Atmospheric CO2 enrichment alters energy assimilation, investment and allocation in Xanthium strumarium

Energy-use efficiency and energy assimilation, investment and allocation patterns are likely to influence plant growth responses to increasing atmospheric CO2 concentration ([CO2]). Here, we describe the influence of elevated [CO2] on energetic properties as a mechanism of growth responses in Xanthium strumarium. Individuals of X. strumarium were grown at ambient or elevated [CO2] and harvested. Total biomass and energetic construction costs (CC) of leaves, stems, roots and fruits and percentage of total biomass and energy allocated to these components were determined. Photosynthetic energy-use efficiency (PEUE) was calculated as the ratio of total energy gained via photosynthetic activity (Atotal) to leaf CC. Elevated [CO2] increased leaf Atotal, but decreased CC per unit mass of leaves and roots. Consequently, X. strumarium individuals produced more leaf and root biomass at elevated [CO2] without increasing total energy investment in these structures (CCtotal). Whole-plant biomass was associated positively with PEUE. Whole-plant construction required 16.1% less energy than modeled whole-plant energy investment had CC not responded to increased [CO2]. As a physiological mechanism affecting growth, altered energetic properties could positively influence productivity of X. strumarium, and potentially other species, at elevated [CO2].     

A test of adaptive hypotheses: Mandibular traits,nest construction materials,and feeding habits in neotropical social wasps (Vespidae,Polistinae)

Summary. The success of many behaviors in hymenoptera depends on the shape and structure of their mandibles. Neotropical social wasps exhibit variation in the shape of their mandibles; both the type of material used in the nest construction and the food sources have been proposed as selective forces that explain that variation. These hypotheses were studied using Independent Contrast analyses and combined tests of significance between: nine mandibles traits, the type of nest material and food source types. Necrophagy and short fiber use are derived conditions in the subfamily that have evolved five times each, while the use of long fibers and live prey are primitive conditions. The mandible structures appear related to the nest fiber type but not to necrophagy. Particularly, species that use long fibers have bigger internal dorsal tooth, longer internal ventral tooth, and shorter and more curved mandibles. Similar results were obtained by including plant hairs as a third nest material type. These findings open related questions for groups of social insects where studies on evolution of mandibles have emphasized food sources.Received 23 November 2003; revised 9 March 2004; accepted 21 April 2004.     

大豆GmPDS基因的克隆及VIGS表达载体构建和鉴定

病毒诱导的基因沉默(virus induced gene silencing,VIGS)技术是近年来发展起来的一种反向遗传学快速研究基因功能的方法,对于植物特别是难于转化的大豆而言尤其适用。本研究采用PCR技术从大豆(Glycine max)基因组中克隆了八氢番茄红素去饱和酶(phytoene desaturase,PDS)基因的部分序列,命名为GmPDS(Glycinemax PDS)。该片段长430bp,序列分析表明,该基因与大豆八氢番茄红素去饱和酶(GenBank登录号:M64704)cDNA序列同源性为99%。双酶切GmPDS片段和烟草脆裂病毒载体(pTRV2),构建了重组载体pTRV2-GmPDS,并将该重组载体分别转化农杆菌C58C1/pMP90、GV3101和LBA4404,为分析pTRV载体是否可以浸染大豆奠定了基础。     

沉默抑制子CMV 2b基因的克隆及其反向重复植物表达载体的构建

从安徽亳州采集表现明显CMV症状的烟草样本,取ELISA检测阳性反应最强的样本提取总RNA。设计特异性引物扩增CMV RNA2部分片段,克隆并测序。其中包含的2b基因全长336个核苷酸,编码111个氨基酸。将来源于安徽烟草的CMV 2b基因与其它CMV 2b基因进行序列比对,结果表明,来源于安徽烟草的CMV 2b基因与来源于韩国的2b基因AF033667的核苷酸序列相似性最高,达98.8%。构建2b基因系统关系树,也表明来源于安徽烟草的CMV 2b基因与AF033667亲缘关系最近。以安徽CMV 2b为模板,分别扩增大小约为300 bp的正向片段CMV 2b（r）和反向片段CMV 2b（i）。先后将反向片段CMV 2b（i）和正向片段CMV 2b（r）分别插入载体pSK-In所含intron两侧,获得重组质粒pSK-2b（r）-In-2b（i）。再将含intron的正反向片段插入pBIN438,最终得到含CMV 2b部分序列反向重复的植物表达载体pBIN-2b（r）-In-2b（i）。     

玉米叶绿体表达载体的构建及AsRED基因原核表达

从玉米幼嫩叶片中提取玉米叶绿体基因DNA,通过PCR克隆出叶绿体同源重组片段trnA和trnI、叶绿体特异性启动子Prrn以及终止子psbA.构建玉米叶绿体表达载体pBAIRTARED,含有一个人工操纵子,其中,筛选标记基因aadA和红色荧光蛋白报告基因AsRED处于Prrn启动子和psbA终止子控制.将构建的载体转化大肠杆菌BL21（DE3）,观测到重组细胞呈现红色,表明构建的载体可以用于玉米叶绿体转化以及表达报告基因.     

Leaf lifespan and lifetime carbon balance of individual leaves in a stand of an annual herb, Xanthium canadense

Leaf lifespan in response to resource availability has been documented in many studies, but it still remains uncertain what determines the timing of leaf shedding. Here, we evaluate the lifetime carbon (C) balance of a leaf in a canopy as influenced by nitrogen (N) availability. Stands of Xanthium canadense were established with high-nitrogen (HN) and low-nitrogen (LN) treatments and temporal changes of C gain of individual leaves were investigated with a canopy photosynthesis model. Daily C gain of a leaf was maximal early in its development and subsequently declined. Daily C gain at shedding was nearly zero in HN, while it was still positive in LN. Sensitivity analyses showed that the decline in the daily C gain resulted primarily from the reduction in light level in HN and by the reduction in leaf N in LN. Smaller leaf size in LN than in HN led to higher light levels in the canopy, which helped leaves of the LN stand maintain for a longer period. These results suggest that the mechanism by which leaf lifespan is determined changes depending on the availability of the resource that is most limiting to plant growth.     

Niche construction,human behavior,and the adaptive‐lag hypothesis

Niche construction is the process whereby organisms modify selective environments, thereby affecting evolution. The niche‐construction perspective is particularly relevant to researchers using evolutionary methods to interpret human behavior and society. On the basis of niche‐construction theory, we argue against the hypothesis that modern humans experience an atypically large adaptive lag. We stress that humans construct their world largely to suit themselves and frequently buffer adaptive lag through cultural niche construction. Where they are unable to do that, natural selection of genes rapidly ensues. Our argument has implications for evolutionary psychology and human behavioral ecology, and suggests that the methods of the latter are potentially applicable to all human societies, even postindustrial ones.     

Environmental Enhancement Through Use of Recycled Aggregate Concrete in a Two-Stage Mixing Approach

As a high priority of waste management and recycling by the Hong Kong government, Recycled Aggregate (RA) has been used in various construction applications, mainly as sub-grade, roadwork, and unbound materials. However, higher-grade applications are rare. The major barrier encountered is the variation of quality within RA, which causes lower strength, resulted from crystallization of Recycled Aggregate Concrete (RAC). Therefore, the objective of this study is to examine the crystallization of RAC in a Two-Stage Mixing Approach. Following are the five areas of interest: (i) investigate the waste problems in construction activities; (ii) examine the crystal development on the hydration of cement paste; (iii) develop a two-stage mixing approach (TSMA) for improving the performance of RAC; (iv) explore the crystallization of TSMA in comparison with the Normal Mixing Approach (NMA) through use of Differential Scanning Calorimetry (DSC); and (v) verify the results obtained from DSC analysis with those obtained from compressive strength testing. This study adopted 0, 20, and 100% RA substitution in virgin aggregate and measured by DSC and compressive strength on both TSMA and NMA. TSMA uses only half the water for mixing, forming a thin layer of cement slurry on the surface of RA that will permeate into the porous old cement mortar and fill old cracks and voids in the pre-mix process. The results from DSC analysis clearly demonstrated that TSMA can give a better crystallization of CaO·SiO₂·H₂O [CSH] and Ca(OH)₂[CH]. The optimal situation occurs on 20% RA substitution in virgin aggregate, balancing the advantages of each, a finding supported by the results from compressive strength testing. Therefore, TSMA is a superior methodology and opens a wider application for the use of RAC.     

The effect of population structure on the adaptive radiation of microbial populations evolving in spatially structured environments

Spatial structure is thought to be an important factor influencing the emergence and maintenance of genetic diversity. Previous studies have demonstrated that environmental heterogeneity, provided by spatial structure, leads to adaptive radiation of populations. In the present study, we investigate not only the impact of environmental heterogeneity on adaptive radiation, but also of population fragmentation and niche construction. Replicate populations founded by a single genotype of Escherichia coli were allowed to evolve for 900 generations by serial transfer in either a homogeneous environment, or a spatially structured environment that was either kept intact or destroyed with each daily transfer. Only populations evolving in the structured environment with intact population structure diversified: clones are significantly divergent in sugar catabolism, and show frequency-dependent fitness interactions indicative of stable coexistence. These findings demonstrate an important role for population fragmentation, a consequence of population structure in spatially structured environments, on the diversification of populations.