Apostasioideae
| Apostasioideae | ||||||||||||
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Neuwiedia griffithii , illustration |
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| Scientific name | ||||||||||||
| Apostasioideae | ||||||||||||
| Horan. |
The Apostasioideae are a subfamily of the family of orchids (Orchidaceae). With only 17 species in two genera , it is the smallest of the five subfamilies of this plant family. At the same time, the species gathered in it are considered the most original of all orchids.
features
All representatives of the Apostasioideae are small, perennial, herbaceous plants. The roots have no velamen . The leaves are arranged in a spiral along the slender stem. In the bud the leaves are rolled, the leaf blade is plicate. There is no dividing tissue between leaf and shoot.
The inflorescences of the Apostasioideae are terminal and branched simply or racemously . The flowers are spiraling on the stem, they are small and white, yellowish to yellow in color, sometimes resupinated . The bracts are relatively large and leaf-like. The petals are in two threefold circles, the specialization of a petal as a labellum is only weak ( Neuwiedia ) or absent ( Apostasia ). The ovary is subordinate and three-chambered. The narrow stylus ends in a scar that has three identically shaped scar lobes. There are two or three fertile stamens . The middle stamen can be fully developed, reduced in size, stunted to a sterile staminodium or completely absent. The stamens are fused with each other and with the style at the base. The elongated anthers contain the powdery pollen, the individual pollen grains are not glued together. The fruits are mostly capsule fruits , but rarely also berry-like . They contain numerous round seeds that are about 300 µm in size and have a hard seed coat.
Chromosome numbers of 2n = 48 in Apostasia and 2n = 96 in Neuwiedia were found, Okada deduces from this a base number of x = 12. The chromosomes are very small.
Some species self-pollinate, others are pollinated by bees, which use vibrations in the flower to remove the pollen.
Distribution and habitat
The species of the Apostasioideae are found exclusively in Asia from Nepal, southern China and Japan to New Guinea and in the far north of Queensland , Australia. They grow there in ever-humid climates in forests that are between 200 and 2200 m high.
Systematics
Although the internal systematics of the two genera and their relationship to one another was mostly undisputed, the taxonomic position of the subfamily has been discussed many times. The main controversial issue is whether the Apostasioideae should actually be incorporated into the orchid family or should be viewed as a separate family, Apostasiaceae or Neuwiediaceae. Molecular genetic studies support the integration into the Orchidaceae and confirm the relationship between the two genera. A position as a sister taxon to all other orchids is being discussed.
Individual evidence
- ↑ a b c d Traudel Rübsamen: Morphological, embryological and systematic studies on Burmanniaceae and Corsiaceae (with a view of the Orchidaceae-Apostasioideae). J. Cramer, Berlin 1986. ISBN 3-443-64004-4
- ↑ H. Okada: Karyomorphological observations of Apostasia nuda and Neuwiedia veratrifolia (Apostasioideae) Orchidaceae. in: Japanese Journal of Botany. Tokyo 63.1988, 344-350. (Quoted from Dressler (1993))
- ↑ KM Cameron et al.: A phylogenetic analysis of the Orchidaceae: evidence from rbcL nucleotide sequences. in: American Journal of Botany. Columbus 86.1999, 208-224. ISSN 0002-9122
literature
- Robert L. Dressler: Phylogeny and Classification of the Orchid Family . Cambridge University Press, Cambridge 1993, pp. 83ff. ISBN 0-521-45058-6
Web links
- PF Stevens: Angiosperm Phylogeny Website. May 2006, accessed August 9, 2009 .
