bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution of non-work and work-related risk factors to the association between income and mental disorders in a working population: the Health 2000 Study
Authors: Virtanen M , Koskinen S , Kivimäki M , Honkonen T , Vahtera J , Ahola K , Lönnqvist J
Published: February 2008

Objectives:

To examine the contribution of non-work and work factors to the association between income and DSM-IV depressive and anxiety disorders in a working population.

Methods:

A representative sample of the Finnish working population aged 30–64 (1667 men, 1707 women) in 2000–2001 responded to a survey questionnaire on non-work factors (marital status, housing conditions, non-work social support, violence victimisation, smoking, physical symptoms), work factors (job demands, job control, social support at work, educational prospects, job insecurity) and household income. Somatic health was examined in a standard health examination. The 12-month prevalence of depressive and anxiety disorders was examined with the Composite International Diagnostic Interview.

Results:

The risk of having a depressive or anxiety disorder was 2.8 times higher in the low-income group than in the high-income group among men and 2.0 times higher among women. For men, non-work and work factors explained 20% and 31% of this association, respectively. For women, the corresponding figures were 65% and 23%.

Conclusions:

Low income is associated with frequent mental disorders among a working population. In particular, work factors among men and non-work factors among women contribute to the income differences in mental health.
Differential responses of C3 and C4 grasses to mycorrhizal symbiosis, phosphorus fertilization, and soil microorganisms
Authors: Hetrick B. A. D. , Wilson G. W. T. , Todd T. C.
Published: February 2008

The responses of five C4, warm-season and five C3, cool-season tallgrass prairie grasses to phosphorus (P) fertilization, mycorrhizae, and soil microorganisms were compared in greenhouse studies. The warm-season grasses responded positively to mycorrhizae or to P fertilization, but mycorrhizal plants did not respond to P. The soil microflora reduced mycorrhizal plant dry weight and root colonization. In contrast, cool-season grasses did not respond to mycorrhizae or P fertilization. Soil microorganisms did not suppress cool-season plant growth, but root colonization was reduced in nonsterile soil. For the warm-season grasses there was an inverse relationship between mycorrhizal root colonization and P fertilization and a positive relationship between root colonization and plant dry weight. For the cool-season grasses there was also an inverse relationship between root colonization and P fertilization, but the relationship between root colonization and plant dry weight was negative. In both the warm-season and cool-season grasses, low levels of mycorrhizal root colonization persisted even when P fertilization was sufficient to eliminate mycorrhizal effects on plant growth. Thus, warm- and cool-season grasses display profoundly different strategies for nutrient acquisition. Key words: cool-season grasses, warm-season grasses, vesicular–arbuscular mycorrhizae.
A light and electron microscope investigation of the transfer cell region of maize caryopses
Authors: Davis Ronald W. , Smith J. D. , Cobb B. Greg
Published: February 2008

The transfer cell zones from 23-day postpollination corn caryopses were examined using light and electron microscopes and X-ray elemental analysis. The transfer cells were sectioned in cross and longitudinal planes and were characterized by having numerous cell-wall extensions in the form of anastomosing lamellae. The most basal transfer cells had more cell-wall extensions than those that were successively deeper in the endosperm. Cytoplasm, rich with mitochondria, filled the interstices of cell-wall extensions, and many vesiculate areas could be found along the plasma membrane. Some transfer cells contained crystals within plastids. The crystals were composed of magnesium, phosphorus, calcium, and zinc. Other cells had large aggregations of endoplasmic reticulum that were often in close association with mitochondria or unidentified, single membrane bounded organelles. When viewed in cross section, the cell-wall extensions of contiguous cells tended to originate from common loci. Plasmodesmata were absent in the bottom parts of the basal transfer cells where they contacted the maternal tissue but were abundant in the upper parts of these cells and in the transfer cells found deeper in the endosperm. The plasmodesmata were found in clusters and alternated with the wall extension areas.
Temporal patterns of gamete production within individuals of Raphanus sativus (Brassicaceae)
Authors: Young Helen J. , Stanton Maureen L.
Published: February 2008

Previous studies on the deployment of energy to male and female gametes in plants have concentrated on differences among individuals or among related species. We documented temporal patterns of sex allocation within individual wild radish plants grown under controlled conditions. Lifetime investments in pollen and ovules were determined for four unrelated individuals of Raphanus sativus L. (Brassicaceae). Each individual produced 600–1100 flowers over the approximately 5-week flowering period. Mature floral buds were collected daily and ovule number, pollen grain number, pollen size, and pollen to ovule ratio (P:O) were determined for each. Variation in these traits was partitioned into variation among plants and among dates (representing flowering sequence). There was significant variation among plants for all characters, but because plants responded differently to date for three of the characters, further analyses were performed on a plant-by-plant basis. All plants showed significant reductions in pollen number and P:O through time, three plants showed a significant reduction in pollen size with time, and two plants showed a significant reduction in ovule number with time. The observed variation in phenotypic gender among these plants was not environmentally mediated because all plants were grown together in a controlled environment and therefore the differences in allocation to gametes were due to genetic or developmental differences. A result of intraspecific variation in gamete production is that the success of each individual as a male and female parent is likely to vary both within the population and within the flowering season. Key words: pollen to ovule ratio, Raphanus, pollen number, temporal changes, phenotypic gender, Brassicaceae, radish.
Somatic embryogenesis in tissue cultures of Podophyllum hexandrum
Authors: Arumugam N. , Bhojwani Sant S.
Published: February 2008

In vitro multiplication of Podophyllum hexandrum Royle (Podophyllaceae) via somatic embryogenesis is reported. The callus derived from zygotic embryos on Murashige and Skoog medium containing 2 μM BA and 0.5μM IAA differentiated globular embryos. On this medium the globular embryos continued to multiply but failed to mature. Further development of the embryos occurred if the sucrose level in the basal medium was raised to 6% or the medium was supplemented with 1–10 μM NAA. Light and temperatures higher than 25 °C suppressed embryogenesis. Embryogenic potential of the callus has been maintained for over 20 months through subcultures. The somatic embryos developed into plantlets on the basal medium. Key words: endangered species, podophyllotoxin, Podophyllum, somatic embryogenesis.
Pattern of root initiation by an ectomycorrhizal fungus on hypocotyl cuttings of Larix laricina
Authors: Stein Anne , Fortin J. André
Published: February 2008

The rooting pattern of tamarack hypocotyl cuttings produced under the influence of the ectomycorrhizal fungus Laccaria bicolor (Maire) Orton was assessed and compared with the rooting patterns induced by three plant growth regulators. No callus was produced in fungal and control treatments, and the rooting percentages were 93 and 100%, respectively. The fungal treatment caused an upward distribution of roots along the hypocotyls, while in the controls the roots formed only at the base of the hypocotyls. Appreciable callus tissue formation was promoted by all naphtaleneacetic acid concentrations (1, 10, and 50 μM) and rooting percentages never exceeded 10%. A slight swelling at the base of the cuttings was induced by 1 μM indolebutyric acid, whereas higher concentrations (10 and 50 μM) promoted callus tissue formation. Hypocotyls cultured along with the fungus in the auxin-supplemented media did not exhibit any callus tissue formation, and numerous root primordia were initiated on the hypocotyl axis. Callus tissue was absent or negligible on the cuttings treated with ethephon (2-chloroethylphosphonic acid), an ethylene-releasing compound, at 50, 75, and 100 μM. The rooting percentages were optimal at the higher ethephon concentrations, while at 50 μM 93% of the hypocotyls formed roots and root primordia. A redistribution of roots along the hypocotyl was observed with 75 and 100 μM ethephon in a manner similar to the fungal treatment.
Spatial, temporal, and species-specific patterns of heterogeneity in growth chamber experiments
Authors: Potvin C. , Lechowicz M. J. , Bell G. , Schoen D.
Published: February 2008

Despite the sophistication of contemporary growth chambers, growing conditions cannot be uniformly controlled during experiments. Uniformity trials with bean (Phaseolus vulgaris cv. Spartan) and maize (Zea mays cv. Golden Bantam) in the McGill University Phytotron identified three significant sources of variability. First, not even two identically programmed chambers of the same model and from the same manufacturer provide identical growing environments. Second, programmed environmental conditions are not precisely maintained over time even in a single chamber. Third, the growing environment within a chamber has a consistent pattern of spatial variability with poor growth in the chamber corners and best growth in the center. The importance of these effects varies with species and with the parameters measured, but none can be entirely avoided. Good experimental design with replication of treatments across chambers and blocking within chambers can minimize the negative impact of these sources of uncontrolled experimental variability.
Biochemical and cytochemical responses of Stylosanthes guianensis to infection by Colletotrichum gloeosporioides: association of callose deposition with resistance
Authors: Sharp D. , Braithwaite K. S. , Irwin J. A. G. , Manners J. M.
Published: February 2008

Biochemical and cytochemical responses of leaves of the tropical pasture legume Stylosanthes guianensis cv. Graham to infection by a compatible and incompatible race of Colletotrichum gloeosporioides have been investigated. No evidence for the synthesis of phytoalexins and induction of the enzyme phenylalanine ammonia-lyase was obtained. Peroxidase was induced but with little difference between the two interactions. Cytochemical staining and radiolabelling with [14C]cinnamic acid indicated that infection was not associated with cell-wall lignification. In the compatible interaction, several pathogenesis-related proteins and chitinase were induced at 4 days after inoculation, but these proteins were not induced in the incompatible interaction. The deposition of callose in host cells associated with fungal appressoria was monitored by staining with aniline blue. The appressoria of the incompatible race were associated with a greater number of host callose deposits than those of the compatible race between 1 and 3 days after inoculation. In addition, the aniline blue staining deposits associated with the appressoria of the incompatible race showed a greater intensity of fluorescence when compared with those of the compatible race. Histological studies showed low levels of penetration (1–6%) for both interactions. In the incompatible interaction, fungal development did not extend past vesicle formation in the penetrated cell, whereas in compatible interactions the fungus had extended to greater than 20 cells by 96 h. Thus, among a number of possible host responses to infection, the deposition of callose associates most closely with race-specific resistance. Key words: anthracnose, phytoalexins, peroxidase, papillae, chitinase.
Seasonal variations of growth in the red alga Chondrus crispus on the Atlantic French coasts. II. Relations with phosphorus concentration in seawater and internal phosphorylated fractions
Authors: Chopin Thierry , Hourmant Annick , Floc'h Jean-Yves , Penot Michel
Published: February 2008

Monthly measurements of the total phosphorus content in three parts of Chondrus crispus showed a gradient along the thallus with its seasonal variations. Parallel patterns of seasonal variations were observed between total phosphorus content in the growing parts of the alga (apex and middle) and dissolved inorganic phosphorus concentration in seawater. 32P-phosphorus absorbed in the alga was incorporated in organic compounds, of which 60% were water-soluble. Water-soluble phosphorylated compounds were those usually found in higher plants and other algae. With a low phosphorus content and a high specific radioactivity, the water-soluble inorganic fraction probably did not have a storage role. The water-soluble organic fraction presented the opposite characteristics; hence, it could be considered as a storage pool, together with the acid-insoluble fraction. As the seasonal pattern of the phosphorylated fractions was similar at the three parts of the alga, the phosphorus gradient along the thallus did not correspond to a qualitative or quantitative difference in storage compounds in these parts, but was still attributed to seasonal variations of phosphorus concentration in seawater and growth.
Characterization of indol-3-ylacetic acid in developing secondary xylem of 26 Canadian species by combined gas chromatography – mass spectrometry
Authors: Savidge R. A.
Published: February 2008

Using one purification procedure, endogenous indol-3-ylacetic acid (IAA), a known regulator of vascular development in woody plants, was characterized by capillary gas chromatography–mass spectrometry in developing secondary xylem of 6 conifers, 16 hardwoods, and 4 additional species of woody plants indigenous to the northern temperate zone. The results suggest IAA may be ubiquitous throughout the Tracheophyta.
Effects of temperature, salt, and osmotic potential on early growth of wheat (Triticum aestivum). I. Germination
Authors: Hampson Cheryl R. , Simpson G. M.
Published: February 2008

Kernels of spring wheat (cv. Katepwa) were germinated in Petri dishes at six osmotic potentials (−0.3 to −1.8 MPa) and eight temperatures (6–34 °C) in single-salt solutions of a variety of chloride and sulfate salts, and the time to onset of germination, germination rate index, and final percent germination were determined. Percent germination was maximal at 18–22 °C in the presence of osmotic stress, but was unaffected by temperature in its absence. At temperatures below 10 °C or above 30 °C and osmotic potentials below −0.3 MPa, germination was delayed, slowed down, and eventually inhibited. Temperature stress intensified the effects of osmotic stress on germination and vice versa. Main effects of temperature, osmotic potential, and salt type and all their interactions were highly significant (P < 0.01) for all variables.
Effects of temperature, salt, and osmotic potential on early growth of wheat (Triticum aestivum). II. Early seedling growth
Authors: Hampson Cheryl R. , Simpson G. M.
Published: February 2008

Kernels of spring wheat (cv. Katepwa) were germinated in Petri dishes at six osmotic potentials (−0.3 to −1.8 MPa) and three temperatures (10, 18, and 30 °C) in single-salt solutions of a variety of chloride and sulfate salts, or in polyethylene glycol. Shoot length and maximum root length were measured at 7 days, and membrane damage of roots was assayed by measuring leakage of UV-absorbing compounds. Low temperature and osmotic potential decreased root and shoot length. High (30 °C) temperature enhanced growth in distilled water controls and in polyethylene glycol, but reduced growth if salt stress below -0.6 MPa was present. All salts greatly enhanced osmotically induced membrane leakage. Changes in membrane leakage with temperature may be partially responsible for observed salt–temperature interactions on growth.
Fungal calcium oxalate in mycorrhizae of Monotropa uniflora
Authors: Snetselaar Karen M. , Whitney Kenneth D.
Published: February 2008

Monotropa uniflora is an achlorophyllous angiosperm that is obligately mycotrophic. The "monotropoid" mycorrhizae it forms resemble ectomycorrhizae but are distinguished by elaborations of the epidermal cell walls that surround intruding fungal hyphae. Monotropoid mycorrhizae collected from blooming plants in late summer contained calcium oxalate crystals between mantle hyphae. The crystals appeared to form in association with hyphal walls and grew into a matrix outside the hyphae. Production of calcium oxalate by M. uniflora's mycobiont seems to be a coordinated metabolic process rather than a random precipitation event. The significance of calcium translocation and isolation as calcium oxalate to this mycorrhizal fungus is unclear, but the presence of extensive crystal deposits during and after flowering of the host plant suggests a possible link with the nutrient transfer occurring at that time. Mycorrhizal regulation of calcium may affect the availability of mineral nutrients to the associated Monotropa plants. Key words: Monotropa uniflora, mycorrhiza, calcium oxalate, ectomycorrhiza.
Comparative anatomy of roots and mycorrhizae of common Ontario trees
Authors: Brundrett Mark , Murase Gracia , Kendrick Bryce
Published: February 2008

The structure of roots and mycorrhizae of trees belonging to 20 important Ontario tree genera were examined. During this study efficient methods for examining root anatomy were developed, and tree root information was compiled. The ultimate lateral roots of most species examined were consistently mycorrhizal, and many species had heterorhizic root systems with separate long and short lateral roots. Tree roots displayed enough structural diversity in features such as thickened, lignified, or suberized walls, and secondary metabolite-containing cells to allow identification of genera. The roots of trees belonged to four major anatomical groups as a result of the major differences between angiosperm and gymnosperm roots, and between those with ectomycorrhizal (ECM) or vesicular–arbuscular mycorrhizal (VAM) associations, (i) Members of the Pinaceae had structurally similar heterorhizic roots that had ECM with a cortical Hartig net. (ii) Thuja (Cupressaceae) had distinctive nonheterorhizic roots with phi thickenings and VAM. (iii) Angiosperms with ECM belonged to diverse families, but all had similar heterorhizic root systems with ECM short roots that had an epidermal Hartig net and a narrow cortex of thick-walled cells, (iv) Most angiosperms with VAM had nonheterorhizic roots, and this group had the greatest diversity of root structural features. Possible structural and defensive roles of root features and potential influences of these features on mycorrhizal formation are considered.
Structure and ontogeny of Betula alleghaniensis – Pisolithus tinctorius ectomycorrhizae
Authors: Massicotte H. B. , Peterson R. L. , Ackerley C. A. , Melville L. H.
Published: February 2008

The ontogeny and ultrastructure of ectomycorrhizae synthesized between Betula alleghaniensis (yellow birch) and Pisolithus tinctorius, a broad host range fungus, were studied to determine the structural modifications in both symbionts during ectomycorrhiza establishment. A number of stages, including initial contact of hyphae with the root surface, early mantle formation, and mature mantle formation, were distinguished. Interactions between hyphae and root hairs were frequent. As a paraepidermal Hartig net developed, root epidermal cells elongated in a radial direction, but wall ingrowths were not formed. Repeated branching of Hartig net hyphae resulted in extensive fine branches and the compartmentalization of hyphal cytoplasm. Nuclei and elongated mitochondria were frequently located in the narrow cytoplasmic compartments, and [Formula: see text] thickenings developed along walls of cortical cells in primary roots.
Ultrastructure and karyology of Tetramyxa parasitica (Plasmodiophoromycetes)
Authors: Braselton James P.
Published: February 2008

Tetramyxa parasitica Goebel was located in galls on shoots of Ruppia maritima L. var. maritima and Zannichellia palustris L. subsp. repens (Boenn.) Schübler & Martens. Ultrastructural features of sporogenic (cystogenous) development included a host–parasite boundary of a single unit membrane, cruciform nuclear division in young plasmodia, synaptomenal complexes in nuclei of transitional plasmodia, and resting spores grouped in fours. Synaptonemal complexes in nuclei were counted through analysis of serial sections. The haploid chromosome number was determined to be 32, which distinguished Tetramyxa from other plasmodiophorid genera. Key words: karyotype, Tetramyxa, Plasmodiophoromycetes.
Variation in the double-stranded RNA phenotype between and within different rust species
Authors: Dickinson M. J. , Wellings C. R. , Pryor A.
Published: February 2008

The dsRNA phenotype of 34 isolates representing 10 Australian pathotypes of Puccinia striiformis, 2 of P. recondita, and 1 each of P. graminis, P. sorghi, P. menthae, and Melampsora lini were examined. Each rust species had its own distinctive dsRNA pattern. Variation occurred in the dsRNA phenotype between the two isolates of P. recondita and among the 34 different isolates of P. striiformis but did not correlate with variation in pathotype. Single pustule isolates of P. graminis and P. recondita were examined to establish that all the dsRNAs were probably present in individual uredospores and were consistently transmitted asexually. The potential use of dsRNA phenotype as a cytoplasmic marker in rust population studies is discussed. Key words: dsRNA, Puccinia, rust.
Ultrastructural morphology of the uredium and collar formation during urediosporogenesis of Uromyces transversalis on gladiolus
Authors: Ferreira Johan F. , Rijkenberg F. H. J.
Published: February 2008

The transverse uredia of Uromyces transversalis on gladiolus leaves were investigated by scanning and transmission electron microscopy. The basal cell forms one or more protuberances distally, each being delimited by a septum to become a urediospore initial. The initial elongates and lays down a septum to form a urediospore and pedicel. The first protuberance on the basal cell forms holoblastically, and evidence is found at the same locus for the subsequent enteroblastic formation of up to three successive urediospore initials. The pedicel wall of a spore thus formed remains on the basal cell and becomes a collar around the next protuberance. The basal layer of the two-layered septum that delimited the pedicel from the basal cell grows out to form the wall of the subsequent protuberance, and in the process ruptures and laterally displaces the terminal septal layer. A new basipetal septum forms to delimit the subsequent urediospore initial. In this manner, several collars form retrogressively and concentrically at one locus.
Circumscription of the genus Medicago (Leguminosae) by seed characters
Authors: Small Ernest , Brookes Brenda , Lassen Per
Published: February 2008

Delimitation of Medicago from its close relatives in tribe Trifolieae subtribe Trigonellinae remains controversial. Scanning electron microscope studies of the seed surface of Medicago, Trigonella, and Melilotus showed consistent differences between Medicago and the other two genera. Smooth and rough seeds occur in all three genera, the rough seeds proving taxonomically useful. The roughness of Medicago seeds is due to rugose surface bumps (usually wrinkled, always with rounded sides), except in the monotypic section Orbiculares. The roughness of seeds of Trigonella, Melilotus, and Medicago section Orbiculares is due to tuberculate surface bumps. The structure of the Malpighian layer shows completely parallel taxonomic differences. The Malpighian cells are traversed by the light line, and the length of the portion of the cell above the light line (a) and that below the light line (b) distinguishes smooth, rugose, and tuberculate seeds. In smooth seeds (of Medicago, Melilotus, and Trigonella), a and b are constant. In rugose seeds (in Medicago only), a is constant while b is greater under the testa bumps, varying with the height of the portion of the bump occupied. In tuberculate seeds (in Medicago section Orbiculares, and in Trigonella and Melilotus), b is constant while a is greater under the testa bumps. These studies confirm the appropriateness of circumscribing Medicago in a wide sense, except for the inclusion of Medicago section Orbiculares.
Systematic implications of achene micromorphology in Carex section Hymenochlaenae (Cyperaceae)
Authors: Waterway Marcia J.
Published: February 2008

The structures of the achene epidermal cells and their included silica deposits are illustrated and described for 28 species that have been referred to Carex section Hymenochlaenae. On the basis of these epidermal features, there are anomalous species in nearly all of the subsections and sections that have been circumscribed by Kükenthal, Mackenzie, Ohwi, and Koyama. Furthermore, some species with nearly indistinguishable achene surface features have quite different overall morphologies and have traditionally been placed in different sections. Similarities in the structure of the silica deposits in the achene epidermal cells may result from the retention of the primitive character state in several different lineages or from parallel development of modified silica bodies or wall structures in different lineages. Levels of homoplasy appear to be too high to make these characters reliable indicators of evolutionary relationships in Carex section Hymenochlaenae.
Chlamydospores of Phytophthora cactorum: their production, structure, and infectivity
Authors: Darmono T. W. , Parke J. L.
Published: February 2008

Chlamydospores of Phytophthora cactorum are described and compared with oogonia and sporangia. Chlamydospores (average diameter 39.7 μm) were generally larger than either oogonia or sporangia, were usually produced terminally on long supporting hyphae and had single, two-layered walls. They were readily formed in vitro in V8 juice broth supplemented with 2 g L−1 CaCO3 after incubation for 20 days at 4 °C. No chlamydospores were produced at 8, 12, 16, 20, or 32 °C, but chlamydospores sometimes developed at 24 and 28 °C. Chlamydospores also formed on mycelial mats buried in pasteurized potting mix after incubation for 20 days at 4 °C. Germination of chlamydospores after freezing at −23 °C for 24 h was 60–80%. Chlamydospores prepared in this way were infectious to American ginseng (Panax quinquefolium) seedlings. All 11 isolates of P. cactorum examined produced chlamydospores. Key words: Phytophthora cactorum, chlamydospores, temperature, ginseng, Panax quinquefolium.
Elemental storage in Cucurbita embryos: X-ray microanalysis of magnesium, potassium, calcium, and phosphorus within globoid crystals
Authors: Ockenden I. , Lott J. N. A.
Published: February 2008

Embryos of Cucurbita maxima, Cucurbita andreana, and their reciprocal hybrids store phosphorus, magnesium, potassium, and calcium in distinctive globoid crystals within protein bodies found in cotyledon mesophyll cells. Samples of cotyledon tissue from each of the four kinds of embryos were cryogenically prepared and analyzed by X-ray microanalysis in the frozen state in a scanning electron microscope. The relative proportions of phosphorus, magnesium, potassium, and calcium were expressed as peak to background ratios. Total concentrations of the four elements in whole cotyledons, as measured by neutron activation analysis, were similar to the trends shown by the peak to background ratios for the same elements. This supports the concept that the bulk of the elements P, K, Mg, and Ca in seed tissues is stored in globoid crystals.
Dynamics of decline and mortality of Chamaecyparis nootkatensis in southeast Alaska
Authors: Hennon P. E. , Hansen E. M. , Shaw III C. G.
Published: February 2008

Alaska-cedar, Chamaecyparis nootkatensis (D. Don) Spach, has been dying in undisturbed forests throughout southeast Alaska for the last 100 years. To determine if decline spreads, boundaries of mortality at seven sites with decline were mapped using aerial photographs taken in 1927, 1948, 1965, and 1976. Mortality was present at all seven sites in 1927. The boundaries of mortality have since expanded, but not by more than 100 m beyond the 1927 limit. In ground surveys, dead Alaska-cedar trees, classified according to their degree of deterioration, were recorded in 427 plots along 39 transects. Fifty-five taxa of understory vegetation were also recorded from 280 plots along these 21 transects; an ordination was produced from their distribution that represented a gradient from bogs to sites with better drainage. Most mortality was associated with bog and semibog sites. Alaska-cedar has a disproportionate level of mortality (65% of basal area dead) relative to other conifers. Local spread of cedar decline occurred along this gradient, as plots with more recently killed cedar trees had high average ordination scores (better drainage) and plots with cedars killed long ago had low average scores (boggy). Snags that probably date from the onset of extensive mortality were relatively common (at least 8% of all snags) on all 23 sites where intensive mortality was surveyed on the ground. As all sites with mortality that we investigated throughout southeast Alaska have these snags, decline does not appear to have spread to new sites since its onset. Although decline is relatively species specific and has patterns of local spread, the spread of mortality is along a specific, preexisting ecological gradient. These results, and the apparent lack of any site to site spread in the last 100 years, suggest that Alaska-cedar decline is not caused by some biotic agent.
Evidence of high self-fertilization in natural populations of eastern white cedar (Thuja occidentalis)
Authors: Perry Daniel J. , Knowles Peggy
Published: February 2008

Arrays of open-pollinated seeds were assayed for allozyme polymorphisms at four loci (Mdh-1, Me, 6Pg-2, and Pgm) to obtain estimates of outcrossing rates for three eastern white cedar populations in northwestern Ontario, Canada. Multilocus population outcrossing rate estimates were low, ranging from 0.507 to 0.745, with significant heterogeneity among populations. Low stand densities and relatively high selfed embryo survival may have contributed to the low effective outcrossing rates observed. Single-tree multilocus outcrossing rate estimates were obtained for nine trees from one population. When estimated jointly with outcross pollen pool allele frequencies, these outcrossing rate estimates ranged from 0.253 to 1.023 with significant heterogeneity among trees. Key words: mating system, outcrossing rate, Thuja occidentalis L.
Widespread incidence of double-stranded RNAs of unknown function in rust fungi
Authors: Pryor A. , Boelen M. G. , Dickinson M. J. , Lawrence G. J.
Published: February 2008

Double-stranded (ds) RNAs were found to be present in 33 of 38 collections of rust fungi, representing 15 species from four genera. This finding suggests that dsRNAs occur commonly in rust fungi. Tests were undertaken to determine the role or phenotype associated with the presence of dsRNAs. Comparisons were made between strains of Puccinia sorghi (maize rust) that had different dsRNAs and two fully isogenic strains of Melampsora lini (flax rust), one with no dsRNA and one with at least 13 dsRNAs. It was concluded that dsRNAs had no obvious effect on pathogen virulence or on growth rate as measured by rate of accumulation of leaf chitin or time to pustule eruption. Also it was demonstrated that the presence of dsRNAs had no effect on the interaction that exists between rusts over short distances in the leaf. Key words: dsRNA, rust, function, incidence.
New Cephaliophora species capturing rotifers and tardigrades
Authors: Barron G. L. , Morikawa C. , Saikawa M.
Published: February 2008

Cephaliophora muscicola and Cephaliophora longispora are new species of Hyphomycetes capturing rotifers and tardigrades using specialized adhesive pegs. Elongate, hyaline, multiseptate, canoe-shaped conidia are produced synchronously in small clusters at the apex of conidiophores, which arise at right angles from the vegetative hyphae. In the presence of rotifers, conidia germinate to produce one or several adhesive pegs. Rotifers and tardigrades are captured by the pegs, and subsequent growth forms an extensive network of hyphae bearing pegs and clusters of conidia. Cephaliophora muscicola was recovered from moss and forest debris in New Zealand and from leaf mould in Japan. Cephaliophora longispora was removed from mossy soil collected in New Zealand and from moss in Canada.
A new predatory Hyphomycete capturing copepods
Authors: Barron G. L.
Published: February 2008

Dactylella copepodii sp.nov. is described as a new predatory Hyphomycete capturing larval and adult stages of soil-inhabiting copepods. Capture is by adhesion to the swollen end cell of a hypha or lateral branch. Conidiophores are simple and each bears a large, hyaline, multiseptate, terminal, solitary conidium. In the presence of copepods, conidia germinate from the end cells to produce simple or sparingly branched hyphae bearing adhesive knobs at the tips. The relationship between Dactylella and Monacrosporium is discussed.
Desiccation causes the proliferation of multicellular hairs, but not mucilage papillae, in Cryptothallus mirabilis (Hepatophyta): a correlated light and electron microscope study
Authors: Duckett Jeffrey G. , Renzaglia Karen S. , Pell Keith
Published: February 2008

When Cryptothallus dries out over periods of 4–20 days, the dorsal surfaces of the thalli become covered with multicellular hairs. The distribution of mucilage papillae and the endophytic fungus are not affected by desiccation. The hairs are thin walled and highly vacuolated whereas the mucilage papillae, like their secretory counterparts in Marchantia and mosses, are thick walled with dense cytoplasm containing stacks of endoplasmic reticulum and numerous Golgi bodies. Cytochemistry shows that the secretion is rich in carbohydrates and is derived from Golgi vesicles. After an active secretory phase, senescence of the mucilage papillae is associated with acid phosphatase activity. Key words: Aneura, Cryptothallus, desiccation, liverwort, mucilage papilla, multicellular hair, ultrastructure.
Light-growth response relationships in Pacific silver fir (Abies amabilis) and subalpine fir (Abies lasiocarpd)
Authors: Klinka K. , Wang Q. , Kayahara G. J. , Carter R. E. , Blackwell B. A.
Published: February 2008

Pacific silver fir and subalpine fir, both typically inhabiting high-elevation forests in northwestern North America, were considered shade-tolerant species, the former more tolerant than the latter. To determine their relative shade tolerance, established advance regeneration was sampled along a light gradient ranging from open areas to inside a forest stand, and analysis of irradiance, growth, and leaf measures was obtained. Relationships between the percentage of above-canopy light (in the photosynthetically active wavelengths) associated with each study tree and its 1991 height increment, 1991 lateral increment, caliper at the base of the 1991 leader, and specific leaf area were examined for individual sites, and sites were grouped according to soil moisture. There were strong, consistent, and similar relationships between irradiance, growth performance, and specific leaf area for both species. As irradiance decreased, growth performance decreased and specific leaf area increased. In spite of ecological differences between the study sites for each species, it was concluded that on fresh sites, Pacific silver fir and subalpine fir are very tolerant of shade. Both are equally well adapted to survive under high shade and snowpack by allocating more resources to caliper and lateral growth than to height growth and by increasing specific leaf area. Key words: shade tolerance, advance regeneration, irradiance, growth performance, specific leaf area, Pacific silver fir, subalpine fir.
Environmental factors including management practices as correlates of weed community composition in spring seeded crops
Authors: Dale M. R. T. , Thomas A. G. , John E. A.
Published: February 2008

The relationship between the weed communities and environmental variables such as soil, crop, and management was investigated in two provinces of Canada. The frequencies of weed species were recorded in cereal and oilseed fields in Saskatchewan (2244 fields over 4 years) and Manitoba (864 fields over 3 years), Canada. Information on some of the physical characteristics of the fields and on the management practices imposed on them was also collected, in part by questionnaire. The two kinds of data were ordinated together using canonical correspondence analysis to assess the relationships between the species and the environmental variables. In the Saskatchewan data, there was a clear and consistent separation of the species into groups along an axis correlated with soil zone and the associated climatic gradient. In the Manitoba data, the same groups of species did not separate as clearly or as consistently, although geographic region was a major determinant of the weed communities. The greater variability may be due to the fact that the gradient of soil types is much more restricted in Manitoba and not as closely correlated with climatic conditions. In both provinces, culture practices were less important as correlates of the weed community composition than soil type or, to a certain extent, the previous crop. Key words: canonical correspondence analysis, cereal crops, oil seed crops.
Cytotaxonomic observations on North American Festuca (Poaceae)
Authors: Aiken Susan G. , Fedak George
Published: February 2008

The presence of B chromosomes is reported in Festuca altaica Trin., where a plant with relatively wide and often flat leaves had a chromosome number of 2n = 4x = 28; an adjacent plant, with conspicuously narrow and tightly rolled leaves, had 2n = 4x = 28 + 2B chromosomes. A first chromosome count of 2n = 42 is reported for Festuca rubra L. ssp. densiuscula (Hackel) Piper, along with observations on the nomenclature and morphology of this west coast subspecies. A first chromosome count for a North American plant of Festuca brevissima Jurtzev is 2n = 14. Collections made in northern Yukon were compared with the type borrowed from Leningrad and with the distribution of this species relative to the other North American diploid Festuca, Festuca aggr. auriculata Drob. A collection of Festuca brachyphylla Schultes from northern Yukon had a chromosome number of 2n = 42, and unusual morphology and phenology were interpreted as the result of a snow patch habitat. A second record for Festuca dasyclada Hackel ex. Beal of a chromosome number of 2n = 28 and justifications for keeping this species in Festuca are presented. Key words: Poaceae, North American, Festuca, chromosomes, morphology, nomenclature.
Genetic diversity among natural populations of Agathis borneensis (Araucariaceae), a tropical rain forest conifer from Brunei Darussalam, Borneo, Southeast Asia
Authors: Kitamura Keiko , Rahman Mohamad Yusof Bin Abdul
Published: February 2008

Agathis is a genus of tropical conifers that occurs mainly in Southeast Asia. Because of its production of good softwood, many stands of Agathis have been harvested. We provide an estimate of genetic variation within and among populations of Agathis borneensis in Brunei Darussalam, Southeast Asia. Five populations were investigated using isozyme electrophoresis. We investigated a total of 17 putative loci, five of which were polymorphic. Estimated total heterozygosity was 0.122. Heterozygosity within populations was 0.106. The population structure did not deviate significantly from Hardy–Weinberg expectations. Nei's coefficient of gene differentiation indicated that the among-population component of genetic diversity represents 14% of the total population component. The low level of genetic diversity and the large diversity among populations were the opposite of that for conifers in the temperate zone, because of the small size of each population. The large diversity among populations indicated the restricted gene flow resulting from the asynchronous flowering of this species. The genetic distance indicated that A. borneensis in Brunei could be classified in two groups, with one isolated population considerably different from the others both genetically and ecologically. The conservation strategy is discussed from the viewpoint of genetic resources. Key words: Agathis borneensis, Araucariaceae, Brunei Darussalam, genetic diversity, isozyme, tropical rain forest.
American chestnut survival in understory mesic sites following the chestnut blight pandemic
Authors: Griffin Gary J.
Published: February 2008

American chestnut survival was studied in 15 mesic understory sites located in the former oak–chestnut forest region of the eastern United States. Mesic deep coves and northeasterly slopes studied had no or low chestnut survival. Several shallow coves, north to northwesterly slopes, and a large cove slope examined had good chestnut survival. Live chestnut to chestnut stump ratios of 1 or greater were found on these sites. High canopy-tree basal area was not always associated with low chestnut survival, and vice versa. For five mesic sites studied in more detail, high chestnut survival was associated with higher basal areas for understory species (> 2.5 cm dbh) and frequency and basal area of red maple. Chestnut blight incidence was low or zero at these sites. Mesic sites, especially shallow coves, with surviving chestnuts may have the greatest potential for chestnut growth and biocontrol of blight, if effective hypovirulence, blight resistance, and forest management measures are developed. Key words: chestnut blight, forest competition, hypovirulence, biocontrol.
DNA sequence relationships and origins of acetohydroxy acid synthase genes of Brassica napus
Authors: Hattori J. , Rutledge R. G. , Miki B. L. , Baum B. R.
Published: February 2008

The allotetraploid Brassica napus has been shown to contain a five-member multigene family (AHAS1 – 5) of the nuclear-encoded chloroplastic enzyme acetohydroxy acid synthase, three members of which are expressed. AHAS1 and AHAS3 are constitutively expressed while AHAS2 expression is ovule- and seed-specific. By sequence and phylogenetic analyses we show that the AHAS1 and AHAS3 genes are 96–98% similar in the coding region and the adjacent 5′ and 3′ noncoding regions and were derived from a common ancestral crucifer gene. In contrast, the AHAS2 gene shares only about 80% sequence similarity with the AHAS1 and AHAS3 genes, limited to the region coding for the mature peptide and in a short region of the presumptive transit peptide. The AHAS2 gene likely arose by gene duplication of a housekeeping AHAS gene and has acquired characteristics different from other plant housekeeping AHAS genes, perhaps owing to different functional constraints. Key words: acetohydroxy acid synthase, Brassica napus, phylogenetic inference, multigene family, DNA sequence.
Teliospore wall structure in Entorrhiza (Tilletiaceae) and its relationship to taxonomy of the genus
Authors: Fineran Brian A. , Fineran Judith M.
Published: February 2008

Spore wall organization in the five species of Entorrhiza (Ustilaginales) has been investigated using thin sections for transmission electron microscopy, supported by light and scanning electron microscopy and some freeze-etching. Material was examined from herbaria, specimens preserved in fixative, and fresh host tissue. The wall has four main layers, numbered 1–4 from the outside to inside of the wall; some layers are further differentiated into zones. Layer 1 in E. aschersoniana, E. caspaiyana, and E. caricicola has two zones: a broad outer zone 2 of dense matrix and a narrow inner zone 1 of less compacted material. Zone 1 is absent in E. cypericola. In E. scirpicola, layer 1 is represented by discontinuous longitudinal ridges. In all spores, layer 2 is composed of a homogeneous electron-dense matrix. Layer 1 in E. aschersoniana, E. casparyana, and E. caricicola is uniformly thick, but in E. cypericola it is broad with an irregular outer margin. In E. scirpicola, layer 2 is differentiated into a distinctive pattern of longitudinal ribs. In all spores of Entorrhiza, layer 3 is resolvable into fine lamellae, corresponding to the mosaic of striations seen after freeze-etching. Layer 3 in Entorrhiza is equivalent to the partition layer described in other Tilletiaceae. Layer 4 has the same organization in all the species, consisting of a very narrow zone 2 abutting layer 3 and a broad zone 1 that forms the rest of the layer. Based on wall structure, E. aschersoniana and E. casparyana represent the most closely related species, followed by E. caricicola, with E. cypericola more distant again. Entorrhiza scirpicola is considered the least related of the species; only its layers 3 and 4 resemble the other species. Key words: Entorrhiza, Tilletiaceae, spore wall ultrastructure, species relationships.
Distribution of unusual polyamines in leguminous seeds
Authors: Hamana Koei , Matsuzaki Shigeru , Niitsu Masaru , Samejima Keijiro
Published: February 2008

Polyamines of 18 leguminous mature seeds were analyzed by high-performance liquid chromatography and gas chromatography – mass spectrometry. Putrescine, spermidine, and spermine occurred ubiquitously and cadaverine, agmatine, and homospermidine were sporadically found in these seeds. Six unusual polyamines, i.e., canavalmine [NH2(CH2)4NH(CH2)3NH(CH2)4NH2], homospermine [NH2(CH2)4NH(CH2)4NH(CH2)4NH2], aminopropylcanavalmine [NH2(CH2)3NH(CH2)4NH(CH2)3NH(CH2)4NH2], thermospermine [NH2(CH2)3NH(CH2)3NH(CH2)4NH2], and aminopropylhomospermidine [NH2(CH2)3NH(CH2)4NH(CH2)4NH2] were found in the seeds of Pisum sativum. Thermospermine and aminopropylhomospermidine were also detected in the seeds of Vicia hirsuta and Trifolium pratense, respectively. An unusual tetraamine, norspermine [NH2(CH2)3NH(CH2)3NH(CH2)3NH2], was found in the seeds of Medicago sativa and Vicia faba. The seeds of Phaseolus coccineus contained homospermine and a tertiary branched pentaamine, N5-aminobutylhomospermine [NH2(CH2)4N((CH2)4NH2)(CH2)4NH(CH2)4NH2]. Key words: poly amine, legume, seed.
Cytologie et histologie de la reproduction chez le Nymphaea heudelotii
Authors: Miegroet Françoise Van , Dujardin Michel
Published: February 2008

The ontogenesis of reproductive cells has been cytologically analysed in Nymphaea heudelotii Planch., family Nymphaea-ceae, subclass Magnoliidae. Our observations of embryo sac development on sections differ from those made by Cook in 1906. Embryo sacs derive from a single functional megaspore and are four nucleate. After fertilization, the polar nucleus divides and successively generates two storage tissues that are located in two separate chambers. Nucellar tissue, which is filling up with starch inclusions, then insures a storage function. This species possesses 14 bivalents at meiosis and 14 somatic chromosomes at the first mitosis of the pollen grain. A reorganization of amyliferous organelle aggregates has also been observed in microsporocytes. Key words: reproduction, embryogenesis, microsporogenesis, megasporogenesis, Nymphaea.