Nitella C.Agardh, 1824

Lectotype species: Nitella opaca (C.Agardh ex Bruzelius) C.Agardh

Currently accepted name for the type species: Nitella opaca (C.Agardh ex Bruzelius) C.Agardh

Original publication: Agardh, C.A. (1824). Systema algarum. pp. [i]-xxxvii, [1]-312. Lundae [Lund]: Literis Berlingianis [Berling].

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Description: Mature plants 30-100 cm heigh, attached with numerous basal rhizoids, these multicellular, colorless and branched. Primary axes with alternating sequence of nodal and internodal cells developed from apical cell. Each apical cell derivative divides transversely and the daughter cells develop into multicellular nodal complex with 6 (rarely 7-8) peripheral cells, and its internodal cell, respectively. Each peripheral cell divides periclinally; the inner cell develops into a basal node, whereas the outer becomes an apical cell and produces the branchlet; stipulodes absent. Each node with whorl of four to many determinate, ecorticate branchlets. Branchlets furcate, with sympodial growth, appearing di- or trichotomously branched to 3-4 orders, with acuminate branch tips. Indeterminate axes up to two or more per node, developing in axils of branchlets and scattered on plant. Cortication on internodal cells absent. Cytoplasm distinctly layered with external stationary layer with rows of helicoidally aligned chloroplasts (ectoplasm) and internal streaming layer with nuclei, mitochondria (endoplasm); cells with large central vacuole. Sexual reproduction oogamous with gametes produced in multicellular gametangia. Species uni- or bisexual, in former antheridia single and terminal at point of furcation, oogonia lateral and subtending furcation. In bisexual species antherida as in unisexual forms with one to several oogonia subtending node. Antheridia similar to Chara except for presence of two rather than one stalk cell, developing from terminal cells of branchlets. Antheridial stalk cells formed after development of antheridial mother. Sperm released from antheridial filament by pore in cell wall; pore more specialized than in Chara. Oosporangia encrusted with calcium carbonate, with two, 5-celled tiers of crown cells; at maturity compressed laterally. Oosphere with three sterile cells. Zygote germination associated with development of protonemal stage that undergoes divisions to form large and small cells. The primary axes develop as lateral branches to the protonema. Life history presumably zygotic with meiosis occurring during zygote germination, however exact position of meiosis not clarified. As in embryophytes, centrioles arise de novo in spermatogenous tissue; centrioles give rise to basal bodies. Mature sperm cell streamlined and coiled, similar to Chara, bryophytes and Selaginella. Parallel basal bodies inserted anteriorly and flagella directed rearward, coiling with the cell body. A row of mitochondria occupy the anterior of the cell, the condensed coiled nucleus is in the mid-region and a row of starch-filed plastids with associated mitochondria are in cell posterior. A peripheral microtubular ribbon provides the framework for the cell. Similar to land plants and Coleochaetales, the Nitella spermatozoid with multilayered structure (MLS); thus differing from Chara spermatozoids where the MLS has been lost. Nitella cosmopolitan, present in fresh or slightly brackish water; endemic species present on all continents (except Antarctica). Unisexual species tend to be endemic; bisexual species more widely distributed. Oospores of N. furcata with temperature dependent annual cycle of germination. Subfossil oospores can be identified from lake sediments. Nitella used as a model system for studies of cytoplasmic streaming, and cell wall synthesis. Cell elongation associated with regions of lower pH and wall extensibilibity apparently regulated by localized proton extrusion into acidic bands. Primary and secondary walls structurally different in internodal cells with primarily transverse and helicoidal microfibrils respectively; however, chemical differences qualitative rather than quantitative. Cell wall proteins apparently do not play significant role in regulation of internode expansion. Deposition of cell wall appositions containing callose and pectin associated with glycosomes and induced by chlortetracycline; these plugs similar to wound plugs induced by mechanical injury. Rosette/globular morphology of terminal complexes similar to that in land plants and other Charophyceae. Numerous studies have been carried out on ion transport, electrophysiology and metabolism. Cytokinesis via phragmoplast typical of charophytes and land plants. Paleonitella from Lower Devonian Rhynie chert at least 400 million years old, with parasitizing plasmodiophoromycetes. Characters for species segregation include unisexual versus bisexual nature of plants, morphology of branchlets, chromosome numbers, gametangial size and arrangement. Ultrastructural features associated with surface ornamentation of the oosporangial wall define five major structural types with most species having apparently unique features. With Tolypella comprises tribe Nitellae. Genus (and Charales in general) of considerable phylogenetic importance in that complex implicated either as possible sister group of all land plants or as derived from primitive land plants by reduction.

Information contributed by: D. Garbary & K. Renzaglia . The most recent alteration to this page was made on 2011-05-04 by Anders Langangen.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Bryant, J.A. & Stewart, N.F. (2002). Order Charales. In: The Freshwater Algal Flora of the British Isles. An identification guide to freshwater and terrestrial algae. (John, D.M., Whitton, B.A. & Brook, A.J. Eds), pp. 593-612. Cambridge: Cambridge University Press.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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Anders Langangen in Guiry, M.D. & Guiry, G.M. 04 May 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 10 August 2022

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