Mineral‐nitrogen and phosphorus leaching from vegetable gardens in Niamey,Niger

Urban and periurban agriculture (UPA) contributes significantly to meeting increasing food demand of rapidly growing urban populations in West African cities. The often intensive high‐input vegetable production within UPA results in large positive nutrient balances, being presumably linked to strong nutrient leaching which needs quantification. This study aimed at estimating leaching losses of mineral N and P in three representative urban gardens of Niamey, Niger, using ion‐exchange‐resin cartridges installed below the crop rooting zone at 0.6 m soil depth. In 2007, a year with below‐average annual rainfall (425 mm as compared to 542 mm), mean leaching of mineral N amounted to 5.9 and 7.3 kg N ha^–1 for two gardens with > 80% sand fraction and only 2.2 kg N ha^–1 for a garden with 40% silt and clay. Apparent annual P leaching was 0.7 kg P ha^–1 in all three gardens. Additional multiannual studies are necessary to assess the effect of inter‐ and intraannual variation in precipitation on nutrient leaching in intensive UPA vegetable production of semiarid West Africa.     

Effect of hesperetin,a citrus flavonoid,on the liver triacylglycerol content and phosphatidate phosphohydrolase activity in orotic acid-fed rats

The effect of dietary hesperetin on the hepatic lipid content and the enzyme activities involved in triacylglycerol (TG) synthesis in rats fed diets with or without 1% orotic acid (OA) was studied. Hepatic TG content was raised by approximately 5-fold after administration of OA for 10 days. The OA-feeding significantly increased the activity of hepatic microsomal phosphatidate phosphohydrolase (PAP), which is the rate-limiting enzyme for TG synthesis. Hepatic glucose-6-phosphate dehydrogenase (G6PDH) and malic enzyme activities were also increased. An addition of 1% hesperetin to the OA-supplemented diet resulted in the decrease of the hepatic TG content by 44% and of microsomal PAP activity. Dietary hesperetin alone neither affected liver TG content nor PAP activity significantly. OA-feeding caused an increased liver cholesterol level, whereas simultaneous addition of hesperetin and OA reduced its content to the control level. A slight reduction of hepatic cholesterol by hesperetin was also observed in the OA-free dietary group. The present study demonstrated that dietary hesperetin can reduce the hepatic TG accumulation induced by OA, and this was associated with the reduced activity of TG synthetic enzyme, PAP.     

Nitrogen fluxes during the initial stage of willows and poplars in short‐rotation coppices

Among energy crops, short‐rotation coppices (SRC) are recommended to provide renewable energy. Compared to annual crops, willows and poplars are regarded as plants with low requirements for nutrients, herbicides, pesticides, and soil maintenance. However, only little is known about N‐fertilizer effects on SRC and the few studies are even inconsistent. Therefore, we studied the effects of N on yields of willows and poplars in a field experiment. The effects of N fertilization on nitrate leaching and nitrous oxide emissions from the loamy‐sand soil were also measured. Cuttings of willows (Salix viminalis clone Inger) and poplars (Populus maximovizcii × P. nigra clone max 4) were planted on farmland in 2008. The experiment was arranged in a random block design with three levels of N fertilizer (0, 50, and 75 kg N ha^–1 y^–1). After 2 y, the trees were harvested for the first time. Fertilization did not affect the yields of willows or poplars. However, the application of 75 kg N ha^–1 y^–1 caused an average increase of N leaching in the willow and poplar plots of 25 kg N ha^–1 y^–1 and 40 kg N ha^–1 y^–1, respectively. Emissions of N₂O were increased by a maximum of only 0.2 kg N ha^–1 y^–1. Further, the N fertilizer stimulated the growth of the weed biomass in case of the willow plots by 46% and of the weed N content by 52% (r = 0.53). In conclusion, in the first 2 y, SRC could be produced in a more effective and environmentally friendly manner without mineral fertilizer.     

In Vitro Evaluation of Antioxidant Potential of the Invasive Seagrass Halophila stipulacea

Marine organisms with fast growth rates and great biological adaptive capacity might have biotechnological interests, since ecological competitiveness might rely on enhanced physiological or biochemical processes’ capability promoting protection, defense, or repair intracellular damages. The invasive seagrass Halophila stipulacea, a non-indigenous species widespread in the Mediterranean Sea, belongs to this category. This is the premise to investigate the biotechnological interest of this species. In this study, we investigated the antioxidant activity in vitro, both in scavenging reactive oxygen species and in repairing damages from oxidative stress on the fibroblast human cell line WI-38. Together with the biochemical analysis, the antioxidant activity was characterized by the study of the expression of oxidative stress gene in WI-38 cells in presence or absence of the H. stipulacea extract. Concomitantly, the pigment pool of the extracts, as well as their macromolecular composition was characterized. This study was done separately on mature and young leaves. Results indicated that mature leaves exerted a great activity in scavenging reactive oxygen species and repairing damages from oxidative stress in the WI-38 cell line. This activity was paralleled to an enhanced carotenoids content in the mature leaf extracts and a higher carbohydrate contribution to organic matter. Our results suggest a potential of the old leaves of H. stipulacea as oxidative stress damage protecting or repair agents in fibroblast cell lines. This study paves the way to transmute the invasive H. stipulacea environmental threat in goods for human health.