Chlorantraniliprole and novaluron, two reduced-risk insecticides (IRRs), are currently used to control codling moth (Cydia pomonella) in apple orchards in southeastern Canada. Reproduction of Harmonia axyridis (Pallas), an invasive ladybeetle, and the indigenous Coleomegilla maculata DeGeer, both important generalist predators, might be compromised after exposure of adults to these IRRs. The aim of the study was to compare the effects of chlorantraniliprole and novaluron on fecundity and fertility between the two ladybeetles in a laboratory setting. Reproductive mates were given chlorantraniliprole- or novaluron-treated prey for 24 h, and reproductive performance was followed during 15 days. Chlorantraniliprole did not affect reproduction of ladybeetles. However, novaluron-reduced fecundity, egg hatch, and fertility of the invasive ladybeetle H. axyridis, by 29, 43, and 78.7%, respectively, contrasting with no significant effect on the indigenous C. maculata. Additionally, H. axyridis oviposition pattern was altered by the same insecticide. This resulted in more egg masses containing fewer eggs, compared to the control. No such changes were detected for C. maculata. Chlorantraniliprole does not disturb reproduction of H. axyridis or C. maculata. Treatments of novaluron should have an important effect on populations of the invasive H. axyridis, and consequently on the impact of the invader on native ladybeetle species and on its dominance, and finally potentially on biocontrol services provided by the assemblage of ladybeetles.
The tomato (Solanum lycopersicum L.) cultivar Micro‐Tom (MT) is widely used in physiological studies, but the effects of nitrate ( ) and ammonium ( ) ratios ( : ratios) and, in particular, the effects of the accompanying ions in sources are unknown. To determine whether the accompanying ions in sources influence toxicity, the effects of : ratios on the physiology, electrolyte leakage index, nutrition, and dry weight were studied using hydroponics. The sources were ammonium chloride (NH4Cl) or ammonium sulfate [(NH4)2SO4], and five : ratios were used: 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. The source was calcium nitrate [Ca(NO3)2], and the nitrogen (N) concentration was 15 mmol L?1. The results indicate that NH4Cl or (NH4)2SO4 can be used in studies on toxicity because the accompanying ions did not influence the tomato plants. In addition, : ratios of 100 : 0 and 75 : 25 resulted in the highest dry weight of tomato plants, whereas ratios of 25 : 75 or 0 : 100 were toxic. 相似文献
The objectives of this study were (1) to determine the concentrations and background concentrations of Ba, Co, Cr, Mn, and Ni in the urban soils of Talcahuano (Chile); (2) assess the level of contamination in the urban soils based on different pollution indexes; and (3) to identify natural or anthropogenic sources in order to obtain a spatial distribution of the pollutants.
Material and methods
A total of 420 samples were collected from the study area as follows: 140 topsoil samples (TS) (0–10 cm), 140 subsoil samples (SS) (10–20 cm), and 140 deep soil samples (DS) (150 cm). The soils were characterized, and the concentrations of Ba, Co, Cr, Mn, and Ni were analyzed by atomic absorption photospectrometry following aqua regia digestion. Correlations and principal component analysis combined with spatial analysis were implemented in order to distinguish the sources and their classification as geogenic or anthropogenic. Several simple and robust statistical methods were applied to datasets in order to explore their potential in the evaluation of a useful and robust background values. The degree of contamination along with the geoaccumulation index, enrichment factor, and contamination factor were also evaluated.
Results and discussion
The median concentrations obtained for various elements includes Ba 461 mg kg?1, Co 82.7 mg kg?1, Cr 134 mg kg?1, Mn 311 mg kg?1, and Ni 56.1 mg kg?1. In general, the concentrations of Ba, Co, Cr, Mn, and Ni decrease with depth. Correlations and principal component analysis suggest that Cr, Mn, and Ni are contributed by external sources. The spatial distribution of Cr, Mn, and Ni in TS displays a spatial pattern extending along industrial environments and emission sources.
Conclusions
The estimated background values determined with the iterative 2σ-technique includes 536 mg kg?1 for Ba, 95.9 mg kg?1 for Co, 208 mg kg?1 for Cr, 464 mg kg?1 for Mn, and 90.5 mg kg?1 for Ni. The geochemical index, enrichment factor, and the contamination factor register a moderate to considerable contamination in some soil samples.
The aim of this study was to evaluate in the medium term (5 years) the effect of two organic amendments, which were spiked to a degraded soil as a strategy for bioremediation, on the amount and characteristics of soil humic acids (HAs) and their ability to associate with certain extracellular enzymes.
Materials and methods
Soil samples were collected in an experimental field where 5 years earlier, a mixture of the organic fraction of household waste and sewage sludge (2:1 ratio), both composted (composted residue, CR) and non-composted (fresh residue, FR), had been added in triplicate at rates equivalent to 1 % (D1) and 3 % of organic carbon (D2) to 30-m2 plots as a strategy for degraded soil restoration. Humic substances (HSs) and HAs were extracted from the collected soil samples and submitted to chemical, biochemical, spectroscopic (FTIR), and chemical-structural (CPMAS 13C NMR) analyses.
Results and discussion
After 5 years, the amended soils showed significantly higher HS and HA content than did the control soil, and the differences with respect to the control were greater with compost addition than with FR addition. The HA from the amended soils had higher H, N, and S contents than the HA from the non-amended soil in addition to a lower oxygen content and lower O/C ratio values. Furthermore, the FTIR spectra of the HA from the amended soils showed a higher absorption intensity in bands corresponding to aliphatic and amide-carboxylic groups and polysaccharide structures and a lower absorption intensity in bands corresponding to carbonyls and carboxylic groups than the HA from the control. These results were confirmed by 13C-NMR spectra, which showed a clear increase of aliphatic compounds in the HA from the amended soils with respect to the HA from the control. HA spectra were not greatly influenced by the maturity of the amendment or by the application dose.
Conclusions
In general, the addition of organic amendments increased the quantity of enzymes immobilized in the humic colloid. Furthermore, the addition of the composted residues favored to a greater extent the immobilization of the abovementioned enzymes, which represent a biological reservoir in the soil. This is of great importance since these enzymes possess functional capacity even when the soils are under conditions that are stressful or unfavorable for microbial life. An increase in the quantity of immobilized enzymes such as that observed in amended soils supposes an important improvement in soil quality.
Effects of pretreatment of Brassica napus leaves with ascospores of Leptosphaeria biglobosa or chemical defence activators [acibenzolar- S -methyl (ASM) or menadione sodium bisulphite (MSB)] on infection by ascospores of Leptosphaeria maculans (phoma stem canker) and development of disease were studied in controlled-environment (phoma leaf spot) and field (phoma leaf spot and stem canker) experiments. In controlled-environment experiments, pretreatment of oilseed rape leaves (cv. Madrigal) with L. biglobosa , ASM or MSB delayed the appearance of L. maculans phoma leaf spot lesions. These pretreatments also decreased the phoma leaf spot lesion area in both pretreated leaves (local effect) and untreated leaves (systemic effect). In winter oilseed rape field experiments in the 2002/03 and 2003/04 growing seasons, pretreatment with L. biglobosa or ASM in October/November decreased not only the number of phoma leaf spot lesions per leaf caused by L. maculans in autumn/winter, but also the severity of phoma stem canker in the subsequent spring/summer. Effects were greater in 2002/03 (when natural L. maculans ascospore release began in September 2002) than in 2003/04 (when ascospore release began in December following a period of dry weather in August/September 2003). These results suggest that pretreatment with biological or chemical defence activators can induce local and systemic resistance to L. maculans , with both short-term effects on the development of phoma leaf spotting and long-term effects on the development of stem canker 8 months later. 相似文献
Floodplain lakes are ecosystems characterised by annual flood and dry cycles. Fish ecology is influenced by the flood pulse due to the large influx of allochthonous food resources and diversification of habitats during the flood cycle, while during the dry cycle, fishes tend to be confined in reduced habitat. The aim of this study was to evaluate the seasonal variation in trophic niche width and overlap of four species—Mylossoma duriventre, Prochilodus nigricans, Cichla.pleiozona and Serrasalmus rhombeus—in an Amazonian floodplain lake. Stable isotope analyses were used to estimate trophic niche width and overlap during the flood and dry seasons. We hypothesised broader niche width for all species during the flood cycle and a higher degree of overlap between the two piscivorous fishes during the dry cycle. Isotopic niche width was 72% broader for P. nigricans, 61% for S. rhombeus and 54% for C. pleiozona during the dry cycle, which did not support our hypothesis. Core niche width overlaps were not observed between piscivorous species in either flood or dry cycle. The results indicate that seasonal variation in isotopic niche width is specific to feeding habit. Understanding how fish trophic ecology responds to changes in the hydrological regime during the seasons is crucial for sustainable fishery management in a region where many people rely heavily on fish for nutritional and economic purposes. 相似文献