''Acorus'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
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 on ...
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...
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). ...
(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, and several families of aquatic monocots (e.g., Alismataceae,
Posidoniaceae). However, modern phylogenetic studies demonstrate that ''Acorus'' is
sister to all other monocots. Common names include calamus and
sweet flag.
The genus is native to
North America 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 ...
, 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 in ...
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 subcontinent of Eurasia and it is located enti ...
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, respecti ...
except for some
tetraploids in eastern Asia, while the cultivated plants are sterile
triploids, probably of
hybrid 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 mechanism ...
s are arranged on a lateral
spadix (a thickened, fleshy axis). Unlike aroids, there is no
spathe (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 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) ...
. 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 on ...
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
APG III 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 ...
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 publish ...
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''
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 subcontinent of Eurasia and it is located enti ...
, 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 ...
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 10 ...
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 ...
, 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''
Raf. - Canada, northern United States, Buryatiya region of Russia
* ''
Acorus gramineus''
Sol. ex Aiton Aiton may refer to:
People
*Aiton (surname)
*Standard author abbreviation of William Aiton (1731 – 1793), Scottish botanist
Places
* Aiton, Cluj, a commune in Romania
* Aiton, Savoie, a commune in France
Other uses
* Tai Aiton people, one of ...
– Japanese sweet flag or grassy-leaved sweet flag; fertile diploid (2''n'' = 18); - China, Himalayas, Japan, Korea, Indochina, Philippines, Primorye
''Acorus'' from Europe,
China 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 U.S. state, states, a Washington, D.C., federal district, five ma ...
.
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-vo ...
, which in turn was derived from 'coreon', meaning 'pupil', because it was used in
herbal medicine 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
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...
.
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 '' Iri ...
''.
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 federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
. 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
pest
Pest or The Pest may refer to:
Science and medicine
* Pest (organism), an animal or plant deemed to be detrimental to humans or human concerns
** Weed, a plant considered undesirable
* Infectious disease, an illness resulting from an infection
** ...
s.
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: Acoraceaein Stevens, P. F. (2001 onwards)
Angiosperm Phylogeny Website Version 7, May 2006.
NCBI Taxonomy Browserin 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