View source for Dioscorea

{{Treatment/ID
|accepted_name=Dioscorea
|accepted_authority=Linnaeus
|publications={{Treatment/Publication
|title=Sp. Pl.
|place=2: 1032. 1753
|year=1753
}}, {{Treatment/Publication
|title=Gen. Pl. ed.
|place=5, 456. 1754
|year=1754
}}
|common_names=Yam;ñame
|basionyms=
|synonyms=
|hierarchy=Dioscoreaceae;Dioscorea
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Dioscoreaceae]]</div><div class="higher-taxon"><small>genus</small>[[Dioscorea]]</div></div>
|etymology=for Dioscorides, ca. 40–90, Greek physician, author of De Materia Medica
|volume=Volume 26
|mention_page=page 12, 479, 481, 484
|treatment_page=page 480
}}<!--

--><span class="statement" id="st-d0_s0" data-properties=""><b>Vines,</b> typically herbaceous;</span> <span class="statement" id="st-d0_s1" data-properties="whole_organism growth form or texture;whole_organism architecture;whole_organism architecture;whole_organism growth form">rhizomatous or tuberous.</span> <span class="statement" id="st-d0_s2" data-properties=""><b>Stems </b>twining clockwise or counterclockwise, branched or not, smooth or winged, polygonal or terete, glabrous or sometimes bearing prickles;</span> <span class="statement" id="st-d0_s3" data-properties="stem growth form;stem architecture;stem architecture;stem architecture;stem architecture;stem shape;stem shape;stem pubescence;stem pubescence">some species producing bulbils (branches modified into small aerial tubers) in leaf-axils.</span> <span class="statement" id="st-d0_s4" data-properties="leaf development;leaf arrangement;leaf arrangement;pattern arrangement or course"><b>Leaves </b>initiated in spiral pattern, modified in some species and appearing opposite or whorled.</span> <span class="statement" id="st-d0_s5" data-properties="node architecture;ultimate spicate life cycle;individual flower arrangement;individual flower arrangement;cyme architecture;flower atypical quantity;flower atypical quantity;flower quantity;flower architecture;flower architecture"><b>Inflorescences:</b> staminate nodes at ultimate flowering spicate or paniculate, individual flowers grouped in bracteolate cymes of (1–) 3 (–8) sessile or pedicellate flowers;</span> <span class="statement" id="st-d0_s6" data-properties="inflorescence architecture;inflorescence architecture;inflorescence architecture;inflorescence quantity;flower architecture;flower architecture;flower architecture;bract size">pistillate solitary or rarely fasciculate, 1 flower per node, sessile or subsessile, unbranched, subtended by pair of minute bracts.</span> <span class="statement" id="st-d0_s7" data-properties="flower reproduction;flower architecture;flower architecture;flower architecture"><b>Flowers </b>unisexual, staminate and pistillate flowers on different plants or rarely staminate and pistillate flowers on same plant;</span> <span class="statement" id="st-d0_s8" data-properties="tepal architecture or function or pubescence;tepal architecture or function or pubescence;tepal atypical some measurement;tepal some measurement">tepals glandular or not, 1–3 (–30) mm;</span> <span class="statement" id="st-d0_s9" data-properties="flower architecture;filament fusion;gynoecium prominence">staminate flowers with filaments distinct (connate basally only in D. polystachya), gynoecium rudimentary;</span> <span class="statement" id="st-d0_s10" data-properties="flower architecture;flower presence;staminode presence;ovary position;ovary length;style architecture;branch shape">pistillate flowers with staminodes present or sometimes absent, ovary inferior, usually 2–3 times length of perianth, style 3-branched, branches 2-fid;</span> <span class="statement" id="st-d0_s11" data-properties="pedicel architecture">pedicel, when present, not articulate.</span> <span class="statement" id="st-d0_s12" data-properties="fruit architecture;fruit architecture;fruit dehiscence;perianth duration;style duration"><b>Fruits </b>capsular, 3-winged, dehiscence loculicidal, perianth and styles generally persistent.</span> <span class="statement" id="st-d0_s13" data-properties="seed atypical quantity;seed quantity;seed shape;seed architecture;wing size"><b>Seeds </b>(1–) 2 per locule, compressed, usually winged unilaterally, bilaterally, or with wings expanded circumferentially;</span> <span class="statement" id="st-d0_s14" data-properties="">tannins, saponins present.</span> <span class="statement" id="st-d0_s15" data-properties="saponins presence;x chromosome quantity;x chromosome quantity">x = 9, 10.</span><!--

-->{{Treatment/Body
|distribution=Worldwide
|discussion=<p>Species ca. 600 (6 in the flora).</p><!--
--><p>The most comprehensive treatment to date (R. Knuth 1924) divides Dioscorea into 60+ sections. The native North American species are assigned to sect. Macropoda Uline: stems twining counter-clockwise, staminate flowers aggregated into more or less sessile cymes and with six fertile stamens, tepals united only at the base, and capsules as broad as or broader than long, reflexed at maturity, with seeds winged all around. This section also includes disjunct species from the Balkan Peninsula, the Himalayas, temperate East Asia, and the Caucasus Mountains.</p><!--
--><p>The taxonomy of Dioscorea is notoriously problematic. Many of the species are poorly known, and in the absence of comparative studies there has been an unchecked proliferation of names in the genus. That Dioscorea exhibits considerable diversity across its expansive geographic range is not contested, but a great many of the names in current use are very narrowly applied and lack any corroboration from field, laboratory, or herbarium studies. At present there is also no phylogenetic framework from which to interpret the variation that has been documented. Segregate genera have been erected, only to be subsumed again. A robust classification will ultimately emerge from rigorous systematic investigation, now in progress at research institutions around the world (L. R. Caddick et al. 2000; H. Huber 1998; P. Wilkin 1999; C. C. Xifreda 2000).</p><!--
--><p>Dioscorea species are cultivated circumtropically, especially in West Africa and the West Indies, for their starchy tubers (yams), the cultivars having been derived from about ten species, including three of the four taxa naturalized in the flora. The rhizomes/tubers of many noncomestible species accumulate varying concentrations of steroidal saponins (F. W. Martin 1969), and Dioscorea species of Mexican, South African, and Asian origin have been utilized extensively in the industrial synthesis of cortisone and human sex hormones. Much lower saponin yields are obtained from the native North American species than from the species harvested commercially elsewhere. Saponin content varies as a function of plant age and time of harvest, as well as phylogenetic position (L. Degras 1993). The rhizomes of D. villosa are included in some Native American pharmacopeias and are used to ease the pain of childbirth (H. H. Smith 1928). An alcohol extract of the “root” was widely administered in nineteenth- century eclectic medicine as a remedy for colic (H. H. Bartlett 1910).</p>
|tables=
|references=
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Plants rhizomatous; bulbils never produced in leaf axils; leaf margins entire or repand; petiole base never clasping.
|[[#key-0-2| > 2]]
|-id=key-0-1
|1
|Plants tuberous; bulbils produced in leaf axils; leaf margins lobed or entire; petiole base sometimes clasping.
|[[#key-0-4| > 4]]
|-id=key-0-2
|2
|Rhizomes brownish, nodes not articulate; staminate inflorescences solitary in leaf axils; perianth of both staminate and pistillate flowers greenish white; stamens erect; thecae distinct, widely spreading.
|[[Dioscorea villosa|Dioscorea villosa]]
|-id=key-0-2
|2
|Rhizomes yellow, nodes articulate, each bearing 1 dark, contrasting, ± deltate scale leaf or the dark vertical scar remaining once leaf falls; staminate inflorescences (1–)2–5 in leaf axils; perianth of both staminate and pistillate flowers orangish yellow; stamens inwardly curved; thecae connate.
|[[Dioscorea floridana|Dioscorea floridana]]
|-id=key-0-3
|3
|Leaf margins 3–5-lobed.
|[[#key-0-4| > 4]]
|-id=key-0-3
|3
|Leaf margins entire.
|[[#key-0-5| > 5]]
|-id=key-0-4
|4
|Leaf blade hastate-cordate, margins 3-lobed, apex acute or mucronate; petiole base not clasping; staminate plants flowering annually.
|[[Dioscorea polystachya|Dioscorea polystachya]]
|-id=key-0-4
|4
|Leaf blade reniform, margins irregularly 3–5-lobed, apex conspicuously caudate; petiole base clasping; plants rarely flowering.
|[[Dioscorea sansibarensis|Dioscorea sansibarensis]]
|-id=key-0-5
|5
|Stems broadly winged, 4-angular; distal leaves decussate, blade base sagittate; seeds winged all around.
|[[Dioscorea alata|Dioscorea alata]]
|-id=key-0-5
|5
|Stems terete, usually unwinged; leaves alternate throughout, blade base orbicular; seeds unilaterally winged.
|[[Dioscorea bulbifera|Dioscorea bulbifera]]
|}
</div></div><!--

-->{{#Taxon:
name=Dioscorea
|authority=Linnaeus
|rank=genus
|parent rank=family
|synonyms=
|basionyms=
|family=Dioscoreaceae
|distribution=Worldwide
|reference=None
|publication title=Sp. Pl.;Gen. Pl. ed.
|publication year=1753;1754
|special status=
|source xml=https://bibilujan@bitbucket.org/aafc-mbb/fna-fine-grained-xml.git/src/84153f6d59a0a91d69695978a64cee7560374f8e/V26/V26_1001.xml
|genus=Dioscorea
|bract size=minute
|branch shape=2-fid
|cyme architecture=bracteolate
|filament fusion=distinct
|flower architecture=pistillate;staminate;pistillate;pistillate;staminate;unbranched;subsessile;sessile;pedicellate;sessile
|flower atypical quantity=3;8
|flower presence=absent
|flower quantity=3
|flower reproduction=unisexual
|fruit architecture=3-winged;capsular
|fruit dehiscence=loculicidal
|gynoecium prominence=rudimentary
|individual flower arrangement=grouped;paniculate
|inflorescence architecture=fasciculate;solitary;pistillate
|inflorescence quantity=1
|leaf arrangement=whorled;opposite
|leaf development=modified
|node architecture=staminate
|ovary length=2-3 times length of perianth
|ovary position=inferior
|pattern arrangement or course=spiral
|pedicel architecture=articulate
|perianth duration=persistent
|saponins presence=absent
|seed architecture=winged
|seed atypical quantity=1;2
|seed quantity=2
|seed shape=compressed
|staminode presence=absent
|stem architecture=winged;smooth;not;branched
|stem growth form=twining
|stem pubescence=sometimes;glabrous
|stem shape=terete;polygonal
|style architecture=3-branched
|style duration=persistent
|tepal architecture or function or pubescence=not;glandular
|tepal atypical some measurement=3mm;30mm
|tepal some measurement=1mm;3mm
|ultimate spicate life cycle=flowering
|whole_organism architecture=tuberous;rhizomatous
|whole_organism growth form=vine
|whole_organism growth form or texture=herbaceous
|wing size=expanded
|x chromosome quantity=10;9
}}<!--

-->[[Category:Treatment]][[Category:Dioscoreaceae]]