Melon leaf nightshade
| Melon leaf nightshade | ||||||||||||
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Melon leaf nightshade |
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| Solanum citrullifolium | ||||||||||||
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The melon leaf nightshade ( Solanum citrullifolium ) is a species of the genus nightshade ( Solanum ) in the nightshade family (Solanaceae). The species is native to northern Mexico and Texas , a total of three varieties are distinguished.
description
Vegetative characteristics
The melon leaf nightshade forms annual, 30 to 80 cm high, herbaceous plants armed with thorns , which are widely spread. The rungs are green and have a rotating cross-section with a diameter of 3 to 9 mm; they are densely to sparsely bristled or prickly and usually covered with simple, glandular trichomes 0.3 mm in length. Longer, single-row trichomes with a length of up to 0.7 mm are rarely found on the younger shoots. The sympodial units have two leaves that are more or less opposite.
The foliage leaves are broadly ovate and double pinnately lobed, and are usually indented at the base. The individual leaf lobes are blunt or rounded, the leaf blades are 4 to 10 cm long. There are spines on the main veins; Various glandular and occasionally some simple, straight trichomes with a length of up to 0.8 mm can be found on the upper side of the leaf. On the underside there are roughly distributed trichomes, star-rayed and glandular with a few rays. The petioles are up also occupied as long as the leaf blade and barbed.
Inflorescences and flowers
The melon leaf nightshade blooms from July to October. The inflorescences are between the nodes ( concave formation ), are 5 to 11 cm long and consist of six to ten flowers . The calyx is lanceolate linear in the flowering stage one-half to two-thirds in divided pointed lobes. The calyx tube is bell-shaped and 1.7 to 2.6 mm long. The star-shaped, five-fold, purple or blue crown has a diameter of 2.5 to 3.5 cm and narrow to broad triangular corolla lobes. There are two different forms of stamens within a flower : On the one hand, a single long stamen with a 1.1 to 1.6 cm long anthers, this is pointed from the center of the flower pointing downwards, at the tip again bent inwards and overflowing with purple . On the other hand, the flower has four short, completely yellow stamens with 6 to 10 mm long anthers. These are arranged in a circle in the center of the flower. The ovary is bare and deeply integrated into the developing cup tube, the slender pen is 1 to 1.6 mm long, the scar is not widened.
Fruits and seeds
The fruit is a spherical berry with a diameter of 8.5 to 11.5 mm, which stands on a 9 to 13 mm long fruit stalk and is completely enclosed by the enlarged, close-fitting and spiked calyx tube. When ripe, the fruit dries up and pops up. About 30 to 60 lenticular seeds are formed per fruit . These are dark brown and 2.3 to 2.9 mm long; their surface is reticulated, wavy or furrowed with weak radial ridges.
Other specifications
The melon leaf nightshade has a chromosome base number of . A study found various flavonoids and flavones in the leaves , the composition of which is characteristic of the species. There are typically various 3-O- glycosides , 6, 8-diC- glycosylapigenin and, among other things, derivatives of 8-hydroxy myricetin that have been detected for the first time in this type . The varieties Solanum citrullifolium var. Citrullifolium and Solanum citrullifolium var. Setigerum show differences in the flavonoid composition: the former contains an 8-O-glycoside of 8- hydroxyquercetin , the latter is an 8-hydroxymyricetin-based aglycon and apigenin 7-O -Glucoside to be found. The variety Solanum citrullifolium var. Knoblochii was not investigated in this study.
ecology
The pronounced duality of the stamens is typical of the Solanum section of Androcera and thus also causes a special pollination ecology in the melon leaf nightshade. The single, larger stamen is curved downwards, but points with the tip towards the center of the flower. Due to the violet color of this stamen, the four remaining yellow stamens remain the primary target for various bees (Apiformes) as pollinators. As with other nightshades, the bees bend around these stamens and, by vibrating and humming, loosen the pollen that lands on the bee's belly and is later distributed on the rail brush. However, the abdomen touches the tip of the longer stamen, so that pollen is also deposited there. The position of the stylus means that it is usually pollinated with pollen from the longer stamens when larger bees, for example of the genera bumblebees ( Bombus ), wooden bees ( Xylocopa ) and Protoxaea visit the flowers. However, the pollen formed in the shorter stamens is also fertile.
Distribution and location
The melon leaf nightshade is found in Mexico in the east of the state of Chihuahua and in the west of the state of Coahuila ; in the US state of Texas , the distribution area in the Trans-Pecos area extends west of the Pecos River . Isolated occurrences of the species exist in western Chihuahuas and central Texas.
The plants grow on limestone, lava, sand, on alluvial soil, in calcareous and salty plains, often also around moist depressions, on lightly overgrown mountain slopes, on dry grasslands and in ruderal areas. In overgrazed and ruderal areas, the plant can quickly become an annoying weed.
Systematics
External system
Solanum citrullifolium is a typical representative of the subgenus Solanum subgenus Leptostemonum of the nightshade family (Solanum). In the division of sections according to Whalen (1979), the species is placed in the Androceras section , Violaceifolium series . Molecular biological studies of 112 of the subgenus Leptostemonum , comprising 350 to 400 species, showed that the groups around Solanum rostratum (to which the melon leaf nightshade also belongs) and around Solanum crinitum together with the previously unplaced species Solanum mitlense resulted in a monophyletic clade , described by Whalen in 1984 . The cladogram with the species studied by Levin looks like this:
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According to the cladogram
Internal system
The species is divided into three varieties , some of which have separate distribution areas.
- Solanum citrullifolium var. Citrullifolium : The shoots of the nominate form are covered with a maximum of 20 spines per centimeter, these are 3 to 7 mm long and up to 1 mm thick. There is thick hair on the younger shoots in particular. The fruits stand on upward-pointing stems. This variety occurs in two geographically separated areas. The main area extends from northern to central Coahuila to the Davis Mountains in western Texas. The second distribution area is isolated in central Texas, the first description of the species was based on a plant grown from seeds from this distribution area. The outermost leaf lobes of these plants are more rounded than the plants in the main area, the star-shaped trichomes on the underside of the leaves are almost completely absent and the inflorescences enlarge more as the fruit ripens. This central Texas form is considered to be very rare, it has only been collected twice (1930 and 1949).
- Solanum citrullifolium . Var knoblochii Whalen : This variety is similar to nominate at most properties, however, is geographically separated from her Solanum citrullifolium var. Knoblochii comes only in a limited area to the west of the state of Chihuahua, at altitude in Tarahumara ago. The spines standing on the shoot are 2 to 4 mm long, the pale blue crown often has whitish spots on the adhesions of the petals. The hairs are whitish, many of the trichomes reach lengths of 2 to 3 mm. The fruits have stems that are arranged at right angles to the main axis of the inflorescence.
- Solanum citrullifolium var. Setigerum Bartlett : This variety is characterized above all by its very strong reinforcement. There are 25 or more 4 to 8 mm long spines per centimeter of the stem axis, but their diameter hardly exceeds 0.5 mm. The variety is found in eastern Chihuahua to western Coahuila, and occasionally in Presidio County (Texas).
Botanical history and etymology
The species was first described in 1849 by Alexander Braun on the basis of a plant grown in the botanical garden in Freiburg . The holotype was probably destroyed, but an isotype made by the same plant exists in the herbarium of the Missouri Botanical Garden .
The specific epithet citrullifolium refers to the shape of the leaves, which are similar to those of the watermelon . The German name is a literal translation of the art epithet.
swell
- ↑ a b c d e f g PBI Solanum: Solanum citrullifolium , online, accessed October 23, 2007.
- ↑ Michael D. Whalen: Foliar Flavonoids of Solanum Section Androceras: A Systematic Survey . In: Systematic Botany , Volume 3, Number 3. (Fall 1978), pages 257-276. doi : 10.2307 / 2418297
- ↑ Michael D. Whalen: Reproductive Character Displacement and Floral Diversity in Solanum Section Androceras . In: Systematic Botany , Volume 3, Number 1. (Spring 1978), pages 77-86. doi : 10.2307 / 2418533
- ↑ a b PBI Solanum: Solanum citrullifolium var.citrullifolium , online, accessed October 28, 2007.
- ↑ a b PBI Solanum: Solanum citrullifolium var.setigerum , online, accessed October 28, 2007.
- ↑ a b Rachel Levin, Nicole Myers, Lynn Bohs: Phylogenetic Relationship among the “Spiny Solanums ” (Solanum subgenus Leptostemonum, Solanaceae). In: American Journal of Botany , Volume 93, Number 1, 2006. Pages 157-169.
- ↑ PBI Solanum: Solanum citrullifolium var.knoblochii , Online, accessed October 28, 2007.
- ↑ Michael D. Whalen: New Taxa of Solanum, Section Androceras from Mexico and Adjacent United States. In: Wrightia , Volume 5, Number 7, May 1976. Pages 228-238.
Web links
- GRIN taxonomy
- Herbarium evidence of the isotype specimen from the Missouri Botanical Garden
