Gas exchange, biomass partition, and water relationships of three grass seedlings under water stress

Three grass species, switchgrass ( Panicum virgatum ), foxtail millet ( Setaria italica ), and Old World bluestem ( Bothriochloa ischaemum ), referred to as introduced, traditional, and indigenous species, respectively, in the Loess hilly gully region on Loess Plateau in China, were grown in a growth chamber. Water was withheld to let the soil gravimetric moisture content (SGMC) decline gradually from 14.92% for 15 days. The gas exchange characteristics, leaf water conditions, root and shoot growth, and water use efficiency (WUE) of the three grasses were compared. The SGMC of foxtail millet declined faster than that of switchgrass and Old World bluestem, and it maintained higher leaf water potential at a lower soil water content, indicating that it might have greater drought tolerance. During the process of soil drying, the stomatal conductance (Gs), photosynthesis rate, and transpiration rate (Tr) of foxtail millet and Old World bluestem declined linearly, whereas those of switchgrass declined parabolically. The Gs of each grass was significantly different between the stressed and well-watered (WW) conditions. When the SGMC declined to ≈ 11.0%, 9.5%, and 8.6%, respectively, the leaf water potential was significantly different between the two growing conditions, showing the appearance of non-hydraulic and hydraulic signals. As a result of greater stomatal adjustment ability and a smaller Gs, foxtail millet had a high WUE. Among the three grasses, switchgrass had a high Tr and root/shoot (R/S) ratio under both WW and stressed conditions, and water stress significantly improved its R/S ratio. The results showed that foxtail millet seedlings have the best drought adaptability in the flexible soil–water environment, whereas switchgrass seedlings have the worst, but a high R/S ratio might be advantageous under drought conditions once the seedlings are established.     

国际货币制度的变迁及启示

通过对国际货币制度变迁及其动因的综合分析,阐述了国际货币制度的变迁对中国的影响与启示.     

Tomato spotted wilt virus in peanut tissue types and physiological effects related to disease incidence and severity*

Three peanut cultivars, Georgia Green, NC-V11, and ANorden, were grown using production practices that encouraged the development of Tomato spotted wilt virus (TSWV). The progression of TSWV infection was examined through the season using enzyme-linked immunosorbent assay (ELISA) tests on different tissue types [roots, leaves, pegs (pod attachment stem structures) and pods] and the effect of TSWV infection on physiological functions was examined at three harvest dates. Plants were classed into three severity categories: (i) no TSWV symptoms or previous positive ELISA tests; (ii) less than 50% of leaf tissue exhibiting TSWV symptoms; and (iii) greater than 50% of leaf tissue affected. TSWV showed a slow rate of infection at the beginning of the season and a greater percentage of infection of the roots than in the leaves. Photosynthesis was reduced in virus-affected infected plants by an average of 30% at the mid-season harvest and 51% at the late season harvest compared with virus-free plants across all three cultivars. Leaf tissue with symptoms had lower photosynthetic rates than healthy leaves. There were small differences among cultivars, with cv. ANorden maintaining higher average photosynthetic levels than cv. Georgia Green and higher transpirational levels than cv. NC-V11. The ability to maintain high assimilation physiology in the presence of the virus may help cultivars withstand TSWV infection and maintain final yields.     

大亚湾水交换的数值模拟研究

对大亚湾的潮流场进行三维数值模拟，分别用Lagrange质点追踪法和保守物质输运扩散2种方法研究大亚湾的水交换能力，并把大亚湾分成7个子区域，计算整个海湾和各子区域的水体平均存留时间和更新时间，比较各子区域的水交换能力的大小，分析2种方法结果差异产生的原因。大亚湾的水交换能力受潮致余流流场结构支配。质点追踪模拟结果显示，大亚湾南部及大鹏澳区域质点迁移出海湾的速度较快，哑铃湾、大亚湾北部及范和港区域较慢；保守物质输运扩散模型计算结果显示，大亚湾东南部水体的更新时间最快，水交换能力最强，其次分别为大亚湾中东部、西南部、范和港、大亚湾北部、大鹏澳、哑铃湾。     

含SF6混合气体电击穿特征的试验研究

研究了ＳＦ６及Ｎ２，ＣＯ２，ＣＣｌ２Ｆ２，ＣＣｌ４二元混合气体的电击穿特性。结果表明：二元混合气体ＳＦ６／Ｎ２，ＳＦ６／ＣＯ２中ＳＦ６含量为５０％＿６０％时，其耐电强度与ＳＦ６的耐电强度接近，而价格低于ＳＦ６。     

柱后衍生阳离子交换色谱法测定动物源性饲料原料及饲料中的生物胺

试验采用柱后衍生阳离子交换色谱技术建立同时测定动物源性饲料原料及饲料中组胺、腐胺、尸胺、亚精胺、精胺和酪胺的分析方法。样品以2%磺基水杨酸溶液提取,4%磺基水杨酸溶液和二氯甲烷净化提取样液,采用氨基酸分析仪用阳离子交换色谱柱(LCA K17)、以柠檬酸K液为流动相分离6种生物胺,茚三酮溶液衍生后,可见光检测器于570 nm条件下测定。结果显示,6种生物胺在2~100μmol/L浓度范围内具有良好的线性,相关系数均大于0.999;方法的检出限为5.0 mg/kg,定量限为10.0 mg/kg;3个加标水平的回收率在83.46~111.34%,加标含量范围为25.0~1 000.0 mg/kg,相对标准偏差(RSD,n=6)在0.38%~5.13%。研究表明,此方法的回收率高、选择性好,可应用于动物源性饲料原料及饲料中生物胺的测定。     

Ecosystem-scale biosphere-atmosphere interactions of a hemiboreal mixed forest stand at Järvselja, Estonia

During two measurement campaigns, from August to September 2008 and 2009, we quantified the major ecosystem fluxes in a hemiboreal forest ecosystem in Järvselja, Estonia. The main aim of this study was to separate the ecosystem flux components and gain insight into the performance of a multi-species multi-layered tree stand. Carbon dioxide and water vapor fluxes were measured using the eddy covariance method above and below the canopy in conjunction with the microclimate. Leaf and soil contributions were quantified separately by cuvette and chamber measurements, including fluxes of carbon dioxide, water vapor, nitrogen oxides, nitrous oxide, methane, ozone, sulfur dioxide, and biogenic volatile organic compounds (isoprene and monoterpenes). The latter have been as well characterized for monoterpenes in detail. Based on measured atmospheric trace gas concentrations, the flux tower site can be characterized as remote and rural with low anthropogenic disturbances.Our results presented here encourage future experimental efforts to be directed towards year round integrated biosphere-atmosphere measurements and development of process-oriented models of forest-atmosphere exchange taking the special case of a multi-layered and multi-species tree stand into account. As climate change likely leads to spatial extension of hemiboreal forest ecosystems a deep understanding of the processes and interactions therein is needed to foster management and mitigation strategies.     

关于新风换气机的选择与计算

系统地分析论述了新风换气机的分类情况、选型原则、适用条件、设计要点以及如何使用Microsoft EXCEL表格进行设备选型与节能计算的方法。使我们在实施工程设计中设备的选型与计算更加快速准确。