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| Potamogeton obtusifolius
Mert. & Kock |
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| TAXONOMY |
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| Family: |
Potamogetonaceae |
| Genus: |
Potamogeton |
| |
| Species Synonyms: |
none |
| Common Names: |
bluntleaf pondweed |
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| DISTRIBUTION |
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| Canada: |
south-central Yukon, southwestern British Columbia,
Alberta – Saskatchewan – northern Manitoba – Ontario –
Quebec – Newfoundland – Nova Scotia |
| Saskatchewan: |
northern to south-central Saskatchewan; Lake Athabasca
– Clearwater River – Deschambault Lake – Chelan |
| Ecoregion: |
Moist Mixed Grassland, Boreal Transition, Mid-Boreal
Upland, Mid-Boreal Lowland, Churchill River Upland, Tazin Lake Upland |
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| HABITAT |
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| Saskatchewan: |
in shallow water of protected lake bays, ponds,
and quiet streams |
| Canada: |
cold streams and lakes |
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| RARITY STATUS |
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Provincial
Status According
to Harms (2003): |
Endangered |
| Nature Conservancy
Status: |
G5 S2 |
Saskatchewan
Species at
Risk Status: |
None |
| COSEWIC Status:
|
None |
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| Potamogeton
obtusifolius is threatened because it is rare or uncommon in Saskatchewan.
No threats are known or anticipated for this species. |
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| SPECIES
DESCRIPTION |
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| Height: |
35 – 90 cm |
| Roots: |
roots fibrous; rhizomes absent |
| Stems: |
branched, slightly compressed, slender, without
spots, glands at nodes yellow-green to gold; turions terminal, abundant,
soft |
| Leaves: |
submersed, spirally arranged, sessile, flaccid,
3 – 8 cm long, 1 – 4 mm wide, base not lobed, apex rounded or
apiculate, light green to reddish, lacunae septate and in 1 – 3 rows
on each side of midrib, veins 3, margin entire; stipules persistent, 1 –
2 cm long, convolute, free from blade, fibrous |
| Inflorescence: |
spike emersed, 8 – 15 mm long; peduncles
1 – 4 cm long, uniform, erect, cylindrical |
| Flowers: |
small, greenish; tepals 4; stamens 4; carpels
4 |
| Fruits: |
sessile, olive-green to brown, may be keeled,
beak short |
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| POTAMOGETON
KEY FOR SPECIES FOUND IN SASKATCHEWAN |
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| 1 Stipular sheaths of submersed leaves
adnate to base of leaf blade; leaf margins cartilaginous |
P. robbinsii |
| 1 Stipular sheaths of submersed leaves
free from base of leaf blade; leaf margins not cartilaginous |
2 |
| |
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2 Submersed leaves oblong to lanceolate
to nearly orbicular
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3 |
| 2 Submersed leaves ribbon-like or
thread-like |
9 |
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| 3 Leaf margins conspicuously serrate
and undulate; turions present |
P. crispus |
| 3 Leaf margins entire or undulate;
turions absent |
4 |
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| 4 Submersed leaves clasping; floating
leaves absent |
5 |
| 4 Submersed leaves not clasping, may
be petiolate; floating leaves present or absent |
6 |
| |
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| 5 Stipules persistent; rhizome with
rusty spots |
P. praelongus |
| 5 Stipules shredding into fibres;
rhizome not obviously spotted |
P. richardsonii |
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| 6 Floating leaf blade rounded to cordate;
stem rusty or black-spotted; submersed leaves arcuate |
P. amplifolius |
| 6 Floating leaf blade cuneate or rounded;
stems without spots; submersed leaves not arcuate |
7 |
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| 7 Submersed leaves petiolate |
P. nodosus |
| 7 Submersed leaves sessile |
8 |
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| 8 Fruits plump, pedicellate; submersed
leaf blade 7 – 9-veined |
P. alpinus |
| 8 Fruits compressed, sessile; submersed
leaf blade 3 – 19-veined |
P. gramineus |
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| 9 Floating leaves present on at least
some plants in a population |
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| 9 Floating leaves absent |
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| 10 Lacunae present and prominent;
submersed leaves with distinction between blade and petiole; leaves dimorphic,
the floating ones long-petioled and wider than the submersed ones |
P. epihydrus |
| 10 Lacunae absent or not prominent;
submersed leaves phyllodial; leaves uniform, no distinction between the
floating and submersed leaves |
P. natans |
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| 11 Nodes without glands |
12 |
| 11 Nodes glandular |
13 |
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| 12 Leaves 15 – 35-veined, greater
than 2 mm wide; stem wing-flattened |
P. zosteriformis |
| 12 Leaves 3 – 5-veined, less
than 2 mm wide; stem not wing-flattened |
P. foliosus ssp. foliosus |
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| 13 Stipules fibrous, whitish |
14 |
| 13 Stipules not fibrous, green, brown
or whitish |
15 |
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| 14 Leaf apex acute to apiculate, leaves
thin, 5 – 7-nerved; peduncles at most 5 cm long |
P. friesii |
| 14 Leaf apex bristle-tipped; leaves
firm, 3-nerved; peduncles to 9 cm long |
P. strictifolius |
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| 15 Fruits 2.5 – 3.5 mm long |
P. obtusifolius |
| 15 Fruits 1.5 – 2 mm long |
16 |
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| 16 Mature fruits obovoid; peduncles
1 – 3 per plant; leaf blade with less than 2 rows of lacunae along
midrib |
P. pusillus ssp. pusillus |
| 16 Mature fruits widest at the middle;
peduncles more than 3 per plant; leaf blade with 1 – 5 rows of lacunae
along midrib |
P. pusillus ssp. tenuissimus |
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