La Régénération Naturelle Assistée (RNA) comme un moyen de reverdir le bassin arachidier au Sénégal : cas du terroir de Khatre Sy

Au Sénégal, le bassin arachidier est confronté à une réduction de la  couverture végétale exposant les sols à l’érosion éolienne et hydrique, à la baisse de la fertilité des sols, à la rareté du bois de chauffe. Face à cette situation, les populations ont réagi dans le terroir de Khatre Sy avec l’appui du Projet de Reboisement Villageois du Nord Bassin Arachidier  (PREVINOBA) en faisant la Régénération Naturelle Assistée (RNA). Cette étude évalue l’impact de la RNA sur le reverdissement du terroir de Khatre Sy. Les résultats d’inventaire montrent la présence de dix-sept espèces appartenant à onze familles dominées par les Combretaceae et les Balanitaceae. L’analyse de variance des paramètres structuraux indique une différence significative entre les arbres de la parcelle mise en défens et ceux des champs avec RNA pour le diamètre moyen du tronc et leur hauteur moyenne. Dans la mise en défens, la fréquence des arbres répond à une distribution en « L » décroissante, alors que, pour celle des champs avec RNA, il s’agit d’une distribution «en cloche ». L’ensemble du terroir de Khatre Sy présente une bonne capacité de régénération. La RNA a permis d’améliorer la densité des arbres dans les champs ouvrant de bonnes perspectives pour le reverdissement du bassin arachidier.Mots clés : Régénération naturelle assistée, reverdissement, bassin arachidier, Sénégal

Choriocarcinoma on hysterectomy specimen in Senegal: histological study

Background: Trophoblastic diseases are in general exclusive to women in their reproductive years. Gestational choriocarcinoma (GC) is a rare malignant tumor derived from the trophoblast of women in childbearing age. Our objective was to study the epidemiological and clinicopathologic aspects at the laboratories of pathological anatomy and cytology (ACP) of Aristide Le Dantec Hospital and General Idrissa Pouye Hospital.Methods: Our study was conducted in the anatomy and pathology laboratories of the Hôpital Général Idrissa Pouye and the Hôpital Aristide Le Dantec in Dakar. This study was based on records of pathological reports of gestational choriocarcinomas from these different laboratories. This was a retrospective and descriptive bi-centric study, spread over eight (8) years from January 1, 2013, to December 31, 2020. All cases diagnosed on hysterectomy specimens and with a formal conclusion of choriocarcinoma have been included. We recorded the data collected in Excel 2007 software and the analysis was made using Epi Info.Results: We collected 25 cases of choriocarcinomas. The mean age of the patients was 38.1±9.7. Mixed seat tumors (intra-cavitary and intra-mural) were the most frequent with 48% of cases. Patients who were at FIGO stage 1 represented for 88% of cases.Conclusions: Gestational choriocarcinoma (GC) is a proliferation of the trophoblast (cytotrophoblast and syncitiotrophoblast). This study has helped establish histopathological data of choriocarcinoma on hysterectomy specimen in Dakar

Extractable phosphorus and rice yield in an ultisol of the humid forest zone in West Africa

Little attention has been devoted to calibrating soil tests for phosphorus (P) in the field for upland rice in West Africa. The information is needed to improve fertilizer P recommendations. A field experiment was conducted in the rainy season of 1994 to establish the relationship between extractable P by Bray 1 and grain yield of four upland rice cultivars grown on an Ultisol in the forest zone of Ivory Coast. The critical limit of Bray 1 P in the soil at 90% relative rice grain yield varied from 12.5 to 15.0 mg P/kg of soil for the four cultivars tested. The P critical limit in the soil tended to be lower for the cultivars of rice earlier found to be efficient at converting applied P into grain yield

Plant phosphorus and rice yield in an Ultisol of the humid forest zone in West Africa

Little attention has been devoted to calibrating plant tissue tests for phosphorus (P) in the field for upland rice in West Africa, although information is needed for improving crop production through efficient P nutrition. A field experiment was conducted under rainfed conditions in the 1994 season to establish the relationships between plant P content and grain yield of upland rice grown on an Ultisol, having a range in extractable P, in the humid forest zone of Ivory Coast. The critical limit of P content in the whole rice plant tops at the tillering stage, at 90% relative grain yield, was found to be 2 g kg‐1 P for the four upland rice cultivars tested. Total P uptake in the biomass was significantly correlated with rice grain (r=0.81, n=20) and straw (r=0.79) yields of the cultivars

Direct and residual fertilizer phosphorus effects on yield and phosphorus efficiency of upland rice in an Ultisol

Phosphorus (P) deficiency is one of the major limiting factors for crop production in highly weathered soils in the humid zone of West Africa. Very few studies have evaluated the residual value of fertilizer P to rice in these soils. Field experiments were conducted for three years (1993–1995) to determine the response of four upland rice cultivars to fertilizer P applied at 0, 45, 90, 145 and 180 kg P ha-1 only once in 1993, and to fertilizer P residues in 1994 and 1995. The soil at the experimental site, in the humid forest zone of Ivory Coast (West Africa), was an Ultisol, low in available P. Grain yields of the rice cultivars were significantly increased by fertilizer P in 1993, and by the fertilizer P residues in 1994 and 1995 although the magnitude of response decreased with time since the fertilizer was applied. The cultivars differed in cumulative agronomic and physiological efficiencies, and the efficiencies were higher at the lower rates of P. The amounts of total P removed in three successive crops were similar for all the four rice cultivars although P harvest index was 10–12% higher in the P efficient than inefficient cultivars. The results suggest that the differences observed in the P efficiency of rice cultivars are due to differences in the internal efficiency of P

Response of upland rice to phosphorus in an ultisol in the humid forest zone of West Africa

Phosphorus (P) deficiency is one of the major limiting factor for crop production in highly weathered soils in the humid tropics. Field experiments were conducted for two years (1992 and 1993) to determine P response and efficiencies of upland rice cultivars in an Ultisol, low in available P, in the forest zone of Cote d'Ivoire. The rice cultivars tested were selected from a large number of entries tested earlier for acidity tolerance. Grain yields of the cultivars were significantly increased by P application. There was little further response in grain yield at higher rates than 60 kg P ha -1. The rice cultivars differed in agronomic and physiological P efficiencies and the efficiencies were higher at lower rates of R The rooting depths of the cultivars were increased by application of P at the lowest application rate (30 kg P ha-1).The results suggest that P fertilization of soil acidity-tolerant upland rice cultivars can significantly improve the productivity of the ultisols

Long-Term Phosphorus Fertilizer Effects on Phosphorus Uptake, Efficiency, and Recovery by Upland Rice on an Ultisol

Phosphorus (P) deficiency is a major constraint to upland rice production on highly weathered, low activity clay soils in the humid zone of West Africa. There is a paucity of information on the long-term fertilizer P effects on rice on these soils. A field experiment was conducted for six years (1993–1998) to determine the response of four upland rice cultivars to fertilizer P applied at 0, 45, 90, 135, and 180 kg P ha−1 only once in 1993, and to residual P in 1994, 1995, 1996, and 1998. The experimental site was located on an Ultisol, low in available P, in the humid forest zone of Côte d'Ivoire, West Africa. This paper discusses long-term P effects on P uptake and efficiency of upland rice cultivars. The cultivars evaluated differed in cumulative agronomic and physiological P efficiencies, and the efficiencies were higher at lower P rates for the P-efficient cultivars. The P uptake response and P harvest index were affected by P rate and its residual effect, which decreased with time after P was applied. The mean cumulative recovery of applied P in five crops of four rice cultivars varied from 5.5 to 9.4%. The results suggest that the variation in P efficiency of the cultivars is due to differences in the efficiency of utilization of P for grain production

Phosphorus response of Oryza sativa, O. glaberrima, and hybrid rice cultivars on an ultisol

Phosphorus (P) deficiency is a major constraint to upland rice production on Ultisols in the humid zone of West Africa. Integrated use of P-efficient cultivars and P nutrition is needed for enhanced sustainable productivity on these soils. This article reports on the P responsiveness of interspecific rice hybrids (crosses from Oryza sativa and O. glaberrima) along with O. sativa and O. glaberrima cultivars grown on an acidic Ultisol, low in available P. The cultivars differed in yield and P-uptake response to fresh and residual P. Two interspecific cultivars gave a linear response to P and produced the greatest grain yield under direct and residual P. The O. glaberrima cultivar CG 14 did not respond to the applied P, whereas the O. sativa cultivar was moderate in its performance. Our results show that the interspecific rice cultivars have the potential to adapt and perform well on acidic upland soil

Special symplectic Lie groups and hypersymplectic Lie groups

A special symplectic Lie group is a triple $(G,\omega,\nabla)$ such that $G$ is a finite-dimensional real Lie group and $\omega$ is a left invariant symplectic form on $G$ which is parallel with respect to a left invariant affine structure $\nabla$. In this paper starting from a special symplectic Lie group we show how to ``deform" the standard Lie group structure on the (co)tangent bundle through the left invariant affine structure $\nabla$ such that the resulting Lie group admits families of left invariant hypersymplectic structures and thus becomes a hypersymplectic Lie group. We consider the affine cotangent extension problem and then introduce notions of post-affine structure and post-left-symmetric algebra which is the underlying algebraic structure of a special symplectic Lie algebra. Furthermore, we give a kind of double extensions of special symplectic Lie groups in terms of post-left-symmetric algebras.Comment: 32 page