Déterminisme génétique du nombre de cæca pyloriques chez la Truite fario (Salmo trutta, Linné) et la Truite arc-en-ciel (Salmo gairdneri, Richardson) II. – Effet du génotype du milieu d'élevage et de l'alimentation sur la réalisation du caractère chez la Truite arc-en-ciel

International audienc

Fertilization Strategies Based on Climate Information to Enhance Food Security Through Improved Dryland Cereals Production

Rainfall uncertainty and nutrient deficiency affect sorghum production in Sahel. This study aimed at (i) determining the responses (varieties*water*nitrogen) of various West-African sorghum (Sorghum bicolor L. Moench) varieties to the application of fertilizer (NPK and urea) at selected growing stages according to water regime (irrigated or not, different rainfall patterns) and (ii) simulating them to define alternative fertilization strategies. This chapter proposes alternative fertilization strategies in line with rainfall patterns. Split plot experiments with four replications were carried out in two locations (Senegal), with four improved sorghum varieties (Fadda, IS15401, Soumba and 621B). Treatments were T1, no fertilizer; T2 = 150 kg/ha of NPK (15-15-15) at emergence +50 kg/ha of urea (46%) at tillering +50 Kg/ha of urea at stem extension; T3 = half rate of T2 applied at the same stages; T4 = 150 kg/ha of NPK + 50 kg/ha of urea at stem extension +50 kg/ha of urea at heading, and T5 = half rate of T4 applied at the same stages. Plant height, leaf number, grain yield, and biomass were significantly affected by the timing and rate of fertilizers. Grain yield were affected by water*nitrogen and nitrogen*variety interactions. It varied from 2111 to 261 kg/ha at “Nioro du Rip” and from 1670 to 267 kg/ha at “Sinthiou Malème”. CERES-Sorghum model overestimated late fertilizer grain yields. To achieve acceptable grain yield, fertilizers application should be managed regarding weather

O efeito de borda influencia a estrutura da comunidade vegetal em uma floresta tropical seca?

Efeitos de borda são considerados fator-chave na regulação da estrutura de comunidades vegetais em diferentes ecossistemas. Entretanto, apesar dos poucos estudos relacionados, o efeito de borda parece não ser determinante em regiões semiáridas, como a floresta tropical seca brasileira, conhecida como Caatinga. Este estudo testou a hipótese nula de que a comunidade vegetal arbustivo-arbórea não sofre alterações em sua estrutura, riqueza e composição devido ao efeito de borda. Foram instaladas 24 parcelas (20 x 20 m) em um fragmento de Caatinga arbórea, sendo 12 parcelas na borda do fragmento e 12 parcelas no seu interior. A riqueza, abundância e composição das espécies não diferiram estatisticamente entre as parcelas de borda e interior. Os resultados deste estudo corroboram um possível padrão de ambientes semiáridos e contrastam com resultados anteriores de diferentes ambientes, como florestas tropicais úmidas, cerrado e floresta de araucária. Indicam diferenças abruptas entre comunidades vegetais da borda e do interior de fragmentos florestais, sugerindo que a comunidade arbustivo-arbórea da Caatinga não é ecologicamente afetada pela presença de bordas._________________________________________________________________________________________ ABSTRACT: Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m) were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges

Méthode de mesure de la longueur de diffusion dans des rubans de silicium polycristallin destinés à la conversion photovoltaïque

A method easy to impliment has been set up which enables the measurement of diffusion length with good precision in polysilicon ribbons of p type whose characteristics are those necessary for solar cells. This method is based on the study of Schottky diode obtained through a mercury-silicon contact.Une méthode simple a été mise au point qui permet de mesurer, avec une bonne précision, la longueur de diffusion des électrons dans des rubans de silicium polycristallin de type p dont les caractéristiques sont celles requises pour fabriquer des photopiles. Elle est basée sur l'étude d'une diode Schottky réalisée au moyen d'un contact mercure-silicium

Temperature stress induces notochord abnormalities and heat shock proteins expression in larval green sturgeon (Acipenser medirostris Ayres 1854)

The effects of thermal stress on survival, development and heat shock protein (hsp) expression of green sturgeon (GS) yolk-sac larvae, from hatching through yolk depletion were investigated to provide insight into effects of highly altered natural river hydrographs. Hatched GS larvae were reared at constant water temperatures 18°C (control) through 28°C at 2°C increments. Larval survival significantly decreased at 26-28°C, with 28°C being lethal. Significant proportions of deformed larvae were found at sub-lethal (20-26°C) and lethal 28°C rearing temperatures, with kyphosis (i.e. backward flexion of notochord) accounting for >99% of morphological deformities. Histological analysis of larvae preparations indicate that elevated water temperature affects notochord cell function and physiology. At rearing temperatures 20-28°C, thermal stress elicited a quick (24 h) and long lasting (yolk-sac absorption) significant over-expression of measured heat shock proteins (hsps), all of which are known components of intracellular protein repair and stabilization mechanism. Thermal sensitivity, as indicated by the incidence of abnormalities and expression of different hsps, varied significantly between crosses. Thermally tolerant progeny exhibited a short but rapid hsp72 (size in kDa) over-expression, and more pronounced hsp60 and hsp90 over-expression, than less tolerant progeny which exhibited a prolonged hsp72 and hsp78 over-expression. At environmentally relevant water temperatures bent larvae exhibited spiral swimming, which in the wild would compromise the ability of emerging larvae to forage, avoid predators, and migrate downstream, ultimately compromising survival and recruitment. Before larvae hsp content can be used as a thermal-stress biomarker for GS, field validation studies are needed. © 2013 Blackwell Verlag GmbH