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Carbon-rich dust is known to form in the atmosphere of the semiregular variable star R Sculptoris. Such stardust, as well as the molecules and gas produced during the lifetime of the star, will be spread into the Galaxy via the mass-loss process. Probing this process is crucial to understand the chemical enrichment of the Galaxy. R Scl was observed using the ESO/VLTI MATISSE instrument in December 2018. Here we show the first images of the star between 3 and 10 R*. Using the complementary MIRA 3D image reconstruction and the RHAPSODY 1D intensity profile reconstruction code, we reveal the location of molecules and dust in the close environment of the star. Indeed, the C2H2 and HCN molecules are spatially located between 1 and 3.4 R* which is much closer to the star than the location of the dust. The R Scl spectrum is fitted by molecules and a dust mixture of 90% of amorphous carbon and 10% of silicone carbide. The inner boundary of the dust envelope is estimated by DUSTY at about 4.6 R*. We derive a mass-loss rate of 1.2 ± 0.4 × 10−6M⊙ yr−1however no clear SiC forming region has been detected in the MATISSE data.

Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis ~15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, η Car A, is a luminous blue variable (LBV); the secondary, η Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV η Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims. Our aim is to study the intensity distribution and kinematics of η Car’s WWC zone. Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Brα imaging of η Car’s distorted wind. Results. We present the first VLTI-MATISSE aperture-synthesis images of η Car A’s stellar windin several spectral channels distributed across the Brα 4.052 μm line (spectral resolving power R ~ 960). Our observations were performed close to periastron passage in February 2020 (orbital phase ~ 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (~14 au). The radius of the faintest outer wind regions is ~26 mas (~60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 ± 0.06 mas (6.54 ± 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.

Context. Carbon is one of the most abundant components in the Universe. While silicates have been the main focus of solid phase studies in protoplanetary discs (PPDs), little is known about the solid carbon content especially in the planet-forming regions (~0.1–10 au). Fortunately, several refractory carbonaceous species present C-H bonds (such as hydrogenated nano-diamond and amorphous carbon as well as polycyclic aromatic hydrocarbons), which generate infrared (IR) features that can be used to trace the solid carbon reservoirs. The new mid-IR instrument MATISSE, installed at the Very Large Telescope Interferometer (VLTI), can spatially resolve the inner regions (~1–10 au) of PPDs and locate, down to the au-scale, the emission coming from carbon grains. Aims. Our aim is to provide a consistent view on the radial structure, down to the au-scale, as well as basic physical properties and the nature of the material responsible for the IR continuum emission in the inner disk region around HD 179218. Methods. We implemented a temperature-gradient model to interpret the disk IR continuum emission, based on a multiwavelength dataset comprising a broadband spectral energy distribution and VLTI H-, L-, and N-bands interferometric data obtained in low spectral resolution. Then, we added a ring-like component, representing the carbonaceous L-band features-emitting region, to assess its detectability in future higher spectral resolution observations employing mid-IR interferometry. Results. Our temperature-gradient model can consistently reproduce our dataset. We confirmed a spatially extended inner 10 au emission in H- and L-bands, with a homogeneously high temperature (~1700 K), which we associate with the presence of stochastically heated nano-grains. On the other hand, the N-band emitting region presents a ring-like geometry that starts at about 10 au with a temperature of 400 K. Moreover, the existing low resolution MATISSE data exclude the presence of aromatic carbon grains (i.e., producing the 3.3 μm feature) in close proximity tothe star (≲1 au). Future medium spectral resolution MATISSE data will confirm their presence at larger distances. Conclusions. Our best-fit model demonstrates the presence of two separated dust populations: nano-grains that dominate the near- to mid-IR emission in the inner 10 au region and larger grains that dominate the emission outward. The presence of such nano-grains in the highly irradiated inner 10 au region of HD 179218 requires a replenishment process. Considering the expected lifetime of carbon nano-grains from The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS model), the estimated disk accretion inflow of HD 179218 could significantly contribute to feed the inner 10 au region in nano-grains.Moreover, we also expect a local regeneration of those nano-grains by the photo-fragmentation of larger aggregates.

Context: FS Canis Majoris (FS CMa, HD 45677) is an unclassified B[e] star surrounded by an inclined dust disk. The evolutionary stage of FS CMa is still debated. Perpendicular to the circumstellar disk, a bipolar outflow was detected. Infrared aperture-synthesis imaging provides us with a unique opportunity to study the disk structure. Aims: Our aim is to study the intensity distribution of the disk of FS CMa in the mid-infrared L and N bands. Methods: We performed aperture-synthesis imaging of FS CMa with the MATISSE instrument (Multi AperTure mid-Infrared SpectroScopic Experiment) in the low spectral resolution mode to obtain images in the L and N bands. We computed radiative transfer models that reproduce the L- and N-band intensity distributions of the resolved disks. Results: We present L- and N-band aperture-synthesis images of FS CMa reconstructed in the wavelength bands of 3.4-3.8 and 8.6-9.0 micrometer. In the L-band image, the inner rim region of an inclined circumstellar disk and the central object can be seen with a spatial resolution of 2.7 milliarcsec (mas). An inner disk cavity with an angular diameter of 6x12mas is resolved. The L-band disk consists of a bright northwestern (NW) disk region and a much fainter southeastern (SE) region. The images suggest that we are looking at the bright inner wall of the NW disk rim, which is on the far side of the disk. In the N band, only the bright NW disk region is seen. In addition to deriving the inclination and the inner disk radius, fitting the reconstructed brightness distributions via radiative transfer modeling allows one to constrain the innermost disk structure, in particular the shape of the inner disk rim., Comment: accepted for publication in A&A

International audience; Grain legumes can contribute to cropping systems through their ability to fix atmospheric N2 in their root-nodules. However, the symbiotic nitrogen fixation process requiadditional phosphorus. Thus, the production of grain legumes, particularly common bean, is limited by P-deficiency in many soils, mostly in tropical and Mediterranean areas. Recombinant inbred lines (RILs — F8) from a cross of common bean parents BAT477 with DOR364 were selected for improved phosphorus-use efficiency and N2-dependent growth in glasshouse hydro-aeroponic culture and tested in farmers’ field. The present work with Phaseolus vulgarisas a model grain legume shows a significant difference in the overall phosphatase activity in nodules, including a relatively high level of phytase activity, between two recombinant inbred lines that contrast in their efficiency in utilization of P for symbiotic nitrogen fixation.

All common bean lines grown in Europe, as in other continents, are the result of a process of domestication and evolution (mutation, selection, migration and genetic drift), from wild forms (Phaseolus vulgaris var. aborigineus and Phaseolus vulgaris var. mexicanus) found exclusively in the Americas. Observations on morphological (e.g., bract shape), agronomic (e.g., seed size), biochemical (e.g., isozyme) and molecular variability for wild and cultivated lines, made it possible to distinguish at least two major centers of common bean domestication, namely Andean and Mesoamerican. Subsequently, new cultivars may have evolved within and between the two gene pools in Spain and Portugal, making southern Europe a secondary center of diversity for the common bean. Indeed, the first documented appearance of common bean in Europe, after the discovery of America, was in 1508 as an ornamental plant in France. This happened before it was possible to introduce common bean lines from the Andes, i.e., before Peru was explored by Pizarro in 1528. Both Andean and Mesoamerican germplasm differ by the diversity of phaseolin, a seed protein. Thus, most of the European germplasm is from Andean locations since the type T phaseolin is found in their seeds. It is thought that Mesoamerican lines were less popular because of their lower adaptability to winter cold and to short-duration summers. However, the type C phaseolin, is most frequently found in the Iberian Peninsula, although recent studies show that the populations found in northwestern Spain and Portugal are predominantly of the T-type phaseolin. Concerning their interaction with the root-symbiont rhizobia, genotypic variation has been recently found among various landraces from this region, including Great Northern, Caparron, White Kidney and Canellini commercial types, for nodulation and the N2-dependent plant growth after inoculation with Rhizobium tropici CIAT 899. It is concluded that knowledge of the origin, evolution and dissemination of common bean in Europe may be valuable information for the improvement of this legume species.

Hydrogenase activities and N2-fixing capacities of soybean nodules (Glycine max. cv. Hodgson), inoculated with strains ofBradyrhizobium japonicum andRhizobium fredii from different geographical regions, were measured after 35 days of culture under controlled conditions. Of the strains tested, 47% induced nodules with bacteroids which recycled H2. The data obtained suggest that H2-recycling ability is not a major factor influencing early N2-fixation which depends essentially on the precocity and intensity of the initial nodulation.

La presente recherche porte sur l’etude au champ d’une chlorose de l’arachide observee en zone sahelo-soudanienne d’Afrique de l’Ouest. Les mesures et observations regulierement realisees sur les plantes et sur l’activite nitrogenasique (C2H4) des nodosites, montrent que la chlorose etudiee resulte fondamentalement d’un retard et d’une deficience generale de la nodulation.

Symbiotic nitrogen fixation is inhibited in the presence of nitrate. Yarious symbiotic processes are affected including nitrogenase activity which decreases just after addition of nitrate to the medium. Experimental results suggest that this inhibition is not due to reduction of nitrate in the shoots and roots but to nitrate ion metabolism in root nodules where bacterial reduction of nitrate does not appear to play a major role. Considerable nitrate metabolism was found to occur in the plant compartment of the nodules. This could cause inhibition by nodular accumulation of nitrite produced by cytosolic nitrate reductase activity and by competition with bacteroids for the reduction energy.

The development of soybean leaves grown at fluctuating photon flux density between 100 and 1500μM m(-2)s(-1) with a period of 160 sec were compared to leaves developed under continuous light with the same mean photon flux density. Number of epidermal cells and stomata, leaf area and specific leaf weight were not affected by the periodic fluctuation of photon flux density. Chloroplastic pigment concentration and chlorophyll fluorescence reveal some photoinhibitory effects of the high photon flux density phase. Stomatal and internal CO2 conductance and the quantum yield were not affected by the light regime. In contrast ribulose 1.5 bisphosphate carboxylase/oxygenase activity before in vitro activation by CO2 and Mg(++) was stimulated by the periodic illumination whereas the total amount of the enzyme and the internal leaf CO2 conductance remained steady. In conclusion, there was no major difference between leaves of plant grown either under a steady or under a periodic fluctuation of the photon flux density except some photoinhibitory symptoms under fluctuating illumination, and a higher in vivo level of activation of the Rubisco.