Spermogony
The spermogony or the spermogonium is a form of the spore camp, which occurs mainly in the secondary fruit form of the rust fungi (Pucciniales), but also in other fungi . Spermogonia are mycelial structures that produce small, mononuclear spores called spermatia . They usually appear as small, dark warts on the host's surface and are the first single-core form in rust fungi from germinating basidiospores . In addition to the production of spermatia, they also serve to absorb them and thus fertilize the mycelium with cell nuclei of a different mating type . This exchange takes place via wind propagation or via insects , which serve as vectors. For this purpose, spermogonia often produce sweet nectar . Spermatia can function as both a fertilizing cell and a conidia ; In a narrower sense, spermogonia only include those spore stores that serve both fertilization and spreading. Since the ecology of many mushrooms has often not been adequately researched, the term pyknia is usually used in unclear cases .
Origin and structure
Spermogonia can have very different structures. There are spherical and dome-shaped spermogonia in which the sperm-producing layer is arranged either in a bowl-shaped or flat manner. This layer produces relatively small spores through asexual division and, in rust fungi, initially grows under the epidermis before it emerges from it in the later stages. With the naked eye, spermogonia can usually only be seen as small, dark bumps or through the discolored surroundings. Often the spore-producing layer is surrounded by convoluted hyphae that serve as receptive hyphae . The entire mycelium of a spermogony arises from a mononuclear, germinating basidiospore and is consequently also mononuclear. In order to get to cell nuclei of a different pairing type, which are necessary for the sexual reproduction of the fungi, but many spermogonia secrete sticky, sweet nectar . It contains spermatozoa and attracts insects, which carry the spores of the fungi from plant to plant. As a result, they not only contribute to the spatial distribution, but also supply the unisexual spermogonia with the nuclei they lack.
Once the conception hyphae have taken in the appropriate nuclei, they form a double-nucleus mycelium through cell division , which is still haplontal . Aecia arise from this mycelium , which then produce dinuclear spores. These in turn form the basis for telienes , in whose teliospores the nuclei finally fuse and a new set of chromosomes is created. In 1927, John Hubert Craigie was able to demonstrate for the first time that the hyphae and spores of spermogonia function as gametes . Up until then, their role in the rust fungus life cycle had been unclear.
Taxonomic meaning
Unlike Aecien, Uredien and Telien, spermogonia are not used directly as a taxonomic criterion because they always occur together with Aecien. Although their respective structure is often decisive if two similar species are to be distinguished, it is not a basis for form taxa such as Telien or Aecien. However, rust spermogonia can be divided into different groups according to their morphology , which in turn provided an important basis for the classification of this group before molecular genetic analyzes were available.
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literature
- Heinrich Dörfelt , Gottfried Jetschke (Ed.): Dictionary of mycology . 2nd Edition. Spectrum, Academic Publishing House, Heidelberg a. a. 2001, ISBN 3-8274-0920-9 .
- Y. Hiratsuka, S. Sato: Morphology and Taxonomy of Rust Fungi . In: KJ Scott, AK Chakravorty (Ed.): The Rust Fungi . Academic Press, London a. a. 1982, ISBN 0-12-633520-6 , pp. 1-34 .
