Charales

Stoneworts
Chara globularis
Scientific classification
Kingdom: Plantae
Division: Charophyta
Class: Charophyceae
Order: Charales
Family: Characeae
Genera

Chara
Lamprothamnium
Nitella
Tolypella

Charales is an order of pondweeds, freshwater algae 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.

Contents

Description

The Charales have large, macroscopic thalli growing up to 120 cm long, they are branched, multicellular, and use chlorophyll to photosynthesize. They grow in fresh water. They may be called stoneworts,[1] 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. 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 worldwide, with 33 in Britain and Ireland according to Groves and Bullock-Webster),[2][3] however Stewart and Church (1992) reduce this to 21.[4]

Characeae are the principal plant life of some of the volcanic crater lakes of Nicaragua, and can be found in excess of 20 meters depth in some circumstances. Introduced tilapia (Oreochromis niloticus) consumed all the Characeae in Lake Apoyo[5].

Species

British Isles

Ref: Stewart & Church (1992).[4]

Other regions

Distribution

Ireland

Ecology

The Characeae are aquatic though some can survive in brackish or maritime habitats. They are to be found usually in still, clear, non-flowing, water attached by rhizoids. They can be pioneer colonizers or ephemerals.[10] They are usually found in low to medium nutrient-rich water and tend to disappear due to eutrophication.

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

  1. ^ Kapraun DF (April 2007). "Nuclear DNA content estimates in green algal lineages: chlorophyta and streptophyta". Ann. Bot. 99 (4): 677–701. doi:10.1093/aob/mcl294. PMC 2802934. PMID 17272304. http://aob.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=17272304. 
  2. ^ Groves, J. and Bullock-Webster, G.R. 1920. The British Charophyta. Vol.1, Nitelleae. London, The Ray Society
  3. ^ Groves, J. and Bullock-Webster, G.R. 1924. The British Charophyta. Vol.2, Characeae.. London, The Ray Society
  4. ^ a b Stewart, N.F. and Church, J.M. 1992. Red Data Books of Britain and Ireland. The Joint Nature Conservation Committee, Peterborough. ISBN 1-873701-24-1
  5. ^ McCrary JK, Murphy BR, Stauffer, Jr. JR, Hendrix SS (2007): Tilapia (Teleostei: Cichlidae) status in Nicaraguan naturalwaters; Env. Biol. Fishes 78:107-114 [1]
  6. ^ ITIS Standard Report Page: Chaetosphaeridiaceae
  7. ^ Algaebase :: Species Detail
  8. ^ a b c Morton, O. 1992 in Hackney, P. (Ed.) Stewart & Corry's Flora of the North-east of Ireland. Institute of Irish Studies and The Queen's University of Belfast ISBN 0-85389-446-9 (HB)
  9. ^ Guiry, M.D., John, D.M., Rindi, F. and McCarthy, T.K 2007. New Survey of Clare Island Volume:6: The Freshwater and Terrestial Algae. Royal Irish Academy. ISBN 978-1-904890-3-7
  10. ^ John, D.M., Whitton, B.A. and Brook, A.J. 2002. The Freshwater Algal Flora of the British Isles. Cambridge University Press, London. ISBN 0-521-77051-3

Further reading

Further links

Rhodophyta
Glaucocystophyceae
Viridiplantae/
Plantae
sensu stricto