Assessing hydroaeroponic culture for the tripartite symbiosis of mungbean (Vigna radiata L.) with arbuscular mycorrhizal fungi and rhizobia

Mungbean (Vigna radiata L.) has the potential to establish symbiosis with rhizobia that fix atmospheric dinitrogen (N2), and arbuscular mycorrhizal fungi (AMF) that improve the uptake of low mobile soil nutrients such as phosphorus. Both rhizobial and mycorrhizal symbioses can benefit plants synergistically. The tripartite symbiosis of mungbean with rhizobia and AMF was assessed in hydroaeroponic culture under sufficient versus deficient P supplies (250 versus 75 μmol P plant-1 week-1) by comparing the effects of three AMF species on the mycorrhizal root colonization, rhizobial nodulation, and plant growth. Although, Glomus intraradices colonized well the roots of mungbean in sand and hydroaeroponic cultures, Gigaspora rosea only established well under sand culture conditions, and Acaulospora mellea weakly colonized roots under both culture conditions. Though significant differences of mungbean growth were found with different AMF species in sand, only few differences were observed in hydroaeroponic cultures. It is argued that the later will probably be a valuable tool for scrutinizing the interactions among the three symbionts, as well as plant  physiology, and nutrient partitioning within the symbiotic system.Key words: Acaulospora mellea, arbuscular mycorrhizal, Bradyrhizobium, Gigaspora rosea, Glomus intraradices, mungbean, phosphorus, symbiotic nitrogen fixation

Effect of phosphorus limiting on phytase activity, proton efflux and oxygen consumption by nodulatedroots of common bean (Phaseolus vulgaris)

This work intended to measure the nodulated-roots oxygen consumption, proton efflux and phytase activity in 2 lines of common bean (Phaseolus vulgaris) (115, 147) at 2 levels of P supply. Rooted seedlings were inoculated with Rhizobium tropici CIAT 899 in hydroaeroponic cultivation under glasshouse. Phosphorus was supplied as KH2PO4 at 15 and 250 ìmol pl-1 week-1 (15P and 250P, respectively). Our results showed that plant growth nodulation and symbiotic nitrogen fixation were significantly affected by P limiting (15P) for the both lines, but this adverse effect was more pronounced in 147 than in 115. For the both lines, the phytase activity, higher in roots than in nodules, was significantly increased by P limiting, but 115 maintained higher values as compared to 147 line. Incotyledons, the phytase activity was higher in 115 than in 147. Phosphorus shortage increased the cumulated proton release only in 115, whereas it was lowered for 147. In this line, the proton release was linked to symbiotic nitrogen fixation. Under 15P, the proton efflux per unit of nodulated-root biomass was 25% greater for 115 than 147, suggesting that under P limitation, proton efflux may constitute an efficient way to increase P uptake in the tolerant line (115). 15P increased significantlynodulated-root O2 consumption per g nodule DW and nodule conductance, but to a higher extent in 147. As a whole, bean plants at P-deficient conditions increased the activity of phytases and proton efflux, thus maintaining the oxygen diffusion in nodules. This may represent an adaptive mechanism for N2- fixing legumes to respond to P deficiency, by increasing the utilisation and the uptake of phosphorus for symbiotic nitrogen fixation

Dynamique des compartiments du carbone et de l'azote dans le sol cultivé en niébé et sorgho dans le système zaï en zone Nord soudanienne du Burkina Faso

La gestion appropriée des sols cultivés peut permettre un stockage de carbone, en plus de l’avantage supplémentaire du maintien du niveau de fertilité qui en résulte. L’objectif de cette étude est d’appréhender l’influence réelle de pratiques culturales sous niébé ou sorgho dans le système zaï, sur l’évolution et  l’organisation des teneurs de carbone (C) et d’azote (N) du sol à l’échelle de la parcelle. Un dispositif factoriel en blocs de Fisher a été utilisé. Les traitements comprenant des apports de fumier seul ou associé au burkina phosphate avec exportation des résidus de cultures ont été testés. Le fractionnement  granulométrique de la matière organique du sol a été utilisé, séparant trois fractions. Les résultats révèlent que la répartition de C et N dans les fractions  granulométriques n’a pas été affectée par les espèces cultivées. Quelle que soit la culture, le carbone et l’azote se trouvent  essentiellement sous forme de  matière organique stable dans la fraction 0-20 μm, soit respectivement 64% et 73% pour C et N. L’apport du fumier seul ou combiné au phosphate, entraîne une  augmentation de la matière organique labile ; 38% de C et 31% de N sont stockés dans la fraction 50-2000 μm. La dynamique de la matière organique du sol à  l’échelle de la parcelle est plus influencée par les amendements que par les espèces cultivées.Mot clés : Matière organique, sols dégradés, légumineuse, céréale, fumier, burkina phosphate

High loading of nanostructured ceramics in polymer composite thick films by aerosol deposition

Low temperature fabrication of Al2O3-polyimide composite substrates was carried out by an aerosol deposition process using a mixture of Al2O3 and polyimide starting powders. The microstructures and dielectric properties of the composite thick films in relation to their Al2O3 contents were characterized by X-ray diffraction analysis. As a result, the crystallite size of α-Al2O3 calculated from Scherrer's formula was increased from 26 to 52 nm as the polyimide ratio in the starting powders increased from 4 to 12 vol.% due to the crushing of the Al2O3 powder being reduced by the shock-absorbing effect of the polyimide powder. The Al2O3-polyimide composite thick films showed a high loss tangent with a large frequency dependence when a mixed powder of 12 vol.% polyimide was used due to the nonuniform microstructure with a rough surface. The Al2O3-polyimide composite thick films showed uniform composite structures with a low loss tangent of less than 0.01 at 1 MHz and a high Al2O3 content of more than 75 vol.% when a mixed powder of 8 vol.% polyimide was used. Moreover, the Al2O3-polyimide composite thick films had extremely high Al2O3 contents of 95 vol.% and showed a dense microstructure close to that of the Al2O3 thick films when a mixed powder of 4 vol.% polyimide was used

Symbiotic Legume Nodules Employ Both Rhizobial Exo- and Endo-Hydrogenases to Recycle Hydrogen Produced by Nitrogen Fixation

BACKGROUND: In symbiotic legume nodules, endosymbiotic rhizobia (bacteroids) fix atmospheric N(2), an ATP-dependent catalytic process yielding stoichiometric ammonium and hydrogen gas (H(2)). While in most legume nodules this H(2) is quantitatively evolved, which loss drains metabolic energy, certain bacteroid strains employ uptake hydrogenase activity and thus evolve little or no H(2). Rather, endogenous H(2) is efficiently respired at the expense of O(2), driving oxidative phosphorylation, recouping ATP used for H(2) production, and increasing the efficiency of symbiotic nodule N(2) fixation. In many ensuing investigations since its discovery as a physiological process, bacteroid uptake hydrogenase activity has been presumed a single entity. METHODOLOGY/PRINCIPAL FINDINGS: Azorhizobium caulinodans, the nodule endosymbiont of Sesbania rostrata stems and roots, possesses both orthodox respiratory (exo-)hydrogenase and novel (endo-)hydrogenase activities. These two respiratory hydrogenases are structurally quite distinct and encoded by disparate, unlinked gene-sets. As shown here, in S. rostrata symbiotic nodules, haploid A. caulinodans bacteroids carrying single knockout alleles in either exo- or-endo-hydrogenase structural genes, like the wild-type parent, evolve no detectable H(2) and thus are fully competent for endogenous H(2) recycling. Whereas, nodules formed with A. caulinodans exo-, endo-hydrogenase double-mutants evolve endogenous H(2) quantitatively and thus suffer complete loss of H(2) recycling capability. More generally, from bioinformatic analyses, diazotrophic microaerophiles, including rhizobia, which respire H(2) may carry both exo- and endo-hydrogenase gene-sets. CONCLUSIONS/SIGNIFICANCE: In symbiotic S. rostrata nodules, A. caulinodans bacteroids can use either respiratory hydrogenase to recycle endogenous H(2) produced by N(2) fixation. Thus, H(2) recycling by symbiotic legume nodules may involve multiple respiratory hydrogenases

The CCP4 suite: integrative software for macromolecular crystallography

The Collaborative Computational Project No. 4 (CCP4) is a UK-led international collective with a mission to develop, test, distribute and promote software for macromolecular crystallography. The CCP4 suite is a multiplatform collection of programs brought together by familiar execution routines, a set of common libraries and graphical interfaces. The CCP4 suite has experienced several considerable changes since its last reference article, involving new infrastructure, original programs and graphical interfaces. This article, which is intended as a general literature citation for the use of the CCP4 software suite in structure determination, will guide the reader through such transformations, offering a general overview of the new features and outlining future developments. As such, it aims to highlight the individual programs that comprise the suite and to provide the latest references to them for perusal by crystallographers around the world

Fixation d'azote par le soja vietnamien (Glycine max) cv DH4 inoculé par Bradyrhizobium japonicum USDA 138 (G3)

Les quatre associations symbiotiques entre, d'une part, les sojas (Glycine max L) cv DH4 (soja vietnamien) et 171-16 et, d'autre part, les rhizobiums SMX11 (originaire de la vallée du Mékong) à croissance rapide et G3 (Bradyrhizobium japonicum USDA 138) à croissance lente sont cultivées sur milieu liquide à pH 6,3 dépourvu d'azote minéral. Les plantes dont les nodosités sont déjà en place et actives sont transférées à 30 j sur des milieux à pH 5,3 et 4,3. La réponse des 4 symbioses au pH du milieu est étudiée par comparaison, après 2 sem de la biomasse (quantité de matière sèche des plantes) et de la fixation de N2 (N organique total des plantes) des plantes transférées à celles des plantes maintenues à pH 6,3. Trois types de réponses à l'acidification du milieu s'observent sans relation apparente avec les réponses individuelles des plantes et des bactéries au pH du milieu lors des cultures en conditions asymbiotiques : pour les symbioses de SMX11, le transfert en milieu acide n'a pas d'effet sur la fixation de N2 quel que soit l'hôte, tandis que pour les symbioses de G3, le transfert à pH 4,3 est inhibiteur avec 171-16, et stimulateur avec DH4. Les sojas 171-16 et DH4, non inoculés, dépendants de NO3-, ont une croissance respectivement plus rapide et plus lente à pH 4,3 qu'à pH 6,3. Enfin la croissance des rhizobiums est maximale respectivement à pH 5,3 et 6,3 pour les souches G3 et SMXII. Les effets du pH du milieu ne sont donc en relation ni avec le génotype bactérien, ni avec le génotype de la plante pris isolément, mais dépendent vraisemblablement du contrôle génétique créé par les conditions de symbiose. G3 trouve ainsi, chez le soja DH4 et dans des conditions de milieu acide, les conditions d'environnement cellulaire les plus favorables à l'expression de sa capacité à fixer N 2. Il est conclu que la symbiose G3/DH4 non seulement tolère mais préfère le milieu acide en aquiculture. En conséquence, il apparaît souhaitable de tester au champ l'effet de l'inoculation du soja vietnamien DH4 avec la souche G3, en particulier dans le delta du Mékong où les sols sont très acides.Dinitrogen fixation by the vietnamese soybean (Glycine max) cv DH4 inoculated by Bradyrhizobium japonicum USDA 138 (G3) is enhanced upon transfer to acid medium. Four symbiotic associations obtained by inoculation of soybean (Glycine max L) cv DH4 (from Vietnam) and 171-16, with Rhizobium SMX11, a fast-growing strain from the Mekong valley and G3 (Bradyrhizobium japonicum USDA 138), a slow-growing strain, were grown on N-free solution at pH 6.3. Acid treatments were applied by transfer of 30-d-old plants with well-developed nodules onto solutions at pH 5.3 and 4.3. The effect of pH was studied after 2 wk by measuring biomass (plant dry weight) and N2 fixation (organic N per plant). Three different responses to acid pH were observed with no apparent connection with individual responses to acid pH of plants and rhizobia when grown asymbiotically: SMX11 symbiosis was resistant to acid pH whatever the host soybean, while G3/171-16 symbiosis was sensitive to acid pH, and G3/DH4 preferred pH 4.3. The non-inoculated soybeans 171-16 and DH4 cultured on NO3- grew respectively faster and more slowly at pH 4.3 than at pH 6.3. Maximum growth rate of the free rhizobia was at pH 5.3 and 6.3 for G3 and SMX11 respectively. Thus, the effects of growth pH have no relationship with the rhizobia or the plant genotype considered alone. They likely depend on the genetic control developed by the symbiotic conditions. When inoculated in soybean DH4 and grown on acid medium, G3 finds the most favorable cellular conditions for the expression of its N2 fixation capacity. The G3/DH4 symbiotic association not only tolerates but prefers growing on acid medium. In conclusion it appears advisable to test the effect of inoculation of the vietnamese soybean DH4 with the strain G3 in the field, especially in the Mekong delta where soils are known to be very acid

Culture d'une légumineuse et d'une céréale dans le système zaï avec différents amendements organo-minéraux -productivité et impact sur les propriétés biologiques d'un sol ferrugineux dégradé dénudé en Région nord soudanienne au Burkina Faso

Legume and Cereal Cropping in Zaï System with Different Organo-mineral Amendments - Productivity and Impact on Biological Properties of Degraded Bare Alfisol in North Sudanian Zone of Burkina Faso. Zaï is an agricultural practice that allows the cultivation of abandoned degraded soils. An experiment was conducted from 2006 to 2012 in Burkina Faso to assess the impact of this practice on the production of sorghum and cowpea, as well as on the biological properties of soils. The experiment was set up according to a factorial experimental design in Fischer blocks. The crops were grown in the trial , received different types of organic (manure, compost) and mineral (rock phosphate) input. The results showed that the intake of simple manure and compost significantly increased the yield of the two crops. The addition of phosphate (2 t.ha-1) to compost (3 t.ha-1) and to manure (3 t.ha-1) increased the yields of cowpea and sorghum respectively by 70 to 80% and 88 to 160% compared to sole compost and manure applications. The biological activity of the soil was not influenced by the type of crop but rather by organo-mineral intakes. The combination of rock phosphate to manure had a particularly positive effect on soil biological activity. The natural phosphate intake associated with organic matter therefore appears essential to maintain crop production and soil properties