Atriplex

Atriplex () is a plant genus of 250–300 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 

The species 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 alternate or rarely opposite leaves are petiolate or sessile, often persistent or tardily deciduous. The flat or slightly fleshy leaf blades are either entire, or serrate, or lobed and very variable in shape.

The inflorescences consist of axillary or terminal spikes or spicate panicles, or axillary clusters of glomeruled flowers. The flowers are unisexual, some species are monoecious, others dioecious. Male flowers consist of 3-5 perianth lobes and 3-5 stamens. Female flowers are usually lacking a perianth, but are enclosed by 2 foliaceous bracteoles, and contain an ovary with a short style and 2 stigmas.

In fruit, the bracteoles can enlarge, thicken or become appendaged. They enclose the fruit tightly, without becoming connate to it. The pericarp is adnate to the vertically orientated, flattened seed. The seed coat is thick, leathery or hardening. The annular embryo surrounds the perisperm.

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 (kranz anatomy).

Distribution and evolution 
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.

The genus evolved in Middle Miocene, the C4-photosynthesis pathway developed about 14.1-10.9 million years ago, when the climate became increasingly dry. The genus diversified rapidly and spread over the continents. The C4Atriplex colonized North America probably from Eurasia during the Middle/Late Miocene, about 9.8-8.8 million years ago, and later spread to South America. Australia was colonized twice by two C4 lineages, one from Eurasia or America about 9.8-7.8 million years ago, and one from Central Asia about 6.3-4.8 million years ago. The last lineage diversified rapidly, and became the ancestor of most Australian Atriplex species.

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.

Use by humans 
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.

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.

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).

Systematics 
The genus Atriplex was first described in 1753 by Carl Linnaeus. 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. After phylogenetical research, Kadereit et al. (2010) excluded Halimione as a distinct sister genus. The remaining Atripex species were grouped into several clades, that mostly are not identical with the traditional sections:

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 crassifolia Ledeb.: in Asia.
 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.

Selected species not yet investigated phylogenetically:

 Atriplex acadiensis – Maritime saltbush
 Atriplex acutiloba
 Atriplex alaskensis S. Watson – Alaska orache
 Atriplex amnicola Paul G. Wilson – River saltbush, swamp saltbush: in Australia, naturalized in California 
 Atriplex × aptera
 Atriplex argentea – Silvery saltbush
 Atriplex asterocarpa
 Atriplex barclayana
 Atriplex bonnevillensis
 Atriplex bunburyana F.Muell.
 Atriplex cephalantha
 Atriplex cordifolia
 Atriplex cordulata
 Atriplex cornigera
 Atriplex coronata S. Watson: in California
 Atriplex corrugata
 Atriplex coulteri
 Atriplex crassipes
 Atriplex cristata
 Atriplex cryptocarpa
 Atriplex cuneata
 Atriplex depressa
 Atriplex dioica – Thick-leaved orache, saline saltbush
 Atriplex drymarioides
 Atriplex eichleri
 Atriplex elegans
 Atriplex erecticaulis
 Atriplex exilifolia F.Muell.
 Atriplex falcata – Sickle saltbush
 Atriplex flabelliformis
 Atriplex franktonii – Frankton's saltbush
 Atriplex fruticulosa
 Atriplex garrettii
 Atriplex graciliflora
 Atriplex griffithsii – Griffith's saltbush (sometimes included in A. lentiformis or A. torreyi)
 Atriplex hastata – Halberd-leaved orache, Spearscale (often included in A. patula)
 Atriplex heterosperma Bunge – Two-scaled orache: in Eastern Europe
 Atriplex humifusa
 Atriplex humilis F.Muell.
 Atriplex hypoleuca
 Atriplex incrassata F.Muell.

 Atriplex infrequens
 Atriplex johnsonii
 Atriplex johnstonii
 Atriplex klebergorum
 Atriplex kochiana Maiden
 Atriplex limbata
 Atriplex lobativalvis F.Muell.
 Atriplex macropterocarpa
 Atriplex matamorensis
 Atriplex maximowicziana – Maximowicz's saltbush
 Atriplex minuscula
 Atriplex minuticarpa
 Atriplex morrisii
 Atriplex nana
 Atriplex navajoensis
 Atriplex nuttallii S. Watson – Nuttall's saltbush: in North America
 Atriplex obconica
 Atriplex pachypoda
 Atriplex pacifica
 Atriplex paludosa R.Br.
 Atriplex papillata
 Atriplex persistens
 Atriplex plebeja
 Atriplex pumilio R.Br.
 Atriplex pusilla
 Atriplex quadrivalvata
 Atriplex saccaria
 Atriplex spinifera
 Atriplex spinulosa
 Atriplex subspicata
 Atriplex subtilis
 Atriplex tenuissima
 Atriplex texana
 Atriplex torreyi
 Atriplex tridentata
 Atriplex truncata – Wedge-leaved saltbush
 Atriplex tularensis
 Atriplex valdesii  Flores Olv., Mexico
 Atriplex vallicola
 Atriplex vestita
 Atriplex wardii
 Atriplex watsonii
 Atriplex welshii
 Atriplex wolfii
 Atriplex wrightii

Excluded species:
Extriplex:
 Extriplex californica (Moq.) E.H.Zacharias (Syn. Atriplex californica  Moq.) 
 Extriplex joaquiniana (A.Nelson) E.H.Zacharias (Syn. Atriplex joaquiniana A.Nelson)
 Halimione Aellen:
Halimione pedunculata (L.) Aellen (Syn.: Atriplex pedunculata L.)
 Halimione portulacoides (L.) Aellen (Syn.: Atriplex portulacoides L.)
 Halimione verrucifera (M.Bieb.) Aellen (Syn.: Atriplex verrucifera M.Bieb.)
 Stutzia E.H.Zacharias: 
 Stutzia covillei (Standl.) E. H. Zacharias (Syn. Atriplex covillei (Standl.) J. F. Macbr.) 
 Stutzia dioica (Nutt.) E. H. Zacharias (Syn. Atriplex suckleyi (Torrey) Rydberg, Atriplex ovata (Rydb.) Clem. & E. G. Clem.)

References 
 
 
 

 

 

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

 
Category:Halophytes
Category:Drought-tolerant plants
Category:Garden plants
Category:Amaranthaceae
Category:Taxa named by Carl Linnaeus