Schwenckia
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Schwenckia is a genus of plants fromthe nightshade family (Solanaceae). The 25 species occur in tropical and subtropical regions of Central and South America , one species can also be found as a ruderal plant in East Africa .
description
Vegetative characteristics
Schwenckia are annual or perennial plants that grow upright, creeping or, in exceptional cases, climbing and grow to a height of 0.4 to 1.5 (2.5) m. The plants are covered with glandular and non-glandular trichomes , drusen are formed in the cortex and marrow cells , as well as in the leaves ( mesophyll cells). The cortex cells of the trunk show Caspary stripes . Crystal sand does not appear in the plants.
The leaves are usually stalked with petioles a length of (0.4) 2 to 25 mm, occasionally they are almost or completely sessile. The leaf blades are (0.3) 2 to 9 cm in length.
Inflorescences and flowers
The axillary or terminal inflorescences are often racemose or panicley , the inflorescence stalks then have a length of (0.5) 2 to 4 (16) mm. Sometimes, however, the inflorescences only consist of a single flower or they are in groups of up to three flowers. The calyx tube is tubular to bell-shaped, radially symmetrical or slightly zygomorphic and has a length of 2.5 to 4 (12) mm. The mostly triangular corolla lobes or teeth have three longitudinally directed nerves, they are as wide as they are long or longer, are shorter than the calyx tube or, in exceptional cases, slightly longer. The yellow, greenish or purple crown is radial symmetry or zygomorphic, 8 to 30 mm long, only in the species Schwenckia micrantha is the length only 2 to 3 mm. The corolla-tube is narrowly tubular, straight or, as an exception, curved. The coronet is narrow, consists of five corolla lobes, which can be very complex and bizarre in shape.
The androeceum usually consists of two fertile stamens and three staminodes reduced to the stamens , which can be very short or long. Four fertile stamens are formed in only five or six species, which then appear in two different forms. The stamens are generally cylindrical, slightly awl-shaped or strongly indented. They are hairless or hairy and about three to nine times as long as the anthers. The stamens are fixed to the corolla tube at different heights - either at the lower edge of the tube, at the upper edge of the tube or in the middle between both edges. The anthers are ventrally fused with the stamens, mostly narrow-elliptical, in exceptional cases egg-shaped, occasionally almost fused together, in exceptional cases protruding beyond the crown. They are (0.5) 1 to 1.8 (2) mm long, only in Schwenckia micrantha they hardly reach a length of 0.2 to 0.4 mm. The counters for the dust bags are slightly different in size and are separated from each other in the lower quarter. The pollen is slightly elongated or elongated-spherical and relatively small with a size of 12 to 18 µm.
The carpel is bilobed and has many opposing (anatropic) ovules . The nectaries are everted, bowl-shaped and sometimes quite wide. The scar is small and disc-shaped, head-shaped or disc-shaped.
Fruits and seeds
The fruits are spherical or occasionally egg-shaped capsules that can be pointed. They have a diameter of (2) 3.5 to 5 (7) mm and are usually longer than the calyx, which enlarges during fruit ripening. They consist of two completely formed, smooth fruit capsule compartments. Usually the fruits contain ten to 20 (or 40) seeds , sometimes 50 to 70 or even just under six to 14. They are mostly 0.6 to 0.8 (1) mm long, in Schwenckia micrantha only 0.3 to 0.4 mm, are cube-shaped, the surface is structured like a network. The embryo lies straight in the seed, the cotyledons are shorter than the rest of the embryo, endosperm is abundant.
Chromosome number
Chromosome numbers are known from the species Schwenckia lateriflora (Vahl) Carvalho , where a base chromosome number of was determined. In Schwenckia americana D. Royen ex L. 2n = 20 was found.
ingredients
In the roots were tigogenin and gitogenin , two steroid - glycosides detected.
Occurrence
The species of the genus Schwenckia occur in the tropical and subtropical regions of Central America to the Antilles in northeast Argentina . Brazil and Venezuela are the countries with the largest number of species with 16 and nine species respectively. The most common species Schwenckia americana has been known as a ruderal plant in East Africa, especially from Senegal , Guinea and Sierra Leone , since the early 19th century .
Systematics
Within the genus Schwenckia there are 25 species. The genus is classified within the systematics of the nightshade family by William D'Arcy and Armando Hunziker in the tribe Schwenckieae of the subfamily Cestroideae, in the systematics according to Richard Olmstead they are placed in a separate subfamily Schwenckioideae.
Here is a selection of the types:
- Schwenckia americana D. Royen ex L.
- Schwenckia lateriflora (Vahl) Carvalho
- Schwenckia micrantha Benth.
Botanical history and etymology
The genus was first described in 1764 by Carl von Linné in the 6th edition of his work " Genera Plantarum ". As an author he names " David van Royen ". In the heading describing the genus he calls this " Schwenkia ", ie without the "c" in front of the "k", in the naming of the species he writes " Schwenckia americana ". This different spelling of the generic name often led to the fact that both spellings were used in parallel in the literature. In addition, instead of the correct page number 577, 567 is incorrectly indicated on the genus description page, which can also be found in numerous works as an indication of the first description. By choosing the generic name, Linné honored Martin Wilhelm Schwencke (1707–1785), a botanist and physicist from The Hague . He wrote, probably delighted about this honor, in 1766 an eight-page publication on the genre named after him. This publication was quoted in the next edition by Linnés in 1767, probably without his having read it himself. He standardized the spelling of the generic name on " Schwenkia ". However, since Linnaeus did not Latinize the "ck" in similar names, such as in the genera Baeckea or Osbeckia , it is assumed that this is an oversight, so the correct generic name must be Schwenckia .
literature
- Armando T. Hunziker: The Genera of Solanaceae . ARG Gantner Verlag KG, Ruggell, Liechtenstein 2001, ISBN 3-904144-77-4 .
Individual evidence
- ↑ Schwenckia americana at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
- ↑ Cf. JAM van Balken: Overview of Solanaceae Species ( Memento of the original from September 29, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , online.
- ↑ RG Olmstead et al .: Phylogeny and Provisional Classification of the Solanaceae Based on Chloroplast DNA (PDF; 131 kB) . In Solanaceae IV, Advances in Biology and Utilization , editors: M. Nee, DE Symon, JP Jessup, and JG Hawkes, Royal Botanic Gardens, Kew. 1999. Pages 111-137.
- ↑ Lotte Burkhardt: Directory of eponymous plant names . Extended Edition. Botanic Garden and Botanical Museum Berlin, Free University Berlin Berlin 2018. online
- ^ H. Heine: On the Correct Spelling of the Generic Name Schwenckia D. van Royen ex L. (Solanaceae), with a note about Martin Wilhelm Schwencke. In: Kew Bulletin , Volume 16, Number 3, 1963. Pages 465-469.
