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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Phytochemistry 30 (1991), S. 2127-2130 
    ISSN: 0031-9422
    Keywords: Compositae ; Helianthus annuus ; high oleic mutant ; microsomes ; oleate desaturase ; seeds ; sunflower ; temperature control.
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Phytochemistry 28 (1989), S. 2597-2600 
    ISSN: 0031-9422
    Keywords: Compositae ; Helianthus annuus ; fatty acid composition ; high oleic acid mutant. ; lipids ; seeds ; sunflower
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-0417
    Keywords: saline lakes ; stable isotope ; sedimentology ; mineralogy ; paleohydrology ; Altiplano ; Holocene ; Little Ice Age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The paleohydrological evolution of several high altitude, saline lakes located in the southernmost Altiplano (El Peinado and San Francisco basins, Catamarca province, NW Argentina) was reconstructed applying sedimentological, geochemical and isotopic techniques. Several playa lakes from the San Francisco basin (26° 56′ S; 68° 08′ W, 3800-3900 m a.s.l.) show evidence of a recent raise in the watertable that led to modern deposition of carbonate and diatomaceous muds. A 2 m - long core from El Peinado Lake (26° 29′ 59′′ S, 68°05′ 32′′ W, 3820 m a.s.l.) consists of calcitic crusts (unit 3), overlaid by an alternation of macrophyte-rich and travertine clast- rich, laminated muds (unit 2), and topped by travertine facies (unit 1). This sedimentary sequence illustrates a paleohydrological evolution from a subaerial exposure (unit 3) to a high lake stand (unit 2), and a subsequent smaller decrease in lake level (unit 1). The δ13Corganic matterrecord also reflects the lake transgression between units 3 and 2. Although there is a general positive correlation between δ 18Ocarbonate and salinity proxies (Na, Li and B content), the large data dispersion indicates that other factors besides evaporation effects control chemical and isotopic composition of lakewater. Consequently, the oxygen isotopic composition cannot be interpreted exclusively as an indicator of salinity or evaporation ratio. The degassing of CO2 during groundwater discharge can explain the enriched δ13C values for primary carbonates precipitated. The carbon budget in these high altitude, saline lakes seems to be controlled by physical rather than biological processes.The Altiplano saline lakes contain records of environmental and climatic change, although accurate 14C dating of these lacustrine sediments is hindered by the scarcity of terrestrial organic material, and the large reservoir effects. Sedimentologic evidence, a 210Pb-based chronology, and a preliminary U/Th chronology indicate a very large reservoir effect in El Peinado, likely as a result of old groundwaters and large contributions of volcanic and geothermal 14C-free CO2 to the lake system. Alternative chronologies are needed to place these paleorecords in a reliable chronological framework. A period of increased water balance in the San Francisco basin ended at about 1660 ± 82 yr B.P. (calendar yr U/Th age), and would correlates with the humid phase between 3000 and 1800 yr B.P detected in other sites of the southern Altiplano. Both, 210Pb and preliminary U/Th dating favor a younger age for the paleohydrological changes in El Peinado. The arid period reflected by subaerial exposure and low lake levels in unit 3 would have ended with a large increase in effective moisture during the late 17th century. The increased lake level during deposition of unit 2 would represent the period between AD1650 - 1900, synchronous to the Little Ice Age. This chronological framework is coherent with other regional records that show an abrupt transition from more arid to more humid conditions in the early 17th century, and a change to modern conditions in the late 19th century. Although there are local differences, the Little Ice Age stands as a significant climatic event in the Andean Altiplano.
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  • 4
    ISSN: 1573-0417
    Keywords: sedimentology ; saline lake ; meromixis ; Northern Great Plains ; Holocene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Medicine lake is a small (about 1 km2), shallow (up to 10 m deep), saline (50–170 g l−1) and meromictic lake formed after the retreat of the Wisconsin ice in the north American Great Plains. Based on a detailed sedimentological analysis of cores, we describe and interpret 13 sedimentary subfacies grouped in 9 associations which characterize the following lacustrine subenvironments: clastic littoral (freshwater and saline), springs, microbial mats, bench slope, and pelagial (oxic, alternating oxic-anoxic, anoxic and hypersaline, and organic-dominated). Lateral distribution and vertical evolution of subfacies in our model are controlled by climate fluctuations, climate-related limnological parameters (lake level, TDS and brine composition, and redox conditions), and autocyclic processes (progressive infilling of the basin and higher sedimentation rate in the pclagial realm). Microbial and chemical processes govern deposition in this system, and meromixis plays a decisive role in lake dynamics. Phototropic bacterial plate communites at the chemocline dominated as pelagial organic producers during stable meromictic periods, whereas benthic microbial communities developed during mixed water periods. Water stratification during the Holocene was mainly controlled by three parameters: 1) basin morphometry, 2) lake level, and 3) differences in TDS values between mixolimnion and monimolimnion waters. Sedimentary facies analyses is a powerful descriptive and interpretative tool that greatly contributes to deciphering the high resolution paleoenvironmental information archived in lake sequences. Depositional and paleoenvironmental models provide a dynamic framework for integrating paleolimnological data and other proxy paleorecords. Medicine lake serves as a facies model for shallow, perennial hypersaline, meromictic lakes in modern and ancient lacustrine basins. The sediment sequence from Medicine lake cores is consistent with the general paleoclimatic evolution of the northern Great Plains since the retreat of ice sheets. Our study reveals a plethora of rapid fluctuations in the water cycle both during the middle and the late Holocene. These augment prior paleoclimate reconstructions based on diatom studies of the lower Holocene freshwater to saline transition and on pollen profiles which show little variability during the subsequent long prairie grass episode.
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  • 5
    ISSN: 1573-0417
    Keywords: Atacama ; Holocene ; limnogeology ; South America ; paleoclimatology ; lake sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sedimentological, mineralogical and geochemical analyses of sediment cores from 9 m-deep, saline Laguna Miscanti, Chile (23 ° 44′S, 67 °46′W, 4140 m a.s.l.) together with high-resolution seismic profiles provide a mid to late Holocene time series of regional environmental change in the Atacama Altiplano constrained by 210Pb and conventional 14C dating. The mid Holocene was the most arid interval since the last glacial maximum, as documented by subaerial exposure and formation of hardgrounds on a playa surface. Extremely low lake levels during the mid Holocene appear consistent with lower effective moisture recorded at other sites along the Altiplano and in the Amazon Basin. Termination of this arid period represented a major shift in the regional environmental dynamics and inaugurated modern atmospheric conditions. The cores show a progressive upward increase in effective moisture interrupted by numerous century-scale drier periods of various intensities and durations that characterize a fluctuating late Holocene climate. In spite of chronological uncertainties, the major environmental changes seem to correlate with the available paleorecords from the region providing a coherent account of effective moisture variability in the tropical highlands of South America.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5060
    Keywords: Helianthus annuus ; sunflower ; oleic acid content ; linoleic acid content ; genetical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sunflower lines breeding true for very high oleic acid content in their oil (average levels higher than 85%) were crossed with standard sunflower lines with mean oleic acid levels of 30%. Analysis of the oil of F1 seeds indicated dominance for high oleic levels and control of the genotype of the embryo. Segregating generations were obtained selfing heterozygous high oleic BCnF1 plants from several generations of a backcrossing program to incorporate the high oleic character to standard inbred lines and testcrossing these plants to low oleic material. Analysis of F2 and testcrossed seeds showed three kind of segregations, in both F2 and testcrossed populations, with different proportions of low, intermediate and high oleic types. Genetic analysis of these data supported the hypothesis, that the high oleic character is controlled by three dominant complementary genes OL1, OL2 and OL3. Additional data showing F1 seeds with intermediate oleic content and segregations for high oleic in progenies of intermediate types, suggest the presence of major factors modifying high oleic acid content.
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  • 7
    ISSN: 1573-5060
    Keywords: Helianthus annuus ; fatty acids ; palmitic acid ; X-ray mutagenesis ; seed oil ; sunflower
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A new sunflower mutant, CAS-12, was obtained, which has both high palmitic (≈30%) and high oleic acid contents, and also a substantial amount of palmitoleic acid (≈7%). The mutant was selected after X-ray irradiation of dry seeds of the inbred line BSD-2-423, which had normal palmitic (≈3%) and high oleic (≈88%) acid levels. The increase of palmitic and palmitoleic acids occurred at the expense of the oleic acid content, which decreased to around 55% in respect to the original line. Linoleic acid content is always under 5%. Palmitic and palmitoleic acid levels were similar to those of the high palmitic mutant CAS-5 obtained in a previous programme from a low oleic line isogenic to BSD-2-423 using a similar mutagenic treatment. In that previous programme we also selected three high stearic acid mutants using chemical mutagenic treatment on the same sunflower line (RDF-1-532). We attempted to obtain mutants in other lines but were unsuccessful. The isolation of similar mutants in isogenic parental lines illustrates the importance of the genetic background in the development of specific mutants with an altered seed oil fatty acid composition. The oil of this mutant will increase the range of potential uses of sunflower oil.
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