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  • Springer  (183)
  • American Society of Hematology
  • Annual Reviews
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal for general philosophy of science 21 (1990), S. 309-328 
    ISSN: 1572-8587
    Schlagwort(e): Evolution ; evolutionäre Erkenntnistheorie ; Organismus ; Autonomie ; Abbildungskritik
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Philosophie , Wissenschaftskunde und Wissenschaftsorganisation, Hochschul- und Universitätswesen, Museumswissenschaft
    Notizen: Summary The concept of evolutionary epistemology has been critically discussed by philosophers who have mainly pointed to unacceptable philosophical tenets (cf. Vittorio Hösle, this Journal, Vol. 19 (1988), pp. 348–377). However, as most philosophers are extremely reluctant to critically treat the biological theories on which the ideas of evolutionary epistemology are based, the invalid concepts of adaption escaped their critical scrutiny. Therefore the influence of preconceived biological theories on the biological basis of evolutionary epistemology and the distorting consequences on the philosophical level could not be elaborated. The following context sketches a new view of organismic reasoning and its impact on evolutionary aspects of epistemology. The basic theorem of adaptation is shown to be unacceptable and invalid if organisms are conceived as autonomous entities which can only evolve according to their specific internal organismic properties.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 9 (1990), S. 110-118 
    ISSN: 1432-0789
    Schlagwort(e): Kuehneltiella terricola gen. nov., sp. nov. ; Soil ciliates ; Colpodidae ; Systematics ; Evolution ; Australia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The morphology and biology of the colpodid ciliate Kuehneltiella terricola gen. nov., sp. nov. has been investigated using living organisms, various silver impregnation methods, and scanning electron microscopy. The new species has been isolated in soil from central Australia and might be endemic to this continent. The new genus Kuehneltiella differs from its nearest relative, Bresslaua, in having a right oral polykinetid composed of a single row of dikinetids. A reinvestigation of Lynn's slides of Bresslaua insidiatrix showed that, contrary to the statement of Lynn (1979), this species has a typic colpodid right oral polykinetid, i.e., composed of many short, disordered kineties. A brief review of the literature suggests that simple, single-rowed, right oral polykinetids are apomorphic in the colpodids s. str. Further, this special character has obviously evolved independently several times within the class Colpodea and even within the colpodids s. str. An illustrated key to the genera of the family Colpodidae is provided.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 9 (1990), S. 95-100 
    ISSN: 1432-0789
    Schlagwort(e): Assulina-Valkanovia ; Testacea ; Polymorphism ; Genotypes ; Evolution ; Spruce forest ; Sphagnum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The taxonomy and evolution of the Assulina-Valkanovia complex were investigated in a spruce forest soil which included a Sphagnum plot (GDR, Thuringia). In both habitats Assulina muscorum occurred in two colour forms (brown and colourless) and four shapes. A quantified phenospectrum from Assulina muscorum was obtained. The four shapes were distributed differently between the brown and the colourless forms in Sphagnum and soil. The shell measurements showed statistically significant differences between the brown and the colourless forms. Even between the two brown populations there were some significant differences. Each of the four shape types of brown and of colourless Assulina can be kept in clonal cultures for some time. However, without selection, single cultures eventually revert to mixed types. The four shape types show different degrees of stability. These colour and shape forms are genotypes, which can also occur for short periods in the natural habitats. The brown populations in Sphagnum and in the soil were dominated by different shape types during the period of investigation. Valkanovia elegans cannot be distinguished from Assulina muscorum type 4, but Valkanovia can inhabit both upper and lower soil horizons, whereas Assulina and its forms lives exclusively in the upper horizon (litter). Valkanovia from the lower horizon is constant in clonal culture. The conclusion of the present investigation is that there are stable and unstable constellations within a changeable genome, which give asexual groups both a taxonomic structure and a continuum of forms. Selection can increase stability, by polygenic control of features.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Current genetics 17 (1990), S. 223-227 
    ISSN: 1432-0983
    Schlagwort(e): Orotidine-5′-phosphate decarboxylase ; Cephalosporium acremonium ; Recombinant DNA ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have cloned the Cephalosporium acremonium pyr4 gene by cross-hybridization with the equivalent gene from Neurospora crassa, the closest relative from which this gene is available. The C. acremonium pyr4 gene complements an E. coli pyrF mutant lacking orotidine-5′-phosphate decarboxylase (OMPdecase), and most probably does not contain introns. Maxicell analysis in E. coli shows that it encodes a 46 kDa polypeptide. The C. acremonium OMPdecase contains a highly conserved pentadecapeptide characteristic for this category of enzyme. Extensive sequence comparison suggests an important role of this region in enzymatic activity.
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  • 5
    ISSN: 1432-0983
    Schlagwort(e): Trypanosomes ; RNA polymerase ; Transcription ; Evolution ; Phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have sequenced the genes encoding te largest subunits of the three classes of DNA-dependent RNA polymerases of Trypanosoma brucei. The nucleotide and deduced amino acid sequences were compared and aligned with the corresponding sequences of other eukaryotes. Phylogenetic relationships were subsequently calculated with a distant matrix, a bootstrapped parsimony and a maximum-likelihood method. These independent calculations resulted in trees with very similar topologies. The analyses show that all the largest subunits of T. brucei are evolutionarily distant members within each of the three RNA polymerase classes. An early separation of the trypanosomal subunits from the eukaryotic lineage might from the fundamental basis for the unusual transcription process of this species. Finally, all dendrograms show a separate ramification for the largest subunit of RNA polymerase I, II and III. RNA polymerase II and/or III form a bifurcation with the archaebacterial lineage. RNA polymerase I, however, arises separately from the eubacterial β′ lineage. This suggests that the three eukaryotic RNA polymerase classes are not simply derived by two gene duplications of an ancestral gene with subsequent differentiation.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0983
    Schlagwort(e): Cyanophora paradoxa ; Ferredoxin-NADP+-oxidoreductase ; Protein-import ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cyanophora paradoxa is an important model organism for the study of the transition from endocytobiontic cyanobacteria to factual eukaryotic cell organelles. The cyanelles of these organisms possess cyanobacterial, as well as plastidic, characteristics. Although the transfer of cyanellar proteins from cytosolic into cyanellar space has been shown, the process of translocation of a known protein across the peptidoglycan layer and the envelope membranes has not been characterized. In this study we demonstrate that a specific and obligate cyanelle protein —Ferredoxin-NADP+-oxidoreductase (FNR) — is coded on the nuclear genome, synthesized on 80S ribosomes and transported from the eukaryotic cell compartment into the cyanelles of Cyanophora paradoxa, an original intracellular host-guest relation. These results indicate a gene transfer from guest to host genome and support the view that, in spite of their cyanobacterial origin, cyanelles have been evolved to cell organelles comparable to plastids.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 489-492 
    ISSN: 1432-1432
    Schlagwort(e): Actinomyces ; Phosphotransferase ; Aminoglycoside ; Phylogenetic tree ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The protein sequences of seven 3′-aminoglycoside phosphotransferases falling into the six identified types and three 6′-aminoglycoside phosphotransferases were analyzed to give a rooted phylogenetic tree. This tree supports the origin of these groups of enzymes in an ancestor closely related to the actinomycetes, and that horizontal transfer of the resistance genes occurred, possibly via transposons. The implications for genetic engineering of a novel antibiotic are discussed.
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  • 8
    ISSN: 1432-1432
    Schlagwort(e): Mitochondrial DNA ; Evolution ; Echinoderms ; Sea stars ; DNA sequence ; Mitochondrial proteins ; Mitochondrial tRNA genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have cloned and sequenced over 9 kb of the mitochondrial genome from the sea starPisaster ochraceus. Within a continuous 8.0-kb fragment are located the genes for NADH dehydrogenase subunits 1, 2, 3, and 4L (ND1, ND2, ND3, and ND4L), cytochrome oxidase subunits I, II, and III (COI, COII, and COIII), and adenosine triphosphatase subunits 6 and 8 (ATPase 6 and ATPase 8). This large fragment also contains a cluster of 13 tRNA genes between ND1 and COI as well as the genes for isoleucine tRNA between ND1 and ND2, arginine tRNA between COI and ND4L, lysine tRNA between COII and ATPase 8, and the serine (UCN) tRNA between COIII and ND3. The genes for the other five tRNAs lie outside this fragment. The gene for phenylalanine tRNA is located between cytochrome b and the 12S ribosomal genes. The genes for tRNAglu and tRNAthr are 3′ to the 12S ribosomal gene. The tRNAs for histidine and serine (AGN) are adjacent to each other and lie between ND4 and ND5. These data confirm the novel gene order in mitochondrial DNA (mtDNA) of sea stars and delineate additional distinctions between the sea star and other mtDNA molecules.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 68-75 
    ISSN: 1432-1432
    Schlagwort(e): DNA ; Genome size ; Repetitive DNA ; Amphibians ; Reptiles ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Many characters differentiate amphibian from reptilian genomes. The former have, on the average, larger and more variable genome sizes, a greater repetitive DNA percentage, and a higher interspersion level among DNAs with different degrees of repetitivity. Reptiles have more reduced and uniform genome sizes, a repetitive DNA percentage generally lower than 50%, and a lower interspersion level. Other differences can be observed in the chromosome banding and in the correlations between genome size and other morphometric and functional parameters of the cell. The differences found in amphibians and reptiles seem to indicate that in these two vertebrate classes there is a different tendency toward or tolerance of the accumulation and preservation of genetically dispensable DNA fractions. This might depend either on a different propensity toward genic amplification or on the appearance, in reptiles, of stricter and more efficient constraints regulating genome size.
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 133-141 
    ISSN: 1432-1432
    Schlagwort(e): Y-chromosome ; DNA ; Human ; Primate ; Evolution ; PUPPY sequence ; Alu element
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A Y-chromosomal DNA fragment has been isolated from a human Y-Charon 21A recombinant library. Evolutionary analysis of 1F5 indicates that the size and sequence of this fragment have been conserved in higher primates. Deletion mapping and in situ hybridization analysis have localized 1F5 to the middle euchromatic portion of the long arm of the human Y chromosome at Yq11.2. Sequence analysis revealed the presence of an atypical Alu element and two regions rich in polypyrimidine-polypurine residues.
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  • 11
    ISSN: 1432-1432
    Schlagwort(e): Bacteria ; Sugars ; Phosphotransferase system ; Transport proteins ; Evolution ; Sequence comparisons ; NADH dehydrogenase ; Mitochondria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The amino acid sequences of 15 sugar permeases of the bacterial phosphoenolpyruvatedependent phosphotransferase system (PTS) were divided into four homologous segments, and these segments were analyzed to give phylogenetic trees. The permease segments fell into four clusters: the lactose-cellobiose cluster, the fructose-mannitol cluster, the glucose-N-acetylglucosamine cluster, and the sucrose-β-glucoside cluster. Sequences of the glucitol and mannose permeases (clusters 5 and 6, respectively) were too dissimilar to establish homology with the other permeases, but short regions of statistically significant sequence similarities were noted. The functional and structural relationships of these permease segments are discussed. Some of the homologous PTS permeases were found to exhibit sufficient sequence similarity to subunits 4 and 5 of the eukaryotic mitochondrial NADH dehydrogenase complex to suggest homology. Moreover, subunits 4 and 5 of this complex appeared to be homologous to each other, suggesting that these PTS and mitochondrial proteins comprise a superfamily. The integral membrane subunits of the evolutionarily divergent mannose PTS permease, the P and M subunits, exhibited limited sequence similarity to subunit 6 of the mitochondrial F1F0-ATPase and subunit 5b of cytochrome oxidase, respectively. These results suggest that PTS sugar permeases and mitochondrial proton-translocating proteins may be related, although the possibility of convergent evolution cannot be ruled out.
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 60-71 
    ISSN: 1432-1432
    Schlagwort(e): Cysteine endopeptidase ; Cysteine proteinase ; Inhibitor ; Cystatin ; Kininogen ; Evolution ; Amino acid sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have examined the amino acid sequences of a number of proteins that have been suggested to be related to chicken cystatin, a protein from chicken egg white that inhibits cysteine proteinases. On the basis of statistical analysis, the following proteins were found to be members of the cystatin superfamily: human cystatin A, rat cystatin A(α), human cystatin B, rat cystatin B(β), rice cystatin, human cystatin C, ox colostrum cystatin, human cystatin S, human cystatin SA, human cystatin SN, chicken cystatin, puff adder cystatin, human kininogen, ox kininogen, rat kininogen, rat T-kininogens 1 and 2, human α2HS-glycoprotein, and human histidine-rich glycoprotein. Fibronectin is shown not to be a member of this superfamily, and the c-Ha-ras oncogene protein p21(Val-12) probably is not a member also. It was convenient to divide members of the superfamily into four types on the basis of the presence of one, two, or three copies of cystatin-like segments and the presence or absence of disulfide bonds. Evolutionary dendrograms were calculated by three methods, and from these we have constructed a scheme depicting the sequence of events in the evolution of these proteins. We suggest that about 1000 million years ago a precursor containing disulfide loops appeared, and that all disulfide-containing cystatins are derived from this. We follow the evolution of the proteins of the superfamily along four main lineages, with special attention to the part that duplication of segments has played in the development of the more complex molecules.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 424-431 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila melanogaster ; Evolution ; Hybrid dysgenesis ; I elements ; Transposons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary There are two categories of strains inDrosophila melanogaster with respect to the I-R system of hybrid dysgenesis. The inducer strains contain particular transposable elements named I factors. They are not present in the strains of the other category called reactive (R) strains. Defective I elements are present in the pericentromeric regions of both categories of strains. This last subfamily of I sequences has not yet been described in detail and little is known about its origin. In this paper, we report that the defective I elements display an average of 94% of sequence identity with each other and with the transposable I factor. The results suggest that they cannot be the progenitors of the present day I factors, but that each of these two subfamilies started to evolve independently several million years ago. Furthermore, the sequence comparison of these I elements with an active I factor fromDrosophila teissieri provides useful information about when the deleted I elements became immobilized.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 32 (1991), S. 296-303 
    ISSN: 1432-1432
    Schlagwort(e): Prebiotic chemistry ; Primordial soup ; Oparin hypothesis ; Evolution ; Impact catastrophism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In the traditional concept for the origin of life as proposed by Oparin and Haldane in the 1920s, prebiotic reactants became slowly concentrated in the primordial oceans and life evolved slowly from a series of highly protracted chemical reactions during the first billion years of Earth's history. However, chemical evolution may not have occurred continuously because planetesimals and asterioids impacted the Earth many times during the first billion years, may have sterilized the Earth, and required the process to start over. A rapid process of chemical evolution may have been required in order that life appeared at or before 3.5 billion years ago. Thus, a setting favoring rapid chemical evolution may be required. A chemical evolution hypothesis set forth by Woese in 1979 accomplished prebiotic reactions rapidly in droplets in giant atmospheric reflux columns. However, in 1985 Scherer raised a number of objections to Woese's hypothesis and concluded that it was not valid. We propose a mechanism for prebiotic chemistry in clouds that satisfies Scherer's concerns regarding the Woese hypothesis and includes advantageous droplet chemistry. Prebiotic reactants were supplied to the atmosphere by comets, meteorites, and interplanetary dust or synthesized in the atmosphere from simple compounds using energy sources such as ultraviolet light, corona discharge, or lightning. These prebiotic monomers would have first encountered moisture in cloud drops and precipitation. We propose that rapid prebiotic chemical evolution was facilitated on the primordial Earth by cycles of condensation and evaporation of cloud drops containing clay condensation nuclei and nonvolatile monomers. For example, amino acids supplied by, or synthesized during entry of, meteorites, comets, and interplanetary dust would have been scavenged by cloud drops containing clay condensation nuclei. Polymerization would have occurred within cloud systems during cycles of condensation, freezing, melting, and evaporation of cloud drops. We suggest that polymerization reactions occurred in the atmosphere as in the Woese hypothesis, but life originated in the ocean as in the Oparin-Haldane hypothesis. The rapidity with which chemical evolution could have occurred within clouds accommodates the time constraints suggested by recent astrophysical theories.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 32 (1991), S. 415-420 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila melanogaster ; Drosophila virilis ; mastermind ; Gene comparison ; Repetitive sequences ; Homopolymers ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Themastermind gene ofDrosophila melanogaster encodes a novel, highly repetitive nuclear protein required for neural development. To identify functionally important regions we have initiated an interspecific comparison of the gene inDrosophila virilis. Mastermind transcription and genomic organization are similar in both species and sequence analysis reveals significant conservation in a major cluster of charged amino acids. In contrast, extensive variation is noted in homopolymer domains that immediately flank the acidic cluster. Distinct patterns of evolutionary change can be identified: the major difference between unique regions are occasional amino acid substitutions whereas the repetitive areas are characterized by numerous large in-frame insertions/deletions and a nearly threefold higher rate of amino acid replacement. Conservation of the acidic domain suggests that it has an important functional role whereas the hypervariable homopolymer regions appear to be under less selective constraints than adjacent unique areas.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 333-346 
    ISSN: 1432-1432
    Schlagwort(e): Protamine ; Evolution ; Nuclear protein ; DNA condensation ; Sperm proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The availability of the amino acid sequence for nine different mammalian P1 family protamines and the revised amino acid sequence of the chicken protamine galline (Oliva and Dixon 1989) reveals a much close relationship between mammalian and avian protamines than was previously thought (Nakano et al. 1976). Dot matrix analysis of all protamine genes for which genomic DNA or cDNA sequence is available reveals both marked sequence similarities in the mammalian protamine gene family and internal repeated sequences in the chicken protamine gene. The detailed alignments of the cis-acting regulatory DNA sequences shows several consensus sequence patterns, particularly the conservation of a cAMP response element (CRE) in all the protamine genes and of the regions flanking the TATA box, CAP site, N-terminal coding region, and polyadenylation signal. In addition we have found a high frequency of the CA dinucleotide immediately adjacent to the CRE element of both the protamine genes and the testis transition proteins, a feature not present in other genes, which suggests the existence of an extended CRE motif involved in the coordinate expression of protamine and transition protein genes during spermatogenesis. Overall these findings suggest the existence of an avian-mammalian P1 protamine gene line and are discussed in the context of different hypotheses for protamine gene evolution and regulation.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 409-424 
    ISSN: 1432-1432
    Schlagwort(e): Phylogeny ; Tetrapods ; Morphology ; Cladistics ; Divergence ; Evolution ; Amphibians ; Reptiles ; Birds ; Mammals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The phylogeny of the major groups of tetrapods (amphibians, reptiles, birds, and mammals) has until recently been poorly understood. Cladistic analyses of morphological data are producing new hypotheses concerning the relationships of the major groups, with a focus on the identification of monophyletic groups. Molecular phylogenies support some of these views and dispute others. Geological dates of the major evolutionary branching points are recalculated on the basis of the cladograms and new fossil finds.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 32 (1991), S. 24-30 
    ISSN: 1432-1432
    Schlagwort(e): Short sequence distribution ; Sequence constraints ; Averaged sequence ; Sequence structure ; Asymmetric nucleotide sequences ; GC content ; Evolution ; Evolutionary constraints
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The data from a genomic library can be sorted into the frequencies of every possible tetranucleotide in the sequence. This tabulation, a short sequence distribution, contains the frequency of occurrence of the 256 tetranucleotides and thus seems to serve as a vehicle for averaging sequence information. Two such distributions can be readily compared by correlation. Reported here are correlations (Spearmanr s) of the distributions from all of the genomic libraries in GenBank 44.0 with sizes equal to or larger than that ofSalmonella typhimurium, except for the data for mouse and humans. All of the organisms examined showed highly significant correlations between the two DNA strands (not the complementarity expected from base pairing). Of 155 comparisons between libraries, 132 showed significant correlations at the 99% confidence level. Application of the correlation coefficients as a similarity matrix clustered most organisms in a phenogram in a pattern consistent with other hypotheses. This suggests a highly conserved pattern underlying all other genetic information in cellular DNA and affecting both DNA strands, perhaps caused by interaction with conserved factors necessary for DNA packaging.
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  • 19
    ISSN: 1432-1432
    Schlagwort(e): Lagomorphs ; Rabbit ; Mitochondrial DNA ; Heteroplasmy ; Restriction site polymorphism ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A characterization was conducted on mitochondrial DNA (mtDNA) molecules extracted separately from 107 European rabbits (Oryctolagus cuniculus) both wild and domestic, 13 European hares (Lepus capensis), and 1 eastern cottontail (Sylvilagus floridanus). Experimentally this study took into account restriction site polymorphism, overall length variation of the noncoding region, and numbers of repeated sequences. Nucleotide divergences indicate that the mtDNAs from the three species derived from a common ancestor some 6–8 million years (Myr) ago. Every animal appeared heteroplasmic for a set of molecules with various lengths of the noncoding region and variable numbers of repeated sequences that contribute to them. This systematic heteroplasmy, most probably generated by a rate of localized mtDNA rearrangements high enough to counterbalance the cellular segregation of rearranged molecules, is a shared derived character of leporids. The geographic distribution of mtDNA polymorphism among wild rabbit populations over the western European basin shows that two molecular lineages are represented, one in southern Spain, the second over northern Spain, France, and Tunisia. These two lineages derived from a common ancestor some 2 Myr ago. Their present geographical distribution may be correlated to the separation of rabbits into two stocks at the time of Mindel glaciation. Finally the distribution of mtDNA diversity exhibits a mosaic pattern both at inter- and intrapopulation levels.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 175-178 
    ISSN: 1432-1432
    Schlagwort(e): Aspergillus ; 5S rRNA genes ; 5S rRNA pseudogenes ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have cloned and determined the nucleotide sequence of 18 DNA fragments hybridizing to 5S rRNA from twoAspergillus species-A. wentii andA. awamori. Four of the analyzed sequences were pseudogenes. The gene sequences of these two species were very similar and differed fromAspergillus nidulans at both constant and microheterogeneous sites.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 464-469 
    ISSN: 1432-1432
    Schlagwort(e): Evolution ; tRNA ; Ribosome ; Peptide bond ; Catalytic RNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Continuation of early evolutionary bonding between tRNAs would provide a solution to residence time problems between peptidyl-tRNA and mRNA. It could also improve the speed of peptide bond formation by holding the amino acid close to the growing peptide. The tRNA clover leaf structure would allow each tRNA to from a TΨC(GA)-loop bond to one side and a D-loop bond to the other, hence fixing itself within a group of tRNAs, all attached to the mRNA. This can be developed into a system for peptide elongation in which bonds are made and broken in an ordered sequence, with each step triggering the next. This leads to a model system that fits with some recent propsals for a three-site ribosome.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 3-9 
    ISSN: 1432-1432
    Schlagwort(e): Caenorhabditis elegans ; Caenorhabditis briggsae ; hsp70 ; grp78 ; Gene comparison ; Evolution ; Regulatory elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Caenorhabditis elegans andCaenorhabditis briggsae are two closely related nematode species that are nearly identical morphologically. Interspecific cross-hybridizing DNA appears to be restricted primarily to coding regions. We compared portions of thehsp-3 homologs two grp 78-like genes, fromC. elegans andC. briggsae and detected regions of DNA identity in the coding region, the 5′ flanking DNAs, and the introns. Thehsp-3 homologs share approximately 98% and 93% identity at the amino acid and nucleotide levels, respectively. Using the nucleotide substitution rate at the silent third position of the codons, we have estimated a lower limit for the date of divergence betweenC. elegans andC. briggsae to be approximately 23–32 million years ago. The 5′ flanking DNAs and one of the introns contain elements that are highly conserved betweenC. elegans andC. briggsae. Some of the regions of nucleotide identity in the 5′ flanking DNAs correspond to previously detected identities including viral enhancer sequences, a heat shock element, and an element present in the regulatory regions of mammalian grp78 and grp94 genes. We propose that a comparison ofC. elegans andC. briggsae sequences will be useful in the detection of potential regulatory and structural elements.
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  • 23
    ISSN: 1432-1432
    Schlagwort(e): Archaebacteria ; rRNA operons ; Secondary structure ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Several sequences flanking the large rRNA genes of several transcripts from extreme thermophiles, extreme halophiles, and methanogens were aligned and analyzed for the presence of common primary and secondary structural features, which would bear on the concept of monphyletic archaebacteria. Few sequences were common to all the archaebacterial transcripts, and these were confined to short regions generally flanking putative double helices. At a secondary structural level, however, in addition to the previously characterized processing stems of the 16S and 23S RNAs, four helices were detected that were common to the archaebacterial transcripts: two in the 16S RNA leader sequence and two in the 16S-23S RNA spacer. Although all of these helices vary in size and form from organism to organism, three of them contain double helical segments that are strongly supported by compensating base changes among the three archaebacterial groups. Three extreme halophiles exhibited two additional helices in their relatively large spacers and a further helix preceding the 5S RNA, which are also supported by compensating base changes. Ribosomal RNA transcripts from eubateria/chloroplasts and eukaryotes were also examined for secondary structural features with locations and forms corresponding to those of the archaebacteria, but none were detected. The analysis provides support for the monophyletic nature of the archaebacteria and reinforces their differences from eubacteria/chloroplasts and eukaryotes.
    Materialart: Digitale Medien
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  • 24
    ISSN: 1432-1432
    Schlagwort(e): Retroposon ; Salmonid ; +RNA ; Evolution ; Average sequence divergence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An in vitro runoff transcription assay of total genomic DNA was developed. As an example of use of this assay, analysis of a highly repetitive sequence in the cherry salmon (Oncorhynchus masou) is described. Total genomic DNA of the cherry salmon was completely digested with Hpa 1, whose site is known to be in the tRNA-unrelated region of the cherry salmon Hpa 1 family. On transcription of the digested DNA in a HeLa cell extract, a discrete-sized RNA of about 100 nucleotides, constituting 70% of the transcripts, was produced, whereas on transcription of the undigested total DNA, only smeared RNA was obtained. In a fingerprint, the oligonucleotides of the discrete transcript from the digested total DNA were very distinct and exactly corresponded to those of a transcript from an Hpa 1 digest of a cloned DNA, but with few extra oligonucleotides. These results showed that the cherry salmon Hpa 1 family constitutes a major repetitive family in the genome of the cherry salmon. For determination of the distribution of the salmonid Hpa 1 family in other salmonid species, the same analysis was applied to DNAs from the chum salmon (Oncorhynchus keta), brown trout (Salmo trutta), Japanese common charr (Salvelinus leucomaenis pluvius), and Japanese huchen (Hucho perryi). The results showed that the salmonid Hpa 1 family is widespread in the genomes of salmonid species. A method and equations are also presented for estimating the relationship between the ratio of a given repetitive family to all the Pol III genes and its average sequence divergence by calculating the molar ratio of the runoff transcript to all the in vitro Pol III transcripts.
    Materialart: Digitale Medien
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  • 25
    ISSN: 1432-1432
    Schlagwort(e): Phylogenetic tree ; Likelihood method ; RNA polymerase ; Archaebacteria ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The amino acid sequences of the largest subunits of the RNA polymerases I, II, and III from eukaryotes were compared with those of archaebacterial and eubacterial homologs, and their evolutionary relationships were analyzed in detail by a recently developed tree-making method, the likelihood method of protein phylogeny, as well as by the neighbor-joining method and the parsimony method, together with bootstrap analyses. It was shown that the best tree topologies predicted by the first two methods are identical, whereas the last one predicts a distinct tree. The maximum likelihood tree revealed that, after the separation from archaebacteria, the three eukaryotic RNA polymerases diverged from an ancestral precursor in the eukaryotic lineage. This result is contrasted with the published result showing multiple origins for the three eukaryotic polymerases. It was shown that eukaryotic RNA polymerase I evolved much more rapidly than RNA polymerases II and III: The N-terminal half of RNA polymerase I shows an extraordinarily high evolutionary rate, possibly due to relaxed functional constraints. In contrast the evolutionary rate of archaebacterial RNA polymerase is remarkably limited. In addition, including the second largest subunit of the RNA polymerase, a detailed analysis for the branching pattern of the three major groups of archaebacteria was carried out by the maximum likelihood method. It was shown that the three major groups of archaebacteria are likely to form a single cluster; that is, archaebacteria are likely to be monophyletic as originally proposed by Woese and his colleagues.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 42-48 
    ISSN: 1432-1432
    Schlagwort(e): Satellite DNA ; Mouse ; Human chromosomes 13 and 21 ; Evolution ; Saltatory amplification ; Homogenization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The hypothesis that highly reiterated satellite DNAs in present-day populations evolve by molecular mechanisms that create, by saltatory amplification steps, new long arrays of satellite DNA, and that such long arrays are used for homogenization purposes, has been tested both in mouse and in humans. In mouse, the data obtained are consistent with this hypothesis. This was tested in more detail on chromosomes 13 and 21 of the human genome. A Centre d'Etudes du Polymorphisme Humain family, which in some individuals exhibits strong supplementary DNA bands following TaqI restriction endonuclease digestion and conventional gel electrophoresis, was analyzed by pulse field gel electrophoresis following restriction by BamHI. The supplementary bands on chromosome 13 (18 times the basic alpha satellite DNA repeat) and on chromosome 21 (a 9.5-mer) segregated with centromeric alpha satellite DNA blocks of 5 and 5.3 megabases, respectively. These are by far the largest alpha satellite block lengths seen in all chromosome 13 and chromosome 21 centrometric sequences so far analyzed in this manner. The possibility that these supplementary alpha satellite sequences were created in single individuals by saltatory amplification steps is discussed in light of our own data and that published by others. It is proposed that deletion events and unequal cross-overs, which both occur in large satellite DNA arrays, contribute to the homogenization of size and sequence of the alpha satellite DNA on most chromosomes of humans.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 207-208 
    ISSN: 1432-1432
    Schlagwort(e): Evolution ; Vesicle ; Biogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The earliest fossil stromatolites present evidence of a complex ecosystem of photosynthetic organisms. Because the origin of present life can be dated within a few hundred million years prior to these fossils, their complexity poses a problem. A heuristic model outlines the first radiation leading to the universal ancestor.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 205-210 
    ISSN: 1432-1432
    Schlagwort(e): Isozyme ; Intron ; Phylogenetic tree ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Both the mouse cytosolic malate dehydrogenase gene and its mitochondrial counterpart contain eight introns, of which two are present at identical positions between the isozyme genes. The probability that the two intron positions coincide by chance between the two genes has been shown to be significantly small (=1.3×10−3), suggesting that the conservation of the intron positions has a biological significance. On the basis of a rooted phylogenetic tree inferred from a comparison of these isozymes and lactate dehydrogenases, we have shown that the origins of the conserved introns are very old, possibly going back to a date before the divergence of eubacteria, archaebacteria, and eukaryotes. In the aspartate aminotransferase isozyme genes, five of the introns are at identical places. The origins of the five conserved introns, however, are not obvious at present. It remains possible that some or all of the conserved introns have evolved after the divergence of eubacteria and eukaryotes.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 325-329 
    ISSN: 1432-1432
    Schlagwort(e): PLP-dependent decarboxylase ; Evolution ; Profile analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A database search has revealed significant and extensive sequence similarities among prokaryotic and eukaryotic pyridoxal phosphate (PLP)-dependent decarboxylases, includingDrosophila glutamic acid decarboxylase (GAD) and bacterial histidine decarboxylase (HDC). Based on these findings, the sequences of seven PLP-dependent decarboxylases from five different organisms have been aligned to derive a consensus sequence for this family of enzymes. In addition, quantitative methods have been employed to calculate the relative evolutionary distances between pairs of the decarboxylases comprising this family. The multiple sequence analysis together with the quantitative results strongly suggest an ancient and common origin for all PLP-dependent decarboxylases. This analysis also indicates that prokaryotic and eukaryotic HDC activities evolved independently. Finally, a sensitive search algorithm (PROFILE) was unable to detect additional members of this decarboxylase family in protein sequence databases.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 485-492 
    ISSN: 1432-1432
    Schlagwort(e): BK virus ; Strains ; Regulatory region ; Late region ; Nucleotide sequence ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Within the genome of human polyomavirus BK (BKV), there exists a noncoding regulatory region toward the late region side of the origin of DNA replication. In most BKV strains isolated by viral culture, this regulatory region contains tandem repeats varying in size. Recently. however, several laboratories isolated new BKV strains (designated as archetypal strains) lacking such repeat sequences. To examine the genetic relationship between archetypal strains, a phylogenetic tree was constructed for seven BKV strains, including three archetypal strains, from DNA sequence data on the late genes, those for leader protein (agnoprotein), and those for structural proteins (VP1, VP2, and VP3). For three strains data previously reported were used, whereas for the others sequences were determined in this study. From total numbers of nucleotide substitutions in each pair of strains, a phylogenetic tree was constructed by the unweighted pair-group method. The phylogenetic tree obtained reveals that BKV strains containing the archetypal regulatory region do not constitute a cluster of closely related strains and that these strains, together with those carrying the major part of the archetypal regulatory region, are widespread in the BKV population. This finding suggests that the basic structure of the archetypal regulatory region has been conserved in the course of BKV evolution.
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 111 (1990), S. 181-189 
    ISSN: 1573-0832
    Schlagwort(e): mycotoxin ; ochratoxin ; Penicillium ; storage ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Eleven-kilogram parcels of HY-320 wheat, a cultivar of the new Canada Prairie Spring class, were kept at 15 and 19% initial moisture contents (IMC) in simulated storage in a Manitoba farm granary for 60 weeks to determine biotic and abiotic changes and mycotoxin production. Ochratoxin A reached a maximum of 0.24 ppm by week 20 in the 19% IMC wheat, but was absent in the 15% IMC wheat; no other mycotoxins were detected. Temperature, moisture content, O2 and CO2 levels, fat acidity values, seed germination, microfloral incidence and abundance, and the presence of other mycotoxins were monitored. Principal component analysis of all variables showed that the first principal components accounted for 32–41% of the system variability, and contained the ochratoxin A variable. Ochratoxin A was produced in moist grain that had decreased seed germination andAltermaria activity, and high fungal activity byPenicillium andAspergillus versicolor. Compared to other stored cereals previously studied, HY-320 wheat would be ranked in a low-risk category for mycotoxin formation, based on the ochratoxin A levels observed.
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  • 32
    ISSN: 1573-0832
    Schlagwort(e): Penicillium griseofulvum ; patulin ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Sixty-four wheat samples from Spanish flour factories were screened for patulin and patulin-producing moulds. None of them was found to contain any patulin, whereas samples experimentally contaminated with this toxin proved it to be highly unstable. On the other hand, Penicillium griseofulvum was the only in vitro patulin-producing species found (19 samples). Mould growth in the samples was investigated by using yeast-sucrose medium (YES) and high-performance liquid chromatography (HPLC) to measure the amounts of toxin produced during 40 day's incubation at 20 and 28°C. The highest yield rate of patulin was obtained between the 20th and 30th day of incubation; such a rate, however, was very low throughout the vigorous growth phase, during the first 20 days of incubation. The more appropriate temperature for incubation and patulin production was 28 °C. We also investigated the influence of other incubation conditions in the yield and found stationary dark cultures to be more efficient that shaken or fermentation cultures in YES medium. The best patulin yield achieved was 11.9 mg in the culture broth and 6.3 mg in the mycelium from 100 ml of medium.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 29 (1991), S. 163-172 
    ISSN: 1573-0867
    Schlagwort(e): Superphosphate ; residual value ; sandy soil ; leaching of phosphorus ; lupins ; barley ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In a field experiment on deep, yellow, sandy soil near Badgingarra, Western Australia, the residual value of superphosphate applied one and two years previously was measured relative to freshly-applied superphosphate using yields of narrow-leafed lupin (Lupinus angustifolius), barley and wheat. In addition, soil samples were collected for measurement of bicarbonate-extractable soil P. This was also used to estimate the residual value of the superphosphate. For lupins and wheat, and for bicarbonate-extractable soil P, the residual value decreased with increasing level of application. For barley grain, the residual value was not significantly affected by the level of application. The decrease in residual value of superphosphate with increasing level of application is attributed to increased leaching of applied phosphorus (P) down the profile of the sandy soils as the level of application increases. This may reduce subsequent plant yields due to the delay in seedling roots reaching the P in the soil during the crucial early stages of plant growth. For lupins, the relationship between yield and the level of superphosphate applied was markedly sigmoidal. The relationship for wheat and barley was exponential. Consequently, at suboptimal levels of P application, lupins required about two to three times more P than wheat or barley to produce the same yield. However, lupins required less P to achieve near-maximum yield.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 21 (1990), S. 163-166 
    ISSN: 1573-0867
    Schlagwort(e): Critical level of Zn ; alkaline soils ; Zn-deficiency ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Field experiments were conducted at 32 locations, chosen for their wide range in DTPA extractable Zn, to determine the critical deficiency level of Zn for predicting response of wheat to Zn application. Soil application of 5.6 kg Zn ha−1 significantly increased the grain yield in deficient soils. Soil extractable Zn was significantly related with per cent grain response and absolute grain yield. Both the graphical and statistical methods of Cate and Nelson indicated the critical level to be 0.75 mg kg−1 soil of DTPA extractable Zn. This level gave a predictability value of 82 per cent.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 22 (1990), S. 147-159 
    ISSN: 1573-0867
    Schlagwort(e): Sulfate ; elemental sulfur ; leaching ; ryegrass ; wheat ; greenhouse experiments ; split application
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Three factorial experiments with four replications were conducted in a greenhouse to examine the effectiveness of gypsum, elemental sulfur (ES powder) and three S containing N fertilizers, viz., ammonium sulfate (AS), urea + ES, and Ureas (20% AS and 80% urea). All experiments were conducted twice in different years. In the first experiment with uncropped soil, the effects of soil type, leaching rate (2.3 and 6.9 mm water per day) and urea addition on sulfate leaching losses were studied. Leaching losses decreased in the order Ureas 〉 ammonium sulfate (AS) 〉 gypsum ≫ urea + ES. Increasing the leaching rate greatly increased sulfate losses from both soils. Losses were greater in the sandy Typic Hapludoll than in the clayey Oxic Paleustalf. Sulfate adsorption was found to decrease strongly with rising the pH in both soils. Hydrolysis of urea temporarily raised the pH of the soil, thereby increasing the sulfate leaching losses. In the second experiment the effects of S rate (0–65 mg per kg soil), split application and leaching rate (0 and 2.3 mm per day) on sulfate leaching losses and ‘apparent S recovery’ (ASR) by three successive cuts of ryegrass (Lolium perenne L.) were studied. Herbage yield more than doubled when S was applied. The effectiveness of the sulfate fertilizers was greater when S was split-applied than given all at once. With split applications the ASR decreased in the order: Ureas 〉 AS 〉 gypsum 〉 urea + ES 〉 ES powder. ES fertilizers were least effective, because the oxidation rate of ES to sulfate was clearly too slow. In the third experiment the effects of S rate (0–40 mg per kg soil) and split application on sulfate leaching losses and ASR in the grain of wheat (Triticum aestivum L.) were studied under leaching conditions (2.3 mm per day). Grain yield increased strongly due to S application. Split application greatly increased the effectiveness of the sulfate fertilizers and appeared to be an effective tool in satisfying the S need of the crop under leaching conditions. Again, ES fertilizers were least effective, because the oxidation rate of ES was too slow to meet the S demand of the crop. In all experiments leaching losses of sulfate from the ES fertilizers were smaller than from the sulfate fertilizers.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 22 (1990), S. 97-107 
    ISSN: 1573-0867
    Schlagwort(e): Superphosphate ; placement depth ; banding ; relative effectivenesss ; lupins ; wheat ; field experiment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In a field experiment on a sandplain soil in a low rainfall (326mm per annum) Mediterranean environment of south-western Australia, seven levels of single superphosphate, 0, 7.5, 10, 14, 19.5, 30 and 39 kg P ha−1, were placed at either 3, 5, 7, 9, 11 or 13 cm depth before sowing wheat (Triticum aestivum) at 3 cm. In a separate treatment, superphosphate was drilled with the seed (the normal practice). In the second year, the plots were sown with lupins (Lupinus angustifolius) at 3 cm depth with no additional superphosphate. In three separate treatments, superphosphate at 0, 14 and 39 kg P ha−1, was drilled with the lupin seed (the normal practice) on plots that had received no superphosphate in the first year. Yields of wheat and lupins were used as a measure of the effectiveness of the superphosphate placement treatments relative to the effectiveness of superphosphate drilled with seed of wheat (year 1) or lupins (year 2), to give relative effectiveness (RE) values in each of the two years. In the first year the RE of superphosphate was increased by about 20% when the fertilizer was placed 5 to 9 cm deep in the soil. In the second year, the RE of superphosphate for producing lupin grain was increased by about 30–60% where the fertilizer had been placed 5–13 cm deep in the previous year compared with freshly drilled 3 cm deep. The yield of wheat or lupins was closely related to the P content of plant tissue; each relationship was independent of the depth or year of superphosphate application.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 26 (1990), S. 229-235 
    ISSN: 1573-0867
    Schlagwort(e): Grass ; wheat ; nitrogen nutrition ; dilution curve ; mineral content ; mineral removal ; phosphorus ; potassium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The important effect of nitrogen in changing the patterns of mineral content and mineral removal is analysed for grass swards and wheat. Different models are proposed; accumulated dry matter developed throughout a growing period is shown to be an excellent reference for assessing the evolution of the plant mineral content and the mineral removal the growing crop. Applications in diagnosing mineral nutrition status and optimising fertilizer use are proposed and discussed.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 46 (1990), S. 530-533 
    ISSN: 1420-9071
    Schlagwort(e): Evolution ; genetics ; heritability ; locomotion ; physiology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Locomotor capacities and their physiological bases are thought to be of considerable selective importance in natural populations. Within this functional complex, organismal performance traits (e.g., speed, stamina) are expected to be of more direct selective importance than their suborganismal determinants (e.g., heart size). Quantitative genetics theory predicts that traits of greater selective importance should generally have lower heritabilities at equilibrium. Contrary to these expectations, we report that organismal performance traits had the highest heritabilities in a natural population of garter snakes.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 46 (1990), S. 1016-1017 
    ISSN: 1420-9071
    Schlagwort(e): In vitro absorption ; calcium ; wheat ; Bengal gram
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The in vitro absorption of calcium from the duodenum was significantly less in a group of rats fed on a wheat diet than in a group fed a wheat and Bengal gram (70∶30) diet.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 35 (1991), S. 180-186 
    ISSN: 1432-1254
    Schlagwort(e): Evolution ; Paleophysiology ; Primates ; Sweating ; Thermoregulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Abstract Mammals have two kinds of sweat glands, apocrine and eccrine, which provide for thermal cooling. In this paper we describe the distribution and characteristics of these glands in selected mammals, especially primates, and reject the suggested development of the eccrine gland from the apocrine gland during the Tertiary geological period. The evidence strongly suggests that the two glands, depending on the presence or absence of fur, have equal and similar functions among mammals; apocrine glands are not primitive. However, there is a unique and remarkable thermal eccrine system in humans; we suggest that this system evolved in concert with bipedalism and a smooth hairless skin.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell reports 10 (1991), S. 148-151 
    ISSN: 1432-203X
    Schlagwort(e): wheat ; rye ; embryogenesis ; growth ; tissue culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The influence of the short arm of rye chromosome 1 (1RS) from Secale cereale var. Imperial on the growth and differentiation of callus cultures from wheat Triticum aestivum var. Chinese Spring immature embryos was analysed. This chromosome arm was found to stimulate both embryogenesis and the rate of growth of calli. Recombinant lines carrying segments of 1RS were used to delineate the regions of 1RS responsible for the tissue culture effects. The enhancement of embryogenesis and the stimulation of growth were shown to be associated with two distinct genetic regions of the chromosome arm; the former is located between the centromere and the Sec 1 locus, while the latter is situated in the immediate vicinity of the Sec 1 locus.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Current genetics 20 (1991), S. 173-175 
    ISSN: 1432-0983
    Schlagwort(e): Batophora ; Small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (SSU) ; rbcS cDNA sequence ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Two cDNA clones for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (SSU) of Batophora oerstedii were isolated and sequenced. One clone contains the coding information for the complete SSU precursor protein. As in two other species of Dasycladaceae (Acetabularia mediterranea and A. cliftonii), the rbcS cDNA sequences of B. oerstedii display the codons TAA or TAG, which seem to code for glutamine, in the reading frame. The amino acid substitution rate for the SSU protein was calculated to be 0.35–0.41 amino acids per 109 years per site based on the substitutions observed in the SSU amino acid sequences of Acetabularia and Batophora.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 167 (1990), S. 71-78 
    ISSN: 1432-1351
    Schlagwort(e): Compound eye ; Optics ; Crustacea ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Compound eyes of the decapod shrimp Gennadas, the hermit crab Dardanus, and the syncarid crustacean Anaspides are studied histologically and with optical experiments. The results demonstrate that these three crustaceans all have refracting superposition eyes. The conclusion is based on the following observations: 1. There is a wide clear-zone, which allows for a superposition image to be formed. 2. Dark-adapted eyes display a large eye-glow, and the ommatidia are not optically isolated. 3. The crystalline cones have the shape typical for refracting superposition eyes, and they contain the required lens-cylinder gradient of refractive index. Euphausiids and mysids were previously thought to be the only crustaceans with refracting superposition eyes, whereas the species investigated here were assumed to have reflecting superposition eyes (decapod shrimps) or apposition eyes (hermit crabs and syncarids). The present findings increase more than twofold the number of crustacean groups that are known to have developed refracting superposition optics. It also provides insight into the evolutionary mechanisms that may have led to the development of this type of imaging optics.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 169 (1991), S. 191-200 
    ISSN: 1432-1351
    Schlagwort(e): Insect ; Behaviour ; Pattern generation ; Grasshopper ; Stridulation ; Bilateral coordination ; Abdominal ganglia ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Stridulation of grasshoppers is controlled by hemisegmental pattern generator subunits which probably are restricted to the metathoracic ganglion complex (TG3-complex). The coordination of left and right pattern generator subunits depends on commissures of the TG3-complex (Ronacher 1989). The coordination of the stridulatory movements was studied in Chorthippus dorsatus males with partial mediosagittal incisions in the TG3-complex. Animals bearing anterior incisions in the TG3-complex, by which all commissures of the metathoracic neuromere and the first abdominal neuromere were transected, were still able to produce bilaterally coordinated species-specific stridulatory movements. Commissures of the T3- and A1-neuromere, thus, are not necessary, and the A2-, A3-commissures are sufficient for this coordination (Figs. 3, 4). Animals with partial posterior incisions, extending until A1, had deficits in their stridulation pattern; the coordination between the hindlegs was impaired though not completely lost (Fig. 6). This is discussed in view of the structure of ‘stridulation interneurons’ identified in a related grasshopper species (Omocestus viridulus). These results indicate an unexpected substantial contribution of the abdominal neuromeres A2 and A3 to the control of stridulatory movements. This constitutes an interesting parallel to the flight control system of locusts where interneurons located in the first 3 abdominal neuromeres also appear to contribute to the flight pattern generator (Robertson et al. 1982).
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  • 45
    ISSN: 1432-072X
    Schlagwort(e): Oligotrophic bacteria ; Caulobacter ; “Hyphobacter” ; Hyphomonas ; Hyphomicrobium ; Antibiotic sensitivity ; Evolution ; Fatty acids ; Lipids ; Taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new approach was developed for the determination of taxonomic and evolutional relationships among four genera of oligotrophic bacteria. The main idea of this approach is the algorithmized integrative analysis of the morphological and physiological specificity of these bacteria, their 5S rRNA sequences, fatty acid and lipid composition of their membranes, as well as their sensitivity to a large variety of antibiotics. It was shown that the genera Caulobacter and Hyphomonas are closely related to each other, but they are both distant from Hyphomicrobium species. The new genus, “Hyphobacter”, is placed between Caulobacter and Hyphomonas. Taxonomic heterogeneity was found to exist within the genera Caulobacter and Hyphomicrobium. Evolutional pathways from Caulobacter to Hyphomicrobium are proposed on the basis of the present data. No correlations were found between the cell morphology of the organisms and their geno-and chemotaxonomy.
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  • 46
    ISSN: 1432-072X
    Schlagwort(e): Eubacterium ; Thermophile ; Evolution ; Fervidobacterium ; Lipids ; Thermotoga
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An extremely thermophilic anaerobic fermentative eubacterium growing at temperatures between 50 and 80°C (opt.: 65°C) was isolated from an Icelandic hot spring. The cells were Gram-negative motile rods, about 1.8 μm in length, and 0.6 μm in width occurring singly and in pairs. About 50% of the cells formed large spheroids at one end similar to Fervidobacterium nodosum. The new isolate H 21 differed from Fervidobacterium nodosum by a 6 mol % higher GC-content of its DNA (41 mol %), its ability to grow on cellulose, and insignificant DNA homology. The lipids of isolate H 21 were similar to that of members of “Thermotogales”. 16S rRNA sequencing of isolate H 21 and Fervidobacterium nodosum indicated (a) that isolate H 21 represents a new species of the genus Fervidobacterium which we name Fervidobacterium islandicum and (b) that the genus Fervidobacterium belongs to the “Thermotogales” branch.
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  • 47
    ISSN: 1573-1561
    Schlagwort(e): Allelochemicals ; no-tillage ; conventional-tillage ; soils ; wheat ; Triticum aestivum ; mass spectrometry ; Petri-dish bioassay ; fatty acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Putative allelochemicals found in the soil of no-tillage and conventional-tillage wheat plots near Stillwater, Oklahoma, were obtained by a mild alkaline aqueous extraction procedure, bioassayed to determine their biological activity, purified, and analyzed with a capillary gas chromatography-mass spectrometry-data analysis system. The most significant inhibition was found in bioassays of extracts from soil collected immediately after harvest in June, July, and August. No-tillage soils produced significant inhibition during the rest of the year also. Mass spectrometry showed fatty acids as the most abundant compounds. However, when bioassayed authentic samples of the five free fatty acids showed no significant biological activity toward wheat.
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  • 48
    ISSN: 1573-5028
    Schlagwort(e): tRNA-like sequences ; t-elements ; RNA processing ; mitochondria ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have recently described the properties of a wheat mitochondrial extract that is able to process, accurately and efficiently, artificial transcripts containing wheat mitochondrial tRNA sequences, with the production of mature tRNAs (P.J. Hanic-Joyce and M.W. Gray, J. Biol. Chem., in press). Such processing involves 5′-endonucleolytic, 3′-endonucleolytic, and TRNA nucleotidyltransferase activities. Here we show that this system also acts on transcripts containing sequences corresponding to an unusual class of short repeats (‘t-elements’) in wheat mtDNA. These repeats are theoretically capable of assuming a tRNA-like secondary structure, although stable transcripts corresponding to them are not detectable in vivo. We find that t-element sequences are processed with the same specificity and with comparable efficiency as are authentic tRNA sequences. Because known t-elements are located close to and in the same transcriptional orientation as active genes (18S-5S, 26S, tRNAPro) in wheat mtDNA, our results raise the question of whether t-elements play a role in gene expression in wheat mitochondria.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 16 (1991), S. 335-337 
    ISSN: 1573-5028
    Schlagwort(e): Triticum ; wheat ; endosperm ; gliadin ; pseudogene ; duplication ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 16 (1991), S. 907-908 
    ISSN: 1573-5028
    Schlagwort(e): ubiquitin ; wheat ; heat shock protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 51
    ISSN: 1573-5028
    Schlagwort(e): α-amylase inhibitor ; expression inE. coli ; glycosylation versus activity ; insect α-amylase ; mutagenesis ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The wheat monomeric inhibitor WMAI-1 (syn. 0.28) produced inEscherichia coli using the pT7-7 expression ventor has the correct N-terminal sequence and the same electrophoretic mobility and specific activity towards the α-amylase from the insectTenebrio molitor as the native WMAI-1 isolated from wheat. This confirms that the native inhibitor is not glycosylated and contradicts claims that a putative glycosyl moiety was essential for inhibition. Thirteen mutants have been obtained at six different sites. Substitution of the highly conserved N-terminal S by the sequence ARIRAR increased the pre-incubation time required for maximum activity. A similar result was obtained by insertion of GPRLPW after position 4, while insertion of EPRAPW at the same position rendered the inhibitor inactive. The substitution D/EGPRL and insertions DGP or D, at position 58, produced complete inactivation. All other mutations had only minor effects on activity.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 17 (1991), S. 273-275 
    ISSN: 1573-5028
    Schlagwort(e): Tahsp17.3 ; low-molecular-weight HSP ; Triticum aestivum L. ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 53
    ISSN: 1573-5028
    Schlagwort(e): α-amylase tetrameric inhibitor ; cDNA cloning ; genetic mapping ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have characterized three cDNA clones corresponding to proteins CM1, CM3 and CM16, which represent the three types of subunits of the wheat tetrameric inhibitor of insect α-amylases. The deduced amino acid sequences of the mature polypeptides are homologous to those of the dimeric and monomeric α-amylase inhibitors and of the trypsin inhibitors. The mature polypeptides are preceded by typical signal peptides. Southern blot analysis of appropriate aneuploids, using the cloned cDNAs as probes, has revealed the location of genes for subunits of the CM3 and of the CM16 type within a few kb of each other in chromosomes 4A, 4B and 4D, and those for the CM1 type of subunit in chromosomes 7A, 7B and 7D. Known subunits of the tetrameric inhibitor corresponding to genes from the B and D genomes have been previously characterized. No proteins of this class have been found to be encoded by the A genome in hexaploid wheat (genomes AA, BB, DD) or in diploid wheats (AA) and no anti α-amylase activity has been detected in the latter, so that the A-genome genes must be either silent (pseudogenes) or expressed at a much lower level.
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  • 54
    ISSN: 1573-5028
    Schlagwort(e): pathogen-induced ; peroxidase ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We report here the complete amino acid sequence of a pathogen-induced putative peroxidase from wheat (Triticum aestivum L.) as deduced from cDNA clones representing mRNA from leaves infected with the powdery mildew fungus Erysiphe graminis. The protein consists of 312 amino acids, of which the first 22 form a putative signal sequence, and has a calculated pI of 5.7. Sequence comparison revealed that the putative wheat peroxidase is most similar to the turnip (Brassica rapa) peroxidase, with which it shares 57% identical and 13% conserved amino acids.
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  • 55
    ISSN: 1573-5028
    Schlagwort(e): peroxidase gene ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have used a cDNA clone encoding a pathogen-induced putative wheat peroxidase to screen a genomic libary of wheat (Triticum aestivum L. cv. Cheyenne) and isolated one positive clone, lambda POX1. Sequence analysis revealed that this clone contains a gene encoding a putative peroxidase with a calculated pI of 8.1 which exhibits 58% and 83% sequence identity to the amino acid sequence of the turnip (Brassica rapa) peroxidase and a pathogen-induced putative wheat peroxidase, respectively. The two introns in the wheat gene are at the same positions as introns in the peroxidase genes of tomato and horseradish. Results of S1-mapping experiments suggest that this gene is neither pathogen-nor wound-induced in leaves but is constitutively expressed in roots.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 16 (1991), S. 1073-1076 
    ISSN: 1573-5028
    Schlagwort(e): abscisic acid ; dehydration ; LEA ; water stress ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A cDNA clone (pMA2005) of a Group 3 LEA (late embryogenesis abundant) protein has been sequenced from wheat. The wheat cDNA clone codes for a protein with ten tandem repeats of an 11 amino acid sequence and has homology to other Group 3 LEAs reported in barley, carrot, cotton and rape (L. Dure et al., Plant Mol Biol 12: 475–486, 1989). The deduced amino acid sequence indicates that the wheat protein has a molecular weight of 23 000 and is a basic, hydrophilic protein. Northern analysis with the cDNA clone shows that dehydration of wheat shoot tissue results in increased transcript levels that correlate with increases in endogenous ABA.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 15 (1990), S. 793-795 
    ISSN: 1573-5028
    Schlagwort(e): mitochondrial gene ; ORF25 ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The wheat mitochondrial orf25 nucleotide sequence of 576 pb has been determined. Its derived protein sequence shares 88% and 75% amino acid identity with those of maize and tobacco mitochondria, respectively. The wheat and tobacco orf25 sequences lack four inserts, of 6 bp to 36 bp, that are present in the maize homologue. The wheat orf25 gene is actively transcribed and is preceded by a regulatory sequence block very similar to those located upstream of the wheat coxII and atp6 genes. Our observations support the view that orf25 sequences encode a functional polypeptide in plant mitochondria.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 16 (1991), S. 663-670 
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; proline-rich protein ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A cDNA (WPRP1) encoding a wheat proline-rich protein has been isolated and sequenced. The amino acid composition shows 45% proline, with high levels of methionine, lysine and glutamic acid. The derived 378 residue amino acid sequence has a highly repetitive structure which is unlike those of other proline-rich proteins. The WPRP1 cDNA clone was used to determine the copy number and chromosomal location of the WPRP1 gene by restriction fragment length polymorphism analysis of wheat inbred lines. Although WPRP1 is encoded by a single-copy gene it is also a representative of a larger family of related sequences. RNA gel blot analysis showed that expression of WPRP1 is highest in rapidly growing tissue which together with its amino acid composition suggests a structural role for the encoded protein.
    Materialart: Digitale Medien
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  • 59
    ISSN: 1573-5028
    Schlagwort(e): wheat ; glutathione-S-transferase ; transposon-like sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 16 (1991), S. 1099-1101 
    ISSN: 1573-5028
    Schlagwort(e): wheat ; Triticum aestivum ; cDNA clone ; waxy protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 17 (1991), S. 167-168 
    ISSN: 1573-5028
    Schlagwort(e): chloroplast ; monocot gene ; phosphoribulokinase ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    ISSN: 1573-5028
    Schlagwort(e): Tahsp26.6 ; chloroplast-localized HSP ; Triticum aestivum L. ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Journal of mathematical biology 28 (1990), S. 237-256 
    ISSN: 1432-1416
    Schlagwort(e): Behavior ; Evolution ; Neural network ; Dynamic optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract One of the main challenges to the adaptionist program in general and the use of optimization models in behavioral and evolutionary ecology, in particular, is that organisms are so constrained' by ontogeny and phylogeny that they may not be able to attain optimal solutions, however those are defined. This paper responds to the challenge through the comparison of optimality and neural network models for the behavior of an individual polychaete worm. The evolutionary optimization model is used to compute behaviors (movement in and out of a tube) that maximize a measure of Darwinian fitness based on individual survival and reproduction. The neural network involves motor, sensory, energetic reserve and clock neuronal groups. Ontogeny of the neural network is the change of connections of a single individual in response to its experiences in the environment. Evolution of the neural network is the natural selection of initial values of connections between groups and learning rules for changing connections. Taken together, these can be viewed as “design parameters”. The best neural networks have fitnesses between 85% and 99% of the fitness of the evolutionary optimization model. More complicated models for polychaete worms are discussed. Formulation of a neural network model for host acceptance decisions by tephritid fruit flies leads to predictions about the neurobiology of the flies. The general conclusion is that neural networks appear to be sufficiently rich and plastic that even weak evolution of design parameters may be sufficient for organisms to achieve behaviors that give fitnesses close to the evolutionary optimal fitness, particularly if the behaviors are relatively simple.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Journal of mathematical biology 29 (1991), S. 743-761 
    ISSN: 1432-1416
    Schlagwort(e): Transposable element ; Branching-processes ; Population genetics ; Evolution ; Mobile genetic elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract We have formulated a very general mathematical model to analyze the evolution of transposable genetic elements in prokaryotic populations. Transposable genetic elements are DNA sequences able to replicate and insert copies of themselves at new locations in the genome. This work characterizes the equilibrium distribution of copy number under the influence of copy number-dependent selection, transposition and deletion. Our principal results concern the equilibrium distribution of copy number in response to various selective regimes. For particular transposition patterns (e.g. unregulated transposition or copy number-dependent transposition), equilibrium distributions are calculated numerically for a variety of specific selection patterns. Selection is quantified through specification of the expected number of offspring for individuals of each type, which is generally a non-increasing function of copy number, in accord with the usual evolutionary speculations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 168 (1991), S. 461-467 
    ISSN: 1432-1351
    Schlagwort(e): Electric fish ; Sternopygus ; Jamming avoidance ; Electrolocation conditioning ; Preadaptation ; Temporal filtering ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Several species of weakly electric fish reflexively change their frequency of electric organ discharge (EOD) in response to sensing signals of similar frequency from conspecifics; that is, they exhibit jamming avoidance responses (JAR).Eigenmannia increases its EOD frequency if jammed by a signal of lower frequency and decreases its EOD frequency if jammed by a signal of higher frequency. This discrimination is based on an analysis of the patterns of amplitude modulations and phase differences resulting from signal interference. Fish of the closely related genus,Sternopygus, however, do not exhibit a JAR. Here we show that despite lacking this behavior,Sternopygus shares many sensory processing capacities withEigenmannia: 1. Fish could be conditioned to discriminate the sign of the frequency difference (Df) between an exogenous sinusoidal signal and its own EODs with as few as 300 training trials. 2. Fish can discriminate the sign of Df for jamming signals with an amplitude as low as 2 μV/cm (p-p); which is approximately 40 dB below the amplitude of the fish's EOD, as measured lateral to the operculum. 3. Fish appear to discriminate the sign of Df by evaluating modulations in signal amplitude and differences in the timing of signals received by different areas of the body surface. 4. Sternopygus processes electrosensory information through band-pass modulation filters. Tuning to modulation rates over at least 4–16 Hz exists.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 79 (1990), S. 397-400 
    ISSN: 1432-2242
    Schlagwort(e): Durum wheat ; C-banding ; Homoeologous pairing ; Chromosome structure ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Meiotic pairing was analyzed at metaphase I in ABRR triticale × rye hybrids to identify the arm homoeology of chromosomes ofTriticum turgidum. Wheat chromosomes were identified using a C-banding technique. Results confirmed that the homoeologous relationships between chromosome arms of the A and B genomes inT. turgidum are the same as inT. aestivum, and that a double translocation involving4AL,5AL, and7BS is present inT. turgidum. It is proposed that a pericentric inversion involving a substantial portion of chromosome4A is present inT. turgidum andT. aestivum.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 296-304 
    ISSN: 1432-2242
    Schlagwort(e): Sorghum ; Isozyme ; Genetic diversity ; Evolution ; Systematics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A survey of allozyme variation among the spontaneous taxa of Sorghum section Sorghum was undertaken. Eight plants each of 90 accessions representing the diploid S. bicolor (ssp. arundinaceum and drummondii) and the tetraploids S. almum and S. halepense were analyzed for 17 enzyme systems encoded by 30 loci. Low levels of variation were found within and among accessions, although there was more variation than is typical of inbreeding species. We found an average of 3.2 alleles per locus in ssp. arundinaceum, with a mean expected heterozygosity for the accessions of 0.034 and total panmictic heterozygosity of 0.154. An analysis of the apportionment of genetic variation among accessions of ssp. arundinaceum indicated that 26% of the variation occurs within accessions and 74% among accessions. Cultivated sorghum contains far less allozymic variation than ssp. arundinaceum, its presumed progenitor. This is consistent with the prediction that cultivated sorghum experienced a loss of genetic variation during domestication. For the most part, cultivated sorghum contains a subset of the allozymes found in ssp. arundinaceum. Principal component analysis revealed continuous variation among the accessions and geographic regions, with accessions failing to segregate into discrete clusters. However, accessions of race virgatum of ssp. arundinaceum occupied one end of the continuum and were, in that sense, distinguished from the other accessions. Similarly, most accessions of S. halepense and S. almum occupied the central portion of the continuum. The allozymic data presented here are consistent with the hypothesized origin of S. halepense via autopolyploidy or segmental allopolyploidy.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 79 (1990), S. 305-313 
    ISSN: 1432-2242
    Schlagwort(e): Peroxidase ; Isoelectric focusing ; Hexaploid ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Isoelectric focusing (IEF) of extracts from different tissues of hexaploid wheat cv “Chinese Spring” provided a method of distinguishing and identifying the four known, and one newly discovered, sets of genes encoding peroxidase isozyme production.Per-1, carried on the short arms of homoeologous group 1 chromosomes, shows a high degree of conservation and is active in coleoptile tissue.Per-2, carried on the short arms of group 2 chromosomes, shows some polymorphism and is most active in root tissue.Per-3, on the long arms of group 3 chromosomes, is highly variable and most active in embryo tissue.Per-4, carried on chromosome arms7AS,4AL, and7DS, is quite variable and most active in endosperm tissue. (The chromosome nomenclature used in this paper is that agreed to by the 7th International Wheat Genetics Symposium, where the previous designations of4A and4B were reversed.) Restriction fragment length polymorphism (RFLP)-based maps of the group 7 chromosomes were used to locatePer-A4 to a distal region of7AS. In addition, a further set of genes was identified as being active in root tissue. In wheat a single locus,Per-D5, was found on chromosome arm2DS.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 81 (1991), S. 13-20 
    ISSN: 1432-2242
    Schlagwort(e): Potato ; Chloroplast DNA ; Sequence comparison ; Nucleotide substitution rate ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A deletion specific to chloroplast (ct) DNA of potato (Solanum tuberosum ssp. tuberosum) was determined by comparative sequence analysis. The deletion was 241 bp in size, and was not flanked by direct repeats. Five small, open reading frames were found in the corresponding regions of ctDNAs from wild potato (S. tuberosum ssp. andigena) and tomato (Lycopersicon esculentum). Comparison of the sequences of 1.35-kbp HaeIII ctDNA fragments from potato, tomato, and tobacco (Nicotiana tabacum) revealed the following: the locations of the 5′ ends of both rubisco large subunit (rbcL) and ATPase beta subunit (atpβ) mRNAs were probably the same as those of spinach (Spinacia oleracea); the promoter regions of the two genes were highly conserved among the four species; and the 5′ untranslated regions diverged at high rates. A phylogenetic tree for the three potato cultivars, one tomato cultivar, and one tobacco cultivar has been constructed by the maximum parsimony method from DNA sequence data, demonstrating that the rate of nucleotide substitution in potato ctDNA is much slower than that in tomato ctDNA. This fact might be due to the differences in the method of propagation between the two crops.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 641-647 
    ISSN: 1432-2242
    Schlagwort(e): Pinus ; Species hybridization ; Chloroplast DNA ; Molecular markers ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Restriction fragment analysis and heterologous hybridization of chloroplast (cp) DNA was used to develop species-specific markers for P. tabulaeformis, P. yunnanensis and P. massoniana. Fragment patterns created by the BclI and DraI restriction enzymes and hybridization patterns to the psbC and psbD probes were distinctive among the three species. No intraspecific variation was detected with respect to any of the cpDNA markers developed in this study. The cpDNA markers obtained were subsequently used to examine the parentage of P. densata, a putative Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The analysis demonstrated for the first time that P. densata populations accommodate chloroplast genomes of P. tabulaeformis and P. yunnanensis, which strongly supports earlier suggestions of the hybrid origin of this species. It appears that P. densata represents a stabilized natural hybrid that has become adapted to high mountain environments where neither of the parental species can normally grow.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 635-640 
    ISSN: 1432-2242
    Schlagwort(e): Pinus ; Species hybridization ; Allozymes ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Allozyme differentiation at 13 loci was studied in populations of Pinus tabulaeformis, P. densata, and P. yunnanensis from China. It was previously suggested that P. densata represents a Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The observed levels of allozyme variation within and among the investigated species were comparable to those of other conifers. P. tabulaeformis differed markedly from P. yunnanensis with respect to allozyme frequencies, while P. densata was intermediate between the two putative parents. There was evidence of homozygote excess in embryos from all investigated species, as compared to Hardy-Weinberg expectations. The observed allozyme composition of P. densata conformed to earlier morphological and molecular evidence indicating hybrid origin of this taxon. It was proposed that fusion of gene pools from P. tabulaeformis and P. yunnanensis has led to adaptive evolution of a new species, P. densata.
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  • 72
    Digitale Medien
    Digitale Medien
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    Theoretical and applied genetics 82 (1991), S. 57-64 
    ISSN: 1432-2242
    Schlagwort(e): Cultivated rice ; Wild rice ; RFLP ; Satellite DNA ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A 352-bp EcoRI fragment from rice DNA was cloned and shown to be a member of a tandem repeat. Sequence determination revealed homologies with human alpha satellite DNA and maize knob heterochromatin specific repeat. This 352-bp sequence is highly specific for the AA genome of rice. However, copy number and sequence organization are variable, depending on the accession analyzed. Several examples of amplification were observed in O. rufipogon and O. longistaminata. Use of resolutive polyacrylamide gel electrophoresis and 4-bp cutter enzymes allowed one to distinguish between the Indica and Japonica subtypes of O. sativa. The same method also discriminates between two groups of O. rufipogon, the presumed ancestor of O. sativa, suggesting that the present day Indica and Japonica subtypes originated independently from two O. rufipogon distinct populations.
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  • 73
    ISSN: 1615-6102
    Schlagwort(e): Cell division cycle ; Wheat ; cdc2 ; suc1 ; Protein kinase ; H1 histone kinase ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Thecdc2-like p34 protein of wheat is closely similar to the p34cdc2 enzyme of yeasts and animals since both have binding affinity for p13suc1 protein encoded by the fission yeastsuc1 gene. In yeast p13suc1 participates in modulation of p34cdc2 activity and is necessary for completion of mitosis. Wheat p34 that was affinity purified on p13suc1 contained the PSTAIR amino acid sequence that is present in all known p34cdc2 homologues and it also had H1 histone protein kinase activity that was independent of calcium and cyclic AMP, which is characteristic of p34cdc2 in vitro. Functional equivalence with the known cell cycle control protein supports our earlier proposition that the high level of this homologue in wheat leaf meristem is important in determining where cell division can occur and the capacity for resumption of cell division. The affinity of plant p34 for fission yeast p13suc1 suggested that a similar association occurs in plants. We have detected a plant homologue of pl3suc1 using affinity-purified antibody raised against the fission yeast protein, in wheat, pea andChlamydomonas. We conclude that the distribution of p13suc1 homologue in plants is likely to be ubiquitous. Thesuc1 gene function inSchizosaccharomyces pombe is essential for mitosis, in which it is required for inactivation of p34cdc2. We propose that association of plant p34 with p13suc1 is similarly involved in plant mitosis.
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  • 74
    ISSN: 1615-6102
    Schlagwort(e): Basal-body root complex ; Cell division cycle ; Centrosome ; Chlamydomonas ; Evolution ; Monoclonal antibody
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The mammalian centrosome monoclonal antibody MPM-13 recognized component(s) of the well defined MTOC basal-body root complex in the green plantChlamydomonas. The antibody reaction coincided in location with the basal-body root complex and the cruciate nature of the staining pattern corresponded to the configuration of the root microtubules. During mitosis the behaviour of MPM-13 stained material mirrored the duplication, separation and migration to the spindle poles of the basal body-root complex. It is suggested that conserved MTOC components were recognized and that these may have retained a similar, perhaps universal, function in microtubule organization.
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  • 75
    Digitale Medien
    Digitale Medien
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    Protoplasma 164 (1991), S. 54-69 
    ISSN: 1615-6102
    Schlagwort(e): Green algae ; Flagellar beat ; Video analysis ; Evolution ; Swimming patterns ; Prasinophyceae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The flagellar beat and swimming patterns of flagellated cells of 22 green plants, including 17 green flagellates (volvocalean and prasinophyte algae), motile cells of three seaweeds,Bryopsis, Caulerpa, andUlva, sperms of a liverwort,Marchantia, and a fern,Athyrium, were examined using a high-speed video system. So-called breast-stroke is widely distributed in green plants, and occurs rarely in prasinophyte flagellates and ulvophycean algae; in these algal groups flagellar beat similar to that found in animal sperm is common, both during forward and backward swimming. Different types of swimming patterns were observed in prasinophytes. The results indicate evolutionary trends of flagellar beat and swimming patterns in green plants such as change from backward to forward swimming, from flagellar to ciliary beating and from uni-directional (parallel) to radial-directional (cruciate) beating. Such trends are shown in two prasinophyte groups, thePyramimonas-lineage andTetraselmis-lineage.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Biology and philosophy 6 (1991), S. 59-80 
    ISSN: 1572-8404
    Schlagwort(e): Evolution ; semantic approach ; theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract Paul Thompson, John Beatty, and Elisabeth Lloyd argue that attempts to resolve certain conceptual issues within evolutionary biology have failed because of a general adherence to the received view of scientific theories. They maintain that such issues can be clarified and resolved when one adopts a semantic approach to theories. In this paper, I argue that such conceptual issues are just as problematic on a semantic approach. Such issues arise from the complexity involved in providing formal accounts of theoretical laws and scientific explanations. That complexity is due to empirical and pragmatic considerations, not one's adherence to a particular formal approach to theories. This analysis raises a broader question. How can any formal account properly represent the complex nature of empirical phenomena?
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Biology and philosophy 6 (1991), S. 81-92 
    ISSN: 1572-8404
    Schlagwort(e): Evolution ; fitness ; natural selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract This paper considers a variety of attempts to define fitness in such a way as to defend the theory of evolution by natural selection from the criticism that it is a circular argument. Each of the definitions is shown to be inconsistent with the others. The paper argues that the environment in which an animal evolves can be defined only with respect to the properties of the phenotype of the animal and that it is therefore not illuminating to try to explain the phenotypic properties of the animal in terms of adaptation to an environment that is defined by those very properties. Furthermore, since there is no way that the environment can be defined independently of the presence of the animal there is no way that the quality of an animal can be assessed; and there can be no objective criteria by whichany form of selection can be carried out, therefore there can be no criteria by whichnatural selection can be carried out. It is proposed that fitness is nothing more than the production of offspring, that this is a phenotypic property like all the others, and if it is heritable then the offspring of the parents that produce the most offspring will themselves produce the most offspring, and that in principle it is impossible to account for this in terms of the other phenotypic properties of the fittest animals except by circular argument. Differential rates of reproduction are the causes of evolution and the phenotypic causes are strictly inexplicable.
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  • 78
    ISSN: 1573-5036
    Schlagwort(e): Lycopersicon esculentum L. ; magnesium-manganese interaction ; magnesium: manganese ratio ; manganese toxicity ; tomato ; Triticum aestivum L. ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Results are reported for tomato (Lycopersicon esculentum L. var. Ailsa craig) and wheat (Triticum aestivum L. cv. Mara) which demonstrate that increasing concentrations of Mg in the plant raises plant tolerance to Mn toxicity. Water culture experiments with tomato show that under conditions of high Mn supply (200 µM, Mn), not only does increasing Mg application (0.75 mM to 15 mM) depress Mn uptake, but the higher Mg concentrations in the shoot counteract the onset of Mn toxicity when the concentrations of Mn in the shoot are also high. The ratio of Mg: Mn in the tissues is a better indicator of the appearance of toxicity symptoms than Mn concentration alone. Toxicity symptoms were observed when the Mg:Mn ratio in the shoot tissue was from 1.13 to a value between 3.53 and 6.54. The corresponding Mg: Mn ratio in the older leaves was from 0.82 to between 2.27 and 3.51. For wheat grown in soil, analyses of leaves revealed that growth could be expressed by the following relationship: Y=A+B exp(-kX), where Y=growth, X=Mg:Mn ratio, A, B and k=constants. Growth was significantly reduced when the Mg:Mn ratio fell below 20:1. From a measurement of this ratio it is therefore possible to predict the appearance of Mn toxicity and its influence on growth.
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  • 79
    ISSN: 1573-5036
    Schlagwort(e): calcium ; ear development ; magnesium ; potassium ; tissue press sap ; Triticum aestivum L. ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract For floret development and final grain number ear elongation in wheat (10–17d before anthesis) is the most sensitive period to adverse growth conditions. Sugars are supposedly the main factor determining floret numbers and grain set, and play next to potassium a significant role in establishing turgor pressure in young tissues. In view of this osmotic function, the influence of K on the concentration of water soluble carbohydrates (WSC, total of sucrose and reducing sugars), Ca and Mg was investigated in pot experiments. Further, the osmotic potential of sap extracted from young ears was determined and compared to sap extracted from the leaf blade. Plants supplied with low amounts of K (moderate K-deficiency) had a considerably lower K concentration in the press sap of the flag leaf and the ear than plants well supplied with K. Concentrations of WSC, Ca and Mg were higher in press sap of the flag leaf in K deficient plants than in plants adequately supplied with K. This indicates a substitution of K in its osmotic role. In press sap from ears, however, WSC, Ca and Mg were not influenced by the K application. Therefore, substances other than those measured must have been responsible for the osmoregulation in the young ear. WSC and the osmotic potential increased (more negative) independently on K supply during ear elongation, while K, Ca and Mg concentrations decreased. Whereas grain number was not influenced by the treatment, single grain weight at maturity was reduced by low K availability in the soil.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 124 (1990), S. 303-307 
    ISSN: 1573-5036
    Schlagwort(e): models ; potassium uptake ; Triticum aestivum L. ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Spring wheat was grown in the field under deficient and sufficient levels of soil K and with high and low supplies of fertiliser nitrogen. Measurements were made of K uptake, soil nutrient supply parameters, root growth and, in solution culture, root influx parameters. Mechanistic models predicted uptake reasonably well under K-deficient conditions, but over-predicted uptake, by as much as 4 times, under K-sufficient conditions. The over-prediction was apparently due to poor characterisation of plant demand.
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  • 81
    ISSN: 1573-5036
    Schlagwort(e): Cu levels ; N sources ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A pot experiment was conducted, in a greenhouse, at Hisar, India, using a sandy soil deficient in nitrogen and copper, to study the effects of various levels of N and Cu on the dry matter yield and the N and Cu contents of wheat (Triticum aestivum L.). The sources of nitrogen used were Ca(NO3)2, NH4Cl and NH4NO3 applied in amounts necessary to establish 120 ppm of soil nitrogen and using a control (0 ppm N). Copper was applied, as copper chloride, to give soil Cu levels of 0, 5, 10 and 20 ppm. In general, dry matter yields, N and Cu concentrations in shoots and roots and available soil-N after harvest of the plants, followed the order Ca(NO3)〉NH4NO3〉NH4Cl. Up to a level of 5 ppm Cu, the dry matter yields of shoots and roots increased, but decreased at higher levels of Cu. Increasing Cu levels significantly decreased the available soil-nitrogen after harvest and also the concentration of N in the plants. At the same time the concentration of Cu in shoots and roots and available Cu in the soil was increased. Nitrogen and copper were found to have a mutually antagonistic effect on each other's concentration in the plants. The antagonism was greater with NH4 + sources than with NO3 − compounds.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    European journal of plant pathology 96 (1990), S. 187-198 
    ISSN: 1573-8469
    Schlagwort(e): fusarium head blight ; Fusarium culmorum ; F. graminearum ; wheat ; mycotoxin ; deoxynivalenol ; nivalenol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Beschreibung / Inhaltsverzeichnis: Samenvatting Aaraantasting van tarwe doorFusarium culmorum enFusarium graminearum leidt tot vorming van mycotoxinen in het graan, waarvan deoxynivalenol (DON) en nivalenol (NIV) de belangrijkste toxinen zijn. In dit artikel wordt een overzicht gegeven van de toxicologische aspecten, en het voorkomen van deze toxinen in tarwe. Informatie over DON en NIV in tarwe in West-Europa is schaars. Gebaseerd op gegevens vanFusarium epidemieën in de jaren 1979–1986 wordt een schatting gegeven van de concentratie DON in Nederlandse tarwe. Rekening houdend met de herkomst en verwerking van tarwe, blijken zowel in dierlijk als menselijk voedsel lage concentraties DON chronisch voor te komen. Op basis van een maximaal toelaatbare dagelijkse dosis DON van 3 μg kg−1 lichaamsgewicht is de schatting van de dagelijkse opname van DON in het jaar volgend op de oogst van 1982 net op de grens. Zowel een jaarlijkse inventarisatie vanFusarium aantasting en DON besmetting van het graan, als de ontwikkeling vanFusarium-resistente rassen zijn noodzakelijk.
    Notizen: Summary An infection of bread wheat by fusarium head blight contaminates the crop with mycotoxins, particularly deoxynivalenol (DON) and nivalenol (NIV). The toxicity and natural occurrence of these mycotoxins in wheat are reviewed. Based on 8 years data of fusarium head blight epidemics of wheat in the Netherlands, DON contamination of the grain was estimated. Fusarium head blight ratings averaged an infection of 1.7% of all spikelets; estimates for DON contamination averaged 0.9 mg kg−1. Taking a guideline level for DON in uncleaned bread wheat of 2 mg kg−1, in 1979 and 1982 a wheat crop was produced with estimated DON concentrations above the limit of tolerance. Human and animal exposure to mycotoxins in the Netherlands appears to be small but chronic. The information presented in this paper illustrates the need for an annual evaluation of the crop for fusarium head blight incidence and mycotoxin content, and the necessity of fusarium head blight resistant wheat cultivars.
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  • 83
    Digitale Medien
    Digitale Medien
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    Evolutionary ecology 4 (1990), S. 130-142 
    ISSN: 1573-8477
    Schlagwort(e): Evolution ; Darwin's finches ; extinction ; Geospizinae ; island biogeography ; ecological isolation ; reproductive isolation ; speciation ; taxon cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Hamilton-Rubinoff model of evolution in the avifauna of the Galapagos Islands suggests that speciation occurs on small outlying islands, and that new species invade the central island region, where ecological differentiation takes place. I present an alternative model in which both speciation and ecological differentiation leading to origin of actively colonizing taxa occur on the large islands, with colonization of small and outlying islands being primarily one way. Although forms on outlying islands may differentiate to the level of new species, their fate is postulated to be extinction rather than re-invasion of central islands. Data on species with expanding, differentiating, fragmenting, and relict distributions support this second model. Polytypy and incompleteness of distributions on the large islands indicate that isolation is adequate for differentiation to occur. Distributions of expanding taxa centre on the large islands, and their distributions show sequences leading from large islands to smaller and more outlying islands. Curves of occupancy of large islands versus total islands also agree with the prediction that expansions begin in the large islands.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 224 (1990), S. 459-468 
    ISSN: 1617-4623
    Schlagwort(e): Flaveria ; C3/C4 plants ; Phosphoenolpyruvate carboxylase ; Gene family ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Phosphoenolpyruvate carboxylase (PEPCase) was shown to be encoded by a multigene family in various Flaveria species analysed. Several clones were isolated from genomic libraries of F. pringlei (C3 species) and F. trinervia (C4 species) and classified into four distinct groups according to their hybridization behaviour to a full-length cDNA clone encoding the PEPCase C4 isozyme of F. trinervia. A detailed cross-hybridization analysis demonstrated that the closest relative of most of the PEPCase genes isolated from F. trinervia and F. pringlei was not found in the same but in the other species. Northern analysis, using stringent conditions, allowed discrimination of class-specific PEPCase transcripts and revealed characteristic organ-specific expression patterns.
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  • 85
    ISSN: 1617-4623
    Schlagwort(e): Aspergillus nidulans ; Gene regulation ; amdS gene ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In Aspergillus nidulans expression of the acetamidase structural gene, amdS, is under the control of at least four regulatory genes including the trans-acting amdA regulatory gene. A cis-acting mutation (amdI66) consisting of an 18 by duplication in the 5′ region of the amdS gene results in very high levels of acetamidase activity but only in strains carrying semi-dominant mutations in the amdA gene. In selecting for increased amdS expression in an amdI66 amdA – strain, an A. nidulans strain with a mutation in the 5′ region of the amdS gene was isolated. The nucleotide sequence was determined of the region containing the mutation, designated amdI666. The mutant strain carries three tandem copies of the 18 by sequence that is duplicated in the amdI66 mutation. Thus, from a strain carrying a duplication of an apparent regulatory protein binding site with little effect on gene expression, a strain has been derived that carries a triplication of the site with consequent major effects on regulation. The multiple copies of regulatory sites present in many genes may have been generated by a similar mechanism.
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  • 86
    Digitale Medien
    Digitale Medien
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    Molecular genetics and genomics 221 (1990), S. 315-321 
    ISSN: 1617-4623
    Schlagwort(e): Small stable RNA ; Signal recognition particle ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The genes encoding the 7S RNAs of the archaebacteria Archaeoglobus fulgidus, Methanosarcina acetivorans, Sulfolobus solfataricus, and Thermococcus celer have been isolated. All four genes occur as single genomic copies and are flanked by sequences containing potential signals for transcriptional promotion and termination. The genes encode RNA molecules approximately 300 nucleotides in length which conform strictly to a model of secondary structure common to all described archaebacterial 7S RNAs. Archaebacterial 7S RNAs exhibit a strong similarity to eukaryotic 7S RNAs in terms of overall secondary structure, while primary sequence conservation is limited to a specific structural domain of the molecule. This domain displays strong primary and secondary structural similarity to features of small eubacterial RNAs, including the small cytoplasmic (sc) RNA of Bacillus subtilis and the 4.5S RNA of Escherichia coli. Conservation of this structural domain among divergent RNA molecules across three kingdoms suggests that these RNAs are the descendants of a unique subcellular structure present before the divergence of the archaebacterial, eubacterial and eukaryotic kingdoms.
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  • 87
    ISSN: 1615-6110
    Schlagwort(e): Angiosperms ; Leguminosae ; Medicago truncatula f.laxicycla ; M. laxispira ; Evolution ; adaptation ; seed germination ; chromosome number ; Flora of Libya
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Medicago truncatula is a member ofMedicago sect.Spirocarpos, in which all 34 species have coiled fruit, usually tightly coiled, that permanently retain the seeds. A variant ofM. truncatula from Libya is unique for the species in possessing very loosely coiled fruits, and is here recognized as a new forma,M. truncatula f.laxicycla E. Small. In germination tests of a number of species ofMedicago, the unusual Libyan variant proved to be the only one in which rapid and simultaneous germination of most of the seeds occurred while still within a fruit. The loose coiling of the fruit of the Libyan variety appears to facilitate water entry and seedling escape. Its rapid germination might adapt it to respond quickly to intermittently available moisture, but at the cost of abandoning the strategy of intermittent germination adopted by other populations ofMedicago sect.Spirocarpos.
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  • 88
    Digitale Medien
    Digitale Medien
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    Molecular genetics and genomics 228 (1991), S. 324-327 
    ISSN: 1617-4623
    Schlagwort(e): Yolk proteins ; Gene families ; Evolution ; Egg production ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The yolk proteins of Drosophila melanogaster comprise a family of three related yolk polypeptides each encoded by a single-copy gene. We show by genetic crosses that each gene makes an equivalent contribution to the fecundity and fertility of the female and they do not individually provide unique functions to the embryo. We show that the number of eggs laid by a female depends upon the number of genes encoding yolk polypeptides present in the genome and furthermore that the probability of an egg hatching into an adult also critically depends upon the number of yolk protein genes present in the mother. This suggests that the three yolk protein-encoding genes in Drosophila melanogaster may have arisen by duplication, then been maintained for quantitative reasons because they increased egg production and fertility, rather than each protein evolving a different function as is the case with most small gene families, such as tubulins and collagen genes.
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  • 89
    Digitale Medien
    Digitale Medien
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    Molecular genetics and genomics 231 (1991), S. 53-58 
    ISSN: 1617-4623
    Schlagwort(e): Chlamydomonas moewusii ; Mitochondrial DNA ; Map ; Gene localization ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We report that the mitochondrial genome of Chlamydomonas moewusii has a 22 kb circular map and thus contrasts with the mitochondrial genome of Chlamydomonas reinhardtii, which is linear and about 6 kb shorter. Overlapping restriction fragments spanning over 90% of the C. moewusii mitochondrial DNA (mtDNA) were identified in a clone bank constructed using a Sau3AI partial digest of a C. moewusii DNA fraction enriched for mtDNA by preparative CsCI density gradient centrifugation. Overlapping Sau3AI clones were identified by a chromosome walk initiated with a clone of C. moewusii mtDNA. The mtDNA map was completed by Southern blot analysis of the C. moewusii mtDNA fraction using isolated mtDNA clones. Regions that hybridized to C. reinhardtii or wheat mitochondrial gene probes for subunit I of cytochrome oxidase (cox1), apocytochrome b (cob), three subunits of NADH dehydrogenase (nadl, nad2 and nad5) and the small and the large ribosomal RNAs (rrnS and rrnL, respectively) were localized on the C. moewusii mtDNA map by Southern blot analysis. The results show that the order of genes in the mitochondrial genome of C. moewusii is completely rearranged relative to that of C. reinhardtii.
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 231 (1991), S. 106-112 
    ISSN: 1617-4623
    Schlagwort(e): Serine tDNAs ; Glutamine tDNA ; Bovine consensus sequence ; Short interspersed nuclear element ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A bovine tRNA gene cluster has been characterized and the sequences of four tDNAs determined. Two of the tDNAs could encode tRNASer IGA, one tDNASer UGA, and the fourth tRNAGln CUG. The three serine tDNAs representing the UCN codon isoacceptor family are almost identical. However, the sequence of the tDNASer TGA differs from a previously sequenced bovine tDNASer TGA at 12 positions (ca. 14%). This finding suggests that in the bovine genome, two subfamilies of genes might encode tRNASer UGA. It also raises the possibility that new genes for a specific UCN isoacceptor might arise from the genes of a different isoacceptor, and could explain previously observed differences between species in the anticodons of coevolving pairs of tRNAsSer UCN. The gene cluster also contains complete and partial copies, and fragments, of the BCS (bovine consensus sequence) SINE (short interspersed nuclear element) family, six examples of which were sequenced. Some of these elements occur in close proximity to two of the serine tDNAs.
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  • 91
    ISSN: 1617-4623
    Schlagwort(e): Archaebacteria ; Evolution ; Gene cluster ; Halobacterium marismortui ; Ribosomal protein genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nucleotide sequence has been determined of a 4700 by region from a ribosomal protein gene cluster of Halobacterium marismortui (Haloarcula marismortui), which is equivalent to part of the spectinomycin operon of Escherichia coli. The genes were localized on the recombinant λEMBL3 clone PP*7, which also contains several other ribosomal protein genes from the DNA region in H. marismortui equivalent to the linked S10/spc operon. The genes analysed encode ten ribosomal proteins, namely HmaL5, HmaS14, HmaS8, HmaL6, HL5, HL24, HmaL18, HmaS5, HmaL30 and HmaL15. The gene organization of the archaebacterial cluster is similar to that in eubacteria but has two additional genes, namely those encoding HL5 and HL24, which were identified as extra proteins that are apparently not present in E. coli. These correspond to the gene products of orfd and orfe in Methanococcus vannielii and also have eukaryotic counterparts.
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  • 92
    ISSN: 1573-5036
    Schlagwort(e): Gaeumannomyces graminis ; genotypes ; interaction ; manganese ; oxidation ; take-all ; Triticum aestivum ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Take-all is a world-wide root-rotting disease of cereals. The causal organism of take-all of wheat is the soil-borne fungus Gaeumannomyces graminis var tritici (Ggt). No resistance to take-all, worthy of inclusion in a plant breeding programme, has been discovered in wheat but the severity of take-all is increased in host plants whose tissues are deficient for manganese (Mn). Take-all of wheat will be decreased by all techniques which lift Mn concentrations in shoots and roots of Mn-deficient hosts to adequate levels. Wheat seedlings were grown in a Mn-deficient calcareous sand in small pots and inoculated with four field isolates of Ggt. Infection by three virulent isolates was increased under conditions which were Mn deficient for the wheat host but infection by a weakly virulent isolate, already low, was further decreased. Only the three virulent isolates caused visible oxidation of Mn in vitro. The sensitivity of Ggt isolates to manganous ions in vitro did not explain the extent of infection they caused on wheat hosts. In a similar experiment four Australian wheat genotypes were grown in the same Mn-deficient calcareous sand and inoculated with one virulent isolate of Ggt. Two genotypes were inefficient at taking up manganese and were very susceptible to take-all, one was very efficient at taking up manganese and was resistant to take-all, and the fourth genotype was intermediate for both characters. All genotypes were equally resistant under Mn-adequate conditions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 133 (1991), S. 93-100 
    ISSN: 1573-5036
    Schlagwort(e): cultivars ; growth inhibition ; hydrogen cyanide ; lettuce ; Pseudomonas fluorescens ; volatile metabolites ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Lettuce and wheat cultivars, differing in reaction to root inoculation with plant growth-inhibitory bacteria, were tested for sensitivity to (i) gaseous metabolites produced by deleterious, cyanogenic isolates of Pseudomonas fluorescens, and to (ii) pure cyanide. Reactions were read as shoot and/or root elongation after exposure of seedlings to the volatiles in vitro. Lettuce cultivar Salad Bowl was significantly less sensitive than cv. Montana, both to bacterial volatiles and to pure cyanide, and a similar difference between these cultivars was also obtained in greenhouse experiments where bacteria were inoculated directly on the roots. Cultivar differences were, however, not recorded, either in vitro or in the greenhouse, when the bacteria were grown on a medium which did not support cyanide production. In wheat, a difference in sensitivity to bacteria-produced volatiles was recorded between two cultivars (Drabant and Besso) differing in reaction to bacterial inoculation, but in contrast to lettuce cultivars, the wheat cultivars tested did not react differentially to pure cyanide. The results suggest that in lettuce differential sensitivity to cyanide is one factor behind cultivar differences in reaction to the bacteria tested, even though bacterial metabolites other than cyanide may contribute to the plant growth inhibition recorded. In wheat, however, differential cultivar responses to these bacteria could not be shown to be related to cyanide.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 59 (1991), S. 1-8 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; root ; combining ability ; correlation ; dry matter ; variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Wheat root characters which influence vital plant processes have scarcely been explored for their genetic control. This study was conducted to i) examine the diversity of root traits and associated shoot traits in spring wheat (Triticum aestivum L.) cultivars; ii) study the nature of genetic control of selected traits; and iii) examine associations among root and shoot traits. Three experiments were conducted in the greenhouse with plants grown in the vermiculite medium in clear plastic tubes. In the first experiment, 42 spring wheat cultivars were grown for three weeks and measurements were taken on root length, leaf length, root number, leaf number, root dry weight, and top dry weight. In the second study, 15F1's originating from a partial diallel mating of six cultivars along with the parents were evaluated for 4 weeks. The data on root length, leaf length, and root number were subjected to diallel analysis according to Griffing's method 4, fixed model. A third experiment consisted of studying 2 F2 populations with 141 plants per population. In the first study the 42 cultivars exhibited a wide range of variation for all six traits. Diallel analysis revealed significant effects of both general combining ability (GCA) and specific combining ability (SCA) for root length, leaf length, and root number. Parents with high GCA estimates were identified. Significant positive correlation coefficients were found among root and shoot traits. Analysis of F2's for root length indicated quantitative nature of inheritance of root length.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 45 (1990), S. 71-80 
    ISSN: 1573-5060
    Schlagwort(e): wheat ; Triticum aestivum ; wheat leaf rust ; Puccinia recondita f.sp. tritici ; partial resistance ; histology ; growth curve
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The average size of wheat leaf rust colonies, measured using epifluorescence microscopy was significantly larger in the highly susceptible genotype Morocco than in the susceptible genotype Kaspar and the partially resistant genotypes Westphal 12A, Akabozu and BH 1146. This was already so three days after inoculation. Colony growth in partially resistant genotypes was continuously retarded compared to colonies in the highly susceptible genotype Morocco. No evidence was found for an initial inhibition of the growth of colonies in partially resistant genotypes. In partially resistant genotypes formation of uredial beds and sporulating areas started at a smaller colony size than in susceptible genotypes. Wheat leaf rust colonies in primary leaves of all genotypes studied were much larger than colonies in flag leaves measured at the same number of days after inoculation. Growth and sporulation of not intertwined colonies was not influenced by either a high or a low number of neighbouring colonies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 45 (1990), S. 81-86 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; Puccinia recondita f.sp. tritici ; wheat leaf rust ; partial resistance ; histology ; abortion ; adult plant resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Arrest of the growth of wheat leaf rust infection structures was studied with fluorescence microscopy in seedling leaves and flag leaves of the susceptible spring wheat genotypes Morocco and Kaspar and the partially resistant genotypes Westphal 12A and Akabozu. The percentages non-penetrants and substomatal vesicle abortion were low in all genotypes. In the partially resistant genotypes the percentage abortion of infection structures was higher than in the susceptible genotype Morocco. Aborted infection structures had formed one or two haustorial mother cells. In adult plants differences in the percentage aborted infection structures between susceptible and partially resistant genotypes were more pronounced than in seedlings. The so-called late abortion was not observed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 45 (1990), S. 59-69 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; Pyrenophora tritici-repentis ; resistance ; tan spot ; yellow spot ; variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary No complete resistance to Pyrenophora tritici-repentis has been located in more than 1400 bread wheats examined. Incomplete resistance, however, occurs at different levels in many spring and winter types and data are presented for the strongest sources of resistance detected. In particular, there is a high frequency of Brazilian spring wheats with appreciable levels of resistance to this pathogen. Recent international nurseries from CIMMYT, Mexico, also contain numerous potentially valuable sources of resistance and these wheats may be shorter and higher yielding in Australia than the Brazilian wheats. The resistances in many Brazilian cultivars may be largely common because the cultivars are often strongly interrelated. Some of the Brazilian wheats resistant to P. tritici-repentis are also resistant to one or more of the septoria diseases and/or possess tolerance to aluminium toxicity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 45 (1990), S. 87-92 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; near-isogenic lines ; NILs ; Puccinia recondita f.sp. tritici ; leaf rust ; Puccinia striiformis ; yellow rust ; backcross ; variation ; background resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Using the cultivar Arina as the recurrent parent, six backcrosses were made with two donor lines carrying the leaf rust resistance genes Lr1 and Lr9, respectively. Selection for leaf rust resistance occurred at the seedling stage in the greenhouse; the first plants transferred to the field were BC6F4s. Frequency distribution of the 332 Lr1/7 × Arina and the 335 Lr9/7 × Arina lines showed continuous variation for yellow rust resistance and heading date in these leaf rust near-isogenic lines (NILs). Similar results were also obtained for plant height, for resistance to powdery mildew and glume blotch, as well as for baking quality characters in another set of more advanced NILs. The available information on the behaviour of one of the parents of cultivar Arina led to the conclusion that the expressed yellow rust resistance is quantitative and might possibly be durable.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 45 (1990), S. 169-177 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; coefficient of parentage ; pedigree ; gene pool
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Pedigrees of 142 Yugoslavian winter wheat cultivars were traced to 110 ancestral genotypes, of which 41 contributed significantly. In each of the four major Yugoslavian wheat breeding programs, the most important ancestor, as evaluated by mean coefficient of parentage, was ‘Akagomughi’, source of the genes Rht8 and Ppd1. The other 13–19 ancestors accounting for the majority of the remaining germplasm, varied considerably among institutions. The relative contributions of ancestors changed little between the periods 1967–76 and 1982–86, with the exception of ‘Neuzucht’ (source of a 1B/1R translocation), which became much more important in the latter period.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 46 (1990), S. 149-155 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; selection ; preharvest sprouting ; germination ; kernel color ; dormancy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The utility of spike- and seed-based mass selection techniques for improving preharvest sprouting resistance in heterogeneous wheat (Triticum spp.) populations was evaluated. Sorting seed by size improved selection efficiency in some cases, putatively by physiological synchronization. Progeny testing, as well as changes in frequency of red-kernelled types, indicate effectiveness of both spike- and seed-based mass selection for reduced preharvest sprouting. Differential effectiveness of mass selection, in populations segregating for dormancy from different sources, is consistent with previous work on mechanisms of dormancy from these sources. These results are of value to improvement of preharvest sprouting resistance in large, heterogeneous wheat populations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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