Comments
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Pistillate flowers in distal to proximal axils, 2.2 mm; styles 1--1.2 mm; stigmas 2-lobed. Seeds slightly recurved, purplish, fusiform, 1.5--3 ´ 0.5--0.7 mm, apex with style situated at center; testa dull, 3 cell layers thick, pitted; aeroleareoles regularly arranged in ca. 15 longitudinal rows, ladderlike, 4-angled, broader than long, end walls not raised. 2n = 24.
Najas minor, with its mature leaves recurved and with its aeroleareoles broader than long and arranged in longitudinal rows like the rungs of a ladder, is one of the more distinctive species of Najas. Young sterile individuals resemble N. gracillima, however.
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Description
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Monoecious, dark green; stem lip to 25-30 cm long and up to 1 mm broad, profusely branched particularly in upper part, intemodes without spines. Leaves linear, 15-40 x 0.7-1.5 mm, serrulate to spinose-dentate with 7-25 teeth on each side, apex acute with 1-2 teeth, sometimes with some spines on the back of the midrib. Sheath 1.5-3 mm long as well as broad, short rounded-truncate or spinulose, with 5-8 teeth on each side. Male flowers: solitary, enclosed in a spathe, neck conical or cylindrical, anther 1-thecous. Female flower without spathe, often 2-3 together, style with 2-stigmas. Seeds slightly recurved at apex; areoles broader than long and arranged ladder like.
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Description
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Stems profusely branched near apex distally, 11--120 cm ´ 0.2--1 mm; internodes 0.5--5.8 cm, without prickles abaxially. Leaves usually recurved with age, 0.5--3.4 cm, stiff in age; sheath 1--3 mm wide, apex truncate to auriculate; blade 0.1--1.2 mm wide, margins conspicuously serrulate, teeth 7--15 per side, apex acute, with 1--2 teeth, teeth multicellular; midvein without prickles abaxially. Flowers 1--2 per axil, staminate and pistillate on same plant. Staminate flowers in distal axils, 1.9--2.2 mm; involucre 2-lobed, beaks 0.4--2.1 mm; anther 1-loculed, 0.3 mm.
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Distribution
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Throughout the Old World.
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Distribution
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Distribution: Europe to Asia through Africa, America (wide spread).
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Distribution
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introduced; Ala., Del., Fla., Ga., Ill., Ind., Ky., La., Mass., Mich., Miss., Mo., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Vt., Va., W.Va.; Eurasia; Africa.
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Elevation Range
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700 m
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Flower/Fruit
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Fl. Per.: March-September.
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Flowering/Fruiting
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Flowering summer--fall.
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Habitat
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Ponds, lakes, and slow- moving streams; 0--500m.
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Najas minor
provided by wikipedia EN
Najas minor, known as brittle naiad or brittle waternymph,[2] is an annual aquatic plant, a submersed herb. It is native to Europe, Asia and North Africa from the Netherlands to Morocco east to Japan and the Philippines, including China, Siberia, Central Asia, Iran, Turkey, Ukraine, Germany, France Italy and a host of other countries.[3] It is now introduced to North America and considered a weedy invasive species in the eastern half of the United States from Florida to Oklahoma to New Hampshire to Ontario to South Dakota.[4] This plant prefers calm waters, such as ponds, reservoirs, and lakes, and is capable of growing in depths up to 4 meters.
Identification
Najas minor grows in dense clusters and has highly branched stems. These stems fragment easily and this plant is capable of propagation from stem fragments or from small seeds which grow along its stem. The small flowers are located in clusters along the leaf axils. The leaves of the plant are opposite, unbranched, strap-shaped, and are around 4.5 centimeters in length. The leaves have serrations which are visible to the naked eye. This plant is similar in morphology to coontail or slender naiad.[5][6][7]
Distribution
Najas minor is distributed widely in the Northern Hemisphere, such as Canada, the United States, Japan, China, Europe.[8] This species is also reported from tropical Asia (Thailand),[9] but the report is now recognized as an identification error.[10]
Invasive spread and control
Brittle naiad was introduced to the United States, where it is considered an invasive species or noxious weed, in the 1900s. Brittle naiad in the United States is established in the Mid-Atlantic States. Established populations are found as far west as Oklahoma and Ontario, Canada in the north. The presence of this plant is a problem because its dense growth covers wide areas, inhibiting the growth of native species of aquatic macrophytes. The thick, clustering growths of brittle naiad can make fishing access or the operation of a boat difficult in a pond or lake. Brittle naiad may spread to new areas by stem fragments carried on a boat's hull, deck, propeller, or trailer. Control measures for brittle naiad include the use of aquatic herbicides, but application of chemicals may not destroy the seeds. Grass carp are another widely used control measure and have been known to readily consume brittle naiad plants. Mechanical harvesting of brittle naiad is difficult, as the brittle stems readily break and are easily disbursed throughout the system. As with most invasive species, prevention of an infestation is easier than eradication.
References
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^ The Plant List
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^ USDA, NRCS (n.d.). "Najas minor". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 16 July 2015.
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^ "World Checklist of Selected Plant Families: Royal Botanic Gardens, Kew". apps.kew.org. Retrieved 2017-01-31.
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^ Biota of North America Project, Najas minor
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^ Carlo Allioni. 1773. Auctarium ad Synopsim Methodicam Stirpium Horti Reg. Taurinensis 3, Najas minor
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^ Carlo Allioni. 1774. Mélanges Philos. Mat. Soc. Roy. Turin 5: 55, Najas minor
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^ N.Z.Wang. 1985. Journal of Wuhan Botanical Research 3(1): 31, Najas moshanensis
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^ Haynes, R.R. 2000. Najadaceae. pp. 77–83. In: Flora of North America Editorial Committee (eds), Flora of North America north of Mexico, Vol. 22, Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford University Press, New York, NY, USA.
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^ Haynes, R.R. 2001. Hydrocharitaceae. In: T. Santisuk & K. Larsen (eds), Flora of Thailand 7: 365–382. The Forest Herbarium, Royal Forest Department. Bangkok.
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^ Ito, Y. (2016) Taxonomic notes on the genus Najas (Hydrocharitaceae) in Thailand: addition of N. marina and exclusion of N. minor. Thai Forest Bulletin 44: 104-107. doi: 10.20531/TFB.2016.44.2.03
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Najas minor: Brief Summary
provided by wikipedia EN
Najas minor, known as brittle naiad or brittle waternymph, is an annual aquatic plant, a submersed herb. It is native to Europe, Asia and North Africa from the Netherlands to Morocco east to Japan and the Philippines, including China, Siberia, Central Asia, Iran, Turkey, Ukraine, Germany, France Italy and a host of other countries. It is now introduced to North America and considered a weedy invasive species in the eastern half of the United States from Florida to Oklahoma to New Hampshire to Ontario to South Dakota. This plant prefers calm waters, such as ponds, reservoirs, and lakes, and is capable of growing in depths up to 4 meters.
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