197,177 research outputs found
Use of Zebra mussel (Dreissena polymorpha) to assess trace metal contamination in the largest Italian subalpine lakes
No full textTrace metal (Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) contamination was evaluated in zebra mussels from the lakes Maggiore, Lugano, Como, Iseo and Garda, which are located in the most highly populated and industrialised area in Italy. Zebra mussels from Lake Maggiore contained the highest concentrations (3.44, 1.51, 4.97, 0.158, 5.87, 346 μg g−1 for Cd, Co, Cr, Hg, Pb, Zn, respectively) of all metals analysed except Cu and Ni. The lowest levels of most metals were in animals from Garda and Lugano (0.78 and 0.60 μg g−1 for Cd, 2.87 and 2.03 μg g−1 for Cr, 0.065 and 0.049 μg g−1 for Hg, 12.1 and 11.9 μg g−1 for Ni, 1.96 and 2.46 μg g−1 for Pb, 158 and 163 μg g−1 for Zn). The most contaminated sites and possible local sources of metals were identified for each lake, and the lakes classified into quality classes concerning metal pollution
Ascorbate oxidase is the potential conductor of a symphony of signaling pathways
No full textThe functional role of ascorbate oxidase (AO; EC 1.10.3.3) has never been fully explained so far, due to the difficulties in understanding the presence of an enzyme specifically oxidizing ascorbate with no obvious advantage, and the apparent disadvantage of lowering plant stress resistance as a consequence of ascorbate consumption. Here we suggest a complete change of perspective, by proposing an essential role of AO as a modulator of both ascorbate and oxygen content, with relevant implications related to signaling. By affecting the overall redox state, AO is actually involved in redox regulation in the extracellular matrix. In addition, AO can contribute to creating a hypoxic microenvironment, especially relevant in the maintenance of meristem identity and the establishment of mutualistic plant-microbe interactions. We also hypothesize the possible involvement of AO in the activation of a signaling cascade analogous to the mechanism of prolyl hydroxylases/Hypoxia Inducible Factors in animal
Comparing actual transpiration fluxes as measured at leaf-scale and calculated by a physically based agro-hydrological model
No full textThe primary purpose of this paper is to compare the actual transpiration rates from tomato crops, as measured at leaf scale and estimated by a macroscopic approach in an agro-hydrological model named FLOWS, under variable soil properties and water availability. To this aim, sixteen plots were cultivated with toma-toes in Metaponto, Southern Italy. Soil hydraulic properties (SHP) were obtained using a fast in situ characterisation method. Leaf-area index (LAI) was measured using a leaf-area metre. SHP and LAI were then used in the physically-based FLOWS, which allowed calculating the macroscopic transpiration rates, Ta,m. Single-leaf transpiration rates, Ta,l, and stomatal conductance, gs,l, were measured in situ. For comparison with Ta,m, gs,l was upscaled by the Big-Leaf approach to canopy scale stomatal conductance, gs,c, which was applied to the Penman-Monteith model to obtain the canopy-scale transpiration, Ta,c. Finally, multiple linear regression (MLR) was used to find the statistical relationship between Ta,m and Ta,c, and the SHP and gs,c. Results showed that the macroscopic approach smooths the spatial variability of transpiration rates. Ta,c increased with the saturated water content, θs, and the slope of the water retention curve, n, while Ta,m decreased with increasing θs and n. MLR improved significantly by introducing gs,c to predict Ta,m
Mitigation of nitrogen pollution in vegetated ditches fed by nitrate-rich spring waters
No full textIn permeable soils, excess nitrate from agriculture is transported vertically and accumulates in aquifers. However, it can come back to the surface via groundwater movement and pollute watercourses. We hypothesized that vegetated ditches may mitigate significant amounts of nitrate from spring waters, and represent a buffer system to protect downstream water bodies from eutrophication. To test this hypothesis, nitrate removal was measured in ditches fed by nitrate-rich groundwater in presence and absence of emergent vegetation. Reach-scale methods (N2 open-channel, N budgets) were coupled with laboratory incubations of sediment cores (benthic N fluxes, isotope pairing) and plant N uptake estimation. Studied ditches are representative of a wide hydrological network in Northern Italy, within the so-called “spring-belt” (Po River plain), a NO3−-vulnerable area with high density of contaminated springs. Results indicated a greater reach-scale N removal in vegetated (38–84 mmol N m−2 d−1) as compared to unvegetated condition (12–45 mmol N m−2 d−1). Denitrification was the dominant N-removal pathway, while plant uptake represented a minor fraction of the net N abatement. Large development of interfaces for microbial growth provided by aquatic vegetation and more opportunities for biotic interactions are features that promote nitrate reduction in the ditch network. Despite the vegetated ditches were significant N-reactors, denitrification provided a little N-removal to in-stream high nitrate loads, with the exception of periods when plant coverage and water retention time peaked. Management of N-saturated ditches may consist in the enlargement of stretches to increase water retention and amplify the interfaces where biofilms develop, though preserving hydraulic efficiency. The maintenance of vegetation in the ditch networks would result in a significant N-abatement on a larger scale
Chemistry and isotopic composition of precipitation and surface waters in Khumbu valley (Nepal Himalaya): N dynamics of high elevation basins
No full textWe monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050 m a.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry
and to obtain insights regarding ecosystem responses to atmospheric inputs.
The major cations in the precipitation were NH4+ and Ca2+, whereas the main anion was HCO3−, which constituted approximately 69% of the anions, followed by NO3−, SO42− and Cl-. Data analysis suggested that Na+, Cl− and K+ were derived from the long-range transport of marine aerosols. Ca2+, Mg2+ and HCO3− were related to rock and soil dust contributions and the NO3− and SO42− concentrations were derived from anthropogenic sources. Furthermore, NH4+ was derived from gaseous NH3 scavenging. The isotopic composition of weekly precipitation ranged from −1.9 to −23.2‰
in δ18O, and from −0.8 to −174‰ in δ2H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation,which suggested
that other water sources contributed to the stream flow. Precipitation contentsfor all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while
in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source.
The calculated atmospheric N load (0.30 kg ha−1y−1) was considerably lower than the levels that were measured in other high-altitude environments. Nevertheless, the NO3− concentrations in the surface waters (from 2 to 17
μeq L−1) were greater than expected based on the low N inputs from wet deposition
MODULATION OF THE INWARD RECTIFIER POTASSIUM CHANNEL IRK1 BY THE RAS SIGNALLING PATHWAY
No full textLugano Switzerlan
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
The physiology of plants in the context of space exploration
No full textThe stress that the space environment can induce on plant physiology is of both abiotic and biotic nature. The abiotic space environment is characterized by ionizing radiation and altered gravity, geomagnetic field (GMF), pressure, and light conditions. Biotic interactions include both pathogenic and beneficial interactions. Here, we provide an overall picture of the effects of abiotic and biotic space-related factors on plant physiology. The knowledge required for the success of future space missions will lead to a better understanding of fundamental aspects of plant physiological responses, thus providing useful tools for plant breeding and agricultural practices on Earth
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