Salsola tragus

Salsola tragus, often known by its synonym Kali tragus, is a species of flowering plant in the family Amaranthaceae. It is known by various common names such as prickly Russian thistle, windwitch, or common saltwort. It is widely known simply as tumbleweed because, in many regions of the United States, it is the most common and most conspicuous plant species that produces tumbleweeds. Informally, it may be known as Kali or Salsola: the latter being its restored genus, containing 54 other species, into which the obsolete genus Kali has been subsumed.

Taxonomy

Linnaeus originally described the species as ; it is native to Eurasia, but in the 1870s, it appeared in South Dakota when flaxseed from Russia turned out to be contaminated with seeds. Although it is the best-known of this group of weeds and was once thought to be a single, well-defined species, it is now known to include more than one species and some hybrids. This has led to taxonomic confusion in dealing with species in the genera and in America. Recent studies show that the population once assigned to comprises three or more morphologically similar species that differ in flower size and shape. The group was widely assigned to the family Chenopodiaceae, but the Chenopodiaceae – including the genera and – have since been included in the Amaranthaceae. They now are allocated to the Salsoloideae, a subfamily of the Amaranthaceae. ==Description==

Description

s in its axil is an annual forb. In habit, the young plant is erect, but it grows into a rounded clump of branched, tangled stems, each one up to about a metre long. Depending on the plant's genetics and condition, the leaves and stems may be green, red, or striped, and they may be hairless or pubescent. The leaves are tipped with spines that in most varieties are so sharp that the plants are best handled with gloves and other suitably protective clothing, though some genetic variants have only a hair at the tip. On the young plant, leaves may be more than 5 cm long, succulent and more or less cylindrical; these juvenile leaves are deciduous and drop off as the plant matures. The leaves of the mature plant are persistent, leathery, broader and shorter than the young leaves (seldom more than 1 cm in length), rigid and spine-tipped. They remain on the stem till the plant dies at the end of the season. In the axil of the mature leaf, there are two leaf-like bracts with a flower between them. The flower lacks petals but is surrounded by a disk of wide, winged sepals, whitish to pink. ==Ecology==

Ecology

Reproduction and dispersal , Germany (November 2015). The plant becomes woody as the fruits develop. As they ripen, the plant begins to die, dry out, and become brittle. In that state, the base of the stem breaks off easily, particularly in high winds. The plant then rolls readily before the wind and disperses its seeds as a tumbleweed. A large specimen of may produce some 200,000 seeds. Invasive potential has proven to be highly invasive as an introduced species and rapidly became a common ruderal weed of disturbed habitats in many regions of North America, particularly in the Midwest. The species has also become naturalized in various regions of Central and South America and in parts of Southern Africa and Australia. It now occupies a wide variety of habitat types in those regions. It often is the first or even the only colonizer in conditions where no local species can compete successfully. Because it prefers sand and its tolerance of salinity, it commonly grows along sea beaches as well as in disturbed grassland and desert communities, especially in semiarid regions. ==Edibility==

Edibility

The plant is edible when young, and its shoots can be harvested and eaten. As the plant matures, it becomes too woody, bitter, and spiny to be considered edible. The young shoots can be eaten raw in salads, and are reported to be even more flavorful when cooked as a pot herb. Young plants are also reported as good fodder for livestock. Some varieties of Russian thistle can contain above-average levels of oxalic acid, particularly in older plants, and people who are sensitive to oxalic acid should avoid the genus, as it is a severe allergen for some. Oxalates in certain vegetables contribute to gout and are a causative agent in certain types of kidney and bladder stones; therefore, K. tragus is not recommended for people with a history of such conditions or with diabetic kidney disease. People who have adverse reactions to eating spinach, which also can have high levels of oxalates, should avoid consumption of Russian thistle. ==Ecology and agricultural management==

Ecology and agricultural management

is a ruderal annual forb. It germinates rapidly even with very little moisture in arid conditions. When young, it may be grazed freely, but that phase lasts for only a brief period, and generally at a time when other forage is relatively plentiful. After this, it becomes a weed in most contexts. One reason is that as they mature, most varieties become too spiny and woody for most stock to browse. Moreover, older foliage develops higher levels of oxalates, bitter tannins, and alkaloids, making it unpalatable. As its fruits mature, the plant dies, dries, and becomes hard and brittle. In this state, it is likely to detach from its root and become a tumbleweed. As tumbleweeds go, it is very large, often a metre or more in diameter, spiny, largely inedible to most livestock if unprocessed, and a fire hazard. However, in regions where there is plentiful winter rain, the moisture softens both the twigs and the spines, after which hardy breeds of livestock and some wildlife species once again will eat it. Although has not yet received much recognition in contemporary first-world livestock nutrition, this might reflect short memories rather than a lack of evidence for its merits; during the Dust Bowl era, it was credited with rescuing beef cattle husbandry in North America. The usual hay crops had failed, and when all other sources failed, farmers fed their cattle on tumbleweed. restoration in Idaho. After a wildfire, only grew in the arid, saline clay soil, providing minimal forage for livestock and wildlife. Another factor to bear in mind in dealing with is grazing or, more particularly, overgrazing. In regions where competitive vegetation is present together with the , overgrazing may favour the weed, while managing the grazing intensity to favour the desired plants may be the most economical, and in the long term, the most effective way of dealing with its overgrowth. A good example was in controlling troublesome on Bighorn Sheep Winter Ranges in Jasper National Park by proper management of grazing intensity. Salsola and phytoremediation A special class of soil mitigation is phytoremediation, in which the removal and accumulation of toxic elements from soils by suitable management of plant growth is a major component. Because such soil situations as mine dumps tend to be extreme examples of disturbed sites, and often are of fine texture, species show promise for certain classes of such work. Simply by growing there in high density, they can play a valuable role in phytostabilization by reducing wind erosion and similar processes that promote the spread of pollution. The dry tumbleweed material has also been used as mulch on replanted coal mine spoils in Arizona. and others such as iron and cobalt. proved to be an active absorber of all those ions, plus some others, and it may well be a hyperaccumulator of both copper and cadmium. It certainly accumulated lead and arsenic very actively, and also chromium in the most toxic hexavalent form. It is not yet clear that would be a useful species for commercial phytoextraction, either for phytoremediation or for phytomining. Still, there are genetic variables that could, in principle, be selected for. For instance, the ions the plant species absorb are variously bound or chelated by organic acid groups such as oxalate, or by thiol groups, among others. Some, such as arsenate, pass through phosphate metabolic processes before being bound by sulfur groups. However, a plant that has absorbed some of the levels of toxic substances (e.g., arsenic, lead, or cadmium) that the species can accumulate probably would not be suitable for food or fodder. Thus, phytoextraction sites would have to be protected from livestock. ==Prospects for genetic improvement==

Prospects for genetic improvement

Such considerations have led some workers to recommend that the plant be actively exploited for its very attractive merits. Frustratingly, however, the plant in the wild is highly variable; apart from its intrinsic genetic variability, invasive populations have hybridised extensively with other species of that were apparently imported at the same time. To some extent, the genus hybridises in its countries of origin as well. Apart from such sources of variability, there are considerable variations in ploidy. The unpredictability of the merits of wild strains may frustrate farmers who have tried the species and found that seeds from wild plants do not produce crops that meet their expectations, leading them to abandon their attempts. However, despite the associated difficulties, the plants' genetic variability does imply opportunities for genetic improvement. The presence of tetraploids and hexaploids improves the prospects for new variants to be established in the population. The species, along with its hybrids and variants, has attracted attention as a valuable prospect for selective breeding for various agricultural purposes. The most desirable and the most undesirable genetically determined attributes have turned out to assort independently, which is a necessary condition for efficient selection of independent characters, so that, for example, one can select breeding stock with desirable attributes, without being unable to select for the absence of undesirable attributes. One could select, say, lines rich in protein, but without spines. ==Other problems and products==