bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of T- and B-Lymphocyte Turnover in a Natural Host of Simian Immunodeficiency Virus
Authors: Kaur Amitinder , Di Mascio Michele , Barabasz Amy , Rosenzweig Michael , McClure Harold M. , Perelson Alan S. , Ribeiro Ruy M. , Johnson R. Paul
Published: November 2007

Increased lymphocyte turnover is a hallmark of pathogenic lentiviral infection. To investigate perturbations in lymphocyte dynamics in natural hosts with nonpathogenic simian immunodeficiency virus (SIV) infection, the nucleoside analog bromodeoxyuridine (BrdU) was administered to six naturally SIV-infected and five SIV-negative sooty mangabeys. As a measure of lymphocyte turnover, we estimated the mean death rate by fitting a mathematical model to the fraction of BrdU-labeled cells during a 2-week labeling and a median 10-week delabeling period. Despite significantly lower total T- and B-lymphocyte counts in SIV-infected sooty mangabeys than in SIV-negative mangabeys, the turnover rate of B lymphocytes and CD4+and CD8+T lymphocytes was not increased in the SIV-infected animals. A small, rapidly proliferating CD45RA+memory subset and a large, slower-proliferating CD45RA−central memory subset of CD4+T lymphocytes identified in the peripheral blood of sooty mangabeys also did not show evidence of increased turnover in the context of SIV infection. Independently of SIV infection, the turnover of CD4+T lymphocytes in sooty mangabeys was significantly higher (P< 0.01) than that of CD8+T lymphocytes, a finding hitherto not reported in rhesus macaques or humans. The absence of aberrant T-lymphocyte turnover along with an inherently high rate of CD4+T-lymphocyte turnover may help to preserve the pool of central memory CD4+T lymphocytes in viremic SIV-infected sooty mangabeys and protect against progression to AIDS.
Gag-Processing Defect of Human Immunodeficiency Virus Type 1 Integrase E246 and G247 Mutants Is Caused by Activation of an Overlapping 5′ Splice Site
Authors: Mandal Dibyakanti , Feng Zehua , Stoltzfus C. Martin
Published: November 2007

We have previously described several human immunodeficiency virus type 1 (HIV-1) mutants that are characterized by an excessive-RNA-splicing phenotype and reduced virus particle production. In one of these mutants (NLD2up), the sequence of 5′ splice site D2 was changed to a consensus splice donor site. This splice site overlaps the HIV-1 integrase reading frame, and thus, the NLD2up mutant also bears a G-to-W change at amino acid 247 of the integrase. A previously described E-to-K mutant at position 246 of the C-terminal domain of the integrase, which resulted in a G-to-A mutation at the +3 position of overlapping splice donor D2 (NLD2A3), was also shown to affect virus particle production and Gag protein processing. By using second-site mutations to revert the excessive-splicing phenotype, we show that the effects on Gag protein processing and virus particle production of both the NLD2up and NLD2A3 mutants are caused by excessive viral RNA splicing due to the activation of the overlapping 5′ splice site and not to the changes in the integrase protein. Both integrase protein mutations, however, are lethal for virus infectivity. These studies suggest that changes in the usage of overlapping splice sites may be a possible alternative explanation for a defective virus phenotype resulting from changes in protein-coding sequences or in the nucleotide sequence during codon optimization.
Moulds, bacteria and cancer among Finns: an occupational cohort study
Authors: Laakkonen A , Verkasalo P K , Nevalainen A , Kauppinen T , Kyyrönen P , Pukkala E I
Published: November 2007

Background:

Some environmental moulds and bacteria produce carcinogenic toxins.

Aim:

To study associations between work-related exposure to moulds and bacteria and cancers in Finland.

Methods:

A cohort of all economically active Finns in the population census in 1970 were followed-up for 30 million person-years. Subsequent cancer cases were identified through record linkage with the Finnish Cancer Registry. Observed and expected numbers of cancer cases were calculated by occupation, sex, birth cohort and period of observation. Exposures to moulds of agricultural and industrial origin and to bacteria of non-human origin were estimated with the Finnish Job–Exposure Matrix.

Results:

Men with the highest mould and bacterial exposure had a reduced relative risk for lung cancer (RR 0.7, 95% CI 0.6 to 0.9 for moulds and RR 0.9, 95% CI 0.8 to 1.0 for bacteria). Women in the highest mould and bacterial exposure category had RRs of 3.1 (95% CI 1.0 to 9.2) and 2.6 (95% CI 1.5 to 4.7) for cervical cancer, respectively. The respective RRs for lip cancer were 2.4 (95% CI 1.2 to 5.1) and 1.6 (95% CI 1.2 to 2.2).

Conclusions:

Exposures at the investigated concentrations to either moulds or bacteria are unlikely to be major risk factors of cancer, although suggestions of risk increases were observed for some cancer types. It has been suggested previously that the decreased risk for lung cancer is due to the protective effect of endotoxins.
Rileya, a new genus of Coelomycetes
Authors: Funk A.
Published: November 2007

Rileya nov. gen. (Coelomycetes) is characterized by thick-walled plectenchymatous pycnidia, hypha-like, branched conidiophores, and holoblastic, distoseptate conidia with a simple apical appendage produced holoblastically from the inner wall. A single species, R. piceae, is described from Picea sitchensis (Bong.) Carr. in coastal British Columbia, Canada.
Seasonal changes in the standing crop of an epilithic algal population on the north shore of Great Slave Lake
Authors: Moore James W.
Published: November 2007

Seasonal changes in the density of epilithic algae were determined from June 1975 to November 1976 at three sites on the north shore of Great Slave Lake. Densities increased rapidly in May immediately after the disappearance of ice, showed only small fluctuations during the summer, and waned during October. Microscopic algae, mainly Fragilaria capucina, Gomphonema olivaceum, G. ventricosa, Cymbella ventricosa, and other diatoms, reached peak abundance (2 × 109 μm3/cm2) on irregular occasions (July, September, October) throughout the growing season. However, filamentous algae, mainly Ulothrix zonata, reached maximum densities (60 mg/cm2 dry weight) during July of both years.Additional survey collections of epilithic algae were made at 14 sites in the east arm of the lake during June and July of 1975. The most common species included Tabellaria flocculosa, Rhopalodia gibba, Cymbella angustata, C. microcephala, Anomoeoneis vitrea, Achnanthes minutissima, and Ulothrix zonata. Algal densities were considerably less than those recorded from the north shore, a reflection of lower nutrient and alkalinity levels. Maximum abundances for microscopic and filamentous algae were 1.05 × 109 μm3/cm2 and 4.1 mg/cm2 respectively.
Zoospore ultrastructure of Phlyctochytrium plurigibbosum (Chytridiales)
Authors: Barr D. J. S. , Hadland-Hartmann V. E.
Published: November 2007

The zoospore of Phlyctochytrium plurigibbosum Barr is globular to amoeboid while swimming and posteriorly uniflagellate. Mitochondria are in the posterior and are petal-like in their arrangement. The nucleus and one or more lipid globules are in the centre to anterior part of the cell. Morphologically, microbodies are intimately associated with lipid globules and loosely associated with mitochondria. There is a conspicuous double membrane system of smooth endoplasmic reticulum, and free ribosomes are dispersed throughout the cytoplasm. Microtubules radiate into the zoospore body from the proximal face of the kinetosome.
Dormancy studies in seed of Avena fatua. 9. Demonstration of genetic variability affecting the response to temperature during seed development
Authors: Sawhney Ramma , Naylor J. M.
Published: November 2007

Experiments are reported which demonstrate characteristic differences among pure lines of wild oats in the degree to which seed dormancy is influenced by temperature during seed development. In some lines, high temperature during seed maturation greatly reduced the duration of primary dormancy; in others, this effect was relatively slight. Evidence is discussed that two temperature-sensitive physiological processes influence the duration of dormancy in this species.
Sexual reproduction of white spruce (Picea glauca)
Authors: Owens John N. , Molder Marje
Published: November 2007

Reproductive buds broke dormancy at the same time as vegetative buds. Pollen mother cells entered prophase of meiosis immediately after dormancy and five-celled, winged pollen was mature about 6 weeks later. Megasporogenesis occurred 3 weeks after microsporogenesis and the female gametophyte was mature in about 6 weeks. Pollination occurred over about 1 week in late May or early June and fertilization occurred about 3 weeks after pollination. One to four archegonia developed. A comparable number of 16-celled proembryos usually developed within 1 week after fertilization and cotyledons began to develop about 1 month after fertilization. Simple polyembryony occurred in most ovules but cleavage polyembryony was not observed. Embryos were fully developed in late August and seeds were mature and shed in September.The small number of archegonia often present, the high incidence of self-pollination, which may have been the cause of the high frequency of early embryo abortion, and the failure of basal and distal ovules to become pollinated were major causes of empty seed.The phenology of reproductive development varied with the site and the elevation but varied little at one site in successive years. Differences were greatest early in the growing season, but by the time of fertilization, higher elevation trees which began development much later had nearly caught up with lower elevation trees and seeds from all sites were mature and shed at about the same time.Reproductive bud dormancy like vegetative bud dormancy was broken in response to photo-period rather than temperature; however, subsequent cone development was greatly affected by temperature.
Effects of sulfur dioxide and ozone on Ulmus americana seedlings. II. Carbohydrates, proteins, and lipids
Authors: Constantinidou H. A. , Kozlowski T. T.
Published: November 2007

The effects of SO2 (2 ppm for 6 h), O3 (0.9 ppm for 5 h), and SO2–O3 mixtures (2 ppm SO2 and 0.9 ppm O3 for 5 h followed by SO2 for 1 h) were studied on metabolite contents of 4-month-old, actively growing and quiescent Ulmus americana L. seedlings. Effects on metabolite contents in leaves, stems, and roots were examined 24 h, 1 week, and 5 weeks after exposure to pollutants for actively growing seedlings, and 24 h and 1 week for quiescent seedlings. Fumigations caused significant reduction in total nonstructural carbohydrate and protein contents of actively growing seedlings within 24 h after fumigation. By the end of 5 weeks, however, carbohydrate and protein contents of new (< 1 cm long at the time of fumigation) leaves were comparable with those of control plants, indicating that capacity of new leaves to function was restored. The adverse effects of pollutants on metabolites of older leaves (> 1 cm long) of actively growing seedlings persisted throughout the 5-week period. Changes in lipid contents of actively growing seedlings were small and in most cases not significant. Exposure to pollutants decreased lipid contents of quiescent seedlings (up to 28%); this decrease was much lower than reduction in carbohydrates or proteins (up to approximately 65%). Metabolite contents of both actively growing and quiescent seedlings were reduced most by SO2–O3, an intermediate amount by SO2, and least by O3 treatment.
Ultrastructure of compatible and incompatible reactions of sunflower to Plasmopara halstedii
Authors: Wehtje Glenn , Littlefield Larry J. , Zimmer David E.
Published: November 2007

Penetration of sunflower, Heliantluis animus, root epidermal cells by zoospores of Plasmopara halstedii is preceded by formation of a papilla on the inner surface of the host cell wall that invaginates the host plasma membrane. Localized degradation and penetration of the host cell wall by the pathogen follow. The invading fungus forms an allantoid primary infection vesicle in the penetrated epidermal cell. The host plasma membrane invaginates around the infection vesicle but its continuity is difficult to follow. Upon exit from the epidermal cell the fungus may grow intercellularly, producing terminal haustorial branches which extend into adjacent host cells. The fungus may grow through one or two cortical cell is after growing from the epidermal cell before it becomes intercellular. Host plasma membrane is not penetrated by haustoria. Intercellular hyphae grow toward the apex of the plant and ramify the seedling tissue. Resistance in an immune cultivar is hypersensitive and is triggered upon contact of the host cell with the encysting zoospore before the host cell wall is penetrated. Degeneration of zoospore cytoplasm accompanies the hypersensitive reaction of the host. Zoospores were often parasitized by bacteria and did not germinate unless penicillin and streptomycin were added to the inoculum suspension.
Reconstruction tridimensionnelle du chondriome de Ginkgo en culture tissulaire; étude au moyen de coupes épaisses et de coupes fines sériées
Authors: Rohr René
Published: November 2007

The observation of thick sections and serial thin sections with the electron microscope demonstrates a reticular organization of mitochondria in cultured cells from Ginkgo. Thick sections show that most of the mitochondria fuse either in loose networks made up of elongated elements or in dense clusters composed of globular units. Serial thin sections enable us to prove the true reticular nature of the mitochondrial organization; most of the mitochondrial profiles are part of highly fused and branched networks. These mitochondrial reticula (about two to three per cell) occupy an important place within the cell. Some mitochondria remain isolated or they fuse slightly. Two three-dimensional models have been built: the first one constructed with cardboard sheets is used to display the organization of a reticulum; the other of Plexiglas clearly indicates the relative positions and the form of mitochondria in a complete cell. The mitochondria, plastids, and vacuoles of this cell are also measured and enumerated.
A revision of Linodochium, Pseudocenangium, Septopatella, and Siroscyphella
Authors: Dyko B. J. , Sutton B. C.
Published: November 2007

Pseudocenangium Karst. is redescribed and illustrated, and Siroscyphella Höhn. is reduced to synonymy with it. Two species, P. pinastri and P. succinenm, are accepted. Septopatella Petrak, based on P. septatum, is confirmed as a distinct form genus. Pseudocenangium hartigianum and P. umense are made the types of the new form genera Gelatinopycnis and Pocillopycnis respectively. Pseudocenangium laricinum is excluded. The related form genus Linodochium hyalinum (Lib.) Höhn. is redescribed and illustrated.
Developmental studies of the leaves of Sagittaria latifolia and their relationship to the leaf-base theory of monocotyledonous leaf morphology
Authors: Bloedel Char A. , Hirsch Ann M.
Published: November 2007

The adult sagittate leaf of Sagittaria latifolia Willd. (Alismataceae) is an example of a monocotyledonous leaf which is differentiated into distinct blade, petiole, and sheath regions. Unlike some bladed monocotyledonous leaves in which the lamina has been shown to be a modification of the leaf base, the adult arrowhead-shaped leaf has no radial precursor tip which facilitates its evaluation in terms of the leaf-base theory. However, the scale and linear leaves of this plant are each comprised of a dorsiventral leaf base and a radially symmetrical upper leaf zone. These leaves are found in a heteroblastic series beginning with reduced scale leaves. Comparative morphological studies of the scale and linear leaves as well as evidence from scanning and light microscopy of the arrowhead-shaped leaves indicate that the lamina of the sagittate leaf is derived from the distal portion of the upper leaf zone. Similarities in internal structure between the unifacial distal region of the linear leaf and the dorsiventral sagittate blade also support this observation. Therefore, Knoll's leaf-base theory of monocotyledonous leaf morphology can be expanded to accommodate the sagittate leaf.
Le système endophytique du Viscum album : anatomie et fonctionnement des suçoirs secondaires
Authors: Sallé G.
Published: November 2007

Sinkers of Viscum album were studied in infected branchlets of Pyrus mains. Each sinker consists of parenchymatous cells and isodiametric vessels. Moreover, the oldest ones have a radially oriented tissue (radial system) with elongated tracheids. The outermost vessels of the sinkers are in direct contact with those of the host xylem. Serial sections show that vessel members around the periphery of the sinkers have perforations on their longitudinal tangential walls, whereas in the middle of the sinkers, perforations occur on their transversal or longitudinal walls facing the radial system. A scheme is proposed indicating how water and mineral salts travel, through the sinkers, from the host to the cortical strand.An intercalary meristem is observed at the base of the sinkers; it corresponds in position to the cambial zone of the host. Its cyclic activity is demonstrated: from October to January, this meristematic zone shows no DNA synthesis, no mitosis, and cells 'blocked' in their G 1 presynthetic phase. From April to June, mitosis and DNA synthesis reach a maximum. A comparison is established between the growth of the host cambium and the one of the intercalary meristem.
Populational variation in the leaf oil terpene composition of western red cedar, Thuja plicata
Authors: Rudloff E. von , Lapp Martin S.
Published: November 2007

Intra- and inter-populational variations in the leaf oil terpene composition of western red cedar from 29 different collection sites from most of its natural range were investigated. This cedar species has one of the lowest degrees of variability found thus far in northern North American conifer species. No significant difference was found between coastal and interior populations and only slight divergence was recorded in outlying ones.
Seasonal variation of abscisic acid in the dormant shoots of Douglas-fir
Authors: Webber Joe E. , Laver Murray L. , Zaerr Joe B. , Lavender Denis P.
Published: November 2007

The occurrence of abscisic acid (ABA) in the dormant shoots of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was confirmed by bioassay, thin-layer chromatography, gas–liquid chromatography, and gas–liquid chromatography – mass spectrometry. Seasonal variation of ABA in the buds, leaves, and stems was then determined using 2-trans-ABA as an internal standard. Concentrations of ABA were highest in the autumn for buds (2.1 μg/g) and needles (0.79 μg/g) and highest in January for stems (0.34 μg/g). The lowest concentrations for all tissues were in February and March, before bud burst. Close correlation of levels of ABA with previously measured physiological evidence of growth and metabolic activity suggests a possible role in the dormancy cycle of Douglas-fir.
A study of heterokaryosis and its influence on virulence in Fusarium oxysporum lycopersici
Authors: Sldhu Gurmel S. , Webster John M.
Published: November 2007

Single-step amino acid auxotrophs were obtained by ultraviolet irradiation of microconidia from races I and 2 of Fusarium oxysporum lycopersici. Intrarace and interrace combinations were made between the mutants to synthesize heterokaryons. After appropriate tests, 13 heterokaryons were selected for analyses of nuclear ratios and virulence. Results indicate that nuclear ratios of intrarace heterokaryons were more balanced than those of interrace heterokaryons. This may be due to incompatibility factors. Tests on four tomato cultivars indicate that heterokaryons rarely show an increase in virulence. There was limited occurrence and low survival of heterokaryons under soil conditions. The findings are discussed in light of the role of heterokaryosis in natural variability and virulence of Fungi Imperfecti.
Light and scanning electron microscopy of the telial, pycnial, and aecial stages of Melampsora lini
Authors: Gold R. E. , Littlefield L. J.
Published: November 2007

Urediospore infection by Melampsore lini on stems or leaves of Linum usitatissimum produced uredia which quickly converted from urediospore to teliospore production. The telium was composed of a palisade of laterally united, sessile, prismatic teliospores (ca. 50 × 6 μm) positioned between the epidermis and the stem cortex. Teliospores were induced to germinate by subjecting telia to a series of freeze–thaw and wet–dry cycles. Germination began after 6–10 such cycles and continued until 20–24 cycles had been performed. Teliospores germinated apically to form basidia and smooth, ovate to elliptical basidiospores (ca. 6 × 5 μm). Basidiospore germlings penetrated directly through the host epidermis and formed intercellular and intracellular hyphae. The haploid intracellular structures formed were irregular and hypha like, often septate, and occasionally grew into adjacent host cells. Several morphological variants of intracellular hyphae were observed; all such structures were distinct from the more specialized dikaryotic haustoria derived from either dikaryotic aeciospore or urediospore infections. Development of pycnia occurred primarily in the substomatal cavities of leaves. Flexuous hyphae extended through stomata; concomitantly, pycniospores produced in chains from a palisade of pycniosporophores exuded through the stomata onto the leaf surface in droplets of honeydew. Pycniospores were smooth, ellipsoidal, and ca. 3 × 1.5 μm. Caeomoid aecia developed on both sides of flax leaves and on stems. Short irregular chains of aeciospores alternating with smaller wedge-shaped intercalary cells were produced from sporogenous hyphae at the base of aecia. Mature aeciospores were globose to ovate (ca. 16 × 13 μm) and were densely ornamented with smooth, cog-like verrucae.
Translocation of 11C from leaves of Helianthus, Heracleum, Nymphoides, Ipomoea, Tropaeolum, Zea, Fraxinus, Ulmus, Picea, and Pinus: comparative shapes and some fine structure profiles
Authors: Thompson R. G. , Fensom D. S. , Anderson R. R. , Drouin R. , Leiper W.
Published: November 2007

A 3-min pulse of 11CO2 was fed to leaves of various plant species to allow us to compare the patterns of movement of 11C translocate over 90 min. Three groups of profiles were found. (1) In Helianthus, Nymphoides, Tropaeolum, Ipomoea, and Fraxinus, a mass flow passed successive detectors, rising steadily over a 90-min period. (2) In Zea and Triticum, the mass flow remained at a peak for 5–10 min and fell steadily thereafter. (3) In Picea and Pinus, no obvious mass-flow pattern was detected in 90 min but rather a series of waves or packets. In every case, the activity opposite certain positions accumulated faster than others, suggesting that points of local buildup of translocate occur along a stem or petiole.By using high activity 11CO2 counting times of 5 s or 1 s, and the five-point mean technique of analysis of data, we have been able to detect aberrations in the tracer profile opposite each detector. These aberrations are due in part to the movement of tracer at different speeds in parallel veins, in part to the superposition of reverse flow of tracer, and in part to apparent discontinuities of flow or small waves of tracer. We conclude that some pulsatory sucrose loading mechanism is possible in the leaves, but a nonsteady-state translocatory mechanism is also possible. We have developed techniques for detecting the points of time of the onset of mass flow and the method of following small peaks of tracer activity past successive detectors. Waves of translocate moved at 0.2 cm min−1 in pine and spruce and 0.5–10 cm min−1 in ash and the angiosperms. Some synchrony of flow causes activity reinforcement or interference to occur in transient fashion.
Nematophagous fungi: a new Harposporium producing aerial arthroconidia
Authors: Barron G. L.
Published: November 2007

A new Harposporium is described which produces branching chains of arthroconidia at the apex of phialide-bearing conidiophores. Phialoconidia are crescent shaped in lactophenol but tend to coil to form part of a helix in water. Phialoconidia are very variable in size and have a mucoid secretion at the proximal end. Arthroconidia germinate in the presence of nematodes to produce phialoconidia from short, cylindrical conidiogenous cells. Infection of a nematode host is initiated by lodging of a phialoconidium in the oesophagus.
Direct measurement of water capacity of Beta vulgaris storage tissue sections using a displacement transducer and resulting values for cell membrane hydraulic conductivity
Authors: Green William N. , Ferrier Jack M. , Dainty Jack
Published: November 2007

The water capacity of red beet (Beta vulgaris) storage tissue is measured as a function of water potential. These measurements use a linear displacement transducer to measure equilibrium tissue section thickness as a function of bathing solution osmotic pressure. The water potential equilibration time constant of the tissue as a function of water potential is also measured, using the applied force method. The water capacity and time constant data are combined to provide values for the hydraulic conductivity of the cell membrane.
An energy dispersive x-ray analysis study of protein bodies in the seeds of Astragalus bisulcatus and Oxytropis Lambertii
Authors: Lott John N. A. , Vollmer Catherine M.
Published: November 2007

Elemental composition of protein body regions in radicle, stem, and cotyledon areas of the leguminous plants Astragalus bisulcatus and Oxytropis Lambertii were determined using energy dispersive x-ray (EDX) analysis. Globoid crystals from all tissue regions of both species routinely contained P, K, Mg, and Ca. Possible relationships between seed size and the presence of calcium in globoid crystals of plants in the legume subfamily Papilionateae are discussed. Although the two species studied are selenium accumulators, no Se was ever detected in either globoid crystal or proteinaceous regions. The unusual mineral uptake properties of these plants seemingly does not influence the types of mineral reserves deposited in the protein bodies of the seed.
Trois Laboulbéniales (Ascomycetes) nouvelles, parasites de Diptères
Authors: Rossi Walter , Rossi M. Graziella Cesari
Published: November 2007

Three new species of Stigmatomyces occurring on African Diptera are described: Stigmatomyces canzonerii, parasitic on Canace nasica Hal. (Canaceidae), Stigmatomyces giordanii, parasitic on Asmeringa sp. (Ephydridae), and Stigmatomyces senegalensis, parasitic on Aphrosylus sp. (Dolichopodidae).
Respiratory pathways and fat synthesis in the developing castor oil seed
Authors: Simcox P. D. , Garland W. , DeLuca V. , Canvin D. T. , Dennis D. T.
Published: November 2007

During castor oil seed development, changes occur in the activities of enzymes involved in fatty acid biosynthesis, glycolysis, and the pentose phosphate pathways. The activities of acetyl-CoA carboxylase, phosphofructokinase, pyruvate kinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase per seed increase during the phase of rapid oil synthesis in the endosperm. As the seed matures and the rate of fatty acid synthesis decreases, there is a corresponding diminution in the activities of these enzymes. An indication of the metabolic capacity of the plastids was determined by monitoring the ribulose-1,5-bisphosphate carboxylase activity in the endosperm.
The regulation of nitrate reduction in spinach leaves
Authors: Canvin David T. , Woo K. C.
Published: November 2007

Nitrate reduction did not occur in leaves in the dark in aerobic conditions but did occur in anaerobic conditions. Nitrate reduction in leaves in the dark in aerobic conditions was observed, however, when the respiratory electron transport chain was inhibited with antimycin A but not when it was inhibited with amytal or rotenone. It would appear that NADH generated outside the mitochondria was used for nitrate reduction in the dark under anaerobic conditions. The relevance of this observation to nitrate reduction in the light is discussed.
Contrôle génétique de deux états différenciés de Nectria haematococca
Authors: Daboussi-Bareyre M. J. , Laillier-Rousseau D. , Parisot D.
Published: November 2007

With a fixed genome and in uniform culture conditions, the wild-type strain of Nectria haematococca proceeds from a juvenile state to either of two morphologically distinct differentiated states. These differentiated states appear suddenly as small brown areas in the margin of the thalli and widen to hyphae in the vicinity through transmission of two extrachromosomal factors, each of them being specific for one of the two differentiated states.Mutagenesis indicates that nuclear genes are involved in controlling the establishment of differentiation. Mutations were obtained in at least six genetically independent loci. Some genes influence the maintenance of both differentiated states; others affect them specifically. Studies on the double mutants obtained from crosses between mutant strains reveal information on the mode of action of the genes. The relationships between these genes and the extrachromosomal factors are discussed.
Ontogeny, structure, and necrosis of trichomes on the epidermis of slipper spurge (Pedilanthus tithymaloides)
Authors: Dave Y. S. , Patel N. D. , Rao K. S.
Published: November 2007

The trichomes of slipper spurge (Pedilanthus tithymaloides Poit.) are uniseriate, curved, and branched or unbranched. The trichome originates by an enlargement of a single protodermal initial, which elongates and gradually becomes curved, septate, and branched. Cytoplasm is present only during its early developmental stages. Later its cytoplasm and nucleus undergo necrosis and its walls become thickened. The structural changes occur during the bilumenation of the basal cell. The distal part above the bilumenated basal cell of the trichome is finally shed and only the thick-walled basal cell remains.
Pure culture synthesis and host specificity of red alder mycorrhizae
Authors: Molina Randy
Published: November 2007

Cultures of 28 ectomycorrhizal fungi were tested in pure culture syntheses for mycorrhiza formation with red alder. Only 4 of the 28 fungi tested formed characteristic ectomycorrhizae: Alpova diplophloeus, Paxillus involutus, Aslraeus pteridis, and Scleroderma hypogaeum. These mycorrhizae are briefly described, and the specialization of alder mycorrhizae is discussed.
Production of phytotoxic substances by Alternaria triticina
Authors: Kumar C. S. K. Vijaya , Rao A. S.
Published: November 2007

The culture filtrate of Alternaria triticina Prasada & Prabhu inhibited germination and root elongation of seeds of a resistant variety (HD 1982) and a susceptible variety (Kalyan Sona) of wheat. The filtrate-induced symptoms on the leaves of wheat plants were similar to those induced by the fungus. Thin-layer chromatographic analysis of the crude toxin extracted in n-butanol, acetone, and petroleum ether revealed the presence of more than one phytotoxic compound in the culture filtrate of A. triticina. The toxic principles were thermostable and nonspecific and inhibited the growth of wheat. The possible role of toxic metabolites during pathogenesis is suggested.
Ultrastructure of sporulation in the Hemiascomycetes Ascoidea corymbosa, A. rubescens, Cephaloascus fragrans, and Saccharomycopsis capsularis
Authors: Ashton M. L. , Moens P. B.
Published: November 2007

Sporulation in four species belonging to three different families of the Hemiascomycetes is described from serial sections. The results show that in each species the formation of the ascospore wall is initiated at a specialized spindle pole body. Spore delimitation proceeds concurrently with the last nuclear division in the ascus. The findings support the taxonomic position that these species belong to a group that includes the yeasts but that is distinct from the Euascomycetes.
Observations on Mucosetospora (Coelomycetes)
Authors: Raj T. R. Nag , Morelet M.
Published: November 2007

Mucosetospora Morelet is reduced to synonymy with Phyllostieta Desm. (nom. cons.). Mucosetospora gallica (Morelet) Morelet (≡ Petrakomyces gallicus Morelet) is treated as a synonym of Phyllostieta spinarum (Diedicke) Nag Raj & Morelet comb. nov. (≡ Phoma spinarum Diedicke).
Light inhibition of rooting in Norway spruce (Picea abies) cuttings
Authors: Strömquist Lars-Helge , Eliasson Lennart
Published: November 2007

Stem cuttings from 3-year-old seedlings of Picea abies L. (Karst.) (Norway spruce) were rooted in tap water in a growth chamber. The effect of two levels of irradiance given to either the upper two thirds of the cuttings or to the whole cutting was investigated. When only the upper two thirds of the cuttings were irradiated, the number of cuttings which rooted was lower at the higher irradiance level (40 W m−2) as compared with the number rooting at the lower irradiance level (8 W m−2). Rooting was inhibited almost completely at either of the irradiances if the base of the cutting was also irradiated.
Analysis of variation in leaf and twig characters of Abies lasiocarpa and A. amabilis from north-coastal British Columbia
Authors: Parker William H. , Bradfield Gary E. , Maze Jack , Lin S.-C.
Published: November 2007

To investigate the extent and causes of natural variation within and among populations of Abies amabilis and Abies lasiocarpa collected from north-coastal British Columbia, morphological and anatomical data were analyzed using principal components analysis, canonical analysis, and regression analysis. The results indicate that hybridization does not occur between these two species, even in areas modified by natural or artificial disturbance. Within A. lasiocarpa there is an indication of evolutionary divergence of populations correlated with latitude and (or) local environmental conditions. Specimens of A. lasiocarpa and A. amabilis collected from a lava bed were found to be differentiated from forest-grown populations, apparently as a result of either phenotypic plasticity or local selection pressures affecting the survival of newly established seedlings. Regression analysis demonstrated that twig periderm thickness in A. amabilis correlates significantly with altitude suggesting the presence of clinal variation.
Vegetational development and the effect of geese on vegetation at La Pérouse Bay, Manitoba
Authors: Jefferies R. L. , Jensen A. , Abraham K. F.
Published: November 2007

The salt marshes at La Pérouse Bay, Manitoba, are described. Unconsolidated, water-saturated sediment is colonized by Hippuris tetraphylla, Puccinellia phryganodes, and Carex subspathacea. These sediments undergo frost heave, and on elevated mounds, Elymus arenarius var. mollis and Salix brachycarpa become established. This last species is the dominant one of the low willow tundra, which is the characteristic vegetation of the coastal strip. Where drainage is impeded in the upper marsh, relatively high salinities occur and species such as Salicornia europaea agg. and Triglochin maritima are present.A population of 10 000 to 20 000 lesser snow geese (Anser caerulescens) feed, in summer, on Puccinellia phryganodes, Carex subspathacea, Potentilla egedii, and Elymus arenarius var. mollis. The birds strip the shallow turf of Puccinellia in low lying areas between clumps of willow. This terracing of the surface creates depressions which become filled with water and ice. The role of geese in producing these ponds in the upper levels of salt marshes in the Arctic does not appear to have been reported previously. The ponds are subsequently colonized by Carex aquatilis and Triglochin maritima. The salt marsh gives way to an extensive fresh water marsh dominated by species of Salix, Eriophorum angustifolium, Calamagrostis neglecta, and Dupontia fisheri. The results are compared with data from other salt marshes in Hudson Bay and in the Arctic.
Effets du lindane sur la division, le cycle cellulaire et les biosynthèses de deux Algues unicellulaires
Authors: Jeanne N.
Published: November 2007

The lindane or hexachlorocyclohexane γ isomer inhibited cell division in two cultivated unicellular algae and caused morphological changes of enlarged cells; increase of the golgi apparatus, endomultiplication of the organelles, abnormal partition of nuclei, and a decrease in the number of microtubules were observed. However, lindane did not change the polymerization of tubulin in vitro. In synchronously dividing Dunaliella bioculata, mitosis could be blocked even if the insecticide was added to cultures after the beginning of the outburst of cell division during the dark period. During the first cell cycle, the RNA and protein cell content increased more slowly in treated cells and then continued to increase more or less rapidly during the second cell cycle. The DNA synthesis was strongly inhibited by 10 μg/mL of lindane and depressed by 5 μg/mL as early as the first cell cycle. The synthesis did not resume during the second cell cycle.
Histology of the development of the graft union in pea roots
Authors: Stoddard Frederick L. , McCully M. E.
Published: November 2007

The development of the union of pea roots splice grafted when 8 days old is followed with optical microscopy. Cell divisions are induced close to the wound in both partners in 1 to 2 days. Content of cytoplasm increases in some cells of the pith, cambium, pericycle, and cortex, and these cells proliferate to form both disorganized callus within the vascular cylinder and organized nodules of cells in the cortex of each partner. There is more proliferation proximal to the graft. The resulting cells invade the graft gap, completely filling it and effecting union by day 7. The first wound-repair vascular tissue differentiates on day 4 in both partners. Wound-repair xylem bridges the union on day 7, phloem on day 8, and a cambium by day 12. The necrotic layer (cells killed by cutting), initially thick, is disrupted by day 4 and largely disappears, as do its phenolic staining properties, by the time of cohesion. Growth of the whole plant resumes by day 9. During development of the union, the cortex and pith proliferate most, the pericycle less, the endodermis and cambium least, thus disproving the dogma that the cambium is the sole proliferative layer in graft formation.
Vegetation characteristics of Snow Goose nest sites
Authors: Heagy M. I. , Cooke F.
Published: November 2007

The vegetation at a Lesser Snow Goose breeding colony was examined to determine if particular plant species or species associations were characteristic of the nest sites of the geese. A stepwise discriminant analysis revealed that nest sites could be satisfactorily distinguished from the ambient vegetation using 2 of the 29 plant species growing in the quadrats. These two species, lyme grass (Elymus arenarius ssp. mollis) and arctic daisy (Chrysanthemum arcticum ssp. polare) were strongly associated with Snow Goose nest sites.Possible explanations for the association are examined. It is suggested that rather than a cause and effect relationship between plants and nest sites, E. arenarius and C. arcticum have similar ecological requirements to those of the geese for a nesting site.
Effect of cultural age and a single photoperiod on morphogenesis of the discomycete Pyronema domesticum
Authors: Moore-Landecker Elizabeth
Published: November 2007

The discomycete Pyronema domesticum requires light for the production of its gametangia and apothecia. Effects of a single exposure to light (150 ft-c (1 ft-c = 10.76391 lx)) for periods ranging from [Formula: see text] to 168 h on cultures aged 0–10 days were evaluated. A timetable for major developmental events (e.g., gametangial maturation) was established to determine the reactions of specific morphological events to light. Light was required to initiate gametangial production, but was not required at the time of gametangial differentiation. A minimum single exposure of 6 h was required to initiate gametangia, whereas a single exposure of 12 h was required to allow maximum development of the ascogonia to the fully globose form. Development of the ascogenous hyphae, asci, and ascospores was favored by exposure to a longer period of light and reached maximum development with exposure to at least 36 h of light. Although light favors ascospore formation, they can be delimited in the dark. An extended period of light (over 96 h) inhibits ascospore maturation.Neither gametangia nor apothecia were formed in cultures that were either too young (less than 2 days) or too old (6 days or more) at the time of light exposure. The age of 3 days at the initiation of light exposure was optimum for gametangial production, for development of the ascogenous hyphae and ascospores, and for apothecial expansion. In those cultures that were 4 days old at the time of exposure, many of the apothecia either lacked paraphyses, had very short paraphyses, or had an unusually high proportion of sterile asci.Sclerotia were only formed in the cultures which were exposed to light for comparatively short (18 h or less) periods of time. These sclerotia were intermixed with apothecia in the cultures.
Fungal community structure in some alpine soils
Authors: Bissett J. , Parkinson D.
Published: November 2007

The community structure and interactions among the soil microfungi of three alpine sites were investigated using a factor analytical method. The sites were distributed along an elevation gradient, and the diversity and evenness of allotment of species were inversely related to altitude. Clusters of species having similar distributions were defined from factor analyses performed separately for each site. Within each site, differences among the soil horizons were primarily responsible for variation in the fungal community, and species groups were differentiated by their patterns of colonization of the soil profile. Changes in the mycoflora with depth were continuous, although the magnitude of these changes was greater near the surface of the soil. Seasonal changes also were most apparent in the surface horizons.In a grassland site at 1900 m, a species group dominated by Penicillium janthinellum was largely restricted to the surface horizons of the soil, and three other species groups were affected by seasonal changes in the environment. In an alpine meadow site (2530 m), the Penicillium steckii and Cylindrocarpon destructans groups occurred in the surface horizons, with the first group predominant in the spring and the second in the summer and fall. At a summit ridge site (2840 m), all taxa except the sterile fungi were essentially restricted to the surface horizons. Species groups dominated by sterile-dark fungi were predominant in the bottom horizons at all three sites.The most frequently occurring species usually had large communalities indicating a high degree of association with the other species, and probably reflecting their influence over the suitability of the environment for exploitation by other species. The communality structure also indicated a decrease in species interactions with increasing depth of soil.
The taxonomy of Minuartia rossii (Caryophyllaceae)
Authors: Wolf Steven J. , Packer John G. , Denford Keith E.
Published: November 2007

The Minuartia rossii complex, which consists of M. austromontana, M. elegans, and M. rossii s. str., is confined primarily to Arctic–Alpine North America. Previously, the three taxa have been recognized at various taxonomic levels. However morphological, cytological, and phytogeographical data support the recognition of the taxa at the specific level. The basic chromosome number of the complex is x = 15, with M. rossii having 2n = 58 and 60, M. austromontana 2n = 30, and M. elegans both 2n = 30 and 2n = 60. With respect to reproductive biology, the complex as a whole exhibits pronounced protandry and is gynodioecious; however, M. rossii s. str. rarely flowers and relies almost exclusively on vegetative reproduction via bulbils. The three taxa have distinct geographical distributions: M. rossii. Wrangel Island, high Arctic North America, Greenland, and Spitzbergen; M. elegans. Eastern Siberia, Alaska, the Yukon, and south to Alberta; and M. austromontana, confined primarily to the front ranges of the northern and central Rocky Mountains. This distribution pattern is probably the result of Pleistocene survival of the taxa in three different areas: the Canadian Arctic Archipelago, Beringia, and south of the ice. The epithet columbiana frequently applied to the Rocky Mountain taxon is invalid. The name Minuartia austromontana S. J. Wolf et Packer is proposed for this taxon and it is herein described, having never previously been given formal taxonomic recognition.
The effect of sodium hypochlorite, gibberellic acid, and light on seed dormancy and germination of wild buckwheat (Polygonum convolvulus) and cow cockle (Saponaria vaccaria)
Authors: Hsiao A. I.
Published: November 2007

Seed germination of wild buckwheat (Polygonum convolvulus L.) and cow cockle (Saponaria vaccaria L.) increased with increasing time of immersion in 6% sodium hypochlorite (NaOCl). Maximum germination was obtained at 6 to 8 h for wild buckwheat and at 2 h for cow cockle. The effect of NaOCl treatment of wild buckwheat seeds mimics the effect of acid scarification. Wild buckwheat germination was not influenced by light and (or) gibberellic acid (GA3). To induce 50% germination (t½) of cow cockle NaOCl treatments of 0.5 and 1 h were required for seeds incubating in the dark and light, respectively. Once the seed coat was made more permeable by NaOCl, both the promoting effect of GA3 and the inhibitory effect of light were increased. When the optimum effect of NaOCl occurred, all the seeds germinated. However, prolonged NaOCl treatment resulted in either poor germination or seed disintegration.The hard coat seems to be the main factor in regulating wild buckwheat seed germination. Cow cockle, however, is regulated by at least two other factors, light and hormones, in addition to seed coat.
Plant regeneration from stem callus of cassava
Authors: Tilquin J. P.
Published: November 2007

Callus formation and organogenesis have been induced on the internode culture of cassava (Manihot esculenta Crantz). Callusing was rapidly induced on the medium devised by Kartha, Gamborg, and Constabel for the shoot apical meristem culture of cassava. During culture, green protuberances appear on the callus followed by the differentiation of a leaf-like structure. The leaf-like structure degenerated after a month of differentiation. On the same medium, but lacking gibberellic acid (GA3), organogenesis is less frequent and precocious but the leaves which appear are typical of cassava; leaf differentiation is followed by shoot development.
The differential effects of indole-3-acetic acid and its metabolites on the development of Puccinia graminis f. sp. tritici in vitro
Authors: Grambow Hans J. , Tücks Marie Th.
Published: November 2007

3,3′-Bisindolylmethane (BIM), and to a minor degree, 3-methyleneoxindole (MeOx) stimulated mycelial growth in axenic culture of the rust fungus Puccinia graminis f. sp. tritici, race 32, and transition from germ tube to mycelial growth. The effect of BIM was clearly antagonized by indole-3-acetic acid (IAA) and by indole-3-aldehyde (IAld). On the contrary, indole-3-carboxylic acid (ICarb) had a very low antagonistic activity. These results led us to the hypothesis that the balance of the steady-state concentrations of IAA and the various IAA metabolites may be critically involved in the control of the development of the rust fungus in vivo.