Atriplex

''Atriplex'' () is a plant genus of about 250 species, known by the common names of saltbush and orache (; also spelled orach). It belongs to the subfamily Chenopodioideae of the family Amaranthaceae ''s.l.''.
The genus is quite variable and widely distributed. It includes many desert and seashore plants and halophytes, as well as plants of moist environments.
The generic name originated in Latin and was applied by Pliny the Elder to the edible oraches. The name saltbush derives from the fact that the plants retain salt in their leaves; they are able to grow in areas affected by soil salination.

Description

Species of plants in genus ''Atriplex'' are annual or perennial herbs, subshrubs, or shrubs. The plants are often covered with bladderlike hairs, that later collapse and form a silvery, scurfy or mealy surface, rarely with elongate trichomes. The leaves are arranged alternately along the branches, rarely in opposite pairs, either sessile or on a petiole, and are sometimes deciduous. The leaf blade is variably shaped and may be entire, tooth or lobed.

The flowers are borne in leaf axils or on the ends of branches, in spikes or spike-like panicles . The flowers are unisexual, some species monoecious, others dioecious. Male flowers have 3-5 perianth lobes and 3-5 stamens. Female flowers are usually lacking a perianth, but are enclosed by 2 leaf-like bracteoles, have a short style and 2 stigmas.

After flowering, the bracteoles sometimes enlarge, thicken or become appendaged, enclosing the fruit but without adhering to it.

The chromosome base number is x = 9, except for ''Atriplex lanfrancoi'', which is x=10.

A few ''Atriplex'' species are C₃-plants, but most species are C₄-plants, with a characteristic leaf anatomy, known as kranz anatomy.

Atriplex elegans.jpg, ''Atriplex elegans''
Atriplex hymenelytra bracts.jpg, ''Atriplex hymenelytra''
Starr 050516-1394 Atriplex lentiformis.jpg, ''Atriplex lentiformis''
Atriplex nummularia.JPG, ''Atriplex nummularia''
Starr 040125-0020 Chenopodium murale.jpg, ''Atriplex suberecta''
Atriplex patula (5129939806).jpg, '' Atriplex patula'', female flower with bracteoles and ovule

Taxonomy

The genus ''Atriplex'' was first formally described in 1753 by Carl Linnaeus in '' Species Plantarum''. The genus name was used by Pliny for orach, or mountain spinach ('' A. hortensis'').

Phylogeny

The genus evolved in Middle Miocene, the C₄-photosynthesis pathway developed about 14.1–10.9 million years ago (mya), when the climate became increasingly dry. The genus diversified rapidly and spread over the continents. The C₄ ''Atriplex'' colonized North America probably from Eurasia during the Middle/Late Miocene, about 9.8–8.8 mya, and later spread to South America. Australia was colonized twice by two C₄ lineages, one from Eurasia or America about 9.8–7.8 mya, and one from Central Asia about 6.3–4.8 mya. The last lineage diversified rapidly, and became the ancestor of most Australian ''Atriplex'' species.

Systematics

The type species ( lectotype) is ''Atriplex hortensis''. The name is derived from Ancient Greek ἀτράφαξυς (''atraphaxys''), "orach", itself a Pre-Greek substrate loanword.

''Atriplex'' is an extremely species-rich genus and comprises about 250-300 species, with new species still being discovered. An example includes ''Atriplex yeelirrie'', formally described in 2015.

Traditional taxonomy of Atripliceae based on morphological features has been controversial. Molecular studies have found that many genera are not true clades. One such study found that Atripliceae could be divided into two main clades, ''Archiatriplex'', with a few, scattered species, and the larger ''Atriplex'' clade, which is highly diverse and found around the world. After phylogenetic research, Kadereit et al. (2010) excluded ''Halimione'' as a distinct sister genus. The remaining ''Atriplex'' species were grouped into several clades.

The following is a cladogram with estimated divergence times for the tribe Atripliceae. To infer the phylogeny, an ITS matrix composed of spacer ITS-1, the 5.8S subunit, and spacer ITS-2 were amplified and sequenced for each specimen. Not all species in the genus ''Atriplex'' are presented in the cladogram (based on page 7 of ). This work suggested that the Americas were colonised by C4 ''Atriplex'' from Eurasia or Australia. Furthermore, that in the Americas ''Atriplex'' first appeared in South America, where two lineages underwent ''in situ'' diversification and evolved sympatrically. North America was then colonised by ''Atriplex'' from South America, then one lineage later moved back to South America.

*''Atriplex lanfrancoi/cana''-Clade:
**''Atriplex lanfrancoi'' (Brullo & Pavone) G. Kadereit et Sukhor. (Syn.: ''Cremnophyton lanfrancoi'' Brullo & Pavone): endemic to Malta and Gozo.
**''Atriplex cana'' C.A. Mey.: from Eastern European Russia to western China.
*''Atriplex'' section ''Atriplex'': annual C₃-plants.
**''Atriplex aucheri'' Moq.: in Eastern Europe and West Asia.
** ''Atriplex hortensis'' L. – Garden orache, red orach, mountain spinach, French spinach: in Asia, cultivated or naturalized in Europe.
** ''Atriplex oblongifolia'' Waldst. & Kit. – Oblong-leaved orache: in Eurasia.
** ''Atriplex sagittata'' Borkh. (Syn.: ''Atriplex nitens'' Schkuhr): in Eurasia
*''Atriplex'' section ''Teutliopsis'' Dumort.: annual C₃-plants.
**''Atriplex australasica'' Moq.
** ''Atriplex calotheca'' (Rafn) Fr.: in Northern Europe.
** ''Atriplex davisii'' Aellen: from southern Europe to Egypt.
** ''Atriplex glabriuscula'' Edmondston – Northeastern saltbush, Babington's orache, smooth orache, Scotland orache, glabrous orache: In central and northern Europe.
** ''Atriplex gmelinii'' C.A. Mey. ex Bong. – Gmelin's saltbush: in Asia and North America.
** ''Atriplex intracontinentalis'' Sukhor.: from Central Europe to Asia.
** ''Atriplex laevis'' C.A. Mey.: in Asia, naturalized in eastern Europe.
** ''Atriplex latifolia'' Wahlenb.: in Eurasia.
** ''Atriplex littoralis'' L. – Grass-leaved orache: in Eurasia and North Africa.
** ''Atriplex longipes'' Drejer – Long-stalked orache: in northern Europe.
** ''Atriplex micrantha'' C.A. Mey.: in Asia, naturalized in Europe.
** ''Atriplex nudicaulis'' Boguslaw – Baltic saltbush: in Eurasia.
** '' Atriplex patula'' L. – Common orache, spreading orache: in Eurasia and North Africa.
** ''Atriplex praecox'' Hülph. – Early orache: in northern Europe.
** ''Atriplex prostrata'' Moq. – Spear-leaved orache, thin-leaved orache, triangle orache, fat hen: in Eurasia and North Africa.
* C₄-''Atriplex''-Clade: containing the majority of species. The traditional classification into sections (sect. ''Obione'', sect. ''Pterochiton'', sect. ''Psammophila'', sect. ''Sclerocalymma'', sect. ''Stylosa'') did not reflect the phylogenetical relationships and was rejected by Kadereit et al. (2010).
**''Atriplex acanthocarpa'' (Torr.) S. Watson: in North America.
** ''Atriplex acutibractea'' Anderson: in Australia.
** ''Atriplex altaica'' Sukhor.: in Asia.
** ''Atriplex angulata'' Benth.: in Australia.
** ''Atriplex billardierei'' (Moq.) Hook. f.: in Australia.
** ''Atriplex canescens'' (Pursh) Nutt. – Chamiso, chamiza, four-winged saltbush, grey sagebrush: in North America.
** ''Atriplex centralasiatica'' Iljin: in Asia.
** '' Atriplex cinerea'' Poir. – Grey saltbush, truganini: in Australia
** ''Atriplex codonocarpa'' P.G. Wilson: in Australia.
** ''Atriplex conduplicata'' F. Muell.: in Australia.
** '' Atriplex confertifolia'' (Torr. & Frém.) S. Watson – Shadscale (saltbush): in North America.
** ''Atriplex cordobensis'' Gand. & Stuck.: in South America.
** ''Atriplex deserticola'' Phil.: in South America.
** ''Atriplex dimorphostegia'' Kar. & Kir.: in North Africa.
** ''Atriplex eardleyae'' Aellen: in Australia
** ''Atriplex elachophylla'' F. Muell.: in Australia.
** '' Atriplex fissivalvis'' F. Muell.: in Australia
** ''Atriplex flabellum'' Bunge ex Boiss.: in Eurasia.
** '' Atriplex gardneri'' (Moq.) D. Dietr. – Gardner's saltbush, moundscale: in North America
** ''Atriplex glauca'' L.: in Portugal, Spain and in North Africa.
** '' Atriplex halimus'' L. – Mediterranean saltbush, sea orache, shrubby orache: in south Europe, North Africa and southwest Asia.
** ''Atriplex herzogii'' Standl.: in North America.
** ''Atriplex holocarpa'' F. Muell.: in Australia.
** ''Atriplex hymenelytra'' (Torr.) S. Watson – Desert holly: in North America.
** ''Atriplex hymenotheca'' Moq.: in Australia.
** ''Atriplex imbricata'' (Moq.) D. Dietr.: in South America.
** ''Atriplex inamoena'' Aellen: in Eurasia.
** ''Atriplex intermedia'' Anderson: in Australia.
** ''Atriplex isatidea'' Moq.: in Australia.
** ''Atriplex laciniata'' L. – Frosted orache: In western and northern Europe.
** ''Atriplex lampa'' (Moq.) Gillies ex Small: in South America.
** ''Atriplex lehmanniana'' Bunge: in Eurasia.
** ''Atriplex lentiformis'' (Torr.) S. Watson – Quail bush: in North America.
** ''Atriplex leptocarpa'' F. Muell.: in Australia.
** ''Atriplex leucoclada'' Boiss.: in Eurasia.
** '' Atriplex leucophylla'' (Moq.) D. Dietr.: in North America
** ''Atriplex lindleyi'' Moq.: in Australia.
** ''Atriplex moneta'' Bunge ex Boiss.: in Eurasia.
** ''Atriplex muelleri'' Benth.: in Australia.
** ''Atriplex nessorhina'' S.W.L. Jacobs: in Australia.
** ''Atriplex nummularia'' Lindl. – Old man saltbush, giant saltbush: in Australia.
** ''Atriplex obovata'' Moq.: in North America.
** ''Atriplex pamirica'' Iljin: in Eurasia.
** '' Atriplex parishii'' S. Watson: in North America
** '' Atriplex parryi'' S. Watson: in North America
** ''Atriplex parvifolia'' Kunth: in South America.
** ''Atriplex patagonica'' (Moq.) D. Dietr.: in South America.
** '' Atriplex phyllostegia'' (Torr. ex S. Watson) S. Watson: in North America.
** ''Atriplex polycarpa'' (Torr.) S. Watson – Allscale (saltbush), desert saltbush, cattle saltbush, cattle spinach: in North America.
** '' Atriplex powellii'' S. Watson – Powell's saltbush: in North America.
** ''Atriplex pseudocampanulata'' Aellen: in Australia.
** ''Atriplex quinii'' F. Muell.: in Australia.
** ''Atriplex recurva'' d'Urv.: in Eurasia, endemic to areas around the Aegean.
** ''Atriplex rhagodioides'' F. Muell.: in Australia.
** ''Atriplex rosea'' L. – Tumbling orache: in Eurasia and North Africa.
** ''Atriplex rusbyi'' Britton ex Rusby: in South America.
** ''Atriplex schugnanica'' Iljin: in Asia.
** ''Atriplex semibaccata'' R. Br. – Australian saltbush, berry saltbush, creeping saltbush: in Australia.
** ''Atriplex semilunaris'' Aellen: in Australia.
** ''Atriplex serenana'' A. Nelson ex Abrams: in North America
** ''Atriplex sibirica'' L.; in Asia, naturalized in Europe.
** ''Atriplex sphaeromorpha'' Iljin: in Russia, Ukraine and Caucasus.
** ''Atriplex spinibractea'' Anderson: in Australia.
** ''Atriplex spongiosa'' F. Muell.: in Australia.
** ''Atriplex stipitata'' Benth.: in Australia.
** ''Atriplex sturtii'' S.W.L. Jacobs: in Australia.
** ''Atriplex suberecta'' I. Verd. – Sprawling saltbush, lagoon saltbush: in Australia.
** '' Atriplex tatarica'' Aellen: in Europe, North Africa and Asia.
** ''Atriplex turbinata'' (Anderson) Aellen: in Australia.
** ''Atriplex undulata'' (Moq.) D. Dietr.: in South America.
** ''Atriplex velutinella'' F. Muell.: in Australia.
** ''Atriplex vesicaria'' Heward ex Benth. – Bladder saltbush: in Australia.

Distribution and habitat

The genus ''Atriplex'' is distributed nearly worldwide from subtropical to temperate and to subarctic regions. Most species-rich are Australia, North America, South America and Eurasia. Many species are halophytes and are adapted to dry environments with salty soils.

Ecology

''Atriplex'' species are used as food plants by the larvae of some Lepidoptera species; see the list of Lepidoptera which feed on ''Atriplex''. For spiders such as ''Phidippus californicus'' and other arthropods, saltbush plants offer opportunities to hide and hunt in habitat that is otherwise often quite barren.

It has been proposed that genus ''Atriplex'' was a main food source in the diet of the extinct giant kangaroo ''Procoptodon goliah''. Stable isotopic data suggested that their diet consisted of plants that used the C4 photosynthetic pathway, and due to their semi-arid distribution, chenopod saltbushes were likely responsible.

Uses

The favored species for human consumption is now usually garden orache (''A. hortensis''), but many species are edible and the use of ''Atriplex'' as food is known since at least the late Epipaleolithic (Mesolithic).

Common orache ('' A. patula'') is attested as an archaeophyte in northern Europe, and the Ertebølle culture is presumed to have used it as a food. Its seed has been found among apparent evidence of cereal preparation and cooking at Late Iron Age villages in Britain. In the biblical Book of Job, ''mallûaḥ'' (מַלּ֣וּחַ, probably Mediterranean saltbush, ''A. halimus'', the major culinary saltbush in the region) is mentioned as food eaten by social outcasts (). Grey saltbush ('' A. cinerea'') has been used as bushfood in Australia since prehistoric times.
Chamiso (''A. canescens'') and shadscale (''A. confertifolia'') were eaten by Native Americans, and spearscale (''A. hastata'') was a food in rural Eurasia.

Studies on ''Atriplex'' species demonstrated their potential use in agriculture. Meat from sheep which have grazed on saltbush has surprisingly high levels of vitamin E, is leaner and more hydrated than regular lamb and has consumer appeal equal to grain-fed lamb. The vitamin E levels could have animal health benefits while extending the shelf-life and maintaining the fresh red colour of saltbush lamb. This effect has been demonstrated for old man saltbush ('' A. nummularia'') and river saltbush ('' A. amnicola''). For reasons unknown, sheep seem to prefer the more fibrous, less nutritious river saltbush.

A study on ''A. nummularia'' discovered the species have a nitrogen content of 2.5–3.5%, and could potentially be used as a protein supplement for grazing if palatable. A subsequent study allowed sheep and goats to voluntarily feed on '' Atriplex halimus'' and aimed to determine if the saltbush was palatable, and if so, did it provide enough nutrients to supplement the diet of these animals. In this study they determined when goats and sheep are given as much '' A. halimus'' as they like, they do obtain enough nutrients to supplement their dietunless the animal requirements are higher during pregnancy and milk production.

Saltbushes are also used as an ornamental plant in landscaping and can be used to prevent soil erosion in coastal areas. Old man saltbush (''Atriplex nummularia'') has also been successfully used to rehabilitate old mining sites around Lightning Ridge (Australia).

See also

*Barbara Hulme, producer of Atriplex hybrids

References

Stanley L. Welsh
''Atriplex'' - online
In: Flora of North America Editorial Committee (ed.): ''Flora of North America North of Mexico'', Volume 4: ''Magnoliophyta: Caryophyllidae, part 1.'', Oxford University Press, New York. 2003, .
Gelin Zhu, Sergei L. Mosyakin & Steven E. Clemants: ''Chenopodiaceae''
''Atriplex'' - online
In: Wu Zhengyi, Peter H. Raven, Deyuan Hong (ed.): ''Flora of China'', Volume 5: ''Ulmaceae through Basellaceae.'', Science Press und Missouri Botanical Garden Press, Beijing und St. Louis, 2003, .



Gudrun Kadereit, Evgeny V. Mavrodiev, Elizabeth H. Zacharias & Alexander P. Sukhorukov: Molecular phylogeny of Atripliceae (Chenopodioideae, Chenopodiaceae): Implications for systematics, biogeography, flower and fruit evolution, and the origin of C4 Photosynthesis. - ''American Journal of Botany'' 97(10): 1664-1687, 2010.
(2004): Variation within and between two saltbush species in plant composition and subsequent selection by sheep. '' Aust. J. Agr. Res.'' 55(9): 999–1007. (HTML abstract)
(2004): Saltbush lifts sheep meat vitamin content. ''Farming Ahead'' 153(October): 63
PDF fulltext


''Atriplex''
at Tropicos, accessed 2013-07-11

* (1999): Orach. ''In: Oxford Companion to Food'': 556.
*

{{Taxonbar, from=Q157801

Halophytes
Drought-tolerant plants
Garden plants
Amaranthaceae genera
Taxa named by Carl Linnaeus
Pseudocereals
Chenopodioideae