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Mycocentrospora acerina , the causal agent of liquorice rot of carrot roots, produces several cell-wall polysaccharide degrading enzymes in vitro . To assess the involvement of these enzymes in tissue invasion, the production and localization of pectin methylesterases, polygalacturonases, pectate lyases and endoglucanases were measured in root tissue infected by M. acerina . Isoelectrofocusing studies demonstrated the production of three isoforms of pectin methylesterase in healthy tissue. In infected tissue, two isoforms already observed in the culture filtrate and two novel isoforms were detected. Tissue maceration was associated with in vivo production of pectin methylesterase and polygalacturonase, which were first detected on the second day whereas pectate lyase and endoglucanase activities were detected only from the fourth day after infection. Maceration was always detected ahead of the mycelium, indicating diffusion of these enzymes. 相似文献
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Sturges WT Wallington TJ Hurley MD Shine KP Sihra K Engel A Oram DE Penkett SA Mulvaney R Brenninkmeijer CA 《Science (New York, N.Y.)》2000,289(5479):611-613
We detected a compound previously unreported in the atmosphere, trifluoromethyl sulfur pentafluoride (SF(5)CF(3)). Measurements of its infrared absorption cross section show SF(5)CF(3) to have a radiative forcing of 0.57 watt per square meter per parts per billion. This is the largest radiative forcing, on a per molecule basis, of any gas found in the atmosphere to date. Antarctic firn measurements show it to have grown from near zero in the late 1960s to about 0.12 part per trillion in 1999. It is presently growing by about 0.008 part per trillion per year, or 6% per year. Stratospheric profiles of SF(5)CF(3) suggest that it is long-lived in the atmosphere (on the order of 1000 years). 相似文献
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This study assessed the protein and energy requirements of Tra catfish (Pangasianodon hypothalamus) using a bio‐energetic factorial approach. To examine these parameters, a series of inter‐related studies were undertaken to define the various factorial parameters. Studies included controlled laboratory experiments and field‐data collection from commercial farms in the Mekong Delta region of Vietnam. Key components of the model include parameters for maintenance energy (39.7 kJ kg?0.844 day?1 at 32 °C) and protein (0.467 g kg?0.833 day?1 at 32 °C) demands, the effect of animal live‐weight and temperature on growth and maintenance energy demands, the efficiencies of energy and protein utilization at various energy and protein intake levels and the variability in whole body composition with varying live‐weight. Interestingly, both the energy [0.510· (Energy intake) ? 11.143] and protein [0.322·(Protein intake) + 0.665] utilization efficiencies at near satiety feed intake levels were substantially lower than that observed from other fish species. Modelling using these equations was used to iteratively derive optimal diet designs and feeding rations for growing Pangasius catfish. 相似文献
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Lelieveld J Crutzen PJ Ramanathan V Andreae MO Brenninkmeijer CM Campos T Cass GR Dickerson RR Fischer H de Gouw JA Hansel A Jefferson A Kley D de Laat AT Lal S Lawrence MG Lobert JM Mayol-Bracero OL Mitra AP Novakov T Oltmans SJ Prather KA Reiner T Rodhe H Scheeren HA Sikka D Williams J 《Science (New York, N.Y.)》2001,291(5506):1031-1036
The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6 degrees S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere. 相似文献
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T Rockmann CAM Brenninkmeijer G Saueressig P Bergamaschi JN Crowley H Fischer PJ Crutzen 《Science (New York, N.Y.)》1998,281(5376):544-546
Atmospheric carbon monoxide (CO) exhibits mass-independent fractionation in the oxygen isotopes. An 17O excess up to 7.5 per mil was observed in summer at high northern latitudes. The major source of this puzzling fractionation in this important trace gas is its dominant atmospheric removal reaction, CO + OH --> CO2 + H, in which the surviving CO gains excess 17O. The occurrence of mass-independent fractionation in the reaction of CO with OH raises fundamental questions about kinetic processes. At the same time the effect is a useful marker for the degree to which CO in the atmosphere has been reacting with OH. 相似文献
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