Thinopyrum intermedium |
Poaceae subfam. pooideae |
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intermediate wheatgrass |
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Habit | Plants rhizomatous, often glaucous. | Plants annual or perennial; sometimes matlike, sometimes cespitose, sometimes stoloniferous, sometimes rhizomatous. | ||||||||||||||||||||||||||||||||||||||||
Culms | 50-115 cm, glabrous or hairy, sometimes hairy only on the nodes; lowest internode plus sheath 3-5 mm thick. |
usually hollow, sometimes solid. |
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Sheaths | mostly glabrous, often ciliate on the margins; auricles 0.5-1.8 mm; ligules 0.1-0.8 mm; blades 2-8 mm wide, flat, abaxial surfaces glabrous, adaxial surfaces usually sparsely strigose, sometimes with hairs of mixed lengths, with 7-30 ribs, ribs not prominent, margins whitish, thicker than the veins. |
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Leaves | distichous; sheaths usually open to the base, varying to closed for nearly their full length; auricles present or absent; abaxial ligules absent; adaxial ligules scarious or membranous, sometimes puberulent or scabridulous, usually not ciliate, cilia sometimes shorter than the base; pseudopetioles rarely present; blades usually linear, sometimes broadly so, venation parallel; cross sections non-Kranz, mesophyll nonradiate, adaxial palisade layer absent, fusoid and arm cells usually absent; midribs usually simple; adaxial bulliform cells present; stomates with parallel-sided subsidiary cells; epidermes usually lacking bicellular microhairs, sometimes with unicellular microhairs, papillae usually absent, when present, rarely more than 1 per cell. |
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Inflorescences | usually terminal, panicles, spikes, or racemes, usually ebracteate; disarticulation usually below the florets, sometimes below the glumes, at the rachis nodes, or at the inflorescence bases. |
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Spikes | 8-21 cm, erect or lax; internodes 7-12 mm; rachises glabrous or with hairs, scabrous on the edges, particularly distally, not disarticulating at maturity. |
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Spikelets | 11-18 mm, with 3-10 florets; disarticulation beneath the florets. |
usually bisexual, infrequently unisexual or mixed, usually laterally compressed or not compressed, occasionally dorsally compressed, with 1-30 sexual florets, distal floret(s) often reduced, infrequently spikelets with 1-2 reduced or staminate basal florets and a single terminal sexual floret. |
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Glumes | oblong, glabrous and mostly smooth, or strigose with 1-1.5 mm hairs, hairs usually evenly distributed, weakly keeled distally, keels scabrous, at least distally, midvein usually more prominent and longer than the lateral veins, margins not hyaline or hyaline near the apices, apices obliquely truncate or obtuse to acute, sometimes mucronate; lower glumes 4.5-7.5 mm long, 1.5-2.5 mm wide, 5-6-veined; upper glumes 5.5-8.5 mm long, 2-3 mm wide, 5-7-veined; lemmas 7.5-10 mm, glabrous or with 1-1.5 mm hairs, hairs usually evenly distributed, sometimes only on the outer portion of the lemmas, apices occasionally awned, awns to 5 mm; paleas 7-9.5 mm, keels usually scabrous for 1/2 their length; anthers 5-7 mm. |
usually 2, upper or lower glumes sometimes absent, rarely both glumes absent; lemmas without uncinate hairs, awned or not, awns single, basal to apical; paleas usually well-developed, sometimes reduced or absent; lodicules 2(3), usually lanceolate and broadly membranous distally, rarely truncate and fleshy, usually not veined or obscurely veined, sometimes distinctly veined, sometimes ciliate; anthers (1, 2)3; ovaries glabrous or sometimes hairy distally, sometimes with an apical appendage; haustorial synergids absent; styles (1)2 (-4), bases close together, sometimes fused. |
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Caryopses | hila linear, elliptic, ovate, or punctate; endosperm usually hard, sometimes soft or liquid, with or without lipids, starch grains compound or simple; embryos less than 1/2 the length of the caryopses; epiblasts usually present; scutellar cleft usually absent; mesocotyl internode usually absent; embryonic leaf margins overlapping, x = 7, 10. |
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2n | = 42, 43. |
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Thinopyrum intermedium |
Poaceae subfam. pooideae |
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Distribution |
AZ; CA; CO; GA; IA; ID; MA; MT; ND; NE; NJ; NM; NV; NY; OR; SD; TX; UT; WA; WY; BC; SK; YT
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Discussion | Thinopyrum intermedium is native to Europe and western Asia. It is widely established in western North America, having been introduced for erosion control, revegetation, forage, and hay. It also occurs in scattered locations further east. One of its advantages for erosion control and revegetation is that it establishes rapidly in many different habitats. In its native range, it grows in dry areas with sandy or stony soils. In Europe, it forms sterile hybrids with Elymus repens; no such hybrids are known from North America. Several subspecies have been recognized within Thinopyrum intermedium, usually based on differences in the vestiture of the glumes and lemmas, the presence or absence of lemma awns, and the color of the plants. Assadi (1994) commented that there was little correlation between the different character states. He grew seeds from several wild plants and, even when most of the offspring resembled the parent plant, there was often segregation of some variants. Crossing experiments showed that hybrids between the morphological variants were fertile, and usually had regular meiosis. He noted, however, that the plants with glabrous spikelets tended to grow in mesophytic habitats, those with hairy glumes and lemmas on dry slopes, and those with ciliate glumes and lemmas at the edges of fields and in wet places. This difference in habitat preference was reiterated by Ogle (2001). Because of this ecological distinction, they are formally recognized here as subspecies. Plants with hairs only near the lemma margins are included under T. intemedium subsp. intermedium. They may be derived from crosses between the hairy and glabrous plants, a possibility that has not been experimentally evaluated. There seems to be little correlation between spikelet vestiture and that of the leaves and stems. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The subfamily Pooideae includes approximately 3300 species, making it the largest subfamily in the Poaceae. It reaches its greatest diversity in cool temperate and boreal regions, extending across the tropics only in high mountains. The circumscription and relationships of tribes within the Pooideae are unsettled (see, for example, Catalan et al. 1997, 2004; Soreng and Davis 1998). In this flora, some previously recognized tribes have been combined with the Poeae. Recognition of some of these as subtribes is well supported; among these is the Hainardieae Greuter (which, at the subtribal level, is called the Parapholiinae Caro). Members of other traditional tribal groupings, such as the Aveneae Dumort., appear to be widely dispersed within the Poeae sensu lato. Further work will probably support the division of the expanded Poeae into additional tribes; there is as yet no clear indication as to what the boundaries of such tribes should be. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 374. | FNA vol. 24, p. 57. | ||||||||||||||||||||||||||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Triticeae > Thinopyrum | Poaceae | ||||||||||||||||||||||||||||||||||||||||
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Synonyms | Elytrigia intermedia, Elymus hispidus, Agropyron tricophorum, Agropyron intermedium var. trichophorum, Agropyron intermedium | |||||||||||||||||||||||||||||||||||||||||
Name authority | (Host) Barkworth & D.R. Dewey | Benth. | ||||||||||||||||||||||||||||||||||||||||
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