bluuebunny/crossref_metadata_2025 huggingface dataset:
Phycological studies in lakes Ontario, Erie, Huron, and Superior
Authors: Munawar M. , Munawar I. F.
Published: February 2008

An indepth phycological comparison is presented for lakes Ontario, Erie, Huron, and Superior, based on extensive lake-wide surveys carried out during the past 12 years. This comparison was achieved by the application of standard and consistent identification, enumeration, and data-processing techniques. The resulting species composition data are voluminous and present a broad picture of the phytoplankton assemblage. Our data base has enabled us to assess the long-term floristic changes, knowledge of which is lacking in the Great Lakes. The species composition reflects more or less the current trophic status of these lakes. The preponderance of nannoplankton and phytoflagellates is the subject of our current experimental research, which includes the fractionation of chlorophyll a and carbon-14 uptake, toxicity studies of heavy metals upon various size fractions of algae, and the role of microalgae and ultraplankton in the transfer of contaminants via zooplankton grazing. The need for phycological research in the Great Lakes is expanding with decreasing eutrophication and the increasing problems of contaminants. The recovery, rehabilitation, and preservation of these vital freshwaters are the primary concern of the continuing Canadian research program in the Great Lakes.
Light and transmission electron microscopy of English oak ectomycorrhizal short roots
Authors: Edwards H. H. , Gessner R. V.
Published: February 2008

The incorporation of caffeine in standard transmission electron microscope fixation procedures has allowed good preservation and embedment of ectomycorrhizal short roots of English oak (Quercus robur L.). In the mantle the most conspicuous structures are cystidia which radiate outwards from the surface. These conically shaped cells have knobs at their tips and thickened cell walls. The cystidia and other outer mantle cells contain many cytoplasmic constituents, whereas the inner mantle cells are nearly devoid of cytoplasm. The mantle cells are held together by an intercellular slime network. The Hartig net cells are filled with cytoplasm and contain numerous lipid droplets. Typical dolipore septa separate the cells; however, these cells have irregularly branched shapes. The host root tissue appears little altered by the presence of the fungal symbiont. However, the root cap consists of only a few cell layers. The apical meristem is functional as evidenced by the presence of newly divided cells and microtubules lining enlarging cells.
Decomposition of wild rice (Zizania aquatica) straw in two natural lakes of northwestern Ontario
Authors: Sain Pritam
Published: February 2008

Decomposition of wild rice (Zizania aquatica L.) straw was studied by placing 20 g of air-dried straw into 25 × 15 cm size nylon bags. Each set of five straw bags was covered in a fine aluminum screen to avoid damage from aquatic animals. The screens were placed on October 17, 1979, in West Bay representing a river system and in Lulu Lake, a typical shallow wild rice lake. After 350 days the total decomposition by weight of straw was 94 and 72% in West Bay and Lulu Lake, respectively. Release of nutrients from the straw was studied by calculating the percent loss of nutrients in each sampling period. A rapid release of nutrients was observed during the first 3 weeks followed by a slow release of nutrients thereafter. Total amounts of nutrients released after 350 days were about 98% potassium, 82% calcium, 81% phosphorus, 79% sulfur, 72% magnesium, and 57% nitrogen. The amount of nitrogen released and the carbon:nitrogen ratio of straw at the jointing stage of wild rice suggest that a major portion of the total nitrogen remains tied up in straw and may not become available for the next wild rice crop.
Ustilago spp. pathogenic on Aegilops. I. Ustilago aegilopsidis
Authors: Nielsen J. , Huang H.-Q.
Published: February 2008

The spore mass of Ustilago aegilopsidis is blackish brown; the spores germinate with the production of four primary sporidia on the promycelium, and infection of the host occurs through the coleoptiles of very young seedlings. Two collections of the fungus were pathogenic on Aegilops bicornis and Aegilops caudata, and one collection was also pathogenic on Aegilops cylindrica, but neither collection was pathogenic on 18 other Aegilops spp., eight Triticum spp., or two Hordeum spp. Experimental hybridization of the fungus with two smuts of barley, Ustilago nigra and Ustilago hordei, showed that U. aegilopsidis is very closely related to these fungi, and possibly conspecific with U. nigra.
The vascular flora of raised bogs in southeastern Labrador and its phytogeographic significance
Authors: Glaser Paul H. , Foster David R.
Published: February 2008

The vascular flora of raised bogs in southeastern Labrador is composed of only 26 species, which may be grouped into three different elements: wide-ranging arctic–boreal species, boreal species reaching their northeastern range limits in the forest–tundra transition, and boreal species reaching their range limits along the shores of Lake Melville. The striking impoverishment of the Labrador bog flora relative to those in Newfoundland and other parts of the Gulf of St. Lawrence region is apparently the result of the colder more continental climate of Labrador, which excludes from the regional bog flora the less hardy species of southern affinities.
Scanning electron microscope observations of internal symptoms of white elm following Ceratocystis ulmi infection and cerato-ulmin treatment
Authors: Takai Shozo , Hiratsuka Yasuyuki
Published: February 2008

Internal vascular symptoms induced by Ceratocystis ulmi infection and cerato-ulmin (CU) in white elm (Ulmus americana) were observed under a scanning electron microscope. Symptoms caused by CU were indistinguishable from those caused by C. ulmi. The main symptoms observed were (i) edemalike surface wall alteration, (ii) granular deposit, (iii) pit membrane heaving, (iv) smooth coating, (v) bubble and (or) tylose formation, (vi) rough coating, (vii) droplet formation, and (viii) vessel plugging with calluslike material. Internal symptoms appeared earlier in CU treated elms (as early as 2 h after treatment) than in C. ulmi infected elms (10 h after infection).
Developmental morphology of the gall of Urophora cardui (Diptera, Tephritidae) in the stems of Canada thistle (Cirsium arvense)
Authors: Lalonde R. G. , Shorthouse J. D.
Published: February 2008

Urophora cardui (L.) induces a large multichambered gall in stem tissues of Cirsium arvense (L.) Scop. Four phases in gall development are identified: initiation, growth, maturation, and dehiscence. Initiation begins when larvae tunnel from a shoot tip into the developing stem and change the polarity of pith and procambial tissues. These cells become gall parenchyma and proliferate during the growth phase. Procambial strands and gall laticifers appear among the gall parenchyma and the cells nearest the larvae differentiate into primary nutritive cells. In the maturation phase, gall tissues cease proliferating, procambial strands near the larvae give rise to secondary nutritive tissue, and all remaining gall parenchyma lignifies. Dehiscence occurs when callus tissues at the top of the gall degrade. Developmental studies utilizing insect-induced galls may increase our understanding of normal plant growth and development.
A Holocene pollen record of boreal forest history from the Travaillant Lake area, Lower Mackenzie River Basin
Authors: Ritchie J. C.
Published: February 2008

A 396-cm sediment sequence from SW Lake in the boreal woodland zone near Travaillant Lake, Northwest Territories, Canada, provides a Holocene record of pollen percentages and species interactions. Three local pollen assemblage zones are described: a Betula–Populus–Juniperus zone from 10 500 to 9000 years BP, a Picea–Betula zone from 9000 to 5100 years BP, and a Picea–Betula–Alnus zone from 5100 years BP to the present. The earliest vegetation recorded at this site is a mosaic of poplar groves, juniper and Shepherdia shrub, and fragmentary patches of tundra, replaced rapidly by spruce woodland at roughly 8500 years BP, dominated initially by Picea glauca. Picea mariana spread extensively between 8500 and 5000 years BP, probably as a function of increasing paludification. The present spruce-dominated vegetation was in place by 5000 years BP. Some changes in the pollen record can be explained by the Milankovitch early Holocene period of warmer summers followed by a cooling to modern conditions by 5000 years BP. Others require explanations in terms of edaphic factors or biological interactions among the main taxa.
Evidence for bicarbonate accumulation by Anacystis nidulans
Authors: Shelp Barry J. , Canvin David T.
Published: February 2008

Kinetic studies of photosynthetic O2 evolution as a function of pH were conducted to investigate the nature of the inorganic carbon used during photosynthesis by Anacystis nidulans. At pH 5, the apparent affinity for carbon during photosynthesis was similar in air-grown and high CO2 grown cells, but at alkaline pH, the apparent affinity was much greater in air-grown cells. The substrate concentration for half-maximum rates of photosynthesis in air-grown cells remained constant as a function of pH when the substrate was expressed as total carbon, suggesting that these cells were capable of using varying proportions of CO2 and [Formula: see text]. Photosynthesis in high CO2 grown algae appeared to be more dependent on CO2 over the pH range, indicating that CO2 was the predominant carbon species used, but [Formula: see text] uptake was also indicated. Internal inorganic carbon and photosynthetic carbon fixation in air-grown cells were determined at pH 8.5, using silicone oil centrifugation. Anacystis accumulated inorganic carbon in large excess of that in the external medium by a mechanism which is sensitive to inhibitors of energy metabolism and independent of concurrent carbon fixation; light was required to accumulate and maintain the internal carbon pool. The degree of accumulation was a function of the carbon concentration in the external medium; at 12 μM external carbon, the accumulation ratio was in excess of 100-fold, whereas at 4.76 mM, the ratio was only 5-fold. The rates of carbon transport were always sufficient to maintain photosynthesis. Carbon efflux rates approaching 40% of the influx rate were found at equilibrium internal carbon concentrations. Kinetic parameters of photosynthesis are discussed with reference to the known properties of algal ribulose bisphosphate (RuBP) carboxylase–oxygenase. It is concluded that the internal inorganic carbon pool serves as an intermediate for photosynthetic carbon fixation and that, if CO2 and [Formula: see text] are in equilibrium, the carbon accumulation at ambient CO2 and O2 is sufficient to suppress RuBP oxygenase activity.
Comparison of polypeptides in Ustilago spp. pathogenic on wheat, barley, and oats: a chemotaxonomic study
Authors: Kim W. K. , Rohringer R. , Nielsen J.
Published: February 2008

Detergent-soluble polypeptides were extracted from spores of several isolates of Ustilago spp. pathogenic on wheat, barley, and oats: U. tritici, U. nuda, U. nigra, U. hordei, U. avenae, and U. kolleri. These polypeptides were then separated by two-dimensional isoelectric focusing – polyacrylamide gel electrophoresis. Despite large differences in virulence, the three isolates of U. tritici virulent on wheat gave almost identical polypeptide patterns; an isolate virulent only on Aegilops spp. differed from these three by nine polypeptides. In U. nuda, two isolates had identical patterns, and four polypeptides varied between two other isolates. There were five or fewer differences in polypeptides between two isolates of each of U. nigra, U. hordei, U. avenae, and U. kolleri. This low level of intraspecific variation and the variability between closely related isolates preclude use of the present technique to differentiate isolates of unlike virulence of these six fungi. However, the species U. tritici and U. nuda differed by 47 polypeptides; this high level of interspecific variation supports the concept of treating these two pathogens as separate taxa. In contrast, the seedling-infecting smuts of barley and oats, U. nigra, U. hordei, U. avenae, and U. kolleri, showed only a difference in 13 polypeptides overall, with the last two differing by only one polypeptide. This limited interspecific variation supports the view that these four pathogens are very closely related and should be united under one taxon.
A technique for the isolation of intramatrical vesicles from vesicular–arbuscular mycorrhizae
Authors: Jabaji-Hare S. , Sridhara S. I. , Kendrick B.
Published: February 2008

A method for isolating the vesicles of vesicular–arbuscular mycorrhizal (VAM) fungi from within the roots of Allium porrum is presented. Colonized roots were homogenized with 0.3 M sucrose – 0.05 M NaHCO3 and filtered through cheesecloth. The supernatant was centrifuged (180 min, 82 000 g) on 1.3 M sucrose – 15 mM CsCl. Our tests yielded 46 000 vesicles per operator day, but the potential yield is limited only by the amount of root material available.
Leaf morphology of Claytonia virginica: racial and clinal variation
Authors: Doyle Jeff J.
Published: February 2008

Differences in average leaf length to width ratio are found to characterize the four chemical and cytological races of the geophytic spring ephemeral Claytonia virginica L. (Portulacaceae). Two races with wide leaves are mostly northern in distribution, while two other races having narrower leaves are predominantly southern. Within each race, a statistically significant north–south cline in leaf ratio is observed, mirroring the variation pattern observed for the species as a whole. Several ecological variables, including zenith angle of the sun and total solar radiation, also show north–south gradients when measured over the aboveground portion of the Claytonia virginica seasonal cycle and corrected for the time of flowering of the species at different latitudes. It is suggested that the clinal pattern of variation observed in the species has evolved in response to these environmental gradients.
Differentiation of raphide crystal idioblasts in isolated root cultures of Yucca torreyi (Agavaceae)
Authors: Kausch A. P. , Horner H. T.
Published: February 2008

Excised primary roots of Yucca torreyi (L.) were cultured in various media, and development of cortical raphide crystal idioblasts was observed. Idioblasts were consistently produced, required 24 h to differentiate fully from initials in isolated root cultures, and developed normally relative to those cells in intact roots. In vacuoles of idioblast initials, we observed an electron-dense amorphous material associated with paracrystalline bodies and membranous crystal chambers. Crystallization occurs within and is apparently controlled by crystal chamber membranes. After crystal production, crystalloplastids differentiate lobed regions, and cables of tubules and mucilage form within the central vacuole. Many aspects of Yucca idioblast development are common to differentiation of similar cells in intact organs of other plants. Based on our results, we believe that isolated root cultures of Yucca will be useful for future physiological investigations of oxalate metabolism and control of idioblast cytodifferentiation.
Comparison of plants derived from cuttings, node cultures, and ethyl methanesulfonate treated node cultures of bird's-foot trefoil (Lotus corniculatus)
Authors: Orshinsky B. R. , Tomes D. T.
Published: February 2008

Plants derived from node cultures of six genotypes of bird's-foot trefoil (Lotus corniculatus L.) were compared under field conditions with plants propagated by stem cuttings. Culture- and cutting-derived plants flowered at the same time, but for most other traits there was a strong interaction of genotype and propagation method. Plants from node culture were either similar to those from cuttings or else flowered at a lower node, were shorter, had reduced leaflet length:width ratio, lower pollen stainability, and (or) reduced seed yield. Number of stems per plant was increased for all genotypes and three genotypes had higher forage yield in the 1st year after node culture propagation. On average, this increase in yield and stem number persisted in the 2nd year. Treatment of node cultures with the mutagen ethyl methanesulfonate prior to plant regeneration delayed shoot development and induced a number of chlorophyll-deficient variants, but seldom affected any of the quantifiable plant traits. Most of the observed differences between cutting-derived and node culture derived plants were likely due to hormonal or epigenetic effects of the culture system.
The genus Thalassiosira: protoplast ultrastructure of the bipolar diatom Thalassiosira antarctica
Authors: Doucette Gregory J. , Burghardt Robert C. , Fryxell Greta A.
Published: February 2008

Disjunct populations of vegetative and resting stages of the bipolar diatom Thalassiosira antarctica Comber were examined for differences in protoplast ultrastructure. Analysis of clonal cultures from northern and southern populations revealed differences of uncertain taxonomic value between resting spores and no discernable differences between vegetative cells. Several unique ultrastructural features were noted in members of both populations. Most notable were complex corelike structures and intramembrane particle arrays, not previously observed in diatoms, occurring in certain vesicles. Also, dictyosomes exhibited an apparent reversal in polarity with respect to width and staining intensity of luminal spaces. These and other ultrastructural characteristics are considered in relation to protoplasts of other Thalassiosira species and diatoms in general.
Microscopie de la mycoflore des aiguilles de sapin (Abies alba). I. Thysanophora penicillioides
Authors: Gourbière François , Pepin Régis
Published: February 2008

Colonization of the needle litter of Abies alba Mill, by Thysanophora penicillioides (Roum.) Kendrick (Deuteromycete, Hyphomycete) has been studied by light and electron microscopy. Internal mycelium is mostly intercellular. The hyphae grow between collapsed cells of the parenchyma and form stromata in the epistomatal and substomatal cavities. Conidiophores arise from the stomates. Productivity is estimated to be 9 × 104 conidiophores per gram of needles. The development of the sclerotia is also described. Thysanophora penicillioides occupies the same ecological niche on Abies needles as Verticicladium trifidum Preuss on Pinus needles.
The phytogeography of Oxalis oregana in British Columbia
Authors: Ogilvie R. T. , Hebda R. J. , Roemer Hans L.
Published: February 2008

The occurrence of Oxalis oregana Nutt. in British Columbia is documented for five localities on the west coast of Vancouver Island and one locality in the Queen Charlotte Islands. The Oxalis populations grow in alluvial Tsuga heterophylla – Picea sitchensis – Thuja plicata – Polystichum munitum forest communities. Rhizomatous reproduction was recorded in all populations and flowering in two of the Vancouver Island populations. Three of the populations may be less than 3000 years old because they would have been inundated by higher sea levels during the middle Holocene. Possible introduction of plants by native people from the Olympic Peninsula, WA, is discussed.
Variation in bark characteristics of American beech (Fagus grandifolia)
Authors: Ostrofsky William D. , Blanchard Robert O.
Published: February 2008

Three distinct bark patterns of American beech (Fagus grandifolia Ehrh.) were exhibited by trees growing in naturally occurring forest stands in New Hampshire, U.S.A. Consistent differences in periderm anatomy were found to be associated with each particular bark pattern. Two patterns were typical of trees which maintained the first periderm in a superficial position. Another bark pattern is interpreted as being the result of normal rhytidome development, an uncommon occurrence in American beech.
Betula leaves and reproductive structures from the Middle Eocene of British Columbia, Canada
Authors: Crane Peter R. , Stockey Ruth A.
Published: February 2008

Fossil angiosperm leaves from the Middle Eocene Allenby Formation, at One Mile Creek near Princeton, southern British Columbia, are described and assigned to Betula leopoldae Wolfe & Wehr. Morphological details of associated infructescences, fruits, staminate inflorescences, and pollen are also very similar to those of extant Betula. Based on association evidence and independently determined systematic relationships, we suggest that the vegetative and reproductive structures were produced by a single fossil species. Combined information from all the organs available suggests that this Eocene Betula is most closely related to species in section Eubetula, subsection Costatae of the extant genus. Material from One Mile Creek constitutes the earliest fully documented record of the genus Betula based on both vegetative and reproductive structures. In the context of the fossil history of the Betulaceae as a whole, it indicates that the two extant genera of the Betuleae, Alnus and Betula, were clearly differentiated by the Middle Eocene.
Scanning electron microscopy of colonization of pear leaves by Pseudomonas syringae pv. syringae
Authors: Mansvelt E. Lucienne , Hattingh Martin J.
Published: February 2008

A scanning electron microscope study was undertaken to determine how Pseudomonas syringae pv. syringae van Hall colonizes the surface of pear leaves and enters leaf tissue. Bacteria multiplied on the leaf surface, particularly on trichomes and in depressions of the cuticular layer. Masses of bacteria were associated with leaf spots, which appeared 9 days after inoculation under favorable conditions. The pathogen entered leaf tissue through the open base of trichomes and through microscopic fissures in depressions of the cuticular layer. The resident phase of P. syringae pv. syringae probably survives on trichomes of pear leaves.
Scanning electron microscopy of pear blossom invasion by Pseudomonas syringae pv. syringae
Authors: Mansvelt E. Lucienne , Hattingh Martin J.
Published: February 2008

Colonization of 'Packham's Triumph' pear blossoms by Pseudomonas syringae pv. syringae van Hall was examined by scanning electron microscopy. All flower parts examined were colonized. One day after inoculation, numerous bacteria occurred between papillae and in the underlying tissue of stigmas, and on the surface of nectariferous tissue. Small colonies with distinct cells were seen on filaments. Masses of bacteria were present in receptacle tissue 2 days after inoculation. The pressure exerted by the expanding mass of bacteria within some regions of this tissue separated the cuticle from the epidermis. The pathogen probably entered internal tissue through natural openings present in the nectariferous region of the blossoms.
Long-term effects of 2, 4-D application on plants. I. Effects on the weed community in a wheat crop
Authors: Hume Larry
Published: February 2008

At Indian Head, Saskatchewan, there are plots that have been sprayed annually with 2,4-D for 36 years, since 1947. Herbicide application rates since 1969 in two sets of plots were 0.42 and 1.12 kg/ha, along with control plots with no application. The crop was wheat in a 3-year wheat – wheat – fallow rotation. The plots were monitored throughout the growing season in 1982 and 1983. The 14 most abundant species on these plots were grouped as susceptible, moderately tolerant, or highly tolerant to 2,4-D. These three groups differed significantly from each other with respect to the number of emerging seedlings during four separate time periods, survival to crop harvest, plant dry weight, and seed production. In all treatments, plant number and size decreased with emergence date, with only a few small plants emerging late in the season. Over the long term, 2,4-D use significantly reduced the number of plants of susceptible species, but it did not eliminate them. Reduced numbers of susceptible plants enabled the number of plants of highly tolerant species to increase. Even in plots treated with high rates of 2,4-D, plants of the susceptible species, Chenopodium album L. and Thlaspi arvense L., were still as abundant as those of any other species group. The overall effect of 2,4-D application was to reduce the difference in performance of susceptible and tolerant species, resulting in changes in quantitative aspects of community structure. No new major species has become established since 1947 as a result of 2,4-D application.
Effects of continuous combined nitrogen supply on symbiotic dinitrogen fixation of faba bean and pea inoculated with different rhizobial isolates
Authors: Chalifour François-P. , Nelson Louise M.
Published: February 2008

Combined nitrogen (N) has adverse effects on virtually all stages of the Rhizobium–legume symbiosis. Tolerance to combined N varies among legume hosts and rhizobial isolates, but the contribution of each symbiotic partner is not well established. The effects of combined N were studied in faba bean (Vicia faba L.) and pea (Pisum sativum L.), using the same Rhizobium leguminosarum isolates for both hosts. In one experiment, faba bean and pea were inoculated individually with four rhizobial isolates and grown for 28 days in the continuous presence of 0, 2.5, 5.0, or7.5 mol m−3 NH4NO3. For each isolate, faba bean was consistently more tolerant to combined N than pea as shown by significantly smaller rates of decrease in N2-fixing activity (acetylene reduction) in faba bean than in pea. The results were substantiated by those of a similar experiment in which increasing levels of 15N-labeled [Formula: see text] (5, 10, or 15 mol m−3) were supplied continuously to faba bean and pea inoculated individually with two rhizobial isolates. Comparisons of the different symbioses based on the proportion of total plant N derived from N2 fixation confirmed the conclusions reached using acetylene reduction activities.
The taxonomy of the Viola nuttallii complex
Authors: Fabijan D. M. , Packer J. G. , Denford K. E.
Published: February 2008

Morphological, cytological, and phytochemical data were incorporated into numerical and statistical analyses to produce a revision of Viola subsection Nuttallianae. A basic chromosome number of x = 6 was confirmed for this polyploid complex, which includes five species: V. vallicola, 2n = 12; V. tomentosa, 2n = 12; V. nuttallii, 2n = 24; V. praemorsa, 2n = 36 and 48; and V. bakeri, 2n = 48. Departures from recent authors include the recognition of two varieties in V. vallicola, vallicola and major (Hook.) Fabijan, based on flavonoid chemistry and distribution. Viola praemorsa is envisaged as embracing a wide range of morphological and chemical diversity, the extremes of which are recognized as the subspecies praemorsa, flavovirens (Pollard) Fabijan, and linguaefolia. In the absence of significant morphological or distributional differences between the V. linguaefolia and V. praemorsa subspecies major (sensu Baker and Clausen) and oregona, these three previously recognized taxa are included in subspecies linguaefolia. Based on cytological, morphological, and flavonoid data presented here, possible phylogenetic relationships are discussed.
Loss of organic matter, elements, and organic fractions in decomposing Eucalyptus microcarpa leaf litter
Authors: Maheswaran J. , Attiwill P. M.
Published: February 2008

The losses of organic matter, elements and organic fractions during the decomposition of Eucalyptus microcarpa Maiden leaf litter were measured in litterbags. The concentrations of nitrogen and phosphorus in litter increased for most of the decomposition period. At the end of 15 months the amounts of elements lost were in the order K > Na > Mg > P > N >Ca. A simple method to determine the different organic fractions according to the degree of decomposability and using a small quantity of litter (0.1 – 0.5 g) was developed. The mass loss during the initial 3 months was most closely related to the amount of light organic fraction in the litter, while during the final 12 months the mass loss was most closely related to the harder organic fractions in the litter.
Immunocytochemical localization of pectinesterases in hyphae of Phytophthora infestans
Authors: Förster Helga , Mendgen Kurt
Published: February 2008

Evidence for the localization of extracellular pectinesterases was obtained in hyphae of Phytophthora infestans with the antibody – protein A – gold technique. Hyphae were fixed in 1% formaldehyde and 0.5% glutaraldehyde, and the immunocytochemical localization was done on ultrathin sections of tissue embedded at low temperature in Lowicryl K4M. Gold particles were mainly present over three different types of vesicles and over dictyosomes. In older parts of the hyphae, the plasma membrane was heavily labeled. This might suggest that the hyphal cell wall in subapical regions is not as permeable as in the hyphal tips.
Seasonal variation of cold resistance in Malus woody tissue as determined by differential thermal analysis and viability tests
Authors: Ketchie D. O. , Kammereck R.
Published: February 2008

Differential thermal analyses, 2,3,5-triphenyltetrazolium chloride stain, electrical conductance, and whole tree freezing test measurements were performed on ‘Golden Delicious’ apple (Malus domestica Borkh.) to monitor annual variations in cold resistance and compare test responses. A distinct pattern of exotherms was observed by thermal analyses throughout the year. The first exotherm at −6 to −9 °C represented the extracellular water. The second and third exotherms varied with the time of year and were at −10 to −39 °C, representing pith cells and xylem tissue, respectively. The lowest temperature exotherm occurred at −35 to −40 °C. Tetrazolium tests, performed at temperatures corresponding to each exotherm, showed that the cell damage occurred in the shoot interior and spread radially outward, with the secondary xylem being the most cold resistant. Comparison of electrical conductance with the xylem exotherm showed a nonlinear relationship. Stress tests on trees under controlled conditions showed that the temperature at the xylem exotherm was critical to the survival of the tree. Both the tetrazolium test and tree stress tests indicated that the lowest temperature exotherm could not be used as a measure of cold resistance. The possibility that thermal analysis is an improved measure of cold resistance is discussed.
CLONES CLOSED UNDER CONJUGATION I: CLONES WITH CONSTANTS
Authors: KEARNES KEITH A. , SZENDREI ÁGNES
Published: February 2008

We show that if G ≤ S A is a permutation group on a finite set A satisfying |A| ≥ 3, then the set of G-closed clones on A that contain all constant operations is finite iff G = S A, A A, AGL(1,5) (|A| = 5), PSL(2,5) (|A| = 6), PGL(2,5) (|A| = 6), PGL(2,7) (|A| = 8), PGL(2,8) (|A| = 9), or PΓL(2,8) (|A| = 9).
WEAKLY P-SMALL NOT P-SMALL SUBSETS IN GROUPS
Authors: BANAKH TARAS , LYASKOVSKA NADIA
Published: February 2008

Answering a question of Dikranjan and Protasov we prove that each infinite group G contains a weakly P-small subset A ⊂ G which is not P-small. This means that for every n there are n pairwise disjoint translation copies of A in G but there is no infinitely many such disjoint copies.
A MEALY MACHINE WITH POLYNOMIAL GROWTH OF IRRATIONAL DEGREE
Authors: BARTHOLDI LAURENT , REZNYKOV ILLYA I.
Published: February 2008

We consider a very simple Mealy machine (two nontrivial states over a two-symbol alphabet), and derive some properties of the semigroup it generates. It is an infinite, finitely generated semigroup, and we show that the growth function of its balls behaves asymptotically like ℓα, for [Formula: see text]; that the semigroup satisfies the identity g6 = g4; and that its lattice of two-sided ideals is a chain.
ENDOMORPHISMS OF RELATIVELY HYPERBOLIC GROUPS
Authors: BELEGRADEK IGOR , SZCZEPAŃSKI ANDRZEJ
Published: February 2008

We generalize some results of Paulin and Rips-Sela on endomorphisms of hyperbolic groups to relatively hyperbolic groups, and in particular prove the following.

• If G is a nonelementary relatively hyperbolic group with slender parabolic subgroups, and either G is not co-Hopfian or Out (G) is infinite, then G splits over a slender group.

• If H is a nonparabolic subgroup of a relatively hyperbolic group, and if any isometric H-action on an ℝ-tree is trivial, then H is Hopfian.

• If G is a nonelementary relatively hyperbolic group whose peripheral subgroups are finitely generated, then G has a nonelementary relatively hyperbolic quotient that is Hopfian.

• Any finitely presented group is isomorphic to a finite index subgroup of Out (H) for some group H with Kazhdan property (T). (This sharpens a result of Ollivier–Wise).
ALGORITHMIC PROBLEMS ON INVERSE MONOIDS OVER VIRTUALLY FREE GROUPS
Authors: DIEKERT VOLKER , ONDRUSCH NICOLE , LOHREY MARKUS
Published: February 2008

Let G be a finitely generated virtually-free group. We consider the Birget–Rhodes expansion of G, which yields an inverse monoid and which is denoted by IM (G) in the following. We show that for a finite idempotent presentation P, the word problem of a quotient monoid IM (G)/P can be solved in linear time on a RAM. The uniform word problem, where G and the presentation P are also part of the input, is EXPTIME-complete. With IM (G)/P we associate a relational structure, which contains for every rational subset L of IM (G)/P a binary relation, consisting of all pairs (x,y) such that y can be obtained from x by right multiplication with an element from L. We prove that the first-order theory of this structure is decidable. This result implies that the emptiness problem for Boolean combinations of rational subsets of IM (G)/P is decidable, which, in turn implies the decidability of the submonoid membership problem of IM (G)/P. These results were known previously for free groups, only. Moreover, we provide a new algorithmic approach for these problems, which seems to be of independent interest even for free groups.

We also show that one cannot expect decidability results in much larger frameworks than virtually-free groups because the subgroup membership problem of a subgroup H in an arbitrary group G can be reduced to a word problem of some IM (G)/P, where P depends only on H. A consequence is that there is a hyperbolic group G and a finite idempotent presentation P such that the word problem is undecidable for some finitely generated submonoid of IM (G)/P. In particular, the word problem of IM (G)/P is undecidable.
A THEOREM ON MATRIX GROUPS
Authors: PAPISTAS A. I.
Published: February 2008

Let K be a principal ideal domain, and An, with n ≥ 3, be a finitely generated torsion-free abelian group of rank n. Let Ω be a finite subset of KAn\{0} and U(KAn) the group of units of KAn. For a multiplicative monoid P generated by U(KAn) and Ω, we prove that any generating set for [Formula: see text] contains infinitely many elements not in [Formula: see text]. Furthermore, we present a way of constructing elements of [Formula: see text] not in [Formula: see text] for n ≥ 3. In the case where K is not a field the aforementioned results hold for n ≥ 2.
NAMBU–GOLDSTONE MODES IN GRAVITATIONAL THEORIES WITH SPONTANEOUS LORENTZ BREAKING
Authors: BLUHM ROBERT
Published: February 2008

Spontaneous breaking of Lorentz symmetry has been suggested as a possible mechanism that might occur in the context of a fundamental Planck-scale theory, such as string theory or a quantum theory of gravity. However, if Lorentz symmetry is spontaneously broken, two sets of questions immediately arise: What is the fate of the Nambu–Goldstone (NG) modes, and can a Higgs mechanism occur? A brief summary of some recent work looking at these questions is presented here.
NATURAL INFLATION: STATUS AFTER WMAP THREE-YEAR DATA
Authors: FREESE KATHERINE , KINNEY WILLIAM H. , SAVAGE CHRISTOPHER
Published: February 2008

Inflationary cosmology, a period of accelerated expansion in the early Universe, is being tested by cosmic microwave-background measurements. Generic predictions of inflation have been shown to be correct, and in addition individual models are being tested. The model of natural inflation is examined in light of recent three-year data from the Wilkinson Microwave Anisotropy Probe and shown to provide a good fit. The inflaton potential is naturally flat due to shift symmetries, and in the simplest version is V(ϕ) = Λ4 [1 ± cos (Nϕ/f)]. The model agrees with WMAP3 measurements as long as f > 0.7 m Pl (where m Pl = 1.22 × 1019 GeV ) and Λ ~ m GUT . The running of the scalar spectral index is shown to be small — an order of magnitude below the sensitivity of WMAP3. The location of the field in the potential when perturbations on observable scales are produced is examined; for f > 5 m Pl , the relevant part of the potential is indistinguishable from a quadratic, yet has the advantage that the required flatness is well motivated. Depending on the value of f, the model falls into the large field (f ≥ 1.5 m Pl ) or small field (f < 1.5 m Pl ) classification scheme that has been applied to inflation models. Natural inflation provides a good fit to WMAP3 data.
ATOMIC CLOCKS AND PRECISION MEASUREMENTS
Authors: GIBBLE KURT
Published: February 2008

We present a review of our clock science conducted under the NASA Microgravity Fundamental Physics program. Our work has led to the development of rubidium atomic clocks, designs for ground- and space-based clocks that juggle atoms to achieve ultrahigh stability and accuracy, improved microwave cavities for atomic clocks, and elucidation of new systematic errors such as the atomic recoil from microwave photons. High stability clocks can be used for precise tests of fundamental physics and accurate deep-space navigation.
ELECTRON ELECTRIC DIPOLE MOMENT EXPERIMENT WITH SLOW ATOMS
Authors: GOULD HARVEY
Published: February 2008

Discovering an electron electric dipole moment (e-EDM) would uncover new physics requiring an extension of the Standard Model. e-EDMs, large enough to be discovered by new experiments are now common predictions in extensions of the Standard Model, including extensions that describe baryogenesis, dark matter, and neutrino mass.

A cesium slow-atom e-EDM experiment (which is similar to an atomic clock) can improve the sensitivity to the e-EDM. And, as with an atomic clock, it could be more sensitive in microgravity than on Earth. As a first step an Earth-based demonstration Cs fountain e-EDM experiment has been carried out at LBNL.
ADVANCED HYBRID SQUID MULTIPLEXER CONCEPT FOR THE NEXT GENERATION OF ASTRONOMICAL INSTRUMENTS
Authors: HAHN I. , DAY P. , BUMBLE B. , LEDUC H. G.
Published: February 2008

The Superconducting Quantum Interference Device (SQUID) has been used and proposed often to read out low-temperature detectors for astronomical instruments. A multiplexed SQUID readout for currently envisioned astronomical detector arrays, which will have tens of thousands of pixels, is still challenging with the present technology. We present a new, advanced multiplexing concept and its prototype development that will allow for the readout of 1,000–10,000 detectors with only three pairs of wires and a single microwave coaxial cable.
OPTICAL CLOCKS AND FREQUENCY METROLOGY FOR SPACE
Authors: KLEIN HUGH
Published: February 2008

Optical frequency standards and femtosecond comb measurement capabilities now rival and in some cases exceed those of microwave devices, with further improvements anticipated. Opportunities are emerging for the application of highly stable and accurate optical frequency devices to fundamental physics space science activities, and the European Space Agency (ESA) has recently commissioned studies on different aspects of optical clocks in space. This paper highlights some examples, including the difficulty of comparing very accurate terrestrial clocks at different locations due to fluctuations of the geoid; by locating a primary frequency standard in space, one could avoid geoid-related gravitational redshifts.
TIME, CLOCKS AND FUNDAMENTAL PHYSICS
Authors: LÄMMERZAHL CLAUS , DITTUS HANSJÖRG
Published: February 2008

Time is the most basic notion in physics. Correspondingly, clocks are the most basic tool for the exploration of physical laws. We show that most of the fundamental physical principles and laws valid in today's description of physical phenomena are related to clocks. Clocks are an almost universal tool for exploring the fundamental structure of theories related to relativity. We describe this structure and give examples where violations of standard physics are predicted and, thus, may be important in the search for a theory of quantum gravity. After stressing the importance for future precise clock experiments to be performed in space, we refer to the OPTIS mission, to which another article in this issue is devoted. It is also outlined that clocks are not only important for fundamental tests but at the same time are also indispensable for practical purposes like navigation, Earth sciences, metrology, etc.
ON ARTIFICIAL BLACK HOLES
Authors: LEONHARDT ULF , PHILBIN THOMAS G.
Published: February 2008

We explain some of the main motivations for creating laboratory analogs of horizons (artificial black holes). We present a concise derivation of the Hawking effect, the quantum radiation of black holes, using a simple analog model.
DETECTING LORENTZ INVARIANCE VIOLATIONS IN THE 10-20 RANGE
Authors: LIPA J. A. , WANG SUWEN , NISSEN J. , KASEVICH M. , MESTER J.
Published: February 2008

In recent years the possibility has been raised of Lorentz invariance violations arising from physics beyond the Standard Model. Some of these effects manifest themselves as small anisotropies in the velocity of light, c. By comparing the resonant frequencies of cavity modes with different spatial alignments, limits on the order δ c/c < 10-15 have been set and some further improvement can be expected. However, the largest Lorentz violations originating at the Planck scale are expected to manifest themselves as a fractional frequency variation at the 10-17 level in the absence of suppression factors. Space experiments have been proposed to approach the 10-18 level. Here we explore the possibilities for pushing further and show that it is possible in principle to reach well into the 10-20 range with existing technology. This could be done in a very quiet cryogenic environment, such as the drag-free orbiter being developed for the Satellite Test of the Equivalence Principle (STEP).
PROBING RELATIVITY USING SPACE-BASED EXPERIMENTS
Authors: RUSSELL NEIL
Published: February 2008

An overview of space tests searching for small deviations from special relativity arising at the Planck scale is given. Potential high-sensitivity space-based experiments include ones with atomic clocks, masers, and electromagnetic cavities. We show that a significant portion of the coefficient space in the Standard Model extension, a framework that covers the full spectrum of possible effects, can be accessed using space tests. Some remarks on Lorentz violation in the gravitational sector are also given.
COHERENT ACCELERATION OF MATERIAL WAVE PACKETS
Authors: SAIF FARHAN , MEYSTRE PIERRE
Published: February 2008

We study the quantum dynamics of a material wave packet bouncing off a modulated atomic mirror in the presence of a gravitational field. We find the occurrence of coherent accelerated dynamics for atoms. The acceleration takes place for certain initial phase space data and within specific windows of modulation strengths. The realization of the proposed acceleration scheme is within the range of present day experimental possibilities.
CMB POLARIZATION: THE NEXT DECADE
Authors: WINSTEIN B.
Published: February 2008

I review the exciting science that awaits cosmologists in precision measurements of the cosmic microwave background radiation, particularly its polarization. The conclusions of the Interagency Taskforce ("Weiss Panel") will also be presented. I conclude with an update based primarily on the new WMAP results from their three-year analysis.
LIGHT SUPERCONDUCTING STRINGS IN THE GALAXY
Authors: FERRER FRANCESC , VACHASPATI TANMAY
Published: February 2008

Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 keV gamma ray line emission from the bulge, which requires an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma ray background. Here we suggest that light superconducting strings could be the source of the observed 511 keV emission. The associated particle physics, at the ~ 1 TeV scale, is within the reach of planned accelerator experiments, while the distinguishing spatial distribution, proportional to the galactic magnetic field, could be mapped by SPI or by future, more sensitive satellite missions.
PRECISION MEASUREMENT BASED ON ULTRACOLD ATOMS AND COLD MOLECULES
Authors: YE JUN , BLATT SEBASTIAN , BOYD MARTIN M. , FOREMAN SETH M. , HUDSON ERIC R. , IDO TETSUYA , LEV BENJAMIN , LUDLOW ANDREW D. , SAWYER BRIAN C. , STUHL BENJAMIN , ZELINSKY TANYA
Published: February 2008

Ultracold atoms and molecules provide ideal stages for precision tests of fundamental physics. With microkelvin neutral strontium atoms confined in an optical lattice, we have achieved a fractional resolution of 4 × 10-15 on the 1S0–3P0 doubly forbidden 87 Sr clock transition at 698 nm. Measurements of the clock line shifts as a function of experimental parameters indicate systematic errors below the 10-15 level. The ultrahigh spectral resolution permits resolving the nuclear spin states of the clock transition at small magnetic fields, leading to measurements of the 3P0 magnetic moment and metastable lifetime. In addition, photoassociation spectroscopy performed on the narrow 1S0–3P1 transition of 88 Sr shows promise for efficient optical tuning of the ground state scattering length and production of ultracold ground state molecules. Lattice-confined Sr 2 molecules are suitable for constraining the time variation of the proton–electron mass ratio. In a separate experiment, cold, stable, ground state polar molecules are produced from Stark decelerators. These cold samples have enabled an order-of-magnitude improvement in the measurement precision of ground state, Λ doublet microwave transitions in the OH molecule. Comparing the laboratory results to those from OH megamasers in interstellar space will allow a sensitivity of 10-6 for measuring the potential time variation of the fundamental fine structure constant Δα/α over 1010 years. These results have also led to improved understandings of the molecular structure. The study of the low magnetic field behavior of OH in its 2Π3/2 ro-vibronic ground state precisely determines a differential Landé g factor between opposite parity components of the Λ doublet.