Effect of Shaking on the Growth of Diluted Cultures of Tetrahymena

ABSTRACT. Cultures of Tetrahymena pyriformis, T. thermophila and T. pigmentosa have been studied with regard to growth rates in shaken and unshaken flasks. In the standard medium, a minimum doubling time of 170 min was obtained for T. pyriformis at 28° C in the unshaken cultures. If the depth of the medium was less than 1 cm, the gyratoric shaking increased the doubling time to 340 min. The effect of shaking could be reduced by the addition of dextrane. Cells subjected to shaking were observed in different media and at different growth temperatures. If cultures were inoculated with 10⁴ cell·ml⁻¹ or more, the effect of shaking was absent. However, with inoculates of 10³ or 10² cell·ml⁻¹, the doubling times for T. pyriformis increased to 240 and 275 min, respectively. Periods of 2 min shaking followed by rest for 60 min could not induce an effect.     

Three new genera of the Asteraceae-Gnaphalieae from the Gape Region

Three new monotypic genera from the Cape Floral Region of South Africa are described. Calotesta Karis, a genus closely related to Metalasia and Alrichantha gemmifera (Karis, 1989) is characterized by its persistent, thick and strongly cutinized testa epidermis. The more distantly related Hydwidea has rather large, solitary white capitula and very thick-walled apical pappus cells. Planea Karis is a new genus established for Metalasia schlechteri L. Bol., a species which must be removed from Metalasia (Karis, 1989). Planea has strongly carinate leaves with involute but characteristically flat margins and narrowly ovate apical anther appendage with a peculiar marginal pattern. Discussions concerning morphology and systematic position as well as illustrations and distribution maps of all taxa are provided.     

几种念珠菌DNA总含量的流式细胞分析

应用流式细胞术(FCM)对处于稳定生长阶段的念珠菌属(Candida)的7种8株念珠菌进行了DNA总含量的流式细胞(FCM)分析。这8株念珠菌是:白念珠菌(C.albicans)2株,热带念珠菌(C.tropicalis),克柔念珠菌(C.krusei),近平滑念珠菌(C.parapsiolosis),乳酒念珠菌(C.kefyr),白念珠菌星形变种(C.stellatoidea),即血清B型白念珠菌,季也蒙念珠菌(C.guilliermondii)各一株。应用EB一步插入法染色,用鸡红细胞(CRBC)作为内参标准进行DNA总含量测定。分析结果表明:稳定生长阶段的组方图上,大多数念珠菌细胞处于DNA合成周期的G_0/G_1期;DNA总含量有明显的种间和种内差异。     

Kinetics of Ion Uptake in Higher Plants

Single, multiphasic mechanisms located in the plasmalemma and the tonoplast are proposed to mediate ion uptake in cells of higher plants. There are no parallel uptake mechanisms and, normally, little or no free diffusion across the plasmalemma. The plasmalemma controls the rate of uptake at low external salt concentrations, while the tonoplast may become rate-limiting at high concentrations.     

The impact of nitrogen deposition on carbon sequestration in European forests and forest soils

An estimate of net carbon (C) pool changes and long‐term C sequestration in trees and soils was made at more than 100 intensively monitored forest plots (level II plots) and scaled up to Europe based on data for more than 6000 forested plots in a systematic 16 km × 16 km grid (level I plots). C pool changes in trees at the level II plots were based on repeated forest growth surveys At the level I plots, an estimate of the mean annual C pool changes was derived from stand age and available site quality characteristics. C sequestration, being equal to the long‐term C pool changes accounting for CO₂ emissions because of harvest and forest fires, was assumed 33% of the overall C pool changes by growth. C sequestration in the soil were based on calculated nitrogen (N) retention (N deposition minus net N uptake minus N leaching) rates in soils, multiplied by the C/N ratio of the forest soils, using measured data only (level II plots) or a combination of measurements and model calculations (level I plots). Net C sequestration by forests in Europe (both trees and soil) was estimated at 0.117 Gton yr^?1, with the C sequestration in stem wood being approximately four times as high (0.094 Gton yr^?1) as the C sequestration in the soil (0.023 Gton yr^?1). The European average impact of an additional N input on the net C sequestration was estimated at approximately 25 kg C kg^?1 N for both tree wood and soil. The contribution of an average additional N deposition on European forests of 2.8 kg ha^?1 yr^?1 in the period 1960–2000 was estimated at 0.0118 Gton yr^?1, being equal to 10% of the net C sequestration in both trees and soil in that period (0.117 Gton yr^?1). The C sequestration in trees increased from Northern to Central Europe, whereas the C sequestration in soil was high in Central Europe and low in Northern and Southern Europe. The result of this study implies that the impact of forest management on tree growth is most important in explaining the C pool changes in European forests.     

Comparative bite forces and canine bending strength in feline and sabretooth felids: implications for predatory ecology

The sabretooth felids were widespread across much of the world in the Late Tertiary, and appear to have been an important group of large predators. Owing to the substantially different skull morphology of derived sabretooths compared with extant felids, there has been considerable debate over the killing mode, bite forces, and bending strength of the large upper canines, and over the implications of these characteristics on feeding ecology. Debates have, however, usually been based on indirect comparisons of force vectors. In this paper, I provide assessments of the estimated force output from the jaw adductor muscles, based on estimates of muscle cross-sectional areas and force vectors, along with canine bending strengths, in a variety of sabretooth felids, in comparison with extant felids. In general, sabretoothed felids had moderately powerful bites, albeit with less jaw adductor power for their body sizes compared with extant felids, sometimes markedly so. Less derived sabrecats appear to have had proportionally higher bite forces than derived forms. The length of the upper canines seemingly compromised their bending strength at any given body size, and again this was most marked in derived forms. However, compared with estimated jaw adductor forces, the canines of sabrecats appear, if anything, to have been stronger than those of extant conical-toothed felids. It has previously been suggested that large sabretoothed felids hunted large prey with a canine shearing bite, powered in part by the jaw adductors and in part by the muscles of the upper neck–occipital region. The present results of canine bending strengths versus the predicted bite force from the jaw adductors supports this suggestion.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 151 , 423–437.     

Genetic tagging: contemporary molecular ecology

Population genetic analyses have been highly successful in deciphering inter- and intra-specific evolutionary relationships, levels of gene flow, genetic divergence and effective population sizes. Parameters estimated by traditional population genetic analyses are evolutionary averages and thus not necessarily relevant for contemporary ecological or conservation issues. Molecular data can, however, also provide insight into contemporary patterns of divergence, population size and gene flow when a sufficient number of variable loci are analysed to focus subsequent data analyses on individuals rather than populations. Genetic tagging of individuals is an example of such individual-based approaches and recent studies have shown it to be a viable alternative to traditional tagging methods. Owing to the ubiquitous presence of hyper-variable DNA sequences in eukaryote genomes it is in principle possible to tag any eukaryote species and the required DNA can be obtained indirectly from substrates such as faeces, sloughed skin and hair. The purpose of this paper is to present the concept of genetic tagging and to further advocate the extension of individual-based genetic analyses beyond the identification of individuals to other kinds of relationships, such as parent-offspring relations, which more fully exploit the genetic nature of the data.     

The Cinnamon Ibon Hypocryptadius cinnamomeus is a forest canopy sparrow

The Cinnamon Ibon inhabits the canopy of cloud‐forest of Mindanao Island in the Philippines, and has until now been classified as an aberrant member of the Zosteropidae (white‐eyes). We assessed the systematic position of this enigmatic species using DNA sequence data (two mitochondrial markers, two nuclear introns and two nuclear exons) and broad taxon sampling. The species was robustly placed among the granivorous passeroid clades, as a basal branch in the family of true sparrows, Passeridae. Morphological data lend further support, as the Cinnamon Ibon shows similar specialization of the skull as other granivorous passeroids. The species’ restricted distribution in the montane cloud‐forest of the island of Mindanao, which is of oceanic origin, is difficult to explain without assuming an over‐water dispersal event.     

鼎湖山森林土壤渗透水酸度和无机氮含量对模拟氮沉降增加的早期响应

在林地分别喷加0、50、100和150kg N hm^-1a^-1,研究鼎湖山马尾松林、马尾松针阔混交林和季风常绿阔叶林中土壤20cm深渗透水酸度和无机氮含量在开始9个月的变化。结果表明,3种森林对照样方土壤渗透水pH值为3．82—4．24,外加氮处理使其平均降低了0．08—0．18。3个森林对照样方土壤渗透水无机氮平均含量分别为6．14、6．66和11．64mg L^-1,铵态氮占15．0％、11．9％和3．0％。外加氮处理使3种森林土壤渗透水铵态氮和硝态氮含量均有不同程度的提高,这表明外加氮处理不但增加了无机氮从森林土壤流失的潜力,而且使土壤进一步酸化。