Poa L.
Poaceae, grass family.
Vegetative morphology. Plants perennial herbs; 5–23–65 cm high; caespitose, or not caespitose. Ground-level or under-ground stems horizontal, or not developed horizontally or vertically; rhizomatous (when present); elongate, or compact; 0.5–0.7825–1.2 mm wide. Scales present; grooved; 0.5–1.25–2 mm long; glabrous. Aerial stems erect, or decumbent; circular or oval in cross-section; glabrous. Leaves distributed along the stems (rarely), or in a basal tuft (usually); alternate; not distinctly distichous; marcescent. Prophylls 0.415–6.788–30 mm long; with smooth veins, or with scabrous veins; with pronounced keels, or lacking pronounced keels. Petioles absent. Sheaths with the margins fused only in the lower part; glabrous; collars present. Ligules present; 0.4–1.9–5 mm long; membranous; glabrous, or hairy; linear, or lanceolate, or ovate-oblong, or transversely oblong; apices acuminate, or acute, or obtuse, or truncate; entire, or erose, or lacerate. Blades 5–550 mm long; 0.4–0.8714–1.8 mm wide. Blades appressed to the stem, or spreading; folded in bud; linear; with sheath auricles, or without auricles; flat, or folded (with boat shaped tips); veins parallel; midvein conspicuously larger than the lateral veins, or midvein similar in size to other veins in the leaf; bulliform cells in distinct rows on either side of the midvein, or without bulliform cells in a distinct row on either side of the midvein. Blades adaxial surface glabrous, or scabrous, or hairy. Blades abaxial surface glabrous, or scabrous.
Reproductive morphology. Flowering stems present. Flowering culm nodes not rooting at the lower nodes; not exposed, or becoming exposed; number visible 0–3. Flag leaf sheaths inflated, or not inflated. Inflorescence paniculate; linear, or lanceolate, or ovate; 0.3–4–13 cm long; 2–25–75 mm wide; main axis glabrous, or scabrous. Number of inflorescence branches at lowest node 1–4. Inflorescence primary branches 2–14–50 mm long; glabrous, or scabrous; with appressed secondary branches, or with spreading secondary branches. Spikelets pedicellate; disarticulating above the glumes; laterally compressed; obovate; 3–5.3–7.5 mm long; 1.2–2.8–5.6 mm wide. Florets per spikelet 2–6. First glume 0.7–0.87–1 × the length of the second glume; 0.4–0.6–0.8 × spikelet length; 1.9–3.2–5 mm long; lanceolate, or ovate; glabrous; margins glabrous; veins 1–3; apex acute. Second glume 0.4–0.9 × as long as the spikelet; almost as long as, or longer than, the lowest floret; lanceolate, or ovate, or oblanceolate; 2.2–3.7–5 mm long; glabrous, or with trichomes; veins 3. Rachilla internode 0.6–1.1–1.8 mm long; glabrous. Rachilla not pronounced between the florets; extending beyond the uppermost floret. Callus differentiated, or not differentiated; hairs 1.5–1.75–2 mm long; hairs shorter than the floret. Lemma 2.7–3.9–5.3 mm long; ovate, or lanceolate, or oblanceolate; keeled, or rounded on the back; surface dull; surface hairy; surface with trichomes on and between the veins; veins 5. Lemma apex acute, or rounded, or truncate; entire, or erose; awnless. Palea well developed; 2.3–3.3–4.5 mm long; with scabrous veins, or with hairy veins. Perianth reduced to lodicules. Stamens 3. Anthers 0.6–1.5–2.3 mm long. Gynoecia superior. Carpels syncarpous; 3. Styles 2. Ovules 1. Fruit sessile. Fruit dry; a caryopsis; indehiscent. Fruit 1.4–1.9–2.5 mm long. Seeds 1.
Ecology and habitat. Substrates: rocks (often on sandstone), gravel, sand, silt, clay, till, moss (often of owl perches).
Notes. Gillespie and Boles (2001) reported on phylogentic relationship
and infraspecific variation in Canadian Arctic Poa based on chloroplast
DNA restriction site data. They found infraspecific variation in three species,
but only in P. hartizii subsp. hartzii did it correspond to
infraspecific taxa. They suggested variation found in P. pratensis had a
geographical rather that taxonomic basis, and hypothesized that it corresponds
to indigenous arctic rather than the influence of introduced extra-arctic
populations. In P. glauca, cpDNA variation was detected only in western
Low Arctic and boreal populations and it was suggested this may represent
greater variation where the species survived the Pleistocene glaciations. In
cladisic analyses of the data the authors found that Poa sect. Poa
comprising P. arctica and P. pratensis was strongly supported and
that these taxa were not closely related to P. alpina. Poa hartzii was
confirmed as a member of a paraphyletic sect. Secundae. Poa glauca and
P. abbreviate are distinct members within a generally unresolved sect.
Stenopoa-Abbreviatae complex.
The description that follows is a
restricted one that was produced by combining data for the taxa occurring in the
eastern Canadian Arctic Archipelago, using INTKEY.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).