Panicum amarum |
Poaceae subfam. panicoideae |
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bitter beachgrass, bitter panicgrass, bitter panicum |
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Habit | Plants perennial; rhizomatous, rhizomes stout, glabrous and glaucous throughout. | Plants annual or perennial; synoecious, monoecious, or dioecious; primarily herbaceous, habit varied. | ||||||||||||
Culms | 20-250 cm tall, 3-10 mm thick, erect or decumbent, simple or branched from the lower nodes; nodes glabrous; internodes glabrous, glaucous. |
annual, usually solid, sometimes somewhat woody, sometimes decumbent, often branched above the base. |
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Sheaths | shorter or longer than the internodes, not keeled, glabrous; collars often glaucous and purplish; ligules 1-5 mm; blades 7-50 cm long, 2-13 mm wide, erect or ascending, firm, thick, flat basally, more or less involute towards the apices. |
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Leaves | distichous; sheaths usually open; auricles usually absent; abaxial ligules usually absent, occasionally present as a line of hairs; adaxial ligules membranous, sometimes also ciliate, or of hairs, sometimes absent; blades sometimes pseudopetiolate; mesophyll radiate or non-radiate; adaxial palisade layer absent; fusoid cells usually absent; arm cells usually absent; kranz anatomy absent or present; midribs usually simple, rarely complex; adaxial bulliform cells present; stomata with triangular or dome-shaped subsidiary cells; bicellular microhairs usually present, with a long, narrow distal cell; papillae absent or present. |
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Panicles | 10-80 cm long, 2-17 cm wide, contracted, slightly nodding; primary branches whorled or opposite, strongly ascending to appressed; pedicels 0.5-15 mm, appressed to slightly divergent. |
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Inflorescences | ebracteate (Paniceae) or bracteate (most Andropogoneae) panicles, racemes, spikes, or complex arrangements of rames (in the Andropogoneae), usually bisexual, sometimes unisexual; disarticulation usually below the glumes, frequently in the secondary and higher order axes of the inflorescences. |
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Spikelets | 4-7.7 mm long, 1.5-2 mm wide, narrowly ovoid, glabrous, acuminate; lower florets staminate. |
bisexual or unisexual, frequently paired or in triplets, the members of each unit usually with pedicels of different lengths or 1 spikelet sessile. |
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Glumes | and lower lemmas relatively thick; lower glumes 2.8-4 mm, 1/2 - 4/5 as long as the spikelets, 3-9-veined, apices of the midveins sometimes scabridulous; upper glumes and lower lemmas extending 1.5-3 mm beyond the upper florets, apices stiffly gaping; upper glumes 3.9-7.6 mm, 5-9-veined; lower lemmas slightly shorter than the upper glumes, 7-9-veined, lower paleas 3-7 mm, oblong-hastate, folded over the anthers; lower florets staminate; upper florets 2.4-3.9 mm long, 1-1.8 mm wide, narrowly ovoid to oblong, glabrous, smooth, shiny, lemma margins clasping the paleas only at the base. |
usually 2, equal or unequal, shorter or longer than the adjacent florets, sometimes exceeding the distal florets; florets 2(-4), usually dorsally compressed, sometimes terete or laterally compressed; lower florets sterile or staminate, frequently reduced to a lemma; upper florets usually bisexual; lemmas hyaline to coriaceous, lacking uncinate hairs, often terminally awned; awns single; paleas of bisexual florets well-developed, reduced, or absent; lodicules usually 2, sometimes absent, cuneate, free, fleshy, usually glabrous; anthers 1-3; ovaries usually glabrous; haustorial synergids absent; style branches 2, free and close or fused at the base. |
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Caryopses | hila usually punctate; endosperm hard, without lipid; starch grains simple; embryos large in relation to the caryopses, usually waisted; epiblasts usually absent; scutellar cleft present; mesocotyl internode elongated; embryonic leaf margins usually overlapping, rarely just meeting, x = 5, (7), 9, 10, (12), (14). |
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2n | = 36, 54. |
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Panicum amarum |
Poaceae subfam. panicoideae |
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Distribution |
AL; CT; DE; FL; GA; LA; MA; MD; MS; NC; NJ; NM; NY; PA; RI; SC; TX; VA; WV
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Discussion | Panicum amarum grows in the coastal dunes, wet sandy soils, and the margins of swamps, along the Atlantic Ocean and the Gulf of Mexico from Connecticut to northeastern Mexico. It is also known, as an introduction, from a few inland locations in New Mexico, North Carolina, and West Virginia, as well as in the Bahamas and Cuba. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The subfamily Panicoideae is most abundant in tropical and subtropical regions, particularly mesic portions of such regions, but several species grow in temperate regions of the world. Within the Flora region, the Panicoideae are represented by 59 genera and 364 species. They are most abundant in the eastern United States (Barkworth and Capels 2000). Photosynthesis may be either C3 or C4. All three pathways are found in the subfamily, but the PCK and NAD-ME variants appear to have evolved only once, while the NADP-ME pathways seems to have evolved several different times (Giussani et al. 2001). The Panicoideae were first recognized as a distinct unit by Brown (1814), earlier than any of the other subfamilial taxa of the Poaceae. Its early recognition is undoubtedly attributable to its distinctive spikelets. Recognition of the tribe Gynerieae is recent (Sanchez-Ken and Clark 2001) and its placement in the Panicoideae, rather than the Centothecoideae, should be regarded as tentative. Spikelets with two florets are found in many other subfamilies, but rarely do they follow the pattern of the lower floret being sterile or staminate and the upper floret bisexual. Development of unisexual florets within the Panicoideae appears to be consistent across the subfamily (LeRoux and Kellogg 1999), but differs from that in the Ehrhartoideae (Zaitcheck et al. 2000). The Paniceae and Andropogoneae have their conventional interpretation in this Flora, so far as the North American taxa are concerned. Molecular studies, however, while strongly supporting the monophyly of the Andropogoneae, show the Paniceae to be paraphyletic, with two distinct clades. In one of these clades, most taxa have a chromosome base number of x = 9, but some have x = 10, and the taxa are pan-tropical in origin. The taxa in the other clade, with one exception, have a chromosome base number of x = 10 and are American in origin. This latter clade is sister to the Andropogoneae, which also have a chromosome base number of x = 10 (Gomez-Martinez and Culham 2000; Giussanni et al. 2001; Barber et al. 2002). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 25, p. 472. | FNA vol. 25, p. 351. | ||||||||||||
Parent taxa | Poaceae > subfam. Panicoideae > tribe Paniceae > Panicum > subg. Panicum > sect. Repentia | Poaceae | ||||||||||||
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Name authority | Elliott | Link | ||||||||||||
Web links |