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Genetic Evidence Suggests That Homosporous Ferns with High Chromosome Numbers are Diploid -- Haufler and Soltis 83 ... Homosporous ferns have usually been considered highly polyploid because they have high chromosome numbers (average n = 57.05). Therefore, homosporous ferns either have gone through repeated cycles of polyploidy and gene silencing or were initiated with relatively high chromosome numbers. The latter possibility represents a radical departure from currently advocated hypotheses of fern evolution and suggests that there may be fundamental differences between the genomes of homosporous ferns and those of higher plants. www.pnas.org /cgi/content/abstract/83/12/4389   (384 words)

lab7 In homosporous plants usually a large number of sporocytes from the central tissue of the developing sporangium undergo meiosis to produce numerous spores. When homosporous spores germinate to produce the multicellular haploid gametophyte, these gametophytes germinate and continue to grow outside of the confines of the spore wall, and establish themselves as independent ("free living") plants. In contrast to the situation in homosporous plants, where the gametophyte is produced outside of the spore wall upon germination, the micro- and megagametophytes are produced within the micro- and megaspore walls, respectively. lsvl.la.asu.edu /plb306/lab6.htm   (2085 words)

IU Biology Faculty: Gerald Gastony Genome Structure and Evolution in Homosporous Ferns — Homosporous ferns are characterized by high chromosome numbers (n average = 57), suggesting that they are polyploids compared to the heterosporous angiosperms (n average = 16), but isozyme gene expression patterns of ferns are the same as those typical of diploid angiosperms. In this first characterization of a homosporous fern genome, we use restriction fragment length polymorphism (RFLP) markers to infer the number of gene copies and their distribution in the genome and amplified fragment length polymorphisms (AFLPs) and isozyme markers to increase saturation of the linkage map. Homosporous ferns are the vast majority of species that compose the clade that is the phylogenetic sister group to seed plants. www.bio.indiana.edu /facultyresearch/faculty/Gastony.html   (671 words)

Self-Service Science Forum Message   (Site not responding. Last check: 2007-10-26) Homosporous vascular plants, simple sporophytes with no differentiation between root and shoot, motile sperm. The single surviving genus Equisetum: Homosporous vascular plants with jointed stems marked by conspicuous nodes and elevated siliceous ribs, and sporangia borne in a strobilis at the apex of the stem. Mostly homosporous, and all have megaphylls (proper leaves with vascular tissue and a leaf trace with a leaf gap). www2.abc.net.au /science/k2/stn/march2000/posts/50965.shtm   (474 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. Spores are tetrahedral and trilete in homosporous taxa and in Selaginella, while those of Isoëtes are monolete. Gametophytes of homosporous genera may be epiterrestrial or subterranean. www.science.siu.edu /landplants/Lycophyta/Lycophyta.desc.html   (731 words)

Lycopodiophyta - Wikipedia, the free encyclopedia These species reproduce by shedding spores and have macroscopic alternation of generations, although some are homosporous while others are heterosporous. There are three main groups within the Lycopodiophyta, sometimes separated at the level of order and sometimes at the level of class. 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. en.wikipedia.org /wiki/Lycopodiophyta   (423 words)

Devonian Times - More about Ferns All living and most fossil sphenopsids were homosporous, but heterospory is known in some arborescent (tree-like) fossils. This order contains both homosporous (producing one type of bisexual spore) and heterosporous (producing female-like megasores and male-like microspores) taxa. They possessed webbed megaphylls and quadriseriate (four-ranked) branching, and were probably all homosporous. www.devoniantimes.org /who/pages/ferns.html   (1914 words)

Genetic Evidence Suggests That Homosporous Ferns with High Chromosome Numbers are Diploid -- Haufler and Soltis 83 ...   (Site not responding. Last check: 2007-10-26) Homosporous ferns have usually been considered highly polyploid because they have high chromosome numbers (average n = 57.05). Therefore, homosporous ferns either have gone through repeated cycles of polyploidy and gene silencing or were initiated with relatively high chromosome numbers. The latter possibility represents a radical departure from currently advocated hypotheses of fern evolution and suggests that there may be fundamental differences between the genomes of homosporous ferns and those of higher plants. intl.pnas.org /cgi/content/abstract/83/12/4389   (300 words)

Associate Web Page Homosporous ferns, which produce only one kind of spores, are known to have high chromosome numbers compared to heterosporous plant species (e.g. For this reason, homosporous ferns are believed to be polyploids. To resolve this discrepancy, Haufler (American Journal of Botany 74: 953-966) hypothesized that homosporous ferns are ancient polyploids (paleopolyploids) that have gone through gene silencing. evodevo.uoregon.edu /people/nakazato.html   (360 words)

Seedless Vascular Plants Homosporous and the spores are borne in sporangia on short lateral branches Homosporous and the sporangia are borne in a strobilus, on umbrella shaped sporangiophores Strobili may be borne at the tips of a vegetative axis, or borne on a non-chlorophyllous fertile branch that develops from the rhizome arnica.csustan.edu /boty1050/Ferns/ferns.htm   (811 words)

Homosporous life histories (from plant) --  Encyclopædia Britannica A homosporous life history occurs in nearly all bryophytes and in most pteridophytes. It is characterized by morphologically identical spores that germinate to produce bisexual (both male and female) gametophytes in pteridophytes, but either bisexual or more usually unisexual (either male or female) gametophytes in bryophytes. More results on "Homosporous life histories (from plant)" when you join. www.britannica.com /eb/article-66089   (841 words)

Nat' Academies Press, (NAS Colloquium) Variation and Evolution in Plants and Microorganisms: Towards a New Synthesis: ... 60 –62), lycophytes, and Equisetum with a homosporous life cycle; all of these groups are the descendants of ancient plant lineages that extend back to the Devonian Period (63). The mean gametic chromosome number for homosporous pteridophytes is n = 57; for angiosperms, it is n = 16 (64). Despite their high chromosome numbers, however, homosporous pteridophytes exhibit diploid gene expression at isozyme loci (65 –68). www.nap.edu /openbook/0309070791/html/116.html   (1551 words)

Pteridophytes   (Site not responding. Last check: 2007-10-26) Sporangia free, borne axillary on sporophylls which are often condensed into strobili; homosporous or heterosporous; axis with differentiated roots... Plants cylindrical with regular sheathed nodes, scariose, bract-like leaves borne in a single whorl at each node, the stem photosynthetic, hollow, containing many silica crystals; homosporous, spores chlorophylous (Equisetophyta)... Homosporous; leaves eligulate, mostly arranged in close spirals, sometimes decussate, sometimes dorsiventrally flattened with all but 2 rows reduced; supported by clusters of roots www.anbg.gov.au /projects/fern/taxa/pteridophyte.html   (789 words)

FERN.6 This group is characterized by homosporous, eusporangiate plants that bear their sporangia in a fertile spike. Filicaleans are homosporous and bear a relatively small number of spores in reduced sporangia called leptosporangia. Leptosporangia are stalked and have an annulus, a group of larger, thicker-walled cells on a portion of their surface. lsweb.la.asu.edu /kpigg/modernferns&conifers.htm   (2397 words)

Non-Flowering Plant Families, UH Botany The Equisetaceae are terrestrial, herbaceous, homosporous vascular plants comprising a single genus with about 15 species. The free-living sporophytic plant body consists of a rhizome with adventitious roots, and an aerial portion with ribbed, silicified stems that are hollow except at the jointed nodes which bear whorls of reduced scalelike megaphyllous leaves, sometimes alternating with branches. Cells in the stem may be silicified or glasslike, contributing to the utility of the stems in scouring pots and pans, a quality that was exploited by pioneers in western North America. www.botany.hawaii.edu /faculty/carr/equiset.htm   (319 words)

plants Spores of Psilotum are of one type (homosporous) and therefore the gametophytes produce both male and female gametes. Most ferns that we study are homosporous, with well defined independent gametophytes often seen on flower pots in the greenhouse, but there are five genera, in two orders that are heterosporous, with reduced gametophytes that resemble those of Selaginella. This is also true of embryos of homosporous vascular plants such as ferns, although seeds are lacking. www.nsci.plu.edu /~jmain/b323web/pages/plants.htm   (3032 words)

Lab VII - The Origin of Seed Plants (2) Some were homosporous like other Devonian euphyllophytes (e.g., Psilophyton and Pertica), while others were heterosporous (produced two types of spores). In fertile axes, ultimate branches are replaced by dichotomies with multiple homosporous sporangia arising along the length of each fork of the branch. According to this argument, heterospory was the intermediate between homosporous free-sporing reproduction and the retained endosporic gametophyte of the seed habit. www.ucmp.berkeley.edu /IB181/VPL/Osp/Osp2.html   (997 words)

ARS | Publication request: Multiple Ribosomal Rna Gene Loci in the Genome of the Homosporous Fern Technical Abstract: The genomes of homosporous ferns are largely uncharacterized, but they appear to differ from gymnosperms and angiosperms in key aspects, such as high chromosome numbers at the diploid level, and thus provide a unique perspective on plant genome structure and evolution. The homosporous fern, ceratopteris richardii, was the model used in the study. These results suggest that the gross morphology of rDNA loci are similar between diploid homosporous ferns and angiosperms, but that important clues to rDNA gene and chromosome evolution in homosporous ferns may reside in the analysis of their minor rDNA sequences. ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=102220   (490 words)

C-Fern - A Plant For Teaching and Research Abnormal reductional and nonreductional meiosis in Ceratopteris: Alternatives to homozygosity and hybrid sterility in homosporous ferns. 1999.Multiple ribosomal RNA gene loci in the genome of the homosporous fern Ceratopteris richardii. McGrath, J.M. and E. Pichersky 1997.Methylation of somatic and sperm DNA in the homosporous fern Ceratopteris richardii. cfern.bio.utk.edu /manual/biblio.html   (2392 words)

Ch 27   (Site not responding. Last check: 2007-10-26) The sporangia are arranged in clusters called sori and equipped with spring-like devices that catapult spores several meters. Most ferns are homosporous although the archegonia and antheridia mature at different rates to ensure cross fertilization between gametophytes. Homosporous is a description for a plant that makes a single type of spore. www.nmc.edu /~ftank/temp/sg27.html   (1474 words)

Lower Vascular Plants F00   (Site not responding. Last check: 2007-10-26) In homosporous strobili such as those of the club moss Lycopodium, all of the spores produced are alike, and the gametophytes they produce can produce both archegonia and antheridia. Ferns have their xylem and phloem arranged in a siphonostele in which primary xylem and phloem -- not just secondary -- are arranged in rings. The fern used as an example in lab is is a hydrophyte with aerenchyma, and is homosporous. trevor.butler.edu /~kschmid/302/rvlvpf00.htm   (849 words)

FIELD SYSTEMATIC BOTANY - PTERIDOPHYTES - HUGH WILSON Microphyllous, homosporous with eusporangia in leaf axiles, often clustered a tips of dichotomously branching stems as STROBILI [STROBILUS]. Eusporangiate, homosporous with a strong leaf dimorphism (sterile (Sporophore) vs. fertile (Trophophore)) with eusporangia in "fertile spikes" and underground, micotrophic gametophytes. "Other" Ferns: the largest and most diverse group - leptosporangiate, homosporous, variously classified, often (as in Correll and Johnston, 1977) put together as the Polypodiaceae (50 genera worldwide, 22 genera with 71 species in Texas - flora of Robertson county lists 9 genera with 10 species). www.csdl.tamu.edu /FLORA/fsb/fsbfern1.htm   (1017 words)

Funded Projects   (Site not responding. Last check: 2007-10-26) Because homosporous ferns have high chromosome numbers compared to other vascular plants, they have long been considered polyploids. The proposed study will provide the most comprehensive evidence bearing on paleopolyploidy in homosporous ferns to date, and thus provide the foundation for future studies of their biology and evolution. The evolution of virulence, as well as resistance to antibiotics and disease, often involves recombination between divergent genomes, yet the broader evolutionary role of wide recombination or hybridization is poorly understood. www.bio.indiana.edu /~rieseberglab/projects.html   (2369 words)

The Haploid-Diploid Life Cycle   (Site not responding. Last check: 2007-10-26) The most common relationship among land plants is when the SPT is dominant over GPT, as is the case with all vascular plants. Some 1n-2n plants have only one morphological type of spore, and are called homosporous. All GPT dominant plants are homosporous, where as SPT dominant plants can be either homosporous or heterosporous. www.ucmp.berkeley.edu /glossary/gloss6/altergen.html   (296 words)

PTEROPHYTA Ferns are usually homosporous and the sporangia often develop in a sorus covered by an indusium (not present in polypodies). Sori usually develop on the underside of leaves as spots or bands or along the leaf margin. For the typical homosporous fern the gametophyte is bisexual. www.hcs.ohio-state.edu /hcs300/svp2.htm   (399 words)

Olympus Microscopy Resource Center: Anatomy of the Microscope - Brightfield Microscopy Digital Image Gallery - ... Similar to other primitive vascular plants, they exhibit an asexual reproductive structure, the sphenophyte strobilus, more commonly known as a cone. Unlike the better-known pinecone, however, the strobili of the horsetail plant may only contain one type of spore since they are homosporous. Horsetail cones, each of which encases many sporophylls within a single sporangium or case, form along the uppermost region of the plant’s branches. www.olympusmicro.com /primer/anatomy/brightfieldgallery/horsetailstrobilussmall.html   (343 words)

Search Results for ploidy - Encyclopædia Britannica It is characterized by morphologically identical spores that germinate to produce bisexual (both male and female)... It is characterized by morphologically dissimilar spores produced from two types of sporangia: microspores, or male... The gymnosperms and angiosperms not only lack some reproductive structures found in the homosporous and heterosporous pteridophytes but also have certain reproductive structures peculiar to the seed... www.britannica.com /search?query=ploidy&submit=Find&source=MWTEXT   (230 words)

Homosporous   (Site not responding. Last check: 2007-10-26) The word "homosporous" uses 11 letters: H M O O O O P R S S U. Words within homosporous not shown as it has more than seven letters. List all words starting with homosporous, words containing homosporous or words ending with homosporous www.morewords.com /word/homosporous   (148 words)

Bio-Tech Info - Gene Silencing Consistent gene silencing in transgenic plants expressing a replicating potato virus X RNA, The EMBO Journal, 16(12):3675-3684, 1997. Gene Silencing in a Polyploid Homosporous Fern: Paleopolyploidy Revisited, Proceedings of the National Academy of Sciences, 88:1602-1605, 1991. Flavonoid genes in petunia: addition of a limited number of gene copies may lead to a suppression of gene expression, The Plant Cell, 2:291-299,1990. www.biotech-info.net /gene_silencing.html   (538 words)

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