Alternanthera Micrantha

''Alternanthera'' is a genus of flowering plants in the family Amaranthaceae. It is a widespread genus with most species occurring in the tropical Americas,Sánchez-Del Pino, I., et al. (2012)
Molecular phylogenetics of ''Alternanthera'' (Gomphrenoideae, Amaranthaceae): resolving a complex taxonomic history caused by different interpretations of morphological characters in a lineage with C₄ and C₃–C₄ intermediate species.
''Botanical Journal of the Linnean Society'' 169(3), 493-517.''Alternanthera''.
Flora of North America. and others in Asia, Africa, and Australia. Plants of the genus may be known generally as joyweeds, or Joseph's coat.''Alternanthera''.
Integrated Taxonomic Information System (ITIS). Several species are notorious noxious weeds.Tanveer, A., et al. (2013)
A review on genus ''Alternanthera'' weeds implications.
''Pak. J. Weed Sci. Res'' 19(1), 53-58.

Description

These are annual or perennial herbs or subshrubs. While some of the better-known species are aquatic plants, most are terrestrial. They take many forms, from prostrate to erect to floating. The leaves are oppositely arranged. The inflorescence is a spike or a rounded head occurring in the leaf axils or the ends of branches. The flowers have 5 tepals. There are 3 to 5 stamens which are fused into a rim at the bases, and 5 pseudostaminodes, appendages between the stamens that are not true staminodes. The fruit is a utricle containing one seed.

The genus ''Alternanthera'' contains both terrestrial and aquatic species. The photosynthetic pathway varies in this genus: Some species undergo C₃ carbon fixation, one clade of 17 species has acquired the C₄ pathway, and yet other species have an intermediate C₃-C₄ pathway. Chinthapalli, B., et al. (2001)
Phospho''enol''pyruvate carboxylase purified from leaves of C₃, C₄, and C₃-C₄ intermediate species of ''Alternanthera'': Properties at limiting and saturating bicarbonate.
''Photosynthetica'' 38(3), 415-19.

Species

It is not yet clear how many species belong in the genus. Estimates range between 80 and 200.''Alternanthera''.
The Plant List.

Species include:GRIN Species Records of ''Alternanthera''.
Germplasm Resources Information Network (GRIN).
*'' Alternanthera acaulis'' Andersson
*''Alternanthera adscendens'' Suess.
*''Alternanthera albotomentosa'' Suess.
*''Alternanthera albida'' (Moq.) Griseb
*''Alternanthera albosquarrosa'' Suess.
*''Alternanthera albotomentosa'' Suess.
*''Alternanthera altacruzensis'' Suess.
*'' Alternanthera angustifolia'' R.Br. – narrow-leaf joyweed
*''Alternanthera aquatica'' (Parodi) Chodat
*''Alternanthera arequipensis'' Suess.
*'' Alternanthera areschougii''
*'' Alternanthera asterotricha'' Uline
*'' Alternanthera axillaris'' (Willd.) DC.
*''Alternanthera bettzickiana'' – calico-plant
*''Alternanthera brasiliana'' (L.) Kuntze – Brazilian joyweed, ruby leaf
*'' Alternanthera caracasana'' Kunth – mat chaff-flower, washerwoman
*'' Alternanthera corymbiformis''
*''Alternanthera crucis'' Bold. – West Indian joyweed
*''Alternanthera dentata'' – little ruby
*'' Alternanthera denticulata'' – lesser joyweed
*'' Alternanthera echinocephala'' (Hook.f.) Christoph. – spiny-headed chaff flower,, p. 144 sea-urchin joyweed
*''Alternanthera ficoidea'' – parrot leaf, sanguinarea
*''Alternanthera filifolia'' (Hook.f.) J.T. Howell
*'' Alternanthera flavescens'' – yellow joyweed
*''Alternanthera flavicoma''
*'' Alternanthera galapagensis''
*'' Alternanthera grandis''
*''Alternanthera hassleriana'' Chodat – Hassler's alternanthera
*'' Alternanthera helleri'' (B.L.Rob.) J.T.Howell
*''Alternanthera littoralis'' P.Beauv.
*'' Alternanthera maritima'' (Mart.) A.St.-Hil. – seaside joyweed
*'' Alternanthera mexicana''
*'' Alternanthera nahui''
*''Alternanthera nana'' – downy joyweed, hairy joyweed
*'' Alternanthera nesiotes''
*'' Alternanthera nodiflora'' – common joyweed
*'' Alternanthera olivacea''
*''Alternanthera paronichyoides'' A.St.-Hil. – smooth joyweed
*''Alternanthera philoxeroides'' (Mart.) Griseb. – alligator weed
*''Alternanthera pubiflora''
*'' Alternanthera pungens''
*''Alternanthera reineckii'' Briq.
*'' Alternanthera sessilis'' (L.) DC. – rabbit-meat, sessile joyweed
*'' Alternanthera snodgrassii''
*'' Alternanthera subscaposa''
*'' Alternanthera tenella'' Colla
*''Alternanthera versicolor'' R.Br.

Ecology

Many species have been reported as noxious weeds, including ''A. angustifolia'', ''A. caracasana'', ''A. denticulata'', ''A. nana'', ''A. nodiflora'', ''A. paronychioides'', ''A. philoxeroides'', ''A. sessilis'', ''A. tenella'', and ''A. triandra''. The most important species is alligator weed (''A. philoxeroides''), a South American aquatic plant that has spread to other continents. It is a weed of many kinds of agricultural crops, it is an invasive species that degrades native habitat, and its dense mats of vegetation clog waterways, slowing shipping and increasing flooding. ''Alternanthera'' plants are known to produce allelopathic compounds that injure other plants, including crops.

Biological pest control agents now in use to reduce alligator weed infestations include the alligator weed flea beetle (''Agasicles hygrophila''), the alligator weed thrips (''Amynothrips andersoni''), and the alligator weed stem borer (''Arcola malloi'').

Uses

''A. philoxeroides'' and ''A. sessilis'' are eaten as vegetables in parts of Asia.

Some ''Alternanthera'' are used as ornamental plants.

References

{{Taxonbar, from=Q2840398

Amaranthaceae genera