Polybrominated diphenyl ethers in retail fish and shellfish samples purchased from Canadian markets

Fish and shellfish retail samples (n = 122) were purchased from three Canadian cities in the winter of 2002 and analyzed for a total of 18 polybrominated diphenyl ether (PBDE) congeners. The samples (salmon, trout, tilapia, Arctic char, mussels, oysters, shrimp, and crab) represented the range of fish and shellfish commercially available to Canadian consumers at the time of purchase. Trout and salmon (geometric mean SigmaPBDE = 1600 and 1500 pg/g, wet weight, respectively) were found to contain significantly higher amounts of PBDEs than the mussel, tilapia, and shrimp groups (geometric mean SigmaPBDE = 260, 180, and 48 pg/g, wet weight, respectively). These differences in SigmaPBDE concentrations among fish and shellfish products were partly driven by differences in lipid content among the samples. Mean SigmaPBDE concentrations in domestic samples were also significantly greater than in imported samples, possibly reflecting global environmental distribution of PBDEs. These concentration differences will contribute to variations in dietary exposure to PBDEs when assorted fish and shellfish items from various origins are consumed.     

Isoflavone aglycon and glucoconjugate content of high- and low-soy U.K. foods used in nutritional studies

The isoflavone aglycon and glucoconjugate content of commercially prepared and "home-prepared" high- and low-soy foods selected for use in an on-going nutritional study were measured by LC-MS. The daidzin, daidzein, 6"-O-malonyldaidzin, 6"-O-acetyldaidzin, genistein, genistin, 6"-O-malonylgenistin, 6"-O-acetylgenistin, glycitin, glycitein, 6"-O-malonylglycitin, and 6"-O-acetylglycitin content are expressed in terms of individual isoflavones, total isoflavone equivalents, and milligrams of isoflavones per portion served. Soybeans (774 mg x kg(-1) total isoflavones) and soybean-containing foods had the highest isoflavone content of the foods examined. The low-soy foods all contained very low concentrations (<8 mg x kg(-1) total isoflavones) of the isoflavone aglycons and glucoconjugates. High- and low-soy 11 day rotating menus were constructed from the analyzed foods to deliver 100.0 and 0.5 mg of isoflavones per day, respectively.     

Errors in field measurement of leaf diffusive conductance associated with leaf temperature

The ability of leaf diffusive conductance (C_L) measurements to discriminate between different treatments in field studies has generally been disappointing. Since values of C_L are sensitive to leaf temperature and temperature gradients between the leaf and air, inaccurate temperature measurements will produce substantial errors. This work compared two methods of leaf temperature measurement from which values of C_L were calculated and subsequently compared.Experiments using well-watered field- and glasshouse-grown cotton (Gossypium hirsutum L.) where diffusion porometer readings and leaf temperatures were measured indicated that the porometer thermistor reading differed markedly from leaf temperature as assessed with an infrared thermometer. Under high air vapor pressure deficit (AVPD) conditions (5.2 kPa), leaf temperature (T_L) to ambient air temperature (T_A) differences were as large as ?8°C. Porometer thermistor temperature was strongly influenced by T_A and to a lesser extent by T_L. Values of C_L calculated from porometer measurements of T_L can be up to 96% less than true C_L values. This is the result of both incorrect T_L measurement and a failure to account for the effects of the leaf to porometer-cup temperature differential. Until these two sources of error are addressed, values of C_L obtained from diffusion porometer measurements in the field must be regarded as only qualitative.     

Tallgrass prairie management and bird nest success along roadsides

The attributes of roadside vegetation, an important bird habitat in grassland ecosystems, have been shown to affect bird abundance, distribution composition, and diversity, yet there are relatively few works on reproductive success of birds nesting along roadsides. Because roadsides are linear habitats, management at the landscape scale can affect nest success in roadsides through bottom-up and top-down effects. In northeastern Oklahoma tallgrass prairie is subjected annually to prescribed spring fires. In the short term fires can alter both arthropod abundance and predator access to nests. We explored effects of burning on bird nest success with a five-year study along roads that traversed tallgrass prairie habitat. Using data from ∼1400 nests of 23 species, we generated nest survival curves for groups of altricial species defined by nest substrate (ground, shrub, tree, or culvert). We then determined if these curves were affected by management practice (spring burning), food abundance (arthropod biomass), and habitat attributes (tree density and height). Nest substrate had a large effect on nest success: despite their shorter nest exposure period, ground nests were least successful and culvert nests were most successful. An increase in arthropod biomass following burning was possibly the cause for the increased nest success in burned plots, regardless of substrate, suggesting bottom-up control. Tree height and nest height were correlated positively with nest success, whereas tree density had no effect. Conversely, nest predation rates were correlated negatively with nest success, with ground nests experiencing the highest predation, culvert nests the lowest. Our results suggest that burning may increase nest success through bottom-up processes, but some species may not benefit from the increase in food abundance as a result of a concomitant increase in predation.     

Nutrient dynamics in litter mixtures of four Mediterranean maquis species decomposing in situ

In natural conditions, litters shed from different species become mixed with each other, and decompose together. Most studies deal with decomposition of individual species; few studies investigate the influence of litter mixing on decomposition and nutrient dynamics; the results are contradictory as positive, negative, or no effect, of litter mixing have been observed. In this study we test the hypothesis: i) that litter mixing in the Mediterranean maquis, a nutrient poor, high diversity ecosystem, produces non-additive effects on nutrient dynamics; ii) that the effects vary with the composition in species of the mixture and with the relative amount of the species component the mixture. Two types of 3-species mixtures were set up; one contained three sclerophylls, Phillyrea angustifolia, Pistacia lentiscus and Quercus ilex; the other contained the first two species with the mesophyll Cistus. Litterbags, containing monospecific litters and even and uneven mixtures, were incubated under natural condition in situ; even mixtures had the 3 species in equal proportion, whereas uneven mixtures had one of the species as dominant (50%) and the other two species in equal proportion (25%:25%). Litterbags were retrieved after 92, 188 and 403 days; litters from the mixtures were separately analyzed for mass loss and content of nitrogen (N), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn). Results indicate that mixing influences the dynamics of N, Mn, Ca, Mg, Fe, Cu and Zn, but scarcely affects the dynamics of K and Na. The comparison of observed to expected values for changes of nutrients in litterbags indicates the occurrence of non-additive effects of litter mixing on movements of N, Fe, Cu, and Zn to or from the litterbags containing the mixtures. The effects depend on the composition in species of the mixture, whereas the relative amount of the species component the mixture is not relevant.     

Chromatographic methods for metabolite profiling of virus- and phytoplasma-infected plants of Echinacea purpurea

This study was focused on the effects of virus and phytoplasma infections on the production of Echinacea purpurea (L.) Moench secondary metabolites, such as caffeic acid derivatives, alkamides, and essential oil. The identification of caffeic acid derivatives and alkamides was carried out by means of high-performance liquid chromatography-diode array detection (HPLC-DAD), HPLC-electrospray ionization-mass spectrometry (ESI-MS), and MS(2). Quantitative analysis of these compounds was carried out using HPLC-DAD. The results indicated that the presence of the two pathogens significantly decreases (P < 0.05) the content of cichoric acid, the main caffeic acid derivative. Regarding the main alkamide, dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamide, a significant decrease (P < 0.05) in the content of this secondary metabolite was observed in virus-infected plants in comparison with healthy plants, while in the phytoplasma-infected sample the variation of this secondary metabolite was not appreciable. The % relative area of the E/Z isomers of this alkamide was also found to change in infected samples. The gas chromatography (GC) and GC-MS analysis of E. purpurea essential oil enabled the identification of 30 compounds. The main significant differences (P < 0.05) in the semiquantitative composition were observed for three components: limonene, cis-verbenol, and verbenone. The results indicate that the presence of virus and phytoplasma has an appreciable influence on the content of E. purpurea secondary metabolites, which is an important issue in defining the commercial quality, market value, and therapeutic efficacy of this herbal drug.     

Effect of seawater aerosol on leaves of six plant species potentially useful for ornamental purposes in coastal areas

Aerosol marine strongly affects the growth and development of urban, garden and landscape plants. Few studies have focused on the effects of sodium chloride on plant growth, which is usually applied through irrigation water or substrate media. Even less information is available on the eco-physiological responses of plants to marine aerosol. The aim of this work was to evaluate the physiological responses of different plant species to seawater nebulisation treatments. Plant species that are commonly used along sea fronts were selected as being potentially useful for the study. Plants were bought from a local nursery and included: Acacia cultriformis, Callistemon citrinus, Carissa edulis microphylla, Gaura lindheimeri, Jasminum sambac, Westringia fruticosa. Plants were placed in a randomised block design in a greenhouse and treated for 5 s with seawater or irrigation water (control) using a nebulisation system once every day for 77 days.