浙江雪胆几种金属元素分布及其与土壤养分之间的关系

对浙江雪胆各器官主要金属元素分布及其与土壤养分之间的关系进行了研究,结果表明,1)浙江雪胆原生土壤中Fe元素的含量最高,其次是K元素,Mn和Zn含量较低;2)植物的各器官中,均以K元素含量最高,其次是Ca和Mg,微量元素Fe、Mn和Zn含量均相对较低;3)Fe、Mn和Zn 3种微量元素均以根中含量为最高,Mg和Ca元素均以块茎中较高,K则以叶中最高;4)同一器官元素分布均呈正相关,而不同器官之间的元素分布整体上呈负相关;5)根中Mg、K和Ca均与土壤元素含量整体上呈负相关,块茎中元素均与土壤元素含量均呈正相关,叶中除Fe元素外,其他元素均与土壤元素含量均呈负相关;6)各器官大量元素的富集系数较高。     

Tolerant and diverse natural killer cell repertoires in the absence of selection

Natural killer (NK) cells are innate lymphocytes that participate in the early control of viruses and tumors. The function of NK cells is under tight regulation by two complementary inhibitory receptor families that bind to classical and non-classical HLA class I molecules: the CD94/NKG2A receptors and the killer cell immunoglobulin-like receptors (KIRs). In this mini-review, recent data on the structure of human NK cell receptor repertoires and its relation to functional responses and tolerance to self are discussed. We propose that no active selection is required to generate diverse NK cell repertoires characterized by a dominant expression of receptors with specificity for self-HLA class I. Instead, the primary consequence of interactions with HLA class I molecules is a functional tuning of randomly generated NK cell repertoires.     

The force of selection on the human life cycle

In this article, I present evidence for a robust and quite general force of selection on the human life cycle. The force of selection acts in remarkably invariant ways on human life histories, despite a great abundance of demographic diversity. Human life histories are highly structured, with mortality and fertility changing substantially through the life cycle. This structure necessitates the use of structured population models to understand human life history evolution. Using such structured models, I find that the vital rates to which fitness is most sensitive are prereproductive survival probabilities, particularly the survival of children ages 0 to 4 years. The fact that the preponderance of selection falls on transitions related to recruitment combined with the late age at first reproduction characteristic of the human life cycle creates a fitness bottleneck out of recruitment. Because of this, antagonistic pleiotropy with any trait that detracts from the constituent transitions to recruitment is expected. I explore the predictors of variation in the force of selection on early survival. High fertility increases the selective premium placed on early survivorship, whereas high life expectancy at birth decreases it.     

Developing fish community based ecohydrological indicators for water resources management in Taiwan

With concerns about the maintenance of both aquatic communities and flow conditions, a number of hydrologic indicators have been developed. These indicators are generally based on the development of hydrologic statistics for flows that are important to the maintenance of aquatic ecosystems. Although the hydrologic basis for indicators is well defined by common techniques in stochastic hydrology, the basis for ecological integration is still being developed. A critical evaluation of hydrologic indicators intended to protect aquatic ecosystems finds that proposed indicators are based more on standard hydrologic statistics and measures of hydrologic alteration than the habitat needs and ecological requirements of local or desired aquatic communities. We argue that hydrologic indicators are not ecohydrological indicators unless direct connections between flow events and aquatic community habitat and ecological needs are the basis of the indicator development and selection. In this article, we identify ecohydrological indicators that are based on habitat and ecological needs of fish communities. The indicator identification process is initiated with the analysis of community needs using an autecology matrix. Hydrologic statistics are then selected that are appropriate to the target fish community. The resulting ecohydrological indicators provide a direct connection to fish community flow requirements and the physical habitat conditions and associated ecology and life history needs of fish species. Handling editor: J. A. Cambray     

Natural durability of selected larch and Scots pine heartwoods in laboratory and field tests

The aim of this study was to compare natural durability of Siberian larch heartwood grown in Siberia and Sweden as well as European larch and Scots pine heartwood grown in Sweden. The study was based on standard in- and above ground tests lasting 12 years but laboratory decay tests with white and brown rot fungi was also included. Field test results showed that Siberian larch heartwood from Siberia was the most durable among the studied heartwoods with a decay index of 60 after 12 years in Simlångsdalen (Sweden), while European larch heartwood grown in Sweden, was decayed to failure before the end of the test. Scots pine heartwood was found to perform similarly to Siberian larch from Siberia. No relationship could be established between natural durability of examined heartwoods and their water absorption behavior; however, strong correlation to the total amount of extractives was observed. Scots pine and Siberian larch heartwood from Siberia had 12.7 and 19.6% total extractives content respectively but the extractives composition differs. The study revealed also that lignin and monosaccharide content could not explain the variations in decay resistance of the studied heartwoods. No similarities in the natural durability revealed by laboratory and field tests were observed.     

Influence and value of different water regimes on avian species richness in arid inland Australia

Riparian habitats in arid landscapes are recognised for their structurally diverse vegetation and diverse bird species assemblages. In the extensive semi-arid and arid centre of Australia, riparian woodland habitats are impacted by pastoral land-use which may negatively influence vegetation structure and avian species composition. However, pastoralism has promoted the establishment of artificial water bodies, so that additional riparian vegetation may occur in the landscape. In this study, we surveyed the importance of different water regimes (i.e. artificial lakes, natural waterholes, desert sites) together with their associated vegetation on avian species richness in north-western New South Wales, Australia. Our results show that bird species richness was highest at water locations, in particular at artificial lakes. Avian species richness was negatively associated with distance to water bodies, both in desert vegetation types and in the riparian vegetation type along dry creeks. Moreover, riparian habitats supported larger avian assemblages and especially those of sedentary bird species compared to the surrounding shrub-steppe landscape. This indicates that artificial water bodies may be of significance for arid zone bird species and might gain in importance with changing water availabilities due to climatic changes.     

Release of transforming plasmid and chromosomal DNA from two cultured soil bacteria

The release of chromosomal and plasmid DNA from Acinetobacter calcoaceticus and Bacillus subtilis cultivated in minimal medium and broth over a period of 50 h was monitored and related to growth phase, autolysis, DNase production and natural competence. The released DNAs were biologically active in natural transformation. In addition, the circular integrity of a released B. subtilis shuttle vector (pHV14) was demonstrated by artificial transformation of Escherichia coli. In cultures of both strains high molecular weight DNA accumulated, particularly during the stationary and death phase (up to 30 g ml^-1). Generally, despite the presence in culture fluids of DNase activity (and of an intracellular enzyme, catalase, indicating some cell lysis) there was high transforming activity of chromsomal and plasmid DNA even 40 h after the cultures reached the stationary phase. In cultures of B. subtilis in minimal medium a presumably active release of intact plasmids and chromsomal DNA occurred during the competence phase. The release of biologically functional DNA during essentially all growth phases of a gram-positive and a gram-negative member of soil bacteria might facilitate horizontal gene transfer by transformation in natural habitats.     

天然珍珠母液及其配方产品实验结果的分析

目的研究分析天然珍珠母液中主要的微量化学成分及其配方产品。方法采用《中华人民共和国国家标准》中的食品氨基酸、牛磺酸和微量元素及化妆品的测定方法进行检测。结果天然珍珠母液富含人体所需的氨基酸、牛磺酸和多种微量元素,具有无致病菌及重金属不超标和产品获得认证的特点。结论天然珍珠母液有潜在的多领域应用和综合开发价值。     

Enantioselective Demethylation of Nicotine as a Mechanism for Variable Nornicotine Composition in Tobacco Leaf

Nicotine and its N-demethylation product nornicotine are two important alkaloids in Nicotiana tabacum L. (tobacco). Both nicotine and nornicotine have two stereoisomers that differ from each other at 2′-C position on the pyrrolidine ring. (S)-Nicotine is the predominant form in the tobacco leaf, whereas the (R)-enantiomer only accounts for ∼0.2% of the total nicotine pool. Despite considerable past efforts, a comprehensive understanding of the factors responsible for generating an elevated and variable enantiomer fraction of nornicotine (EF_nnic of 0.04 to 0.75) from the consistently low EF observed for nicotine has been lacking. The objective of this study was to determine potential roles of enantioselective demethylation in the formation of the nornicotine EF. Recombinant CYP82E4, CYP82E5v2, and CYP82E10, three known tobacco nicotine demethylases, were expressed in yeast and assayed for their enantioselectivities in vitro. Recombinant CYP82E4, CYP82E5v2, and CYP82E10 demethylated (R)-nicotine 3-, 10-, and 10-fold faster than (S)-nicotine, respectively. The combined enantioselective properties of the three nicotine demethylases can reasonably account for the nornicotine composition observed in tobacco leaves, which was confirmed in planta. Collectively, our studies suggest that an enantioselective mechanism facilitates the maintenance of a reduced (R)-nicotine pool and, depending on the relative abundances of the three nicotine demethylase enzymes, can confer a high (R)-enantiomer percentage within the nornicotine fraction of the leaf.     

Ectomycorrhizal colonization of naturally regenerating <Emphasis Type="Italic">Pinus sylvestris</Emphasis> L. seedlings growing in different micro-habitats in boreal forest

We investigated the species richness and composition of ectomycorrhizal (EM) fungi colonizing Pinus sylvestris L. seedlings naturally regenerating in boreal forest, in three different microhabitats: on forest ground, on decaying stumps, and within moss layer on erratic boulders. We tested the hypothesis that habitat differences would affect the composition of the EM community of regenerating pine seedlings. In total, 16 EM species were detected, from which none occurred on seedlings growing in all three microhabitats. Piloderma croceum and Cenococcum geophilum were common for seedlings growing in forest ground and on boulders, while Tricholoma aestuans and Suillus luteus were shared between seedlings growing on forest ground and decaying stumps. EM species richness and composition were strikingly different between seedlings regenerating in different microhabitats. Results are discussed as a function of dispersal and niche differentiation of EM fungi.