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Dictionary Definition

stonewort n : any of various submerged aquatic algae of the genus Chara having nodes with whorled filamentlike branches; usually encrusted with calcium carbonate deposits

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English

Noun

  1. Any of various complex algae of the family Characeae, known for being branched and having enclosed egg cells.

See also

Extensive Definition

The Charales are in the division Charophyta. They are green plants believed to be the closest relatives of the green land plants. Linnaeus established the genus (Chara) in 1753.

Description

The Charales, have large, macroscopic, thalli growing up to 120cm long, they are branched, multicellular, and use chlorophyll to photosynthesize. They grow in fresh water. They may be called stoneworts, because the plants can become encrusted in lime (calcium carbonate) after some time. The "stem" is actually a central stalk consisting of giant, multinucleated cells. They are unique in having a whorl of small branchlets at each node in the stipe, this gives them a superficial resemblance to the genus Equisetum. In these whorls it is possible to see the phenomenon of cytoplasmic streaming very well. In fact the streaming in Chara is the fastest recorded of any cell. Cytoplasmic streaming is caused by the microfilaments found inside the cell, as proven by the use of cytochalasin B to stop streaming. There are about 400 species world-wide, with 33 in Britain and Ireland according to Groves and Bullock-Webster), however (Stewart and Church (1992) reduce this to 21.

Species

British Isles

Ref: Stewart & Church (1992).

Distribution

(due for further enlargement)

Ireland

Co. Antrim
C.aspera Deth. ex Willd. var. aspera
C. globularis Thuill. var. globularis
C. vulgaris var. papillata Wallr. ex A. Braun
C. globularis var. virgata (Kützing) R.D.Wood
C. vulgaris L. var. vulgaris
C. vulgaris L. var. contraria (A.Braun ex Kützing) J.A. Moore
C. vulgaris var. longibracteata (Kützing) J. Groves & Bullock-Webster
C. vulgaris var. papillata Wallr. ex A. Braun
Nitella flexilis (L.) var. flexilis
Nitella translucens (Pers.) C.A. Ag.
Tolypella nidifica (O. Mill.) Leonh. var. glomerata (Desv.) R.D.Wood
Co. Down
C. virgata Kützing
N. flexilis (Linnaeus) C.Agardh
N. translucens (Persoon) C.Agardh

Ecology

The Characeae are aquatic though some can survive in brackish or maritime habitats. They are to be found usually in still, non-flowing, water attached by rhizoids. They can be pioneer colonizers or ephemerals.

Life history

The antheridia and oogonia are protected by a layer of sterile cells when mature; the oogonium is oblong in shape and consists of a single egg, while the spherical antheridium is packed with threadlike cells that produce spermatia. As a result, the Charales have the most complex structure of all green algae, if indeed they should be so labelled.
The possible ancestors of the land plants are also known as brittleworts or skunkweed. These curious labels arise from the fragility of their lime-encrusted stems, and from the foul odor these produce when stepped on.
Many botanists propose that the stoneworts and their relatives be placed in a phylum, division, sub-kingdom, or even kingdom by themselves, often named Charophyta. Their classification by taxonomists is currently undergoing much cladistic scrutiny. Further DNA and RNA analysis may prove the charophytes to be a crucial evolutionary link in the phylogenetic tree of life, the critical developmental step from the algae toward the non-vascular and then vascular land plants.

References

Further reading

  • Morton, O. 1992. Charophyta. pp.91 - 94 in Hackney, P. (Ed) 1992 Stewart and Corry's Flora of the North-east of Ireland. Third edition. Institute of Irish Studies. The Queen's University of Belfast.
  • Lloyd, James. 2007. "Cytoskeletal Structures Responsible for Cytoplasmic Streaming in Chara." St. Vincent-St. Mary High School in Accordance with Dr. Donald Ott of The University of Akron. (Science Inquiry)
stonewort in Bulgarian: Characeae
stonewort in German: Armleuchteralgen
stonewort in Hebrew: נאווניתאים
stonewort in Dutch: Kranswieren
stonewort in Japanese: 車軸藻類
stonewort in Lithuanian: Maurabragiečiai
stonewort in Norwegian: Kransalger
stonewort in Polish: Ramienicowce
stonewort in Russian: Харовые водоросли
stonewort in Swedish: Kransalger
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