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  • 1
    Electronic Resource
    Electronic Resource
    VITAMIN B12. XXVI. DEGRADATION OF FACTOR III TO 5-HYDROXYBENZIMIDAZOLE AND DERIVATIVES AND BIOSYNTHESIS OF FACTOR III (1955)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 77 (1955), S. 5192-5192 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01624a086
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Bacterial leaf symbiosis in Dioscorea sansibarensis: morphology and ultrastructure of the acuminate leaf glands (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 10 (1987), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The symbiosis between a bacterium and the West African rain forest yam Dioscorea sansibarensis is described for the first time at the ultrastructural level. The bacteria are harboured in glands which run the entire length of the pronounced ‘drip-tip’ leaf acumenae of the host plant. Each acumen, which may be up to 12 cm long in very large mature leaves, contains from two to six bacterial glands. The glands are kidney-shaped in cross section and contain numerous multicellular simple trichomes which arise from the epidermis of the gland floor and project into the lumen of the gland. The bacteria are Gram-negative and variously rod, ovoid, and coccoid in shape. The bacterial cells contain mesosomes, polyhydroxybutyrate granules and large electron-dense bodies. Bacteria-free plants grow more slowly and produce one yellowish-green leaf per node in contrast to the vigorous growth habit of infected plants, with two deep green leaves per node. Infected plants exposed to a variety of atmospheres containing acetylene, both in the light and in the dark, failed to reduce acetylene to ethylene, indicating that nitrogen fixation is not a function of this symbiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11603654
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  • 3
    Electronic Resource
    Electronic Resource
    Location and distribution of symbiotic bacteria during floral development in Ardisia crispa (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 10 (1987), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The location and distribution of symbiotic bacteria during floral development in Ardisia crispa (Thunb.) A.DC., a species characterized by bacterial leaf nodules, has been studied using light, scanning and transmission electron microscopy. During early floral development, bacteria in mucilage derived from host plant trichomes, become enclosed in a small conical chamber on top of the placenta, as a result of the closure and fusion of the carpel initials. The placental epidermal cells, which appear to be secretory in nature, become detached apically in places forming a network of grooves which traverse the placental surface. The symbiotic bacteria are preferentially located in these grooves. As growth and development of the placenta proceed, the grooves widen and deepen to form channels. The cells lining these channels secrete a mucilaginous material. The network of channels covers the entire placental surface and terminates at the placental margins surrounding the ovules. Bacteria are found within the channels, at the ends of the channels near the margin of the placenta, on the surface of the ovules and in the micropyle. It is suggested that these mucilage-filled channels are responsible for, and a prerequisite of, ensuring that the bacterial partner is efficiently transmitted from one host generation to the next by providing a mechanism by which the bacteria arc accurately placed within the developing seed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11604753
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  • 4
    Electronic Resource
    Electronic Resource
    The occurrence of calyx nodules inPsychotria spp. (Rubiaceae) (1984)
    Springer
    Protoplasma 121 (1984), S. 199-208 
    Details
    ISSN: 1615-6102
    Keywords: Psychotria ; Leaf nodules ; Calyx nodules ; Symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence and structure of calyx nodules in the flowers of two leaf nodulated rubiaceous speciesPsychotria punctata Vatke andPsychotria kirkii Hiern. has been described for the first time at the ultrastructural level. Bacteria, resident in colleter-secreted mucilage in the space between calyx and corolla, invade stomatal pores which develop on the calyx protoderm. The bacteria proliferate in the substomatal cavity and then invade the calyx mesophyll. This invasion is most pronounced inP. punctata where the bacteria even penetrate and enter the cells of the vascular tissue. Although no sheath forms around the calyx nodules, the calyx mesophyll cells surrounded by the bacteria become identical in shape, size and secretory function to the invasive mesophyll cells of leaf nodules. The functional and evolutionary significance of calyx nodulation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282313
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  • 5
    Electronic Resource
    Electronic Resource
    The initiation, development and structure of root nodules inElaeagnus angustifolia L. (Elaeagnaceae) (1985)
    Springer
    Protoplasma 128 (1985), S. 107-119 
    Details
    ISSN: 1615-6102
    Keywords: Actinorhizal root nodules ; Development ; N2 fixation ; Elaeagnus ; Frankia ; Symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A correlated light and electron microscopic study was undertaken of the initiation and development of root nodules of the actinorhizal tree species,Elaeagnus angustifolia L. (Elaeagnaceae). Two pure culturedFrankia strains were used for inoculation of plants in either standing water culture or axenic tube cultures. Unlike the well known root hair infection of other actinorhizal genera such asAlnus orMyrica the mode of infection ofElaeagnus in all cases was by direct intercellular penetration of the epidermis and apoplastic colonization of the root cortex. Root hairs were not involved in this process and were not observed to be deformed or curled in the presence of the actinomyceteFrankia. In response to the invasion of the root, host cells secreted a darkly staining material into the intercellular spaces. The colonizingFrankia grew through this material probably by enzymatic digestion as suggested by clear dissolution zones around the hyphal strands. A nodule primordium was initiated from the root pericycle, well in advance of the colonizingFrankia. No random division of root cortical cells, indicative of prenodule formation was observed inElaeagnus. As the nodule primordium grew in size it was surrounded by tanninised cells of a protoperiderm. The endophyte easily traversed this protoperiderm, and once inside the nodule primordium cortex ramified within the intercellular spaces at multiple cell junctions. Invasion of the nodule cortical cells occurred when a hyphal branch of the endophyte was initiated and grew through the plant cell wall, again by apparent enzymatic digestion. The plant cell plasmalemma of invaded cells always remained intact and numerous secretory vesicles fused with it to encapsulate the advancingFrankia within a fibrous cell wall-like material. Once within the host cell some endophyte cells began to differentiate into characteristic vesicles which are the presumed site of nitrogen fixation. This study clearly demonstrates that alternative developmental pathways exist for the development of actinorhizal nitrogen-fixing root symbioses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276333
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  • 6
    Electronic Resource
    Electronic Resource
    Nodulation of actinorhizal plants byFrankia strains capable of both root hair infection and intercellular penetration (1986)
    Springer
    Protoplasma 131 (1986), S. 82-91 
    Details
    ISSN: 1615-6102
    Keywords: Actinorhizae ; Elaeagnus ; Frankia ; Infection processes ; Myrica ; Nodule development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A morphological analysis of the initiation and development of root nodules ofElaeagnus angustifolia andMyrica cerifera inoculated with pure-culturedFrankia strains DDB 011610 or DDB 020110 was undertaken. From ultrastructural observations it was determined that both of theseFrankia strains can infectElaeagnus by an intercellular penetration mechanism andMyrica by the root hair infection mechanism. This indicates that both of these strains have the ability to infect host plant roots by either of two mechanisms. The reverse, thatElaeagnus orMyrica could be infected by both mechanisms, was not observed. The infection and nodule development processes of these two plants in combination with these strains were similar to observations made in previous studies (Miller andBaker 1985,Torrey andCallaham 1979). However, one exception was identified in the development of the prenodule ofMyrica when infected with strain 011610, in that endophytic hyphae developed vesicles within the cells of the prenodule. This event has not been described before for any of the actinorhizal genera and may be an indication of less than optimal compatibility between the host plant and the symbiont.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281689
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  • 7
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    A new earliest Paleocene (Puercan) mammalian fauna from Colorado's Denver Basin, U.S.A. (2016)
    University of Wyoming
    Details
    Publication Date: 2016-06-21
    Description: Few areas preserve the Cretaceous–Paleogene (K–Pg) boundary and earliest Paleocene (Puercan) mammalian faunas better than Colorado's Denver Basin. Research conducted decades ago described a diverse Puercan fauna from the Denver Basin, but many would agree that the best-known fauna in the basin—the Littleton fauna—probably represents a late early-Puercan (i.e., late Pu1) assemblage. Renewed collecting of fossil mammals from Denver Museum of Nature & Science (DMNH) loc. 2560 in the Denver Formation on the eastern side of the Denver Basin—approximately nine meters stratigraphically above the K–Pg boundary—has produced a Puercan faunal assemblage containing isolated teeth of at least nine species of fossil mammal. Based upon its faunal composition, low diversity, absence of taxa characteristic of middle and late Puercan faunal assemblages, and close stratigraphic proximity to the K–Pg boundary, the fauna from DMNH loc. 2560 probably represents a Puercan fauna that is earlier than the Littleton fauna. It is most similar to early Puercan (Pu1) faunas in Wyoming and northeast Montana. We document the occurrence of three species of the multituberculate Mesodma ( M. ambigua, M. formosa , and M. hensleighi ), the cimolodont Cimexomys minor , the marsupial Thylacodon montanensis , and four species of archaic ungulate (or ‘condylarth’), including Protungulatum donnae , Oxyprimus sp., Baioconodon nordicus , and Maiorana sp. The presence of P. donnae defines the onset of the Puercan age, while Oxyprimus, Maiorana , and B. nordicus are restricted elsewhere to Pu1. C. minor is known from Lancian and early Puercan (Pu1) localities. The faunal assemblage from DMNH loc. 2560 indicates that the characteristic, low-diversity Pu1 fauna found in Montana and Wyoming extended as far south as Colorado. Additionally, we report the occurrence of the ‘condylarth’ Ampliconus browni from the South Table Mountain locality (DHMH loc. 2814) near Golden, Colorado. Its presence corroborates research by others that this locality is probably temporally correlative to the late early-Puercan (late Pu1) Alexander locality south of Denver, Colorado (UCM loc. 77267 [UCM = University of Colorado Museum of Natural History]). Our research provides a more complete picture of early Puercan mammalian diversity in the Denver Basin and a means to temporally correlate early Puercan faunas from Montana to Colorado.
    Print ISSN: 1555-7332
    Electronic ISSN: 1555-7340
    Topics: Geosciences
    Published by University of Wyoming
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  • 8
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    VITAMIN B12. XXVI. DEGRADATION OF FACTOR III TO 5-HYDROXYBENZIMIDAZOLE AND DERIVATIVES AND BIOSYNTHESIS OF FACTOR III (1955)
    American Chemical Society
    Details
    Publication Date: 1955-10-01
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 9
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    Kelp, cobbles, and currents: Biologic reduction of coarse grain entrainment stress (2015)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2015-05-23
    Description: Models quantifying the onset of sediment motion do not typically account for the effect of biotic processes because they are difficult to isolate and quantify in relation to physical processes. Here we investigate an example of the interaction of kelp (Order Laminariales) and coarse sediment transport in the coastal zone, where it is possible to directly quantify and test its effect. Kelp is ubiquitous along rocky coastlines and the impact on ecosystems has been well studied. We develop a physical model to explore the reduction in critical shear stress of large cobbles colonized by Nereocystis luetkeana , or bull kelp. Observations of coarse sediment motion at a site in the Strait of Juan de Fuca (northwest United States–Canada boundary channel) confirm the model prediction and show that kelp reduces the critical stress required for transport of a given grain size by as much as 92%, enabling annual coarse sediment transport rates comparable to those of fluvial systems. We demonstrate that biology is fundamental to the physical processes that shape the coastal zone in this setting.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 10
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    Exceptional continental record of biotic recovery after the Cretaceous-Paleogene mass extinction (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉We report a time-calibrated stratigraphic section in Colorado that contains unusually complete fossils of mammals, reptiles, and plants, and elucidates the drivers and tempo of biotic recovery during the poorly known first million years after the Cretaceous–Paleogene mass extinction (KPgE). Within ~100 thousand years (ka) post-KPgE, mammalian taxonomic richness doubled and maximum mammalian body mass increased to near pre-KPgE levels. A three-fold increase in maximum mammalian body mass and dietary niche specialization occurred at ~300 ka post-KPgE, concomitant with increased megafloral standing species richness. The appearance of additional large mammals occurred by ~700 ka post-KPgE, coincident with the first appearance of Leguminosae (bean family). These concurrent plant and mammal originations and body mass shifts coincide with warming intervals, suggesting climate influenced post-KPgE biotic recovery.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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