Differential human impact and vegetation history in two adjacent Pyrenean valleys in the Ariège basin,southern France,from 3000 B.P. to the present

Detailed palynological studies in two adjoining French Pyrenean valleys, complemented by the study of archives, demonstrate that under similar climatic conditions, the forest history of each valley from the Bronze Age to present time was essentially determined by socio-economical constraints, possibly modified by natural characteristics such as topography. The studies show why the expansion of Fagus (beech) at c. 4000 B.P. was asynchronous on the northern slope of the Pyrenees and emphasize the effects of the human impact on the recent lowering of the tree-line.A contribution to the 8th IPC, Aix-en-Provence, 1992     

Differential accumulation of four phaseolin glycoforms in transgenic tobacco

An intron-less phaseolin gene [15] was used to express phaseolin polypeptides in transgenic tobacco plants. The corresponding amounts of phaseolin immunoreactive polypeptides and mRNA were similar to those found in plants transformed with a bean genomic DNA sequence that encodes an identical -phaseolin subunit. These results justified the use of the intron-less gene for engineering of the phaseolin protein by oligonucleotide-directed mutagenesis. Each and both of the two Asn residues that serve as glycan acceptors in wild-type phaseolin were modified to prevent N-linked glycosylation. Wild-type (wt^i–) and mutant phaseolin glycoforms (dgly ₁, dgly ₂ and dgly _1,2) were localized to the protein body matrix by immunogold microscopy. Although quantitative slot-blot hybridization analysis showed similar levels of phaseolin mRNA in transgenic seed derived from all constructs, seed from the dgly ₁ and dgly ₂ mutations contained only 41% and 73% of that expressed from the wild-type control; even less (23%) was present in seed of plants transformed with the phaseolin dgly _1,2 gene. Additionally, the profile of 25–29 kDa processed peptides was different for each of the glycoforms, indicating that processing of the full-length phaseolin polypeptides was modified. Thus, although targeting of phaseolin to the protein body was not eliminated by removal of the glycan side-chains, decreased accumulation and stability of the full-length phaseolin protein in transgenic tobacco seed were evident.Abbreviations bp base pair(s) - DAF days after flowering - GUS -glucuronidase - kb kilobase - kDa kilodalton     

Demography,genealogy and genetics. The reproductive process in the populations of two French Mountain Valleys from the seventeenth to the twentieth century

An exhaustive analysis of registers of births, deaths, and marriages is used to reconstitute genealogies, both ascending and descending, for all individuals who lived in two mountain valleys: the Valserine valley (in the French Jura), which is studied from the end of the seventeenth century to the present, and the Vallouise valley (in the French Alps) studied from the seventeenth to the nieteenth centuries. This genealogical approach makes it possible to trace the reproductive process in the populations whose members lived in the valley for several generations. The Vallouise valley forms an important demographic isolate; nearly 98 per cent of those born between 1820 and 1849 were descendants of ancestors who had lived in the valley two centuries earlier. By contrast, there has been continuous immigration into the Valserine valley, which has resulted in a constant renewal of the gene pool. Only 18 per cent of the gene pool of individuals living in this valley two centuries later was contributed by those who lived in the valley and who were born before 1750.     

Stratigraphy,facies and synsedimentary tectonics in the Jurassic Rosso Ammonitico Veronese (Altopiano di Asiago,NE Italy)

Summary The red, pelagic limestones of the Rosso Ammonitico Veronese (Upper Bajocian-Tithonian) of the Altopiano di Asiago area can be subdivided into eight facies. They differ from each other in structure (bedding style, presence and type of nodularity) and texture (nature of components, grain-vs mud-support, compactional features). Several discontinuities could be recognized, based on sedimentological or biostratigraphic evidence. In the context of a drowned platform, where sediments essentially consist of skeletal remains of both planktonic and benthic organism, the different facies are interpreted as reflecting a varying influence of currents on the winnowing of micrite and on triggering early cementation. Early cementation in turn, controlled the patterns of bioturbation and the response of sediments to later compaction and pressure-dissolution. At times, microbial mats, of unidentified nature, were important in trapping and binding sediment, giving rise to early lithified nodules and layers of stromatolitic aspect. The Rosso Ammonitico Veronese can be subdivided into three units: lower Rosso Ammonitico (RAI: Upper Bajocian-Lower Callovian), middle Rosso Ammonitico (RAM: Upper Callovian-Middle Oxfordian), and upper Rosso Ammonitico (RAS: Lower Kimmeridgian-Tithonian). Frequent ammonite moulds allow the precise dating of the base and top of each unit, and the documentation of facies heteropies and hiatusses in the more fossiliferous RAS. The lower unit (RAM) is massive and essentially nodular; the middle unit (RAM) is well bedded, non-nodular, and cherty; the upper unit (RAS) is richer in clay and typically nodular. The RAI and the RAS are present everywhere, though significant facies and thickness changes affect particularly the RAS; the RAM is much more variable, ranging from 0 to 10 metres. These variations, that may be gradual or abrupt, are inter-preted as the result of Middle-Late Callovian block-faulting which generated an irregular sea floor topography where the swells were more exposed to currents that continuously removed sediments, inducing long-lasting periods of nondeposition. Sediments preferentially accumulated in the adjacent lows. A confirmation of this hypothesis is provided by evidence of synsedimentary tectonics, described for the first time in the Rosso Ammonitico Veronese. Neptunian dykes, both vertical and horizontal, are developed at the top of the RAI and are filled with laminated sediments or collapse breccias. Glides of metre-size blocks and slumps are present at the top of the RAI and at the base of the RAM, respectively. Cm-thick layers of mud supported breccias are intercalated in the upper part of the RAI and within the RAM: they are interpreted as seismites. All these features document a tensional regime that generated fractures in more or less lithified sediments and failure along steep fault scarps or gently dipping slopes of tilted fault blocks. Recognition of this Callovian-Oxfordian tectonic activity shows that, after the Bajocian drowning, the Trento Plateau did not simply experience a uniform and general foundering: a small-scale block-faulting was still active and affected the pattern of facies distribution.     

The Origin of the Oxidative Burst in Plants

A large number of publications recently have drawn strong analogies between the production of active oxygen species in plant cells and the “oxidative burst” of the phagocyte, even to the point of constructing elaborate models involving receptor mediated G-protein activation of a plasmalemma NADPH oxidase in plant cells. However there are potentially other active oxygen species generating systems at the plant cell surface. The present work examines these alternatives with particular emphasis on the rapid production of active oxygen species, in common with a number of other systems, by suspension-cultured cells of French bean on exposure to an elicitor preparation from the fungal pathogen Colletotrichum lindemuthianum. The cells show a rapid increase in oxygen uptake which is followed shortly afterwards by the appearance of a burst of these active oxygen species, as measured by a luminescence assay, which is probably all accounted for by hydrogen peroxide. An essential factor in this production of H₂O₂ appears to be a transient alkalinization of the apoplast where the pH rises to 7.0-7.2. Dissipation of this pH change with a number of treatments, including ionophores and strong buffers, substantially inhibits the oxidative burst. Little evidence was found for enhanced activation of a membrane-bound NADPH oxidase. However the production of H₂O₂ under alkaline conditions can be modelled in vitro with a number of peroxidases, one of which, an M_r 46,000 wall-bound cationic peroxidase, is able to sustain H₂O₂ production at neutral pH unlike the other peroxidases which only show low levels of this reaction under such conditions and have pH optima at values greater than 8.0. On the basis of such comparative pH profiles between the cells and the purified peroxidase and further inhibition studies a direct production of H₂O₂ from the wall peroxidase in French bean cells is proposed. These experiments may mimic some of the responses to plant pathogens, particularly the hypersensitive response, which is an important feature of resistance. A cell wall peroxidase-origin for the oxidative burst is clearly different from a model consisting of receptor activation of a plasmaiemma-localised NADPH oxidase generating superoxide. An alternative simple and rapid mechanism thus exists for the generation of H₂O₂ which does not require such multiple proteinaceous components.     

Deep-water stromatolites andFrutexites Maslov from the early and Middle Jurassic of S-Germany and Austria

Summary Despite extensive discussions during the last 20 years stromatolites are still used by many geologists as unequivocal indicators of very shallow-water conditions. We investigated four stratigraphic units from the Lower and Middle Jurassic of southern Germany (Posidonien-Schiefer, Amaltheen-Ton) and of the Northern Calcareous Alps (Adneter Kalk, Klauskalk), which were formerly interpreted as shallow marine sediments by some authors due to the occurrence of stromatolites. Our interpretations of the macro-, micro- and ultrafacies of these sediments are not compatible with shallow-water settings. We therefore propose a deep-marine, aphotic origin of these stromatolites. Former interpretations of the Posidonien-Schiefer as a shallow-water deposit are mainly based on the occurrence of stromatolites. We favour the model of a temporarily stagnant, deep, aphotic basin for these planktonrich sediments. Particles resembling ooids, but lying within mudstones cannot be taken as evidence for shallow agitated water. They either formed within the mud or are allochthonous. The deep-water setting of the red limestone of the Alpine Early and Middle Jurassic is indicated by a lack of platform-typical components like coated grains and phototrophic benthos and by shells of plankton and nekton forming a major part of the sediment. Stromatolites occur on the steep slope of a drowned Rhaetian reef with an estimated relief of 50–100 m and immediately below and within radiolarian limestones, deposited below the aragonite compensation depth (ACD). The aphotic stromatolites show some morphological differences to their shallow water counterparts. In all of our sections they occurred during intervals of reduced sedimentation. They form only thin horizons and probably grew very slowly. Mineralizations by Fe−Mn oxides and phosphate are very common. The presence of a microbial film is evident from binding of sedimentary particles, but the nature of the microbes is not known. Growth habits within the very distinct environments of red limestone and black shales show some common features, but also clear differences. The microproblematicumFrutexites Maslov is a very common component in deep-water stromatolites, but may also itself form small crusts or dendrolites. It occurs in two different forms. Opaque, slender forms with indistinct outlines probably grew within the weakly lithified sediment. Thicker, transparent forms with well defined outlines are found in cavities and probably also grew on the seafloor. Well preserved specimens display an internal fabric of radially arranged fibres of Fe−Mn oxides and calcite. It is suggested that calcite or aragonite were one original mineralogy ofFrutexites, which was later replaced by Fe−Mn oxides or phosphate. It is not certain whetherFrutexites is an organic, biomineralized structure or an inorganic mineralization, but the variable mineralogy and growth forms in different environments point to an organic origin. But even if organic, the occurrence in cryptic habitats and negative phototactic growth-directions make it clear thatFrutexites was not phototrophic.     

Ecology and biology ofNoctuidonema guyanense (Nematoda,aphelenchoididae), an ectoparasite ofSpodoptera frugiperda (Lep., Noctuidae), in French Guiana

Male and female moths ofSpodoptera frugiperda (J. E. Smith), collected in French Guiana between 1980 and 1987 were examined to evaluate the level of parasitism by the Aphelenchoidid ectoparasitic nematodeNoctuidonema guyanense Remillet &; Silvain. The rate of parasitism varies according to the population level ofS. frugiperda, the sex of the moths, number of matings, and age of the females. The results confirm that the transmission of the nematode from one moth to another occurs during mating. The growth of a nematode colony on a moth seems to be limited by the development of the physiological state of the host.     

Phylogeny of Saxifraga section Saxifraga subsection Arachnoideae (Saxifragaceae) and the origin of low elevation shade-dwelling species

Saxifraga section Saxifraga subsection Arachnoideae is a lineage of 12 species distributed mainly in the European Alps. It is unusual in terms of ecological diversification by containing both high elevation species from exposed alpine habitats and low elevation species from shady habitats such as overhanging rocks and cave entrances. Our aims are to explore which of these habitat types is ancestral, and to identify the possible drivers of this remarkable ecological diversification. Using a Hybseq DNA-sequencing approach and a complete species sample we reconstructed and dated the phylogeny of subsection Arachnoideae. Using Landolt indicator values, this phylogenetic tree was used for the reconstruction of the evolution of temperature, light and soil pH requirements in this lineage. Diversification of subsection Arachnoideae started in the late Pliocene and continued through the Pleistocene. Both diversification among and within clades was largely allopatric, and species from shady habitats with low light requirements are distributed in well-known refugia. We hypothesize that low light requirements evolved when species persisting in cold-stage refugia were forced into marginal habitats by more competitive warm-stage vegetation. While we do not claim that such competition resulted in speciation, it very likely resulted in adaptive evolution.     

Rapid changes in oxidative metabolism as a consequence of elicitor treatment of suspension-cultured cells of French bean (Phaseolus vulgaris L.)

Stressed plant cells often show increased oxygen uptake which can manifest itself in the transient production of active oxygen species, the oxidative burst. There is a lack of information on the redox status of cells during the early stages of biotic stress. In this paper we measure oxygen uptake and the levels of redox intermediates NAD/NADH and ATP and show the transient induction of the marker enzyme for redox stress, alcohol dehydrogenase. Rapid changes in the redox potential of elicitor-treated suspension cultures of French bean cells indicate that, paradoxically, during the period of maximum oxygen uptake the levels of ATP and the NADH/NAD ratio fall in a way that indicates the occurrence of stress in oxidative metabolism. This period coincides with the maximum production of active oxygen species particularly H₂O₂. The cells recover and start producing ATP immediately upon the cessation of H₂O₂ production. This indicates that the increased O₂ uptake is primarily incorporated into active O₂ species. A second consequence of these changes is probably a transient compromising of the respiratory status of the cells as indicated in expression of alcohol dehydrogenase. Elicitor-induced bean ADH was purified to homogeneity and the M_r 40 000 polypeptide was subjected to amino acid sequencing. 15% of the whole protein was sequenced from three peptides and was found to have nearly 100% sequence similarity to the amino acid sequence for pea ADH1 (PSADH1). The cDNA coding for the pea enzyme was used to demonstrate the transient induction of ADH mRNA in elicitor-treated bean cells. Enzyme activity levels also increased transiently subsequently. Increased oxygen uptake has previously been thought to be associated with provision of energy for the changes in biosynthesis that occur rapidly after perception of the stress signal. However the present work shows that this rapid increase in oxygen uptake as a consequence of elicitor action is not wholly associated with respiration.