Nitrogen deficiency impacts on leaf cell and tissue structure with consequences for senescence associated processes in Brassica napus

International audienceImprovement of nutrient use efficiency is a major goal for several crop plants, especially Brassica napus. Indeed, the low nitrogen use efficiency (NUE) in this crop results in negative economic and ecological consequences. The low NUE of oilseed rape is mainly due to low remobilization of nitrogen from vegetative parts to growing organs. Remobilization of leaf nitrogen takes place during senescence, a process known to strongly modify cell and tissue structure. This study focused on the impact of moderate N depletion, expected to induce 30% reduction of seed yield, on these structural modifications. Two genotypes (Aviso and Express) were studied, with different tolerance of nitrogen depletion, evaluated through seed yield and dry mass production. Structural modifications of leaf cells and tissues were investigated through NMR relaxometry and light microscopy. Lower tolerance of N depletion was associated with higher impact on senescence associated structural modification pattern. The link between leaf structure modifications and nutrient remobilization is discussed. It is proposed that leaf structure monitoring during senescence through NMR device could be developed to select genotypes with high NUE

Diversity of Leptospira spp. in bats and rodents from Papua New Guinea

Leptospirosis is the most common bacterial zoonosis globally. The pathogen, Leptospira spp., is primarily associated with rodent reservoirs. However, a wide range of other species has been implicated as reservoirs or dead-end hosts. We conducted a survey for Leptospira spp. in bats and rodents from Papua New Guinea. Kidney samples were collected from 97 pteropodid bats (five species), 37 insectivorous bats from four different families (six species) and 188 rodents (two species). Leptospires were detected in a high proportion of pteropodid bats, including Nyctimene cf. albiventer (35%), Macroglossus minimus (34%) and Rousettus amplexicaudatus (36%). Partial sequencing of the secY gene from rodent and bat leptospires showed host species clustering, with Leptospira interrogans and L. weilii detected in rodents and L. kirschneri and a potential novel species of Leptospira detected in bats. Further research is needed in Papua New Guinea and other locales in the Pacific region to gain a better understanding of the circulation dynamics of leptospires in reservoir species and the risks to public and veterinary health

Etude de faisabilité de mesure RMN sur des semences

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEEEn conclusion : 1. le signal RMN est sensible à la différence de teneur en eau des échantillons étudiés et à la composition de l'extrait sec de la graine ou de ses fractions. 2. Il est possible : a. d'extraire un signal spécifique des fractions protéique et amylacée. b. d'extraire un signal correspondant à la phase aqueuse. On note une variation très importante des paramètres de relaxation attribués à l'eau en fonction de la teneur en eau ou de l'Aw. Par ailleurs, cette variable présente une sensibilité notable à la composition de la graine puisque le temps de relaxation est différent malgré une teneur en eau ou une Aw identique. Par contre, l'évolution des amplitudes des signaux semble cohérente avec la teneur en eau. Ainsi l'amplitude serait un indicateur de la teneur en eau tandis que le temps de relaxation serait un indicateur lié au ratio entre la quantité d'eau exprimée en fonction de la teneur en protéine, ou autres composées hydrophiles. c. d'extraire un signal spécifique de la matière grasse. Ces premières mesures confirment la faisabilité d'un dosage de la quantité de lipide. Méthode qui est déjà proposée par certains constructeurs

1. NMR approach to evaluate impact of nitrogen supply on the senescence process of Brassica napus leaves under field conditions

International audienceDuring leaf senescence, improved remobilization of nutrients from old leaves to growing organs may represent an adaptive response of Brassica napus plants to the decrease in nitrogen (N) input. Therefore characterization of the natural genotypic variability of leaf remobilization efficiency should allow providing relevant information for crop improvement. It has been recently demonstrated that NMR transverse relaxation times can be used to monitor leaf senescence process through senescence associated cell and tissue structural modifications [1-2]. The impact of N deficiency on these changes has also been demonstrated on Brassica Napus plants grown under controlled conditions [3]. The aim of the present work was to investigate by NMR a plant response to nitrogen fertilization under field conditions. Two genotypes of winter oil seed rape (Brassica napus, cv Aviso and Express) with different tolerance to N deficiency were assessed. A mobile NMR lab [4] was brought into the field allowing NMR measurements without plant uprooting. Transverse relaxation times were measured on leaf discs cut from the leaves of each leaf rank of the plant studied. A CPMG sequence with a 90°-180° pulse spacing of 0.2ms and 64 averages were used. The genotypic response to N depletion was evaluated through dry mass production and seed yield. The results obtained in two different genotypes showed that despite a great variability of the macro and micro environmental factors, the NMR relaxation provided robust indicators of the structural changes that occurred during leaf development. The pattern of these changes differed between genotypes in lower N regime due to their different responses to the decrease in N input. This study presents an important step toward the use of NMR relaxometry for field phenotyping of nitrogen fertilization response

Détermination des lipides dans des déchets organiques par la méthode soxhlet : comparaison à la méthode par RMN

National audienceDepuis de nombreuses années, la production de déchets organiques est en augmentation constante en raison de pratiques d’élevage, d’industrialisation, de procédés de traitement et collecte des déchets. Pour répondre aux enjeux environnementaux de la gestion des déchets, des procédés biologiques de traitement et de valorisation sont mis en oeuvre, notamment la digestion anaérobie (méthanisation). Cependant, l’ajout de graisse peut entraîner, dans certains cas, des inhibitions dans le procédé de digestion [1]. La bibliographie décrit de nombreuses méthodes concernant la détermination des lipides. La plus connue et utilisée consiste, à l’aide d’un soxhlet, à extraire à chaud par solubilisation des composants à l’aide d’un solvant [2]. Une autre méthode de mesure des lipides totaux par résonance magnétique RMN a été étudiée sur des muscles de poisson séché et a donné une bonne corrélation [3]. Dans le domaine des déchets, la RMN a déjà été utilisée pour la caractérisation de la matière organique, notamment les acides humiques, et les transformations de cette matière lors du compostage [4], mais aucune référence ne semble disponible sur l’analyse des lipides. Au cours de cette étude, la méthode RMN a été comparée à la méthode soxhlet sur des déchets organiques susceptibles d’être utilisés en méthanisation. Ainsi, 48 déchets d’origine différente ont été analysés avec les 2 méthodes Trois répétitions ont été effectuées pour chacun des substrats. La corrélation entre les méthodes soxhlet et RMN a été de 0.90 et la pente de régression de 1.02. Une meilleure précision de la méthode RMN a été calculée avec un coefficient de variation de 5% alors que pour la méthode sohxlet il est de 14%. En revanche, la méthode RMN a donné globalement des valeurs inférieures à la méthode de référence soxhlet : la sous-estimation peut être liée à l’extraction non sélective au soxhlet, à une température de chauffage insuffisante liée à l’état amorphe des lipides ou au degré de saturation des matières grasses dans les différents produits pour la RMN. L’état d’hydrolyse des graisses lié à leur stockage et le degré de saturation des acides gras à longues chaînes pourrait influencer la mesure des lipides par RMN. La méthode RMN semble adaptée à l’analyse des graisses avec une meilleure répétition et présente l’avantage de n’utiliser aucun solvant, d’être rapide et non destructrice malgré une sous-évaluation par le protocole RMN actuel. Enfin, cette étude a également permis d’établir des données lipidiques sur des déchets organiques et suppléer la méthode d’analyse soxhlet de référence

Procédé d'identification et de quantification des proportions relatives des différentes fractions cristallisées présentes dans un coulis d'hydrate et son utilisation pour les fluides frigoporteurs

Procédé d'identification et de quantification des proportions relatives des différentes fractions cristallisées et liquide présentes dans un coulis d'hydrate, défini comme un solide en suspension dans un fluide porteur, caractérisé en ce qu'il est effectué au moyen d'un spectromètre de résonance magnétique nucléaire à bas champ et d'une sonde de radiofréquence permettant de détecter et de quantifier les protons par mesure directe sur ledit coulis d'hydrate. Le coulis d'hydrate est par exemple composé d'un clathrate hydrate d'alkyl-onium. Application à l'identification, la caractérisation et la quantification des différents polymorphes d'hydrates formés dans des fluides frigoporteurs diphasiques, en mode statique ou dynamique

Caractérisation par RMN à bas champ du taux de solide et distinction de cristaux A et B d'hydrates de TBAB

International audienceSemiclatrate hydrate crystals of tetra-n-butyl ammonium bromide (TBAB) form at atmospheric pressure and a positive temperature. In suspension in water, they can be used as a heat transport medium or for gas separation. In terms of thermal energy storage and secondary refrigeration applications, TBAB hydrate slurries may be characterized by their flow properties under specific thermophysical conditions. The study presented here investigated one of these important properties, i.e. the crystal content, also called the solid fraction, that is usually estimated using the TBAB:H2O phase diagram. Our investigations revealed that Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry was remarkably sensitive to the solid content of TBAB:H2O hydrate slurries. Non-invasive and non-destructive measurements performed in real time demonstrated the power of NMR relaxometry to identify and quantify TBAB hydrates. Most importantly, NMR both measured and quantified type A and B hydrates, which no other technique can achieve without destroying the crystals or can only perform theoretically on the basis of a phase diagram, and thus without considering the possible conversion of type A to type B hydrates

Determination of lipid fraction from organic wastes using Nuclear Magnetic Resonance (NMR): Comparison to the soxhlet method

International audienceDuring this study, nuclear magnetic resonance (NMR) was compared to the soxhlet extraction for determination of the lipid content of organic waste usually used in anaerobic digestion. Thus, 48 different wastes were analyzed using both methods and three replicates were performed for each. The correlation between Soxhlet methods and NMR was 0.90 and the regression slope was equal to 1.02. A better precision was obtained for NMR method with a coefficient of variation of 5%, while for the Soxhlet method, this coefficient is 14%. In contrast, the NMR method gave overall values below the reference method soxhlet. This difference can be explained by the advanced state of hydrolysis of fats where a large amount of volatile fatty acids, saturated molecules small chains linked would be present, and the degree of saturation of fatty acids long chains. NMR method seems suited to the analysis of lipids with better repetition and has the advantage of not using any solvent, be fast and non-destructive. However, the determination of some lipid matrices seems undervalued using the conditions established by the NMR protocol. Finally, this study also established data on lipid content of organic waste

RMN mobile pour le phénotypage des feuilles

International audienceBackground: Low field NMR has been used to investigate water status in various plant tissues. In plants grown in controlled conditions, the method was shown to be able to monitor leaf development as it could detect slight variations in senescence associated with structural modifications in leaf tissues. The aim of the resent study was to demonstrate the potential of NMR to provide robust indicators of the leaf development stage in plants grown in the field, where leaves may develop less evenly due to environmental fluctuations. The study was largely motivated by the need to extend phenotyping investigations from laboratory experiments to plants in their natural environment.Methods: The mobile NMR laboratory was developed, enabling characterization of oilseed rape leaves throughout the canopy without uprooting the plant. The measurements made on the leaves of plants grown and analyzed in the field were compared to the measurements on plants grown in controlled conditions and analyzed in the laboratory.Results: The approach demonstrated the potential of the method to assess the physiological status of leaves of plants in their natural environment. Comparing changes in the patterns of NMR signal evolution in plants grown under well-controlled laboratory conditions and in plants grown in the field shows that NMR is an appropriate method to detect structural modifications in leaf tissues during senescence progress despite plant heterogeneity in natural conditions. Moreover, the specific effects of the environmental factors on the structural modifications were revealed.Conclusion: The present study is an important step toward the selection of genotypes with high tolerance to water or nitrogen depletion that will be enabled by further field applications of the method