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| Potamogeton amplifolius
Tuckerman |
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| TAXONOMY |
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| Family: |
Potamogetonaceae |
| Genus: |
Potamogeton |
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| Species Synonyms: |
none |
| Common Names: |
largeleaf pondweed
broad-leaved pondweed |
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| DISTRIBUTION |
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| Canada: |
south-central British Columbia, central Saskatchewan
– Manitoba – Ontario – Quebec – Newfoundland –
Nova Scotia |
| Saskatchewan: |
central Saskatchewan; Prince Albert National Park
– Churchill River |
| Ecoregion: |
Mid-Boreal Upland, Churchill River Upland |
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| HABITAT |
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| Saskatchewan: |
in shallow quiet water of protected lake bays,
ponds, and slow-moving streams |
| Canada: |
lakes and streams |
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| RARITY STATUS |
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Provincial
Status According
to Harms (2003): |
Endangered |
| Nature Conservancy
Status: |
G5 S1 |
Saskatchewan
Species at
Risk Status: |
None |
| COSEWIC Status:
|
None |
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| Largeleaf pondweed
is endangered because of extreme rarity in Saskatchewan. No immediate threats
are known but may occur in the future. |
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| SPECIES
DESCRIPTION |
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| Height: |
6 – 100 cm |
| Roots: |
roots fibrous; rhizomes present |
| Stems: |
round, often rusty spotted |
| Leaves: |
both submersed and floating, floating leaves may
be absent; submersed leaves 5 – 12 cm long, 1.5 – 6 cm wide,
oval to inversely lance-shaped, base rounded to acute, not clasping, lax,
light to dark green, veins 20 – 50, margin entire; stipular sheaths
persistent, conspicuous, free from the base of the leaf blade, light brown,
not fibrous or shredding at tip; petioles to 6 cm long, round; floating
leaves stalked, 4 – 9 cm long, 2.5 – 4 cm wide, lance-shaped
to elliptic, base rounded to heart-shaped, veins 27 – 50 |
| Inflorescence: |
spikes terminal or axillary, erect, 3.5 –
8 cm long, cylindrical, uniform, floating; inflorescence stalks uniform |
| Flowers: |
small, greenish; tepals 4; stamens 4; ovaries
4 |
| Fruits: |
single-seeded, sessile, reddish-brown, with a
prominent central beak |
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| POTAMOGETON
KEY FOR SPECIES FOUND IN SASKATCHEWAN |
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| 1 Stipular sheaths of submersed leaves
fused 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 lance-shaped
to nearly round
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3 |
| 2 Submersed leaves ribbon-like or
thread-like |
9 |
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| 3 Leaf margins conspicuously saw-toothed
and wavy; overwintering stems present |
P. crispus |
| 3 Leaf margins entire or wavy; overwintering
stems absent |
4 |
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| 4 Submersed leaves clasping; floating
leaves absent |
5 |
| 4 Submersed leaves not clasping, may
be stalked; 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 heart-shaped;
stem rusty or black-spotted; submersed leaves arced |
P. amplifolius |
| 6 Floating leaf blade wedge-shaped
or rounded; stems without spots; submersed leaves not arced |
7 |
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| 7 Submersed leaves stalked |
P. nodosus |
| 7 Submersed leaves sessile |
8 |
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| 8 Fruits plump, stalked; submersed
leaf blade 7 – 9-veined |
P. alpinus |
| 8 Fruits compressed, not stalked;
submersed leaf blade 3 – 19-veined |
P. gramineus |
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| 9 Floating leaves present on at least
come plants in a population |
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| 9 Floating leaves absent |
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| 10 Air spaces in leaf tissue present
and prominent; submersed leaves with distinction between blade and stalk;
leaves of two types, the floating ones long-stalked and wider than the submersed
ones |
P. epihydrus |
| 10 Air spaces in leaf tissue absent
or not prominent; blade and petiole not well-differentiated on submersed
leaves; 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 tip tapered to pointed, leaves
thin, 5 -7-nerved; inflorescence stalks at most 5 cm long |
P. friesii |
| 14 Leaf tip bristle-tipped; leaves
firm, 3-nerved; inflorescence stalks 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 widest at the top;
inflorescence stalks 1 – 3 per plant; leaf blade with less than 2
rows of air spaces along midrib |
P. pusillus ssp. pusillus |
| 16 Mature fruits widest at the middle;
inflorescence stalks more than 3 per plant; leaf blade with 1 – 5
rows of air spaces along midrib |
P. pusillus ssp. tenuissimus |
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