Acorus

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Acorus is a genus of monocot flowering plants. This genus was once placed within the family Araceae (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, and naturalised in southern Asia and Europe from ancient cultivation.[1]Template:R/superscript[2]Template:R/superscript[3]Template:R/superscript[4]Template:R/superscript[5]Template:R/superscript[6]Template:R/superscript The known wild populations are diploid 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

File:Acorus calamus1.jpg
Habit of Acorus calamus.

The inconspicuous flowers 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 family has recently been resurrected as molecular systematic studies have shown that Acorus is not closely related to Araceae or any other monocot 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 to all other monocots. This relationship is confirmed by more recent phylogenetic studies.Script error: No such module "Footnotes".Script error: No such module "Check for unknown parameters".Script error: No such module "Footnotes".Script error: No such module "Check for unknown parameters". Treatment in the APG IV system is unchanged from APG III.[7]Template:R/superscript

Species

In older literature and on many websites, there is still much confusion, with the name Acorus calamus equally but wrongly applied to Acorus americanus (formerly Acorus calamus var. americanus).

The Kew Checklist accepts 4 species within the genus Acorus:[1]Template:R/superscript

Acorus from Kazakhstan, Europe, China and Japan have been planted in the United States.

Etymology

The name 'acorus' is derived from the Greek word 'acoron', a name used by Dioscorides, which in turn was derived from 'coreon', meaning 'pupil', because it was used in herbal medicine as a treatment for inflammation of the eye.Script error: No such module "Unsubst".

Distribution and habitat

These plants are found in wetlands, particularly marshes, where they spread by means of thick rhizomes. Like many other marsh plants, they depend upon aerenchyma to transport oxygen to the rooting zone.[12]Template:R/superscript 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.[13]Template:R/superscript Although many marsh plants accumulate large banks of buried seeds,[14]Template:R/superscript seed banks of Acorus may not accumulate in some wetlands owing to low seed production.[15]Template:R/superscript 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.[16]Template:R/superscript 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.[17]Template:R/superscript

Toxicity

File:Acorus calamus illustration.jpg
Sweet Flag (2006 drawing by USGS Northern Prairie Wildlife Research Center)

Products derived from Acorus calamus were banned in 1968 as food additives by the United States Food and Drug Administration.[18]Template:R/superscript The primary chemical responsible for the plant's toxic and carcinogenic effects is 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.[19]Template:R/superscript 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.[20]Template:R/superscript 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.[21]Template:R/superscript[22]Template:R/superscript[23]Template:R/superscript Research has consistently demonstrated that "β-asarone was not detectable in the North American spontaneous diploid Acorus [calamus var. americanus]".[24]Template:R/superscript

Uses

The parallel-veined leaves of some species contain ethereal oils that give a sweet scent when dried.Script error: No such module "Unsubst". Fine-cut leaves used to be strewn across the floor in the Middle Ages, both for the scent, and for presumed efficacy against pests.Script error: No such module "Unsubst".

References

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  1. ↑ a b Template:Cite POWO
  2. ↑ Flora of North America: Acorus
  3. ↑ Flora of China, Vol. 23 Page 1, 菖蒲属 chang pu shu, Acorus Linnaeus, Sp. Pl. 1: 324. 1753.
  4. ↑ 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.
  5. ↑ Boyce, P.C., Sookchaloem, D., Hetterscheid, W.L.A., Gusman, G., Jacobsen, N., Idei, T. & Nguyen, V.D. (2012). Flora of Thailand 11(2): 101–325. The Forest Herbarium, National Park, Wildlife and Plant Conservation Department, Bangkok.
  6. ↑ Nooteboom, H.P. (ed.) (2011). Flora Malesiana 20: 1–61. Noordhoff-Kolff N.V., Djakarta.
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ Template:Cite POWO
  9. ↑ Template:Cite POWO
  10. ↑ Template:Cite POWO
  11. ↑ Template:Cite POWO
  12. ↑ Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. Chapter 1.
  13. ↑ Script error: No such module "Citation/CS1". Figure 1.
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Script error: No such module "Citation/CS1". Appendix 3.
  17. ↑ Script error: No such module "Citation/CS1". Figure 2
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ Ginwal, HS, An efficient genomic DNA isolation protocol for RAPD and SSR analysis in Template:Tx
  20. ↑ Evstatieva et al., Fitologiya 48: 19–22. 1996; Löve & Löve, Proc. Genet. Soc. Canada 2: 14–17. 1957
  21. ↑ Script error: No such module "Citation/CS1".
  22. ↑ (Rost and Bos, 1979)
  23. ↑ Antimicrobial activities of the crude methanol extract of Acorus calamus Linn., S Phongpaichit, N Pujenjob, J. Songklanakarin
  24. ↑ Script error: No such module "Citation/CS1".
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Bibliography

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