bluuebunny/crossref_metadata_2025 huggingface dataset:
Clarifying the Source of Black Shank Resistance in Flue-cured Tobacco
Authors: Johnson Charles S. , Pattison Jeremy A. , Clevinger Elizabeth M. , Melton Thomas A. , Fortnum Bruce A. , Mila Asamina
Published: June 2008

Widespread use of resistance to race 0 of Phytophthora nicotianae in flue-cured tobacco (Nicotiana tabacum) has increased problems with race 1 in commercial fields. The RAPD marker UBC30, tightly linked to the Ph gene for resistance to race 0, was used to clarify the presence of the Ph gene in specific cultivars to enable farmers to more appropriately match cultivar resistance to the pathogen races predominating in their fields. The marker UBC30 was present in 20 of the 31 flue-cured tobacco cultivars tested, including CC 27, GL 350, NC 196, SP 220, SP 225, SP 227, and NC 810. These cultivars were previously thought to not possess the Ph gene. Presence of UBC30 was highly correlated (r = 0.93; P ≤ 0.001) with survival in fields infested primarily with race 0, and with greater survival in fields infested primarily with race 0 versus race 1 of the pathogen (r = 0.76; P ≤ 0.001). The likely presence of the Ph gene in so many currently grown flue-cured tobacco cultivars may limit farmers' ability to shift pathogen populations back to race 0 from race 1 via the recommended cultivar rotation strategy.

Accepted for publication 27 February 2008. Published 18 June 2008.
Effect of Soybean Cultivars Moderately Resistant to Soybean Cyst Nematode on SCN Populations and Yield
Authors: Adee Eric A. , Johnson Martin L. , Niblack Terry L.
Published: June 2008

Spread of soybean cyst nematode Heterodera glycines (SCN) to much of the soybean (Glycine max) growing region in the Midwest has created a persistent and significant annual yield loss for soybean. Host resistance has been the primary means of reducing yield loss to SCN. It is not known how moderately resistant cultivars fit into the management of SCN. Moderately resistant cultivars can have high yield potential, but nematode reproduction is greater than on resistant cultivars. Moderate resistance is defined by a SCN female index (FI) of 10 to 29 in standardized tests, whereas cultivars with an FI < 10 are considered resistant. Two each of SCN-resistant, moderately resistant, and susceptible (FI > 60) cultivars were planted in the same plots for two soybean crops in annual rotation with corn. The SCN population was reduced 80 and 54% by resistant and moderately resistant cultivars, respectively, and increased 189% by the susceptible. Yields of the resistant and moderately resistant were 8.2 and 11.8 bu/acre better, respectively, than for the susceptible. All plots were planted to a susceptible cultivar in the final year of the study, and demonstrated there was a carry-over effect from previous cultivars. Following resistant and moderately resistant cultivars, yields of the susceptible were 6.6 and 4.3 bu/acre above following susceptible cultivars. This study showed that moderately resistant soybean cultivars can be an effective tool for improving profitability of soybean.

Accepted for publication 9 April 2008. Published 18 June 2008.
Fish odour triggers conspecific attraction behaviour in an aquatic invertebrate
Authors: Kullmann Harald , Thünken Timo , Baldauf Sebastian A , Bakker Theo C.M , Frommen Joachim G
Published: July 2008

Group living has evolved as an adaptation to predation in many animal species. In a multitude of vertebrates, the tendency to aggregate varies with the risk of predation, but experimental evidence for this is less well known in invertebrates. Here, we examine the tendency to aggregate in the freshwater amphipodGammarus pulexin the absence and presence of predator fish odour. Without fish odour, the gammarids showed no significant tendency to aggregate. In contrast to this, in fish-conditioned water, they significantly preferred to stay close to conspecifics. Predation risk can, thus, influence gammarids social behaviour.
Selection on personality in a songbird affects maternal hormone levels tuned to its effect on timing of reproduction
Authors: Groothuis Ton G.G , Carere Claudio , Lipar Joe , Drent Piet J , Schwabl Hubert
Published: July 2008

The increase or decrease in yolk androgens over the laying sequence of a clutch in birds may mitigate or enhance, respectively, the disadvantage of the last-hatched chicks, providing a potentially adaptive tool to adjust brood size to food conditions. This variation may involve a genetic component on which Darwinian selection can act. We found that two lines of a wild bird species selected for bold and shy personalities show, respectively, increased and decreased androgen concentrations over the laying sequence. The line showing the increase laid earlier in the season, when food conditions are normally sufficient to raise the whole brood. The line showing the decrease laid later, when food is normally scarce, which may facilitate brood reduction. The results indicate a correlated response in maternal hormone transfer to genetic selection on personality, which relates to ecological conditions.
Systematic construction and prediction of the arrangement of the strands of sandwich proteins
Authors: Papatheodorou T.S , Fokas A.S
Published: July 2008

The problem of predicting the three-dimensional structure of a protein starting from its amino acid sequence is regarded as one of the most important open problems in biology. Here, we solve aspects of this problem for the so-called sandwich proteins that constitute a large class of proteins consisting of only β-strands arranged in two sheets. A breakthrough for this class of proteins was announced in Kister
et al
. (Kister
et al.
2002
Proc. Natl Acad. Sci. USA
99
, 14 137–14 141), in which it was shown that sandwich proteins contain a certain invariant substructure called
interlock
. It was later noted that approximately 90% of the observed sandwich proteins are
canonical
, namely they are generated by certain
geometrical structures
. Here, employing a topological investigation, we prove that interlocks and geometrical structures are the direct consequence of certain biologically motivated fundamental principles. Furthermore, we construct all possible canonical motifs involving 6–10 strands. This construction limits dramatically the number of possible motifs. For example, for sandwich proteins with nine strands, the
a priori
number of possible canonical motifs exceeds 360 000, whereas our construction yields only 49 geometrical structures and 625 canonical motifs.
Towards a virtual lung: multi-scale, multi-physics modelling of the pulmonary system
Authors: Burrowes K.S , Swan A.J , Warren N.J , Tawhai M.H
Published: July 2008

The essential function of the lung, gas exchange, is dependent on adequate matching of ventilation and perfusion, where air and blood are delivered through complex branching systems exposed to regionally varying transpulmonary and transmural pressures. Structure and function in the lung are intimately related, yet computational models in pulmonary physiology usually simplify or neglect structure. The geometries of the airway and vascular systems and their interaction with parenchymal tissue have an important bearing on regional distributions of air and blood, and therefore on whole lung gas exchange, but this has not yet been addressed by modelling studies. Models for gas exchange have typically incorporated considerable detail at the level of chemical reactions, with little thought for the influence of structure. To date, relatively little attention has been paid to modelling at the cellular or subcellular level in the lung, or to linking information from the protein structure/interaction and cellular levels to the operation of the whole lung. We review previous work in developing anatomically based models of the lung, airways, parenchyma and pulmonary vasculature, and some functional studies in which these models have been used. Models for gas exchange at several spatial scales are briefly reviewed, and the challenges and benefits from modelling cellular function in the lung are discussed.
Mechanisms of transmurally varying myocyte electromechanics in an integrated computational model
Authors: Campbell Stuart G , Flaim Sarah N , Leem Chae H , McCulloch Andrew D
Published: July 2008

The mechanical properties of myocardium vary across the transmural aspect of the left ventricular wall. Some of these functional heterogeneities may be related to differences in excitation–contraction coupling characteristics that have been observed in cells isolated from the epicardial, mid-myocardial and endocardial regions of the left ventricle of many species, including canine. Integrative models of coupled myocyte electromechanics are reviewed and used here to investigate sources of heterogeneous electromechanical behaviour in these cells. The simulations (i) illustrate a previously unrecognized role of the transient outward potassium current in mechanical function and (ii) suggest that there may also exist additional heterogeneities affecting crossbridge cycling rates in cells from different transmural regions.
Biomechanical functional and sensory modelling of the gastrointestinal tract
Authors: Liao Donghua , Lelic Dina , Gao Feng , Drewes Asbjørn Mohr , Gregersen Hans
Published: July 2008

The aim of this review is to describe the biomechanical, functional and sensory modelling work that can be used to integrate the physiological, anatomical and medical knowledge of the gastrointestinal (GI) system. The computational modelling in the GI tract was designed, implemented and evaluated using a series of information and communication technologies-based tools. These tools modelled the morphometry, biomechanics, functions and sensory aspects of the human GI tract. The research presented in this review is based on the virtual physiological human concept that pursues a holistic approach to representation of the human body. Such computational modelling combines imaging data, GI physiology, the gut–brain axis, geometrical and biomechanical reconstruction, and computer graphics for mechanical, electronic and pain analysis. The developed modelling will aid research and ensure that medical professionals benefit through the provision of relevant and precise information about a patient's condition. It will also improve the accuracy and efficiency of the medical procedures that could result in reduced cost for diagnosis and treatment.
A computational framework for modelling solid tumour growth
Authors: Lloyd Bryn A , Szczerba Dominik , Rudin Markus , Székely Gábor
Published: July 2008

The biology of cancer is a complex interplay of many underlying processes, taking place at different scales both in space and time. A variety of theoretical models have been developed, which enable one to study certain components of the cancerous growth process. However, most previous approaches only focus on specific aspects of tumour development, largely ignoring the influence of the evolving tumour environment. In this paper, we present an integrative framework to simulate tumour growth, including those model components that are considered to be of major importance. We start by addressing issues at the tissue level, where the phenomena are modelled as continuum partial differential equations. We extend this model with relevant components at the cellular or even sub-cellular level in a vertical fashion. We present an implementation of this framework, covering the major processes and treat the mechanical deformation due to growth, the biochemical response to hypoxia, blood flow, oxygenation and the explicit development of a vascular system in a coupled way. The results demonstrate the feasibility of the approach and its applicability to
in silico
studies of the influence of different treatment strategies (like the usage of novel anti-cancer drugs) for more effective therapy design.
Modelling thrombosis using dissipative particle dynamics method
Authors: Filipovic N , Kojic M , Tsuda A
Published: July 2008

Aim. Arterial occlusion is a leading cause of cardiovascular disease. The main mechanism causing vessel occlusion is thrombus formation, which may be initiated by the activation of platelets. The focus of this study is on the mechanical aspects of platelet-mediated thrombosis which includes the motion, collision, adhesion and aggregation of activated platelets in the blood. A review of the existing continuum-based models is given. A mechanical model of platelet accumulation onto the vessel wall is developed using the dissipative particle dynamics (DPD) method in which the blood (i.e. colloidal-composed medium) is treated as a group of mesoscale particles interacting through conservative, dissipative, attractive and random forces.

Methods. Colloidal fluid components (plasma and platelets) are discretized by mesoscopic (micrometre-size) particles that move according to Newton's law. The size of each mesoscopic particle is small enough to allow tracking of each constituent of the colloidal fluid, but significantly larger than the size of atoms such that, in contrast to the molecular dynamics approach, detailed atomic level analysis is not required.

Results. To test this model, we simulated the deposition of platelets onto the wall of an expanded tube and compared our computed results with the experimental data of Karinoet al. (Miscrovasc. Res.17, 238–269, 1977). By matching our simulations to the experimental results, the platelet aggregation/adhesion binding force (characterized by an effective spring constant) was determined and found to be within a physiologically reasonable range.

Conclusion. Our results suggest that the DPD method offers a promising new approach to the modelling of platelet-mediated thrombosis. The DPD model includes interaction forces between platelets both when they are in the resting state (non-activated) and when they are activated, and therefore it can be extended to the analysis of kinetics of binding and other phenomena relevant to thrombosis.
Isolation and Culture of Mouse Keratinocytes
Authors: Jones Jonathan C.R.
Published: July 2008

INTRODUCTION

This protocol describes the isolation of keratinocytes from pregnant bald mice. It can also be used for isolation of primary rat keratinocytes.
Identification of Differential Genes by Suppression Subtractive Hybridization: VI. Differential Hybridization with Tester and Driver DNA Probes
Authors: Rebrikov Denis V.
Published: July 2008

INTRODUCTION

Suppression subtractive hybridization (SSH) is one of the most powerful and popular methods for generating subtracted cDNA or genomic DNA libraries. This technique can be used to compare two mRNA populations and obtain cDNAs representing genes that are either overexpressed or exclusively expressed in one population as compared to another. It can also be used for comparison of genomic DNA populations. This protocol describes a method for screening a subtracted cDNA library by differential hybridization using (1) a tester-specific subtracted probe (forward-subtracted probe), (2) a driver-specific subtracted probe (reverse-subtracted probe), (3) a cDNA probe synthesized directly from tester mRNA (or tester genomic DNA), and (4) a cDNA probe synthesized directly from driver mRNA (or driver genomic DNA).
In Vitro Screening for Regulated Transcription Factors with Differential Display of DNA-Binding Proteins (DDDP)
Authors: Reinke Hans , Schibler Ueli
Published: July 2008

INTRODUCTION

Strict regulation of transcription factor activity is essential to establish and maintain gene expression. Eukaryotic cells control transcription factors at many different levels. Post-translational regulatory mechanisms (e.g., phosphorylation, nuclear translocation, multimerization, regulated degradation, etc.) play particularly important roles because they enable cells to respond to various intra- and extracellular stimuli quickly and without prior protein synthesis. However, extensive post-translational changes can make it difficult to identify differentially regulated transcription factors. Common genomic screening techniques such as DNA microarray analysis are unable to detect any mode of regulation beyond that of mRNA stability. This protocol describes the differential display of DNA-binding proteins (DDDP), which is based on the electrophoretic mobility shift assay (EMSA) and detects DNA-binding transcription factors, independent of the number or nature of regulatory steps required for activation. DDDP is an unbiased screening technique that can be used in any experimental system that uses concentrated protein extracts. A plasmid library containing random DNA sequences is constructed. This library is then used to generate radioactive DNA probes to test protein extracts from different sources in parallel for differentially regulated DNA-binding proteins. Plasmids corresponding to probes that display differential DNA-binding activity can be sequenced, and the binding sequence can be narrowed down in a two-step procedure. The corresponding transcription factors can then be identified by bioinformatic and/or biochemical methods.
Two Distinct Interacting Classes of Nuclear Envelope–Associated Coiled-Coil Proteins Are Required for the Tissue-Specific Nuclear Envelope Targeting ofArabidopsisRanGAP
Authors: Zhao Qiao , Brkljacic Jelena , Meier Iris
Published: July 2008

Ran GTPase plays essential roles in multiple cellular processes, including nucleocytoplasmic transport, spindle formation, and postmitotic nuclear envelope (NE) reassembly. The cytoplasmic Ran GTPase activating protein RanGAP is critical to establish a functional RanGTP/RanGDP gradient across the NE and is associated with the outer surface of the NE in metazoan and higher plant cells. Arabidopsis thaliana RanGAP association with the root tip NE requires a family of likely plant-specific nucleoporins combining coiled-coil and transmembrane domains (CC-TMD) and WPP domain–interacting proteins (WIPs). We have now identified, by tandem affinity purification coupled with mass spectrometry, a second family of CC-TMD proteins, structurally similar, yet clearly distinct from the WIP family, that is required for RanGAP NE association in root tip cells. A combination of loss-of-function mutant analysis and protein interaction data indicates that at least one member of each NE-associated CC-TMD protein family is required for RanGAP targeting in root tip cells, while both families are dispensable in other plant tissues. This suggests an unanticipated complexity of RanGAP NE targeting in higher plant cells, contrasting both the single nucleoporin anchor in metazoans and the lack of targeting in fungi and proposes an early evolutionary divergence of the underlying plant and animal mechanisms.
Analysis of Decomposability and Complexity for Design Problems in the Context of Decomposition
Authors: Chen Li , Li Simon
Published: July 2008

The current practice in problem decomposition assumes that (1) design problems can be rationally decomposed a priori and (2) decomposition can usefully result in complexity reduction a priori. However, this assumption is not always true in reality. In response to this concern, this paper introduces the notions of decomposability and complexity to problem decomposition. In particular, a full scale of decomposability analysis and complexity analysis in the context of decomposition are presented along with approaches and algorithms. These new analyses not only address the viability and validity of decomposition, but also help achieve an optimal number of sub-problems during decomposition, which is usually determined by trial and error or a priori. Further, a procedure that is able to combine these new analyses into our two-phase decomposition framework is described. This effort leads to an enhanced decomposition method that is able to find the most appropriate decomposition solution to a complex design problem.
Applications of RFID Technology and Smart Parts in Manufacturing
Authors: Zhekun Li , Gadh Rajit , Prabhu B. S.
Published: July 2008

Industrial and consumer applications of Radio Frequency Identification (RFID) are explored. The state-of-the-art and development in RFID technology is reviewed. A currently operative smart parts based manufacturing system is described which uses RFID as the key technology. The role of RFID in the emerging Wireless Internet Manufacturing field is highlighted.
A Multi-Agent Intelligent Environment for Rapid Assembly Design, Planning and Simulation
Authors: Zha Xuan F. , Li Ling L. , Lim Samuel Y. E.
Published: July 2008

This paper presents a knowledge-intensive concurrent integration framework for designing, planning, analysis and simulation of assemblies, which is built upon P/T nets and multi-agent systems in AI. In the paper, critical issues are addressed on the implementation of intelligent assembly modeling, analysis and design, planning and simulation using knowledge intensive P/T net models, e.g., knowledge modeling and acquisition, function-behavior-structure modeling, fuzzy relational database, case-based reasoning, and assembly design language, etc. The developed multi-agent intelligent environment, RAPID Assembly system, can process various types of knowledge in assembly design, process and task planning, and assembly system design and simulation so that intelligent design, planning and simulation can be implemented in a virtual environment. It assists designers and manufacturing engineers to design and evaluate the product and its assembly processes and assembly systems (e.g., assembly feasibility, sequences, trajectories, and execution strategies) without building physical prototypes. Design cases are provided to illustrate how the system works.
A Web-Based Process for Creating Parametric Cost Models for Product Design Trade Studies
Authors: Gue´rinot Alexandre E. , Roach Gregory M. , Cox Jordan J.
Published: July 2008

This paper proposes a method for creating a parametric cost model established on the foundation of the product design generator methodology to provide early estimates of production cost and manufacturing cycle-time during preliminary design. This is accomplished by capturing the manufacturing process and knowledge associated with the product and its production. The relationships between design decisions and manufacturing costs are explicitly exposed making the cost estimation process reusable and repeatable. Designers can now clearly assess the profitability of their design, identify appropriate trade-offs between engineering requirements and production costs, and alter the design accordingly.
Optimisation of Autonomous Threaded Fastenings Based on Non-Linear Least Square Method With GUIs
Authors: Klingajay Mongkorn , Wanathap Wuttipong
Published: July 2008

Threaded fastenings are a common assembly method, accounting for over a quarter of all assembly operations. They are especially popular because they permit easy disassembly for maintenance, repair, relocation and recycling. Screw insertions are typically carried out manually as it is a difficult operation to automate. There is very little published research on automating threaded fastenings, and most research on automated assembly focuses on the peg-in-hole assembly problem. Non-linear least square method was designed and employed to identify torque signature signals during online threaded fastening. Creating interactive simulations and graphical user interfaces became necessary as a visualization aid. This provides help and support for the user, allowing them to concentrate on the concept they are illustrating and to put emphasis on the monitoring process rather than the mechanics of running the program. This paper presents a Graphical User Interface (GUI) tool to accommodate and support threaded fastening operations used in assembly line industries. This tool was produced as interactive software with a convenient GUI in combination with the computing and graphics capability of MATLAB. It has applied to automated monitoring of threaded fastenings based-on an analytical model and on-line parameter estimation. The monitoring problem deals with predicting the integrity of the screw insertion process based on the torque vs. insertion angle curves generated during the insertions. A Non-linear Least Square Method (NLSM) is applied for estimation of four unknown parameters during a self-tapping screw insertion to be presented. It is shown that these parameters, required by the model, can be reliably estimated on-line. Experimental results are presented to validate the estimation procedure.
In Vitro Activity of Ceftobiprole against Pathogens from Two Phase 3 Clinical Trials of Complicated Skin and Skin Structure Infections
Authors: Amsler Karen M. , Davies Todd A. , Shang Wenchi , Jacobs Michael R. , Bush Karen
Published: July 2008

In phase 3 clinical trials for ceftobiprole treatment of complicated skin and skin structure infections, 1,219 gram-positive and 276 gram-negative aerobic baseline pathogens were identified. Ceftobiprole inhibited all staphylococcal isolates, including methicillin-resistant strains, at MICs of ≤4 μg/ml. Against
Enterobacteriaceae
and
Pseudomonas aeruginosa
isolates, the potency of ceftobiprole was similar to that of cefepime.
Anti-Human Immunodeficiency Virus Type 1 Activities of Antimicrobial Peptides Derived from Human and Bovine Cathelicidins
Authors: Wang Guangshun , Watson Karen M. , Buckheit Robert W.
Published: July 2008

From among 15 human cathelicidin LL-37-derived peptides, FK-13 was identified as the smallest peptide active against human immunodeficiency virus (HIV) and GI-20 had the highest therapeutic index, which was twice that of LL-37. BMAP-18, which is derived from bovine cathelicidin BMAP-27, possessed a therapeutic index similar to that of GI-20. Peptide sequence order, helical structures, and aromatic residues are important in HIV inhibition.
The marine algae of British Columbia, northern Washington, and southeast Alaska: division Rhodophyta (red algae), class Rhodophyceae, order Gigartinales, family Dumontiaceae, with an introduction to the order Gigartinales
Authors: Lindstrom Sandra C. , Scagel Robert F.
Published: July 2008

The benthic marine algal order Gigartinales (Rhodophyta) is introduced, and a key to the families found between Cross Sound, Alaska, and northern Washington is provided. The family Dumontiaceae is monographed. Ten of 16 currently recognized genera and 14 of some 48 recognized species are described and illustrated: Constantinea rosa-marina (Gmelin) Postels et Ruprecht, C. simplex Setchell, C. subulifera Setchell, Cryptosiphonia woodii (J. G. Agardh) J. G. Agardh, Dilsea California (J. G. Agardh) Kuntze, Dumontia contorta (Gmelin) Ruprecht, D. simplex Cotton, Farlowia mollis (Harvey et Bailey) Farlow et Setchell in Collins, Holden, et Setchell, Neodilsea borealis (Abbott) Lindstrom, N. natashae Lindstrom, Orculifilum denticulatum Lindstrom, Pikea californica Harvey, Thuretellopsis peggiana Kylin, and Weeksia coccinea (Harvey) Lindstrom. Farlowia compressa J. G. Agardh is recognized as a taxonomic synonym of F. mollis, and Pikea robusta Abbott as a taxonomic synonym of Pikea californica. Vegetative keys to the genera and species of the family are also included. Basionyms, synonyms, type specimens, type localities, and what is known about life histories, distributions, phenologies, and habitats of the species are given. Representative specimens are cited.
Effects of soil moisture and light intensity on the chasmogamous and cleistogamous components of reproductive effort of Dichanthelium clandestinum populations
Authors: Bell Timothy J. , Quinn James A.
Published: July 2008

Plants from six New Jersey populations of Dichanthelium clandestinum, a perennial grass with chasmogamous and cleistogamous flowers on the same individual, showed significant differences in their responses to decreasing light and soil moisture, but chasmogamous reproductive effort was always less than cleistogamous. In an experiment with three light treatments, populations were significantly different in biomass allocation to chasmogamous and cleistogamous reproduction and varied as to which light treatment produced the most significant difference between chasmogamous and cleistogamous allocation. In an experiment using soil moisture gradient boxes, chasmogamous reproductive effort remained relatively constant over the moisture gradient for all six populations; however, for five populations, percentage biomass allocation to cleistogamous reproduction was significantly lower at low soil moistures. The population responses formed a continuum from no difference in allocation to cleistogamy along the moisture gradient to a sharp drop in cleistogamous allocation at the lower end of the gradient to a relatively steady decrease in cleistogamous allocation with decreasing soil moisture. These results indicate genetically based differences in phenotypic plasticity and underscore the need to use more than one population of a species when research is conducted on variation in relative allocation to chasmogamous and cleistogamous reproduction along environmental gradients.
Isozyme variation in Trillium nivale (Liliaceae)
Authors: Bayer Randall J. , Duke John C. La , Crawford Daniel J.
Published: July 2008

Trillium nivale Riddell is an early-blooming spring ephemeral, which occurs in widely scattered, small populations throughout the eastern United States. Nine populations from previously glaciated regions of Ohio were surveyed by enzyme electrophoresis to determine the extent of the genetic variation present in the species. Twelve enzymes, coded by 25 putative genetic loci, were assayed during the study. Within populations, either very low amounts of genetic variation or total genetic uniformity were detected. The low levels of genetic variation are perhaps correlated with the reproductive biology of T. nivale.
Patterns of floral development in Agalinis and allies (Scrophulariaceae). I. Floral development of Agalinis fasciculata and A. tenuifolia
Authors: Kampny Christine M. , Canne-Hilliker Judith M.
Published: July 2008

The sequence of events and morphology of structures were similar during early floral development of Agalinis tenuifolia and A. fasciculata. The lateral-posterior calyx primordia were initiated first, followed by the middle-posterior primordium, and lastly by the two anterior primordia. The corolla primordia arose in an anterior to posterior succession, then the four stamen primordia were initiated simultaneously. Later the gynoecium originated as an oval-shaped ridge. Two depressions within it became locules, and the two sides of the cleaved ridge separating them met and formed a septum. A placenta formed in each locule and numerous ovules were initiated on it. Zygomorphy was apparent in the calyx, corolla, and androecium during the primordial stage. Organogenesis in the calyx was rapid so that the calyx lobes and tube were well formed before organogenesis of other floral parts. Except for those of the calyx, floral character states distinctive for each species were manifested late in development of the floral bud.
Potential for biological control of Cercosporidium personatum leafspot of peanuts by Dicyma pulvinata
Authors: Mitchell James K. , Smith Donald H. , Taber Ruth A.
Published: July 2008

The biology of Dicyma pulvinata (Berk. & Curt.) v. Arx, a mycoparasite of Cercosporidium personatum (Berk. & Curt.) Deighton, was investigated under both laboratory and field conditions. At 26 °C, conidia of D. pulvinata close to both hyphae and conidia of C. personatum germinated within 11–17 h. Visible signs of colonization of lesions of C. personatum by D. pulvinata appeared within 58–65 h (21–31.5 h leaf wetness). Dicyma pulvinata was an effective protectant when plants were exposed to continuous leaf wetness at 26 °C for 5 days. In field microplot studies, lesions of C. personatum were visibly colonized by both mutant and wild-type isolates of D. pulvinata within 4 days after applying their conidial suspensions. Environmental conditions during this 4-day period were 40 h leaf wetness, 60 h of 23–28 °C (optimal temperatures for growth of the wild-type isolate), and 17.31 cm rainfall.
Effects of medium composition and light on formation of apothecia and sclerotia by Pyronema domesticum
Authors: Moore-Landecker Elizabeth
Published: July 2008

Pyronema domesticum (Sow.) Sacc. was cultured in a 12 h light: 12 h dark cycle and in the dark on water agar; an inorganic salts medium (Claussen's agar); Claussen's agar supplemented with casein hydrolysate, biotin, thiamine, asparagine, glycine, or urea; and media containing a variety of natural materials, either supplemented or not with dextrose or another carbohydrate. Apothecial formation was favored by illumination, while sclerotial formation was favored by darkness. Maximum production of apothecia and sclerotia occurred on low-carbohydrate media supporting scant to moderate mycelial growth but was prevented on medium with a high carbohydrate concentration (20 g/L). Large numbers of well-developed apothecia formed on dilute media containing only inorganic nutrients (Claussen's agar), a small amount (3.0 g/L) of casein hydrolysate, or the extract from 20 g potatoes/L. Fewer incompletely developed apothecia formed on 2% water agar. Apothetical production was depressed or prevented by the addition of asparagine, glycine, urea, biotin, or thiamine to Claussen's agar. Sclerotia formed in maximum numbers on rabbit food agar, vegetable juice agar, and on dilute potato extract agar. Fewer sclerotia were produced on Claussen's agar.
Seasonal changes in the fruits of Viburnum opulus, a fleshy-fruited temperate-zone shrub
Authors: Jones Elise , Wheelwright Nathaniel T.
Published: July 2008

Certain temperate-zone plant species retain their fleshy fruits through the fall and winter. The production of "persistent fruits" has been interpreted as an adaptive reproductive strategy because plants can offer "low-investment" fruits when competition with other plants for seed dispersers is low. In theory fruits are defended chemically against fall pathogens, and palatability improves seasonally with cold-induced chemical changes. We studied the ecology of persistent fruits in Viburnum opulus (Caprifoliaceae), a fleshy-fruited temperate-zone shrub. Viburnum opulus fruits remained uneaten through the fall until most were removed, apparently by avian seed predators. Some shrubs retained fruits through May. Birds in the field and laboratory preferred all other fruit species tested over V. opulus. Palatability of V. opulus fruits to captive American Robins declined rather than improved throughout the winter, contrary to expectation. Tannins and pH remained constant, while sucrose concentration doubled over a 6-month period. Seeds regurgitated by robins in the spring germinated at similar rates as seeds processed the previous fall. Although V. opulus showed some of the theoretically expected adaptations for delayed seed dispersal (chemical defense, germination following spring dispersal), it did not show others (seasonal improvement in palatability). Plants with persistent fruits may depend on years of severe weather and food scarcity for seed dispersal.
Fluoride- and drought-induced structural alterations of mesophyll and guard cells in cotyledons of jack pine (Pinus banksiana)
Authors: Zwiazek J. J. , Shay Jennifer M.
Published: July 2008

Fluoride- and drought-induced injuries to mesophyll and guard cells were studied in jack pine (Pinus banksiana Lamb.) cotyledons, using light and electron microscopy techniques. Most early structural alterations were similar in cells of fluoride- and water-stressed seedlings. Both treatments resulted in an appearance of lipid material in the cytoplasm during early stages of injury, suggesting damage to the cell membranes. Treatment with sodium fluoride also resulted in deposition of starch in chloroplasts. Guard cells were more resistant to both stresses than mesophyll cells. Both metabolic injury and collapse of neighbouring cells may be responsible for the opening of stomata in wilting, fluoride-treated seedlings.
Phomopsis subordinaria and associated stalk disease in natural populations of Plantago lanceolate
Authors: Nooij Marianne P. de , Aa Huub A. van der
Published: July 2008

Natural populations of Plantago lanceolata L. can be infected by the fungus Phomopsis subordinaria (Desm.) Trav., which causes a stalk disease. Inoculation experiments revealed that the fungus needs a wound to enter the plant tissue. Symptoms of the disease in the field and from inoculation experiments in the greenhouse are described and the taxonomic position of the fungus is discussed. The pathogen could not be isolated from other plant species in heavily infected Pl. lanceolata populations and can be regarded as specialized on Pl. lanceolata. Other species of the genus Plantago differed considerably in their susceptibility to the disease. Comparison of Pl. lanceolata genotypes indicated that there is variation in susceptibility among host genotypes. Because the disease may reduce the production of viable seeds, the possibility of natural selection for resistance in the host is considered.
Viability of an ectomycorrhizal inoculum produced in a liquid medium and entrapped in a calcium alginate gel
Authors: Mauperin Ch. , Mortier F. , Garbaye J. , Tacon F. Le , Carr G.
Published: July 2008

Survival of Hebeloma crustuliniforme (Bulliard ex Fries) Quelet, grown in a liquid medium and subsequently entrapped in beads of calcium alginate, was tested under different conditions. Mycelium viability was not affected either by curing the beads for up to 22 h in 0.7 M CaCl2 or by the addition of either peat or bentonite to the alginate gel. Both peat and bentonite improved the water retention of the alginate gel, but only the incorporation of bentonite slowed down the rate at which moisture was lost by evaporation. At 4 °C the entrapped mycelium retained its viability for at least 5 months, provided that storage conditions remained humid. Partial drying of the beads reduced the effective storage time to a month. Emergence of hyphae from the beads was influenced by the presence of sterile soil extracts prepared from a podzolic soil, an acid brown earth, a mesotrophic brown earth, an eutrophic brown earth, and a rendzina. Hyphae grew out of all the beads containing peat irrespective of the type of soil extract but only grew out of those containing bentonite when they were on the mesotrophic brown earth extract. Hyphal emergence from beads containing neither peat nor bentonite appeared to be influenced by the pH of the extract, being better on those that were more acidic. Both sterile and nonsterile nursery soil supported growth of hyphae from the three types of bead, but on nonsterile soil, hyphae were not abundant and those that developed began to die off sooner than those on sterile soil.
Ultrastructure of Acremonium coenophialum, Acremonium lolii, and Epichloe typhina endophytes in host and nonhost Festuca and Lolium species of grasses
Authors: Siegel M. R. , Järlfors U. , Latch G. C. M. , Johnson M. C.
Published: July 2008

Ultrastructural studies were made of Acremonium fungal endophytes of tall fescue and perennial ryegrass and two isolates of Epichloe typhina. Hyphae of these fungi were observed in leaf sheaths of their natural host plant grown from infected seed and in artificially inoculated nonhost Festuca and Lolium species of grasses. Hyphae were also studied from fungal colonies grown on cellophane on potato dextrose agar. Crystalline inclusions were found in all endophyte–host combinations with the exceptions of E. typhina from perennial ryegrass in its own host and in a nonhost tall fescue, and Acremonium coenophialum in a nonhost perennial ryegrass. Tubular complexes were seen only in Acremonium lolii when growing in both host and in a non-host tall fescue. Three structures not seen before in endophytes (bundles of microtubules, 55 to 60 nm diameter "tubes," and bilayered cell walls) were found in E. typhina growing only in perennial ryegrass, its natural host. None of the distinguishing ultrastructural components described were found in hyphae grown in culture. Our observations suggest that endophytes express specific ultrastructural features only when they are grown in the grasses. However, it was not readily discernible what function the components serve and what role, if any, the natural versus the nonhost grass plays in the expression of endophyte ultrastructure.
Lipid metabolism of a Tertiary relic species, Kerguelen cabbage (Pringlea antiscorbutica)
Authors: Dorne Albert-Jean , Joyard Jacques , Douce Roland
Published: July 2008

The Kerguelen cabbage, Pringlea antiscorbutica R. Br., is a Tertiary relic Cruciferous species well adapted to the continuous cold conditions of this subantarctic archipelago. Each shoot exhibits all the steps of differentiation from embryonic leaves (1 mm) to mature leaves (30–40 cm). In the mature leaf, the chlorophyllous part is often reduced to a narrow peripheral strip, the chloroplasts being replaced progressively by amyloplasts toward the leaf center. This particular situation led us to compare the overall polar lipid and fatty acid composition from the green part of the mature leaves with those of the undifferentiated leaves, without chloroplasts. These lipid compositions are identical with those of all the C16:3 plants analyzed to date. The only feature characteristic of a chilling-resistant plant is the high percentage of saturated phosphatidylglycerol (16:0 + 16:1t). Polar lipid synthesis was followed by direct injection of [14C]acetate into the immature leaves. The incorporations of [14C]acetate into phosphatidylcholine and monogalactosyldiacylglycerol fatty acids closely parallel each other and there is no indication of fatty acid transfer from phosphatidylcholine to monogalactosyldiacylglycerol.
The systematics of the tube-dwelling diatom Nitzschia martiana and Nitzschia section Spathulatae
Authors: Lobban Christopher S. , Mann David G.
Published: July 2008

Nitzschia martiana (C. A. Ag.) Van Heurck is a tube-forming diatom of warmer waters. The tubes are rugose externally and contain bundles of long thin cells. The valves bear plain flaps of silica (conopea) externally, which arise near the central raphe system and extend over much of the valve surface; in the light microscope they can be detected as a pair of parallel lines alongside the raphe system. Beneath the conopea the valve arches inwards, so that tube-like canals are formed on the outside of the cell wall. There are no central raphe endings and the fibulae are rib-like. These characters, shown here to be shared by Nz. angularis Wm. Smith, indicate that Nz. martiana should be transferred into the section Spathulatae within the subgenus Nitzschia.
Composition and soil–environment analysis of prairies on Walpole Island, southwestern Ontario
Authors: Faber-Langendoen D. , Maycock P. F.
Published: July 2008

Extensive prairie communities on Walpole Island Indian Reserve in Lake St. Clair, southwestern Ontario, were sampled for vegetation and soil profile characteristics. Two hundred and fifty-two species were found in the 20 stands. Dominant grasses included Calamagrostis canadensis, Andropogon gerardii, Sorghastrum nutans, Panicum virgatum, Poa pratensis, and Spartina pectinata. Dominant forbs were Pycnanthemum virginianum, Liatris spicata, Fragaria virginiana, Lysimachia quadriflora, and Viola papilionacea. Stands were ordered along a recognized moisture–substrate gradient divided into four segments; dry-mesic sandy, mesic sandy loam, wet-mesic sandy loam, and wet loam. Many species showed preferences for certain regions of the gradient. Species richness ranged between 44 and 91 species per stand. The composition of the vegetation was summarized for the four segments, using prevalent species lists. Effectiveness of the direct gradient analysis was assessed by ordination using reciprocal averaging and polar ordination. Percent sand, percent organic matter, and depth of A horizon were significant correlates of the primary axis. Frequent burning of the prairie by the Indians has effectively maintained these prairies. The composition of the Walpole Island prairies is similar to those in Michigan, Illinois, and Wisconsin, forming part of the eastern tallgrass prairie.
Time-dependent deformation behaviour of Queenston shale
Authors: Lo K. Y. , Lee Y. N.
Published: July 2008

New methods for simultaneous measurement of three orthogonal strains in time-dependent deformation under several stress systems are described. Results of an extensive series of tests on oriented specimens of Queenston shale, with known magnitude and direction of in situ stress, are reported, together with tests on other shales from southern Ontario. It is found that over the stress range expected in field problems, the swelling behaviour is orthotropic and highly stress dependent. The application of stress in one principal direction not only suppresses the swelling in that direction but also reduces the swelling in the orthogonal directions. A method for representing this strongly nonlinear behaviour is described. Key words: shales, Queenston shale, time-dependent deformation, stress dependency, three-dimensional swelling.
A closed-form probabilistic solution for evaluating the bearing capacity of shallow foundations
Authors: Cherubini C.
Published: July 2008

A closed-form solution for the probabilistic evaluation of shallow foundation bearing capacity according to the model proposed by Terzaghi, as modified by Krizek, is described. A numerical example explains the method of computation. Key words: statistics, probability, ultimate bearing capacity, allowable bearing capacity, shallow foundations, friction angle, numerical methods.
Stand volume estimation from tree counts in the context of vertical line sampling
Authors: Lynch Thomas B.
Published: July 2008

Stand volume estimators are developed in the context of vertical line sampling that depend on counts of sample trees only, rather than on measurements of sample tree dimensions. These estimators are based on three commonly used individual tree volume equations: the constant form factor volume equation, the combined variable volume equation with negative intercept, and the combined variable volume equation with positive intercept. Fieldwork for each of the estimators involves comparison of the squared dbh's of trees that would qualify for selection in an ordinary vertical line sample with numbers chosen randomly from the interval bounded by zero and a fixed maximum squared dbh. Two of the estimators choose sample trees with probability exactly proportional to an individual tree volume equation.
The relationship between multiple leaders and mechanical and frost damage to the apical meristem of Scots pine seedlings
Authors: Holopainen Jarmo K.
Published: July 2008

The responses of young Scots pine seedlings to mechanical apical meristem damage before and after 4 nights exposure to minimum night temperatures of −2.2 and −6.7 °C in controlled environment growth chambers were compared with control seedlings that were subjected or not to apical meristem damage and exposed to a minimum night temperature of 12 °C. The feeding damage caused by Lygus bugs was simulated by piercing the apical meristem of young pine seedlings with a hypodermic syringe needle and injecting a small drop of distilled water into the wound. At −6.7 °C increased numbers of dead seedlings were found. The proportion of seedlings with multiple leaders greatly increased after piercing, and about half of the seedlings subjected to the apical meristem damage had multiple leaders. The proportion of seedlings with multiple leaders and the number of leader shoots per seedling did not differ among seedlings subjected to apical meristem damage before or after the frost exposure. Short and twisted primary needles occurred in the basal parts of the new shoots in the seedlings with multiple leaders. Seedlings with necrotic needles were most often found after exposure to the night temperature of −6.7 °C. Shoot dry weight and length were significantly lower in seedlings subjected to apical meristem damage after frost exposure than in seedlings subjected to apical meristem damage before frost exposure or to no frost exposure. The results suggest that an increased reduction in growth is to be expected if Lygus bug attacks occur on pine seedlings that already suffer from frost injury.