Atriplex (/ˈætrɪplɛks/[2]) is a plantgenus of about 250 species, known by the common names ofsaltbush andorache (/ˈɒrɪtʃ,-ətʃ/;[3][4] also spelledorach). It belongs to thesubfamilyChenopodioideae of thefamilyAmaranthaceaes.l.. The genus is quite variable and widely distributed. It includes manydesert andseashore plants andhalophytes, as well as plants of moist environments. The generic name originated inLatin and was applied byPliny the Elder to the edible oraches.[5] The name saltbush derives from the fact that the plants retain salt in their leaves; they are able to grow in areas affected bysoil salination.
Species of plants in genusAtriplex areannual orperennial 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 elongatetrichomes. The leaves are arranged alternately along the branches, rarely in opposite pairs, eithersessile or on apetiole, and are sometimes deciduous. The leaf blade is variably shaped and may be entire, tooth or lobed.[6][7][8][9][10]
The flowers are borne in leaf axils or on the ends of branches, in spikes or spike-likepanicles . The flowers areunisexual, some speciesmonoecious, othersdioecious. Male flowers have three to fiveperianth lobes and three to fivestamens. Female flowers are usually lacking a perianth, but are enclosed by two leaf-likebracteoles, have a shortstyle and twostigmas.[6][7][8][9][10]
After flowering, the bracteoles sometimes enlarge, thicken or become appendaged, enclosing the fruit but without adhering to it.[6][7][8][9][10]
Thechromosome base number is x = 9, except forAtriplex lanfrancoi, which is x=10.[11]
A fewAtriplex species areC3-plants, but most species areC4-plants, with a characteristic leaf anatomy, known as kranz anatomy.[11]
The genus evolved in MiddleMiocene, theC4-photosynthesis pathway developed about 14.1–10.9million years ago (mya), 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 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 AustralianAtriplex species.[11]
The type species (lectotype) isAtriplex hortensis.[15] The name is derived fromAncient Greek ἀτράφαξυς (atraphaxys), "orach", itself aPre-Greek substrate loanword.Atriplex is an extremely species-rich genus and comprises about 250[7]-300[11] species, with new species still being discovered. An example includesAtriplex yeelirrie, formally described in 2015.[16]
Traditionaltaxonomy ofAtripliceae based on morphological features has been controversial.[17] Molecular studies have found that many genera are not trueclades. One such study found that Atripliceae could be divided into two main clades,Archiatriplex, with a few, scattered species, and the largerAtriplex clade, which is highly diverse and found around the world.[17] Afterphylogenetic research, Kadereit et al. (2010) excludedHalimione as a distinct sister genus. The remainingAtriplex species were grouped into several clades.[11]
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 genusAtriplex are presented in the cladogram (based on page 7 of[18]). This work suggested that the Americas were colonised by C4Atriplex from Eurasia or Australia. Furthermore, that in the AmericasAtriplex first appeared in South America, where two lineages underwentin situ diversification and evolved sympatrically. North America was then colonised byAtriplex from South America, then one lineage later moved back to South America.[18]
Cladogram of estimated divergences within the genusAtriplex
Background colour in cladogram represents the region where a species is endemic.
South America
North America
Australia
Eurasia
Brignone et al. (2019) hypothesis for the evolution and movement ofAtriplex species globally.[18]
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 thephylogenetical relationships and was rejected by Kadereit et al. (2010).[11]
Atriplex species are used as food plants by thelarvae of someLepidoptera species; see the list of Lepidoptera which feed onAtriplex.[20] They are also sometimes consumed by camels.[21] Forspiders such asPhidippus californicus and otherarthropods, saltbush plants offer opportunities to hide and hunt inhabitat that is otherwise often quite barren.[citation needed] It has been proposed that genusAtriplex was a main food source in the diet of the extinct giant kangarooProcoptodon goliah.[22]
The favored species for human consumption is now usuallygarden orache (A. hortensis),[23][24][25] but many species are edible and the use ofAtriplex as food is known since at least the lateEpipaleolithic (Mesolithic).
Studies onAtriplex species demonstrated their potential use in agriculture. Meat from sheep which have grazed on saltbush has surprisingly high levels ofvitamin E, is leaner and more hydrated than regularlamb and has consumer appeal equal to grain-fed lamb.[28] 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.[29][28]
A study onA. 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.[30] A subsequent study allowed sheep and goats to voluntarily feed onAtriplex 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.[31] In this study they determined when goats and sheep are given as muchA. halimus as they like, they do obtain enough nutrients to supplement their diet – unless the animal requirements are higher during pregnancy and milk production.
^abcStanley 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,ISBN0-19-517389-9.
^abcdGelin 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,ISBN1-930723-27-X.
^abcWalsh, Neville G."Atriples". Royal Botanic Gardens Victoria. Retrieved16 July 2022.
^abcJacobs, Surrey W.L."Atriplex". Royal Botanic Garden Sydney. Retrieved16 July 2022.
^abcdefgGudrun 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.
^Linnaeus, Carl (1753).Species Plantarum. Vol. 2. pp. 1052–1053. Retrieved19 June 2022.
^Carl Linnaeus (1753),"Atriplex",Species Plantarum, vol. 2, Lars Salvius/Biodiversity Heritage Library, pp. 1052–1054, retrieved19 May 2015
^Sharr, Francis Aubi; George, Alex (2019).Western Australian Plant Names and Their Meanings (3rd ed.). Kardinya, WA: Four Gables Press. p. 61.ISBN9780958034180.
^abcBrignone, Nicolás F.; Pozner, Raúl E.; Denham, Silvia S. (October 2019). "Origin and evolution of Atriplex (Amaranthaceae s.l.) in the Americas: Unexpected insights from South American species".Taxon.68 (5): 1027.doi:10.1002/tax.12133.S2CID214371753.
^Tasmanian name, also transcribedtrucanini, trucaninny, trugannini, trugernanna, etc. The plant was the namesake forTruganini, among the last ofher people.
^abPearce, Kelly & Jacob, Robin (2004): Saltbush lifts sheep meat vitamin content.Farming Ahead153(October): 63.PDF fulltextArchived July 23, 2005, at theWayback Machine
^Norman, Hayley C.; Freind, Colby; Masters, David G.; Rintoul, Allan J.; Dynes, Robyn A. & Williams, Ian H. (2004): Variation within and between two saltbush species in plant composition and subsequent selection by sheep.Aust. J. Agr. Res.55(9): 999–1007.doi:10.1071/AR04031 (HTML abstract)
^Wilson, A.D.; Harrington, G.N. (1980). "Nutritive value of Australian browse plants".International Livestock Centre for Africa. Addis Ababa: 291.
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