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Urticaceae

Nettle family of plants

  • 5 min read
  • 6 chapters
Description: Urtica dioica - Brennnessel: Blüten Source: selbst fotografiert Date: 4. Sep. '05 14h Photographer: Michael Gasperl ( Migas ) Location: AUT/OÖ/Steyr/an der Enns
No machine-readable author provided. Migas assumed (based on copyright claims). · CC BY 3.0

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The family includes about 2,625 species, grouped into 53 genera. The largest genera are Pilea (500 to 715 species), Elatostema (300 species), Urtica (80 species), and Cecropia (75 species). Cecropia contains many myrmecophytes.

Urticaceae species can be found worldwide, but most species are found in tropical ecosystems, especially tropical Asia.

Description

Urticaceae species can be herbs (e.g. Urtica, Parietaria), shrubs(e.g. Pilea), hemi-epiphytes, or, rarely, trees (Dendrocnide, Cecropia). Their leaves are usually entire and bear stipules.

Urticating hairs are often present. Stinging trichomes on the leaves break upon contact, imbedding a sharp tip into animal skin which is filled with an irritating liquid. This liquid consists of compounds such as histamines and acetylcholines that create an irritating skin reaction. These urticating trichomes are an herbivory defense against primarily mammals, but also defend against invertebrate herbivory as well.

Urticaceae flowers are typically unisexual, with rare cases of functionally hermaphroditic flowers. Pistillate flowers have superior pseudomonomerous ovaries extending to one style. This family has a gynoecium with two carpels, and a perianth of four to five. Urticacids explosively release their pollen when their urticaceaous stamens dry in the heat, causing the filaments to straighten and the anthers to release pollen in a swift motion. Plants are then wind-pollinated. Fruits are achenes.

Additional characteristics represented by members in the family are leaves with cystolith or silicone accumulation. Some members exhibit latex presence only in the bark as an anti-herbivory defense.

While the stings delivered by Urticaceae species are often unpleasant, they seldom pose any direct threat to health, and deaths directly attributed to stinging are exceedingly rare; species known to cause human fatalities include Dendrocnide cordata and Urtica ferox.

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