Clonal integration improves compensatory growth in heavily grazed ramet populations of two inland-dune grasses

Herbaceous species possess several mechanisms to compensate for tissue loss. For clonal herbaceous species, clonal integration may be an additional mechanism. This may especially hold true when tissue loss is very high, because other compensatory mechanisms may be insufficient. On inland dunes in northern China, we subjected Bromus ircutensis and Psammochloa villosa ramets within 0.5 m×0.5 m plots to three clipping treatments, i.e., no clipping, moderate (50% shoot removal) and heavy clipping (90% shoot removal), and kept rhizomes at the plot edges connected or disconnected. Moderate clipping did not reduce ramet, leaf or biomass density of either species. Under moderate clipping, rhizome connection significantly improved the performance of Psammochloa, but not that of Bromus. Heavy clipping reduced ramet, leaf and biomass density in the disconnected plots of both species, but such negative effects were negated or greatly ameliorated when the rhizomes were connected. Therefore, clonal integration contributed greatly to the compensatory growth of both species. The results suggest that clonal integration is an additional compensatory mechanism for clonal plants and may be important for their long-term persistence in the heavily grazed regions in northern China.     

红芽芋球茎片两步法离体快繁及其再生苗生理和光合特性研究

以江西铅山红芽芋(Colocasia esculenta L.Schott var.cormosus‘Hongyayu’)试管苗为材料,建立了芋球茎片两步法离体快繁体系,并对其再生苗的形态指标、染色体数目、生理和光合特性以及叶绿素荧光特性进行了检测。结果表明:(1)红芽芋球茎片单芽诱导的最佳培养基为MS+KT 2 mg/L+6-BA 1 mg/L+NAA0.1mg/L,诱导培养30d后将单芽从球茎片上分离,再接种到生根培养基(MS+KT 2mg/L+NAA 0.1mg/L)上培养30d即可形成完整植株,移栽成活率高达98%;(2)由球茎片单芽、丛生芽、不定芽离体快繁获得的红芽芋再生苗在形态指标、叶下表皮气孔参数、染色体数目、生理生化指标以及叶片光合特性参数和叶绿素荧光特性方面均无显著差异。说明红芽芋球茎片两步法离体培养的再生苗繁殖系数高、染色体数目稳定,该离体快繁体系可应用于江西铅山红芽芋的工厂化生产。     

UNIFICATION OF METHODS FOR ESTIMATING THE STRENGTH OF REPRODUCTIVE ISOLATION

Understanding the evolution of reproductive isolation is tantamount to describing the origin of species. Therefore, a primary goal in evolutionary biology is to identify which reproductive barriers are most important to the process. To achieve this goal, the strength of multiple forms of isolation must be compared in an equivalent manner. However, a diversity of methods has been used to estimate barrier strength, falling into several mathematically distinct categories. This study provides a unified method for calculating isolation that relates the amount of gene flow experienced by taxa to random expectations in a simple linear framework. This approach has three distinct advantages over previous methods: (1) it is directly related to gene flow, (2) it is symmetrical, such that measures in both the positive and negative range are comparable, and (3) it is equivalent between broad categories of reproductive isolation, allowing for appropriate comparisons. This linear formulation can be adjusted for use in all forms of isolation, and can accommodate cases in which null expectations for con‐ and heterospecific gene flow differ. Additionally, this framework can be used to calculate total reproductive isolation and the relative contributions of individual barriers.     

中外水质基准发展趋势和存在的问题

水质基准,是制定水质标准限值的重要依据,是科学的水质管理体系的重要组成部分。我国水体污染形势严峻,区域环境差异明显,亟需建立适合我国水环境特征的水质基准作为水质控制和管理的理论依据。本文就中外水质基准的研究情况进行了探讨,主要包括以下几个方面:1)水质基准的概念及含义;2)欧美国家水质基准的研究历史、现状、发展趋势及存在的关键问题;3)我国水质基准体系的研究重点和发展趋势:包括区域水环境特征调查、人体流行病学调查和生物毒理学研究、水质基准理论与方法学的研究。     

Effects of nutritional restriction on nitrogen and carbon stable isotopes in growing seabirds

When using stable isotopes as dietary tracers it is essential to consider effects of nutritional state on isotopic fractionation. While starvation is known to induce enrichment of ¹⁵N in body tissues, effects of moderate food restriction on isotope signatures have rarely been tested. We conducted two experiments to investigate effects of a 50–55% reduction in food intake on δ¹⁵N and δ¹³C values in blood cells and whole blood of tufted puffin chicks, a species that exhibits a variety of adaptive responses to nutritional deficits. We found that blood from puffin chicks fed ad libitum became enriched in ¹⁵N and ¹³C compared to food-restricted chicks. Our results show that ¹⁵N enrichment is not always associated with food deprivation and argue effects of growth on diet–tissue fractionation of nitrogen stable isotopes (Δ¹⁵N) need to be considered in stable isotope studies. The decrease in δ¹³C of whole blood and blood cells in restricted birds is likely due to incorporation of carbon from ¹³C-depleted lipids into proteins. Effects of nutritional restriction on δ¹⁵N and δ¹³C values were relatively small in both experiments (δ¹⁵N: 0.77 and 0.41‰, δ¹³C: 0.20 and 0.25‰) compared to effects of ecological processes, indicating physiological effects do not preclude the use of carbon and nitrogen stable isotopes in studies of seabird ecology. Nevertheless, our results demonstrate that physiological processes affect nitrogen and carbon stable isotopes in growing birds and we caution isotope ecologists to consider these effects to avoid drawing spurious conclusions.     

Allelopathic effects of the submerged macrophyte <Emphasis Type="Italic">Potamogeton malaianus</Emphasis> on <Emphasis Type="Italic">Scenedesmus obliquus</Emphasis>

Allelopathic effects of the submerged macrophyte Potamogeton malaianus on Scenedesmus obliquus were assessed using a two-phase approach under controlled laboratory conditions. In the co-culture experiment (phase І), the growth of S. obliquus at two different initial cell densities was significantly inhibited by P. malaianus. Moreover, the growth inhibition was dependent on the biomass density of P. malaianus. Antioxidant enzymes (SOD, CAT and POD), MDA, APA, total soluble protein, protein electrophoretic pattern and morphology of S. obliquus were determined after the co-culture experiment was terminated. The activities of SOD, CAT, POD and APA at the low initial cell density were stimulated, the contents of MDA and total soluble protein were increased, and some special protein bands disappeared in P. malaianus treatments. The macrophyte had no effect on the activities of SOD and APA at the high initial cell density, but significantly influenced other physiological parameters of S. obliquus with the increase of biomass density. The morphology of S. obliquus showed no difference in the macrophyte treatments and the controls, and the cultures were dominated by 4-celled coenobia. The results indicated P. malaianus had significant allelopathic effects on the growth and physiological processes of S. obliquus. Moreover, the allelopathic effects depended on initial algal cell density, biomass density of the macrophyte, and their interaction. In the experiment of P. malaianus culture filtrates (phase II), filtrates from combined culture of plant and S. obliquus at the low initial cell density exhibited no apparent growth inhibitory effect on S. obliquus. The result showed that initial addition of growth-inhibiting plant filtrates had no allelopathic effect on S. obliquus. We concluded that the allelopathic effects on S. obliquus were found in the presence of P. malaianus, but not in P. malaianus filtrates. However, the absence of allelopathic effect on S. obliquus might be due to the very low concentrations of allelochemicals in the filtrates. Handling editor: S. M. Thomas     

NaCl胁迫对'金光'杏梅幼苗生长及其生理指标的影响

以‘金光’杏梅盆栽幼苗为试验材料,研究了NaCl胁迫对‘金光’杏梅幼苗生长和生理指标的影响.结果表明:NaCl胁迫显著抑制了‘金光’杏梅幼苗的生长,随着NaCl浓度的升高,‘金光’杏梅的株高、叶面积、叶鲜重、叶干重、茎干重、根干重、叶绿素含量和净光合速率均呈下降趋势;叶片细胞膜透性、丙二醛(MDA)、可溶性糖、脯氨酸(Pro)含量以及POD活性显著增加;而SOD活性在低NaCl浓度下上升,在高NaCl浓度下下降.     

Genetic variation among different populations of Aster tripolium grown on naturally and anthropogenic salt-contaminated habitats: implications for conservation strategies

The sea aster, Aster tripolium L., grows naturally in temperate regions, mainly in the salt meadows close to the coast. The species is also found in naturally and anthropogenically salt-contaminated inland habitats, such as potash mine dumps. The genetic relationships among populations from different habitats and correlations of the genotype with physiological and vegetational parameters were investigated. A. tripolium plants from five different sites close to the seashore on the North Sea island Baltrum, from five different potash mine dumps and, as an outgroup, from the seashore in Japan were probed. DNA was extracted from five plants from each of the 11 A. tripolium populations and analyzed for random amplified polymorphic DNA (RAPD). Altogether 35 polymorphic bands in 51 individuals and 45 different detectable genotypes could be identified. For evaluation of the genetic variation using RAPD bands, the neighbor-joining method, the principal coordinate analysis, and the analysis of molecular variance were applied, resulting in the classification into three genetic groups. A. tripolium plants from different ecological habitats on Baltrum were closely related while the plants growing at the deposit dumps showed a higher genetic diversity. The Japanese population was genetically very different from the German populations. Correlations between phytosociological and soil parameters and the respective genotype were not significant. The results argue for a conservation of anthropogenically salt-contaminated habitats to maintain genetic variability not only on the species level, but also within a species.     

Relationship of aerobic and anaerobic parameters with 400 m front crawl swimming performance

The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake (V.O2PEAK) and total anaerobic contribution (C_ANA). The C_ANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique (V.O2PEAK and alactic contributions of C_ANA) and blood lactate concentration analysis (lactic anaerobic contributions of C_ANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s^-1) and LMS (1.3±0.1 m·s^-1; r = 0.80), V.O2PEAK (4.5±3.9 L·min^-1; r = 0.72) and C_ANA (4.7±1.5 L·O₂; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and V.O2PEAK explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, C_ANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance.     

Temperature manifold for a stopped-flow machine to allow measurements from −10 to +40 °C

Conducting enzymatic stopped-flow experiments at temperatures far removed from ambient can be very problematic because extremes in temperature (<10 °C or >30 °C) can damage the machine or the enzyme. We have devised a simple manifold that can be attached to most commercial stopped-flow systems that is independently heated or cooled separate from the main stopped-flow system. Careful calibration of the flow circuit allows the sample to be heated or cooled to the measurement temperature (−8 to +40 °C) 1 to 2 s before mixing in the reaction chamber. This approach allows measurements at temperatures where the stopped flow or the protein is normally unstable. To validate the manifold, we investigated the well-defined ATP-induced dissociation of rabbit muscle myosin subfragment 1 (S1) from its complex with pyrene-labeled actin. This process has both temperature-dependent and -independent components. Use of ethylene glycol allowed us to measure the reaction below 0 °C and up to 42 °C, and as expected the second-order rate constant (K₁k₊₂) and the maximum rate of dissociation (k₊₂) both increased with temperature, whereas 1/K₁ is unaffected by the change in temperature.