Nature, evolution and characterisation of rhizospheric chemical exudates affecting root herbivores

Similar to aboveground herbivores, root-feeding insects must locate and identify suitable resources. In the darkness of soil, they mainly rely on root chemical exudations and, therefore, have evolved specific behaviours. Because of their impact on crop yield, most of our knowledge in belowground chemical ecology is biased towards soil-dwelling insect pests. Yet the increasing literature on volatile-mediated interactions in the ground underpins the great importance of chemical signalling in this ecosystem and its potential in pest control. Here, we explore the ecology and physiology of these chemically based interactions. An evolutionary approach reveals interesting patterns in the response of insects to particular classes of volatile or water-soluble organic compounds commonly emitted by roots. Food web analyses reasonably support that volatiles are used as long-range cues whereas water-soluble molecules serve in host acceptance/rejection by the insect; however, data are still scarce. As a case study, the chemical ecology of Diabrotica virgifera virgifera is discussed and applications of belowground signalling in pest management are examined. Soil chemical ecology is an expanding field of research and will certainly be a hub of our understanding of soil communities and subsequently of the management of belowground ecosystem services.

Review of semiochemicals that mediate the oviposition of mosquitoes: a possible sustainable tool for the control and monitoring of Culicidae

The choice for suitable places for female mosquitoes to lay eggs is a key-factor for the survival of immature stages (eggs and larvae). This knowledge stands out in importance concerning the control of disease vectors. The selection of a place for oviposition requires a set of chemical, visual, olfactory and tactile cues that interact with the female before laying eggs, helping the localization of adequate sites for oviposition. The present paper presents a bibliographic revision on the main aspects of semiochemicals in regard to mosquitoes' oviposition, aiding the comprehension of their mechanisms and estimation of their potential as a tool for the monitoring and control of the Culicidae.

Chemical labelling of oyster shells used for time-calibrated high-resolution Mg/Ca ratios: A tool for estimation of past seasonal temperature variations

The geochemical compositions of biogenic carbonates are increasingly used for palaeoenvironmental reconstructions. The skeletal delta O-18 temperature relationship is dependent on water salinity, so many recent studies have focused on the Mg/Ca and Sr/Ca ratios because those ratios in water do not change significantly on short time scales. Thus, those elemental ratios are considered to be good palaeotemperature proxies in many biominerals, although their use remains ambiguous in bivalve shells. Here, we present the high-resolution Mg/Ca ratios of two modern species of juvenile and adult oyster shells, Crassostrea gigas and Ostrea edulis. These specimens were grown in controlled conditions for over one year in two different locations. In situ monthly Mn-marking of the shells has been used for day calibration. The daily Mg/Ca.ratios in the shell have been measured with an electron microprobe. The high frequency Mg/Ca variation of all specimens displays good synchronism with lunar cycles, suggesting that tides strongly influence the incorporation of Mg/Ca into the shells. Highly significant correlation coefficients (0.70<R<0.83, p<0.0001) between the Mg/Ca ratios and the seawater temperature are obtained only for juvenile C. gigas samples, while metabolic control of Mg/Ca incorporation and lower shell growth rates preclude the use of the Mg/Ca ratio in adult shells as a palaeothermometer. Data from three juvenile C. gigas shells from the two study sites are selected to establish a relationship: T = 3.77Mg/Ca + 1.88, where T is in degrees C and Mg/Ca in mmol/mol. (c) 2012 Elsevier B.V. All rights reserved.

Botulinum neurotoxin type A blocks the morphological changes induced by chemical stimulation on the presynaptic membrane of Torpedo synaptosomes.

The action of botulinum neurotoxin on acetylcholine release, and on the structural changes at the presynaptic membrane associated with the transmitter release,was studied by using a subcellular fraction of cholinergic nerve terminals (synaptosomes) isolated from the Torpedo electric organ. Acetylcholine and ATP release were continuously monitored by chemiluminescent methods.To catch the membrane morphological changes, the quick-freezing method was applied. Our results show that botulinum neurotoxin inhibits the release of acetylcholine from these isolated nerve terminals in a dose-dependent manner, whereas ATP release is not affected. The maximal inhibition (70%) is achieved at neurotoxin concentrations as low as 125 pM with an incubation time of 6 min. This effect is not linked to an alteration of the integrity of the synaptosomes since, after poisoning by botulinum neurotoxin type A, they show a nonmodified occluded lactate dehydrogenase activity. Moreover, membrane potential is not altered by the toxin with respect to the control, either in resting condition or after potassium depolarization. In addition to acetylcholine release inhibition, botulinum neurotoxin blocks the rearrangement of the presynaptic intramembrane particles induced by potassium stimulation. The action of botulinum neurotoxin suggests that the intramembrane particle rearrangement is related to the acetylcholine secretion induced by potassium stimulation in synaptosomes isolated from the electric organ of Torpedo marmorata.

Liming influence on soil chemical properties, nutritional status and yield of alfalfa grown in acid soil

Alfalfa is an important forage crop with high nutritive value, although highly susceptible to soil acidity. Liming is one of the most efficient and prevailing practices to correct soil acidity and improve alfalfa yield. The objective of this study was to evaluate response to liming of alfalfa grown in a greenhouse on a Typic Quartzipsamment soil. The treatments consisted of four lime rates (0, 3.8, 6.6 and 10.3 Mg ha-1) and two cuts. Alfalfa dry matter increased quadratically with increasing lime rates. In general, dry matter yield was maximized by a lime rate of 8.0 Mg ha-1. Except for the control, the dry matter nutrient contents in the treatments were adequate. The positive linear correlation between root and nodule dry matter with lime rates indicated improvement of these plant traits with decreasing soil acidity. The soil acidity indices pH, base saturation, Ca2+ concentration, Mg2+ concentration, and H + Al were relevant factors in the assessment of alfalfa yield. The magnitude of influence of these soil acidity indices on yield as determined by the coefficient of determination (R²) varied and decreased in the order: base saturation, H + Al, pH, Ca and Mg concentrations. Optimum values of selected soil chemical properties were defined for maximum shoot dry matter; these values can serve as a guideline for alfalfa liming to improve the yield of this forage on acid soils.

Influence of organic-mineral fertilization of an oxisol on soil chemical properties and Bracharia brizantha production

The use of organic-mineral fertilizer produced by the manufacturing industry of lysine and threonine amino acids can improve the fertility of tropical soils. The objective of this study was to evaluate the influence of different doses of the organic-mineral fertilizer named Ajifer L-14 on chemical properties and on the response with increased production of a forage on a Red Latosol in the northwestern region of São Paulo State, Brazil. A randomized block design was used with seven treatments and four replications. The treatments consisted of: T1- control (without application of Ajifer L-14); T2- control (natural vegetation); T3- mineral fertilization according to crop requirements and soil analysis (application of 1.35 kg plot-1 of urea, 2.20 single superphosphate, and 0.51 KCl, corresponding to 60 of N, 40 P2O5 and 30 kg ha-1 of K2O); T4- fertilization with Ajifer L-14 according to the recommendation resulting from the soil chemical analysis (40 L plot-1, corresponding to 60 kg ha-1 N); T5- fertilization with Ajifer L-14, at a rate of 150 % of the recommended values (60 L plot-1, corresponding to 90 kg ha-1 N); T6- fertilization with Ajifer L-14 at a rate of 50 % of the recommended values (20 L plot-1, corresponding to 30 kg ha-1 N); T7- fertilization with Ajifer L-14 at a rate of 125 % of the recommended values (50 L plot-1, corresponding to 75 kg ha-1 N); T8- fertilization with Ajifer L-14 at a rate of 75 % of the recommended values (30 L plot-1, corresponding to 45 kg ha-1 N). The following soil chemical properties were evaluated (layers 0.0-0.1 and 0.1-0.2 m): P, organic matter, pH, K+, Ca2+, Mg2+, cation exchange capacity, potential acidity, and base saturation. The application of this organic-mineral fertilizer does not influence the soil chemical properties. Regression analysis indicated a polynomial relationship between the application rates of organic-mineral fertilizer and the production of dry matter and crude protein of Bracharia Brizantha.

Influence of liming on residual soil respiration and chemical properties in a tropical no-tillage system

Because of the climate changes occurring across the planet, especially global warming, the different forms of agricultural soil use have attracted researchers´ attention. Changes in soil management may influence soil respiration and, consequently, C sequestration. The objectives of this study were to evaluate the long-term influence of liming on soil respiration and correlate it with soil chemical properties after two years of liming in a no-tillage system. A randomized complete block design was used with six replications. The experimental treatments consisted of four lime rates and a control treatment without lime. Two years after liming, soil CO2 emission was measured and the soil sampled (layers 0-5, 5-10, 10-20, and 20-30 cm). The P, Ca2+ e Mg2+ soil contents and pH and base saturation were determined. CO2 emission from soil limed at the recommended rate was 24.1 % higher, and at twice the recommended rate, 47.4 % higher than from unlimed soil. Liming improved the chemical properties, and the linear increase in soil respiration rate correlated positively with the P, Ca2+ and Mg2+ soil contents, pH and base saturation, and negatively with H + Al and Al3+ contents. The correlation coefficient between soil respiration rate and chemical properties was highest in the 10-20 cm layer.

Characterization and nutrient release from silicate rocks and influence on chemical changes in soil

The expansion of Brazilian agriculture has led to a heavy dependence on imported fertilizers to ensure the supply of the growing food demand. This fact has contributed to a growing interest in alternative nutrient sources, such as ground silicate rocks. It is necessary, however, to know the potential of nutrient release and changes these materials can cause in soils. The purpose of this study was to characterize six silicate rocks and evaluate their effects on the chemical properties of treated soil, assessed by chemical extractants after greenhouse incubation. The experimental design consisted of completely randomized plots, in a 3 x 6 factorial scheme, with four replications. The factors were potassium levels (0-control: without silicate rock application; 200; 400; 600 kg ha-1 of K2O), supplied as six silicate rock types (breccia, biotite schist, ultramafic rock, phlogopite schist and two types of mining waste). The chemical, physical and mineralogical properties of the alternative rock fertilizers were characterized. Treatments were applied to a dystrophic Red-Yellow Oxisol (Ferralsol), which was incubated for 100 days, at 70 % (w/w) moisture in 3.7 kg/pots. The soil was evaluated for pH; calcium and magnesium were extracted with KCl 1 mol L-1; potassium, phosphorus and sodium by Mehlich 1; nickel, copper and zinc with DTPA; and the saturation of the cation exchange capacity was calculated for aluminum, calcium, magnesium, potassium, and sodium, and overall base saturation. The alternative fertilizers affected soil chemical properties. Ultramafic rock and Chapada mining byproduct (CMB) were the silicate rocks that most influenced soil pH, while the mining byproduct (MB) led to high K levels. Zinc availability was highest in the treatments with mining byproduct and Cu in soil fertilized with Chapada and mining byproduct.

Concomitant administration of intravenous drugs in the ICU: evaluation of physico-chemical compatibilities

Background and objective: Patients in the ICU often get many intravenous (iv) drugs at the same time. Even with three-lumen central venous catheters, the administration of more than one drug in the same iv line (IVL) is frequently necessary. The objective of this study was to observe how nurses managed to administer these many medications and to evaluate the proportion of two-drugs associations (TDA) that are compatible or not, based on known compatibility data. Design: Observational prospective study over 4 consecutive months. All patients receiving simultaneously more than one drugs in the same IVL (Y-site injection or mixed in the same container) were included. For each patient, all iv drugs were recorded, as well as concentration, infusion solution, location on the IVL system, time, rate and duration of administration. For each association of two or more drugs, compatibility of each drug was checked with each other. Compatibilities between these pairs of drugs were assessed using published data (mainly Trissel LA. Handbook on Injectable Drugs and Trissel's Tables of Physical Compatibility) and visual tests performed in our quality control laboratory. Setting: 34 beds university hospital adult ICU. Main outcome measures: Percentage of compatibilities and incompatibilities between drugs administered in the same IVL. Results: We observed 1,913 associations of drugs administered together in the same IVL, 783 implying only two drugs. The average number of drugs per IVL was 3.1 ± 0.8 (range: 2-9). 83.2% of the drugs were given by continuous infusion, 14.3% by intermittent infusion and 2.5% in bolus. The associations observed allowed to form 8,421 pairs of drugs (71.7% drug-drug and 28.3% drug-solute). According to literature data, 80.2% of the association were considered as compatible and 4.4% incompatible. 15.4% were not interpretable because of different conditions between local practices and those described in the literature (drug concentration, solute, etc.) or because of a lack of data. After laboratory tests performed on the most used drugs (furosemide, KH2PO4, morphine HCl, etc.), the proportion of compatible TDA raised to 85.7%, the incompatible stayed at 4.6% and only 9.7% remain unknown or not interpretable. Conclusions: Nurses managed the administration of iv medications quite well, as only less than 5% of observed TDA were considered as incompatible. But the 10% of TDA with unavailable compatibility data should have been avoided too, since the consequences of their concomitant administration cannot be predictable. For practical reasons, drugs were analysed only by pairs, which constitutes the main limit of this work. The average number of drugs in the same association being three, laboratory tests are currently performed to evaluate some of the most observed three-drugs associations.

Effects of pig slurry application on soil physical and chemical properties and glyphosate mobility

Pig slurry applied to soil at different rates may affect soil properties and the mobility of chemical compounds within the soil. The purpose of this study was to evaluate the effects of rates of pig slurry application in agricultural areas on soil physical and chemical properties and on the mobility of glyphosate through the soil profile. The study was carried out in the 12th year of an experiment with pig slurry applied at rates of 0 (control), 50, 100 and 200 m³ ha-1 yr-1 on a Latossolo Vermelho distrófico (Hapludox) soil. In the control, the quantities of P and K removed by harvested grains were replaced in the next crop cycle. Soil physical properties (bulk density, porosity, texture, and saturated hydraulic conductivity) and chemical properties (organic matter, pH, extractable P, and exchangeable K) were measured. Soil solution samples were collected at depths of 20, 40 and 80 cm using suction lysimeters, and glyphosate concentrations were measured over a 60-day period after slurry application. Soil physical and chemical properties were little affected by the pig slurry applications, but soil pH was reduced and P levels increased in the surface layers. In turn, K levels were increased in sub-surface layers. Glyphosate concentrations tended to decrease over time but were not affected by pig slurry application. The concentrations of glyphosate found in different depths show that the pratice of this application in agricultural soils has the potential for contamination of groundwater, especially when the water table is the surface and heavy rains occur immediately after application.

SOIL CHEMICAL PROPERTIES AND GROWTH OF SUNFLOWER (HELIANTHUS ANNUUS L.) AS AFFECTED BY THE APPLICATION OF ORGANIC FERTILIZERS AND INOCULATION WITH ARBUSCULAR MYCORRHIZAL FUNGI

The use of organic fertilizers and the inoculation of mycorrhizal fungi in the cultivation of oil crops is essential to reduce production costs and minimize negative impacts on natural resources. A field experiment was conducted in an Argissolo Amarelo (Ultisol) with the aim of evaluating the effects of fertilizer application and inoculation of arbuscular mycorrhizal fungi on the growth attributes of sunflower (Helianthus annuus L.) and on soil chemical properties. The experiment was conducted at the Federal University of Rio Grande do Norte, Brazil, using a randomized block design with three replicates in a 4 × 2 factorial arrangement consisting of four treatments in regard to application of organic fertilizer (liquid biofertilizer, cow urine, mineral fertilizer, and unfertilized control) and two treatments in regard to arbuscular mycorrhizal fungi (with and without mycorrhizal fungi). The results showed that the physiological attributes of relative growth rate and leaf weight ratio were positively influenced by fertilization, compared to the control treatment, likely brought about by the supply of nutrients from the fertilizers applied. The growth and productivity attributes were positively affected by mycorrhization.

Chemical and Biochemical Properties of Oxisols after Sewage Sludge Application for 16 Years

ABSTRACT The large production of sewage sludge (SS), especially in large urban centers, has led to the suggestion of using this waste as fertilizer in agriculture. The economic viability of this action is great and contributes to improve the environment by cycling the nutrients present in this waste, including high contents of organic matter and plant nutrients. This study evaluated the chemical and biochemical properties of Dystrophic and EutroferricLatossolos Vermelhos (Oxisols) under corn and after SS application at different rates for 16 years. The field experiment was carried out in Jaboticabal, São Paulo State, Brazil, using a randomized block design with four treatments and five replications. Treatments consisted of control - T1 (mineral fertilization, without SS application), 5 Mg ha-1 SS - T2, 10 Mg ha-1 SS - T3, and 20 Mg ha-1 SS - T4 (dry weight base). The data were submitted to variance analysis and means were compared by the Duncan test at 5 %. Sewage sludge increased P extracted by resin in both theLatossolos Vermelhos, Dystrophic and Eutroferric, and the organic matter content in the Dystrophic Latossolo Vermelho. The waste at the rate 20 Mg ha-1 on a dry weight basis promoted increases in acid phosphatase activity in Eutroferric Latossolo Vermelho, basal respiration and metabolic quotient in DystrophicLatossolo Vermelho. The rate 20 Mg ha-1 sewage sludge on a dry weight basis did not alter the soil microbial biomass in both the Latossolos Vermelhos; in addition, it improved corn yields without inducing any symptoms of phytotoxicity or nutrient deficiency in the plants.

Chemical Functionalization of Bioceramics To Enhance Endothelial Cells Adhesion for Tissue Engineering.

To control the selective adhesion of human endothelial cells and human serum proteins to bioceramics of different compositions, a multifunctional ligand containing a cyclic arginine-glycine-aspartate (RGD) peptide, a tetraethylene glycol spacer, and a gallate moiety was designed, synthesized, and characterized. The binding of this ligand to alumina-based, hydroxyapatite-based, and calcium phosphate-based bioceramics was demonstrated. The conjugation of this ligand to the bioceramics induced a decrease in the nonselective and integrin-selective binding of human serum proteins, whereas the binding and adhesion of human endothelial cells was enhanced, dependent on the particular bioceramics.

Potential influence of the chemical composition of water on the stable oxygen isotope composition of continental ostracods

Many studies in continental areas have successfully used the oxygen isotope composition of fossil ostracod valves to reconstruct past hydrological conditions associated with large changes in climate. Yet, ostracods are known to crystallise their valves out of isotopic equilibrium for oxygen and they generally have higher 18O contents compared to inorganic calcite grown at equilibrium under the same condi- tions. A review of vital offsets determined for continental ostracods indicates that vital offsets might change from site to site, questioning a potential influence of environmental conditions on oxygen isotope fractionation in ostracods. Results from the literature suggest that pH has no influence on ostracod vital offset. A re-evaluation of results from Li and Liu (J Paleolimnol 43:111-120, 2010) suggests that salin- ity may influence oxygen isotope fractionation in ostracods, with lower vital offsets for higher salinities. Such a relationship was also observed for the vital offsets determined by Chivas et al. (The ostracoda- applications in quaternary research. American Geo- physical Union, Washington, DC, 2002). Yet, when results of all studies are compiled, the correlation between vital offsets and salinity is low while the correlation between vital offsets and host water Mg/Ca is higher, suggesting that ionic composition of water and/or relative abundance of major ions may also control oxygen isotope fractionation in ostracods. Lack of data on host water ionic composition for the different studies precludes more detailed examination at this stage. Further studies such as natural or laboratory cultures done under strictly controlled conditions are needed to better understand the potential influence of varying environmental condi- tions on oxygen isotope compositions of ostracod valves.