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''Helenium amarum'' is a species of annual herb in the daisy family known by the common names yellowdicks, yellow sneezeweed, fiveleaf sneezeweed, and bitter sneezeweed. It is native to much of the south-central United States (Texas, Oklahoma, Louisiana, New Mexico)〔 and northern Mexico (Chihuahua, Coahuila),〔 and it is present elsewhere in North America, Australia, and the West Indies as an introduced species.〔(Biota of North America Program 2014 county distribution map )〕〔Turner, B. L. 2013. The comps of Mexico. A systematic account of the family Asteraceae (chapter 11: tribe Helenieae). Phytologia Memoirs 16: 1–100. 〕〔(Tropicos, specimen listing for ''Helenium amarum'' (Raf.) H. Rock )〕〔(Queensland Government, Department of Agriculture and Fisheries, Bitter weed ''(Helenium amarum)'' )〕 ''Helenium amarum'' is a multibranched bushy erect plant reaching 20 to 70 centimeters (8-28 inches) in height and thickly foliated in narrow to threadlike leaves. The tops of stem branches hold inflorescences of many daisy-like flower heads. Each head has a rounded center of sometimes as many as 250 golden yellow disc florets and a fringe of 8-10 usually lighter yellow ray florets which are reflexed away from the center. The fruit is a tiny achene about a millimeter long. This herb is weedy in some areas.〔(Flora of North America, ''Helenium amarum'' (Rafinesque) H. Rock, 1957. Yellowdicks, fiveleaf sneezeweed )〕 The plant is somewhat toxic to mammals〔Ivie, G. W., et al. (1975). Toxicity and milk bittering properties of tenulin, the major sesquiterpene lactone constituent of ''Helenium amarum'' (bitter sneezeweed). ''J Agric Food Chem'' 23:5 845-9.〕 and insects〔Arnason, J. T., et al. (1987). Mode of action of the sesquiterpene lactone, tenulin, from ''Helenium amarum'' against herbivorous insects. ''J Nat Prod'' 50:4 690-5.〕 due to the presence of the lactone tenulin. ;Varieties〔〔 *''Helenium amarum'' var. ''amarum'' - United States *''Helenium amarum'' var. ''badium'' Waterf. - Oklahoma, Texas, Chihuahua, Coahuila ==References== 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「Helenium amarum」の詳細全文を読む スポンサード リンク
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