# Proatriplex

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{{Short description|Genus of plants}}
{{Speciesbox
|image = Proatriplex pleiantha - Patrick Alexander 01.jpg
|image_caption = ''Proatriplex pleiantha'' Sandoval County, New Mexico, USA 
| status = G3 
| status_system = TNC
| status_ref = <ref name=NS>{{cite web |title=''Proatriplex pleiantha'' {{!}} NatureServe Explorer |url=https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.135662/Proatriplex_pleiantha |website=[NatureServe](/source/NatureServe) Explorer |access-date=2 October 2024}}</ref>
|genus = Proatriplex
|parent_authority = ([W.A.Weber](/source/William_Alfred_Weber)) [Stutz](/source/Howard_Coombs_Stutz) & [G.L.Chu](/source/Ge_Lin_Chu)
|species = pleiantha
|authority = ([W.A.Weber](/source/William_Alfred_Weber)) [Stutz](/source/Howard_Coombs_Stutz) & [G.L.Chu](/source/Ge_Lin_Chu) (1990)
|display_parents = 3
|synonyms =  
*''Atriplex pleiantha'' <small>W.A.Weber (1950)</small>
*''Atriplex'' subg. ''Proatriplex'' <small>W.A.Weber</small>
*''Atriplex'' sect. ''Pleianthae'' <small>S.L.Welsh</small>
|synonyms_ref = <ref name="Zacharias" />
}}

'''''Proatriplex''''' is a [monotypic](/source/monotypic) plant genus in the subfamily [Chenopodioideae](/source/Chenopodioideae) of the family [Amaranthaceae](/source/Amaranthaceae), with the only species '''''Proatriplex pleiantha''''' (syn. ''Atriplex pleiantha'').<ref name="Zacharias" /> It is known by the common names '''four-corners orach'''<ref name="FlNAmerica" /> and '''Mancos shadscale'''.<ref>{{PLANTS|id=PRPL2|taxon=Proatriplex pleiantha|accessdate=14 October 2015}}</ref>  It occurs in the Navajo Basin of Arizona, Colorado, New Mexico, and Utah.

==Description==
thumb|left|''Proatriplex pleiantha'' detail of leaves and flowers
''Proatriplex pleiantha'' is an [annual plant](/source/annual_plant) of 5–17&nbsp;cm, glabrous, sometimes slightly farinose. The erect [stems](/source/Plant_stem) are branched from base with white-yellow or reddish ascending branches. The alternate or sometimes nearly opposite [leaves](/source/leaves) are petiolate. The succulent, bright green leaf blades of 5–28&nbsp;mm length and width are ovate to suborbiculate with entire margins. The leaf anatomy is of the "normal" (''non-Kranz'') type of [C3-plants](/source/C3_carbon_fixation).<ref name="Zacharias" />

The plants are [monoecious](/source/monoecious). The [inflorescence](/source/inflorescence)s either contain mixed male and female flowers, or consist of interrupted, terminal spikes of glomerulated male flowers, and female flowers standing in the leaf axils. Male flowers (without bracteoles) consist of 5 [perianth](/source/perianth) lobes, ca. 1–1.5&nbsp;mm long, united in the lower half, with [cucullate](/source/Glossary_of_leaf_morphology) tips, and 5 exserting [stamens](/source/stamens) inserting on a disc. 
Female flowers are sitting in groups of 2–6 within 2 opposite [bracteole](/source/bracteole)s, they consist of a hyaline perianth of 5 scale-like, lanceolate to ovate [tepal](/source/tepal)s of 1–1.5&nbsp;mm, and an ovary with 2 filiform, slightly exserted [stigmas](/source/Stigma_(botany)).<ref name="Zacharias" />

In fruit, the bracteoles enclosing the fruits become accrescent, 3–7&nbsp;mm long and broad, slightly connate in the lower half. Their shape is  triangular-ovate to orbiculate, with sessile or shortly stipitate bases and entire margins. Their surface is glabrous, without tubercles. The suborbicular to obovoid, laterally compressed fruit (utricle) is nearly equal in length to perianth and falls at maturity. The membranous [pericarp](/source/pericarp) adheres to the seed. The vertically orientated seed has a black, smooth and shining, crustaceous seed coat. The annular embryo surrounds the copious farinaceous perisperm.<ref name="Zacharias" />

''Proatriplex pleiantha'' is flowering from May to June.<ref name="Zacharias" />

The [chromosome](/source/chromosome) numbers are n = 9 (haploid) and 2n = 18 (diploid).<ref name="Zacharias" />

==Systematics==
''Proatriplex'' belongs to the tribe [Atripliceae](/source/Atripliceae) in the subfamily [Chenopodioideae](/source/Chenopodioideae) of the family [Amaranthaceae](/source/Amaranthaceae).<ref name="Zacharias" />

''Proatriplex'' has been first described in 1950 by [William Alfred Weber](/source/William_Alfred_Weber) at the rank of a [subgenus](/source/subgenus) of ''[Atriplex](/source/Atriplex)'' (in: ''Madroño'' 10(6): p.&nbsp;188–189). In 1990, it was raised to genus level by [Howard Coombs Stutz](/source/Howard_Coombs_Stutz) & [Ge Lin Chu](/source/Ge_Lin_Chu) (in: ''American Journal of Botany'' 77(3), p.&nbsp;364). The genus is [monotypic](/source/monotypic), comprising only ''Proatriplex pleiantha'' (W.A. Weber) Stutz & G.L. Chu.. This species was later again included in genus ''[Atriplex](/source/Atriplex)''.<ref name="FlNAmerica" /> [Phylogenetic](/source/Phylogenetic) research revealed it to be distinct from most ''Atriplex'' species, being more closely related to other endemic North American genera of Atripliceae.<ref name="Zacharias" />

==Distribution==
''Proatriplex pleiantha'' is endemic to the Navajo Basin of [Arizona](/source/Arizona), [Colorado](/source/Colorado), [New Mexico](/source/New_Mexico), and [Utah](/source/Utah). It is very common in desert badlands, and occurs often in pure stands on saline clay soils of depressions, or together with other [halophyte](/source/halophyte)s in salt desert shrubs.<ref name="Zacharias" /> It grows at altitudes of 1400–1500 m.<ref name="FlNAmerica" />

==References==
<references>
<ref name="FlNAmerica">Stanley L. Welsh (2003): [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242415521 ''Atriplex pleiantha''] in Flora of North America, p.345</ref>
<ref name="Zacharias">Elizabeth H. Zacharias, Bruce G. Baldwin (2010): ''A Molecular Phylogeny of North American Atripliceae (Chenopodiaceae), with Implications for Floral and Photosynthetic Pathway Evolution''. In: ''Systematic Botany'' '''35'''(4), p.839-857. {{doi|10.1600/036364410X539907}}</ref>
</references>

==External links==
{{Wikispecies|Proatriplex}}
* {{GRIN genus|id=16074|name=''Proatriplex''}}
* [http://www.tropicos.org/Name/40037128 ''Proatriplex''] at Tropicos

{{Taxonbar|from1=Q22986033|from2=Q6086963}}

Category:Chenopodioideae
Category:Monotypic Amaranthaceae genera
Category:Flora of Arizona
Category:Flora of Colorado
Category:Flora of New Mexico
Category:Flora of Utah
Category:Endemic flora of the United States
Category:Plants described in 1950
Category:Taxa named by William Alfred Weber

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Adapted from the Wikipedia article [Proatriplex](https://en.wikipedia.org/wiki/Proatriplex) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Proatriplex?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.