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''Spirodela'' is a genus of aquatic plant. It is one of several genera containing plants commonly called duckweed. ''Spirodela'' species are members of the Araceae under the APG II system. They were formerly members of the Lemnaceae.〔Govaerts, R. & Frodin, D.G. (2002). World Checklist and Bibliography of Araceae (and Acoraceae): 1-560. The Board of Trustees of the Royal Botanic Gardens, Kew. 〕〔Landolt, E. (1986) Biosystematic investigations in the family of duckweeds (Lemnaceae). Vol. 2. The family of Lemnaceae - A monographic study. Part 1 of the monograph: Morphology; karyology; ecology; geographic distribution; systematic position; nomenclature; descriptions. Veröff. Geobot. Inst., Stiftung Rübel, ETH, Zurich.〕 ''Spirodela'' species are free-floating thalli, 2-5 plants may remain connected to each other. Plants are green, but may have a red or brown underside. Multiple roots (7 to 12) emerge from each thallus. ''Spirodela'' is larger (10 mm) than ''Lemna'' (2–5 mm, one root per thallus).〔 Certain species of ''Spirodela'' overwinter as turions, a dormant form that lacks air pockets and so sinks to the bottom of the pond. In spring turions rise to the surface and germinate to start a new population. ''Spirodela'' often forms floating mats with related species, e.g. ''Lemna'' and Wolffia. The genus is virtually cosmopolitan in distribution.〔(Kew World Checklist of Selected Plant Families )〕〔(Flora of North America )〕 ''Spirodela punctata'' is sometimes treated as ''Landoltia punctata''.〔Les, D. H. and D. J. Crawford. 1999. ''Landoltia'' (Lemnaceae), a new genus of duckweeds. ''Novon'' 9: 530-533.〕 ==Species== # ''Spirodela oligorrhiza'' (Kurz) Hegelm. - Africa, Australia, southern Asia # ''Spirodela polyrrhiza'' (L.) Schleid. - cosmopolitan # ''Spirodela punctata'' (G.Mey.) C.H.Thomps. - South America, Central America, West Indies # ''Spirodela sichuanensis'' M.G.Liu & K.M.Xie - southern China 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spirodela」の詳細全文を読む スポンサード リンク
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