Genetic variation of xylem hydraulic properties shows that wood density is involved in adaptation to drought in Douglas-fir (Pseudotsuga menziesii (Mirb.))

Relationships between wood density and hydraulic efficiency and safety (hydraulic specific conductivity and vulnerability to cavitation, respectively) could clarify the physiological process explaining the impact of density on fitness. We have used new, relatively high-throughput phenotyping methods to estimate genetic variation of wood hydraulic specific conductivity (ks) and vulnerability to cavitation (VC) as an important step toward demonstrating the adaptive value of wood density.Estación Experimental Agropecuaria BarilocheFil: Dalla Salda, Guillermina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; ArgentinaFil: Martinez Meier, Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; ArgentinaFil: Cochard, Hervé. Institut National de la Recherche Agronomique (INRA); FranciaFil: Rozenberg, Philippe. Institut National de la Recherche Agronomique (INRA); Franci

Intérêts des semences commerciales améliorées de palmier à huile (Elaeis guineensis Jacq.)

Breeders market oil palm seeds that are intended to provide users with high-yielding, quality planting material. They alone can spare growers some cruel disappointments. Given particular biological and genetic characteristics, they are able to overcome problems associated with the heredity of shelf thickness and with inbreeding depression, and to take advantage of heterosis in their varietal creation and propose seeds tolerant of diseases, etc. Compared to "unselected" seeds, marketed seeds produce 2 1/2 times more, simply by taking into account the heredity of shell thickness and inbreeding depression. Moreover, breeders have regularly increased the productivity of their materials. Under conditions in Côte d'lvoire, yields have increased from 2 to 3.6 tons of oil per hectare per year in the lost 40 years. Breeders are also attempting to find solutions to diseases (vascular wilt, Ganoderma) which destroy up to 50% of plantings. For instance, in the case of vascular wilt in Africa, the impact of the disease has been considerably reduced (to 1%). Lastly, reducing vertical growth facilitates harvesting or the decision to replant. Only seeds marketed by breeders can secure the initial investment involved in setting up or renewing an oil palm plantation. (Résumé d'auteur

Modelling the mechanical behaviour of pit membranes in bordered pits with respect to cavitation resistance in angiosperms

Background and Aims Various correlations have been identified between anatomical features of bordered pits in angiosperm xylem and vulnerability to cavitation, suggesting that the mechanical behaviour of the pits may play a role. Theoretical modelling of the membrane behaviour has been undertaken, but it requires input of parameters at the nanoscale level. However, to date, no experimental data have indicated clearly that pit membranes experience strain at high levels during cavitation events. Methods Transmission electron microscopy (TEM) was used in order to quantify the pit micromorphology of four tree species that show contrasting differences in vulnerability to cavitation, namely Sorbus aria, Carpinus betulus, Fagus sylvatica and Populus tremula. This allowed anatomical characters to be included in a mechanical model that was based on the Kirchhoff–Love thin plate theory. A mechanistic model was developed that included the geometric features of the pits that could be measured, with the purpose of evaluating the pit membrane strain that results from a pressure difference being applied across the membrane. This approach allowed an assessment to be made of the impact of the geometry of a pit on its mechanical behaviour, and provided an estimate of the impact on air-seeding resistance. Key Results The TEM observations showed evidence of residual strains on the pit membranes, thus demonstrating that this membrane may experience a large degree of strain during cavitation. The mechanical modelling revealed the interspecific variability of the strains experienced by the pit membrane, which varied according to the pit geometry and the pressure experienced. The modelling output combined with the TEM observations suggests that cavitation occurs after the pit membrane has been deflected against the pit border. Interspecific variability of the strains experienced was correlated with vulnerability to cavitation. Assuming that air-seeding occurs at a given pit membrane strain, the pressure predicted by the model to achieve this mechanical state corresponds to experimental values of cavitation sensitivity (P50). Conclusions The results provide a functional understanding of the importance of pit geometry and pit membrane structure in air-seeding, and thus in vulnerability to cavitation

Swiss French PolyPhone and PolyVar: telephone speech databases to model inter- and intra-speaker variability

Following the demand of the speech technology market, a number of companies and research laboratories joined their forces in order to produce valuable and reusable resources, especially speech databases. Serving their purpose, the collected databases are used for developing, testing, enhancing and evaluating speech technology products, like interactive voice servers, listening typewriter, speaker verification and identification systems, etc. Especially for capturing intra-speaker variability, the PolyVar database was designed and recorded at IDIAP, as a complement to the Swiss French PolyPhone database, which adresses inter-speaker variability issues. We will detail in the following the specific problems of speech database collection (sampling the speaker population, selection of vocabulary items, ...), and will present actual development we carried out at IDIAP throught the PolyPhone and PolyVar databases