Haustorium
A haustorium (plural haustoria) is a suction organ for nutrient uptake, with which a plant or a fungus absorbs substances such as water or nutrients from another part of its own individual or from a foreign organism. Haustoria are of extremely different types:
- Parasitic seed plants penetrate the host plant with haustoria and make contact with their vascular bundles .
- In fungi, especially in the form of lichen , individual hyphae can be developed as haustoria. In the lichens, the mushroom houses lie close to the algae cells ( appressorium ) or something penetrate them. Parasitic fungi penetrate host cells with the haustoria.
- Among the mosses , the foot of the sporogon is called the haustorium. The sporogon sits with it in the gametophyte and absorbs nutrients from it.
- The embryo of the fern plants also forms a foot, called a haustorium, with which it sticks in the prothallium .
- Also in the embryology of the bed covers there are haustoria formations which are formed from parts of the embryo sac , the embryo or the endosperm . The cotyledon ( scutellum ) of the grass fruits ( caryopses ) z. B. is designed as a suction organ, it conveys nutrients from the endosperm to the seedling .
Haustorium of parasitic flowering plants
Most parasitic flowering plants have converted their roots into haustoria, such as mistletoe . A few form their haustoria from shoot tissue, such as the devil's twine ( Cuscuta ).
The haustoria penetrate the tissue of the host plant, where they seek contact with the vascular bundle. Both xylem and phloem are tapped. The exchange of substances with the phloem is likely to take place at least partially via plasmodesma , i.e. symplastically . The mistletoe makes tissue contact through an adhesive epithelium. Its cells resemble secretion hair . In the case of the devil's twine, the haustoria grip the sieve tubes of the host plant like fingers.
literature
- 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. 137 .
Web links
Individual evidence
- ^ 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 , p. 172 .
- ↑ Walter Eschrich: Functional Plant Anatomy . Springer, Berlin 1995, ISBN 3-540-59131-1 , pp. 155 f .