Acoraceae
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''Acorus'' is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s. This genus was once placed within the family
Araceae The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). Also ...
(aroids), but more recent classifications place it in its own family Acoraceae and order Acorales, of which it is the sole genus of the oldest surviving line of monocots. Some older studies indicated that it was placed in a lineage (the order Alismatales), that also includes aroids (Araceae),
Tofieldiaceae Tofieldiaceae is a family of flowering plants in the monocot order Alismatales.Vernon H. Heywood, Richard K. Brummitt, Ole Seberg, and Alastair Culham. ''Flowering Plant Families of the World''. Firefly Books: Ontario, Canada. (2007). . The fami ...
, and several families of aquatic monocots (e.g., Alismataceae,
Posidoniaceae ''Posidonia'' is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia. The APG system (1998) and APG II system (2003) accept this gen ...
). However, modern phylogenetic studies demonstrate that ''Acorus'' is
sister A sister is a woman or a girl who shares one or more parents with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to refer to ...
to all other monocots. Common names include calamus and sweet flag. The genus is native to
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
and northern and eastern
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
, and
naturalised Naturalization (or naturalisation) is the legal act or process by which a non-citizen of a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the i ...
in southern Asia and
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
from ancient cultivation. The known wild populations are
diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
except for some
tetraploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...
s in eastern Asia, while the cultivated plants are sterile
triploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei ( eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contain ...
s, probably of
hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...
origin between the diploid and tetraploid forms.


Characteristics

The inconspicuous
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s are arranged on a lateral spadix (a thickened, fleshy axis). Unlike aroids, there is no
spathe In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...
(large bract, enclosing the spadix). The spadix is 4–10 cm long and is enclosed by the foliage. The bract can be ten times longer than the spadix. The
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
are linear with entire margin.


Taxonomy

Although the family Acoraceae was originally described in 1820, since then ''Acorus'' has traditionally been included in Araceae in most classification systems, as in the
Cronquist system The Cronquist system is a taxonomic classification system of flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including ''The Evolution and Classification of Flowering Plants'' (1968; 2nd edition, 1988) a ...
. The family has recently been resurrected as molecular systematic studies have shown that ''Acorus'' is not closely related to Araceae or any other
monocot Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...
family, leading plant systematists to place the genus and family in its own order. This placement currently lacks support from traditional plant morphology studies, and some taxonomists still place it as a subfamily of Araceae, in the order
Alismatales The Alismatales (alismatids) are an order of flowering plants including about 4,500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Description The Alismatales compri ...
. The
APG III APG is an abbreviation with several different meanings: * Aberdeen Proving Ground, a United States Army installation in Aberdeen, Maryland, also ** Phillips Army Airfield, the airfield of the above, from its IATA airport code * Aboriginal Provisiona ...
system recognizes order Acorales, distinct from the Alismatales, and as the
sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...
to all other monocots. This relationship is confirmed by more recent phylogenetic studies. Treatment in the
APG IV system The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published ...
is unchanged from APG III.


Species

In older literature and on many websites, there is still much confusion, with the name ''Acorus calamus'' equally but wrongfully applied to ''Acorus americanus'' (formerly ''Acorus calamus'' var. ''americanus''). As of July 2014, the Kew Checklist accepts only 2 species, one of which has three accepted varieties: * ''
Acorus calamus ''Acorus calamus'' (also called sweet flag, sway or muskrat root, among many common names) is a species of flowering plant with psychoactive chemicals. It is a tall wetland monocot of the family Acoraceae, in the genus ''Acorus.'' Although us ...
'' L. – Common sweet flag; sterile triploid (3''n'' = 36); probably of cultivated origin. It is native to
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, temperate
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
and the
Himalaya The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 100 ...
s and southern
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
, widely cultivated and naturalised elsewhere. **''Acorus calamus'' var. ''angustatus'' Besser - Siberia, China, Russian Far East, Japan, Korea, Mongolia, Himalayas, Indian Subcontinent, Indochina, Philippines, Indonesia **''Acorus calamus'' var. ''calamus'' - Siberia, Russian Far east, Mongolia, Manchuria, Korea, Himalayas; naturalized in Europe, North America, Java and New Guinea *''
Acorus americanus ''Acorus americanus'', the American sweet flag, is an emergent wetland plant native to the northern United States and Canada. This perennial plant has bright green blade-shaped leaves that arise directly from the rhizomes and sheath into each ot ...
'' Raf. - Canada, northern United States, Buryatiya region of Russia * '' Acorus gramineus''
Sol. Daniel Carlsson Solander or Daniel Charles Solander (19 February 1733 – 13 May 1782) was a Swedish naturalist and an apostle of Carl Linnaeus. Solander was the first university-educated scientist to set foot on Australian soil. Biography ...
ex Aiton
– Japanese sweet flag or grassy-leaved sweet flag; fertile diploid (2''n'' = 18); - China, Himalayas, Japan, Korea, Indochina, Philippines, Primorye ''Acorus'' from Europe,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
and Japan have been planted in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
.


Etymology

The name 'acorus' is derived from the Greek word 'acoron', a name used by
Dioscorides Pedanius Dioscorides ( grc-gre, Πεδάνιος Διοσκουρίδης, ; 40–90 AD), “the father of pharmacognosy”, was a Greek physician, pharmacologist, botanist, and author of ''De materia medica'' (, On Medical Material) —a 5-vol ...
, which in turn was derived from 'coreon', meaning 'pupil', because it was used in
herbal medicine Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remed ...
as a treatment for
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
of the eye.


Distribution and habitat

These plants are found in
wetlands A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
, particularly marshes, where they spread by means of thick rhizomes. Like many other marsh plants, they depend upon
aerenchyma Aerenchyma or aeriferous parenchyma or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and t ...
to transport oxygen to the rooting zone. They frequently occur on shorelines and floodplains where water levels fluctuate seasonally.


Ecology

The native North American species appears in many ecological studies. Compared to other species of wetland plants, they have relatively high competitive ability. Although many marsh plants accumulate large banks of buried seeds, seed banks of ''Acorus'' may not accumulate in some wetlands owing to low seed production. The seeds appear to be adapted to germinate in clearings; after a period of cold storage, the seeds will germinate after seven days of light with fluctuating temperature, and somewhat longer under constant temperature. A comparative study of its life history traits classified it as a "tussock interstitial", that is, a species that has a dense growth form and tends to occupy gaps in marsh vegetation, not unlike ''
Iris versicolor ''Iris versicolor'' is also commonly known as the blue flag, harlequin blueflag, larger blue flag, northern blue flag, and poison flag, plus other variations of these names, and in Britain and Ireland as purple iris. It is a species of ''Iris'' ...
''.


Toxicity

Products derived from ''Acorus calamus'' were banned in 1968 as food additives by the United States
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
. The questionable chemical derived from the plant was β-asarone. Confusion exists whether all strains of ''A. calamus'' contain this substance. Four varieties of ''A. calamus'' strains exist in nature: diploid, triploid, tetraploid and hexaploid. Diploids do not produce the carcinogenic β-asarone. Diploids are known to grow naturally in Eastern Asia (Mongolia and C Siberia) and North America. The triploid cytotype probably originated in the Himalayan region, as a hybrid between the diploid and tetraploid cytotypes. The North American Calamus is known as ''Acorus calamus'' var. ''americanus'' or more recently as simply ''Acorus americanus''. Like the diploid strains of ''A. calamus'' in parts of the Himalayas, Mongolia, and C Siberia, the North American diploid strain does not contain the carcinogenic β-asarone. Research has consistently demonstrated that "β-asarone was not detectable in the North American spontaneous diploid Acorus alamus var. Americanus.


Uses

The parallel-veined leaves of some species contain ethereal oils that give a sweet scent when dried. Fine-cut leaves used to be strewn across the floor in the Middle Ages, both for the scent, and for presumed efficacy against pests.


References


Bibliography

* 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.
Flora of North America: Acoraceae


in Stevens, P. F. (2001 onwards)
Angiosperm Phylogeny Website
Version 7, May 2006.
NCBI Taxonomy Browser


in L. Watson and M.J. Dallwitz (1992 onwards)
The families of flowering plants:
descriptions, illustrations, identification, information retrieval''. Version: 27 April 2006. http://delta-intkey.com.
Taxonomy and distribution of Acorus in Maine



Phylogenetic analysis of rbcL sequences identifies Acorus calamus as the primal extant monocotyledon. Duvall 1993
*
Analysis of Acorus calamus Chloroplast Genome and Its Phylogenetic Implications Vadim V. Goremykin 2005
* * {{taxonbar, from1=Q160087, from2=Q637337, from3=Q2022672 Acorales Monocot genera Absinthe Edible plants Freshwater plants