New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering

International audienceA new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction (SXRD) and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum (UHV) and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100 K in UHV and 600 K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactor in the pressure range of 1-1000 mbars and as a continuous flow cell for pressure lower than 10−3 mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd8Ni92(110) surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules

Origin of Crazing in Deuterated KDP Crystals

International audienceThe H/D isotopic exchange between DKDP crystals [K(H(1-x)Dx)2PO4] and their environment causes a surface damage known as crazing. By studying crystals, grown under perfectly stationary conditions, with a combination of analysis techniques (surface microtopography, micro-Raman spectroscopy, X-ray diffraction topography, trace element analysis) we were able to determine the localization of the isotopic exchange, quantify it, and connect it with a preferential incorporation of impurity. This enables us to propose a direct correlation between the growth mechanisms governing the impurity incorporation, the increase of proton diffusion in the structure in that part of the crystal hence on the localization, and the magnitude of crazing upon aging of the DKDP crystals

Expériences in situ sur le CRG- D1B par couplage de mesure thermogravimétrique et diffraction de neutrons

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An Interactive micromanipulation station combined to a confocal XRF instrument: proof of concept

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Cytokinins and abscisic acid act antagonistically in the regulation of the bud outgrowth pattern by light intensity

Bud outgrowth is a key process in the elaboration of yield and visual quality in rose crops. Although light intensity is well known to affect bud outgrowth, little is known on the mechanisms involved in this regulation. The objective of this work was to test if the control of bud outgrowth pattern along the stem by photosynthetic photon flux density (PPFD) is mediated by sugars, cytokinins and/or abscisic acid in intact rose plants. Rooted cuttings of Rosa hybrida 'Radrazz' were grown in growth chambers under high PPFD (530 m mol m 2 s 1) until the floral bud visible stage. Plants were then either placed under low PPFD (90 m mol m(-2) s(-1)) or maintained under high PPFD. Bud outgrowth inhibition by low PPFD was associated with lower cytokinin and sugar contents and a higher abscisic acid content in the stem. Interestingly, cytokinin supply to the stem restored bud outgrowth under low PPFD. On the other hand, abscisic acid supply inhibited outgrowth under high PPFD and antagonized bud outgrowth stimulation by cytokinins under low PPFD. In contrast, application of sugars did not restore bud outgrowth under low PPFD. These results suggest that PPFD regulation of bud outgrowth in rose involves a signaling pathway in which cytokinins and abscisic acid play antagonistic roles. Sugars can act as nutritional and signaling compounds and may be involved too, but do not appear as the main regulator of the response to PPFD

Assessing the impact of environmental factors on plant architecture through an integrative approach

National audiencePlant architecture determines yield, vigour, pathogen resistance of a crop as well as shape and visual quality of plants. Controlling the establishment of plant architecture is therefore a key concern for plant breeders and horticultural growers of field and greenhouse crops. Environmental factors have a strong impact on plant architecture. Better understanding and controlling these factors should allow better mastering cultural practices and increase yield but also reduce the use of chemicals (pesticide and growth retardants). In the case of ornamental crops, this may contribute to better master plant shape and offer the way to create new products. However, the understanding of how the environment modulates plant architecture is still poor and further research is needed. To address this question, ARCH-E (Architecture and Environment) team of the Research Institute on Horticulture and Seeds (IRHS, Angers, France) is developing an integrative research program whereby environmental effects on the establishment of plant architecture are examined from the molecular to the all plant levels. Rosebush is the model plant studied in this program. Architectural analysis is used to describe and objectively discriminate plant shapes (Morel et al., 2009, Chéné et al; 2012) and the impact of environmental factors, such as quantity and quality of light, nitrogen or water restriction or mechanical stimulation on the architectural components is studied (Thélier et al., 2011, Abidi et al; 2012, Morel et al., 2012). Beside, tools to assess plant shape through sensory analysis are developed and used to train panels of assessors to characterize the rosebush visual quality (Boumaza et al; 2010). The more in-depth study of the effect of light on rose architecture is carried on and has revealed that light was essential to bud outgrowth in rose, and that blue or red lights could, each individually, trigger bud burst (Girault et al; 2008). Light was shown to be required to stimulate sugar transport (Henry et al; 2011), sugar metabolism (Girault et al, 2010) and sugar signaling (Rabot et al., 2012) as well as the synthesis of the plant hormone gibberellic acid (Choubane et al ; submitted). On the basis of these researches, functional and structural modeling is undergone to integrate these results and simulate branching in response to the light environment (Bertheloot et al., 2011

Assessment of the rose bush floribundity and architecture

International audienceFloribundity defined as “the capacity of a plant to produce abundant flowers at high density on each of its branches”, is a key element of the aesthetic quality of the ornamental plants. In the case of many species, including the rosebush, this feature is strongly related to the plant architecture which is determined by the genotype, the environment and the crop management. To address these questions, the Architecture and Environment (ARCH-E) team of the Research Institute on Horticulture and Seeds (http://www6.angers-nantes.inra.fr/irhs) in collaboration with the Genetic determinism & Diversity of Ornamental plants (GDO) team of the same institute, is developing an integrative research program whereby environmental effects on the establishment of the plant architecture are examined from the molecular to the whole plant levels using plant sciences (physiology, genetics, molecular biology, biochemistry…), sensory analysis and modelling studies. The aim of the poster is to present a review of the studies (listed below) managed by the team, focusing on methods to assess and compare the floribundity of some rose cultivars, considered as example varieties by the International Union for the Protection of New Varieties of Plants (UPOV)