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The primary objective of this research was to determine if vesicular-arbuscular (VA) mycorrhizal fungi are associated with the roots of common plant species found in North Carolina salt marshes. Root samples of Spartina alterniflora, S. patents, S. cynosuroides, Distichlis spicata, and Juncus roemerianus were collected from eight salt marsh sites. With the exception of S. alterniflora, all plant species were mycorrhizal. A greenhouse experiment was conducted to determine whether unfavorable soil conditions or inherent resistance by the plant inhibited development of mycorrhizal infection in field-collected S. alterniflora. Spartina alterniflora and S. patens were grown from seeds in soil collected from a pure stand of S. alterniflora (soil A) or a mixed stand of S. patens and D. spicata (soil P). Seedlings were harvested weekly for 8 wk, and roots were evaluated for infection by mycorrhizal fungi. Seedlings of S. patens were infected when grown for 2 wk in either soil A or soil P, indicating that soil collected from stands of S. alterniflora did not inhibit mycorrhizal infection in a susceptible host. Percent root length infected in S. patens was always greater in soil P than in soil A. Seedlings of S. alterniflora were not infected by mycorrhizal fungi in either soil A or soil P. Results of the greenhouse study indicate that S. alterniflora may be resistant to infection by vesicular-arbuscular mycorrhizal fungi. 相似文献
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Marielle Medeiros de Souza Maria do Carmo Cauduro Gastaldini Glaucia Ghesti Pivetta 《Environmental Earth Sciences》2017,76(24):833
Diffuse or nonpoint source (NPS) pollution results in different pollutant concentrations, which depend on river catchments, land use and precipitation events and may vary along a single event. This study aimed to assess NPS pollution loads of organic matter, nutrients, bacteria and heavy metals in four river catchments associated with different types of land use in Southern Brazil. Cluster analysis was used to identify similarities between basins and main component analysis (PCA) to identify the main variables that characterize diffuse pollution in each basin. The use and occupation of the soil were determinant in the formation of the clusters. The basins with rural characteristics formed one group, whereas the basin with urban characteristic generated another group. PCA suggests that changes in the water quality of the catchments in this study can be explained by organic pollutants and farming activities. The Rancho do Amaral catchment, with 55.8% of native forest, displayed the lowest NPS pollution load for all tested parameters. The Alto da Colina catchment, with the largest urban area and largest agricultural land use (50%), showed the highest NPS for all variables in the study, even though it has the smallest area. The differences in pollutant loads can be attributed to the intense degradation processes associated with anthropic activities, such as urbanization, agricultural activity and the discharge of effluents, which are different for each catchment. 相似文献
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Marielle Lacombe Vronique Garon Maurice Comtat Louise Oriol Joël Sudre Danile Thouron Nadine Le Bris Christine Provost 《Marine Chemistry》2007,106(3-4):489-497
Silicate has been determined in sea water by four different electrochemical methods based on the detection of the silicomolybdic complex formed in acidic media by the reaction between silicate and molybdenum salts. The first two methods are based on the addition of molybdate and protons in a seawater sample in an electrochemical cell. Cyclic voltammetry presents two reduction and two oxidation peaks giving four values of the concentration and therefore increasing the precision. Then chronoamperometry is performed on an electrode held at a constant potential. A semi-autonomous method has been developed based on the electrochemical anodic oxidation of molybdenum, the complexation of the oxidation product with silicate and the detection of the complex by cyclic voltammetry. This method is tested and compared with the classical colorimetric one during ANT XXIII/3 cruise across Drake Passage (January–February 2006). The detection limit is 1 μM and the deviation between both methods is less than 3% for concentrations higher than 10 μM. Finally a complete reagentless method with a precision of 2.6% is described based on the simultaneous formation of the molybdenum salt and protons in a divided electrochemical cell. This latter method should be very useful for developing a reagentless sensor suitable for long term in situ deployments on oceanic biogeochemical observatories. 相似文献
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