In business, the importance of gymnosperms is
Various suggestions exist side by side and one after the other for the systematic classification of living beings. The taxon dealt with here does not correspond to the systematics currently used in the German-language Wikipedia or is out of date.
The Naked seed plants (Gymnospermae, from ancient Greek γυμνόςgymnós "Naked" and ancient Greek σπέρμαsperm "Germ", "Same" - literally "naked seed"), short More naked. More naked form the group of Gymnospermae, which is divided into the subdivision Coniferophytina with the classes Ginkgoatae and Pinatae and the subdivision Cycadophytina with the classes Cycadatae and Gnetalae. The seed ferns form the class Lyginopteridatae.
The naked plants are seed plants (Spermatophytina), whose ovules are not enclosed in an ovary as in the flowering plants. In contrast to angiosperms, the carpels are not completely closed. This represents the original state within the seed plants. In contrast to earlier taxonomy, the naked samos are now viewed as a monophyletic group, that is, as a natural related group.
Since the Upper Permian, 270 million years ago (Ma), the groups of naked samers developed. Later, in the Middle Cretaceous, 120 million years ago, the Bedecktsamer developed (individual precursors are already known from the Upper Jurassic). All bare-seeded taxa are now relic groups. Compared to the hundreds of thousands of species there are now only a good five hundred species. Even the higher taxa like classes often contain only a few species. The areas are often disjoint, which also shows that these groups are only relics. The Nacktsamer had the peak of their development with most of the species in the Jura, among other things they served as food for many dinosaurs. Today the coniferous plants (Pinophyta) alone are rich in species and widespread, with over 350 species. Fossil finds give a small overview of the earlier biodiversity of the naked-seed taxa and the ecosystems that formed them at that time.
All today's naked plants are wood plants with secondary growth in thickness. The naked-seed plants differ from the bedecktsamern in the arrangement of their ducts. In addition, the ovules of the flowering plants are enclosed by carpels (carpels) and the seeds are spread through a fruit.
The flowers are separate sexes and consist only of micro- and megasporophylls (the terms stamens or carpels should be limited to the bedecktsamer). Often many flowers of one sex are grouped together in cones. Gymnosperms are usually monoecious (monoecious), but there are also dioecious (dioecious) species. The pollen is mostly spread with the help of the wind (anemophilia). But insect pollination has also been observed. The pollen then reaches the unprotected micropyle, the point of conception. In ginkgo plants (Ginkgophyta) and cycads (Cycadophyta) there are flagellated sperm cells (spermatozoids), similar to many algae. These are released from the pollen tube into a fluid-filled depression at the vertex of the nucleus (pollen chamber) so that they can swim to the egg cell. In the other groups, the pollen tube grows to the egg cell and there releases a gamete nucleus that fertilizes the egg cell. There is only a short path without barriers between pollination and fertilization. However, a lot of time can pass between the two processes.
The naked samos form a monophyletic taxon. The following are traditionally counted among the naked men:
- Cycads (Cycadophyta): with about 123 species
- Ginkgo plants (Ginkgophyta): with only one species
- Softwood family (Pinophyta): with about 365 species
- Gnetophyta: with about 69 species
See also:Systematics of the plant kingdom; Generational change
Cycas circinalis, Cycadaceae, Cycads (Cycadophyta), with pinnate leaf fronds and male inflorescence
Welwitschia mirabilis, Gnetophyta
Ephedra distachya, Gnetophyta
Ginkgo biloba, Ginkgo plants (Ginkgophyta),
Branch with leaves
- ↑ 1,01,1A. Bresinsky, Ch.Körner, J. W. Kadereit, G. Neuhaus, U. Sonnewald: Strasburger - Textbook of Botany. 36th edition, Spektrum Akademischer Verlag, Heidelberg 2008, p. 833. ISBN 978-3-8274-1455-7
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