Thorn (botany)

Schematic longitudinal section of the spike (A) and spike (B). The wooden body of a thorn arises from the wooden body (yellow with dots) of the carrying branch, the thorn is in the armpit of a carrying blade or its leaf scar (not shown); on the other hand, a sting emerges exclusively from bark tissue (green).

A thorn is a stinging structure on a plant that sits in the place of an organ . Thorns are thus transformed shoot axes , leaves , stipules or roots . Their identity can be recognized by their position, partly also through transitional formations. Thorns are always traversed by vascular bundles . This distinguishes them from the similar spines , which, however, are formed as emergence only by epidermis and cortical tissue. In common parlance, the two terms are usually not differentiated according to this definition, so from a botanical point of view a rose does not have the proverbial thorns, but thorns.

Thorns are used to ward off herbivores and for climbing.

Thorn species

In native woody plants, shoot thorns are mostly remodeled short shoots : Examples are sloe ( Prunus spinosa ) and hawthorns ( Crataegus ). The buckthorn ( Rhamnus cathartica ) forms long spines .

The barberry ( Berberis vulgaris ) forms leaf thorns . Here the leaf thorns sit on long shoots, leafy short shoots emerge from the axils of the thorns in the same year. The cactus plants also develop leaf thorns, which, however, are often called spines. Only one emerging leaf vein can form a thorn, in some thistles from the leaf tips, in the common hollow tooth ( Galeopsis tetrahit ) from the calyx tip . The thorns that emerge from individual leaflets in some climbing palms , such as Eremospatha , are known as acanthophylls .

Stipule thorns (stipular thorns) are often paired, horny to woody stipules. They are, for example, in the black locust ( Robinia pseudacacia ) in acacia ( Acacia ) and the Crown of Thorns ( Paliurus spina-christi before).

Root thorns are rare and occur in the aboveground parts of the sprouting roots of some palm trees such as Acanthorrhiza , Cryosophila and Mauritia .

Thorns are very common in plants on arid locations, in xerophytes and succulents . A characteristic example is the genus milkweed ( Euphorbia ), in which different thorn formations occur: widespread stipule thorns, besides long sprout spines ( Euphorbia lignosa , Euphorbia gariepina ), sterile inflorescence stalks ( Euphorbia horrida , Euphorbia enopla ) and leaf-base spines ( Euphorbia hamata ).

Shoot thorns (short shoots) of the single hawthorn ( Crataegus monogyna )
Leaf thorns of barberry ( Berberis vulgaris )
Leaflets of Encephalartos horridus transformed into thorns .
Young Robinia with 15 mm long stipple thorns (= stipple thorns).

Thorns in art

Just as the rose is a symbol of love, the thorns (see the confusion with thorns mentioned above) represent those of suffering . In the fine arts they are also a frequent floral motif for injury and blood - see also Christ's crown of thorns .

The poetry used the thorns as such a symbol, but also knows many puns and proverbs this content. Some examples of this:

Theodor Storm ( July ): "The grain lowers its ears / red berries swell on the thorn"
Idiom: "be a thorn in the side"
Proverb: "No rose without thorns".

In heraldry , the municipality coat of arms of Dörentrup shows several thorns.

literature

Peter Sitte , Elmar Weiler , Joachim W. Kadereit , Andreas Bresinsky , Christian Körner : Textbook of botany for universities . Founded by Eduard Strasburger . 35th edition. Spektrum Akademischer Verlag, Heidelberg 2002, ISBN 3-8274-1010-X .
Hanno Richter: Allgemeine Botanik, script University of Natural Resources and Life Sciences, 2005. (PDF; 233 kB) ( Memento from September 29, 2007 in the Internet Archive ) (especially examples)

Web links

Commons : Sprout thorns - collection of images, videos and audio files

Commons : Leaf thorns - collection of images, videos, and audio files

Wiktionary: Dorn - explanations of meanings, word origins, synonyms, translations

Individual evidence

^ Gerhard Wagenitz : Dictionary of Botany. The terms in their historical context . 2nd expanded edition. Spectrum Academic Publishing House, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 88 .
^ Manfred A. Fischer, Karl Oswald, Wolfgang Adler: Excursion flora for Austria, Liechtenstein and South Tyrol . 3rd, improved edition. Province of Upper Austria, Biology Center of the Upper Austrian State Museums, Linz 2008, ISBN 978-3-85474-187-9 , p. 76 .
^ John Dransfield, Natalie W. Uhl, Conny B. Asmussen, William J. Baker, Madeline M. Harley, Carl E. Lewis: Genera Palmarum. The Evolution and Classification of Palms . Second edition, Royal Botanic Gardens, Kew 2008, ISBN 978-1-84246-182-2 , p. 651.

[1] Gerhard Wagenitz : Dictionary of Botany. The terms in their historical context . 2nd expanded edition. Spectrum Academic Publishing House, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 88 .

[2] Manfred A. Fischer, Karl Oswald, Wolfgang Adler: Excursion flora for Austria, Liechtenstein and South Tyrol . 3rd, improved edition. Province of Upper Austria, Biology Center of the Upper Austrian State Museums, Linz 2008, ISBN 978-3-85474-187-9 , p. 76 .

[3] John Dransfield, Natalie W. Uhl, Conny B. Asmussen, William J. Baker, Madeline M. Harley, Carl E. Lewis: Genera Palmarum. The Evolution and Classification of Palms . Second edition, Royal Botanic Gardens, Kew 2008, ISBN 978-1-84246-182-2 , p. 651.