Solanum viarum
Solanum viarum
Solanum viarum is a species of the genus of the nightshade (Solanum ). Within the genus it is placed in the subgenus Leptostemonum, which is characterized mainly by the conspicuous spines. Solanum viarum applies in the southeastern U.S. as invasive weeds.
Description
Vegetative characteristics
Solanum viarum is a 0.5 to 2 m tall, upright shrub with a high number of splaying branches. The stems are covered with uniform, simple, glandular trichomes, which have a length of 0.4 to 0.5 mm. The plant is sparse with spines. The longest spines reach a length of 8 mm, are bent back and strongly broadened at the base, while the shorter are often only 1 mm long and rather thin, straight and abspreizend. The base of the spines is covered with short, fine trichomes with glandular tips, and with somewhat longer, pointed trichomes with a length of up to 0.2 mm.
A sympodial unit consists of two true leaves, which are usually arranged in pairs. A sheet is approximately twice as large as the second sheet have a larger surface area of 7 to 10 ( 15 ) x 6 to 8 ( 15) inches, and are usually as long as it is wide. The petioles of larger leaves are 3-6 cm long. The thin leaves are ovate to almost circular, the leaf base is cordate to obtuse. The leaf margin is usually three to five pairs of blunt or pointed lobes, which in turn be entire or also may be lobed. The blade tip is sharpened or dulled. On the achszugewandten page they are hairy with two-to three-cell, translucent, 0.4 to 1 mm long trichomes. The achsabgewandten page is densely covered with simple, glandular, about 0.4 mm long trichomes, but also slightly longer, simple, translucent trichomes come to 0.8 mm in length and stemless four (rarely five ) radiating, stellate trichomes with a diameter of 0.8 to 1 mm and a height of 0.5 to 0.8 mm in front. The petioles are covered with similar trichomes as they are also found on the shoot, in addition, there are also some simple, three-cell, translucent trichomes to 1.2 mm in length. Both leaf pages are only sparsely covered with spines, these vary from straight, needle- sharp spines up to very fine spines, sitting on the thinner leaf veins. The spines on the petioles are acicular with 5 to 18 mm longer than those on the rung.
Inflorescences and flowers
Solanum viarum flowers all year round, but even more so in the period from September to April. The standing outside the leaf axils inflorescences are sessile or nearly sessile, unbranched and consist of three to five flowers. Normally, only the lowest flower, rarely the lowest two flowers is fertile. The axes of the inflorescences are densely pubescent with simple, glandular trichomes with a length of 0.4 to 0.6 mm, and in between are some simple, translucent trichomes, which can be up to 1.2 mm long. Spines are either not present on the inflorescence stems or there are few, up to 2 mm long spines. The order to shoot sinuous and closely applied to the inflorescence axis flowers during the flowering stems are 7-11 mm long, crop maturity, they have increased to 10 to 21 mm. The cross section of flower stalks is turning round, the diameter is 2 mm, towards the tip it is hardly increased.
The flowers have a 3 to 4 mm long, triangular calyx, its tube 2 mm and the pointed lobes are 0.8 to 2 mm long. At the base of it is about 0.6 to 0.8 mm wide. The hair resembles that of the flower stalks, but the number of simple, transparent trichomes is usually somewhat higher. The cup is filled unbestachelt or only a few, up to 2 mm long trichomes. On the fruit the calyx is enlarged, the calyx lobes are 4 to 6.5 mm long and at the base of 3.2 to 4 mm wide. The greenish or whitish crown is very delicate, has a diameter of about 2 cm, is 10 to 13 mm long and star-shaped. The corolla tube is 2-3 mm long, narrowly lanceolate Corolla lobe, tapering 7-10 mm long at the base and 2.5 to 3 mm wide towards the tip. The outside is filled with simple, glandular, up to 0.6 mm long trichomes, the inside is hairless. The stamens consist of a 1 to 1.8 mm long stamens, free, a light yellow to cream available at the, 5.5 to 6.9 mm long and wide at the base 1 to 1.5 mm dust bag that is tapered forward and opens there with small pores. The ovary is densely hairy with simple, pointed trichomes, which are 0.2 to 0.35 mm long, in between are some shorter, glandular hairs. When increasing the size of the ovary, the hair falls off, the ovary reaches a diameter of about 5 mm are no longer trichomes present. The stamp of the fertile flowers is 6.8 to 8.2 mm long, 0.5 mm in diameter, cylindrical and glabrous, the scar is little head -shaped.
Fruit and seeds
The fruits are spherical berries with a diameter of 2.2 to 2.5 cm. Unripe fruits are light green with dark green spots, when ripe they are yellow. Inside, there is an approximately 5 mm thick, whitish or greenish with mesocarp spongy consistency. Per fruit are found between about 190 and 385 light red-brown seeds that are flat kidney-shaped and 2.2 to 2.8 × 2.0 to 2.5 mm in size.
Distribution and habitat
The original range of the species extends from Paraguay on the north-eastern Argentina and Uruguay to large parts of eastern Brazil. There, the plants grow mainly on grazing areas, in streets, on garbage dumps, cultivated areas and on the edge of forests in low lying, mostly below 1000 m. It is now to find the kind in India, Africa, China, Vietnam, Australia, Central America, the West Indies, since the 1980s it is also spreading in the Southeast and ranks up there as a dangerous, invasive weeds.
System
Solanum viarum is placed in an untitled series of the subgenus Leptostemonum, Section Acanthophora. This series is next Solanum viarum from occurring in Mexico and northern Central America and the species Solanum myriacanthum to be found in Brazil, Africa and the Indian subcontinent species Solanum aculeatissiumum. The cladistic relationships of the three species of this monophyletic series have not yet been clarified beyond doubt.
Importance
Solanum viarum applies in many of the areas where the species was introduced as an invasive weed. By spiny leaves and stems the plant for livestock feed plant is not as interesting, so that they grow into dense, impenetrable thickets. The fruit can be eaten by cattle and small mammals, so that thereby a wider distribution in the area is encouraged. Especially in areas of central and southern Texas, the species has large grazing areas covered, so that it no longer suitable as stand area for livestock. Estimates of the so- infested area is around 400,000 to 500,000 hectares for the state of Florida in 1995 or 1996. Often, the procedure is with herbicides, plowing against type, but often with limited success. In 1994, a program to combat the spread of the species was launched in the United States. For this was searched for natural enemies from Brazil, Paraguay and Argentina, with which the propagation can be curbed. 2003, the leaf beetles ( Coleoptera) Gratiana boliviana was introduced for this reason, in Florida, to feed its larvae and adult specimens of the plants. In some cases a decrease in Solanum viarum - populations of up to 90% could be detected already within three years, but the species could not be fully contained. In a survey conducted in 2006 indicated 80 % of the polled cattle farmer Florida that the type was to be found on their pastures, 65 % called it as a serious problem in cattle breeding. Overall, the losses incurred by the cattle farmers in Florida in 2006 by the way were estimated at 15 million U.S. dollars. In addition to the cattle and the cultivation of plants by the propagation of the species is affected because they ( lycopersicum Solanum ) vectors or host plant for pests and diseases of economically important solanaceous plants such as tomato, pepper ( capsicum), eggplant (Solanum melongena ) and tobacco (Nicotiana tabacum may be ).