941 research outputs found
Saint Ambroise et Philon
No full textNikiprowetzky Valentin. Saint Ambroise et Philon. In: Revue des Études Grecques, tome 94, fascicule 445-446, Janvier-juin 1981. pp. 193-199
Impact of long-term heavy metals exposure on cold acclimation in Salix viminalis roots
No full textA few years ago, it was observed that Salix viminalis grown in a soil polluted by a mixture of heavy metals were more winter-tolerant than plants grown in unpolluted soil. Salix aboveground organs being extremely frost-hardy, it was hypothesized that the difference in winter-tolerance was the consequence of an increased frost-tolerance at the root level. While this observation is intriguing, it is known that plant response to a combination of stress is unique and cannot be deduced a priori from the response to each of the stresses applied individually.
The aim of this thesis was to investigate this metal-induced frost-tolerance to identify markers of frost-tolerance in the roots of woody perennials. The amount of publicly available molecular data on S. viminalis being scarce at the beginning of the thesis, the first objective was to identify reference genes stably expressed in the root of S. viminalis. Then, these genes were used to select the plants that were studied from a transcriptome and proteome point of view. Since regulation of the cellular redox homeostasis is an important component in plant stress responses and a potential candidate for the observed increase of root frost-hardiness, a particular emphasis was put on it.
Contrary to our initial hypothesis, the simultaneous exposure to cold and metals did not seem to induce the antioxidative machinery. These results were confirmed by an analysis of different antioxidant enzymes and metabolites. However, proteins and transcripts related to the synthesis of lignans and sugars (especially raffinose) and proteins involved in oxidative damage repair mechanisms were found to be significantly more abundant in roots exposed to cold and metals compared to roots only exposed to one stress.
Since these observations were made on plants grown under controlled conditions, a follow up study was done by growing S. viminalis cuttings outside during a full growth season and analysing their roots at several time points. The simultaneous exposure to cold and metals did not increase the root phenolic content or the antioxidative capacity. In addition, the simultaneous exposure to metals did not impede sucrose accumulation, a known metabolic response to cold, in the cold-acclimated roots.
During the work presented here it was also observed that while at the individual gene level exposure to multiple stresses gave results that cannot be predicted from studies using single stress exposure, this is much less the case at the gene-ontology level. While needing confirmational studies with different stress combinations, such approach has the potential to accelerate molecular studies on the effects of multiple stress exposure.
Based on the different experimental setups a small number of genes was identified that show a synergetic effect in plants exposed to both stresses. These are potential candidates for breeding efforts to produce plants with an increased resistance to cold at the root level. Further study is however needed to confirm this
Impact of long-term heavy metals exposure on cold acclimation in Salix viminalis roots
No full textA few years ago, it was observed that Salix viminalis grown in a soil polluted by a mixture of heavy metals were more winter-tolerant than plants grown in unpolluted soil. Salix aboveground organs being extremely frost-hardy, it was hypothesized that the difference in winter-tolerance was the consequence of an increased frost-tolerance at the root level. While this observation is intriguing, it is known that plant response to a combination of stress is unique and cannot be deduced a priori from the response to each of the stresses applied individually.
The aim of this thesis was to investigate this metal-induced frost-tolerance to identify markers of frost-tolerance in the roots of woody perennials. The amount of publicly available molecular data on S. viminalis being scarce at the beginning of the thesis, the first objective was to identify reference genes stably expressed in the root of S. viminalis. Then, these genes were used to select the plants that were studied from a transcriptome and proteome point of view. Since regulation of the cellular redox homeostasis is an important component in plant stress responses and a potential candidate for the observed increase of root frost-hardiness, a particular emphasis was put on it.
Contrary to our initial hypothesis, the simultaneous exposure to cold and metals did not seem to induce the antioxidative machinery. These results were confirmed by an analysis of different antioxidant enzymes and metabolites. However, proteins and transcripts related to the synthesis of lignans and sugars (especially raffinose) and proteins involved in oxidative damage repair mechanisms were found to be significantly more abundant in roots exposed to cold and metals compared to roots only exposed to one stress.
Since these observations were made on plants grown under controlled conditions, a follow up study was done by growing S. viminalis cuttings outside during a full growth season and analysing their roots at several time points. The simultaneous exposure to cold and metals did not increase the root phenolic content or the antioxidative capacity. In addition, the simultaneous exposure to metals did not impede sucrose accumulation, a known metabolic response to cold, in the cold-acclimated roots.
During the work presented here it was also observed that while at the individual gene level exposure to multiple stresses gave results that cannot be predicted from studies using single stress exposure, this is much less the case at the gene-ontology level. While needing confirmational studies with different stress combinations, such approach has the potential to accelerate molecular studies on the effects of multiple stress exposure.
Based on the different experimental setups a small number of genes was identified that show a synergetic effect in plants exposed to both stresses. These are potential candidates for breeding efforts to produce plants with an increased resistance to cold at the root level. Further study is however needed to confirm this
Can phenotypic selection on floral traits explain the presence of enigmatic intermediate individuals in sympatric populations of Platanthera bifolia and P. chlorantha (Orchidaceae)?
No full textPollinators represent one of the main agents of selection on floral traits. Here, we estimated phenotypic selection on floral morphology and phenology in a sympatric population of two orchid species, Platanthera bifolia and P. chlorantha, including enigmatic individuals with intermediate column morphology (as reflected by the distance between viscidia and caudicle length, two traits involved in assortative mating and reproductive isolation among Platanthera species), but genetically indistinguishable from P. bifolia. Our aim was to clarify whether the occurrence of intermediate phenotypes could be explained by the presence of selective pressures exerted by pollinators. Simple linear and quadratic regressions together with univariate and multivariate analyses were used to evaluate the strength of directional, disruptive and stabilizing selection. We found that selection on phenotypic traits varied between groups and sex functions. Contrary to our hypothesis, selection on the viscidia distance and caudicle length appeared to be consistent in the two P. bifolia groups. Interestingly, the viscidia distance was under significant stabilizing selection through female reproductive success in intermediate individuals. Based on these results, we conclude that, despite a significant selective pressure on some phenotypic traits, the presence of individuals with intermediate phenotype is not due to selection. Stabilizing selection on distance between viscidia in intermediate individuals may suggest that assortative mating play a role in the maintenance of this phenotypic polymorphism
Alf Nilsen-Børsskog — The Author Chosen by the Language
No full textThis article discusses Alf Nilsen-Børsskog’s four-volume series of novels Elämän jatko [Continuation of life, 2004–2015], seen as the first literary works treating the Kven culture from a native perspective. Nilsen-Børsskog’s novels are analysed as constituting a “counterstory”, a term coined in the postcolonial cultural research paradigm to refer to self-representation. The Kvens have been considered a national minority in Norway since 1999, and their language has been an official minority language since 2005. The present author scrutinizes how Nilsen-Børsskog’s work differs from previous literary descriptions of this minority, often marked by the frequent use of stereotypes of the Kven language and culture
LIBS and LA-SD-OES Analysis of Minor and Trace Elements in Steel Samples
No full textAuthor Valentin Ehrentraut, BScMasterarbeit Universität Linz 2022Arbeit nach Ablauf der Sperre auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
The Roots of Plant Frost Hardiness and Tolerance
No full textFrost stress severely affects agriculture and agroforestry worldwide. Although many studies about frost hardening and resistance have been published, most of them focused on the aboveground organs and only a minority specifically targets the roots. However, roots and aboveground tissues have different physiologies and stress response mechanisms. Climate models predict an increase in the magnitude and frequency of late-frost events, which, together with an observed loss of soil insulation, will greatly decrease plant primary production due to damage at the root level. Molecular and metabolic responses inducing root cold hardiness are complex. They involve a variety of processes related to modifications in cell wall composition, maintenance of the cellular homeostasis and the synthesis of primary and secondary metabolites. After a summary of the current climatic models, this review details the specificity of freezing stress at the root level and explores the strategies roots developed to cope with freezing stress. We then describe the level to which roots can be frost hardy, depending on their age, size category and species. After that, we compare the environmental signals inducing cold acclimation and frost hardening in the roots and aboveground organs. Subsequently, we discuss how roots sense cold at a cellular level and briefly describe the following signal transduction pathway, which leads to molecular and metabolic responses associated with frost hardening. Finally, the current options available to increase root frost tolerance are explored and promising lines of future research are discussed.Luxembourg National Research Fund (FNR) [project X-press AFR PhD/17/SR 11634190
Ambroise Kom : ce que s’indigner veut dire. Notes provisoires sur une figure de la résistance
No full textThe purpose of this contribution is to gauge the originality, consistency and coherence of the approaches that underpin the specificity of Ambroise Kom’s intellectual trajectory. Thus, it questions the theoretical basis of this posture, by examining the articulation of his theoretical positions and his praxis. Drawing, among other benchmarks, on the experience of the Université des Montagnes in Cameroon, the study establishes that beyond the prevailing taxonomies, the academic escapes the fixity that would otherwise sever his deployment from a decisive part of his approach
Johann Siegmund Valentin Popowitsch (Janez Žiga Valentin Popovič), Vocabula Austriaca et Stiriaca 1-2 (Frankfurt am Main 2004)
No full textThe Austrian dictionary composed by the Slovenian scho-lar Janez Žiga Valentin Popovič (1705-1774) in the third quarter of the 18th century was only published in 2004, and edited by Richard Reutner, who wrote an extensive introduction to it. The dictionary comprises many language-geographical data for the German language, excellent explanations and many comparisons with much information provided regarding Popovic's mother tongue. The author broad horizon is admirable, especially with regard to the German language area and the linguistic literature of that time.Avstrijski slovar, ki ga je v tretji četrtini 18. stoletja sestavil slovenski učenjak Janez Žiga Valentin Popovič (1705-1774), je izšel šele leta 2004 v uredništvu Richarda Reutnerja, kije k njemu napisal obsežen uvod. Slovar vsebuje mnogo jezikovnogeografskih podatkov za nemščino, odlične razlage in marsikaj primerjalnega, veliko pa se najde tudi v zvezi s Popovičevo materinščino. Občudovanja vredna je avtorjeva razgledanost predvsem po nemškem jezikoslovnem prostoru in po takratni jezikoslovni literaturi
Valentin N. Volóchinov: um filósofo da ciência da linguagem
No full textThis text address the work of Russian scholar Valentin N. Vološinov, author of the book Marxism and the Philosophy of Language. The objective is to demonstrate a set of characteristics that place Vološinov as a participant in the critique of science movement, which had its epicenter in Germany, between the years 1840 and 1900. To this end, in addition to a general reflection, which recovers the meaning of the term “criticism” most present in the academic environment of the time, this text considers two points of the much mentioned – and, apparently, somewhat misunderstood – opposition of the Russian thinker to the linguistics of Ferdinand de Saussure, as this linguistics is presented in the Course in General Linguistics. Finally, by way of provocation, this text outlines a few words about the proximity between the epistemological works of Valentin N. Vološinov and Wilhelm Dilthey.Este texto aborda la obra del estudioso ruso Valentin N. Voloshinov, autor de la obra Marxismo y filosofía del lenguaje. El objetivo es demostrar un conjunto de características que sitúan a Voloshinov como participante del movimiento de crítica científica, que tuvo su epicentro en Alemania, entre los años 1840 y 1900. Para ello, además de una reflexión general, que recupera el significado del término “crítica” más presente en el ambiente académico de la época, se consideran dos puntos de la tan mencionada –y, aparentemente, algo incomprendida– oposición del pensador ruso a la lingüística de Ferdinand de Saussure, tal como se presenta esta última en el curso de lingüística general. Al final, a modo de provocación, se esbozan algunas palabras sobre la proximidad entre las obras epistemológicas de Valentin N. Voloshinov y Wilhelm Dilthey.O presente texto aborda o trabalho do estudioso russo Valentin N. Volóchinov, autor da obra Marxismo e filosofia da linguagem. O objetivo é demonstrar um conjunto de características que situam Volóchinov como um partícipe do movimento de crítica das ciências, o qual teve seu epicentro na Alemanha, entre os anos 1840 e 1900. Para isso, além de uma reflexão geral, que recupera a acepção do termo “crítica” mais presente no ambiente acadêmico da época, são considerados dois pontos da muito mencionada – e, ao que tudo indica, um tanto mal compreendido – oposição do pensador russo à linguística de Ferdinand de Saussure, tal como essa última é apresentada no Curso de linguística geral. Ao fim, a título de provocação, são esboçadas algumas palavras a respeito da proximidade entre os trabalhos epistemológicos de Valentin N. Volóchinov e Wilhelm Dilthey
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