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Soybean seed coat chitinase as a defense protein against the stored product pest Callosobruchus maculatus 下载免费PDF全文
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The contribution shows changes in the phosphorus and nitrogen status in long-term investigated spruce stands in the Lu?ické, the Jizerské and the Orlické Mts. on the border between the Czech Republic and Germany and Poland. During the 11 evaluated years, low phosphorus concentrations were measured, often below the deficiency limit 1.2 mg P/g, and an N/P ratio exceeding the optimal range (6–12), primarily in the second needle-year class. Values of an N/P ratio of between 12 and 18 in the Jizerské Mts. and of between 12 and 27 in the Lu?ické Mts. were discovered. A low phosphorus concentration below the 10 mg·kg?1 was also detected in the mineral soil horizon. Temporal changes of N/P ratio (increase) and of P concentration (decrease) in the needles are significant for the spruce stands that are in the Orlické Mts. In the Jizerské Mts. and the Lu?ické Mts., there is fluctuation during evaluated period without any clear trend. 相似文献
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Gonzalo Almendros Pilar Tinoco José-María De la Rosa Heike Knicker José-Antonio González-Pérez Francisco J. González-Vila 《Journal of Soils and Sediments》2018,18(4):1303-1313
Purpose
Data management strategies of pyrolysis results and NMR acquisition modes were examined in humic acids (HAs) from control soils and fire-affected soils. The information supplied by dipolar dephasing (DD) 13C NMR spectroscopy and Curie-point pyrolysis were used to assess chemical structures hardly recognizable and measurable, or of unclear interpretation, when using 13C NMR under standard acquisition pulses (cross-polarization/magic angle spinning, CPMAS).Materials and methods
The HAs were isolated from two forest soils under Pinus halepensis and Pinus sylvestris in control and burned sites affected by medium or severe-intensity wildfires. For NMR analyses, during DD acquisition conditions, a 180° 13C pulse was inserted to minimize phase shifts. Curie-Point pyrolysis was carried out at 510 °C for 5 s, and the pyrolysis fragments were analyzed by GC/MS. The total abundances of the major pyrolysis products were compared by an update of the classical Van Krevelen’s graphical-statistical approach, i.e., as surface density values in the space defined by the compound-specific H/C and O/C atomic ratios.Results and discussion
The DD 13C NMR experiments displayed significant differences in the HA spectral profiles as regards to the standard CPMAS 13C NMR acquisition conditions, mainly in the chemical shift region of alkyl structures as well as for tannin- or carbohydrate-like O-alkyl structures. In fact, the comparison between DD and CPMAS solid-state NMR suggested shortening of alkyl chains and generation of carbohydrate-derived, unsaturated structures—viz. furans—which adds to the aromatic domain. Pyrolytic results showed fire-induced specific changes in HAs chemical structure and its molecular diversity. The changes were evident in the location and sizes of the different clusters of pyrolysis compounds defined by their atomic ratios.Conclusions
The DD 13C NMR provided specific information on the fate of aliphatic structures and the origin of unsaturated HA structures, which could be helpful in differentiating “inherited” from “pyrogenic” aromatic structures. This is further confirmed by the analysis of the molecular assemblages of pyrolytic products, which showed accumulation of condensed polyaromatic domains in the HAs after the high-intensity fire, accompanied by a recalcitrant alkyl hydrocarbon domain. Medium-intensity fire led to aromaticity increase due to a selective accumulation of lignin-derived phenols concomitant to the depletion of aliphatic hydrocarbon constituents.9.
Gabriela Barančíková Maria Jarzykiewicz Erika Gömöryová Erika Tobiašová Tadeáš Litavec 《Journal of Soils and Sediments》2018,18(8):2738-2747
Purpose
Windthrows and fires are major natural disturbances in forest ecosystems, which can affect organic matter in the surface and the mineral layer of forest soil. The main aim of this study was to evaluate the changes occurring in the structure and properties of humic acid (HA) in the lands where windthrows and wildfires occurred.Materials and methods
In November 2004, the forest in the area of 12,000 ha in the Tatra National Park, Slovakia, was seriously damaged by northern wind gusts exceeding 200 km/h. In July 2005, a wildfire broke out in a 220 ha of wind-damaged area. The HAs have been isolated from four research plots: (a) the area where the fallen trees were removed (EXT); (b) an area after windstorm covered by wood from struck trees (NEX), left for spontaneous succession; (c) an area after extracted timber, damaged by the surface wildfire (FIR); and (d) a reference intact spruce forest area (REF). Changes in the chemical structure of the HAs isolated from the research plots were determined on the basis of elemental analysis and UV-Vis, EPR, IR, and 13C NMR spectroscopy.Results and discussion
All used analytical methods showed a decrease in the humification degree of the humic acids extracted from the soils where the spruce forest has been affected by a wildfire and a windthrow. In the case of the control sample HA (REF), the calculated atomic H/C and O/C ratios and the degree of aromaticity (α) calculated from the 13C NMR spectra were higher, indicating higher aromaticity of HA from the REF area. The more complex and developed structure of REF HA was confirmed by the higher value of E1%6 and the lower E4/E6 ratio obtained using UV-Vis spectroscopy. Also, the higher g-parameters determined from the EPR spectra of the stable radicals present in HA confirmed the lower aromaticity on the plots that have been subjected to the calamities. The 13C NMR spectra and the elemental analysis show that the structure of the HA extracted from the NEX plot is the closest to the REF.Conclusions
The results of the systematic research showed significant changes in the structure of HA taken from spruce forest soils that were subjected to windstorms and fires. An enrichment of the HAs in aliphatic carbon and so a lower humification degree of the organic matter in the areas calamity-affected were observed. The results clearly indicate that the HAs extracted from the disturbed plots of the spruce forest are not as stable as those extracted taken from the control plot.10.
Contrasting patterns of variation in weedy traits and unique crop features in divergent populations of US weedy rice (Oryza sativa sp.) in Arkansas and California 下载免费PDF全文