Soil salinity has a negative impact on crop production over the world. The effect of salt stress on growth, chlorophyll content, mineral distribution, biochemical constituents and non-enzymatic antioxidant compounds of white yam (Dioscorea rotundata (L) var. gana) cultivar regularly consumed in Cameroon were investigated. Plants were subjected to four different levels concentrations of NaCl (0, 50, 100 and 200 mM), with 0 mM NaCl as a control. The supply of intake doses of NaCl in the culture medium significantly (P < 0.001) decreased the dry biomass (roots and shoots), growth parameters (number of leaves, noose diameter, leaf area and stem height) and chlorophyll contents from 100 mM NaCl. Mineral elements (K, Ca and Mg) and K/Na ratio significantly (P < 0.001) decreased in roots and shoots with increasing salinity. The higher sodium (Na) concentrations were recorded in shoots than in roots. The different biochemical constituents (proline (PRO), total soluble carbohydrates (CH), soluble proteins (PR) and total free amino acids (FAA)) and non-enzymatic antioxidants compounds (total phenolic (TP) and flavonoids (FLA) contents) significantly (P < 0.001) increased from 50 mM NaCl. The main strategy in cv. gana seems to increase osmotic adjustment through high accumulation of CH, PR, FAA and PRO in the leaves and they could eventually be considered as biochemical indicators of early selection and osmotic adjustment ability for salt tolerant plants. The gana variety could be encouraged to be planted on salt affected soils for the better development in salty areas.

Human activities increasingly accentuate the imbalance of hydrosystems. The aim of the study is to contribute to the knowledge of phytoplankton and some physicochemical parameters related to the Batika river with a view to proposing methods of monitoring for sustainable production of carp fry. Sampling took place monthly from March, 2019 to February, 2020. Physicochemical parameters were measured in situ and in the laboratory. The pelagic area was sampled at 7 identified stations along the river. Two groups were observed according to the physicochemical parameters made up of exclusive species. Group I bringing stations 1, 2 and 3 upstream together; group II bringing stations 5, 6 and 7 downstream closer together. Station 4 is considered a transition station between upstream and downstream. Specific richness of phytoplankton amounts to 6 classes divided into 28 genera and 34 species. The most represented class is Chlorophyceae (36%). The least represented class is Ulvophyceae (1%). Shannon-Weaver diversity index ranges from 3.24 (station 7) to 1.76 (station 4). Specific richness is not very variable from one station to another. The most common types of the study site are Closterium and Micrasterias. Physicochemical parameters show that the Batika river is less polluted. These results show that the Batika river has low phytoplankton richness and good quality water. Monitoring this river would maintain its ecological status for sustainable production of carp fry.

Human activities are causing wetland degradation. Macrophytes play an important role in the management of hydrosystems. They can therefore be used to restore a polluted environment. The aim of the study is to contribute to the phytorestoration of sewage sludge in nitrates, phosphates, cadmium, iron and lead from the Mangrove landfill of "Bois des singes" by planted filters of Pennisetum purpureum. A planted filter of P. purpureum was constructed. Sewages sludges samples were introduced into the device. Nitrates (NO 3 ), phosphates (PO 4 ), cadmium (Cd), iron (Fe) and lead (Pb) assays were carried out in water and plants at different levels of the filter (Settling basin B1, basin B2, basin B3, negative control and positive control) by absorption spectrophotometry flame atomic. The bioaccumulation and translocation factors as well as the bioaccumulation coefficient have been determined. The high contents of PO 4 (4000 mg/l), NO 3 (89 mg/l), Fe (5000 mg/l), Pb (20 mg/l) and Cd (0.08 mg/l) are greatly reduced by the filters at values below the tolerance threshold in B3 of 0.01 mg/l, 0.14 mg/l, 0.0002 mg/l, 0.0003 mg/l and 0.0003 mg/l respectively. The bioaccumulation factor shows that P. purpureum contained in barrels where the parameters are high is lead accumulator with a value of 1.305 (B2), hyperaccumulator of Fe and Cd with values of 10.05 (B2) and 13, 23 (B3). The leaf translocation is greater than 1 with Fe and Pb in the leaves of the boles. P. purpureum transfers Fe and Pb to the leaves. The planted filter of P. purpureum allows a restoration of this sewage sludge. This macrophyte extracts NO 3 , PO 4 , Cd, Fe and Pb and accumulates them in its vegetative system. P. purpureum cant be use to to restore the environment stressed by faecal sludge in the city of Douala.

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