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11.
Fritz-Rudolf Averdieck 《Hydrobiologia》1986,143(1):407-410
The Duvensee originated before the Alleroed in the Late Glacial, and had its largest areal coverage during the Preboreal. After the lake retreat, which began in early Boreal times, the marginal shore areas and nearshore islands were repeatedly inhabited by man in the early Mesolithicum. Archaeological excavations of human settlements and pollen analyses of sediment cores show evidence of lake level fluctuations in the ensuing period. The results disclose that shallow water sediments such as lake marls, algal muds and coarse detrital gyttjas predominate in the sequence. In keeping with the shallow water conditions, strong lateral facies changes were observed in the cores. The early Holocene deposits have almost the same thickness irrespective of their position in the shallow or deep parts of the lake basin. The subaerial exposure of the nearshore and island areas sometimes resulted in fern and reed peats. The last remnants of the lake, which was drained in 1850, lay in the marginal areas over shallow water sediments. 相似文献
12.
X-ray fluorescence spectrometry and atomic absorption spectrometry were used in a quantitative study of zinc, copper, and
magnesium in 71 postmortal human hearts. Samples were obtained from individuals who had demonstrated no previous clinical
or subsequent pathological findings of myocardial infarction and from victims of a recent or an old infarction. A significant
difference (p<0.001) in the elemental levels was observed between the noninfarct and the recent infarct groups. The noninfarct group had
higher cardiac levels of all three elements. However, the difference in elemental concentrations between the noninfarct and
the old-infarct groups was not significant. Cardiac levels of zinc (p<0.001) and copper (p<0.01) were significantly greater in the old-infarct group than in the recent-infarct group. Magnesium levels were higher
in the recent-and-old-infarct group than in the recent infarct group (p<0.01). It is possible that the elements are redistributed during myocardial infarction, and that uptake of these elements
(from the serum pool) by the heart may be important in maintaining myocardial integrity and function. 相似文献
13.
Eviatar Nevo Zeev Gerechter-Amitai Avigdor Beiles Edward M. Golenberg 《Plant Systematics and Evolution》1986,153(1-2):13-30
From 114 accessions of wild emmer wheat from 11 sites in Israel, known for their allozymic variation (Nevo & al. 1982), individual genotypes were tested for resistance to one isolate of stripe rust both in the seedling stage in a growth chamber and in the adult plant stage in the field. The results indicate that resistance to stripe rust in seedlings and adults are significantly correlated (rs = 0.40, p < 0.001). Genetic polymorphisms of resistance to stripe rust vary geographically and are predictable by climatic, as well as allozymic markers. Three variable combinations of rainfall, evaporation, and temperature explain significantly 0.40–0.53 of the spatial variance in disease resistance to stripe rust, suggesting the operation of natural selection. Several allozyme genotypes are significantly associated with disease resistance. We conclude that natural populations of wild emmer wheat in Israel contain large amounts of disease resistance genes. These populations could be effectively screened and then utilized by the phytopathologist for identifying resistant genotypes and producing new resistant cultivars.Patterns of Resistance of Wild Wheat to Pathogens in Israel II. 相似文献
14.
The effects of light-induced non-photochemical quenching on the minimal Fo, and variable Fv, fluorescence emissions at 690 and 730 nm in leaves were determined. Non-photochemical quenching of Fo, but not Fv, was found to be dependent upon the wavelength of emission, and was greater at 690 nm than at 730 nm. For emission at 730, compared to at 690 nm, approx. 30% of Fo was not affected by non-photochemical quenching processes in leaves of C3 plants; in maize leaves this was found to be approx. 50%. The data indicate that a substantial proportion of the pigments contributing to Fo emission at 730 nm are not quenched by light-induced, non-photochemical quenching processes and that there are large differences in the pigment matrices contributing to Fo and Fv emissions at 730 nm, compared to those at 690 nm. These findings have important implications for the accurate estimation and interpretation of non-photochemical quenching of fluorescence parameters and their use in the calculation of photochemical efficiencies in leaves. Measurements of fluorescence emissions at wavelengths above 700 nm are likely to give rise to significant errors when used for determinations of photochemical and non-photochemical quenching parameters. 相似文献
15.
Summary Facultative paedomorphosis in salamanders occurs when larvae respond to varying environmental conditions by either metamorphosing into terrestrial metamorphic adults or retaining their larval morphology to become sexually mature paedomorphic adults. Several hypotheses have been proposed for the evolutionary maintenance of this environmentally induced dimorphism, but few data are available to assess them adequately. We studied a montane population of the tiger salamander,Ambystoma tigrinum nebulosum, and measured the adult growth rate and body condition across three growing seasons to assess the relative costs and benefits of each morph. Metamorphic adults grew more than paedomorphic adults in terms of snout—vent length across years and in weight within years. Dietary analyses and foraging experiments revealed some of the proximate factors that may underlie these differential growth patterns. Across all prey, metamorphs had significantly higher biomass and calories per stomach sample than paedomorphs. Metamorphic diets primarily consisted of the fairy shrimpBranchinecta coloradensis, whereas paedomorphic diets contained a variety of benthic and terrestrial invertebrates. Foraging experiments revealed that both morphs are more successful at capturing fairy shrimp relative to other prey types and both show high electivity toward this prey. However, fairy shrimp occurred only in non-permanent ponds and thus are inaccessible to paedomorphs, which can survive only in permanent ponds. Paedomorphs also experience higher levels of intraspecific competition with large larvae in permanent ponds than metamorphs do in non-permanent ponds. Thus, metamorphs obtain a growth advantage over paedomorphs by foraging in non-permanent ponds that contain fairy shrimp and have reduced intraspecific competition. These results suggest that paedomorphs should have decreased fitness relative to metamorphs, primarily because metamorphs can move into the best habitats for growth. The net fitness effect of morph-specific differences in dispersal depend on whether there are trade-offs with other life history traits. Nonetheless, because the relative benefit of metamorph dispersal will change with environmental conditions in permanent ponds and the surrounding habitat, the relative fitness payoff to each morph should track changes in the environment. Thus, facultative paedomorphosis may be maintained in part by variable, environmentally-specific fitness payoffs to each morph. 相似文献
16.
Anders Sonesson Erik Jantzen Torill Tangen Ulrich Zähringer 《Archives of microbiology》1994,162(4):215-221
Lipopolysaccharides (LPS) from Legionella bozemanii serogroup 1 and Legionella longbeachae serogroup 1 were subjected to chemical analyses. The lipid A part of both LPSs contained 2,3-dideoxy-2,3-diamino-d-glucose as major constituents and d-glucosamine and glycerol as minor constituents of the sugar backbone structure. Both LPSs exhibited a very complex fatty acid composition. Twenty amide-linked 3-hydroxy fatty acids were detected in LPS of L. longbeachae, whereas seventeen were encountered in LPS of L. bozemanii. Both LPSs contained nine ester-linked nonhydroxy fatty acids and the unique long-chain fatty acids 27-oxo-octacosanoic acid, 29-oxotriacontanoic acid, heptacosane-1,27-dioic acid and nonacosane-1,29-dioic acid. SDS-PAGE showed that L. bozemanii produced smooth-form LPS, whereas L. longbeachae LPS was mainly of the R-type. Composition analyses were in accordance with these electrophoretic patterns. d-Quinovosamine and l-fucosamine constituted 80 mol% of the polysaccharide part of L. bozemanii LPS. Other sugars identified were d-glucosamine, d-mannose, d-glucose, l-rhamnose, d-glycero-d-manno-heptose, l-glycero-d-mannoheptose, 2-keto-3-deoxy-octonic acid and glycerol. The polysaccharide chain from LPS of L. longbeachae appeared to be shorter, but composed of the same sugars except l-fucosamine. Both LPSs contained glycerol phosphate and glucosamine phosphate and L. longbeachae LPS contained in addition glucose phosphate.Abbreviations
EI
Electron impact
-
GlcN3N
2,3-Diamino-2,3-dideoxy-d-glucose
-
HPAEC
High pH anion-exchange chromatography
-
Kdo
2-Keto-3-deoxy-octonic acid
-
LPS
Lipopolysaccharide
-
PCP
Phenol/chloroform/petroleum ether solvent
-
PED
Pulsed electrochemical detection
-
PS
Polysaccharide
-
TFA
Trifluoroacetyl
-
TMS
Trimethylsilyl 相似文献
17.
18.
H. J. PEAT A. H. FITTER 《Biological journal of the Linnean Society. Linnean Society of London》1994,52(4):377-393
The distribution of stomata over both leaf surfaces may affect both the photosynthetic rate and water use efficiency of species, implying that species with different photosynthetic and water requirements may also have different stomatal distributions. A database containing data on the distribution of stomata on the leaves of 469 British plant species was used to look for relationships between stomatal distribution (including both location on the leaf and density) and both habitat and morphological variables. Statistical models were applied to the data that minimized any effects that phylogenetic constraints may have had on the data.
Hypostomaty is common in woody species, species which typically occur in shaded habitats and species with large or glabrous leaves. Amphistomaty, however, predominates in species which occur in non-shaded habitats, species with small, dissected or hairy leaves, and in annual species. Amphistomaty, therefore, tends to occur in species where CO2 may be limiting photosynthesis (unshaded environments), or where there are structures to prevent water loss from the leaf (e.g. hairs). Hypostomaty, however, occurs in slow-growing species (e.g. trees), species with leaves which have large boundary layers (large or entire leaves) and in species where CO2 is unlikely to limit photosynthesis (shaded habitats). 相似文献
Hypostomaty is common in woody species, species which typically occur in shaded habitats and species with large or glabrous leaves. Amphistomaty, however, predominates in species which occur in non-shaded habitats, species with small, dissected or hairy leaves, and in annual species. Amphistomaty, therefore, tends to occur in species where CO
19.
20.
C. Baroni Urbani 《Insectes Sociaux》1993,40(3):233-260
Summary Three alternative hypotheses about the evolution of recruitment behaviour in ants, based on accounts in the literature, are compared by means of a cladistic analysis. The three hypotheses are the following:Hypothesis 1. Increasingly efficient recruitment behaviours exhibited by different ant species have been shaped by or are correlated with ant phylogeny.Hypothesis 2. Increasingly efficient recruitment behaviours represent necessary evolutionary steps independently followed during the evolution of different ant clades.Hypothesis 3. Differently efficient recruitment behaviours have been selected in a convergent way among different species by similar population/environmental constraints.In a first stage of the analysis, these hypotheses have been compared in terms of parsimony (i.e. in terms of tree length = TL) of alternative cladograms based on recruitment behaviour only. The analysis gave the following results: Hypothesis 1, TL = 4; Hypothesis 2, TL = 18; Hypothesis 3, TL = 11. At least in terms of parsimony, hence, Hypothesis 1 appears to be the best. This hypothesis, however, cannot be retained for its total lack of congruence with current views on ant phylogeny. Among the remaining two hypotheses, Hypothesis 3 is again much (ca. 40%) more parsimonious than Hypothesis 2, but the retention index for recruitment behaviour on the relative cladogram is 0.2 as compared with 0.7 for Hypothesis 2. Practically, this implies biologically very implausible behavioural evolution indicated by very improbable ancestors for the species included in the analysis. In the case of recruitment evolution the biological credibility of each hypothesis is inversely proportional to its parsimony.The three hypotheses on the evolution of recruitment behaviour are compared again taking into account the morphological and behavioural correlates of recruitment. The results confirm those obtained by simple cladistic analysis of behaviour alone, namely that an obligatory (i. e. neither reversible nor random) increase in recruitment efficiency has been repeatedly selected within different ant clades. Inclusion of the recruitment correlates allows, in addition, a more precise formulation of the implications of each hypothesis and a tentative test of two other alternatives deduced from the literature. Most papers dealing with recruitment assume this behaviour to be controlled by a single gland, while at least two experimental analyses show that more than one gland is likely to be involved as behavioural releaser. A cladistic approach allowed testing of the following two adaptational hypotheses: A) Synergic behavioural control by several glands, allowing shift of the dominant role from one gland to another. B) Single gland control, making improbable the replacement of one gland by another that performs the same function. The results of the analysis appear to favour alternative A slightly, though neither alternative results in implausible evolutionary paths.It is stressed that parsimony remains the sole decisional criterion when no other criteria are available but it can by no way be preferred to the slightest trace of biological common sense. 相似文献