Trichomes, from the Greek meaning "growth of hair", are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.

Algal trichomes

Certain—usually filamentous—algae, have the terminal cell produced into an elongate "hair-like" structure called a trichome. The same term is applied to such structures in some cyanobacteria.

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-minute tree). Also, there are "nontrichomatous" epidermal cells that protrude from the surface.

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.

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:
* 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.

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. 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.

See also

* Seta
* Kief


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

* [ What are Trichomes?]

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Look at other dictionaries:

  • Trichome — Trich ome, n. [See {Trichomatose}.] (Bot.) A hair on the surface of leaf or stem, or any modification of a hair, as a minute scale, or star, or gland. The sporangia of ferns are believed to be of the nature of trichomes. {Tri*chom a*tous}, a.… …   The Collaborative International Dictionary of English

  • Trichōme — (griech.), s. Haare der Pflanzen …   Meyers Großes Konversations-Lexikon

  • Trichome — Trichōme, s. Haare (der Pflanzen) nebst Abb. 742 …   Kleines Konversations-Lexikon

  • Trichome —   [griechisch], Singular Trichom das, s, die Pflanzenhaare (Haare).   …   Universal-Lexikon

  • Trichome — Trichome, Pflanzenhaare, stets aus einer einzelnen Zelle entstehende, ein oder mehrzellige Auswüchse der Pflanzenepidermis. T. sind vielgestaltig und erfüllen sehr unterschiedliche Aufgaben. Auf Absorptionsgeweben befinden sich Wurzelhaare und… …   Deutsch wörterbuch der biologie

  • trichome — [trī′kōm, trik′ōm] n. [Ger trichom < Gr trichōma, growth of hair < trichoun, to cover with hair < thrix (gen. trichos), hair] 1. any hairlike outgrowth from an epidermal cell of a plant, as a bristle, prickle, root hair, etc. 2. any of… …   English World dictionary

  • Trichome — Trichom bei der Acker Schmalwand (Arabidopsis thaliana) Drüsenhaare als Klebfalle am …   Deutsch Wikipedia

  • Trichome — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Un trichome (du grec signifiant « croissance de poils ») peut signifier : En botanique, un trichome désigne de fines excroissances ou… …   Wikipédia en Français

  • trichome — ● trichoma ou trichome nom masculin (grec trikhôma, chevelure) Accumulation de poussières, de matières sébacées, de croûtes et de parasites sur les cheveux, formant une calotte nauséabonde. trichoma [tʀikɔma] ou trichome [tʀikom] n. m. ÉTYM.… …   Encyclopédie Universelle

  • trichome — noun Etymology: German Trichom, from Greek trichōma growth of hair, from trichoun to cover with hair, from trich , thrix hair Date: 1875 a filamentous outgrowth; especially an epidermal hair structure on a plant …   New Collegiate Dictionary

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