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Hairs  [ Botany ]

Dictionary of botanic terminology - index of names

Adjective: Hairy
Trichomes, Seta,  Bristle, Pubescence
  In botany  the hairs (also called trichomes or pubescence) are fine outgrowths or appendages on plantís epidermis. These have diverse structure and function.  

Hairs on plants are extremely variable in their presence across species, location on plant organs, density (even within a species), and therefore function. However, several basic functions or advantages of having surface hairs can be listed:

  1. Defence against herbivores:  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.

  2. Reduction of frost damages:  Hairs on plants growing in areas subject to freeze keep the frost away from the living surface cells.

  3. Protection from wind:  In windy locations, hairs break-up the flow of air across the plant surface, reducing evaporation.

  4. Reflection of solar radiation:  Dense coatings of hairs reflect solar radiation, protecting the more delicate tissues underneath in hot, dry, open habitats.

  5. Absorption of moisture from dew and fog:  In locations where much of the available moisture comes from cloud drip, hairs appear to enhance this process.

The surface appearance of plant's organs, such as stems and leaves, are mainly characterized by the presence of trichomes and many terms are used in reference to the presence, form, and appearance of them.  
See: surface features.

There are several terms dealing whit hairs the most basic are glabrous (lacking hairs)  and pubescent (having hairs), following some of the more common terms. 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). Any of the various types of hairs may be glandular.





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