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  • Ultrastructure  (10)
  • Nitrogen fixation  (6)
  • Springer  (16)
  • 1980-1984  (16)
  • 1955-1959
  • 1981  (16)
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Keywords
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  • Springer  (16)
Years
  • 1980-1984  (16)
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure of the sperms ofPlumbago zeylanica (1981)
    Springer
    Protoplasma 107 (1981), S. 85-107 
    Details
    ISSN: 1615-6102
    Keywords: Male cytoplasmic inheritance ; Plumbago ; Pollen grain ; Pollen tube ; Sperm ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male gametes ofPlumbago zeylanica were examined in pollen grains and tubes using light and electron microscopy of chemically and physically fixed tissues, and Nomarski interference microscopy of isolated, living sperm cells. Male gametes are elongate, spindleshaped cells containing a nucleus, mitochondria, ER, ribosomes, vesicles, dictyosomes, probable microfilaments, and a variable number of plastids. In mature pollen grains ofP. zeylanica, the two sperm cells are directly linked; they share a transverse cell wall with plasmodesmata and are enclosed together by the inner vegetative cell plasma membrane. One of these two sperms is also associated with the vegetative nucleus as a consistent feature of pollen grain organization. The basis of this association appears to be a long, narrow projection of the sperm cell (averaging 〈 1 μm wide and about 30 μm long) which wraps around the periphery of the vegetative nucleus and occupies embayments of that nucleus. This association is maintained throughout pollen tube growth but becomes less extensive near the completion of tube growth and is severed following tube discharge. The consistent occurrence of the sperm-vegetative nucleus association in pollen grains, tubes and isolated pollen cytoplasm suggests that the two structures may be directly connected, but attempts to visualize this type of connection were unsuccessful. Possibly, the entwining nature and extent of complementary interfaces between vegetative nucleus and sperm may have a role in stabilizing their association. Functionally, the two sperms and vegetative nucleus appear to travel as a linked unit within the pollen tube, possibly increasing the effectiveness of gamete delivery and helping to ensure nearly simultaneous transmission of sperms into the receptive megagametophyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275610
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of nitrogen limitation on the ultrastructure of the cyanobacterium Agmenellum quadruplicatum (1981)
    Springer
    Archives of microbiology 130 (1981), S. 204-212 
    Details
    ISSN: 1432-072X
    Keywords: Agmenellum quadruplicatum ; Nitrogen starvation ; Ultrastructure ; PATO poststain ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nitrogen limitation on the ultrastructure of the unicellular cyanobacterium, Agmenellum quadruplicatum, were studied by thin sectioning transmission electron microscopy. Nitrogen became limiting for growth 14–15 h after transfer to nitrogen-limiting medium, but cultures retained full viability for at least 45 h. The c-phycocyanin: chlorophyll a ratio and cellular nitrogen content of the culture dropped rapidly after 14–15 h, as a progressive deterioration of major cell structures took place. Phycobilisomes were degraded first, followed by ribosomes and, then, thylakoid membranes. These structures were virtually depleted from the cells within 26 h. Intracellular polysaccharide accumulated in place of the normal cell structures throughout this period. Nitrogen limitation did not affect polyphosphate bodies, carboxysomes, lipid granules, the cell envelope, or the extra-cellular glycocalyx. All of the ultrastructural changes resulting from nitrogen limitation were reversed upon addition of nitrate to a starved culture. Most cell structures were restored within 3 h, and restoration was complete within 9 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00459520
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  • 3
    Electronic Resource
    Electronic Resource
    Cross-inoculation specificity ofPsophocarpus tetragonolobus (L.) DC (1981)
    Springer
    Plant and soil 60 (1981), S. 139-142 
    Details
    ISSN: 1573-5036
    Keywords: Legumes ; Nitrogen fixation ; Nodulation ; Winged beans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Only legumes of the cowpea cross-inoculation group, including the winged bean (Psophocarpus tetragonolobus) were found to form nodules in a temperate zone soil with no previous history of legume cropping. Isolates from root nodules from uninoculated winged beans grown in the field only nodulated legumes in the cowpea cross-inoculation group.Rhizobium japonicum formed ineffective nodules with the winged bean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02377119
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructure of differentiating preameloblasts from tooth germs of the permanent dentition ofMacaca mulatta andMacaca arctoides (1981)
    Springer
    Calcified tissue international 33 (1981), S. 603-618 
    Details
    ISSN: 1432-0827
    Keywords: Preameloblasts ; Tooth germs ; Monkey ; Enamel ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cytodifferentiation of inner enamel epithelium and the adjacent connective tissue from the tip of the cervical loop to the initiation of enamel elaboration in twoMacaca species was examined. Ten- to twelve-month-old specimens were fixed by perfusion and the permanent tooth buds were prepared for transmission electron microscopy. At the cervical loop proper, inner enamel epithelium cells have lobed nuclei, a paucity of cytoplasm, and wide extracellular spaces; the basal lamina facing the dental papilla is straight. With increasing distance from the tip of the cervical loop, the following changes occur gradually: (a) preameloblasts elongate from 15 to 45 µm, and their organelles, particularly mitochondria and profiles of rough endoplasmic reticulum, become more numerous; (b) extracellular spaces decrease between preameloblasts starting at the basal (infranuclear) end; (c) the basement membrane becomes convoluted and associated with aperiodic fibers; (d) preodontoblast projections penetrate the aperiodic fibers; (e) collagen fibers subjacent to the basement membrane increase in density, with particularly thick fibers paralleling the aperiodic fibers. These modifications occur within three-fourths of the distance from the tip of the cervical loop to the mineralization front. The condensation of preodontoblasts is followed immediately by predentin synthesis. Concomitantly, the basement membrane breaks down and the aperiodic fibers are engulfed by preameloblasts. Preameloblast projections penetrate junctional predentin, contact mineralized dentin, and enamel synthesis ensues. At this stage the ameloblast is 45 µm long, the nucleus is central or basal, the Golgi apparatus has migrated apically, but the Tomes' process has not yet formed. The results indicate that odontogenesis inMacaca monkeys more closely resembles human odontogenesis than does that in the murine rodents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409498
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  • 5
    Electronic Resource
    Electronic Resource
    15N2 Incorporation and metabolism in the lichen Peltigera aphthosa Willd (1981)
    Springer
    Planta 152 (1981), S. 544-552 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Lichens ; Nitrogen fixation ; Peltigera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Nostoc in the cephalodia of the lichen Peltigera aphthosa Willd. fixed 15N2 and the bulk of the nitrogen fixed was continuously transferred from it to its eukaryotic partners (a fungus and a green alga, Coccomyxa sp.). Kinetic studies carried out over the first 30 min, after exposure of isolated cephalodia to 15N2, showed that highest initial 15N2-labelling was into NH 4 + . After 12 min little further increase in the NH 4 + label occurred while that in the amide group of glutamine and in glutamate continued to increase. The 15N-labelling of the amino group of glutamine and of aspartate increased more slowly, followed by an increase in the labelling of alanine. When total incorporation of 15N-label was calculated, the overall pattern was found to be rather similar except that, throughout the experiment, the total 15N incorporated into glutamate was about six times greater than that into the amide group of glutamine. Pulse chase experiments, in which 14N2 was added to cephalodia previously exposed to 15N2, showed that the NH 4 + pool rapidly became depleted of 15N-label, followed by decreases in the labelling of glutamate, the amide group of glutamine and aspartate. The 15N-labelling of alanine, however, continued to increase for a period. When isolated cephalodia were treated with L-methionine-SR-sulphoximine, an inhibitor of glutamine synthetase (EC 6.3.1.2), and azaserine, an inhibitor of glutamate synthase (EC 2.6.1.53), there was no detectable labelling in glutamine although the 15N-labelling of glutamate increased unimpaired. On treating the cephalodia with amino-oxyacetate, an inhibitor of aminotransferase activity, the alanine pool decreased. Evidence was obtained that glutamine synthetase and glutamate synthase were located in the Nostoc, and that glutamate dehydrogenase (EC 1.4.1.4) and various amino-transferases were located in the cephalodial fungus. Possible implications of these findings are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380825
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  • 6
    Electronic Resource
    Electronic Resource
    Relative levels of guanosine 5′-diphosphate 3′-diphosphate (ppGpp) in some N2 fixing bacteria during derepression and repression of nitrogenase (1981)
    Springer
    Archives of microbiology 128 (1981), S. 341-342 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Regulation ; Guanosine 5′-diphosphate 3′-diphosphate (ppGpp)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Addition of ammonium to N2 fixing cultures of Azotobacter vinelandii, Klebsiella pneumoniae and Clostridium pasteurianum rapidly reduced the intracellular levels of guanosine 5′-diphosphate 3′-diphosphate (ppGpp) by 70–90%. This change might reflect a regulatory role of ppGpp in nitrogen metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422542
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure of cell division and reproductive differentiation of male plants in theFlorideophyceae (Rhodophyta). Mitosis inDasya baillouviana (1981)
    Springer
    Protoplasma 106 (1981), S. 329-341 
    Details
    ISSN: 1615-6102
    Keywords: Dasya ; Mitosis ; Rhodophyta ; Spermatangia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitosis in the marine red algaDasya baillouviana (Ceramiales, Florideophyceae) was observed with the electron microscope. Most details of the process are quite similar to those observed in the other macroscopic red algae studied to date. However, some minor variations were noted. At late prophase a very small nuclear envelope protrusion (NEP) is formed at each division pole subjacent to the “nucleus associated organelle” known as the polar ring (PR) and 2–3 cisternae of perinuclear endoplasmic reticulum (PER) are commonly present during metaphase-anaphase. In contrast, in the other florideophycean algae where mitosis has been reported, a prominent NEP is present at late prophase (McDonald personal communication,Scott et al. 1980) and only a single cisterna of PER is observed. Additionally, during mid-late interphase and in mitotically-quiescent cells ofDasya, a single cisterna of smooth-surfaced ER is always juxtaposed with each PR. The possible significance of PER in theFlorideophyceae and other multinucleate organisms is discussed as well as the likely functions of spindle-associated smooth ER. It is suggested that ultrastructural features of mitosis should be useful as criteria to aid in the interpretation of the phylogeny of red algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275563
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  • 8
    Electronic Resource
    Electronic Resource
    Reduction of the nodulation barrier inMedicago laciniata by alteration of the root temperature (1981)
    Springer
    Plant and soil 61 (1981), S. 93-111 
    Details
    ISSN: 1573-5036
    Keywords: Ineffective nodules ; Medicago laciniata ; Nitrogen fixation ; Nodulation ; Root temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Medicago laciniata, an annual leguminous plant of Saharo-Sindian origin, is particularly refractory to root nodulation by most strains ofRhizobium meliloti. Using a series of such bacterial strains belonging to the 8 groups of Brockwell and Hely, and a variety of environmental conditions, it was noted that several normally non-nodulating strains (at 20°C) produced ineffective nodules at root temperatures of 24°C to 28°C. Nodulation at 20°C failed to occur in the presence of a wide variety of test compounds and physical conditions. No phytoalexins or anti-Rhizobium growth inhibitors were isolated from inoculated root tissue at any temperature. Temperature shift experiments indicated no infection of the root hairs at 20°C, and infection threads produced at the permissive root temperature failed to elongate after transfer to 20°C. However, if meristematic activity had been initiated in the inner root-cortical cells as a result of infection thread penetration at 28°C, no blockage of nodule maturation occurred upon subsequent transfer to 20°C root temperature. Nodules produced at 28°C were completely devoid of nitrogenase activity, although the apical (but not the distal) regions contained normal-appearing bacteriods, surrounded by enclosing membranes, and possessed a fully functional leghaemoglobin. A shortage of metabolic energy did not appear to be involved in the ineffective response. A hypothesis to explain the nodulation phenomenon observed was based on the observation in the roots of 2 factors present at 20°C but not at 28°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277367
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  • 9
    Electronic Resource
    Electronic Resource
    Respiration and nitrogen fixation in nodulated roots of soya bean and pea (1981)
    Springer
    Plant and soil 61 (1981), S. 135-143 
    Details
    ISSN: 1573-5036
    Keywords: Hydrogen ; Nitrogen fixation ; Nodulated roots ; Pea ; Respiration ; Soya bean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Oxygen uptake, carbon dioxide evolution and nitrogenase activity, measured either as hydrogen evolution (under argon 80%, oxygen 20%) or as the reduction of acetylene to ethylene, were assayed over the same time period by a direct mass-spectrometric method. When carbon dioxide evolution was used to estimate carbohydrate consumption, the results agreed with other work on whole plants. The RQ values obtained in these experiments were always less than 1.0 and thus the carbohydrate consumption calculated from oxygen uptake suggests that previous estimates, using carbon dioxide evolution as a measure of the cost of nitrogen fixation may be underestimates. Lag periods observed in the reduction of acetylene to ethylene suggest that there is a resistance to diffusion of gases in the root nodules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277370
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of inoculation on yield ofAlnus glutinosa in the Netherlands (1981)
    Springer
    Plant and soil 61 (1981), S. 189-202 
    Details
    ISSN: 1573-5036
    Keywords: Actinomycete symbiosis ; Alder ; Alnus glutinosa ; Endophyte ; Farmyard manure ; Forestry ; Frankia ; Inoculation ; Nitrogen fixation ; Nodulation ; Root nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The occurrence and the infectivity of Frankia, the root-nodule endophyte ofAlnus glutinosa, were studied in different kinds of soil in the Netherlands. Both field and pot experiments indicated that many soils, on which alders have not been grown before, had low numbers of endogenous Frankia or none at all. Inoculation of these soils usually enhanced growth and nodulation of alders. The effect of fertilizer treatments on growth and nodulation ofA. glutinosa were studied in experimental plots. Alders grown in sandy soils, dressed with farmyard manure had the highest yield and the most nodules. The influence of inoculation with homogenates of Sp(+) and Sp(−) nodules and with a pure culture of Frankia AvcIl were studied in pot experiments. The quantity of different kinds of inoculum needed to obtain good growth and nodulation of alder was estimated. The results indicated that addition of a nodule homogenate of 90 g fresh AvcIl Sp(+) nodules is sufficient to inoculate one hectare of nursery soil to produce 10 nodules per plant, while a thousand times larger amount of inoculum is necessary when Sp(−) nodules are used. The limitations and the potentials of using nodule homogenates and pure cultures of Frankia for inoculation in forestry are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277374
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