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Purpose: To detect carnosine, anserine and homocarnosine in vivo with chemical exchange saturation transfer (CEST) at 17.2 T. Methods: CEST MR acquisitions were performed using a CEST‐linescan sequence developed in‐house and optimized for carnosine detection. In vivo CEST data were collected from three different regions of interest (the lower leg muscle, the olfactory bulb and the neocortex) of eight rats. Results: The CEST effect for carnosine, anserine and homocarnosine was characterized in phantoms, demonstrating the possibility to separate individual contributions by employing high spectral resolution (0.005 ppm) and low CEST saturation power (0.15 μ$$ \mu $$T). The CEST signature of these peptides was evidenced, in vivo, in the rat brain and skeletal muscle. The presence of carnosine and anserine in the muscle was corroborated by in vivo localized spectroscopy (MRS). However, the sensitivity of MRS was insufficient for carnosine and homocarnosine detection in the brain. The absolute amounts of carnosine and derivatives in the investigated tissues were determined by liquid chromatography–electrospray ionization‐tandem mass spectrometry using isotopic dilution standard methods and were in agreement with the CEST results. Conclusion: The robustness of the CEST‐linescan approach and the favorable conditions for CEST at ultra‐high magnetic field allowed the in vivo CEST MR detection of carnosine and related peptides. This approach could be useful to investigate noninvasively the (patho)‐physiological roles of these molecules. [ABSTRACT FROM AUTHOR]

Herbicide drift may cause adverse effects on natural and seminatural plant communities, and it has been debated whether the current ecological risk assessments are adequate to protect nontarget terrestrial plant species. In the present study, 9 nontarget terrestrial plant species with different lifespans (3 annual/6 perennial) belonging to 6 different plant families were exposed to 4 herbicides with different modes of action at the vegetative (6–8 leaf) and reproductive (bud) stages separately. The plant tests were conducted under controlled conditions in 2 greenhouses, 1 located in Denmark and 1 in Canada. For both growth stages, effects were recorded on vegetative (above‐ground biomass 3 wk after treatment) and reproductive endpoints (number and germinability of seeds). In most cases, responses following exposure at the juvenile stage were greater than responses following exposure at the reproductive stage. For the combinations of herbicides and plant species included in the present study, we found that the sensitivities of vegetative and reproductive endpoints were equal, or else vegetative endpoints were more sensitive than reproductive endpoints. We also found that annual species were more sensitive than perennial species. The overall conclusions cover many different response patterns, and it is evident that some effects may not be found in the currently used standard tests. Generally, more pronounced effects were obtained in Denmark compared with Canada, highlighting the fact that even under standardized test conditions and following common guidelines, several uncontrollable factors can still induce variable results. Environ Toxicol Chem 2021;40:1389–1404. © 2021 SETAC [ABSTRACT FROM AUTHOR]

The availability of a benchtop nuclear magnetic resonance (NMR) spectrometer, of low cost and easily transportable, can allow detection of low quantities of biosensors, provided that hyperpolarized species are used. Here we show that the micromolar threshold can easily be reached by employing laser-polarized xenon and cage molecules reversibly hosting it. Indirect detection of caged xenon is made via chemical exchange, using ultra-fast Z spectroscopy based on spatio-temporal encoding. On this non-dedicated low-field spectrometer, several ideas are proposed to improve the signal. [ABSTRACT FROM AUTHOR]

Herbicides have been shown to reduce flower production and to delay flowering, with results varying among herbicides and tested plant species. We investigated the effects of herbicides on flowering in an extensive greenhouse study conducted in Canada and Denmark. The effects of low doses of 5 different herbicides (bromoxynil, ioxynil + bromoxynil, metsulfuron‐methyl, clopyralid, and glyphosate), simulating realistic drift scenarios (1 and 5% recommended field rates), on plant flowering were examined using 9 wild plant species exposed at either the seedling (6‐ to 8‐leaf) or flower bud stage. Following herbicide exposure, initial flowering date as well as flower production over time were recorded over the growing period. The effect of herbicides on cumulative flower numbers and flowering time were modeled using Gompertz growth models. Significant delays to peak flowering and/or reductions in flower production were observed in at least one plant species for all tested herbicides, with glyphosate often exhibiting the greatest negative effects, that is, plant death. Except for ioxynil + bromoxynil, there was no clear evidence of either the seedling or the flower bud stage being more sensitive. Overall, 58% of all species × life stage × herbicide treatments resulted in either a statistically significant or a strong decline in flower production with herbicide application rates up to 5% of recommended field rates, whereas significant or strong delays in peak flowering were also detected but were slightly less common. Effects at 1% label rates were minimal. Simultaneous delays to peak flowering and reductions in total flower production occurred in approximately 25% of all cases, indicating that herbicide application rates simulating realistic drift scenarios would likely have negative effects on wild floral communities. Environ Toxicol Chem 2020;39:1244–1256. © 2020 SETAC [ABSTRACT FROM AUTHOR]

Plant competitive interactions influence the effect of herbicides, and the effect of competitive interactions on plant responses may be important to include in the ecological risk assessment of herbicides. In the present study the effect of competitive interactions and sublethal doses of 2 herbicides on plant species was investigated in competition experiments and fitted to empirical competition models. Two nontarget species commonly found in agroecosystems (Centaurea cyanus L. and Silene noctiflora L.) and 2 herbicides (glyphosate and metsulfuron methyl) were used in separate experiments. Plants were sprayed at the 6‐ to 8‐leaf stage. Effects of herbicide treatments and plant density were modeled by generalization of a discrete hyperbolic competition model. The 10% effective dose (ED10) was calculated for C. cyanus. All experiments showed that as density increased, plants were negatively affected. Furthermore, in all cases, C. cyanus remained a better competitor than S. noctiflora. Nevertheless, the density of S. noctiflora (competitor) was an influential element in determining the ED10 of C. cyanus measured at the mature stage. With herbicide exposure, the competitive interactions were further altered; C. cyanus was less affected by glyphosate when S. noctiflora increased to high density. In contrast, at the young stage, conspecific density was important in determining the sensitivity of C. cyanus to metsulfuron methyl, whereas the density of the competitor S. noctiflora had a limited influence. Overall, the results demonstrate the importance of integrating the effect of herbicide and species interactions measured at the reproductive stage into the ecological risk assessments of pesticides. Environ Toxicol Chem 2019;38:2053–2064. © 2019 SETAC. [ABSTRACT FROM AUTHOR]

Questions Do agricultural land use and nitrogen (N) enrichment have negative effects on riparian soil seed banks? What is the potential of the soil seed bank for the conservation and restoration of native riparian plant diversity? Are non-native dominant grass species affected by agriculture and do they affect species richness? Location South Nation River watershed (an agricultural watershed), Ontario, Canada. Methods We examined the riparian above-ground vegetation at 24 sites located across a large (~4000 km2) North American watershed and identified the corresponding soil seed bank composition from soil cores using the seedling emergence method. The above-ground vegetation and soil seed bank species compositions were compared in terms of species richness, percentage of non-native species and a floristic quality index. Factors affecting these descriptors of plants communities (concentration of in-stream nitrate and percentages of surrounding natural habitat and annual crop land) were assessed. The effects of agriculture on two dominant non-native grasses species and their effects on species richness were also assessed. Results In total, 274 plant taxa were identified, including 181 taxa in the soil seed bank and 231 taxa in the vegetation. Overall species richness was high in both the soil seed bank and above-ground vegetation and was unaffected by measures of agricultural intensity (surrounding annual crop land and N enrichment). Above-ground vegetation species richness was strongly negatively affected by the widespread and dominant non-native grasses, Phalaris arundinacea and Bromus inermis, whereas soil seed bank species richness was unaffected. The community compositions of both the soil seed bank and vegetation were negatively affected by the loss of natural habitat and by N enrichment. In fact, an increase in the percentage of non-native species and a decrease in floristic quality were observed along a gradient of agricultural intensity. Conclusions Species richness of the soil seed bank demonstrated resilience to invasions by P. arundinacea and B. inermis, and the soil seed bank showed good potential for conservation of taxonomic diversity. However, the loss of natural habitat and N enrichment had negative effects on the soil seed bank community composition that may lead to an eventual decline in above-ground species richness. [ABSTRACT FROM AUTHOR]

Questions: Plant community resilience largely depends on the secondary succession induced by species re-colonization from seed banks. Soil seed bank resilience is, however, poorly understood, especially in regularly disturbed habitats like riparian zones. Two questions were asked: (1) what are the changes in species diversity experienced by riparian soil seed banks along successional trajectories, and (2) to what extent do riparian soil seed banks promote vegetation resilience during secondary succession? Location: Southeast Quebec, Canada. Methods: Soils were collected along five rivers in field edges and riverbanks of post-agricultural riparian zones with three contrasting successional stages (unplanted, planted with trees 15-17 yr prior to sampling, natural riparian forests), and their seed bank composition determined with the seedling emergence method. Species richness in seed banks was assessed along successional trajectories for distinct ecological groups, using LMM. The compositions of soil seed banks and standing vegetation (from botanical surveys) were compared based on NMDS and indicator species analysis. Results: Seed bank species richness decreased along successional trajectories. Tree-planted riparian zones were generally closer to unplanted riparian zones than to natural riparian forests, the latter being more species-rich for natives, trees, shrubs and zoochores, and species-poor for exotics, forbs and stress-tolerators. Likewise, seed bank species composition of unplanted and tree-planted riparian zones was similar but differed from that of natural riparian forests. Conversely, standing vegetation of tree-planted riparian zones was intermediate between early and late successional stages, at least at field edges. For the three successional stages, seed bank composition clearly differed from standing vegetation. Conclusions: The high resilience of riparian plant communities appeared poorly related to the dynamics of their soil seed banks. This species shift between seed banks and standing vegetation during secondary succession is likely due to periodic flooding, leading to the regular turnover of seeds. The resilience of riparian communities might thus be more influenced by spatial dispersal along rivers and across landscapes than by in situ temporal dispersal in soils. [ABSTRACT FROM AUTHOR]

In agricultural catchments, streams are intimately connected with croplands and are exposed to agrochemicals such as fertilisers and herbicides. In North American streams, the effects of nutrient enrichment on riparian and aquatic plant community structure are not well established and the effects of herbicides are largely unknown., We identified the riparian and aquatic plant community at 12 paired stream/river sites (24 in total, Strahler stream order 3-6) located across a large North American agricultural catchment. Field sites ranged in surrounding agricultural land use (2.7-100% annual crops) and in-stream June concentrations of reactive phosphate (6-65 μg L−1 as phosphorus) and nitrate (3-3981 μg L−1 as nitrogen). Atrazine, a herbicide commonly used on corn crops in North America, was widespread throughout the catchment with time-weighted-average concentrations ranging from 4 to 412 ng L−1 over a 56-day period. Atrazine concentrations were >100 ng L−1 at over half the field sites., In total, 285 riparian and aquatic plant taxa were identified. Effects of agrochemicals on descriptors of plant communities were assessed by comparing paired sites surrounded by low or high levels of agriculture and examining changes across the catchment. Agrochemicals had no effect on overall species richness. However, the percentage of non-native species increased across the catchment along a gradient of increasing nitrate. A decline in submerged macrophytes was associated with enrichment of both nitrate and reactive phosphate, whereas no direct effects of atrazine were observed., A floristic quality assessment was used to determine further effects of agrochemicals on riparian and aquatic plant communities. A ranking system, based on native status and tolerance to disturbance, was used to assign coefficient of conservation values to each species. Floristic quality was subsequently calculated as a function of species richness and the average coefficient of conservation value at each site. Overall floristic quality decreased as nitrate increased. Species positively associated with nitrate were typically fast-growing, weedy, riparian species, whereas species negatively associated with nitrate were characteristic of less disturbed areas and represented a range of growth forms., We conclude that nutrient enrichment, especially of nitrate, has multiple negative effects on riparian and aquatic plant communities that override effects of the herbicide atrazine. Our results highlight the need to reduce inputs of agrochemicals to streams and to regulate nitrogen in addition to phosphorus. [ABSTRACT FROM AUTHOR]

The decline of arable species characteristic of winter cereal fields has often been attributed to different factors related to agricultural intensification but most importantly to herbicide use. Herbicide phytotoxicity is most frequently assessed using short-term endpoints, primarily aboveground biomass. However, short-term sensitivity is usually not sufficient to detect actual effects because plants may or may not recover over time following sublethal herbicide exposures. Therefore, it is important to assess the long-term effects of herbicide applications. Annual species rely on renewable seed production to ensure their persistence; hence, assessment of herbicide sensitivity is more accurately estimated through effects on reproduction. Here we aim to assess the phytotoxicity of two commonly used herbicides: tribenuron and 2,4-D on eight plant species belonging to four families, each with one rare and one more common species. Specifically we examined the pattern of sensitivity using short-term and long-term endpoints (total aboveground biomass, total seed biomass and number of seeds) of these species; we determined the levels of and time to recovery in terms of stem length and fruit number, and assessed whether their rarity relates to their sensitivity to herbicide application. Our results suggest that although differences in herbicide sensitivity are not a direct cause of rarity for all species, it may be an important driver of declining arable plants. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) have become increasingly important metals used in modern technology. Processes including mining, oil refining, discarding of obsolete equipment containing REEs, and the use of REE-containing phosphate fertilizers may increase the likelihood of environmental contamination. However, there is a scarcity of information on the toxicity and accumulation of these metals to terrestrial primary producers in contaminated soils. The objective of this work was to assess the phytotoxicity and uptake from contaminated soil of six REEs (chloride forms of praseodymium, neodymium, samarium, terbium, dysprosium, and erbium) on three native plants (Asclepias syriaca L., Desmodium canadense (L.) DC., Panicum virgatum L.) and two crop species (Raphanus sativus L., Solanum lycopersicum L.) in separate dose-response experiments under growth chamber conditions. Limited effects of REEs were found on seed germination and speed of germination. Effects on aboveground and belowground biomass were more pronounced, especially for the three native species, which were always more sensitive than the crop species tested. Inhibition concentrations (IC25 and IC50) causing 25 or 50% reductions in plant biomass respectively, were measured. For the native species, the majority of aboveground biomass IC25s (11 out of 18) fell within 100 to 300 mg REE/kg dry soil. In comparison to the native species, IC25s for the crops were always greater than 400 mg REE/kg, with the majority of results (seven out of 12) falling above 700 mg REE/kg. IC50s were often not detected for the crops. Root biomass of native species was also affected at lower doses than in crops. REE uptake by plants was higher in the belowground parts than in the above-ground plant tissues. Results also revealed that chloride may have contributed to the sensitivity of the native species, Desmodium canadense, one of the most sensitive species studied. Nevertheless, these results demonstrated that phytotoxicity may be a concern in contaminated areas. [ABSTRACT FROM AUTHOR]

Copyright of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Capping of cyclotriphenolene (3a) by the more available cyclo-triguaiacylene (3c) or trisbromocyclotriphenolene (3b) gives the first rim-functionalized cryptophane-111 derivatives. Crystal structures of the xenon complexes reveal high cavity packing coeffi- cients and unprecedentedly short Xe...C contacts. [ABSTRACT FROM AUTHOR]

Gaining an understanding of the nature of host-guest interactions in supramolecular complexes involving heavy atoms is a difficult task. Described herein is a robust simulation method applied to complexes between xenon and members of a cryptophane family. The calculated chemical shift of xenon caged in a H2O2 probe, as modeled by quantum chemistry with complementary-orbital, topological, and energy-decomposition analyses, is in excellent agreement with that observed in hyperpolarized 129Xe NMR spectra. This approach can be extended to other van der Waals complexes involving heavy atoms. [ABSTRACT FROM AUTHOR]

Gaining an understanding of the nature of host-guest interactions in supramolecular complexes involving heavy atoms is a difficult task. Described herein is a robust simulation method applied to complexes between xenon and members of a cryptophane family. The calculated chemical shift of xenon caged in a H2O2 probe, as modeled by quantum chemistry with complementary-orbital, topological, and energy-decomposition analyses, is in excellent agreement with that observed in hyperpolarized 129Xe NMR spectra. This approach can be extended to other van der Waals complexes involving heavy atoms. [ABSTRACT FROM AUTHOR]

We studied landscape dynamics for three time periods (<1950, 1965, and 1997) along a gradient of agricultural intensity from highly intensive agriculture to forested areas in southern Québec. Air photos were analyzed to obtain long-term information on land cover (crop and habitat types) and linear habitats (hedgerows and riparian habitats) and landscape metrics were calculated to quantify changes in habitat configuration. Anthropogenic areas increased in all types of landscapes but mostly occurred in the highly disturbed cash crop dominated landscape. Perennial crops (pasture and hayfields) were largely converted into annual crops (corn and soybean) between 1965 and 1997. The coalescence of annual crop fields resulted in a more homogeneous agricultural landscape. Old fields and forest cover was consistently low and forest fragmentation remained stable through time in the intensive agriculture landscapes. However, forest cover increased and forest fragmentation receded in the forest-dominated landscapes following farm abandonment and the transition of old fields into forests. Tree-dominated hedgerows and riparian habitats increased in areas with intensive agriculture. Observed changes in land cover classes are related to proximate factors, such as surficial deposits and topography. Agriculture intensification occurred in areas highly suitable for agriculture whereas farm abandonment was observed in poor-quality agriculture terrains. Large-scale conversion of perennial crops into annual crops along with continued urbanization exerts strong pressures on residual natural habitats and their inhabiting wildlife. The afforestation process occurring in the more forested landscapes along with the addition of tree-dominated hedgerows and riparian habitats in the agriculture-dominated landscapes should improve landscape ecological value. [ABSTRACT FROM AUTHOR]

Current regulatory protocols for assessing herbicide effects on plants rely heavily on the use of crops grown under controlled greenhouse conditions to indicate risks to wild vegetation. Guideline test protocols call for low levels of soil nutrients, approximately 3 % organic matter (OM), to test the worst-case scenario for non-target species growing in poor soils. However, species sensitivity to herbicides may be affected by growing conditions, especially soil nutrient levels. The purpose of this study was to assess the impact of high and low soil OM content on the sensitivity of plants to several common agricultural herbicides (glyphosate, chlorimuron ethyl and dicamba). Ten plant species (wild and crop) with high (nitrophilous) or low (non-nitrophilous) affinity for nitrogen were grown under greenhouse conditions in soil with two levels of OM (3 and 9 %) and were exposed to seven doses of the three herbicides in concurrent experiments. Results showed that most species were more sensitive to glyphosate under high OM conditions while chlorimuron ethyl and dicamba results were mixed with respect to OM levels. Overall, 15 species-herbicide combinations were more sensitive in high OM soil, while 11 were more sensitive in low OM soil. No clear pattern in sensitivity emerged among nitrophilous and non-nitrophilous species. Several species showed a difference in response at herbicide levels expected to reach non-target habitats adjacent to crop fields through drift (5 % commonly and 25 % occasionally). In terms of regulatory testing, guidelines may need alteration to allow testing with nutrient levels that more accurately reflect natural environments. [ABSTRACT FROM AUTHOR]

Background: Few studies have focused on the social inequalities associated with environmental noise despite its significant potential health effects. This study analysed the associations between area socio-economic status (SES) and potential residential exposure to road traffic noise at a small-area level in Marseilles, second largest city in France. Methods: We calculated two potential road noise exposure indicators (PNEI) at the census block level (for 24-h and night periods), with the noise propagation prediction model CadnaA. We built a deprivation index from census data to estimate SES at the census block level. Locally estimated scatterplot smoothing diagrams described the associations between this index and PNEIs. Since the extent to which coefficient values vary between standard regression models and spatial methods are sensitive to the specific spatial model, we analysed these associations further with various regression models controlling for spatial autocorrelation and conducted sensitivity analyses with different spatial weight matrices. Results: We observed a non-linear relation between the PNEIs and the deprivation index: exposure levels were highest in the intermediate categories. All the spatial models led to a better fit and more or less pronounced reductions of the regression coefficients; the shape of the relations nonetheless remained the same. Conclusion: Finding the highest noise exposure in midlevel deprivation areas was unexpected, given the general literature on environmental inequalities. It highlights the need to study the diversity of the patterns of environmental inequalities across various economic, social and cultural contexts. Comparative studies of environmental inequalities are needed, between regions and countries, for noise and other pollutants. [ABSTRACT FROM PUBLISHER]

We describe the synthesis of a highly water-soluble cryptophane 1 that can be seen as a universal platform for the construction of 129Xe magnetic resonance imaging (MRI)-based biosensors. Compound 1 is easily functionalized by Huisgen cycloaddition and exhibits excellent xenon-encapsulation properties. In addition, 1 is nontoxic at the concentrations typically used for hyperpolarized 129Xe MRI. [ABSTRACT FROM AUTHOR]

The objectives of this study were to compare the sensitivities of field populations and a laboratory culture of a duckweed species ( Lemna minor) to the herbicide atrazine using three different endpoints and to determine whether sensitivity to atrazine was affected by past exposure to the herbicide. L. minor cultures were purchased commercially or collected from field sites within an agricultural watershed and exposed to atrazine for 7 days under greenhouse conditions. Populations differed significantly in their sensitivity to atrazine. Biomass was more sensitive than frond number, while chlorophyll fluorescence was not a sensitive endpoint. Overall, the sensitivity of the various populations to atrazine was not strongly related to measures of past exposure to agriculture stressors. Positive correlations between biomass twenty-five percent inhibition concentrations (ICs), biomass estimated marginal means and in-stream atrazine concentrations were observed, providing evidence that atrazine exposure is linked to a decrease in sensitivity to atrazine. However, ICs generated for each population were similar, ranging from 19 to 40 and 57 to 92 μg/L atrazine for biomass and frond data respectively, and likely do not represent biologically significant differences in atrazine sensitivity. Given the small range in sensitivity observed between populations, commercial laboratory cultures appear to provide a good estimate of the sensitivity of field populations of L. minor to atrazine and should continue to be used in regulatory phytotoxicity testing. [ABSTRACT FROM AUTHOR]

Vanadium concentrations in soil can be increased through anthropogenic inputs and can be harmful to plants. A Petri dish experiment was conducted to assess the effect of vanadium toxicity on the germination and survival of the garden lettuce, Lactuca sativa. A second study was conducted in a greenhouse to investigate the influence of species selection and nutrient concentration on the toxicity of vanadium pentoxide to plants. L. sativa and four non-crop native plant species, two grasses ( Elymus virginicus and Panicum virgatum) and two broad-leaved species ( Lycopus americanus and Prunella vulgaris) were selected. Artificial soil was used in both experiments, and a geometric progression of five vanadium concentrations plus controls was selected for the soil treatments. Results of the Petri dish experiment showed that seedling survival is a less sensitive end point than above-ground dry weight (DW) as measured in the greenhouse experiment. Nutrient level (100, 10, and 1 kg/ha) was found to strongly influence vanadium toxicity in the greenhouse study. At 100 kg/ha, plant tolerance to vanadium was greatest, as indicated by higher no-observed, lowest-observed, and percentage effect concentration values. Results showed that forbs ( L. americanus and P. vulgaris) tended to be more sensitive than both the crop ( L. sativa) and grasses ( E. virginicus and P. virgatum) at high concentrations of vanadium. Soil concentrations resulting in a 25 % decrease in shoot DW were generally less than the Canadian soil quality guideline for vanadium, suggesting that 130 mg/kg may not be protective of the Canadian native plant species used in this study. [ABSTRACT FROM AUTHOR]

We show that the differentiation between internal and external compartments of various biological cells in suspension can be made via simple NMR spectra of hyperpolarized 129Xe. The spectral separation between the signals of 129Xe in these two compartments is already known for red blood cells, because of the strong interaction of the noble gas with hemoglobin. The observation of two separate peaks in the 200-ppm region can be seen with both eukaryotic and prokaryotic cells, some of which are not known to contain paramagnetic proteins in large quantities. Using different experiments in which the cells are lysed, swell or are blocked in G2 phase, we demonstrate that the low-field-shifted peak observed corresponds to xenon in the aqueous pool inside the cells and not in the membranes. The presence of this additional peak is a clear indication of cell integrity, and its integration allows the quantification of the total cell volume. The relaxation time of intracellular xenon is sufficiently long to open up promising perspectives for cell characterization. The exchange time between the inner and outer cell compartments (on the order of 30 ms) renders possible the targeting of intracellular receptors, whereas the observation of chemical shift variations represents a method of revealing the presence of toxic species in the cells. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The unique plant community on Middle Island, Lake Erie, Canada, has been greatly modified by double-crested cormorants ( Phalacrocorax auritus Less.) whose population has increased enormously in the last two decades. The aims of this study were to assess the impact of cormorants on island tree canopy, understorey vegetation, soil seedbank, and soil chemistry. The ultimate objective was to assess the resilience of the vegetation community for recovery should cormorant nest densities decrease significantly. Forty-three point stations were established in a grid system covering the entire island. The herbaceous and woody vegetation was surveyed over 2 years and tree crown damage was assessed at each point station. In 2008, soil samples were collected for both chemical analysis and a seedbank inventory. Vegetation and seedbank species richness were impoverished compared to the vegetation surveyed prior to cormorant colonization. Cormorants affected not only the tree canopy where they nested but also the understorey vegetation. Exotic plant species were very common in the standing vegetation and constituted the bulk of the abundance in the seedbank. However, there was little relationship between aboveground vegetation and seedbank composition. Cormorants appeared to have little influence on seedbank richness, abundance, and composition. Notably, several species of conservation interest were found in the aboveground vegetation and in the seedbank providing a positive sign for future efforts to restore island plant communities. [ABSTRACT FROM AUTHOR]

Intensification of agriculture and the corresponding increase in herbicide use has led to concern regarding the effects these chemicals may have on nontarget plants of agroecosystems. Current pesticide registration guidelines are focused on testing crop species grown singly in pots under greenhouse conditions and may not provide adequate measures of protection to noncrop species. The objective of the present study was to compare the response of terrestrial and wetland plants to the herbicides glyphosate and atrazine when grown singly in pots versus under different microcosm conditions. Greenhouse microcosms were generally more sensitive than single-species tests. Plants grown for an extended test period or in seminatural field conditions were generally less sensitive to herbicides. Sensitivity was found to be dependent on interactions between species and test conditions. Changes in community structure were observed in herbicide-treated microcosms that would not be predicted from single-species testing. Single-species tests are useful because they are inexpensive, can demonstrate clear dose-response patterns uncomplicated by other factors influencing growth, and are able to provide a measure of the sensitivity of a given species to glyphosate and atrazine. However, they are unable to predict subtle changes in community structure that may have important long-term consequences. Environ. Toxicol. Chem. 2010;29:2304-2315. © 2010 SETAC [ABSTRACT FROM AUTHOR]

Current guidelines for phytotoxicity testing rely heavily on short-term testing of primarily crop species to predict the sensitivity of non-target, wild plants to herbicides. However, little is known on how plants recover following initial growth inhibitions in standard 14-28 day greenhouse tests conducted for pesticide assessment and registration. The objectives of this study were to assess the ability of plant species to recover (biomass and reproduction) when tested at the juvenile stage (routine regulatory testing), comparing crop and wild species and using the herbicide glufosinate ammonium. Ten crops and 10 wild species were tested with a one-time exposure to glufosinate ammonium in a greenhouse. Half the plants of each species (9 doses × 6 replicates) were harvested 3 weeks after being sprayed (short-term). The remaining plants were harvested several weeks later, coinciding with seed set or natural senescence (long-term). Total aboveground biomass and several endpoints related to crop production and plant reproduction were measured. Calculated IC50 values (dosage that results in a 50% decrease in the biomass of a plant as compared to the untreated controls) based solely on aboveground biomass, for species harvested in the long-term were generally higher than those obtained in the short-term (with two exceptions), indicating recovery over time. Crop species did not differ from wild species in terms of sensitivity. However, in seven out of 12 cases where reproduction was measurable, reproductive endpoints were more sensitive than either short or long-term biomass endpoints, indicating the importance of examining these parameters in phytotoxicity testing. Glufosinate ammonium was found to be phytotoxic at low doses (2.64-7.74% g ai/ha of the label rate). [ABSTRACT FROM AUTHOR]

A series of experiments was conducted to assess the level of variability in phytotoxicity testing and to investigate factors that may explain some of the observed uncertainties and inconsistencies. The work was conducted in greenhouse or growth chamber environments with plants growing individually in pots and harvested 28 d after spraying with two herbicides, glyphosate and atrazine, as formulated products. Between six and 10 doses were used on five or six replicates, necessitating over 4,500 individually growing plants. In the first set of experiments, several ecotypes (originating from different areas of the world) of eight wild plant species were tested. Significant differences in sensitivity to atrazine and glyphosate were found among ecotypes of most species tested. In the second suite of experiments, the reproducibility of results during different seasons (when growing conditions vary) was investigated using three crops and four wild plant species. Results showed that seasonal variability elicited a pronounced discrepancy in response between plants tested at different times of the year. It was found that no consistent effects could be attributed to the biotic or abiotic factors investigated. Several ecotypes of the same species differed in their seed size, percentage germination, or germination requirements, as well as in growth patterns, but these differences could not explain differences in herbicide sensitivity. Likewise, differences in phytotoxicity could not be attributed to factors such as temperature, light intensity, and sunlight duration. The present study supports the inclusion of an uncertainty factor in risk assessments to account for the intrinsic variability in plant sensitivity to herbicides. Environ. Toxicol. Chem. 2010;29:327–337. © 2009 SETAC [ABSTRACT FROM AUTHOR]

The article presents the optimum germination requirements for 29 terrestrial and wetland wild plant species that are appropriate for phytotoxicity testing. The authors report that all plant species achieved 50% germination and 23 reached >70% germination. The result means that the plant species are able to meet the criterion outlined in the Organisation for Economic Co-operation and Development (OECD) guidelines. Additionally, most plant species attained their maximum germination within 14 days or less.

Fluorescence correlation spectroscopy (FCS) has been used to analyze the plasma membrane fluidity and heterogeneity of multidrug resistant cells. At the single cell level, the effects of different membrane agents present in the extra-cellular medium have been explored. Firstly, we reveal a modification of plasma membrane heterogeneities according to the addition of a fluidity modulator, benzyl alcohol. On the other hand, revertants such as verapamil and cyclosporin-A appear to act more specifically on the slow diffusion sites, such as lipids microdomains. [ABSTRACT FROM AUTHOR]

The impact of herbicide exposure on nontarget vegetation within agroecosystems has sparked extensive research that revealed that current pesticide registration guidelines may be inadequate at predicting the effects of herbicides on wild plants and habitats. This study extends the current interest by presenting three experiments highlighting some of the limitations to current phytotoxicity testing guidelines. Several crops and wild plant species were grown under greenhouse conditions following standard protocol for phytotoxicity testing. Plants were sprayed with five different herbicides at the four-to six-leaf stage, and biomass was recorded at 28 d after spray. Results showed that current regulatory protocol will likely underestimate herbicide phytotoxicity if testing does not include data for the complete tank-mix formulation. The present study also showed that the range in herbicide sensitivity among cultivars of the same crop can be quite extensive and that, depending on the cultivar included in a risk assessment, conclusions regarding the phytotoxicity of any given herbicide may differ. Although no significant differences in sensitivity were found between crops and related wild species, results revealed that current guidelines are too rigid in terms of species selection. Considering the variability among crop cultivars, coupled with the ecological importance and the ease of germination of many noncrop plant species, pesticide regulatory guidelines would be improved if wild species were included in testing. Findings of the present study indicate that current pesticide regulatory guidelines require modifications to ensure a more accurate assessment of herbicide effects on nontarget plant species. [ABSTRACT FROM AUTHOR]

Focuses on research which studied the effects of glyphosate and seed germination. How several studies reporting detrimental effects of the herbicide on seedling germination and growth, glyphosate is still being registered for use as a weed killer and preharvest desiccant. Effect of its nonselective nature and low chance of species developing resistance has lead to the development of genetically modified crops tolerant to the herbicide which also raises concerns about increased reliance on herbicide use, and subtle ecological impact.

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Presents a study to compare the value of these habitats as a repository of plant biodiversity in agricultural areas of southern Quebec, Canada. Status of the overall plant diversity in natural hedgerows; How they contained more plant species of conservation values than other hedgerow types; Consideration of natural woody, planted woody and herbaceous plants; Suggestion that management practices should optimize the growth of establishing plants of conservation values.

Two extensive databases were used to examine the pattern of species sensitivities to pesticides. The first database consisted of industry-sponsored data collated over several years by the Canadian regulatory authority (data on weed efficacy and crop margin of safety). The second dataset consisted of data submitted to the United States Environmental Protection Agency (U.S. EPA). On the whole we found that crop species were not consistently more, or less, sensitive to the herbicide tested than non-crop species. Within the Poaceae family (grasses), however, non-crop species exhibited higher sensitivity in 15 cases (out of 23), and only in five cases were crops more sensitive. The range of species sensitivity increases with an augmentation of numbers of species tested, suggesting that the number of species tested in current guidelines is insufficient. Principal Component Analyses showed that only two groups of species could be separated; in both databases, grass and broad-leaved species formed two distinct groups. Correlations between species demonstrated a relationship when comparing within genera or within families. The distribution-based method used with the Canadian database ascertained further the importance of testing more or other species than those recommended in the U.S. EPA guidelines. We concluded that, given the limitations of the current databases, further analyses could not be carried out. We suggest that an improved database on phytotoxicity is a prerequisite to refine the risk assessment of pesticide effects of non-target plants. [ABSTRACT FROM AUTHOR]

Compares the population dynamics of three annual species of Veronica (V arvensis, V. hederifolia, and V. persica) and two perennial species (V. serpyllifolia and V. chamaedrys) in six sites in which one or more of the species grew naturally. Differences in times and rates of germination; Flowering in V. arvensis and V. hederifolia.

The approach developed by Environment Canada to assess risk to aquatic and terrestrial plants in nontarget habitats potentially exposed to pesticides evaluated for registration is described. An anonymous sample of pesticide submissions is used to illustrate the approach and to examine its merits and limitations in relation to test species, response variability, testing protocols, ecological relevance, and comparability with other regulatory agencies. Future directions are identified, particularly in relation to impending nontarget-plant testing guidelines for pesticide registration in Canada. This approach incorporates some of the latest research and developments in the field of risk assessment for plants. The novelty of this approach also lies in the use of the plant screening data routinely generated by chemical pesticide companies, which is intended to provide a maximum amount of information to evaluators at minimal increment cost to registrants. The proposed approach can serve as a basis for guideline development and modernization for other jurisdictions. [ABSTRACT FROM AUTHOR]

Cryptophane-111 is one of the best candidates for 129Xe MRI-based applications. Herein, we report the first metal-free and water-soluble cryptophane-111 core which involves an efficient and unusual post-synthetic sulfonation procedure. [ABSTRACT FROM AUTHOR]

Current methods to estimate exposure of wildlife to pesticides from diet depend on a database of published residue concentrations on crop plants normalized to a standard application rate to obtain a residue from a unit dosage (RUD). This database, first published in the early 1970s, was updated in the 1990s. For each category of crops, maximum and mean residues are determined and used to extrapolate concentrations on plants across application rates in calculations of risk. The present study aims to update the database, to examine the validity of extrapolating RUD values across application rates, and to improve the categorization of crops using crop morphology and cultivation methods. The slope of the linear regression of residue concentrations against application rate in 41 trials was significantly different from one in all but five cases. This supports the assumption that residue concentrations are directly proportional to the application rate, although less than half the variance in residue concentrations was explained by the linear model. Residues on leaves were partitioned into eight categories of crops using information regarding plant morphology and cultivation method. Fruit size was an additional variable useful for segregating residues into four categories: Small fruits, large fruits, pods, and grains. The proposed changes increase the amount of variance explained in the residue database from 19 to 32%. Depending on the crop category, residues on fruits were 2- to 16-fold lower than those on leaves. Residue concentrations on leaves of short plants were more than fourfold higher than those on leaves of tall plants. Descriptive statistics are provided for each of the proposed crop categories. [ABSTRACT FROM AUTHOR]