Diversity and P-solubilizing ability of mycorrhizosphere bacteria associated with Pinus pinaster in the Landes forest ecosystem

Ectomycorrhizal fungi (ECM) and their associated mycorrhizosphere bacteria (MB) play a major role in phosphorous (P) nutrition of maritime pine, particularly in the Landes forest ecosystem considering the low bioavailability of P in its sandy-acidic soils. In order to characterize the MB associated to ECM, three collection campaigns of ECM root tips were performed from autumn 2005 to autumn 2006 throughout three forest stations. Five MB and nine ECM genera were identified overall through sequencing of 16S rDNA and mitochondrial large subunit rDNA fragment respectively. Dramatic seasonal changes were observed in the different MB-ECM associations especially in Burkholderia-Lactarius and Bacillus-Russula that were the most abundant ones. P-solubilizing ability of MB was shown to be taxon-dependent with a large majority of P-solubilizing isolates among Burkholderia, Pseudomonas and Paenibacillus contrary to Bacillus. Relationships between functional diversity of the MB-ECM associations and bioavailability of soil P remain to be investigated. (Résumé d'auteur)

Traitement laparoscopique des cancers du colon (étude prospective randomisée et multicentrique laparotomie versus laparoscopie)

MONTPELLIER-BU Médecine (341722104) / SudocMONTPELLIER-BU Médecine UPM (341722108) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Complications nerveuses sexuelles après colectomie gauche par vidéolaparoscopie pour lésions bénignes

MONTPELLIER-BU Médecine (341722104) / SudocMONTPELLIER-BU Médecine UPM (341722108) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Voltammetric study of humic and fulvic substances. Part I: Study of the factors influencing the measurement of their complexing properties with lead

A detailed, qualitative, investigation of the behaviour of lead complexes with fulvic substances has been carried out using several polarographic techniques, e.g d.c. polarography, a.c. polarography, normal and differential pulse polarography and cyclic voltammetry. The mercury drop electrode was used for this study. It is shown that under the conditions used (pH∼6) the charge transfer process is reversible, the complexes are labile and the adsorption of fulvic acids and fulvic complexes occurs on the electrode. The implications of these results, with regard to the use of the various amperometric titrations for the measurement of the complexing capacity of natural waters, are discussed

Measurement of complexation properties of humic and fulvic acids in natural waters with lead and copper ion-selective electrodes

The use of ion-selective electrodes for the measurement of the complexation properties of humic and fulvic acids is described. Values for mean molecular weight of the ligand, the stability constants of the complexes, number of ligands fixed per metal ion, and the dependency of the stability of the complexes on pH, may be obtained. The accuracy of the results is checked by comparing these results with those obtained by other methods and with known ligands. A comparison between this method and other existing methods for studying humic complexes is also made.</p

Study of the complex formation of copper(II) by humic and fulvic substances

A study of the complexation of copper(II) by fulvic substances, based on ion-selective electrode measurements, is reported. The influences of the copper concentration (10-6 –1O-4 M), fulvic acid concentration (2–100 mg 1-1), pH (3–8) and calcium concentration (10-4–5 × 1O-3 M) are given particular attention. The effects of statistical errors on the measurement of the values of the complex-formation parameters are considered. These parameters are measured for various surface-water samples, aqueous soil extracts, peat water and solutions of organic matter formed by in vitro decomposition of leaves. In general, these parameters vary little with actual source for a particular type of water.</p

Relations entre environnement biophysique et réponse agronomique de symbiotes légumineuses-rhizobia : vers une analyse multi-locale

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