[example needed] The same term is applied to such structures in some cyanobacteria, such as Spirulina and Oscillatoria. The trichomes of cyanobacteria may be unsheathed, as in Oscillatoria, or sheathed, as in Calothrix.[1] These structures play an important role in preventing soil erosion, particularly in cold desert climates.[citation needed] The filamentous sheaths form a persistent sticky network that helps maintain soil structure.

Plant trichomes edit

 
Sticky trichomes of a carnivorous plant, Drosera capensis with a trapped insect, contain proteolytic enzymes
 
Glandular trichomes on Cannabis, rich in cannabinoids
 
Trichomes on the surface of a Solanum scabrum leaf
 
Trichomes on the petiole of a Solanum quitoense leaf
 
Antirrhinum majus buds with glandular hairs
 
Scanning electron micrograph of a trichome on a leaf of Arabidopsis thaliana; the structure is a single cell.
 
Scanning electron micrograph of leaf hairs on Brachypodium distachyon (250x)
 
Red glandular trichomes on a rose stem

Plant trichomes have many different features that vary between both species of plants and organs of an individual plant. These features affect the subcategories that trichomes are placed into. Some defining features include the following:

  • Unicellular or multicellular
  • Straight (upright with little to no branching), spiral (corkscrew-shaped) or hooked (curved apex)[2]
  • Presence of cytoplasm
  • Glandular (secretory) vs. eglandular
  • Tortuous, simple (unbranched and unicellular), peltate (scale-like), stellate (star-shaped)[3]
  • Adaxial vs. abaxial, referring to whether trichomes are present, respectively, on the upper surface (adaxial) or lower surface (abaxial) of a leaf or other lateral organ.

In a model organism, Cistus salviifolius, there are more adaxial trichomes present on this plant because this surface suffers from more ultraviolet (UV), solar irradiance light stress than the abaxial surface.[4]

Trichomes can protect the plant from a large range of detriments, such as UV light, insects, transpiration, and freeze intolerance.[5]

Aerial surface hairs edit

Trichomes on plants are epidermal outgrowths of various kinds. The terms emergences or prickles refer to outgrowths that involve more than the epidermis. This distinction is not always easily applied (see Wait-a-minute tree). Also, there are nontrichomatous epidermal cells that protrude from the surface, such as root hairs.

A common type of trichome is a hair. Plant hairs may be unicellular or multicellular, and branched or unbranched. Multicellular hairs may have one or several layers of cells. Branched hairs can be dendritic (tree-like) as in kangaroo paw (Anigozanthos), tufted, or stellate (star-shaped), as in Arabidopsis thaliana.

Another common type of trichome is the scale or peltate hair, that has a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind. Common examples are the leaf scales of bromeliads such as the pineapple, Rhododendron and sea buckthorn (Hippophae rhamnoides).

Any of the various types of hairs may be glandular, producing some kind of secretion, such as the essential oils produced by mints and many other members of the family Lamiaceae.

Many terms are used to describe the surface appearance of plant organs, such as stems and leaves, referring to the presence, form and appearance of trichomes. Examples include:

  • glabrous, glabrate – lacking hairs or trichomes; surface smooth
  • hirsute – coarsely hairy
  • hispid – having bristly hairs
  • articulate – simple pluricellular-uniseriate hairs
  • downy – having an almost wool-like covering of long hairs
  • pilose – pubescent with long, straight, soft, spreading or erect hairs
  • puberulent – minutely pubescent; having fine, short, usually erect, hairs
  • puberulous – slightly covered with minute soft and erect hairs
  • pubescent – bearing hairs or trichomes of any type
  • strigillose – minutely strigose
  • strigose – having straight hairs all pointing in more or less the same direction as along a margin or midrib
  • tomentellous – minutely tomentose
  • tomentose – covered with dense, matted, woolly hairs
  • villosulous – minutely villous
  • villous – having long, soft hairs, often curved, but not matted

The size, form, density and location of hairs on plants are extremely variable in their presence across species and even within a species on different plant organs. Several basic functions or advantages of having surface hairs can be listed. It is likely that in many cases, hairs interfere with the feeding of at least some small herbivores and, depending upon stiffness and irritability to the palate, large herbivores as well. Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells. In windy locations, hairs break up the flow of air across the plant surface, reducing transpiration. Dense coatings of hairs reflect sunlight, protecting the more delicate tissues underneath in hot, dry, open habitats. In addition, in locations where much of the available moisture comes from fog drip, hairs appear to enhance this process by increasing the surface area on which water droplets can accumulate.[citation needed]

Glandular trichomes edit

Glandular trichomes have been vastly studied, even though they are only found on about 30% of plants. Their function is to secrete metabolites for the plant. Some of these metabolites include:

Non-glandular trichomes edit

Non-glandular trichomes serve as structural protection against a variety of abiotic stressors, including water losses, extreme temperatures and UV radiation, and biotic threats, such as pathogen or herbivore attack.[9]

For example, the model plant C. salviifolius is found in areas of high-light stress and poor soil conditions, along the Mediterranean coasts. It contains non-glandular, stellate and dendritic trichomes that have the ability to synthesize and store polyphenols that both affect absorbance of radiation and plant desiccation. These trichomes also contain acetylated flavonoids, which can absorb UV-B, and non-acetylated flavonoids, which absorb the longer wavelength of UV-A. In non-glandular trichomes, the only known role of flavonoids is to block out the shortest wavelengths to protect the plant; this differs from their role in glandular trichomes.[4]

Polyphenols edit

Non-glandular trichomes in the genus Cistus were found to contain presences of ellagitannins, glycosides, and kaempferol derivatives. The ellagitannins have the main purpose of helping adapt in times of nutrient-limiting stress.[4]

Trichome and root hair development edit

Both trichomes and root hairs, the rhizoids of many vascular plants, are lateral outgrowths of a single cell of the epidermal layer. Root hairs form from trichoblasts, the hair-forming cells on the epidermis of a plant root. Root hairs vary between 5 and 17 micrometers in diameter, and 80 to 1,500 micrometers in length (Dittmar, cited in Esau, 1965). Root hairs can survive for two to three weeks and then die off. At the same time new root hairs are continually being formed at the top of the root. This way, the root hair coverage stays the same. It is therefore understandable that repotting must be done with care, because the root hairs are being pulled off for the most part. This is why planting out may cause plants to wilt.

The genetic control of patterning of trichomes and roots hairs shares similar control mechanisms. Both processes involve a core of related transcription factors that control the initiation and development of the epidermal outgrowth. Activation of genes that encode specific protein transcription factors (named GLABRA1 (GL1), GLABRA3 (GL3) and TRANSPARENT TESTA GLABRA1 (TTG1)) are the major regulators of cell fate to produce trichomes or root hairs.[10] When these genes are activated in a leaf epidermal cell, the formation of a trichrome is initiated within that cell. GL1, GL3. and TTG1 also activate negative regulators, which serve to inhibit trichrome formation in neighboring cells. This system controls the spacing of trichomes on the leaf surface. Once trichome are developed they may divide or branch.[11] In contrast, root hairs only rarely branch. During the formation of trichomes and root hairs, many enzymes are regulated. For example, just prior to the root hair development, there is a point of elevated phosphorylase activity.[12]

Many of what scientists know about trichome development comes from the model organism Arabidopsis thaliana, because their trichomes are simple, unicellular, and non-glandular. The development pathway is regulated by three transcription factors: R2R3 MYB, basic helix-loop-helix, and WD40 repeat. The three groups of TFs form a trimer complex (MBW) and activate the expression of products downstream, which activates trichome formation. However, just MYBs alone act as an inhibitor by forming a negative complex.[13]

Phytohormones edit

Plant phytohormones have an effect on the growth and response of plants to environmental stimuli. Some of these phytohormones are involved in trichome formation, which include gibberellic acid (GA), cytokinins (CK), and jasmonic acids (JA). GA stimulates growth of trichomes by stimulating GLABROUS1 (GL1), however, both SPINDLY and DELLA proteins repress the effects of GA, so less of these proteins create more trichomes.[13]

Some other phytohormones that promote growth of trichomes include brassinosteroids, ethylene, and salicylic acid. This was understood by conducting experiments with mutants that has little to no amounts of each of these substances. In every case, there was less trichome formation on both plant surfaces, as well as incorrect formation of the trichomes present.[13]

Significance for taxonomy edit

The type, presence and absence and location of trichomes are important diagnostic characters in plant identification and plant taxonomy.[14] In forensic examination, plants such as Cannabis sativa can be identified by microscopic examination of the trichomes.[15][16] Although trichomes are rarely found preserved in fossils, trichome bases are regularly found and, in some cases, their cellular structure is important for identification.

Arabidopsis thaliana trichome classification edit

Arabidopsis thaliana trichomes are classified as being aerial, epidermal, unicellular, tubular structures.[17]

Significance for plant molecular biology edit

In the model plant Arabidopsis thaliana, trichome formation is initiated by the GLABROUS1 protein. Knockouts of the corresponding gene lead to glabrous plants. This phenotype has already been used in genome editing experiments and might be of interest as visual marker for plant research to improve gene editing methods such as CRISPR/Cas9.[18][19] Trichomes also serve as models for cell differentiation as well as pattern formation in plants.[20]

Uses edit

Bean leaves have been used historically to trap bedbugs in houses in Eastern Europe. The trichomes on the bean leaves capture the insects by impaling their feet (tarsi). The leaves would then be destroyed.[21]

Trichomes are an essential part of nest building for the European wool carder bee (Anthidium manicatum). This bee species incorporates trichomes into their nests by scraping them off of plants and using them as a lining for their nest cavities.[22]

Defense edit

Plants may use trichomes in order to deter herbivore attacks via physical and/or chemical means, e.g. in specialized, stinging hairs of Urtica (Nettle) species that deliver inflammatory chemicals such as histamine. Studies on trichomes have been focused towards crop protection, which is the result of deterring herbivores (Brookes et al. 2016).[23] However, some organisms have developed mechanisms to resist the effects of trichomes. The larvae of Heliconius charithonia, for example, are able to physically free themselves from trichomes, are able to bite off trichomes, and are able to form silk blankets in order to navigate the leaves better.[24]

Stinging trichomes edit

Stinging trichomes vary in their morphology and distribution between species, however similar effects on large herbivores implies they serve similar functions. In areas susceptible to herbivory, higher densities of stinging trichomes were observed. In Urtica, the stinging trichomes induce a painful sensation lasting for hours upon human contact. This sensation has been attributed as a defense mechanism against large animals and small invertebrates, and plays a role in defense supplementation via secretion of metabolites. Studies suggest that this sensation involves a rapid release of toxin (such as histamine) upon contact and penetration via the globular tips of said trichomes.[25]

See also edit

References edit

  1. ^ "Identify That Alga". Retrieved September 20, 2013.
  2. ^ Payne, Willard W. (1978). "A Glossary of Plant Hair Terminology". Brittonia. 30 (2): 239–255. doi:10.2307/2806659. ISSN 0007-196X. JSTOR 2806659. S2CID 42417527.
  3. ^ Levin, Donald A. (1973). "The Role of Trichomes in Plant Defense". The Quarterly Review of Biology. 48 (1): 3–15. doi:10.1086/407484. ISSN 0033-5770. JSTOR 2822621. S2CID 83358711.
  4. ^ a b c Tattini, M.; Matteini, P.; Saracini, E.; Traversi, M. L.; Giordano, C.; Agati, G. (2007). "Morphology and Biochemistry of Non-Glandular Trichomes in Cistus salvifolius L. Leaves Growing in Extreme Habitats of the Mediterranean Basin". Plant Biology. 9 (3): 411–419. doi:10.1055/s-2006-924662. ISSN 1438-8677. PMID 17143807.
  5. ^ Hülskamp, Martin (June 2004). "Plant Trichomes: A Model for Cell Differentiation". Molecular Cell Biology. 5 (6): 471–480. doi:10.1038/nrm1404. PMID 15173826. S2CID 26541461 – via EBSCO.
  6. ^ Tholl, Dorothea (2015), "Biosynthesis and Biological Functions of Terpenoids in Plants", in Schrader, Jens; Bohlmann, Jörg (eds.), Biotechnology of Isoprenoids, Advances in Biochemical Engineering/Biotechnology, vol. 148, Springer International Publishing, pp. 63–106, doi:10.1007/10_2014_295, ISBN 9783319201078, PMID 25583224
  7. ^ Jasiński, Michał; Biała, Wanda (2018). "The Phenylpropanoid Case – It Is Transport That Matters". Frontiers in Plant Science. 9: 1610. doi:10.3389/fpls.2018.01610. ISSN 1664-462X. PMC 6221964. PMID 30443262.
  8. ^ Huchelmann, Alexandre; Boutry, Marc; Hachez, Charles (2017). "Plant Glandular Trichomes: Natural Cell Factories of High Biotechnological Interest1[OPEN]". Plant Physiology. 175 (1): 6–22. doi:10.1104/pp.17.00727. ISSN 0032-0889. PMC 5580781. PMID 28724619.
  9. ^ Karabourniotis, George; Liakopoulos, Georgios; Nikolopoulos, Dimosthenis; Bresta, Panagiota (2020-02-01). "Protective and defensive roles of non-glandular trichomes against multiple stresses: structure–function coordination". Journal of Forestry Research. 31 (1): 1–12. doi:10.1007/s11676-019-01034-4. ISSN 1993-0607.
  10. ^ Schellmann, S.; Schnittger, A.; Kirik, V.; Wada, T.; Okada, K.; Beermann, A.; Thumfahrt, J.; Jürgens, G.; Hülskamp, M. (2002-10-01). "TRIPTYCHON and CAPRICE mediate lateral inhibition during trichome and root hair patterning in Arabidopsis". The EMBO Journal. 21 (19): 5036–5046. doi:10.1093/emboj/cdf524. ISSN 0261-4189. PMC 129046. PMID 12356720.
  11. ^ Schellmann, Swen; Hulskamp, Martin (2004-09-01). "Epidermal differentiation: trichomes in Arabidopsis as a model system". The International Journal of Developmental Biology. 49 (5–6): 579–584. doi:10.1387/ijdb.051983ss. ISSN 0214-6282. PMID 16096966.
  12. ^ 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:10.2307/2442160. JSTOR 2442160.
  13. ^ a b c Yuan, Ling; Singh, Sanjay Kumar; Patra, Barunava; Pattanaik, Sitakanta (2014). "An overview of the gene regulatory network controlling trichome development in the model plant, Arabidopsis". Frontiers in Plant Science. 5: 259. doi:10.3389/fpls.2014.00259. ISSN 1664-462X. PMC 4071814. PMID 25018756.
  14. ^ Davis, P.H.; Heywood, V.H. (1963). Principles of angiosperm taxonomy. Princeton, New Jersey: Van Nostrandpage. p. 154.
  15. ^ Bhatia, R.Y.P.; Raghavan, S.; Rao, K.V.S.; Prasad, V.N. (1973). "Forensic examination of leaf and leaf fragments in fresh and dried conditions". Journal of the Forensic Science Society. 13 (3): 183–190. doi:10.1016/S0015-7368(73)70794-5. PMID 4774149.
  16. ^ United Nations Office on Drugs and Crime (2009). Recommended Methods for the Identification and Analysis of Cannabis and Cannabis Products (Revised and updated). New York: United Nations. pp. 30–32. ISBN 9789211482423.
  17. ^ Maithur, Jaideep; Chua, Nam-Hai (April 2000). "Microtubule Stabilization Leads to Growth Reorientation in Arabidopsis Trichomes" (PDF). Plant Cell. 12 (4): 465–477. doi:10.1105/tpc.12.4.465. PMC 139846. PMID 10760237.
  18. ^ Hahn, Florian; Mantegazza, Otho; Greiner, André; Hegemann, Peter; Eisenhut, Marion; Weber, Andreas P. M. (2017). "An Efficient Visual Screen for CRISPR/Cas9 Activity in Arabidopsis thaliana". Frontiers in Plant Science. 8: 39. doi:10.3389/fpls.2017.00039. ISSN 1664-462X. PMC 5258748. PMID 28174584.
  19. ^ Hahn, Florian; Eisenhut, Marion; Mantegazza, Otho; Weber, Andreas P. M. (5 April 2018). "Homology-Directed Repair of a Defective Glabrous Gene in Arabidopsis With Cas9-Based Gene Targeting". Frontiers in Plant Science. 9: 424. doi:10.3389/fpls.2018.00424. PMC 5895730. PMID 29675030.
  20. ^ Hülskamp, M.; Schnittger, A.; Folkers, U. (1999). "Pattern formation and cell differentiation: trichomes in Arabidopsis as a genetic model system". International Review of Cytology. 186: 147–178. doi:10.1016/S0074-7696(08)61053-0. ISBN 9780123645906. ISSN 0074-7696. PMID 9770299.
  21. ^ Szyndler, M.W.; Haynes, K.F.; Potter, M.F.; Corn, R.M.; Loudon, C. (2013). "Entrapment of bed bugs by leaf trichomes inspires microfabrication of biomimetic surfaces". Journal of the Royal Society Interface. 10 (83): 20130174. doi:10.1098/rsif.2013.0174. ISSN 1742-5662. PMC 3645427. PMID 23576783.
  22. ^ Eltz, Thomas; Küttner, Jennifer; Lunau, Klaus; Tollrian, Ralph (6 January 2015). "Plant secretions prevent wasp parasitism in nests of wool-carder bees, with implications for the diversification of nesting materials in Megachilidae". Frontiers in Ecology and Evolution. 2. doi:10.3389/fevo.2014.00086.
  23. ^ Karley, A (2016). "Exploiting physical defence traits for crop protection: leaf trichomes of Rubus idaeus have deterrent effects on spider mites but not aphids". Annals of Applied Biology. 168 (2): 159–172. doi:10.1111/aab.12252 – via Academic Search Premier.
  24. ^ Cardoso, Márcio Z (2008). "Ecology, Behavior and Binomics: Herbivore Handling of a Plant's Trichome: The Case of Heliconius Charithonia (L.) (Lepidoptera:Nymphalidae) and Passiflora Lobata (Kilip) Hutch. (Passifloraceae)". Neotropical Entomology. 37 (3): 247–52. doi:10.1590/s1519-566x2008000300002. PMID 18641894.
  25. ^ Fu, H. Y.; Chen, S. J.; Kuo-Huang, L. L. (2003). "Comparative study on the stinging trichomes and some related epidermal structures in the leaves of Dendrocnide meyeniana, Girardinia diversifolia, and Urtica thunbergiana". Taiwania. 48 (4): 213–223.

Bibliography edit

  • Esau, K. 1965. Plant Anatomy, 2nd Edition. John Wiley & Sons. 767 pp.

trichome, confused, with, trichrome, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, schola. Not to be confused with Trichrome This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Trichome news newspapers books scholar JSTOR October 2022 Learn how and when to remove this template message Trichomes ˈ t r aɪ k oʊ m z ˈ t r ɪ k oʊ m z from Ancient Greek trixwma trikhōma hair are fine outgrowths or appendages on plants algae lichens and certain protists They are of diverse structure and function Examples are hairs glandular hairs scales and papillae A covering of any kind of hair on a plant is an indumentum and the surface bearing them is said to be pubescent Flower bud of a Capsicum pubescens plant with many trichomesFossil stellate hair trichome probably of an oak in Baltic amber image is about 1 mm wide Contents 1 Algal trichomes 2 Plant trichomes 2 1 Aerial surface hairs 2 2 Glandular trichomes 2 3 Non glandular trichomes 2 3 1 Polyphenols 3 Trichome and root hair development 3 1 Phytohormones 4 Significance for taxonomy 4 1 Arabidopsis thaliana trichome classification 5 Significance for plant molecular biology 6 Uses 7 Defense 7 1 Stinging trichomes 8 See also 9 References 10 BibliographyAlgal trichomes editCertain usually filamentous algae have the terminal cell produced into an elongate hair like structure called a trichome example needed The same term is applied to such structures in some cyanobacteria such as Spirulina and Oscillatoria The trichomes of cyanobacteria may be unsheathed as in Oscillatoria or sheathed as in Calothrix 1 These structures play an important role in preventing soil erosion particularly in cold desert climates citation needed The filamentous sheaths form a persistent sticky network that helps maintain soil structure Plant trichomes edit nbsp Sticky trichomes of a carnivorous plant Drosera capensis with a trapped insect contain proteolytic enzymes nbsp Glandular trichomes on Cannabis rich in cannabinoids nbsp Trichomes on the surface of a Solanum scabrum leaf nbsp Trichomes on the petiole of a Solanum quitoense leaf nbsp Antirrhinum majus buds with glandular hairs nbsp Scanning electron micrograph of a trichome on a leaf of Arabidopsis thaliana the structure is a single cell nbsp Scanning electron micrograph of leaf hairs on Brachypodium distachyon 250x nbsp Red glandular trichomes on a rose stemPlant trichomes have many different features that vary between both species of plants and organs of an individual plant These features affect the subcategories that trichomes are placed into Some defining features include the following Unicellular or multicellular Straight upright with little to no branching spiral corkscrew shaped or hooked curved apex 2 Presence of cytoplasm Glandular secretory vs eglandular Tortuous simple unbranched and unicellular peltate scale like stellate star shaped 3 Adaxial vs abaxial referring to whether trichomes are present respectively on the upper surface adaxial or lower surface abaxial of a leaf or other lateral organ In a model organism Cistus salviifolius there are more adaxial trichomes present on this plant because this surface suffers from more ultraviolet UV solar irradiance light stress than the abaxial surface 4 Trichomes can protect the plant from a large range of detriments such as UV light insects transpiration and freeze intolerance 5 Aerial surface hairs edit This section does not cite any sources Please help improve this section by adding citations to reliable sources Unsourced material may be challenged and removed October 2022 Learn how and when to remove this template message Trichomes on plants are epidermal outgrowths of various kinds The terms emergences or prickles refer to outgrowths that involve more than the epidermis This distinction is not always easily applied see Wait a minute tree Also there are nontrichomatous epidermal cells that protrude from the surface such as root hairs A common type of trichome is a hair Plant hairs may be unicellular or multicellular and branched or unbranched Multicellular hairs may have one or several layers of cells Branched hairs can be dendritic tree like as in kangaroo paw Anigozanthos tufted or stellate star shaped as in Arabidopsis thaliana Another common type of trichome is the scale or peltate hair that has a plate or shield shaped cluster of cells attached directly to the surface or borne on a stalk of some kind Common examples are the leaf scales of bromeliads such as the pineapple Rhododendron and sea buckthorn Hippophae rhamnoides Any of the various types of hairs may be glandular producing some kind of secretion such as the essential oils produced by mints and many other members of the family Lamiaceae Many terms are used to describe the surface appearance of plant organs such as stems and leaves referring to the presence form and appearance of trichomes Examples include glabrous glabrate lacking hairs or trichomes surface smooth hirsute coarsely hairy hispid having bristly hairs articulate simple pluricellular uniseriate hairs downy having an almost wool like covering of long hairs pilose pubescent with long straight soft spreading or erect hairs puberulent minutely pubescent having fine short usually erect hairs puberulous slightly covered with minute soft and erect hairs pubescent bearing hairs or trichomes of any type strigillose minutely strigose strigose having straight hairs all pointing in more or less the same direction as along a margin or midrib tomentellous minutely tomentose tomentose covered with dense matted woolly hairs villosulous minutely villous villous having long soft hairs often curved but not mattedThe size form density and location of hairs on plants are extremely variable in their presence across species and even within a species on different plant organs Several basic functions or advantages of having surface hairs can be listed It is likely that in many cases hairs interfere with the feeding of at least some small herbivores and depending upon stiffness and irritability to the palate large herbivores as well Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells In windy locations hairs break up the flow of air across the plant surface reducing transpiration Dense coatings of hairs reflect sunlight protecting the more delicate tissues underneath in hot dry open habitats In addition in locations where much of the available moisture comes from fog drip hairs appear to enhance this process by increasing the surface area on which water droplets can accumulate citation needed Glandular trichomes edit Glandular trichomes have been vastly studied even though they are only found on about 30 of plants Their function is to secrete metabolites for the plant Some of these metabolites include terpenoids which have many functions related to defense growth and development 6 phenylpropanoids which have a role in many plant pathways such as secondary metabolites stress response and act as the mediators of plant interactions in the environment 7 flavonoids methyl ketones acylsugars 8 Non glandular trichomes edit Non glandular trichomes serve as structural protection against a variety of abiotic stressors including water losses extreme temperatures and UV radiation and biotic threats such as pathogen or herbivore attack 9 For example the model plant C salviifolius is found in areas of high light stress and poor soil conditions along the Mediterranean coasts It contains non glandular stellate and dendritic trichomes that have the ability to synthesize and store polyphenols that both affect absorbance of radiation and plant desiccation These trichomes also contain acetylated flavonoids which can absorb UV B and non acetylated flavonoids which absorb the longer wavelength of UV A In non glandular trichomes the only known role of flavonoids is to block out the shortest wavelengths to protect the plant this differs from their role in glandular trichomes 4 Polyphenols edit Non glandular trichomes in the genus Cistus were found to contain presences of ellagitannins glycosides and kaempferol derivatives The ellagitannins have the main purpose of helping adapt in times of nutrient limiting stress 4 Trichome and root hair development editBoth trichomes and root hairs the rhizoids of many vascular plants are lateral outgrowths of a single cell of the epidermal layer Root hairs form from trichoblasts the hair forming cells on the epidermis of a plant root Root hairs vary between 5 and 17 micrometers in diameter and 80 to 1 500 micrometers in length Dittmar cited in Esau 1965 Root hairs can survive for two to three weeks and then die off At the same time new root hairs are continually being formed at the top of the root This way the root hair coverage stays the same It is therefore understandable that repotting must be done with care because the root hairs are being pulled off for the most part This is why planting out may cause plants to wilt The genetic control of patterning of trichomes and roots hairs shares similar control mechanisms Both processes involve a core of related transcription factors that control the initiation and development of the epidermal outgrowth Activation of genes that encode specific protein transcription factors named GLABRA1 GL1 GLABRA3 GL3 and TRANSPARENT TESTA GLABRA1 TTG1 are the major regulators of cell fate to produce trichomes or root hairs 10 When these genes are activated in a leaf epidermal cell the formation of a trichrome is initiated within that cell GL1 GL3 and TTG1 also activate negative regulators which serve to inhibit trichrome formation in neighboring cells This system controls the spacing of trichomes on the leaf surface Once trichome are developed they may divide or branch 11 In contrast root hairs only rarely branch During the formation of trichomes and root hairs many enzymes are regulated For example just prior to the root hair development there is a point of elevated phosphorylase activity 12 Many of what scientists know about trichome development comes from the model organism Arabidopsis thaliana because their trichomes are simple unicellular and non glandular The development pathway is regulated by three transcription factors R2R3 MYB basic helix loop helix and WD40 repeat The three groups of TFs form a trimer complex MBW and activate the expression of products downstream which activates trichome formation However just MYBs alone act as an inhibitor by forming a negative complex 13 Phytohormones edit Plant phytohormones have an effect on the growth and response of plants to environmental stimuli Some of these phytohormones are involved in trichome formation which include gibberellic acid GA cytokinins CK and jasmonic acids JA GA stimulates growth of trichomes by stimulating GLABROUS1 GL1 however both SPINDLY and DELLA proteins repress the effects of GA so less of these proteins create more trichomes 13 Some other phytohormones that promote growth of trichomes include brassinosteroids ethylene and salicylic acid This was understood by conducting experiments with mutants that has little to no amounts of each of these substances In every case there was less trichome formation on both plant surfaces as well as incorrect formation of the trichomes present 13 Significance for taxonomy editThe type presence and absence and location of trichomes are important diagnostic characters in plant identification and plant taxonomy 14 In forensic examination plants such as Cannabis sativa can be identified by microscopic examination of the trichomes 15 16 Although trichomes are rarely found preserved in fossils trichome bases are regularly found and in some cases their cellular structure is important for identification Arabidopsis thaliana trichome classification edit Arabidopsis thaliana trichomes are classified as being aerial epidermal unicellular tubular structures 17 Significance for plant molecular biology editIn the model plant Arabidopsis thaliana trichome formation is initiated by the GLABROUS1 protein Knockouts of the corresponding gene lead to glabrous plants This phenotype has already been used in genome editing experiments and might be of interest as visual marker for plant research to improve gene editing methods such as CRISPR Cas9 18 19 Trichomes also serve as models for cell differentiation as well as pattern formation in plants 20 Uses editBean leaves have been used historically to trap bedbugs in houses in Eastern Europe The trichomes on the bean leaves capture the insects by impaling their feet tarsi The leaves would then be destroyed 21 Trichomes are an essential part of nest building for the European wool carder bee Anthidium manicatum This bee species incorporates trichomes into their nests by scraping them off of plants and using them as a lining for their nest cavities 22 Defense editPlants may use trichomes in order to deter herbivore attacks via physical and or chemical means e g in specialized stinging hairs of Urtica Nettle species that deliver inflammatory chemicals such as histamine Studies on trichomes have been focused towards crop protection which is the result of deterring herbivores Brookes et al 2016 23 However some organisms have developed mechanisms to resist the effects of trichomes The larvae of Heliconius charithonia for example are able to physically free themselves from trichomes are able to bite off trichomes and are able to form silk blankets in order to navigate the leaves better 24 Stinging trichomes edit Stinging trichomes vary in their morphology and distribution between species however similar effects on large herbivores implies they serve similar functions In areas susceptible to herbivory higher densities of stinging trichomes were observed In Urtica the stinging trichomes induce a painful sensation lasting for hours upon human contact This sensation has been attributed as a defense mechanism against large animals and small invertebrates and plays a role in defense supplementation via secretion of metabolites Studies suggest that this sensation involves a rapid release of toxin such as histamine upon contact and penetration via the globular tips of said trichomes 25 See also edit nbsp Wikimedia Commons has media related to Trichome Thorns spines and prickles Colleter botany Seta Urticating hairReferences edit Identify That Alga Retrieved September 20 2013 Payne Willard W 1978 A Glossary of Plant Hair Terminology Brittonia 30 2 239 255 doi 10 2307 2806659 ISSN 0007 196X JSTOR 2806659 S2CID 42417527 Levin Donald A 1973 The Role of Trichomes in Plant Defense The Quarterly Review of Biology 48 1 3 15 doi 10 1086 407484 ISSN 0033 5770 JSTOR 2822621 S2CID 83358711 a b c Tattini M Matteini P Saracini E Traversi M L Giordano C Agati G 2007 Morphology and Biochemistry of Non Glandular Trichomes in Cistus salvifolius L Leaves Growing in Extreme Habitats of the Mediterranean Basin Plant Biology 9 3 411 419 doi 10 1055 s 2006 924662 ISSN 1438 8677 PMID 17143807 Hulskamp Martin June 2004 Plant Trichomes A Model for Cell Differentiation Molecular Cell Biology 5 6 471 480 doi 10 1038 nrm1404 PMID 15173826 S2CID 26541461 via EBSCO Tholl Dorothea 2015 Biosynthesis and Biological Functions of Terpenoids in Plants in Schrader Jens Bohlmann Jorg eds Biotechnology of Isoprenoids Advances in Biochemical Engineering Biotechnology vol 148 Springer International Publishing pp 63 106 doi 10 1007 10 2014 295 ISBN 9783319201078 PMID 25583224 Jasinski Michal Biala Wanda 2018 The Phenylpropanoid Case It Is Transport That Matters Frontiers in Plant Science 9 1610 doi 10 3389 fpls 2018 01610 ISSN 1664 462X PMC 6221964 PMID 30443262 Huchelmann Alexandre Boutry Marc Hachez Charles 2017 Plant Glandular Trichomes Natural Cell Factories of High Biotechnological Interest1 OPEN Plant Physiology 175 1 6 22 doi 10 1104 pp 17 00727 ISSN 0032 0889 PMC 5580781 PMID 28724619 Karabourniotis George Liakopoulos Georgios Nikolopoulos Dimosthenis Bresta Panagiota 2020 02 01 Protective and defensive roles of non glandular trichomes against multiple stresses structure function coordination Journal of Forestry Research 31 1 1 12 doi 10 1007 s11676 019 01034 4 ISSN 1993 0607 Schellmann S Schnittger A Kirik V Wada T Okada K Beermann A Thumfahrt J Jurgens G Hulskamp M 2002 10 01 TRIPTYCHON and CAPRICE mediate lateral inhibition during trichome and root hair patterning in Arabidopsis The EMBO Journal 21 19 5036 5046 doi 10 1093 emboj cdf524 ISSN 0261 4189 PMC 129046 PMID 12356720 Schellmann Swen Hulskamp Martin 2004 09 01 Epidermal differentiation trichomes in Arabidopsis as a model system The International Journal of Developmental Biology 49 5 6 579 584 doi 10 1387 ijdb 051983ss ISSN 0214 6282 PMID 16096966 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 2307 2442160 JSTOR 2442160 a b c Yuan Ling Singh Sanjay Kumar Patra Barunava Pattanaik Sitakanta 2014 An overview of the gene regulatory network controlling trichome development in the model plant Arabidopsis Frontiers in Plant Science 5 259 doi 10 3389 fpls 2014 00259 ISSN 1664 462X PMC 4071814 PMID 25018756 Davis P H Heywood V H 1963 Principles of angiosperm taxonomy Princeton New Jersey Van Nostrandpage p 154 Bhatia R Y P Raghavan S Rao K V S Prasad V N 1973 Forensic examination of leaf and leaf fragments in fresh and dried conditions Journal of the Forensic Science Society 13 3 183 190 doi 10 1016 S0015 7368 73 70794 5 PMID 4774149 United Nations Office on Drugs and Crime 2009 Recommended Methods for the Identification and Analysis of Cannabis and Cannabis Products Revised and updated New York United Nations pp 30 32 ISBN 9789211482423 Maithur Jaideep Chua Nam Hai April 2000 Microtubule Stabilization Leads to Growth Reorientation in Arabidopsis Trichomes PDF Plant Cell 12 4 465 477 doi 10 1105 tpc 12 4 465 PMC 139846 PMID 10760237 Hahn Florian Mantegazza Otho Greiner Andre Hegemann Peter Eisenhut Marion Weber Andreas P M 2017 An Efficient Visual Screen for CRISPR Cas9 Activity in Arabidopsis thaliana Frontiers in Plant Science 8 39 doi 10 3389 fpls 2017 00039 ISSN 1664 462X PMC 5258748 PMID 28174584 Hahn Florian Eisenhut Marion Mantegazza Otho Weber Andreas P M 5 April 2018 Homology Directed Repair of a Defective Glabrous Gene in Arabidopsis With Cas9 Based Gene Targeting Frontiers in Plant Science 9 424 doi 10 3389 fpls 2018 00424 PMC 5895730 PMID 29675030 Hulskamp M Schnittger A Folkers U 1999 Pattern formation and cell differentiation trichomes in Arabidopsis as a genetic model system International Review of Cytology 186 147 178 doi 10 1016 S0074 7696 08 61053 0 ISBN 9780123645906 ISSN 0074 7696 PMID 9770299 Szyndler M W Haynes K F Potter M F Corn R M Loudon C 2013 Entrapment of bed bugs by leaf trichomes inspires microfabrication of biomimetic surfaces Journal of the Royal Society Interface 10 83 20130174 doi 10 1098 rsif 2013 0174 ISSN 1742 5662 PMC 3645427 PMID 23576783 Eltz Thomas Kuttner Jennifer Lunau Klaus Tollrian Ralph 6 January 2015 Plant secretions prevent wasp parasitism in nests of wool carder bees with implications for the diversification of nesting materials in Megachilidae Frontiers in Ecology and Evolution 2 doi 10 3389 fevo 2014 00086 Karley A 2016 Exploiting physical defence traits for crop protection leaf trichomes of Rubus idaeus have deterrent effects on spider mites but not aphids Annals of Applied Biology 168 2 159 172 doi 10 1111 aab 12252 via Academic Search Premier Cardoso Marcio Z 2008 Ecology Behavior and Binomics Herbivore Handling of a Plant s Trichome The Case of Heliconius Charithonia L Lepidoptera Nymphalidae and Passiflora Lobata Kilip Hutch Passifloraceae Neotropical Entomology 37 3 247 52 doi 10 1590 s1519 566x2008000300002 PMID 18641894 Fu H Y Chen S J Kuo Huang L L 2003 Comparative study on the stinging trichomes and some related epidermal structures in the leaves of Dendrocnide meyeniana Girardinia diversifolia and Urtica thunbergiana Taiwania 48 4 213 223 Bibliography editEsau K 1965 Plant Anatomy 2nd Edition John Wiley amp Sons 767 pp Retrieved from https en wikipedia org w index php title Trichome amp oldid 1193274663, wikipedia, wiki, book, books, library,

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