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

Descurainia sophioides (Fisch.) Schulz

English: Tansy-mustard.

Brassicaceae (Cruciferae), Draba family.

Published in In Engl., Pflanzenreich IV-105, 86: 316. 1924.

Type: Described from Alaska: Kotzebue Sound.

Synonymy. Sisymbrium sophioides Fisch., in Hooker, Fl. Bor.-Amer. 1: 61, t. 20. 1829.

Vegetative morphology. Plants 25–100(–150) cm high; biennial herbs; caespitose, or not caespitose. Taproot present. Caudex absent. Aerial stems erect. Leaves mainly basal (first year plants), or distributed along the stems; alternate; persistent, or dying annually and non-persistent (leaves of flowering stems). Petioles present; 1.5–2.5 mm long; without sessile glands (but sometimes with a few stalked glands); shallowly concave in cross section; glabrous, or hairy; pubescent (sparse glandular hairs). Petiole hairs shorter than the diameter of the petiole; spreading; straight. Leaf blades compound. Blades (10–)28–35(–60) mm long, 10–14(–20) mm wide, spreading, veins pinnate. Blade adaxial surface glabrous or glabrescent (with irregularly forked hairs), hairs puberulent, hairs glandular, hairs sparse, hairs white, or translucent. Blade abaxial surface hairy, hairs pubescent or villous, hairs sparse, hairs white, hairs irregularly branched, hairs spreading. Blades cut into linear divisions. Blade margins deeply divided; degree of incision 80–90%. Hydathodes absent. Blade apices acute. Leaflet arrangement pinnate. Leaflets (3–)6–17; (4–)8–12(–15) mm long (CAN 526659); (0.5–)1–2(–4) mm wide (CAN 273658); lanceolate; veins inconspicuous. Apical leaflet base not distinctly stipitate.

Reproductive morphology. Flowering stems solitary; with leaves. Flowering stems hairy. Flowering stems puberulent. Flowering stem hairs simple; glandular hairs present (stalked). Inflorescences racemose (very dense and subumbellate, elongating slowly so flowers at apex are overtopped by immature siliques); terminal, or lateral; dense (in flower), or diffuse; 1 cm long (in flower to 20 cm in fruit); (7–)10–20 mm wide; elongating as the fruit matures. Pedicels present; with non-glandular hairs (sparse). Flowers per inflorescence 20–70 (or more); small; radially symmetrical (actinomorphic). Sepals conventional; 4; free; 0.8–1.2 mm long; 1.7–2 mm wide; green and purple; herbaceous. Calyx glabrous. Petals conventional; free; 4; yellow; without contrasting markings; obovate; unlobed; 2–3.5 mm long; 0.3–0.5 mm wide (at apex, tapering to 0.1 at base). Stamens 6; stamen filaments markedly unequal in length; stamen filaments glabrous. Anthers yellow; ellipsoid; 0.1–0.2 mm long. Ovary superior; carpels 2; syncarpous. Ovaries glabrous. Styles 1; thick and short; 0.1–0.2 mm long; straight. Stigmas per ovary 1. Placentation parietal. Ovules per ovary 15–20. Fruit stalked (pedicels spreading, becoming re-curved in age); stalk (3–)5–7 mm long; dry; a silique; elongate-cylindrical; purple and yellowish; 20–27(–30) mm long; 1–1.5 mm wide; glabrous; distinctly flattened (somewhat torulose); dehiscent; shedding the outer walls to expose a thin inner wall, with the seeds attached at the margins on either side. Styles remaining straight; persisting in fruit 0.2–0.3 mm long. Seeds 24–36; 1–1.2 mm long (long and slender); brown (orangish); surfaces smooth.

Chromosome information. 2n = 14.

2n = 14. Mulligan (1961); Packer (1964); Mulligan and Porsild (1970, northwestern Canada); Zhukova et al. (1973, Wrangel Island; 1977, northern Siberia); Veselukhina (1976, northeastern Asia); Yurtsev and Zhukova (1982, northern Siberia); Löve and Löve (1982, Arctic Canada); Petrovsky and Zhukova (1983, Wrangel Island); Zhukova and Petrovsky (1984, northern and northeastern Asia); Mulligan (2003).

Ploidy levels recorded 2x.

Taxon as an environmental indicator. Plants of this species are frequently found growing on rubbish heaps near settlements.

Ecology and habitat. Substrates: wet meadows, slopes, ridges; dry, moderately well-drained areas; rocks, gravel, silt, clay; with low organic content, with high organic content, peat; acidic, or calcareous, or non-calcareous. This mustard has basal leaves that are present early in the season and fern-like. They wither as flowering proceeds. The plant has small yellow flowers that are clustered together when flowering starts, but spread out as blooming proceeds. There is much variation in plant height (see image library). Burt (2000) reported that plants are to 1.5 m high at Bathurst Inlet, and to about 0.5 m high at Holman on Victoria Island. The plants are common in the western arctic in areas where the soil has been disturbed, such as around settlements, and along roads and in dumps.

North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut. Range in the Canadian Arctic Archipelago limited. Uncommon. Low Arctic. Arctic islands: Banks, Victoria.

Northern hemisphere distribution. Amphi-Beringian (broadly). Polar Ural – Novaya Zemlya (?), Yamal–Gydan, Taimyr – Severnaya Zemlya, Anabar–Olenyok, Kharaulakh, Yana–Kolyma, West Chukotka, Wrangel Island, South Chukotka, East Chukotka, West Alaska, North Alaska – Yukon, Central Canada, Labrador – Hudson Bay.

Illustrations. • Close-up of plant: Iqaluit. New record for the area. Nunavut, Baffin Island, Iqaluit. August, 2005. Photograph by Kathy Thornhill. • Close-up of inflorescence. Characteristic yellow flowers with long siliques developing. New record for the area. Nunavut, Baffin Island, Iqaluit. August, 2005. Photograph by Kathy Thornhill. • Habitat: Rankin Inlet. Tall plants to shoulder height, approximately 130–140 cm high, growing on a mound in a wet meadow. Water was not limiting growth and there may have been additional nutrients available from anthropogenic influences. Nunavut, Rankin Inlet. 27 July, 2001. Aiken and Brysting 01–047a. CAN. • Plant habit. Plant growing between the markers, isolated in dry gravel, and approximately 15–20 cm high. Manitoba, Churchill. 26 July, 2001. Aiken and Brysting 01–045. CAN. Scale bar in cm. • Plant habit. First year plants, some less than 10 cm high, with yellow flowers and beginning to set fruit. Plants growing with Carex maritima in dry gravel. Nunavut, Rankin Inlet. 27 July, 2001. Aiken and Brysting 01–047. CAN. • Close-up of flowers. Small flowers with yellow calyx and petals. The sepals are wider than the thin petals and remain on the receptacle longer. Nunavut, Rankin Inlet. 27 July, 2001. Aiken and Brysting 01–047. CAN. • Close-up of fruits. Fruits developing along the racemose inflorescence. The siliques are much longer than wide. The outline of several developing seeds is seen in the lowest silique. Nunavut, Rankin Inlet. 27 July, 2001. Aiken and Brysting 01–047. CAN. • Herbarium specimen. Plant with lacy, pinnately divided leaves, the margins of the divisions are dentate which contributes to the lacy appearance of the leaf. N.W.T., Victoria Island, Minto Inlet. 10 July, 1983. S.A. Edlund 106. CAN 484857. • Arctic Island Distribution.


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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