苜蓿幼苗芽、根器官对盐胁迫的生理生化响应

探讨盐胁迫对苜蓿幼苗不同器官生长及抗氧化酶系统的影响,为苜蓿植被恢复技术的研发提供理论参考。【方法】以新牧一号(盐忍耐品种)和北极星(盐敏感品种)2个苜蓿品种为材料,以0mmol/L NaCl处理为对照,用200mmol/L NaCl胁迫处理,测定萌发7d苜蓿幼苗芽、根生长及其H2O2、丙二醛(MDA)含量,相对质膜透性、抗氧化保护酶活性及其同功酶的变化。【结果】200mmol/L NaCl胁迫抑制了苜蓿幼苗的生长,并导致芽、根H2O2、MDA含量及相对质膜透性升高,但新牧一号芽、根器官均表现出比北极星较低程度的生长抑制或质膜损伤。盐胁迫后超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、过氧化氢酶(CAT)、过氧化物酶(POD)的活性均明显增加。CAT和POD对活性氧的清除具有器官差异性,CAT活性在芽中较强,POD则与之相反。SOD-Ⅱ、APX-Ⅰ、POD-Ⅲ及POD-Ⅳ为芽、根中盐胁迫敏感的同功酶谱带。【结论】苜蓿盐忍耐品种通过更强的抗氧化保护能力,降低了盐胁迫对其幼苗的损伤。

A Semi-Quantitative Analysis of Essential Micronutrient in Folium Lycii Using Laser-Induced Breakdown Spectroscopy Technique

In this paper, the capabilities of laser-induced break down spectroscopy (LIBS) for rapid analysis to multi-component plant are illustrated using a 1064 nm laser focused onto the surface of folium lycii. Based on homogeneous plasma assumption, nine of essential micronutrients in folium lycii are identified. Using Saha equation and Boltzmann plot method electron density and plasma temperature are obtained, and the irrelative concentration (Ca, Mg, Al, Si, Ti, Na, K, Li, and Sr) are obtained employing a semi-quantitative method.

Determination and identification of isoflavonoids in Radix astragali by matrix solid-phase dispersion extraction and high-performance liquid chromatography with photodiode array and mass spectrometric detection

The isoflavonoids in Radix astragali were determined and identified by HPLC-photodiode array detection-MS after extraction employing matrix solid-phase dispersion (MSPD). As a new sample preparation method for R. astragali, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and Soxhlet extraction. The amounts of two major components in this herb, formononetin (6) and ononin (2), were determined based on their authentic standards. Four major isoflavonoids, formononetin (6), ononin (2), calycosin (5) and its glycoside (1), and three minor isoflavonoids, (6aR,11aR)-3-hydroxy-9, 10-dimethoxypterocarpan (7), its glycoside (3), and (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavone-7-O-beta-D-glycoside (4), were identified based on their characteristic two-band UV spectra and [M + H](+), [aglycone + H](+) and [A1 + H](+) ions, etc. The combined MSPD and HPLC-DAD-MS method was suitable for quantitative and qualitative determination of the isoflavonoids in R. astragali. (C) 2003 Elsevier B.V. All rights reserved.

Natural 13C abundance as a tracer for studies of soil organic matter dynamics

A method for measuring the long- and medium-term turnover of soil organic matter is described. Its principle is based on the variations of 13C natural isotope abundance induced by the repeated cultivations of a plant with a high 13C/12C ratio (C4 photosynthetic pathway) on a soil which has never carried any such plant. The 13C/12C ratio in soil organic matter being about equal to the 13C/12C ratio of plant materials from which it is derived, changing the 13C content of the organic inputs to the soil (by altering vegetation from C3 type into C4 type) is equivalent to a true labelling in situ of the organic matter. Two cases of continuous corn cultivation (Zea mays: δ13C = −12%.) on soils whose initial organic matter average δ13C is −26%. were studied. The quantity of organic carbon originating from corn (that is the quantity which had turned-over since the beginning of continuous cultivation) was estimated using the 13C natural abundance data. After 13 yr, 22% of total organic carbon had turned-over, in the system studied. Particle size fractions coarser than 50μm on the one hand, and finer than 2μm on the other. contained the youngest organic matters. The turnover rate of silt-sized fractions was slower

One step isolation and purification of liquiritigenin and isoliquiritigenin from Glycyrrhiza uralensis Risch using high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) technique in semi-preparative scale has been successfully applied to the separation of bioactive flavonoid compounds, liquiritigenin and isoliquiritigenin in one step from the crude extract of Glycyrrhiza uralensis Risch. The HSCCC was performed using a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-acetonitrile-water (2:2:1:0.6:2, v/v). Yields of liquiritigenin (98.9% purity) and isoliquiritigenin (98.3% purity) obtained were 0.52% and 0.32%. Chemical structures of the purified liquiritigenin and isoliquiritigenin were identified by electrospray ionization-MS (ESI-MS) and NMR analysis. (c) 2005 Published by Elsevier B.V.

Effects of Microstructural Heterogeneity on the Spallation Behavior of Materials

It is of utmost importance to understand the spallation behaviour of heterogeneous materials. In this paper, a driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. The spallation behavior of heterogeneity material is analyzed with this model. The heterogeniety of mesoscopic units is characterized in terms of Weibull modulus m of strength distibution and stress fluctuation parameter k. At high stress, the maximum damage increases with m; while at low stress, the maximum damage decreases. In addition, for low stress, severe stress fluctuation causes higher damage; while for high stress, causes lower damage.

Fracture mechanics of piezoelectric materials

This paper presents an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar piezoelectric materials based on the continuity of normal electric displacement and electric potential across the crack faces. The explicit analytic solutions are obtained for a single crack in an infinite piezoelectric or on the interface of piezoelectric bimaterials. For homogeneous materials it is found that the normal electric displacement D-2, induced by the crack, is constant along the crack faces which depends only on the remote applied stress fields. Within the crack slit, the perturbed electric fields induced by the crack are also constant and not affected by the applied electric displacement fields. For bimaterials, generally speaking, an interface crack exhibits oscillatory behavior and the normal electric displacement D-2 is a complex function along the crack faces. However, for bimaterials, having certain symmetry, in which an interface crack displays no oscillatory behavior, it is observed that the normal electric displacement D-2 is also constant along the crack faces and the electric field E-2 has the singularity ahead of the crack tip and has a jump across the interface. Energy release rates are established for homogeneous materials and bimaterials having certain symmetry. Both the crack front parallel to the poling axis and perpendicular to the poling axis are discussed. It is revealed that the energy release rates are always positive for stable materials and the applied electric displacements have no contribution to the energy release rates.

FEM Simulations and Optimization about Residual Stresses in Coating Structures with Functionally Graded Materials Layer

An elasto-plastic finite element method is developed to predict the residual stresses of thermal spraying coatings with functionally graded material layer. In numerical simulations, temperature sensitivity of various material constants is included and mix