Soil contamination in the mining town of Moanda, in southwestern of Gabon, is characterized by high concentrations of Manganese. This work aims to analyze the impact of various manganese concentrations in soils on sweet potato growth and development. The plant's seeds were obtained on the local market. The stems were grown in greenhouses in 5 media, 4 of which were enriched with manganese and 1 not enriched. The manganiferous effect was assessed by measuring biochemical and physico-chemical parameters (total chlorophyll, dry matter, total sugars). The effects of the 5 treatments were compared on the Statistica 7.2. software from an Anova. The results show that

Vegetative propagation of spontaneous multipurpose species is still limited in tropical rainforest areas of Central Africa. This study evaluates the aptitude of Pseudospondias microcarpa for aerial marcottage under the conditions of Franceville in south-eastern Gabon. The ultimate objective is its domestication and its integration into traditional agroforestry systems. A total of 102 orthotropic branches were tested on 4 different substrates: Chilean sphagnum moss, moss, male inflorescence of oil palm, and sawdust. The root induction, occurring after 30 days, extends beyond 120 days and does not depend on the substrate type. Rooting (78.43 ± 7.98%) and success rates (97.5 ± 3.42%) at 120 days were very promising. The nursery (55.56 ± 13.25%) and field (45.83 ± 19.93%) survival rates remain quite variable. However, these results indicate that Pseudospondias microcarpa var. microcarpa has a good ability to aerial marcottage. This observation constitutes a prerequisite for the further investigates the optimum conditions of weaning and cultivation. This is done in order to improve Pseudospondias microcarpa plant production through aerial marcottage. The other major result has to do with taking into account local substrates in popularizing this low-cost technique.

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Le nectar de canne à sucre (Saccharum officinarum L.) est utilisé au Gabon non seulement pour la fabrication du sucre industriel, mais également pour la synthèse traditionnelle de vins locaux appelés ‘‘Musungu’’ ou ‘‘Malamba’’. Ces synthèses alcooliques nécessitent l’emploi de nombreux adjuvants dont le rôle exact reste mal défini. Le présent travail a été initié pour étudier l’un d’eux, le bois amer (Garcinia kola) utilisé dans diverses synthèses alcooliques. La méthodologie a consisté à analyser l’évolution de certaines qualités physicochimiques et biochimiques de 1 l des nectars de canne à sucre seuls (témoin), associés à la lie d’anciens vins de canne (Li), au bois amer (Gk) ou à ces 2 amendements (LG), avant et après 4 semaines de fermentation. Les résultats obtenus ont révélé la baisse de l’acidité, de la densité et des sucres totaux dans tous les traitements essais, contrairement aux témoins, après les 28 jours d’incubation. Tous les traitements (essais et témoins) ont en revanche produit des alcools de fortes teneurs comprises entre 7,4 °GL et 9,9 °GL. Mais les vins des traitements témoins quoique très alcoolisés ont tous été jugés aigres et de très mauvaise qualité gustative. Le bois amer ne paraît donc pas intervenir dans les processus de fermentation alcoolique, mais dans la constitution des qualités organoleptiques, en empêchant la prolifération des germes lactiques. Ainsi, dans la perspective d’optimiser la qualité du vin, identifier les germes participants à la fermentation du nectar de canne, sous l’influence de Garcia kola semble être nécessaire.Mots clés : Nectar, Levures, Adjuvants, Alcool, Qualité organoleptique. English Title: Effect of Garcinia kola (Clusiaceae) in the fermentation processes of sugar cane wine (<i>Saccharum officinarum</i> ; Poaceae) in Gabon Sugarcane nectar (Saccharum officinarum L.) is used in Gabon not only for the production of industrial sugar, but also for the traditional synthesis of local wines called ''Musungu'' or ''Malamba''. These alcoholic syntheses require the use of many adjuvants whose exact role remains poorly defined. The present work was undertaken to study one of them, the bitter wood (Garcinia kola) used in various alcoholic syntheses. The methodology consisted of analyzing the evolution of certain of physicochemical and biochemical qualities of 1 l of sugar cane nectars alone (control), associated with the lees of old cane wines (Li), bitter wood (Gk) or 2 amendments (LG), before and after 4 weeks of fermentation. The results obtained revealed the decrease of the acidity, the density and the total sugars in all the treatments tests, contrary to the controls, after the 28 days of incubation. On the other hand, all the treatments (tests and controls) produced alcohols with high contents of between 7.4 °GL and 9.9 °GL. But the wines of the control treatments, although very alcoholic, have all been judged as sour and of very poor taste quality. Bitter wood therefore does not appear to be involved in the processes of alcoholic fermentation, but in the constitution of organoleptic qualities, by preventing the proliferation of lactic acid bacteria. Thus, in order to optimize the quality of the wine, identifying the germs involved in the fermentation of cane nectar, under the influence of Garcia kola seems to be necessary.Keywords: Nectar, Yeasts, Additive, Alcohol, Organoleptic quality.

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