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Schneider, Harald* and Kathleen M. Pryer.   (Site not responding. Last check: 2007-10-26) Recent phylogenetic studies have demonstrated convincingly that heterosporous ferns are a monophyletic group nested within leptosporangiate ferns. Heterosporous ferns have an aquatic lifestyle, similar to that of Paleozoic seed plants. This leads to the hypothesis that heterosporous ferns have evolved analogous megaspore structures to seed plants and these can be used as a model to better understand the biological constraints in which the seed habit evolved. www.ou.edu /cas/botany-micro/botany2000/section2/abstracts/27.shtml   (334 words)

Pryer, Kathleen M.* and Harald Schneider.   (Site not responding. Last check: 2007-10-26) Heterosporous ferns — characterized by morphologically distinct spores producing unisexual gametophytes — form a monophyletic clade nested within the otherwise homosporous leptosporangiate ferns, Polypodiidae. In all, approximately 200 extinct species of heterosporous ferns are preserved in the fossil record, mostly in the form of microfossils with a remarkable diversity of ornamented spores. Recent phylogenetic analyses resolved the relationships among the five extant genera of heterosporous ferns, but these ferns have been largely ignored in systematic studies and infrageneric relationships are virtually unknown. www.botany2002.org /section11/abstracts/18.shtml   (327 words)

NationMaster - Encyclopedia: Lycopodiophyta Heterosporous plants, such as spikemosses, quillworts, and some aquatic ferns produce spores of two different sizes: the larger spore effectively functioning as a female spore and the smaller functionally male. The vulnerable meiotic gametophyte is protected from radiation by its reduced size and often by the use of subterranean mycorhiza for its energy source instead of photosynthesis. In heterospores the female spores are larger than the male because they store food for the new generation. www.nationmaster.com /encyclopedia/Lycopodiophyta   (1546 words)

Schneider, Harald*, Kathleen M. Pryer, and Richard Lupia.   (Site not responding. Last check: 2007-10-26) Heterosporous ferns are a monophyletic lineage comprising five extant genera that fall into two clades: Marsileaceae, including Marsilea, Pilularia and Regnellidium; and Salviniaceae, including Azolla and Salvinia. Observations from light and scanning electron microscopy indicate that the megaspores of each of the heterosporous fern genera have a uniquely modified outer spore wall (perine) above the aperture, which is referred to as an acrolamella, and they also differ substantially in the details of their perine ultrastructure. The evolution of mega- and microspore characters is inferred using a phylogeny obtained from an independent analysis of nucleotide sequence data. www.botany2001.org /section2/abstracts/23.shtml   (338 words)

Spore - Wikipedia, the free encyclopedia Their chief advantage is that, of all forms of progeny, spores require the least energy and materials to produce. Vascular plant spores are always haploid and vascular plants are either homosporous or heterosporous. Heterosporous plants, such as spikemosses, quillworts, and some aquatic ferns produce spores of two different sizes: the larger spore in effect functioning as a "female" spore and the smaller functioning as a "male". en.wikipedia.org /wiki/Spore   (641 words)

Duke University Herbarium Project on Ferns Heterosporous ferns are monophyletic and comprise two extant families, the semi-aquatic Marsileaceae and the aquatic Salviniaceae. Heterosporous ferns are relative newcomers that diversified during the Cretaceous, at the same time as flowering plants. The primary goal of our research is to reconstruct a comprehensive phylogeny for the heterosporous aquatic ferns (Marsileaceae and Salviniaceae), including living and fossil members, incorporating data from multiple genes, morphology, and developmental studies for the living taxa, and integrating morphological data from fossil taxa. www.biology.duke.edu /herbarium/ferns_morfevol.html   (263 words)

Lab 10 Vocabulary List In heterosporous plants, a haploid spore produced within a megasporangium of the sporophyte. In heterosporous plants, a sporangium that produces microspores.Usually morphologically distinct from the megasporangium. In heterosporous plants, a haploid spore produced within a microsporangium of a sporophyte. online.sfsu.edu /~biol240/labs/lab_10plantoverview/pages/10vocab.html   (1695 words)

leptosporangiate ferns The monophyly of the heterosporous ferns (Azollaceae, Salviniaceae, and Marsileaceae) is the most strongly supported result from all analyses in Pryer et al. Their cladistic analysis of heterosporous ferns demonstrated that they are a monophyletic group, which led these authors to readopt the order Hydropteridales. Although the tree ferns, the heterosporous ferns, and the schizaeoid ferns are each well supported clades, their interrelationships (and those of all basal families) remain unresolved. tolweb.org /tree?group=Leptosporangiate_Ferns&contgroup=Filicopsida   (3161 words)

Botany 2004 - Abstract Search Heterosporous ferns, Marsileaceae and Salviniaceae, bear sori either on or within modified reproductive organs. In Marsileaceae, sori are borne on a sorophore, and both of these are enclosed by a sclerenchymatous sporocarp wall. Although the monophyly of heterosporous ferns is now well established, the homology of the fertile structures within the group has been unclear. www.2004.botanyconference.org /engine/search/index.php?func=detail&aid=634   (233 words)

Palaeos Plants: Glossary L-Q Megagametophyte: in heterosporous plants and in seed plants, the female gametophyte produced by a megaspore. Microgametophyte in heterosporous plants and in seed plants, the male gametophyte produced by a microspore. Microspore: a small, haploid (N=1) spore of a heterosporous plant that produces a microgametophyte (male gametophyte). www.palaeos.com /Plants/Lists/Glossary/GlossaryL.html   (2409 words)

[No title] The heterosporous life cycle is a modification of the homosporous life cycle, and further modifications in the heterosporous life cycle lead to seed plants (including flowering plants). The heterosporous life cycle is derived from the homosporous life cycle by modification of the gametophytes. The life cycle of seed plants is derived from the heterosporous life cycle by further modification and reduction of the gametophytes, and by the megagametophyte remaining within the megasporangium for its entire life. www.plantbio.ohiou.edu /epb/instruct/archivedcourses/111-03gwr/Lab-8.htm   (2523 words)

Spartanburg SC | GoUpstate.com | Spartanburg Herald-Journal   (Site not responding. Last check: 2007-10-26) Their chief advantage is that, of all forms of progeny, spores require the least energy and materials to produce. Vascular plant spores are always haploid and vascular plants are either homosporous or heterosporous. Heterosporous plants, such as spikemosses, quillworts, and some aquatic ferns produce spores of two different sizes: the larger spore in effect functioning as a "female" spore and the smaller functioning as a "male". www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=spore   (938 words)

Phylum Lycophyta Sporangia are positioned on the adaxial side of specialized leaves that in turn are arranged in zones along the stem or in a terminal series, known as strobili. Lycophytes are eusporangiate and may be either homosporous or heterosporous. In heterosporous genera, spores germinate and develop into mature gametophytes without emerging from the spore wall; they are endosporic. www.science.siu.edu /landplants/Lycophyta/Lycophyta.desc.html   (731 words)

Journal of Paleontology: ARCELLITES STELLATUS NEW SPECIES, A NEW MEGASPORE FROM THE LOWER CRETACEOUS OF MARYLAND, USA DISPERSED MEGASPORES with affinities to aquatic heterosporous ferns are relatively common in mesofossil assemblages from the Early Cretaceous to the Recent. Extant heterosporous ferns are free floating or shallow rooted freshwater plants, with a dominantly tropical to warm-temperate distribution (Tryon and Lugardon, 1991). Thus the abundance of heterosporous fern megaspores, or the presence of heterosporous fern macrofossils, within a stratigraphie interval may be indicative of a shallow, calm, freshwater depositional environment (Hall, 1963; Batten et al., 1996; Rich et al., 2001). www.findarticles.com /p/articles/mi_qa3790/is_200411/ai_n9461507   (1153 words)

Publication SCHNEIDER, H. and K.M. Structure and function of spores in the aquatic heterosporous fern family Marsileaceae. Internal nodes at the base of the fern topology are very weakly supported, making it impossible to say with certainty how any of the major basal groups of ferns are related to one another. These basal branches of the fern topology are critically important not only for stabilizing the overall framework for ferns, but also for resolving relationships among the "deep" branches of land plants (lycophytes, sphenophytes, eusporangiate ferns) and elucidating which of these are the sister group to seed plants. www.fieldmuseum.org /research_collections/botany/botany_sites/ferns/publications2.html   (2255 words)

Essay: Heterosporous Plants - Coursework.Info Heterosporous Plants ('hetero-' 'different') An important change took place in many of the major plant groups during the Devonian period. Now, some plants began to produce two kinds of spores from two kinds of sporangia, an evolutionary stage which some algae were also to reach in the sea. In heterosporous plants the two different spores germinate into two small, but distinctly different, gametophytes which remain within spores and never grow into a large green plant. www.coursework.info /University/Biological_Sciences/Botany/Heterosporous_Plants_L509.html   (251 words)

HETEROSPOROUS FERNS: PHYLOGENY, ORIGIN AND RADIATION Read directly from the fossil record, the first appearance of heterosporous ferns reliably dates to the earliest Cretaceous and their radiation is broadly coincident with the radiation of flowering plants and derived ferns. Updating the work of Kovach and Batten (1993) and placing taxa in a phylogenetic framework, we investigate the likely timing of heterosporous fern origins and trace their diversification through time and space. Utilizing the record of dispersed megaspores, stratigraphic confidence intervals may be calculated for each of the clades delimited in the phylogeny. gsa.confex.com /gsa/2004AM/finalprogram/abstract_80062.htm   (442 words)

* Heterosporous - (Biology): Definition These may come from the same or different sporangia, and may produce similar or different gametophytes. Lepidodendron was a heterosporous tree common in coal swamps. Fossil from the Devonian period reveal fernlike plants that were heterosporous; that is, produced two kinds of spores. en.mimi.hu /biology/heterosporous.html   (113 words)

Heterosporous life histories (from plant) --  Encyclopædia Britannica A heterosporous life history occurs in some pteridophytes and in all seed plants. It is characterized by morphologically dissimilar spores produced from two types of sporangia: microspores, or male spores, and megaspores (macrospores), or female spores. More results on "Heterosporous life histories (from plant)" when you join. www.britannica.com /eb/article-66091   (847 words)

Seedless Vascular Plants The gametophyte produced by the heterosporous plant is unisexual. Depending on the taxonomic group they are homosporous or heterosporous. Isoeataceae is the other heterosporous group of lycophyta. carroll1.cc.edu /~jclausz/botany/SeedlessVascPlts.html   (918 words)

Botany 2006 - Abstract Search PHYLOGENETIC analyses have demonstrated that the leptosporangiate heterosporous fern families Marsileaceae (Marsilea, Pilularia, Regnellidium) and Salviniaceae (Azolla and Salvinia) are most closely related to one another—the Salviniales. The fossil record of heterosporous ferns is largely composed of dispersed megaspores and microspores. That record is dense enough to permit the application of confidence intervals and stratigraphically constrained phylogenetic analyses to investigate the likely timing of their origins and trace their diversification through time and space. www.2006.botanyconference.org /engine/search/index.php?func=detail&aid=535   (339 words)

Australian Biological Resources Study - Glossaries Vascular plants - Flora of Australia - M megagametophyte: a plant body or cell lineage, formed by vegetative growth of the megaspore, that produces the female gametes of a heterosporous plant. microgametophyte: a plant body or cell lineage, formed by vegetative growth of the microspore, that produces the male gametes of a heterosporous plant. microspore: the smaller of the two kinds of spores produced in the sexual life cycle of a heterosporous plant, giving rise to the male gametophyte. www.environment.gov.au /biodiversity/abrs/online-resources/glossaries/vascular/m.html   (690 words)

Notes to Accompany "Plant Kingdom Phyla" Conifers are heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Cycads are heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Ginkgophyta is heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. www.austincc.edu /plants/notes.html   (955 words)

Heterosporous - Wikipedia, the free encyclopedia Wikimedia needs your help in its US$200,000 fund drive. Heterosporous plants, such as spikemosses, quillworts, and some aquatic ferns produce spores of two different sizes: the larger spore effectively functioning as a female spore and the smaller functionally male. This page was last modified 21:35, 3 June 2005. en.wikipedia.org /wiki/Heterosporous   (65 words)

lycopod picture links Tree-like lycopods were heterosporous; in some forms the megaspores with surrounding megasporangia and megasporophylls look almost seed-like. The plants were heterosporous and some of the strobili, known as Lepidostrobus, could reach a length of nearly 1 m. Chaloneria is was an up to 2 m high unbranched heterosporous lycopod with axes up to 10 cm in diameter with roots of the Stigmaria-Isoetes type. www.uni-muenster.de /GeoPalaeontologie/Palaeo/Palbot/seite6.htm   (880 words)

Spartanburg SC | GoUpstate.com | Spartanburg Herald-Journal   (Site not responding. Last check: 2007-10-26) An independent sporophyte is the dominant form in all clubmosses, horsetails, ferns, gymnosperms, and angiosperms (flowering plants) that have survived to the present day. Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores. During the Devonian period several plant groups independently evolved heterospory and subsequently the habit of endospory, in which single megaspores were retained within the sporangia of the parent sporophyte, instead of being freely liberated into the environment as in ancestral exosporous plants. www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=sporophyte   (542 words)

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