Elaiosome

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Ricinus communis seeds with a caruncula
Strophiole on the raphe, next to the hilum, by the seed of the kidney bean

As Elaiosom ( ancient Greek ἔλαιον elaion , German , oil ' , σῶμα Sōma , German , body' ), German and oil bodies , refers to the fat tag of diaspore (seeds) of plants. It is formed by plants, the seeds of which are either spread by birds ( ornithochory ) or by ants ( myrmecochory ). In the tropics, the elaiosome is larger and more vividly colored and primarily appeals to birds. In the temperate latitudes, the elaiosomata are smaller and tailored to ants.

In tribal history, the Elaiosomata first appeared in the tropics. The adaptation to the temperate zone required a strong reduction in the size of the seeds of the plants. This ruled out ornithochore and only allowed ants to spread.

Caruncula and Strophiole

According to their place of attachment, elaiosomes are divided into caruncula (Latin, 'fleshy outgrowth') (seed callus, wart) and strophiole (Greek-Latin, 'wreath') (germ, seed wart, seed sponge bulge, umbilical bulge, wart). The caruncula, which z. B. occurs in the plant family of the milkweed family (Euphorbiaceae) and in the umbilical chickweed (genus Moehringia ), is located at the germ opening (micropyle). The strophiole is located on the funiculus or on the seed seam (raphe). Must be distinguished is the aril , seed coat, it is however expected by some authors to the Elaisomen. The sarcotesta is also sometimes counted among the elaisomes.

Elaisome-like structures can also emanate from the pericarp , exocarp of a fruit, or from the perianth, the flower axis or other forms.

Elaiosomata and ants

Elaiosomata of myrmecochores (plants that ants use to spread their seeds) contain particularly fats and sugars, and occasionally vitamin B , vitamin C , starch and protein. The elaiosome is intended for consumption only. Because of their elaiosome appendages, ants carry the diaspores into their burrow, separate the elaiosome from the diaspore and then drag the seeds that they are not interested in back out of the burrow.

Many plants that are so prepared for ants to spread their seeds grow predominantly in ant-rich forests. An elaiosome, which with its white color clearly stands out from the black seed, is formed, for example, by the native species of larkspur and fume . Even snowdrops , many violet species, the liverworts that moehringia and Spurge among the growing mainly in forests plants that form on their seed elaiosomes. A well-known example of myrmecochory in grassland plants is the autumn crocus .

The same principle can also be found in warm, dry areas with herbaceous plants and trees, as this habitat also offers ants ideal conditions. The plant species of these regions with elaiosome formation include the ox-tongues , the knapweed and, as woody plants, the acacias .

literature

  • Andreas Bresinsky : Construction, development history and constituents of the elaiosomes: studies on the myrmekochoren distribution of seeds and fruits. Schweizerbart Verlag, Stuttgart 1963 (Bibliotheca Botanica, issue 126).
  • Gustav Hegi : Illustrated flora of Central Europe. Volume III, Part 2, Second Edition, Paul Parey Verlag, Berlin and Hamburg 1979, ISBN 3-489-60020-7 .
  • Ursula Hoffmann and Michael Schwerdtfeger: ... and the golden tree of life: pleasure trips and educational trips in the realm of plants. Ulrich Burgdorf Verlag, Göttingen 1998, ISBN 3-89762-000-6 .
  • Angelika Lüttig, Juliane Kasten: Rose hip & Co: flowers, fruits and spread of European plants. Fauna Verlag, Nottuln 2003, ISBN 3-935980-90-6 .

Individual evidence

  1. ^ HN Ridley: The dispersal of plants throughout the world . L. Reeve Co., London. 1930, archive.org .
  2. ^ Bresinsky, p. 22.
  3. Hegi: Volume III / 2, p. 856 f.
  4. Elena Gorb, Stanislav SN Gorb: Seed Dispersal by Ants in a Deciduous Forest Ecosystem. Kluwer Academic Press, 2003, ISBN 1-4020-1379-5 , p. 10 f.
  5. ^ Macgregor Skene: Biology of Flowering Plants. DPH, 1993, 2006, ISBN 81-7141-205-X (Reprint), p. 413.
  6. Bresinsky, p. 29.