Arthraxon Hispidus

''Arthraxon hispidus,'' is an annual grass commonly known as small carpetgrass, hairy jointgrass, joint-head grass, jointhead arthraxon, small carp grass, and creek grass. It is native to East Asia and Australia. It was accidentally introduced to the United States, Central America, and South America, where it is considered an invasive species.

Description

''Arthraxon hispidus'' is grass that is characterized by ovate or lanceolate shaped leaves with cordate bases that are 2.5-7.6 cm (1-3 in) long and 0.5-1.27 cm (0.2-0.5 in) wide. Its leaf stems and margins are hairy. It is 0.3-0.6 m (1-2 ft) tall with hairless, upright stems. It can spread by rooting at the nodes on its stem if they touch the ground and can spread easily this way. It fruits in caryopses, similar to other grain-like grasses, which may or may not contain awns depending on the subspecies. Its flowering and fruiting time is September through November. The upper glume is purple while the lower glume is green.

It may be confused for deertongue panicgrass (''Dicanthelium clandestinum'') or for '' Oplismenus aemulus.'' ''Arthraxon hispidus'' is distinguished from ''D. clandestinum'' due to its shorter height and leaves as well as the presence of marginal hairs. ''Arthraxon hispidus'' is distinguished from ''O. aemulus'' by its digitate and subdigitate inflorescence.

Taxonomy

''Arthraxon hispidus'' is highly variable, causing some researchers to consider there to be separate subspecies of the plant while others defend its single-species status. Current subspecies of ''A. hispidus'' are based on awn presence or absence.

Some researchers have justified the recognition of a single species (with no subspecies) by stating that proposed subspecies lack enough defining characteristics or geographical separation to be considered separate. They propose that the natural variation of ''Arthraxon hispidus'' can be explained by environmental differences across the species range.

Distribution and habitat

''Arthraxon hispidus'' grows in moist, sunny environments and can be found in riparian, wetland, or floodplain areas across Asia and Australia, specifically New South Wales and Queensland. The seeds of ''A. hispidus'' can be distributed and carried by water in its habitat.

The germination of ''A. hispidus'' is rapid (about three days) and with few limiting factors. It has proven to have high temperature (8-37 degrees Celsius) and pH (5-10) tolerance in germination. It is not known to germinate well in a wide range of salinity, with drought, or when buried more than 1-2 cm (0.4-0.8 in) deep.

Similar to other Australian fire-adapted plants, fire has been suggested to promote germination. Fire is not a necessary disturbance for ''A. hispidus'' to recruit in Australia, but it is believed that ''A. hispidus'' is resistant to variable weather patterns.

Uses

In Asia, ''Arthraxon hispidus'' has a history of being used in traditional medicines as well as dyes.

In traditional medicine, it has been used to treat inflammatory diseases such as asthma. 7-methoxy-luteolin-8-C-β-6-deoxy-xylo-pyranos-3-uloside (mLU8C-PU) has been isolated from ''A. hispidus'', which may be valuable in the treatment of tumor cells, as with other luteolins.

''Arthraxon hispidus'' has been used in the production of a yellow silk cloth, kihachijo, which is associated with Hachijo Island and its kimonos. Identified dye components of the flavonoid ''C-''glycosides include luteolin 8-''C''-rhamnoside, apigenin 8-''C-''rhamnoside, and tricin are responsible for the yellow color produced.

Invasive status and management

In the United States, ''Arthraxon hispidus'' is considered an invasive weed. It was first discovered in the United States in Virginia in the 1930s and was thought to be introduced accidentally or possibly by immigrants from Asia. It now exists in at least 25 US states and is recognized as an invasive species by many of those states. As an invasive species, it is explicitly forbidden in Connecticut and New York.

Management of ''Arthraxon hispidus'' includes mowing, hand-weeding, or glyphosate-based herbicide application. It is recommended to begin management or control practices of ''A. hispidus'' before it produces seeds, due to its rapid germination.

In Australia, ''Arthraxon hispidus'' is considered a threatened species. There is uncertainty about the natural plant community of the species due to a long history of human development. It grows most successfully with other native New South Wales species and grows well in the region of Australia's northern coast.

References

{{Taxonbar, from=Q5702217

Andropogoneae
Flora of tropical Asia
Flora of temperate Asia
Flora of Africa