小麦D~2型细胞质光敏雄性不育性的研究

D2型细胞质与有些普通小麦材料的细胞核互作,可产生特异核质互作不育现象,其中有的表现为长光照敏感型雄性不育。文章研究了具有D2型细胞质的光敏不育系Ae.crassa—Norin26、核质杂种NC2134及克引11、克引12在黑龙江省克山地区自然条件下的育性表现,并以NC2134为细胞质供体,与20个小麦品种(系)杂交,获得一些核质代换系材料,对其育性及主要性状进行观察研究。结果表明:(1)在自然条件下,播种期对育性有影响,随着播种期推迟,Ae.crassa—Norin26不育度增加,1 999年4月22日播种达到全不育,Norin26则在所设播种条件下表现正常可育;(2)NC2134表现可育,这与其可能携带雄性不育的恢复基因有关,克引11、克引12在正常播种情况下表现高度不育甚至全不育;(3)不育系的不育性表现为不同程度的雄蕊心皮化;(4)不同普通小麦材料其核质杂种育性表现不同,有些材料其核质代换低世代分离出一定比例的高不育、半不育及可育株,通过进一步的核置换,可转育成相应的D2型细胞质不育系。     

Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.     

Bioaccumulation of melamine in catfish muscle following continuous, low-dose, oral administration

In this study, catfish muscle was analyzed for melamine (MEL) and cyanuric acid (CYA) residues following experimental feeding with low doses of MEL and MEL and CYA (MEL+CYA) and with the insoluble melamine-cyanurate complex (MEL=CYA). Catfish were daily fed 0.1 mg/kg BW of MEL for 15, 28, or 42 days, 0.1 mg/kg BW of MEL+CYA for 28 days, 2.5 mg/kg BW of MEL+CYA for 14 days, or 400 mg/kg BW of MEL=CYA for 3 days. Residues in the tissue were determined by LC-MS/MS. MEL was extracted with acidic acetonitrile, followed by defatting with dichloromethane, and isolated with cation exchange solid phase extraction (SPE). For CYA analysis, fish were extracted with dilute acetic acid, defatted with hexane, and cleaned up with a graphitic carbon SPE. Catfish fed 0.1 mg/kg BW of MEL reached a maximum muscle residue concentration of 0.33 ± 0.04 mg/kg (ppm) after 28 days of continuous feeding. The same concentration was found for MEL+CYA feeding at the 0.1 mg/kg BW level for 28 days. Feeding at 2.5 mg/kg BW of MEL+CYA yielded muscle concentrations above the 2.5 mg/kg level of concern for most of the study fish. Finally, catfish fed high levels of the MEL=CYA complex (400 mg/kg BW) accumulated relatively little MEL in the muscle (0.14 ± 0.07 mg/kg) and, unlike treatment with MEL+CYA, did not form renal melamine-cyanurate crystals. Appreciable concentrations of CYA were not detected in any of the muscles tested. These studies provide data to model the bioaccumulation of triazine residues into edible fish tissue as a result of the continuous consumption of adulterated feed.     

Tracing sources of soil nitrate using the dual isotopic composition of nitrate in 2 M KCl-extracts

Soils comprise a critical interface between the atmosphere, lithosphere, hydrosphere and biosphere, and play a major role in the cycling of nitrogen (N), an element crucial to plant growth. Isotope techniques constitute a powerful tool to study the origin and fate of N compounds (e.g. NO₃⁻) within the environment including soils. The objective of our study was to test the usefulness of the isotope composition of soil NO₃⁻ extracted with 2 M KCl (soil NO₃) as a tool to investigate the origin and fate of NO₃⁻ in the environment. Specifically issues related to repeat extractions, crop type, length of fertilization, and soil depth were addressed. Soils from four contrasting agricultural management regimes were sampled. Within the relatively confined study area (4 ha), the isotopic compositions of soil NO₃ differed markedly due to management treatments (up to 6 and 17‰ for δ¹⁵N and δ¹⁸O, respectively), but were repeatable among replicate plots (±1‰). Differences in both δ¹⁵N and δ¹⁸O values were observed between legume and non-legume treatments, as well as fertilized versus non-fertilized treatments, which were larger than the variability observed between replicate plots. Differences in the isotopic composition of extractable soil nitrate were not limited to the surface layer, but also occurred within deeper soil layers. This study indicates that the analysis of the natural abundance stable isotope composition of soil NO₃ may provide a promising additional tool for tracing the origin and fate of NO₃⁻ in the soil zone.     

Analytical method for the determination of cyromazine and melamine residues in soil using LC-UV and GC-MSD

A method is reported for the determination of cyromazine and melamine residues in soil. Soil samples are extracted twice via mechanical shaking, each time with 70% acetonitrile/30% 0.050 M ammomium carbonate for 30 min. An aliquot portion of the pooled extracts is subjected to strong cation exchange (SCX) purification on AG 50W-X4 resin. Final analysis is accomplished using liquid chromatography-ultraviolet (LC-UV) detection at a wavelength of 214 nm. Confirmatory analyses can be performed using gas chromatography-mass selective detection (GC-MSD) in the selected ion monitoring (SIM) mode. The limit of detection (LOD) is 2.5 ng injected and the limit of quantification (LOQ) is 10 ppb when using LC-UV for the analysis of N-cyclopropyl-1,3,5-triazine-2,4, 6-triamine (cyromazine) and 1,3,5-triazine-2,4,6-triamine (melamine). The LOD is 0.050 ng injected and the LOQ is 10 ppb when using GC-MSD for confirmatory analyses. The mean procedural recoveries were 97 and 95% and the standard deviations were 16 and 11% for cyromazine and melamine, respectively (n = 24), when using LC-UV. The mean procedural recoveries were 107 and 92% and the standard deviations were 9.9 and 16% for cyromazine and melamine, respectively (n = 29), when using GC-MSD. The method validation study was conducted under U.S. EPA FIFRA Good Laboratory Practice Guidelines 40 CFR 160. The method also passed an Independent Laboratory Validation (ILV) as per U.S. EPA FIFRA Subdivision N.     

Gehalte von Baumwurzeln an chemischen Elementen einschließlich Schwermetallen aus Luftverunreinigungen

Concentrations of chemical elements in tree roots including heavy metals from air pollution Total concentrations of P, S, Na, K, Mg, Ca, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb were measured in roots from beech, spruce, ash, maple and a forest herb (Mercurialis perennis). The root samples were taken from a site with an acid soil type (Saure Braunerde) and from a site with calcareous soil (Rendzina). All elements except Mn, Zn and Pb (on acid soils) and Ca (on calcareous soils) showed higher concentrations in finest roots (<1 mm diameter) compared to fine roots (1–2 mm). In the case of the toxic heavy metals, this is interpreted as a consequence of reduced root uptake due to physiological processes or to organic complexing, followed by an accumulation at the root surface. Compared with aboveground plant parts, roots show accumulation of Al, Pb, Cd and Zn, indicating reduced translocation from roots to shoots. Roots from acid soil show higher concentrations of P, Mn, and Pb than in calcareous soil. The concentrations of Al and heavy metals in the roots are considered to be a consequence of the contamination of the investigated forest sites by long-range transported air pollutants, i.e. acid precipitation and deposition of heavy metals.     

Untersuchungen über die Freisetzung der Bioelemente aus der organischen Substanz der Humusauflage in einem Buchenbestand

Investigations on the Transfer of Bioelements from Organic Matter to Soil Solution in the Humus Layer of a Beech Stand Monthly and annual fluxes of bioelements were measured in two levels: (a) at the soil surface (= input) and (b) at the lower boundary of the humus layer (= output) by determination of amount and concentration of the precipitation (canopy drip), of the litter and of the seepage. Seepage was collected with funnel lysimeters. By comparison of both fluxes (input-output-analysis) for some bioelements mathematical equations could be derived which describe the transfer of these elements from organic matter to soil solution. The results are explained as consequence of the different bonds of the elements in leaf tissues and in humus substances.     

Flüssebilanzen und aktuelle Änderungsraten der Schwermetall-Vorräte in Wald-Ökosystemen des Soiling

Flux balances and current rates of change of heavy metal stores in forest ecosystems of the Soiling The inventory of the heavy metals Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb is calculated for a beech and a spruce forest ecosystem in the Soiling mountains on the basis of measured concentrations in the vegetation and soil compartments and their dry mass per hectare. The inventory is compared with measured heavy metal fluxes coupled with precipitation above and below the canopy, with seepage water fluxes below the rooting zone (50 cm depth), with litterfall, and with the current increment to biomass. The ratios between heavy metal stores in the forest floor layers (table 3) and the annual flux with litterfall (table 4) show decreasing tendency for liberation of the elements by decomposition of organic matter (OM) in the following order: Mn>OM>Ni>Cd>Cu>Cr ≈? Zn>Co ≈? Fe ≈? Pb Manganese is set free faster than total organic matter. The flux balances for the total ecosystems (table 4) show input > output in the case of Cr, Fe, Cu, Cd, and Pb; input ≈? output for Ni and Zn; input < output for Mn and Co. Heavy metal stores in mineral soil are decreasing by percolation losses and increment to biomass (mainly wood) in the case of all elements investigated, except Zn (under beech), Cd and Pb (table 4). The concentrations of Cu and Pb in the forest floor layers have reached levels at which deleterious effects on microorganisms and litter decomposition are to be expected.     

Differential effects of tomato (Lycopersicon esculentum mill) matrix on the volatility of important aroma compounds

Significant tomato matrix effects on the volatility of certain fresh tomato odorants were found. The concentrations of odorants such as (E,E)-2,4-decadienal, beta-damascenone, and beta-ionone, in crushed fresh tomato fruit obtained by solid-phase microextraction (SPME), resulting from a tomato matrix calibration curve were 5.5-, 2-, and 12-fold higher, respectively, than those calculated by calibration based on buffer solutions. Static headspace analyses indicated that, in most cases, the tomato matrix significantly retains the odorants relative to the buffer solution. Thus, the concentration of odorants in the headspace of tomato is lower than expected compared to a simple matrix such as buffer. CaCl(2), although needed in crushed fruit tissue to block enzymatic activity, was found to interact specifically with 2-isobutylthiazole, reducing its content in the headspace by at least 6-fold. If a matrix effect is found, analysis of the odorant molecule contents in the headspace rather than in the food is recommended in order to better evaluate their access to the olfactory receptors.