La vulnérabilité du sapin pectiné (Abies alba Mill.) à la sécheresse en milieu méditerranéen selon les propriétés hydriques du sol

De nombreux cas de mortalité de Sapin pectiné (Abies alba Mill.) sont constatés en limite sud de son aire de répartition en Provence et semblent être liés aux sécheresses successives de la dernière décennie et à la répartition des propriétés hydriques du sol. L enjeu est alors de mieux évaluer l impact du stress hydrique sur le fonctionnement écophysiologique de cette espèce et de pouvoir caractériser et cartographier les zones les plus vulnérables à la sécheresse. Sur le Mont Ventoux, une expérimentation a été mise en place pour suivre pendant 3ans différents paramètres écophysiologiques impliqués dans le comportement hydrique du Sapin pectiné sur des placettes pour lesquelles les propriétés du sol étaient caractérisées. Sur cette montagne de type karstique, les profondeurs de sols sont très variables et, à l'échelle stationnelle, les taux de mortalité et les intensités de stress hydrique étaient plus élevés sur les sols ayant une réserve hydrique plus importante. De plus, un arrière-effet de la sécheresse de 2009 a été observé réduisant durablement la transpiration de l'année suivante. Une approche par modélisation mécaniste a alors été adoptée en intégrant de nouveaux formalismes sur la dynamique racinaire permettant de prendre en compte cet arrière-effet. Elle a été évaluée sur les différents paramètres impliqués dans le cycle de l'eau et du carbone des arbres et le modèle a été validé sur les dynamiques de transpiration et d accroissement en largeur de cernes des troncs. Des indices basés sur la mesure de température de surface ont été utilisés pour évaluer la possibilité de détecter le stress hydrique en forêt. Il existe une variabilité résiduelle liée aux facteurs climatiques et à la dimension réduite de la surface de mesure dans la relation entre transpiration et température de surface à l'échelle de l'arbre. A l échelle du versant, la température de surface a permis d'identifier la répartition spatiale de la durée et de l'intensité du stress hydrique en accord avec la typologie de sol réalisées. La télédétection dans l'infrarouge thermique pourrait ainsi être un outil intéressant pour la gestion forestière.Many reports of deaths of silver fir (Abies alba Mill.) are mentioned at the southern limit of its limit of distribution in Provence and appear to be related to the successive droughts of the last decade and to the distribution of soil water properties. The aim of the study is then to better assess the impact of water stress on ecophysiological functioning of this species and to characterize and map the areas more vulnerable to drought. On the Mont Ventoux, an experiment was set up to monitor for 3 years ecophysiological parameters involved in the water behaviour of silver fir on plots where soil properties were characterized. On this type of karstic mountain, soils depth is highly variable and, at forest stand scale, mortality rates and intensities of water stress were higher on soils with greater water reserve. In addition, a post-effect of the drought of 2009 was observed by reducing transpiration of the following year. A mechanistic modelling approach was then adopted by integrating new formalisms of root dynamics to take into account this post-effect. It was evaluated on various parameters involved in the water and carbon cycles of trees and the model was validated on the dynamics of transpiration and on annual rings width increment of tree trunks.Indices based on measured surface temperature were used to assess the possibility of detecting water stress in forests. At tree scale, there is a residual variability due to climatic factors and to the small size of the measurement surface in the relationship between transpiration and surface temperature. At the mountainside scale, surface temperature indices allowed identifying the spatial distribution of the duration and intensity of water stress according to the typology of soil done. Remote sensing in the thermal infrared could then be a useful tool for forest management.AVIGNON-Bib. numérique (840079901) / SudocSudocFranceF

Pourquoi les nullipares ne choisissent pas plus le DIU ? (enquête auprès de femmes)

Le nombre d IVG en France reste stable depuis quelques années malgré une large diffusion de la contraception. 2/3 des IVG sont dues à un échec contraceptif, notamment de la pilule, qui est le moyen le plus répandu chez les femmes jeunes. Le stérilet au cuivre a depuis 2004 l AMM chez les nullipares. Il est cependant très peu utilisé dans cette population (1.3% en 2010) et reste l apanage des femmes plus âgées multipares. Nous avons voulu savoir quelles sont les opinions et connaissances des nullipares sur ce moyen contraceptif. Nous leur avons pour cela distribué des questionnaires anonymes dans trois centres de l agglomération grenobloise. 190 questionnaires ont été analysés. Seulement 48% des femmes avaient reçu préalablement une information de la part d un professionnel de santé sur le stérilet. 80% des femmes nullipares ne choisiraient pas cette méthode à court terme. Les principales réticences évoquées sont la peur d avoir un corps étranger dans son corps et la peur de la pose. Les deux principaux avantages sont la simplicité d utilisation et l absence d hormone. L âge, le niveau d étude, le lieu d habitation et le statut conjugal n influent pas le choix ou non de cette méthode. Après évaluation par quizz, 73% des femmes ont au moins quatre bonnes réponses sur sept et ont donc des connaissances plus que satisfaisantes. Ces données montrent que les nullipares sont plutôt réticentes envers ce moyen contraceptif. Pourtant leurs craintes sont fondées sur beaucoup d aprioris et pourraient facilement être levées par une information appropriée de la part des professionnels de santé.The number of abortions in France remains stable in recent years despite a large distribution of contraception. 2/3 of abortions are due to contraceptive failures, including the pill failure, which is the most prevalent method among young women. Since 2004, the copper IUD is authorized for nulliparous. However, it is rarely used in this population (1.3% in 2010) and remains the prerogative of older women, and multiparous. We wanted to know the opinions and knowledge of nulliparous about copper IUD. For this, we distributed anonymous questionnaires from them in three centers in Grenoble city. 190 questionnaires were analyzed. Only 48% of women previously received information from the health practitioners on the IUD. 80% of nulliparous would not choose this contraceptive way at short-term. The main reluctances are the fear of having a foreign body inside their womb and the fear of pain with device insertion. The main reasons of interest are the simplicity of use and the non-requirement of hormones. Age, study level, place of residence and marital status do not influence the choice of this method. After a quiz evaluation, 73% of women correctly answered at least four questions over seven and therefore have sufficient knowledge. These data show that nulliparous women are quiet reluctant to use the IUD. However, their fears are based on many misconceptions that could easily be removed by appropriate information from health practitioners.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

Characterisation of grapevine canopy leaf area and inter-row management using Sentinel-2 time series

Accurate data on crop canopy are among the prerequisites for hydrological modelling, environmental assessment, and irrigation management. In this regard, our study concentrated on an in-depth analysis of optical satellite data of Sentinel-2 (S2) time series of the leaf area index (LAI) to characterise canopy development and inter-row management of grapevine fields. Field visits were conducted in the Ouveze-Ventoux area, South Eastern France, for two years (2021 and 2022) to monitor phenology, canopy development, and inter-row management of eleven selected grapevine fields. Regarding the S2-LAI data, the annual dynamic of a typical grapevine canopy leaf area was similar to a double logistic curve. Therefore, an analytic model was adopted to represent the grapevine canopy contribution to the S2-LAI. Part of the parameters of the analytic model were calibrated from the actual grapevine canopy dynamics timing observation from the field visits, while the others were inferred at the field level from the S2-LAI time series. The background signal was generated by directly subtracting the simulated canopy from the S2 LAI time series. Rainfall data were examined to see the possible explanations behind variations in the inter-row grass development. From the background signals, we could group the inter-row management into three classes: grassed, partially grassed, and tilled, which corroborated our findings on the field. To consider the possibility of avoiding field visits, the model was recalibrated on a grapevine field with a clear canopy signal and applied to two fields with different inter-row management. The result showed slight differences among the inter-row signals, which did not prevent the identification of inter-row management, thus indicating that field visits might not be mandatory

New methodology for the characterization of endoglucanase activity and its application on the Trichoderma longibrachiatum cellulolytic complex

The cellulolytic complex of Trichoderma longibrachiatum was separated in nine fractions using FPLC. The avicelase, cellobiase, carboxymethylcellulase, and endoglucanase activities of these fractions were characterized. The endoglucanase activity was measured by a method that allows the determination of the variation in the degree of polymerization of the insoluble celluloses. This method, which is based on the measurement of the reducing power of the insoluble fibers, is proposed as a tool for the identification and characterization of the endoglucanases. Using this technique and H3PO4-swollen cotton as substrate, the kinetic parameters of two proteins that showed high specific endoglucanase activity (pI = 5.25; Mr = 55 kDa; and pI = 4.70; Mr = 70 kDa) were determined. The measurement of the degree of polymerization variation during digestion of Sigmacell gives evidence that the endoglucanase activity is located at the beginning of the reaction.JNICT -Junta Nacional de Investigação Científica e Tecnológicainfo:eu-repo/semantics/publishedVersio

Polysaccharide structures and interactions in a lithium chloride/urea/water solvent

The molten salt hydrate, lithium chloride (LiCl)/urea/water has previously been shown to swell cellulose, but there has so far been no work done to explore its effect on other polysaccharides. In this paper we have investigated the solvent effects of LiCl/urea/water on four natural polysaccharides. Fenugreek gum and xyloglucan, which are both highly branched, were found to increase in viscosity in LiCl/urea/water relative to water, possibly due to the breakage of all intra-molecular associations whereas the viscosity of konjac glucomannan which is predominantly unbranched did not change. Locust bean gum (LBG) had a lower viscosity in LiCl/urea/water compared to water due to the disruption of aggregates. Confocal microscopy showed that fenugreek gum and LBG are able to bind to cellulose in water, however, the conformational change of fenugreek gum in these solvent conditions inhibited it from binding to cellulose in LiCl/urea/water whereas conformational change allowed xyloglucan to bind to cellulose in LiCl/urea/water whilst it was unable to bind in water. Konjac glucomannan did not bind to cellulose in either solvent system. These results provide new insights into the impact of polysaccharide fine structure on conformational change in different solvent environments