Analyse des mécanismes d'adsorption et de désorption du fer ferreux dans les milieux saturés

Des cinétiques d'adsorption et de désorption du fer ferreux par le sol ont été effectuées lors d'expériences réalisées en hypoxie. Les résultats obtenus, complétés par des mesures de Eh, de pH ainsi que de l'échangéabilité du fer adsorbé, aboutissent à une caractérisation de l'adsorption. Ils mettent en évidence une certaine réversibilité de l'adsorption du fer ferreux. Les comportements différents des échantillons étudiés démontrent l'existence d'intéractions à l'interface sol-solution dépendant des teneurs et de la nature des constituants du sol et plus particulièrement des argile

The Greater Phenotypic Homeostasis of the Allopolyploid Coffea arabica Improved the Transcriptional Homeostasis Over that of Both Diploid Parents

Polyploidy impacts the diversity of plant species, giving rise to novel phenotypes and leading to ecological diversification. In order to observe adaptive and evolutionary capacities of polyploids, we compared the growth, primary metabolism and transcriptomic expression level in the leaves of the newly formed allotetraploid Coffea arabica species compared with its two diploid parental species (Coffea eugenioides and Coffea canephora), exposed to four thermal regimes (TRs; 18-14, 23-19, 28-24 and 33-29°C). The growth rate of the allopolyploid C. arabica was similar to that of C. canephora under the hottest TR and that of C. eugenioides under the coldest TR. For metabolite contents measured at the hottest TR, the allopolyploid showed similar behavior to C. canephora, the parent which tolerates higher growth temperatures in the natural environment. However, at the coldest TR, the allopolyploid displayed higher sucrose, raffinose and ABA contents than those of its two parents and similar linolenic acid leaf composition and Chl content to those of C. eugenioides. At the gene expression level, few differences between the allopolyploid and its parents were observed for studied genes linked to photosynthesis, respiration and the circadian clock, whereas genes linked to redox activity showed a greater capacity of the allopolyploid for homeostasis. Finally, we found that the overall transcriptional response to TRs of the allopolyploid was more homeostatic compared with its parents. This better transcriptional homeostasis of the allopolyploid C. arabica afforded a greater phenotypic homeostasis when faced with environments that are unsuited to the diploid parental specie

Metabolic pathways in tropical dicotyledonous albuminous seeds: Coffea arabica as a case study

The genomic era facilitates the understanding of how transcriptional networks are interconnected to program seed development and filling. However, to date, little information is available regarding dicot seeds with a transient perisperm and a persistent, copious endosperm. Coffea arabica is the subject of increasing genomic research and is a model for nonorthodox albuminous dicot seeds of tropical origin.The aim of this study was to reconstruct the metabolic pathways involved in the biosynthesis of the main coffee seed storage compounds, namely cell wall polysaccharides, triacylglycerols, sucrose, and chlorogenic acids. For this purpose, we integrated transcriptomic and metabolite analyses, combining real-time RT-PCR performed on 137 selected genes (of which 79 were uncharacterized in Coffea) and metabolite profiling.Our map-drawing approach derived from model plants enabled us to propose a rationale for the peculiar traits of the coffee endosperm, such as its unusual fatty acid composition, remarkable accumulation of chlorogenic acid and cell wall polysaccharides.Comparison with the developmental features of exalbuminous seeds described in the literature revealed that the two seed types share important regulatory mechanisms for reserve biosynthesis, independent of the origin and ploidy level of the storage tissue

Le palmier dattier en Mauritanie

Importance socio-économique du palmier dattier L’exploitation du palmier dattier constitue une source de revenus financiers appréciable pour les habitants des oasis. Toutes les parties du palmier dattier sont utilisables : les dattes servent à l’alimentation de l’homme ; les folioles des palmes et les noyaux alimentent les animaux domestiques ; le bois du stipe, ainsi que la nervure principale et le pétiole des palmes, servent de matériaux de construction. La phœniciculture favorise le dévelo..