Flora of the Canadian Arctic Archipelago

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S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Poa L.

English: Blue grass.

Poaceae, Grass family.

Published in Sp. Pl. 67. 1753.

Synonymy. Arctopoa (Griseb.) Prob., Novosti Sist. Vyssh. Rast. 11: 49. 1974.

Vegetative morphology. Plants 5–65 cm high; perennial herbs; caespitose, or not caespitose. Only fibrous roots present. Ground level or underground stems horizontal, or absent; rhizomatous (when present); elongate, or compact; 0.5–1 mm wide. Ground level or underground stems scales present; surfaces striate, or grooved; 0.5–2 mm long; glabrous. Aerial stems erect, or decumbent. Leaves distributed along the stems (rarely), or mainly basal (usually); alternate; not distinctly distichous; marcescent. Prophylls 5–70 mm long; with smooth veins, or with scabrous veins; with pronounced keels, or lacking pronounced keels. Petioles absent. Sheaths present; with the margins fused only in the lower part; glabrous, or with trichomes; scabrous; sheath collars present. Ligules present; 0.4–5 mm long; membranous; glabrous, or hairy; lanceolate, or ovate-oblong, or transversely oblong. Ligule apices acuminate, or acute, or obtuse, or truncate; entire, or erose, or lacerate. Leaves grass-like. Blades 7–170 mm long, 0.4–1.8 mm wide, appressed to the stem or spreading, folded in bud, linear, 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. Blade adaxial surface glabrous or scabrous or hairy. Blade abaxial surface glabrous or scabrous.

Reproductive morphology. Flowering stems circular or oval in cross section. Flowering stems with leaves; not rooting at the lower nodes; culm nodes not exposed, or becoming exposed; culm nodes number visible 0–2. Flag leaf sheaths inflated, or not inflated. Inflorescences paniculate; dense, or diffuse; linear, or lanceolate, or ovate; 0.3–12.5 cm long; 2–75 mm wide. Inflorescences main axis glabrous, or scabrous. Number of inflorescence branches at lowest node 1–5. Inflorescence primary branches 2–50 mm long; glabrous, or scabrous; with appressed secondary branches, or with spreading secondary branches. Spikelets disarticulating above the glumes; ovate; 3–7.5 mm long; 1.2–5.6 mm wide. Florets per spikelet 2–6. Two glumes present. First glume 0.7–1 × the length of the second glume; 0.4–0.6–0.8 × spikelet length; 1.9–5 mm long; lanceolate, or ovate; glabrous; margins glabrous; veins 1–3; apex acuminate, or acute. Second glume 0.4–0.9 × as long as the spikelet; almost as long as, or longer than, the lowest floret; 2.2–5 mm long. Second glume lanceolate, or ovate, or oblanceolate. Second glume glabrous, or with trichomes; veins 3. Rachilla not pronounced between the florets; extending beyond the uppermost floret; internode 0.6–1.8 mm long; internode glabrous. Callus differentiated, or not differentiated; hairs 1.5–2 mm long; hairs shorter than the floret. Lemma ovate, or lanceolate, or oblanceolate; 2.7–5.3 mm long; keeled, or rounded on the back; surface dull; surface hairy; surface with trichomes on veins only, or on and between the veins; veins 5; apex acute, or rounded, or truncate; apex entire, or erose; awnless. Palea well developed; 2.3–4.5 mm long; veins scabrous, or hairy. Flowers bilaterally symmetrical (zygomorphic). Perianth represented by lodicules. Stamens 3. Anthers 0.6–2.5 mm long. Ovary superior; carpels 3; syncarpous. Ovaries glabrous. Styles 2. Placentation basal. Ovules per ovary 1. Fruit sessile; dry; a caryopsis; 1.4–2.5 mm long; indehiscent. Seeds 1.

Ecology and habitat. Substrates: rocks (often on sandstone), gravel, sand, silt, clay, till, moss (often of owl perches).

North American distribution. Range in the Canadian Arctic Archipelago widespread. Common.

General notes. Gillespie and Boles (2001) reported on phylogenetic relationships 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 did it correspond to infraspecific taxa. They suggested that the variation found in P. pratensis has a geographical, rather that taxonomic basis, and hypothesised that it corresponds to indigenous arctic populations compared with 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 cladistic 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 for the genus is a restricted one that was produced by combining data for the taxa occurring in the Canadian Arctic Archipelago, using INTKEY.

Illustrations. • Dissected spikelets of three species.


This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.

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