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Encyclopedia > Trichome

Trichomes, from the Greek meaning "growth of hair", are fine outgrowths or appendages on plants and protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. Young Girl Fixing her Hair, by Sophie Gengembre Anderson Hair is a filamentous outgrowth of dead cells from the skin, found mainly in mammals. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) †Rhyniophyta - rhyniophytes †Zosterophyllophyta - zosterophylls Lycopodiophyta - clubmosses †Trimerophytophyta - trimerophytes Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta... Typical phyla Rhodophyta (red algae) Chromista Heterokontophyta (heterokonts) Haptophyta Cryptophyta (cryptomonads) Alveolates Dinoflagellata Apicomplexa Ciliophora (ciliates) Excavates Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Amoebozoa Choanozoa Many others; classification varies Protists (IPA: ) are a heterogeneous group of organisms, comprising those eukaryotes that are not animals, plants, or fungi. ...


Algal trichomes

Certain—usually filamentous—algae, have the terminal cell produced into an elongate "hair-like" structure called a trichome. A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... Cells in culture, stained for keratin (red) and DNA (green). ...

Plant trichomes

Aerial surface hairs

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-bit climber). Also, there are nontrichomatous epidermal cells that protrude from the surface. Raised thorns on the stem of the wait-a-bit climber Thorns on rose stems A spine is a rigid, pointed surface protuberance or needle-like structure on an animal, shell, or plant, presumably serving as a defense against attack by predators. ...

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

A common type of trichome is the scale or peltate hair: a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind.

Any of the various types of hairs may be glandular. The cannabis plant produces most of its oils in trichomes, which are separated from the surface of the plant matter to make hashish. It has been suggested that Cannabis indica, Cannabis ruderalis and Cannabis rasta be merged into this article or section. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

In describing the surface appearance of plant organs, such as stems and leaves, many terms are used in reference to the presence, form, and appearance of trichomes. The most basic terms used are glabrous—lacking hairs— and pubescent—having hairs. Details are provided by: A stem is the above ground axis of a vascular plant. ... The leaves of a Beech tree A leaf with laminar structure and pinnate venation In botany, a leaf is an above-ground plant organ specialized for photosynthesis. ...

  • glabrous, glabrate – lacking hairs or trichomes; surface smooth.
  • hirsute – coarsely hairy
  • hispid – having bristly 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 curly, 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.
  • villosulous – minutely villous
  • villous – having long, soft hairs, often curved, but not matted

Hairs on plants are extremely variable in their presence across species, location on plant organs, density (even within a species), and therefore functionality. However, 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 evaporation. Dense coatings of hairs reflect solar radiation, protecting the more delicate tissues underneath in hot, dry, open habitats. And in locations where much of the available moisture comes from cloud drip, hairs appear to enhance this process.

Root hairs

Root hairs, the rhizoids of many vascular plants, are tubular outgrowths of trichoblasts, the hair-forming cells on the epidermis of a plant root. That is, root hairs are lateral extensions of a single cell and only rarely branched. Just prior to the root hair development, there is a point of elevated phosphorylase activity. Rhizoids, in fungi, are small branching hyphae that grow downwards from the stolons that anchor the fungus. ... Divisions Non-seed-bearing plants Equisetophyta Lycopodiophyta Psilotophyta Pteridophyta Superdivision Spermatophyta Pinophyta Cycadophyta Ginkgophyta Gnetophyta Magnoliophyta The vascular plants are plants in the Kingdom Plantae (also called Viridiplantae) that have specialized tissues for conducting water. ... ROOT is an object-oriented software package developed by CERN. It was originally designed for particle physics data analysis and contains several features specific to this field, but it is also commonly used in other applications such as astronomy and data mining. ... Phosphorylase is an enzyme that catalyzes the production of glucose phosphate from glycogen and inorganic phosphate. ...

Root hairs vary between 5 and 17 micrometres in diameter, and 80 to 1,500 micrometres in length (Dittmar, cited in Esau, 1965).

Root hairs can survive for 2 to 3 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.

The ability of the root epidermis to absorb water from the surrounding soil is the same with or without root hairs, but the root hairs enlarge and extend the water absorbing surface.

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, leaves the plant withered for some time.

There are also plants lacking root hairs, mostly water plants or marsh plants, such as duckweeds (family Lemnaceae), and gymnosperms. Close up of two different duckweeds: Spirodela polyrrhiza and Wolffia globosa. ... Coast Douglas-fir cone This article lacks an appropriate Taxobox You can help Wikipedia by adding one. ...

Trichomes and cannabis

Trichomes evolved on cannabis to prevent herbivory/parasitism by small insects[citation needed]. In the wild, insects landing on a cannabis leaf become adhered to the trichomes causing death or lost time (see sundew) and in addition will absorb the cannabinoids and, so intoxicated, experience increased rates of predation and loss of will to escape[citation needed]. However, the intercession of man in the natural selection process has rapidly accelerated the favoring of genotypes that produce copious amounts of THC-laden trichomes. In addition, THC has very high UV-B absorption properties, thus cannabis evolution may have favored the evolution of genotypes that produced these THC laden capitate-stalked trichomes as a built in 'sun-screen' for protection against UV-B light rays. The dried trichomes of cannabis used for smoking purposes is called kief. Species See separate list. ... Tetrahydrocannabinol, also known as THC, Δ9-THC, Δ9-tetrahydrocannabinol (delta-9-tetrahydrocannabinol), Δ¹-tetrahydrocannabinol (using an older numbering scheme), or dronabinol, is the main psychoactive substance found in the Cannabis plant. ... Look up Cannabis in Wiktionary, the free dictionary. ... Kief or kif is the dried resin glands (or trichomes) of cannabis, which accumulates on containers or has been removed with a kiefing screen or sieve. ...


 The Capitate-Stalked trichomes of the cannabis plant.
The Capitate-Stalked trichomes of the cannabis plant.
  • Bulbous: The bulbous type is the smallest (15 to 30 micrometre). From one to four cells make up the "foot" and "stalk," and one to four cells make up the "head" of the gland. Head cells secrete a resin - presumably cannabinoids, and related compounds which accumulate between the head cells and the cuticle. When the gland matures, a nipple-like protrusion may form on the membrane from the pressure of the accumulating resin. The bulbous glands are found scattered about the surfaces of the above-ground plant parts.
  • Capitate-Sessile: The second type of gland is much larger and is more numerous than the bulbous glands. They are called capitate, which means having a globular-shaped head. On immature plants, the heads lie flush, appearing not to have a stalk and are called capitate sessile. They actually have a stalk that is one cell high, although it may not be visible beneath the globular head. The head is composed of usually eight, but up to 16 cells, that form a convex rosette. These cells secrete cannabinoids, and related compounds which accumulate between the rosette and its outer membrane. This gives it a spherical shape. The gland measures from 25 to 100 micrometres across.
  • Capitate-Stalked: Cannabinoids are most abundant in the capitate-stalked gland which consists of a tier of secretory disc cells subtending a large non-cellular secretory cavity. During flowering the capitate glands that appear on the newly formed plant parts take on a third form. Some of the glands are raised to a height of 150 to 500 micrometres when their stalks elongate. These capitate-stalked glands appear during flowering and form their densest cover on the female flower bracts. They are also highly concentrated on the small leaves that accompany the flowers. The male flowers have stalked glands on the sepals, but they are smaller and less concentrated than on the female bracts. Male flowers form a row of very large capitate glands along the opposite sides of anthers.

picture for trichrome article File links The following pages link to this file: Trichome ... picture for trichrome article File links The following pages link to this file: Trichome ... Look up Cannabis in Wiktionary, the free dictionary. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. ... Cells in culture, stained for keratin (red) and DNA (green). ... Cannabinoids are a group of chemicals which activate the bodys cannabinoid receptors. ... In biology, cuticle or cuticula refers to a more or less tough (but flexible) non-mineral covering of an organism, or part of it. ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... Flower of the Primrose Willowherb (Ludwigia octovalvis) showing petals and sepals A sepal is one member or part of the calyx of a flower. ...

Active ingredients

  • THC: delta-9-tetrahydrocannabinol and delta-8-tetrahydrocannabinol - THC mimics the action of anandamide, a neurotransmitter produced naturally in the body, which binds with the cannabinoid receptors in the brain to produce the ‘high’ associated with marijuana. THC possesses high UV-B (280-315 nm) absorption properties.
  • THCV: tetrahydrocannabivarin - prevalent in certain South African and Southeast Asian strains of cannabis. It is said to produce a ‘clearer high’ and seems to possess many of the therapeutic properties of THC.
  • CBD: cannabidiol - previously believed to be psychoactive, or to contribute to the high by interacting with other cannabinoids, conversely the most recent research indicates that CBD has negligible effect on the high, it is however a strong anti-inflammatory, and may take the edge off some THC effects, such as anxiety. CBD as a non-psychoactive cannabinoid appears to be helpful for many medical conditions. CBD biosynthesizes into cannabinol (CBN) & tetrahydrocannabinol (THC).
  • CBN: cannabinol - a degradation product of THC, produces a depressant effect, ‘fuzzy’ forehead.
  • CBC: cannabichromene - non-psychoactive , a precursor to THC.
  • CBG: cannabigerol - non-psychoactive, hemp strains often possess elevated levels of CBG while possessing only trace amounts of THC.

Tetrahydrocannabinol, also known as THC, Δ9-THC, Δ9-tetrahydrocannabinol (delta-9-tetrahydrocannabinol), Δ¹-tetrahydrocannabinol (using an older numbering scheme), or dronabinol, is the main psychoactive substance found in the Cannabis plant. ... Tetrahydrocannabinol, also known as THC, Δ9-THC, Δ9-tetrahydrocannabinol (delta-9-tetrahydrocannabinol), Δ¹-tetrahydrocannabinol (using an older numbering scheme), or dronabinol, is the main psychoactive substance found in the Cannabis plant. ... Anandamide, also known as arachidonoylethanolamine or AEA, is a naturally occurring endogenous cannabinoid neurotransmitter found in the brain of animals, as well as other organs. ... Chemical structure of D-Aspartic Acid, a common Amino Acid neurotransmitter. ... A Cannabis sativa plant The drug cannabis, also called marijuana, is produced from parts of the cannabis plant, primarily the cured flowers and gathered trichomes of the female plant. ... Tetrahydrocannabivarin, also known as tetrahydrocannabivarol, THCV, or THV, is a psychoactive cannabinoid found in minor amounts in the hemp plant Cannabis sativa. ... Cannabidiol, also known as CBD, is a non-psychoactive cannabinoid found in the hemp plant Cannabis sativa. ... A psychoactive drug or psychotropic substance is a chemical that alters brain function, resulting in temporary changes in perception, mood, consciousness, or behaviour. ... Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. ... Anxiety is a complex combination of emotions that includes fear, apprehension and worry, and is often accompanied by physical sensations such as palpitations, nausea, chest pain and/or shortness of breath. ... Cannabinol, also known as CBN, is a non_psychoactive cannabinoid found in the hemp plant Cannabis sativa. ... See also sedative. ... A precursor is something that existed before and was incorporated into something that came later. ...

See also

A seta is a stiff hair, wierd, culy, things bristle, or bristle-like process or part of an organism. ... Kief or kif is the dried resin glands (or trichomes) of cannabis, which accumulates on containers or has been removed with a kiefing screen or sieve. ...


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

  Results from FactBites:
Trichome Summary (1613 words)
Trichomes are single or multicellular outgrowths of the plant epidermis and collectively constitute the pubescence (hairiness) of the plant surface.
Trichomes of this type are common in the nightshade family (Solanaceae) and plant breeders have created new varieties of potatoes (Solanum) and tomatoes (Lycopersicon) that resist insect pests because of glandular hairs on their leaves and stems.
A common type of trichome is the scale or peltate hair: a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind.
Definition: trichome from Online Medical Dictionary (133 words)
The cells in the trichome are usually separated by septa but some of the adjacent cells can communicate with one another via small pores (microplasmodesmata) which are not found in a simple chain of bacterial cells such as chains of streptococci.
The cells of a trichome may or may not be covered by a common sheath.
Trichomes are formed by many cyanobacteria and for example by species of Beggiatoa.
  More results at FactBites »



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