Melananthus

Melananthus
Systematics
	Nuclear eudicotyledons
	Asterids
	Euasterids I
Order :	Nightshade (Solanales)
Family :	Nightshade family (Solanaceae)
Genre :	Melananthus
Scientific name
	Melananthus
	Walp.

Melananthus is a genus of plants fromthe nightshade family (Solanaceae). The five or six species occur in Central and South America , as well as on Cuba .

description

Vegetative characteristics

The types of Melananthus are either small-growing herbaceous plants with heights of 10 to 40 cm or small, branched shrubs with a height of 0.5 to 1 m. The hair consists exclusively of glandular trichomes . The stem consists of three to six cells, the head can be single-cell or multicellular, in which case the cells can be arranged in a single row or in different levels. The bark of the shoot axes forms a starch sheath, in which, however, no Casparian stripes appear.

The leaves are almost or completely sessile, they are in some of the species in clusters. The shape of the leaf blade is linear, narrow elliptical or linear-lanceolate; the leaf margin is sometimes rolled up. The length ranges from 5 to 25 (rarely only 3) mm, the width from 1.5 to 2 (rarely only 0.4) mm.

Inflorescences and flowers

The inflorescences are terminal spikes , which are composed of groups of two to four flowers . The flower stalks are 1.5 to 2.5 mm long. The calyx is zygomorphic , 1.5 to 2.5 mm long and has five unevenly shaped, triangular elongated or linear segments. The crown can be zygomorphic or radial symmetry. Depending on the species, it is 2.5 to 4 or 4.5 to 8 mm long, its color is yellow-blackish, green, purple or yellow-orange. Their shape is tubular, the corolla tube is very narrow and cylindrical and can be straight or slightly curved. The structure of the coronet is very similar to that of the genus Schwenckia : it is divided into five lobes, with each corolla lobe in turn being divided into three lobes or three-slit and the middle lobe standing in the center, the two outer lobes each connected to the next corolla lobe. The bud coverage is valvat-induplicate.

The four stamens occur in two different lengths, they do not protrude beyond the crown. The starting point in the corolla tube can be the same for all stamens and then lie in the lower quarter of the corolla tube or be located at two levels slightly above one another. In the latter case, the pair above is provided with shorter stamens 1 to 2.5 mm long and set a little deeper, while the second pair has 1.5 to 3 mm long stamens and 0.25 to 0.8 mm long anthers. The counters of the dust bags are usually slightly different in size and they are only separated from each other by less than a quarter of the length in the lower area. The pollen grains are very small with a diameter of 12 to 14 µm, the pollen grain wall is very finely reticulated and about 1.4 µm thick. The ovary is single-chambered, possibly even single-compartment, and forms a single, anatrophic ovule near the base of the ovary . The small scar is disc-shaped and head-shaped.

Fruits and seeds

The fruits are zygomorphic capsules that are 2 to 6 mm long and can be slightly wrinkled or smooth. They are ovate-beaked or somewhat sickle-shaped, somewhat blunted towards the front and open with crevices in the septum. Each fruit only contains a single seed . This is elongated, 1 to 1.5 mm long, broad and rounded at the base, the tip is comparatively narrow. The seed surface is smooth, the hilum points away from the radicle. The embryo is straight or slightly curved, the cotyledons are about half as long as the rest of the embryo. Endosperm is only sparse.

Occurrence

The species of the genus occur mainly in Brazil , Guatemala and Cuba , but can also be found in southern Mexico , Belize , Venezuela and Argentina .

Systematics

External system

Due to the small size of the reproductive organs, a reliable assignment of the genus could not be made for a long time; it was first assigned to the Verbenaceae before it was recognized that it belonged to the nightshade family. Within the systematics of the nightshade family , the genus is classified together with the genera Schwenckia and Heteranthia in the tribe Schwenckieae. The genus Protoschwenckia , which was also placed there in Armando Hunziker's morphologically based system , is now counted among the Cestroideae on the basis of molecular biological studies.

Internal system

There are five or six species within the genus:

The type species is Melananthus dipyrenoides .

proof

literature

Armando T. Hunziker: The Genera of Solanaceae. ARG Gantner Verlag, Ruggell, Liechtenstein 2001, ISBN 3-904144-77-4 .

Individual evidence

^ ^A ^b Richard G. Olmstead, Lynn Bohs: A Summary of Molecular Systematic Research in Solanaceae: 1982-2006. In: DM Spooner et al. (Ed.): Solanaceae VI: Genomics Meets Biodiversity. (= ISHS Acta Horticulturae. 745) 2007, ISBN 978-90-6605-427-1 .
^ ^A ^b Armando T. Hunziker: The Genera of Solanaceae. ARG Gantner Verlag, Ruggell, Liechtenstein 2001.

[Olmstead07-1] A ^b Richard G. Olmstead, Lynn Bohs: A Summary of Molecular Systematic Research in Solanaceae: 1982-2006. In: DM Spooner et al. (Ed.): Solanaceae VI: Genomics Meets Biodiversity. (= ISHS Acta Horticulturae. 745) 2007, ISBN 978-90-6605-427-1 .

[Hunziker01-2] A ^b Armando T. Hunziker: The Genera of Solanaceae. ARG Gantner Verlag, Ruggell, Liechtenstein 2001.