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61.
The question of what determines plant community composition is fundamental to the study of plant community ecology. We examined
the relative roles of historical land use, landscape context, and the biophysical environment as determinants of plant community
composition in regenerating citrus groves in north-central Florida. Results were interpreted in light of plant functional
traits. Herbaceous and woody plants responded differently to broad-scale variables; herbs correlated most strongly with surrounding
land cover at a scale of 8 km, while the only significant determinant of woody species distributions was local land use history.
There were significant correlations between herbaceous species and spatial context, habitat isolation, environmental variables,
and historical variables. Partial Mantel tests indicated that each variable provided a unique contribution in explaining some
of the variation in the herbaceous dataset. The correlation between woody plants and local historical variables remained significant
even with other effects corrected for. In the herbaceous community, species composition was linked to functional traits much
as expected from classical theory. While spatial influences in our study system are important for both woody and herbaceous
plants, the primary determinant of plant community composition in regenerating citrus groves is historical land use. Our results
suggest that the fine-scale mechanisms of local competition, tolerance and facilitation invoked by many classical studies
may ultimately be less important than land use history in understanding current plant community composition in regenerating
agricultural areas. 相似文献
62.
Dueger EL George LW Angelos JA Tankersley NS Luiz KM Meyer JA Portis ES Lucas MJ 《American journal of veterinary research》2004,65(9):1185-1188
OBJECTIVE: To evaluate the efficacy of ceftiofur crystalline-free acid (CCFA) administered into the posterior aspect of an ear for treatment of corneal ulceration associated with naturally occurring infectious bovine keratoconjunctivitis (IBK). ANIMALS: 78 beef calves located at Sierra Foothills Field Station (SFS) and 52 calves located at a commercial dairy (CD). All calves were from 3 to 9 months old. PROCEDURE: At each site, calves were randomly allocated to 1 of 2 treatment groups by use of a block design determined by corneal ulcer size. A single dose of CCFA (6.6 mg of ceftiofur equivalents/kg, s.c.) was administered into the posterior aspect of a pinna. A second group of calves received a single dose of vehicle (0.03 mL/kg, s.c.; controls). Corneal ulcers were photographed, and clinical signs were assessed in calves every 3 to 4 days for 21 days. RESULTS: A positive treatment effect was detected at SFS. Results at the CD were inconclusive because ulcer healing occurred rapidly in control and CCFA-treated calves. At SFS, treatment with CCFA resulted in shorter mean healing times, smaller corneal ulcer surface area measurements, amelioration of ocular discharge and photophobia, and a 50% increase in the percentage of calves healed by day 14. After adjustment for initial corneal ulcer size, treatment with CCFA resulted in a 4-fold increase in the odds of corneal ulcer healing by day 14, compared with controls. CONCLUSIONS AND CLINICAL RELEVANCE: A single dose of CCFA administered into the posterior aspect of a pinna had a positive treatment effect against naturally occurring IBK in calves with corneal ulcerations. 相似文献
63.
64.
M. Angeles Achon Marion Pinner Vicente Medina George P. Lomonossoff 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(7):697-705
Two isolates of maize dwarf mosaic virus (MDMV-Sp and MDMV-Spl) obtained from maize in the northeast of Spain were studied. Both isolates induced similar reactions on 6 sorghum cultivars, johnsongrass and oat (cv. Clintland), with the exception of MDMV-Sp which produced a different reaction on one sorghum cultivar. Thirty-three grass species were tested as possible hosts (16 previously untested) and 18 were found to be susceptible. Among those, eight were previously unidentified hosts for MDMV:Aegilops ovata, A. ventricosa, Avena barbata, Bromus alopecurus, B. diandrus, B. fasciculatus, Echinaria capitata andLolium rigidum. Both isolates were transmitted from maize to maize nonpersistently byRhopalosiphum maidis, R. padi, Schizaphis graminum andSitobium avenae. The virus was not seed-transmitted in Mo17 and B73 maize inbred lines. Pinwheels, scrolls and short curved laminated aggregates were observed in the cytoplasm of maize cells infected by MDMV-Sp or MDMV-Sp1. In addition, laminated aggregates were observed in cells infected by MDMV-Sp1. 相似文献
65.
Anderson JD Johnson TV Schubert G Asmar S Jacobson RA Johnston D Lau EL Lewis G Moore WB Taylor A Thomas PC Weinwurm G 《Science (New York, N.Y.)》2005,308(5726):1291-1293
Radio Doppler data from the Galileo spacecraft's encounter with Amalthea, one of Jupiter's small inner moons, on 5 November 2002 yield a mass of (2.08 +/- 0.15) x 10(18) kilograms. Images of Amalthea from two Voyager spacecraft in 1979 and Galileo imaging between November 1996 and June 1997 yield a volume of (2.43 +/- 0.22) x 10(6) cubic kilometers. The satellite thus has a density of 857 +/- 99 kilograms per cubic meter. We suggest that Amalthea is porous and composed of water ice, as well as rocky material, and thus formed in a cold region of the solar system, possibly not at its present location near Jupiter. 相似文献
66.
Tsiropoulos NG Miliadis GE Likas DT Liapis K 《Journal of agricultural and food chemistry》2005,53(26):10091-10096
Dissipation of the fungicide spiroxamine in grapes of two vine varieties, Roditis and Cabernet Sauvignon, exposed to field treatments was evaluated. Vines of a grape vineyard located in central Greece were sprayed once or twice with a commercial formulation of the fungicide at 30 g a.i./hL. Residues in grapes, must, and wine were determined by gas chromatography/IT-MS after extraction with cyclohexane-dichloromethane (9:1), with a limit of quantitation 0.02 mg/kg in grapes and 0.012 mg/kg in wine. Under field conditions, spiroxamine dissipation on grapes was faster during the first 2 weeks and then slower to the sixth week. About 7 days after application, half of the initial spiroxamine concentration remained on the grapes; the respective proportion at 42 days was about 10%. At 14 and 35 days, residues were lower than 0.44 and 0.22 mg/kg, respectively, values below the maximum residue levels set by the European Union (1 mg/kg). Spiroxamine residues transferred from grapes into the must and through the vinification process into the wine were also studied. Mean transfer factors of 0.26 and 0.55 were found from grapes into wine for the wines obtained without maceration and with maceration, respectively. Residues in wine, prepared from grapes with a spiroxamine content of 0.11-0.20 mg/kg, varied from <0.026 to 0.09 mg/kg. Spiroxamine diastereomer B was found to dissipate slower than diastereomer A in the field as well as during the vinification process. 相似文献
67.
Fernández-Surumay G Osweiler GD Yaeger MJ Rottinghaus GE Hendrich S Buckley LK Murphy PA 《Journal of agricultural and food chemistry》2005,53(10):4264-4271
The effects of fumonisin B-glucose reaction products in swine diets was examined. Pigs were fed diets containing 528 micromol of total fumonisin B/kg (FB), 528 micromol of total FB-glucose adducts/kg (FB-G, 122 micromol of unreacted FB/kg), or 0 micromol of total FB/kg for 15 days to test the efficacy of the FB-G reaction products in detoxifying FB. Weight gain in FB pigs was lower than in FB-G or controls, which was correlated with feed intake reduction in FB pigs. Serum aspartate aminotransferase, gamma-glutamyltransferase, and total bilirubin in FB pigs were higher than in FB-G or control pigs. Serum sphinganine/shingosine ratios in FB pigs were higher than in FB-G or control pigs. Microscopic examination of tissues from FB pigs showed generalized liver necrosis and apoptosis with marked cellular pleomorphism and disorganized hepatic cords. The liver and kidneys in the FB-G group appeared to be normal. Tissues of controls were free of lesions. Results suggest that dietary FB-G products are less toxic to swine and may provide an detoxification approach in instances of widespread FB grain contamination (p < 0.05). 相似文献
68.
Coleman JN Lotya M O'Neill A Bergin SD King PJ Khan U Young K Gaucher A De S Smith RJ Shvets IV Arora SK Stanton G Kim HY Lee K Kim GT Duesberg GS Hallam T Boland JJ Wang JJ Donegan JF Grunlan JC Moriarty G Shmeliov A Nicholls RJ Perkins JM Grieveson EM Theuwissen K McComb DW Nellist PD Nicolosi V 《Science (New York, N.Y.)》2011,331(6017):568-571
If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties. 相似文献
69.
Annet Namayanja Robin Buruchara George Mahuku Patrick Rubaihayo Paul Kimani Stephen Mayanja Hellen Eyedu 《Euphytica》2006,151(3):361-369
Inheritance of resistance to angular leaf spot (ALS) disease caused by Phaeoisariopsis griseola (Sacc.) Ferr was investigated in two common bean cultivars, Mexico 54 and BAT 332. Both Andean and Mesoamerican backgrounds were used to determine the stability of the resistance gene in each of the two cultivars. Resistance to P. griseola was phenotypically evaluated by artificial inoculation with one of the most widely distributed pathotypes, 63–39. Evaluation of the parental genotypes, F1, F2 and backcross populations revealed that the resistance to angular leaf spot in the cultivars Mexico 54 and BAT 332 to pathotype 63–39 is controlled by a single dominant gene, when both the Andean and Mesoamerican backgrounds were used. Allelism test showed that ALS resistance in Mexico 54 and BAT 332 to pathotype 63–39 was conditioned by the same resistance locus. Resistant and susceptible segregating populations generated using Mexico 54 resistant parent were selected for DNA extraction and amplification to check for the presence /absence of the SCAR OPN02 and RAPD OPE04 markers linked to the Phg-2 resistance gene. The results indicated that the SCAR OPN02 was not polymorphic in the study populations and therefore of limited application in selecting resistant genotypes in such populations. On the other hand, the RAPD OPE04 marker was observed in all resistant individuals and was absent in those scored susceptible based on virulence data. Use of the RAPD OPE04 marker in marker-assisted selection is underway. 相似文献
70.
Chitosan is considered to be one of the most promising and applicable materials in adsorption applications. The existence of amino and hydroxyl groups in its molecules contributes to many possible adsorption interactions between chitosan and pollutants (dyes, metals, ions, phenols, pharmaceuticals/drugs, pesticides, herbicides, etc.). These functional groups can help in establishing positions for modification. Based on the learning from previously published works in literature, researchers have achieved a modification of chitosan with a number of different functional groups. This work summarizes the published works of the last three years (2012–2014) regarding the modification reactions of chitosans (grafting, cross-linking, etc.) and their application to adsorption of different environmental pollutants (in liquid-phase). 相似文献