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FOC | Family List | FOC Vol. 22 | Poaceae | Poa

5. Poa subg. Stenopoa (Dumortier) Soreng & L. J. Gillespie, Aliso (in press). 2006.

林地亚属 lin di ya shu

Authors: Guanghua Zhu, Liang Liu & Marina V. Olonova

Poa sect. Stenopoa Dumortier.

Perennials, tufted, some with thin, short rhizomes, sometimes stoloniferous (P. sect. Pandemos) or strongly rhizomatous (P. sect. Tichopoa). Shoots extra- and intravaginal. Culms usually rounded, sometimes strongly compressed (P. sect. Tichopoa), smooth or scabrid. Leaf sheaths mostly closed for 1/20–1/6(–1/4 in P. sect. Pandemos) of length; leaf blades flat, thin, soft to folded or inrolled, firm and hard. Panicle lax to very dense, and spiciform, branches with dense short prickles on angles. Spikelets 3–5(–8) mm, florets 1–3(–8); vivipary absent; rachilla smooth, warty or pubescent; both glumes 3-veined; lemma soft, usually pubescent at least on keel and marginal veins, sometimes also lower part between veins, rarely entirely glabrous; veins slightly raised; callus webbed to glabrous or with a short crown of hairs; palea usually smooth, sometimes pubescent between keels, keels with short prickles, very rarely proximally ciliate. Anthers (1–)1.2–2 mm.

About 40 species: Asia, Europe, North America, a few species in South America; 18 species (one endemic, at least one introduced) in China.

The Chinese species belong to four sections: Poa sect. Secundae V. L. Marsh ex Soreng (species no. 64); P. sect. Pandemos Ascherson & Graebner (species no. 65); P. sect. Tichopoa Ascherson & Graebner (species no. 66); and P. sect. Stenopoa Dumortier (species nos. 67–81). The other two sections in the subgenus, namely P. sect. Abbreviatae Nannfeldt ex Tzvelev and P. sect. Oreinos Ascherson & Graebner, do not occur in China.

Many species in Poa sect. Stenopoa hybridize easily, and have formed a series of morphologically and genetically distinct populations. These are supposed to have been stabilized by apomixis. The situation is made more complex by P. glauca, P. nemoralis, and P. palustris, which are represented by many cytological races of vague taxonomic status. These have hybridized with other species of P. sect. Stenopoa to form agamic complexes, which are supposed to have arisen quite long ago, perhaps during the Pleistocene (Tzvelev, Fl. European Part USSR 1: 117–368. 1974). Four of these have differentiated sufficiently to be treated as the distinct hybridogenous species P. albertii, P. araratica, P. lapponica, and P. urssulensis. Some polytypic species are also accepted. Their subspecies are geographically separated; some may be of hybrid origin, but are close to one parent as result of introgression.

1 Sheaths of upper culm leaves closed for 1/4(–1/3) of length; lower glume 1-veined, often sickle-shaped; lemma with or without a bronze-yellowish band below apex, lateral veins faint to prominent; vegetative shoots extravaginal and/or intravaginal; plants loosely tufted, stoloniferous (sometimes with short lateral shoots with small beadlike swellings); sheaths compressed, usually densely retrorsely scabrid, collars not ciliate; blade papery, flat, apex simple acuminate (P. sect. Pandemos).   65 P. trivialis
+ Sheaths of upper culm leaves closed for 1/20–1/5(–1/4) of length; lower glumes (1 or)3-veined; lemma commonly with a bronze-yellowish band below apex, lateral veins mostly faint; vegetative shoots all or mostly extravaginal (rarely mostly intravaginal); plants rarely with well-developed rhizomes (but if rhizomatous then culms and nodes strongly compressed: P. sect. Tichopoa)   (2)
2 (1) Plants with well-developed rhizomes; culms isolated, nodes and internodes strongly compressed; callus usually webbed (P. sect. Tichopoa).   66 P. compressa
+ Plants without rhizomes (or at most with poorly developed lateral shoots, or short upward-directed bladeless shoots, or somewhat stoloniferous in riparian forms of Poa palustris); culms usually closely clustered, nodes and internodes not or only slightly compressed, but if compressed then plants not rhizomatous; callus webbed or not   (3)
3 (2) Lemmas weakly keeled, glabrous; spikelets 2.5 or more × as long as wide; callus glabrous; panicle contracted, linear; spikelets not viviparous (P. sect. Secundae).   P. secunda subsp. juncifolia
+ Lemmas strongly keeled, pubescent (infrequently glabrous); spikelets commonly 1.5–2 × as long as wide; callus with a dorsal web or glabrous; panicle open or contracted, linear to pyramidal; spikelets sometimes viviparous (P. sect. Stenopoa)   (4)
4 (3) Panicle with viviparous spikelets.   80 P. albertii
+ Panicle without viviparous spikelets   (5)
5 (4) Plants up to 25(–40) cm of alpine and subalpine belt (if from lower elevation steppe see   77 P. versicolor; upper node usually not exposed.
+ Plants (25–)30–100 cm, sometimes alpine; uppermost node usually exposed   (11)
6 Plants 20–30 cm, subalpine (to low alpine)   (7)
+ Plants 5–15(–25) cm, alpine, if taller, then spikelets 5–8 mm, leaf blade green, soft   (8)
7 (6) Ligule 3–8 mm, 2–4 × as long as blade width, lemma glabrous between veins.   76 P. hylobates
+ Ligule 0.7–3 mm (if longer, lemma pubescent between veins), usually equal to blade width.   78 P. araratica
8 (6) Panicle contracted, densely ovoid to spiciform, longest branches 1(–1.5) cm, spikelets crowded, 3–4(–5) mm; uppermost internode not more than 1 mm wide; leaf blade firm in age, narrow, folded or inrolled; plant pale or grayish yellow, glumes sometimes with purplish bands   (9)
+ Panicle elongated, sometimes quite open, longest branches 1.5–2 cm, spikelets moderately crowded to sparse, (3.8–)4–5.5(–6) mm; uppermost internode frequently up to 1.5–2 mm wide; leaf blade withering, folded or flat; plant glaucous, glumes and vegetative parts frequently strongly purplish   (10)
9 (8) Densely tufted, shoots mostly intravaginal; leaf blades inrolled, 0.5–1 mm wide.   79 P. attenuata
+ Moderately tufted, shoots mostly extravaginal; leaf blades folded, 1–1.5 mm wide.   80 P. albertii
10 (8) Callus glabrous (rarely with a few short hairs).   80 P. albertii
+ Callus webbed.   81 P. glauca
11 (5) Mesomorphic plants; culm with uppermost node more than 1/3(–1/2) way up, leaf blade soft, flat, 1–5 mm wide, usually longer than sheath; ligule up to 1.5 × blade width; panicle open   (12)
+ Xeromorphic plants; culm with uppermost node up to 1/3 way up, if up to 1/2 way up and/or plant mesomorphic, then ligule more than 1.5 × blade width; leaf blade firm or soft, folded or flat, 0.5–2.5(–3.5) mm broad, much shorter to infrequently longer than sheath   (18)
12 (11) Ligule 2–3 mm, callus of lemma webbed.   70 P. palustris
+ Ligule of uppermost leaves 0.2–1.5 mm, usually less than blade width (if C Asia, see also   75 P. nemoraliformis
13 Spikelets 4–8 mm, blades (2–)3–8 mm, plants with bluish bloom, scabrid near nodes.   69 P. sichotensis
+ Spikelets up to 4 mm; blades 1–3 mm, plants green, smooth near nodes   (14)
14 (13) Rachilla pubescent   (15)
+ Rachilla glabrous   (16)
15 (14) Ligule up to 1 mm; palea with prickles on keels and glabrous between them   67 P. nemoralis
+ Ligule 1–2 mm; if less than 1 mm, then palea with short hairs on the lower part of keels and pubescent between them.   68 P. lapponica
16 (14) Culm with uppermost node usually at or above middle, culm usually smooth; rachilla warty, never pilose (infrequently sparsely hispidulous).   68 P. lapponica
+ Culm with uppermost node 1/3–1/2 way up; culm usually scabrid; rachilla warty or pilose   (17)
17 (16) Plants firm and robust; leaf blade 1.5–2.5(–3) mm, firm; leaf sheath usually longer than blade; low-elevation grasslands of central and eastern provinces.   72 P. sphondylodes
+ Plants soft and slender; leaf blade 1–1.5(–2) mm, thin; leaf sheath usually shorter than blade; mountain forest margins and high-elevation grass slopes of central and western provinces.   73 P. faberi
18 (11) Plants with 2(or 3) nodes above 1 cm at the base; leaf blade firm or soft and withering in age; uppermost blade usually very narrow and folded, short, usually less than 1/2 as long as sheath to subequal; panicle open to densely spiciform   (19)
+ Plants with 3–5 nodes above 1 cm at the base (if 2, then leaves long, soft, and flat), leaf blade soft and withering with age, never firm, uppermost blades frequently flat, usually more than 1/2 as long as sheath; panicle open or contracted (if contracted, then with blades soft and withering in age), with long erect branches, 1/2 as long as panicle, never dense and spiciform   (22)
19 (18) Panicle dense, contracted to spiciform, branches erect, the longest ones 1/5–1/3(–2/5) as long as panicle; uppermost node usually below 1/6 way up culm.   77 P. versicolor
+ Panicle usually open, especially while flowering, longest branches 1/3–1/2 as long as panicle; uppermost node usually ca. 1/6 way up culm   (20)
20 (19) Plants robust, up to 100(–120) cm; uppermost internode 30–80 cm, up to 2.5 mm in diam. in fruiting material; plants of E and NE China.   71 P. alta
+ Plants slender, 30–45(–55) cm, uppermost internode up to 35 cm long, up to 1.5 mm in diam   (21)
21 (20) Densely to sparsely tufted plants with few leaves; spikelets up to 5 mm; ligule (1–)2–7 mm; plants widespread.   77 P. versicolor
+ Loosely tufted, leafy plants; spikelets up to 6(–6.5) mm; ligule up to 1(–1.5) mm; plants of NW mountains.   75 P. nemoraliformis
22 (18) Plants with 2 nodes; panicle with scattered spikelets; spikelets 4.5–5.5(–8) mm; uppermost internode frequently thick, up to 1.5–2 mm, but not elongated; plant glaucous, frequently dark purple; plants of alpine and subalpine belts.   (go to lead 7)
+ Plants with 3–5 nodes; panicle usually with crowded spikelets; spikelets 3–5.5(–6) mm; uppermost internode usually 1–1.5 mm (if 1.5–2.5(–3) mm then very elongated); plants green or tinged purple, of hills to lower alpine belt   (23)
23 (22) Ligule up to 2 mm   (24)
+ Ligule 2–8 mm   (26)
24 (23) Ligule up to 1(–1.5) mm.   71 P. alta
+ Ligule 1–2 mm   (25)
25 (24) Panicle elongated-pyramidal with quite dense to scattered spikelets 3–4 mm; plants of lower mountain belt in N China.   74 P. urssulensis
+ Panicle with long erect branches and scattered spikelets (3.5–)5–7 mm; plants of high mountain belt in W and NW China.   75 P. nemoraliformis
26 (23) Callus glabrous (sometimes with a few short hairs), panicle usually open.   76 P. hylobates
+ Callus usually webbed; panicle usually loosely contracted   (27)
27 (26) Plants firm and robust; leaf blade 1.5–2.5(–3) mm, firm; leaf sheath usually longer than blade; low-elevation grasslands of C and E provinces.   72 P. sphondylodes
+ Plants soft, slender; leaf blade 1–1.5(–2) mm, thin; leaf sheath usually shorter than blade; mountain forest margins and high-elevation grass slopes of C and W provinces.   73 P. faberi

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