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  • 11
    Electronic Resource
    Electronic Resource
    The conversion of mevalonic acid into gibberellin A12-aldehyde in a cell-free system from Cucurbita pepo (1972)
    Springer
    Planta 102 (1972), S. 261-271 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cell-free system prepared from immature seed of Cucurbita pepo incorporates the label from mevalonate-2-14C into ent-kaur-16-en-19-oic acid (I), ent-7α-hydroxy-kaur-16-en-19-oic acid (II), and ent-gibberell-16-en-7-al-19-oic acid (III) (gibberellin A12-aldehyde). The products were identified by gas liquid chromatography and by combined gas chromatography-mass spectrometry of the methylated and trimethylsilylated fractions. The radioactivity of the compounds was established by recrystallisation to constant specific radioactivity. Gibberellin A12 (IV), also detected in the system after incubation by combined gas chromatographymass spectrometry may be an artefact, derived from gibberellin A12-aldehyde by a non-enzymatic conversion. With gibberellin A12-aldehyde, the cell-free biosynthesis of an ent-gibberellane has been achieved for the first time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386896
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  • 12
    Electronic Resource
    Electronic Resource
    Translocation and loss of phosphate along roots of wheat seedlings (1970)
    Springer
    Planta 93 (1970), S. 15-25 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sites of phosphate uptake, translocation and loss along sterile roots of 5-day-old wheat seedlings were obtained using an automatic scanning method. Highest uptake occurred in the apical centimetre of the primary root and in the lateral root zone although appreciable uptake occurred along the whole of the root. 68% of absorbed phosphate was translocated from the apex, 84% from the midroot portion and 87% from the lateral root zone after 24 hr. Profuse production of lateral roots is seen as important in phosphate uptake and translocation. Losses of absorbed phosphate from root to solution were small and the patterns of such losses along the root corresponded with the patterns of uptake by the root. Patterns of net flux of phosphate along the root are likely to be identical with those for influx. Patterns of phosphate loss along the root are in marked contrast to those reported for chloride efflux and loss of organic materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00387648
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  • 13
    Electronic Resource
    Electronic Resource
    Inhibitor content of phloem and xylem sap obtained from willow (Salix viminalis L.) entering dormancy (1968)
    Springer
    Planta 81 (1968), S. 64-70 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It is shown that there is one growth inhibitor in the phloem sap and two in the xylem sap of willow (S. viminalis L.). The concentration of the inhibitor in the phloem sap, (+)-abscisic acid, increases as the plants enter dormancy. This is also shown for (+)-abscisic acid in the xylem sap, but the concentration of the second inhibitor decreases in a reciprocal manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385515
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  • 14
    Electronic Resource
    Electronic Resource
    The UG2-Merensky Reef interval of the Bushveld Complex northwest of Pretoria (1996)
    Springer
    Mineralium deposita 31 (1996), S. 386-393 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Northwest of Pretoria, the UG2-Merensky Reef interval overlies a Critical Zone-Lower Zone sequence that contains numerous large blocks of floor material. Nevertheless, individual layers can be correlated with equivalent units at Crocodile River mine, the Rustenburg, Impala, Union, and Amandelbult sections. Concentrations of platinum-group elements in two borehole intersections of the UG2 chromitite are 4 ppm over 1.2 m and 2.4 ppm over 2.2 m. Therefore, bulk PGE levels appear to be only moderately lower than those at Western Platinum mine. This renders models explaining PGE enrichment by upward percolating melt or fluids problematic. The Merensky Reef, although containing sulphides, is only weakly mineralized with PGE (0.6 ppm). The UG2 pyroxenite is separated from the UG2 chromitite by a 15 m noritic layer. The introduction of feldspathic cumulates between two units that elsewhere directly overly each other may be explained by the more evolved composition of resident magma in those parts of the chamber distally located with regard to a major feeder zone at Union Section. It also suggests that the UG2 unit is a multiple rather than a single cyclic unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189186
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  • 15
    Electronic Resource
    Electronic Resource
    The UG2–Merensky Reef interval of the Bushveld Complex northwest of Pretoria (1996)
    Springer
    Mineralium deposita 31 (1996), S. 386-393 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract.  Northwest of Pretoria, the UG2–Merensky Reef interval overlies a Critical Zone–Lower Zone sequence that contains numerous large blocks of floor material. Nevertheless, individual layers can be correlated with equivalent units at Crocodile River mine, the Rustenburg, Impala, Union, and Amandelbult sections. Concentrations of platinum-group elements in two borehole intersections of the UG2 chromitite are 4 ppm over 1.2 m and 2.4 ppm over 2.2 m. Therefore, bulk PGE levels appear to be only moderately lower than those at Western Platinum mine. This renders models explaining PGE enrichment by upward percolating melt or fluids problematic. The Merensky Reef, although containing sulphides, is only weakly mineralized with PGE (0.6 ppm). The UG2 pyroxenite is separated from the UG2 chromitite by a 15 m noritic layer. The introduction of feldspathic cumulates between two units that elsewhere directly overly each other may be explained by the more evolved composition of resident magma in those parts of the chamber distally located with regard to a major feeder zone at Union Section. It also suggests that the UG2 unit is a multiple rather than a single cyclic unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001260050046
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  • 16
    Electronic Resource
    Electronic Resource
    Demographic composition of the feeding population of juvenile loggerhead sea turtles (Caretta caretta) off Charleston, South Carolina: evidence from mitochondrial DNA markers (1995)
    Springer
    Marine biology 123 (1995), S. 869-874 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To determine the origin of juvenile loggerhead turtles (Caretta caretta) that occupy the Charleston Harbor Entrance Channel at Charleston, South Carolina, USA, mitochondrial DNA restriction-fragment length polymorphisms from this feeding population were compared to haplotypes from candidate nesting populations. Previous studies have defined two major nesting populations in the southeastern USA, one corresponding to Florida and the other to Georgia/South Carolina. These nesting populations are distinguished by both unique haplotypes and frequency distributions of common haplotypes. The frequency distribution of haplotypes in the juvenile feeding-ground population was significantly different from both nesting populations, implying that the feeding aggregate is drawn from two or more nesting populations. Assuming that these turtles are derived exclusively from rookeries in the southeastern USA, a maximum likelihood estimator indicates that approximately half are from the Florida rookery and half are from the northern (Georgia/South Carolina) rookery complex. Because 91% of nesting in the southeastern USA occurs in Florida rookeries and 8% in the northern complex, the 50:50 ratio indicates that juvenile turtles from Georgia and South Carolina tend to feed preferentially near their respective rookery locations. Human encroachment on this feeding habitat may pose an especially high risk to the smaller Georgia/South Carolina rookeries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349132
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  • 17
    Electronic Resource
    Electronic Resource
    Genetic composition of a green turtle (Chelonia mydas) feeding ground population: evidence for multiple origins (1998)
    Springer
    Marine biology 130 (1998), S. 345-352 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Migratory marine turtles are extremely difficult to track between their feeding and nesting areas, and the link between juvenile and adult habitats is generally unknown. To assess the composition of a feeding ground (FG) population of juvenile green turtles (Cheloniamydas Linnaeus), mitochondrial DNA control region sequences were examined in 80 post-pelagic individuals (straight carapace length = 31 to 67 cm) sampled in September 1992 from Great Inagua, Bahamas, and compared to those of 194 individuals from nine Atlantic and Mediterranean nesting colonies. Evidence from genetic markers, haplotype frequencies, and maximum likelihood (ML) analyses are concordant in indicating that multiple colonies contribute to the Bahamian FG population. ML analyses suggested that most Bahamian FG juveniles originated in the western (79.5%) and eastern (12.9%) Caribbean regions, and these proportions are roughly comparable to the size of candidate rookeries. These data support a life-cycle model in which individuals become pooled in post-hatchling (pelagic) and juvenile (benthic) habitats as a consequence of ocean currents and movement among FGs. A substantial harvest of immature turtles on their feeding pastures will influence the reproductive success of contributing nesting populations over a wide geographic scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050254
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  • 18
    Electronic Resource
    Electronic Resource
    Density-gradient centrifugation as an aid to sorting planktonic organisms. I. Gradient materials (1972)
    Springer
    Marine biology 14 (1972), S. 242-247 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fish eggs and larvae can be separated from invertebrate zooplankton by isopycnic centrifugation in gradients of sucrose or silica. Preserved samples of invertebrate zooplankton, fish eggs, and fish larvae, representing a typical assortment of marine plankton, were layered over linear gradients of 25 to 60% w/w (weight/weight) sucrose or 0 to 15% w/w silica (as Ludox AM) in 100 c3 swinging buckets, and centrifuged for 1 h at 1000 rpm (revs per minute). In sucrose gradients, the invertebrate zooplankton were confined to the two ends of the gradient, while 85% of the fish eggs were recovered from an intermediate zone (27.5 to 55% w/w). In Ludox AM, the fish eggs banded in a narrow region between 2 and 3% w/w, while fish larvae banded at the bottom of the gradient between 10 and 14% w/w. Of the 6 dominant classes of zooplankton, only Salpa overlapped appreciably with the fish eggs and none overlapped with the fish larvae. Of the gradient materials tested, Ludox AM offers the most advantages; sucrose may also be useful for subfractionation. Gradients of sodium bromide and dextran have been found to be totally unsuitable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348286
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  • 19
    Electronic Resource
    Electronic Resource
    Population structure of loggerhead turtle (Carettacaretta) nesting colonies in the Atlantic and Mediterranean as inferred from mitochondrial DNA control region sequences (1998)
    Springer
    Marine biology 130 (1998), S. 567-575 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial (mt) DNA control region sequences were analyzed for 249 Atlantic and Mediterranean loggerhead turtles (Carettacaretta Linnaeus, 1758) to elucidate nesting population structure and phylogeographic patterns. Ten haplotypes were resolved among individuals sampled between 1987 and 1993, from ten major loggerhead nesting areas in the region. Two distinct phylogenetic lineages were distinguished, separated by an average of 5.1% sequence divergence. Haplotype frequency comparisons between pairs of populations showed significant differentiation between most regional nesting aggregates and revealed six demographically independent groups, corresponding to nesting beaches from: (1) North Carolina, South Carolina, Georgia and northeast Florida, USA; (2) southern Florida, USA; (3) northwest Florida, USA; (4) Quintana Roo, Mexico; (5) Bahia, Brazil; and (6) Peloponnesus Island, Greece. The distribution of mtDNA haplotypes is consistent with a natal homing scenario, in which nesting colonies separated by a few hundred kilometers represent isolated reproductive aggregates. However, a strong exception to this pattern was observed in the first group defined by mtDNA data (North Carolina to northeast Florida), which included samples from four nesting locations spread across thousands of kilometers of coastline. These locations were characterized by a single haplotype in 104 out of 105 samples, providing inadequate resolution of population divisions. In view of the subdivisions observed elsewhere, we attribute the lack of differentiation between North Carolina and northeast Florida to recent colonization of these warm temperate coastlines (after the Wisconsin glaciation) not to ongoing gene flow among spatially distinct nesting locations. The relationships among observed haplotypes suggest a biogeographic scenario defined by climate, natal homing, and rare dispersal events. The redefined relationships among nesting aggregations in the western Atlantic region (southeastern USA and adjacent Mexico) prompt a reconsideration of management strategies for nesting populations and corresponding habitats in this region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050278
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  • 20
    Electronic Resource
    Electronic Resource
    Insect photoperiodism: An hourglass measures photoperiodic time inOstrinia nubilalis (1976)
    Springer
    Journal of comparative physiology 111 (1976), S. 249-259 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The European corn borer (Ostrinia nubilalis) diapauses as a last instar larva. Both induction and termination of diapause are photoperiodically controlled. Larvae enter diapause (Fig. 1) when raised in light cycles containing 12 or 13 h of light per 24 h (LD 12∶12 or LD 13∶11). When placed in LD 16∶8, diapausing larvae undergo pupation and adult development (Fig. 2, 3). Long light cycle (T) experiments demonstrate that the timing mechanism involved in terminating diapause has the properties of an interval timer or hourglass mechanism (Fig. 4). Six inductive 8-h dark phases are necessary for optimal termination (Fig. 5), and they must be coupled with at least 4 h of light per cycle (Fig. 6). The circadian system inOstrinia is probably not involved in any way in this response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606467
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