Glyphosate Alters Aboveground Net Primary Production,Soil Organic Carbon,and Nutrients in Pampean Grasslands (Argentina)

We have previously demonstrated that recurrent application of glyphosate causes dramatic shift in the vegetation structure of the native grasslands of Flooding Pampa. As these structural changes might alter functional processes such as primary production, carbon, nitrogen and phosphorus cycling, this study aims to evaluate functional changes associated with the application of glyphosate in these temperate grasslands. We measured aboveground net primary production (ANPP) during two consecutive years, and the concentration of organic carbon, nitrogen and phosphorus in the soil during the following six years after primary production measurements ended in glyphosate treated and non- treated (control) paddocks of a commercial livestock far. We related the vegetation data, basal cover, species richness and diversity, obtained in a previous study conducted in the same paddocks of the livestock farm, with ANPP data obtained in this one. Late summer applications of glyphosate greatly reduced the biomass contribution of warm-season perennial grasses and legumes and increased the contribution of cool season annual grasses, altering the seasonal pattern of ANPP. As the reduction of the spring and summer productivity could not be compensated by the increase of cool-season productivity, the annual ANPP was lower in the glyphosate-treated paddocks than in control paddocks. Glyphosate applications also decreased soil organic carbon and phosphorus concentration, probably because of the reduction of ANPP, the changes of its seasonal distribution and the shift in the floristic composition of the community, which may modify the amount and quality of the litter. We found a linear positive relationship between basal cover, species richness and species diversity with ANPP, which suggest that the negative effects on ecosystem functioning would be directly related with the changes in vegetation structure caused by glyphosate application.     

Osteogenic potential of sorted equine mesenchymal stem cell subpopulations

The objectives of this study were to use non-equilibrium gravitational field-flow fractionation (GrFFF), an immunotag-less method of sorting mesenchymal stem cells (MSCs), to sort equine muscle tissue-derived mesenchymal stem cells (MMSCs) and bone marrow-derived mesenchymal stem cells (BMSC) into subpopulations and to carry out assays in order to compare their osteogenic capabilities. Cells from 1 young adult horse were isolated from left semitendinosus muscle tissue and from bone marrow aspirates of the fourth and fifth sternebrae. Aliquots of 800 × 10³ MSCs from each tissue source were sorted into 5 fractions using non-equilibrium GrFFF (GrFFF proprietary system). Pooled fractions were cultured and expanded for use in osteogenic assays, including flow cytometry, histochemistry, bone nodule assays, and real-time quantitative polymerase chain reaction (qPCR) for gene expression of osteocalcin (OCN), RUNX2, and osterix. Equine MMSCs and BMSCs were consistently sorted into 5 fractions that remained viable for use in further osteogenic assays. Statistical analysis confirmed strongly significant upregulation of OCN, RUNX2, and osterix for the BMSC fraction 4 with P < 0.00001. Flow cytometry revealed different cell size and granularity for BMSC fraction 4 and MMSC fraction 2 compared to unsorted controls and other fractions. Histochemisty and bone nodule assays revealed positive staining nodules without differences in average nodule area, perimeter, or stain intensity between tissues or fractions. As there are different subpopulations of MSCs with different osteogenic capacities within equine muscle- and bone marrow-derived sources, these differences must be taken into account when using equine stem cell therapy to induce bone healing in veterinary medicine.     

Production and evaluation of potassium fertilizers from silicate rock

Rising price and limited geographical availability of traditional sources of potassium (K) fertilizers have stimulated a search for alternative K sources in different parts of the world. We evaluated mineral transformations and agronomic properties of an alternative source of K produced through thermal and chemical treatment of the verdete rock (VR). Chemical and mineralogical characteristics were evaluated before and after each treatment. Four K sources (verdete rock, KCl, acidified verdete, and calcinated verdete) were applied to a Typic Hapludox at different rates. Eucalyptus and sequentially cropped maize and grass were grown in the treated soils. Verdete rock, which contained glauconite and microcline as K crystalline minerals, had very low solubility in water and in citric acid. Thermal and chemical treatments increased the concentration of water soluble K and citric acid soluble K. These treatments also caused crystalline K minerals to collapse and form sylvite and arcanite. Untreated verdete rock was not suitable as a K source for maize (Zea mays L.) and eucalyptus (Eucaliptus urograndis I144). Thermal and chemical treatments increased agronomic performance of VR to be similar to KCl. When K was applied as K‐calcined verdete, 82% of the total K was recovered in maize and grass cultivations. Less K was recovered in plant following addition of K‐acidified verdete and KCl (72% and 77%, respectively). Potassium recoveries by eucalyptus were about 52, 53, and 60% of the amount applied of calcined verdete, acidified verdete, and KCl, respectively. Both calcination and thermal treatment increased the K uptake and dry matter production for all plant species tested to be similar to KCl suggesting that this silicate rock could be beneficiated to be an effective K fertilizer.     

Reintroduction of a dioecious aquatic macrophyte (Stratiotes aloides L.) regionally extinct in the wild. Interesting answers from genetics

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Can patch size and patch distance improve the recolonization of mussel‐seed beds exploited for aquaculture?

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White spot syndrome virus (WSSV) infection and immunity responses in white shrimp (Litopenaeus vannamei) exposed to sublethal levels of metals

To determine if exposure to a sublethal mixture of metals (Cd, Cu, Fe, Mn, Pb and Zn) increases susceptibility to White spot syndrome virus (WSSV) infection, Litopenaeus vannamei juveniles were fed WSSV‐infected shrimp tissues after 21 days of exposure to the metal mixture (WS‐MM treatment). Other treatments consisted of shrimp not exposed to metals and fed infected tissues (WS), and shrimp fed healthy tissues and exposed (MM) or not exposed to metals (C). The presence of viral DNA and inclusion bodies was detected at 32 hr postinfection (hpi) in the stomach epithelium of shrimp from the WS treatment, and eight hours later in shrimp from the WS‐MM treatment, possibly because of an initial negative effect of metals in viral replication. At 40 hpi, the severity of infection represented by the histopathological index increased in both WS and WS‐MM treatments, and values were higher in WS‐MM than in WS shrimp at the end of the experiment. From 56 hpi to the end of experiment, total hemocyte counts were lower in both WS‐MM and WS treatments, and concentrations were particularly low in WS‐MM shrimp. Conversely, phenoloxidase activity was higher in the WS‐MM treatment from 32 to 56 hpi, suggesting a possible role of the prophenoloxidase (proPO) system in the antiviral defense against WSSV. The presence of heavy metals at sublethal concentrations may increase shrimp susceptibility to WSSV; this is supported by a decrease in circulating hemocytes, an increase in the humoral response, and the development of a higher number of WSSV inclusion bodies.     

Studies of various elements of nutritional and toxicological interest associated with different molecular weight fractions in Brazil nuts

On-line hyphenation of size exclusion chromatography (SEC), UV, and inductively coupled plasma mass spectrometry (ICP-MS) was used to study the molecular weight distribution patterns of several elements in Brazil nuts (Bertholletia excelsa). This technique was used for the elemental speciation of different elements of nutritional and toxicological interests such as Mg, Fe, Co, Mo, Ag, Hg, and Pb. Elemental fractionation in Brazil nuts was studied using a Superdex peptide column with resolving capacity in the range of 14 to 0.18 kDa. Three different mobile phases, Tris buffer solution (pH 8.0), phosphate buffer (pH 7.5), and CAPS buffer solution (pH 10.0), were tried for the SEC fractionation. Size exclusion fractionation of all the extracted solutions was performed using a 50 mmol L(-)(1) Tris buffer (pH 8) as the mobile phase at a flow rate of 0.6 mL min(-)(1). Three different extractions, 0.05 mol L(-)(1) NaOH, 0.05 mol L(-)(1) HCl, and hot water at 60 degrees C, were performed, and the association of elements with various molecular weight fractions was evaluated. Total elemental concentrations in the extracted samples were determined and compared with the values obtained after total digestion to calculate the recovery values. Generally, high extraction efficiency was obtained with the NaOH solution as compared with HCl and hot water except in the case of magnesium, for which HCl was found to be a good extractant. Chromatographic elution profiles for these extractions were quite distinct from each other in most cases. Most of the elemental species were found to be associated with high molecular weight fractions. To study the differences obtained during the sample-processing step, the results obtained for nuts with shell were treated differently from those obtained for nuts purchased without shell and were compared.