bluuebunny/crossref_metadata_2025 huggingface dataset:
An evaluation of the ecological hazards associated with cadmium in the Canadian environment
Authors: Outridge P. M. , MacDonald D. D. , Porter E. , Cuthbert I. D.
Published: April 2011

This review was conducted to evaluate the potential hazards associated with releases of cadmium (Cd) into the Canadian environment. The hazard assessment consists of three elements: a focused review of the available data on the toxicology of Cd in various environmental media, a review of the available information on the concentrations of Cd in the Canadian environment, and a comparison of these data. Based on the review of the toxicological literature, the following lowest observed effect concentrations (LOECs) of Cd were identified for the most sensitive species: 0.17 μg∙L−1 in freshwater at a hardness of 48.5 mg∙L−1, 3.5 mg∙kg dry weight (DW)−1 in freshwater sediments, 1.2 μg∙L−1 in marine waters, 4.2 mg∙kg DW−1 in marine sediments, and, 2.0 mg∙kg DW−1 in soil. The freshwater LOEC was adjusted for hardness by a regression equation, so that LOECs could be estimated for waters of varying hardnesses; these LOECs ranged from 0.004 μg∙L−1at a hardness of 1 mg∙L−1 to 0.99 μg∙L−1 at a hardness of 300 mg∙L−1. Critical tissue concentrations (CTCs) in kidneys of 100 mg∙kg fresh weight (FW)−1 for birds and 30 mg∙kg FW−1 for mammals were also identified. Comparison of the empirically derived LOECs and CTCs with concentrations of Cd in Canadian ecosystems suggested that sensitive biota in the following environments may be adversely affected in some locations: surface freshwaters, freshwater and marine sediments, and soils. Some marine mammals, ungulates, and domestic horses are also at risk because of high renal Cd concentrations. The LOECs were exceeded most seriously in the vicinity of base metal smelters, indicating that these smelters represent significant hazards to local aquatic and terrestrial biota. In parts of Ontario, catchment acidification and deposition of aeolian Cd, presumably from other industrial sources, also appear to contribute to elevated Cd concentrations in freshwater systems. The extent and severity of contamination suggest that Cd is a significant threat to the integrity of Canadian ecosystems.Key words: cadmium, Canada, toxicology, contamination, hazard evaluation.
The relationship between root morphology and cadmium accumulation in seedlings of two durum wheat cultivars
Authors: Berkelaar Edward , Hale Beverley
Published: April 2011

Two cultivars of durum wheat (Triticum turgidum L.) with known, and different, grain-Cd accumulation were used to compare root tissue accumulation of Cd with root morphology. Six-day-old 'Kyle' and 'Arcola' seedlings were exposed to a range of Cd2 + concentrations (3.91 × 10-8 - 3.91 × 10-7 M) for 0-200 min, and root Cd contents for the two cultivars were compared with root morphological characteristics. 'Kyle' roots contained 35% less Cd per root system after 200 min of exposure and had less root surface area and fewer root tips than 'Arcola'. 'Kyle' roots also contained 30% less Cd per gram of dry weight than 'Arcola' roots after 200 min of exposure. 'Kyle' roots also had fewer root tips per unit of root dry weight and less surface area per unit of dry weight (DW) than 'Arcola'. When cadmium concentration data (µg·g-1 DW) were expressed per unit of root surface area (µg·cm-2) and per number of root tips (µg·tip-1), the difference in root Cd content between the two cultivars was smaller. These results suggest that greater root Cd content of 'Arcola' than 'Kyle' can be explained by differences in morphology, specifically that a greater surface area and more root tips in 'Arcola' leads to greater Cd accumulation in root tissue.Key words: cadmium accumulation, durum wheat, root morphology.
Seed production of a masting dwarf shrub, Vaccinium myrtillus, in relation to previous reproduction and weather
Authors: Selås Vidar
Published: April 2011

In an analysis of a 50-year time series of seed production in bilberry (Vaccinium myrtillus L.) from Aust-Agder, southern Norway, both previous reproduction and weather contributed to explain annual berry production. There was a relatively regular fluctuation in bilberry production, with intervals between peaks of 2-5 years. The bilberry-production index was negatively correlated with the average bilberry production index of the preceding 3 years. Regularity in the bilberry production was commonly interrupted by unfavourable weather conditions. Depressed bilberry reproduction was associated with high temperatures during flower-bud formation in autumn, high temperatures in winters with thin snow cover, low temperatures during flowering in spring, and low or high amounts of precipitation during berry ripening in summer. It was concluded that, in Fennoscandia, climatic conditions may be responsible for the temporal and spatial synchrony in seed production in bilberry.Key words: bilberry, climate, mast, reproduction, synchrony, weather.
Clonal growth and storage in relation to competition in genets of the rhizomatous perennial Amphibromus scabrivalvis
Authors: Cheplick Gregory P , Gutierrez Christine M
Published: April 2011

The grass Amphibromus scabrivalvis Trin. Swallen produces new ramets from the base of established ramets (to produce a phalanx growth form) and along rhizomes (to produce a guerrilla growth form). It stores resources in stem bases. This research examined genotypic variation in clonal growth and storage and its relation to the performance of replicated genets under competition. It was hypothesized that (i) genets would vary significantly in traits important to clonal growth and storage during competition, (ii) competition would reduce clonal growth capability, (iii) guerrilla-like spacing would enhance clonal growth under competition at low competitor density, and (iv) allocation to storage organs would increase under competition. Fourteen genets of A. scabrivalvis were divided into ramets and planted into pots in the glasshouse alone or in competition with four equally distributed seedlings of Lolium perenne L., a phalanx competitor. Leaf area and mass, as well as the distance of new ramets from the parental ramet, were measured at 9 and 18 weeks. Dry mass of leaves, stem bases, rhizomes, and roots was determined at 18 weeks. Relative competition intensity, based on the difference in total mass per genet between control and competition treatments relative to the control, varied between 0.69 and 0.83. Ramet production, the proportion of the total leaf area in new ramets, and ramet distances varied significantly among genets and were reduced by competition. Mean ramet distance was positively correlated with total mass. Allocation of dry mass to storage organs was significantly increased under competition and may allow genet persistence within an occupied area. The relative ranking of genets in the control and competition treatment was not different, and there were no differences in the relative degree to which the total mass of genets was reduced by competition, despite significant variation in total mass accumulated in the absence of competition.Key words: Amphibromus scabrivalvis, clonal grass, competition, genotypic variation, guerrilla strategies, phalanx strategies, rhizomatous perennial.
Endolithic algae and cyanobacteria from cliffs of the Niagara Escarpment, Ontario, Canada
Authors: Gerrath J F , Gerrath J A , Matthes U , Larson D W
Published: April 2011

A comprehensive survey for endolithic organisms was undertaken to evaluate the distribution of endolithic algae and cyanobacteria in the structure of ancient cliff ecosystems of the Niagara Escarpment. Rocks were collected at 12 sites along the escarpment. Three rock samples were collected from each of five transects for a total of 180 rock samples. Cryptoendolithic or chasmoendolithic organisms were extracted from freshly cleaved faces under laboratory conditions, and attempts were made to culture, grow, and identify these organisms. Cultures of cryptoendolithic organisms were successfully obtained from between 6.7 and 40% of the culture plates from any one site, whereas chasmoendolithic organisms were obtained from 98% of the attempts. Twenty-two taxa were found, including some Cyanophyta that were present at most sites (Chlorogloea) and others that were found rarely (Schizothrix). Cyanophytes were more common at northern sites than southern sites. Among the Chlorophyta, Stichococcus bacillaris was ubiquitous, but Stichococcus exiguus was restricted to one site. The chlorophytes were evenly found along the Escarpment. No geographical trends were obvious among the Xanthophyceae, but some taxa such as Chloridella neglecta were common and others such as Ellipsoidion stichococcoides were not. These results suggest that endolithic organisms within the rocky limestone cliffs of the Niagara Escarpment are not uniform in abundance or species composition. Consequently, management plans intended to maintain microbial species diversity in the face of different patterns of land use and environmental pollution may have to be location-specific along the escarpment.Key words: terrestrial algae, cryptoendolithic organisms, cliffs, Niagara Escarpment.
An initial assessment of genetic relationships among populations ofFusarium circinatumin different parts of the world
Authors: Wikler Karen , Gordon Thomas R
Published: April 2011

Fusarium circinatum Nirenberg & O'Donnell, the fungus responsible for pitch canker disease, is a destructive pathogen of Pinus spp. Pitch canker was first described in 1946 in the southeastern United States, and since 1987 has been reported in numerous other locations including California, Mexico, Japan, and South Africa. To make a preliminary assessment of relationships between populations of F. circinatum in these different locations, we compared allele and genotype frequencies based on eight polymorphic regions of DNA from 76 isolates of the fungus. Patterns of relatedness indicate that the California and Japanese populations of the fungus share lineages with the southeastern U.S.A. population. Genetic diversity is highest in Mexico, implicating it as the center of origin for the fungus. The association of multiple vegetative compatibility groups with a common multilocus genotype suggests that vegetative compatible group diversity may be generated by mutation, rather than through recombination resulting from sexual reproduction.Key words: genomic subtraction, tree disease, genetic distance.
Indicators of population viability in red spruce, Picea rubens. I. Reproductive traits and fecundity
Authors: Mosseler A , Major J E , Simpson J D , Daigle B , Lange K , Park Y -S , Johnsen K H , Rajora O P
Published: April 2011

Red spruce (Picea rubens Sarg.) has experienced a substantial decline across most of its range in eastern North America over the past century and probably also in the disjunct Ontario populations where it now occurs only in small isolated stands. Measurements of cone and seed traits from natural populations were used as indicators of the reproductive and genetic status of red spruce across the northern margins of its range in Canada. Cone and seed traits were quantified to provide reproductive benchmarks for assessing and monitoring population viability. Reduced fecundity and seedling height growth were observed in some of the smallest Ontario populations, suggesting some inbreeding depression in both vegetative and reproductive components of fitness. Nevertheless, the reproductive status of these small isolated Ontario populations compared favorably with the much larger, more extensive Maritime populations in Nova Scotia and New Brunswick. Significantly higher proportions of aborted (nonpollinated) seeds and lower proportions of filled seeds suggested poorer pollination conditions in the Maritimes in 1996. The proportion of empty seed, which was used to estimate inbreeding levels, was significantly and negatively related to seedling height growth. In the short-term, the Ontario populations, which probably represent relatively recent remnants of a broader past distribution, generally appeared to be quite resilient to the effects of small population size on fecundity and progeny fitness. In the longer term, continuing decline in population sizes and numbers may be expected to erode reproductive success and genetic diversity through the effects of inbreeding, genetic drift, and changes in mating behavior. The reproductive indicators described here have general validity for assessing and monitoring reproductive and genetic aspects of population viability in conifers.Key words: Picea rubens, reproductive success, reproductive fitness indicators, inbreeding, population viability, conservation.
On the phylogeny of members of Ceratocystis s.s. and Ophiostoma that possess different anamorphic states, with emphasis on the anamorph genus Leptographium, based on partial ribosomal DNA sequences
Authors: Hausner Georg , Reid James , Klassen Glen R
Published: April 2011

Phylogenetic analysis of partial ribosomal DNA sequences was undertaken to assess the phylogenetic distribution of ophiostomatoid anamorphs with an emphasis on members of Leptographium and the generic limits of Ceratocystis sensu lato Ell. & Halst. Molecular data identified one group of Ophiostoma species with anamorphs assignable to Pesotum and Leptographium that appears to be monophyletic. This study also showed that, based on molecular characters, Pesotum pini (Hutchison & Reid) Okada and all Leptographium strains tested, including L. terebrantis Barras & Perry, L. lundbergii Lag. & Melin, and L. procerum (Kendr.) Wingf., could be placed among Ophiostoma species. With regard to the anamorphs of Ophiostoma, we determined that the separation of Leptographium from Pesotum, although convenient, is artificial. The partial ribosomal DNA sequences also confirm that Europhium should be considered a synonym of Ophiostoma. The phylogenetic position of species of Ceratocystis sensu lato with Chalara-like, Knoxdaviesia, and Gabarnaudia anamorphs is also discussed.Key words: Ceratocystis, Ophiostoma, Leptographium, partial rDNA sequences, phylogeny.
Genetic variability and phylogeny inferred from random amplified polymorphic DNA data reflect life strategy of entomopathogenic fungi
Authors: Oborník Miroslav , Klíc Marek , Zizka Luká
Published: April 2011

Our analysis of the genetic variability and phylogenetic relationships among the isolates of mitosporic entomopathogenic fungi Paecilomyces fumosoroseus (Wize) Brown & Smith (10 isolates), Paecilomyces farinosus (Holm ex S.F. Gray) Brown & Smith (3 isolates), Paecilomyces lilacinus (Thom) Samson (1 isolate), and Verticillium lecanii (Zimmerman) Viegas (6 isolates) was based on the use of random amplified polymorphic DNA (RAPD) markers. Neighbor-joining analysis characterized P. fumosoroseus and V. lecanii as monophyletic taxa. The analysis also supported monophyly of the genus Paecilomyces. We have used the distribution of genetic distances to demonstrate the genetic variability within studied species, in Paecilomyces spp. (Hyphomycetes) and Aschersonia spp. (Coelomycetes) in particular. We conclude that the RAPD-based analysis is useful for the reconstruction of intraspecific and interspecific relationships of the entomopathogenic fungi. Moreover, it can be employed to study the intergeneric relationships, especially in the case of closely related genera of the hyphomycetous entomopathogenic fungi. We propose that RAPD-based phylogeny and genetic variability reflect their life strategy. In our opinion, the mobility of spores represents a factor with major influence on the evolution of these entomopathogenic fungi.Key words: Paecilomyces, Verticillium, Aschersonia, RAPD, phylogeny, genetic variability.
Plant-size and fruit-position effects on reproductive allocation in Alliaria petiolata (Brassicaceae)
Authors: Susko David J , Lovett-Doust Lesley
Published: April 2011

We examined the development of ovules and components of reproductive yield as they related to plant size and fruit position within plants of Alliaria petiolata (M. Bieb.) Cavara and Grande from three sites. We found that both factors affected fruit and seed production, and patterns of ovule fate. Larger plants were more fecund than their smaller counterparts, while proximally positioned flowers within an inflorescence produced more seeds. Maternal investment was regulated according to plant mass at two levels: among fruits (small plants had significantly lower fruit-set than did large plants), and within fruits (small plants had significantly fewer ovules and significantly higher proportions of aborted ovules per fruit than did large plants). All absolute measures of reproduction had positive linear relationships with plant size, but a threshold size for flowering was not found. Most proportional measures of reproduction were independent of plant size. Small plants produced the same relative proportions of total seed number and total seed mass per unit plant dry mass as large plants. Therefore, proportional reproductive allocation did not vary with plant size. However, small plants produced proportionately more flowers per unit dry mass. Small plants may be maximizing their overall fitness through increased allocation to male function (flower production).Key words: Alliaria petiolata, plant-size effects, fruit-position effects, reproductive allocation, patterns of ovule abortion, seed maturation.
Cultivation of rue (Ruta graveolens L., Rutaceae) for the production of furanocoumarins of therapeutic value
Authors: Poutaraud Anne , Bourgaud Frédéric , Girardin Philippe , Gontier Eric
Published: April 2011

Common rue (Ruta graveolens L.) synthesizes furanocoumarins, which are used in dermatology. The production of these molecules requires the improvement of cultural techniques so as to provide plant material with a high content and (or) yield of furanocoumarins for the pharmaceutical extraction industry. Two experiments were set up, firstly, to improve our understanding of the production of these secondary metabolites by the plant and, secondly, to study the influence of successive cuts on their synthesis. The furanocoumarin content was dependent on the proportion of leaves and fruits on the plant. Conversely, it was independent of the biomass at a given age. The shoots harvested 3 months after sowing had a high furanocoumarin content, as did the fruits in the 2nd year (in both cases about 0.9% of the dry matter). However, the dry matter yield produced was low (0.2 and 1.6 tonnes·ha-1, respectively). The harvest of the shoots in the 2nd year gave a high yield (about 5 tonnes·ha-1) but had a lower furanocoumarin content (0.4%). A system of successive cuts (three cuts in the 2nd year) enabled harvesting to be spread out. The plant material then contained 0.5% furanocoumarins, for 3.3 tonnes of dry matter harvested. The proportion of different furanocoumarins varied according to year and plant parts.Key words: Ruta graveolens L., furanocoumarin, cultivation, cuts, secondary metabolite, Rutaceae.
Acclimation to light in planted and naturally regenerated populations of white spruce seedlings
Authors: Awada Tala , Redmann Robert E
Published: April 2011

Physiological responses to sun and shade were examined in white spruce (Picea glauca (Moench) Voss) seedlings collected from three naturally regenerated (N1-N3) and three planted (P1-P3) stands in the boreal forest of Saskatchewan. Seedling survival was greater in the sun than in the shade pretreatment periods. Dark respiration declined by 70% in shade- compared with sun-acclimated seedlings; however, the decline was not statistically significant because of the large within-population variation. Quantum yield, total chlorophyll content, specific leaf area, and absolute water content of needles increased by 45, 33, 32, and 50%, respectively, in response to shade. At low light levels, shade-acclimated populations showed greater photosynthetic rates and steeper light-response curves than seedlings growing in full sun. Seedlings of P3, N2. and N3 saturated at about 200 µmol·m-2·s-1 PAR in the shade, with no increase in photosynthesis at higher light intensities. At light saturation, populations P1 and N3 showed similar photosynthetic rates to both light acclimation regimes; populations P2, P3, and N2 had lower light-saturated photosynthesis in sun, compared with shade pretreatment. Only in N1 was photosynthetic rate greater after sun than shade pretreatment; this population behaved like a "sun" and "shade" population depending on pretreatment. Differences in physiological responses to light among populations suggest the presence of more than one ecotype. N1 showed the greatest plasticity in response to light pretreatment. The remaining populations behaved more like shade-adapted populations, with little adjustment to light conditions. Intrapopulation variation was large for both regeneration types. It appears that selection pressure during reforestation was not great enough to cause a decline in intrapopulation variation in planted compared with naturally regenerated white spruce seedlings.Key words: Picea glauca, white spruce, light acclimation, photosynthesis.
Determination of the origin of the cold-adapted populations of barnyard grass (Echinochloa crus-galli) in eastern North America: a total-evidence approach using RAPD DNA and DNA sequences
Authors: Roy Sophie , Simon Jean-Pierre , Lapointe François-Joseph
Published: April 2011

This survey attempts to establish the origin of cold-adapted populations of barnyard grass (Echinochloa crus-galli (L.) Beauv.) in North America using molecular techniques, including random amplified polymorphic DNA (RAPD) and two types of sequences: chloroplast intron (trnL (UAA)) and rDNA nuclear spacer (ITS 1). There exists many possible scenarios to explain the origin of E. crus-galli in eastern Canada (Quebec), but we dwelled on two particular hypotheses, which are not mutually exclusive. The first hypothesis stipulates that the populations originated only from Europe, whereas the second implies that native subtropical and warm-temperate populations migrated from the south towards northern regions. To assess the likelihood of these hypotheses, the genetic distance matrices obtained from RAPD markers, nuclear, and chloroplastic sequences were combined and tested against the competing models. A principal coordinate analysis was used to discriminate among populations sampled from three different regions (i.e., Quebec, American east coast, and western Europe) and an analysis of molecular variance (AMOVA) detected a significant genetic structure among these populations (FST= 0.110, p < 0.05). Pairwise comparisons further indicated that European populations were significantly different from all other populations, whereas North American populations were not different from one another. The combined sequences revealed eight different haplotypes. Six populations were characterized by unique haplotypes, while one haplotype was shared by 3 of the 12 North American populations. The last and most common haplotype was observed in 9 of the 18 populations from all three regions. The tests computed thus supported the second hypothesis suggesting that the cold-adapted populations of eastern Canada are probably derived from other North American populations rather than European populations.Key words: AMOVA, RAPD, rDNA, cpDNA, genetic variation, population structure.
A taxonomic re-evaluation of Phialocephala phycomyces
Authors: Jacobs K , Wingfield M J , Jacobs A , Wingfield B D
Published: April 2011

Phialocephala was established for species that produce their conidia from phialides at the apex of dark mononematous conidiophores. Phialocephala phycomyces (Auersw.) Kendrick was described more than a century ago as the only species of the genus Hantzschia. The phialides of P. phycomyces are not as deep-seated as those found in Phialocephala dimorphospora Kendrick, the type of Phialocephala, and conidium development occurs near the apex of the conidiogenous cell. Furthermore, P. phycomyces is characterized by reddish-brown conidiophores and is cycloheximide resistant. Based on morphological, as well as molecular comparisons, we concluded that P. phycomyces is a distinct genus, Kendrickiella gen.nov.Key words: Leptographium complex, morphology, phylogeny, Phialocephala, Kendrickiella.
Impact of a major ice storm on an old-growth hardwood forest
Authors: Hooper Michael C , Arii Ken , Lechowicz Martin J
Published: April 2011

We quantified the amount of woody biomass and volume lost in an old-growth hardwood forest at Mont St. Hilaire, Quebec, as a consequence of a major ice storm. The storm of January 1998 brought down 19.9 (air-dried) metric tons or 33.6 m3 of woody debris per hectare. This is about 7-10% of the total aboveground biomass in this forest before the storm and is about 10-20 times greater than the annual production of woody litter typical for temperate deciduous forests in northeastern North America. The woody biomass lost is the greatest recorded for any ice storm. The impact of this ice storm ranks among that of the most damaging windstorms and hurricanes recorded in forested landscapes anywhere.Key words: glaze ice, forest disturbance, forest damage, tree biomechanics, forest dynamics, forest productivity.
Imaging arbuscular mycorrhizal structures in living roots of Nicotiana tabacum by light, epifluorescence, and confocal laser scanning microscopy
Authors: Vierheilig Horst , Knoblauch Michael , Juergensen Katja , van Bel Aart JE , Grundler Florian MW , Piché Yves
Published: April 2011

Light and epifluorescence (blue light excitation) microscopy was used to obtain micrographs of the same sections of unstained (living roots) and stained (dead) tobacco (Nicotiana tabacum L.) roots colonized by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe. To visualize all mycorrhizal structures, roots were in situ stained with trypan blue. The metabolically active fungal tissue was determined by an in situ succinate dehydrogenase stain. A comparison of micrographs of unstained and stained mycorrhizal tobacco roots revealed that (i) finely branched arbuscules do not autofluoresce, but high autofluorescence was observed in clumped structures of collapsed arbuscules; and (ii) finely branched arbuscules are metabolically active, but no activity can be detected in autofluorescent collapsed arbuscules. Confocal laser scanning microscopy was used in combination with the two fluorochromes 5(6)-carboxyfluorescein diacetate or 5(6)-carboxy-seminaphthorhodafluor. Both fluorochromes administered to abraded tobacco leaves are transported via the phloem to the roots. Loading plants with 5(6)-carboxyfluorescein diacetate resulted in a fluorescence of root cells with highly branched arbuscules. After loading the phloem with 5(6)-carboxy-seminaphthorhodafluor, all fungal structures in the root (from relatively thick hyphae to finest branches of arbuscules) were clearly visible in the intact root. The transport route of compounds from the plants to arbuscular mycorrhizal fungi is discussed.Key words: Glomales, mycorrhiza, fluorescence, SDH, confocal, transport.
Macrophyte succession in Minnesota beaver ponds
Authors: Ray A M , Rebertus A J , Ray H L
Published: April 2011

Beavers (Castor canadensis Kuhl.) are keystone species that dramatically alter nutrient cycles and food webs in aquatic and terrestrial ecosystems by modifying their hydrology and selectively removing riparian trees. We documented macrophyte succession in 36 beaver ponds ranging from 4 to over 40 years old. We used impounded bogs, because they were isolated from other waterbodies and less prone to washout. Richness and diversity increased linearly in ponds during the first four decades. Pond age and the product of pond size and the number of neighboring ponds in a 0.25-km radius explained 64% (p = 0.001) of the variation in richness. Compositional trends were best explained by propagule dispersal traits. Initial colonists included vagile species, like free-floating macrophytes and desirable foods for waterfowl, like the narrow-leaved pondweeds. Ponds of intermediate age (1140 years) had the highest diversity, with both floating-leaved and submersed life forms represented. Two community types were identified in older ponds: one characterized by dense lily pad cover and the other characterized by a rich assemblage of Potamogeton. By developing a predictive model for macrophyte succession in beaver ponds, we provide a basis for studying a variety of ecological processes and organisms that depend on macrophytes in these regionally abundant habitats.Key words: macrophyte, succession, beaver, bogs, Minnesota, pond.
The teleomorph of the weakly aggressive segregate ofLeptosphaeriamaculans
Authors: Shoemaker R A , Brun Hortense
Published: April 2011

Leptosphaeria biglobosa n.sp. is described for the weakly virulent (or non-aggressive) pathogen causing blackleg of oilseed rape and canola. The new species differs from the aggressive blackleg organism, Leptosphaeria maculans (Desm.) Ces. & De Not. in having a very prominent beak on the ascomata that is greatly enlarged at the apex. Ascomata of both species were produced on canola stems either by inoculation of compatible strains of the Phoma anamorph or by single ascospore isolates at a distance of 1 cm and letting them grow together. Both species exhibit bipolar heterothallism. Interspecific crosses were negative. In a study of type specimens of Leptosphaeria species with 5-septate ascospores infecting Cruciferae, none were found that matched the features of L. biglobosa. Leptosphaeria napi (Fuckel) Saccardo on Brassica napus L., and Leptosphaeria virginica (Cooke & Ellis) Saccardo on Lepidium virginica L., are synonyms of L. maculans. Leptosphaeria submaculans Holm on Sisymbrium, Berteroa, and Erysimum has distinctively enlarged ascospores. Leptosphaeria alliariae (Desm.) Ces. & De Not. on Alliaria officinalis Andrz., has much smaller ascospores. Leptosphaeria lindquistii Frezzi on Helianthus annuus L. of the Asteraceae has ascospores with only one, two, or rarely, three septa but was considered because it too has a Phoma anamorph.Key words: Phoma lingam, B group, ascomata.
Cytosolic acidification and γ-aminobutyric acid synthesis during the oxidative burst in isolatedAsparagus sprengerimesophyll cells
Authors: Janzen David J , Allen Lisa J , MacGregor Kennaway B , Bown Alan W
Published: April 2011

The four carbon, non-protein amino acid γ-aminobutyrate (GABA) accumulates rapidly in response to diverse stresses. Its synthesis is stimulated by increases in intracellular Ca2+or H+levels. The pathogen-induced oxidative burst is also associated with increases in Ca2+and H+levels. This study investigated the relationship between GABA synthesis and the oxidative burst. A Mas-7-induced consumption of oxygen in isolated Asparagus sprengeri Regel mesophyll cells was accompanied by rapid GABA synthesis. At pH 5.0, a 300% increase occurred within 16 min from 6.6 to 26.3 nmol GABA·106cells1. At pH 6.0, the increase was from 8.5 to 18.1 nmol GABA·106cells1. Mas-7 also stimulated rapid external alkalinization and intracellular acidification. Intracellular pH decreased 0.44 pH units at pH 5.0, and 0.21 pH units at pH 6.0. The Mas-7-induced oxidative burst, GABA synthesis, extracellular alkalinization, and intracellular acidification were all eliminated when lanthanum, a Ca2+channel blocker, replaced Ca2+in the incubation medium. The data demonstrate that GABA accumulation is associated with the oxidative burst, and results from the fluxes of H+and Ca2+, which are known to accompany the oxidative burst. They are discussed in light of emerging data that indicate a role for GABA in plant cell to cell signaling.Key words: γ-aminobutyric acid, GABA, oxidative burst.
Armillaria sinapina in herbaceous plant material from a peatland in Alberta, Canada
Authors: Thormann Markus N , Myrholm Colin L , Mallett Ken I
Published: April 2011

Armillaria sinapina Bérubé & Dessureault mycelium was isolated once from living Carex aquatilis Wahlenb. rhizomes, twice from decomposing C. aquatilis leaves, and three times from decomposing Salix planifolia Pursh leaves in a southern boreal sedge-dominated fen in Alberta, Canada. Restriction fragment length polymorphism (RFLP) analyses of the IGS-1 region with the AluI restriction enzyme were used to identify the isolates, because conspicuous, epigeous basidiomes could not be found in or near the fen. During these analyses, two previously unpublished fragment patterns for A. sinapina were found, consisting of 399240135 base pairs (bp) and 399240183135 bp. Interspecific somatic incompatibility and interfertility tests confirmed the identifications obtained from the RFLP analyses. This is the first report of an annulate species of Armillaria being actively involved in the colonization and decomposition of herbaceous plant material in an ecosystem having only an organic soil horizon. Surveys for species of Armillaria should be expanded to include peatlands and herbaceous plant materials, because they may serve as vast potential biomass and genetic diversity reservoirs for this genus.Key words: peatland, Carex rhizomes, Salix leaves, RFLP, interspecific somatic incompatibility, interfertility.
Holocene climate changes reflected in a diatom succession from Basaltsø, East Greenland
Authors: Cremer Holger , Melles Martin , Wagner Bernd
Published: April 2011

Information on Holocene lacustrine diatom records from Greenland is rare. Here, a complete Holocene diatom succession is described from a sediment core recovered from Basaltsø, an arctic lake on Geographical Society Ø, eastern Greenland. Based on radiocarbon measurements on plant material, the upper 2.42 m of the 9.85 m long sediment sequence represent the Holocene sedimentological record in this area from about 10 000 calibrated (cal.) years BP. The diatom assemblages in Basaltsø are dominated by only a few species. Four stratigraphic diatom zones could be distinguished. During the early Holocene, mainly Staurosira construens (Ehr.) Williams et Round, Nitzschia amphibia Grunow, and Pinnularia mesolepta (Ehr.) W. Smith were the dominant taxa. After this initial stage, between 9600 and 5000 cal. years BP, Staurosirella pinnata (Ehr.) Williams et Round was the most abundant diatom species. From 4500 to 500 cal. years BP, the diatom assemblage was characterized by the co-occurrence of several taxa, including S. construens. S. pinnata, Kolbesia suchlandtii (Hust.) Kingston, and Cyclotella sp. A (rossiitripartitacomensis complex) as the main contributors. Finally, from 500 cal. years BP, the diatom assemblage was clearly dominated by Cyclotella sp. A, Cyclotella pseudostelligera Hustedt, and Sellaphora spp. The Holocene relative frequencies of S. pinnata and S. construens clearly correlate with the total diatom valve concentration, the Betula and Salix pollen percentage in Basaltsø, and the oxygen isotope record from the Renland ice core. This suggests that S. pinnata and S. construens are temperature-sensitive species that responded on the general climatic development in eastern Greenland during the Holocene. The diatom record together with the pollen and geochemical data of Basaltsø indicate to the Holocene climatic optimum on Geographical Society Ø from ca. 9000 to 6500 cal. years BP.Key words: Arctic, Greenland, Holocene, diatoms, paleolimnology, environmental change.
Responses of carbon and nitrogen concentrations in high arctic plants to experimental warming
Authors: Tolvanen Anne , Henry Gregory HR
Published: April 2011

We studied total carbon (C) and nitrogen (N) concentration in five arctic plant species, Cassiope tetragona (L.) D. Don (evergreen dwarf shrub), Dryas integrifolia Vahl (semi-evergreen dwarf-shrub), Salix arctica Pall. (deciduous, dioecious dwarf shrub), Oxyria digyna (L.) Hill (forb), and Carex stans Drej. (graminoid, sedge), after five growing seasons of experimental increase in temperature. The experiments were established in different habitats along a moisture gradient in a coastal lowland at Alexandra Fiord, Ellesmere Island (79ºN). Sampling was conducted three times during the growing season. The seasonal patterns of C and N concentration were similar across all investigated species, even though the absolute concentrations differed. Nitrogen concentrations were high early in the season during the active growth period but declined later in the season. Warming decreased the N concentration and increased the C/N ratio in the three woody species, whereas N concentrations in the forb and the sedge were not affected. Although not measured directly in our study, the differences in concentrations may be due to the slower response in nutrient uptake and growth in the dwarf shrubs but increased nutrient uptake and growth in the forb and the sedge. Among-site differences were only significant in C concentrations of old tissues of Cassiope tetragona and S. arctica. Male and female S. arctica did not differ in their responses to warming. Differences among plant species in their plastic responses may relate to survival during rapid environmental change. Slow-responding dwarf shrubs may be under increased risk of competition from more responsive and faster growing species, such as forbs and graminoids.Key words: allocation, climate change, dwarf shrub, forb, graminoid, ITEX, Ellesmere Island.
Ungulate damage on Scots pines in Mediterranean environments: effects of association with shrubs
Authors: Gómez José M , Hódar José A , Zamora Regino , Castro Jorge , García Daniel
Published: April 2011

The spatial structure of plant communities as well as the quality and abundance of neighbours can strongly influence the intensity of herbivory suffered by a plant. In this paper, we study the effect of the association with shrubs on the ungulate herbivory suffered by Scots pine (Pinus sylvestris var. nevadensis Christ., Pinaceae) saplings in two isolated, fragmented populations in southeastern Spain. For this, we monitored herbivory on saplings with regard to the microhabitat in which they grew. We distinguished pines growing in open interspaces, on the edge of shrubs and within the canopy of shrubs, and also we distinguished four functional types of shrubs: thorny shrubs, nonthorny shrubs, thorny scrubs, and nonthorny scrubs. Our results show that association with shrubs increases the damage inflicted on Scots pine saplings. In fact, saplings growing in the open patches, far from the shrubs, escaped from herbivory more frequently and incurred less damage than did saplings growing close to shrubs. However, herbivory was also reduced when pine saplings were completely surrounded by shrubs, since then they served as a mechanical barrier. The type of neighbouring shrub did not affect the overall damage suffered by pines, despite the fact that the ungulates damaged the nonthorny scrubs more intensely than the other kinds of shrubs. Consequently, saplings have an advantage when growing within the canopy of shrubs; these constitute key microsites for pine recruitment in these Mediterranean forests.Key words: associational resistance, associational susceptibility, mammalian herbivory, Mediterranean high mountain, neighbouring effects, Pinus sylvestris var. nevadensis.
Plant community and diversity change due to localized permafrost dynamics in bogs of western Canada
Authors: Beilman David W
Published: April 2011

Localized permafrost formation and melt at the southern limit of permafrost has a large effect on boreal bog plant community structure and diversity in continental western Canada (Alberta, Saskatchewan, and Manitoba). Non-metric multidimensional scaling ordinations show that non-permafrost-affected bogs, areas currently underlain by permafrost (frost mounds), and areas of permafrost degradation (internal lawns) have distinct plant communities. Bryophytes respond more strongly than vascular plants to lengthened environmental gradients in the bogs studied. Seventy-two vascular plant and bryophyte species were found, with mean alpha diversity (species richness) similar in bogs and internal lawns (22.6 and 22.1) and lowest on frost mounds (15.6). Beta diversity (species turnover between landforms) is greater for bryophytes (4.22) than vascular plants (2.54). Comparisons within internal lawns show highly variable height above water table, community composition, and species diversity in wet communities and reduced variability as peat accumulates and converges on dry surfaces dominated by Sphagnum fuscum (Schimp.) Klinggr. Overall, localized permafrost dynamics increase bog plant diversity by 47% by introduction of unique dry, shaded (frost mound) and wet, open (internal lawn) conditions absent from non-permafrost-affected bogs, making localized permafrost bogs one of the most bryologically diverse peatland types in western Canada.Key words: peatlands, bryophytes, plant communities, non-metric multidimensional scaling ordination, permafrost, climate change.
Comparison of the understory vegetation in boreal forest types of southwest Quebec
Authors: Légaré Sonia , Bergeron Yves , Leduc Alain , Paré David
Published: April 2011

Variation in canopy composition can influence ecosystem processes, such as nutrient cycling and light transmittance, even when environmental soil conditions are similar. To determine whether forest cover type influences species composition of the understory vegetation (herbs and shrubs), the composition of this layer was studied on two different surface deposits, clay and till, and under four different forest cover types dominated, respectively, by Populus tremuloïdes Michx. (aspen), Betula papyrifera Marsh. (white birch), Pinus banksiana Lamb. (jack pine), and Picea glauca (Moench) Voss  Abies balsamea (L.) Mill. (sprucefir) over similar environmental conditions. Detrended correspondence analysis and analysis of variance performed on the ordination scores revealed that understory plant composition was highly affected by surface deposit and forest cover. The gradient observed in the correspondence analysis proceeds from aspen, white birch, sprucefir, to jack pine. Indicator species were identified for each surface deposit and cover type, and most of them were associated with either jack pine or aspen. The richness, evenness, and diversity of the understory vegetation did not vary between cover types, but were affected by surface deposit. By controlling ecosystem processes such as light transmittance and nutrient cycling, forest cover influences understory composition.Key words: cover, understory, composition, boreal forest, environmental condition.
Evidence for active CO2 uptake by a CO2-ATPase in the acidophilic green alga Eremosphaera viridis
Authors: Deveau Jason ST , Lew Roger R , Colman Brian
Published: April 2011

We examined the mechanism(s) responsible for active uptake of dissolved inorganic carbon (DIC) during photosynthesis in the green alga Eremosphaera viridis De Bary. O2 electrode measurements of algal oxygen evolution and CO2 fluxes as a function of DIC availability indicate that E. viridis actively imports only CO2 during photosynthesis, and does not possess external carbonic anhydrase (CA). The K0.5[CO2] was 14.2 and 10.1 µM at pH 5.0 and 8.0, respectively. Both membrane potential and cellular resistance were measured under controlled conditions of [CO2] at either 2 or 15 µM. Active CO2 uptake was electrically silent, suggesting that CO2 uptake might be mediated by a CO2-ATPase. Comparison of ATPase activity in microsomal preparations at low (0 µM) and high (15 µM) [CO2] indicated a 1.25-fold increase in ATP hydrolysis in high [CO2]. The CO2-ATPase activity was inhibited by the broad-acting inhibitors diethylstilbestrol (DES) and N',N'-dicyclohexylcarbodiimide (DCCD) but unaffected by vanadate, fluoride, and nitrate. The K0.5[CO2] of the ATPase activity was 22.5 µM, a value very similar to the K0.5[CO2] for CO2 uptake by whole algal cells. These results suggest the existence of a CO2-ATPase as the major importer of DIC for photosynthesis in the microalga E. viridis.Key words: chlorophyte, CO2 transport, CO2-ATPase, photosynthesis, electrical potential, mass spectrometry.
Postglacial history of a marl fen: vegetational stability at Byron-Bergen Swamp, New York
Authors: Futyma Richard P , Miller Norton G
Published: April 2011

Byron-Bergen Swamp, an 800-ha mire complex in western New York, is a mosaic of hardwoodconifer forest, white cedar swamp, and open nonforested fens dominated by sedges, other herbs, and shrubs. The mire is a sloping, spring-fed rich fen in which marl deposition occurs in the open fens but not under forest. Two cores, 120 m apart, one in a marl fen and the other in a hardwoodconifer swamp, were taken to investigate the history of the mire. Sediment, pollen stratigraphy, and 14C chronology show that the Holocene record of local vegetation at each coring site was very different. One site was first a shallow marl pool (10 700  5600 years BP), then an open shrubconifer vegetation, and finally a closed hardwoodconifer swamp. The other site progressed from a pinesprucetamarack swamp (10 700  8000 years BP) to a white cedar swamp (75003500 years BP) and then to a marl sedge fen (3500 years BP  present). The spatial arrangement of swamp forest and marl fen changed through time, responding to marl accumulation and lateral shifts in drainage pathways. Marl deposition occurred continuously at each site, although at different times, for several thousand years. The pattern of vegetation change that we found is not congruent with that predicted from classical hydrarch succession.Key words: marl, mire development, pollen stratigraphy, rich fen.
Lichen chronosequences (postfire and postharvest) in lodgepole pine (Pinus contorta) forests of northern interior British Columbia
Authors: Coxson Darwyn S , Marsh Janet
Published: April 2011

Lichen community development was examined in a postfire chronosequence from lodgepole pine (Pinus contorta Dougl. ex Loud var. latifolia Engelm.) forests in the Omineca region of north-central British Columbia and in stands originating from logging in the early 1980s. Fire-origin stands showed dense regeneration of pine and widespread growth of acrocarpous mosses such as Polytrichum spp. As canopy thinning progressed, Cladonia spp. lichens initiated development at the forest floor surface. By 50100 years after stand origin, Cladina mitis and Cladina rangiferina dominated at the forest floor surface, remaining at high cover values well into the second century of stand development. Late seral stages of stand development (approximately 150+ years) showed increasing basal area and canopy cover of lodgepole pine, with feathermoss mats (e.g., Pleurozium schreberi) replacing terrestrial lichens at the forest floor surface. Stand ordinations confirmed these groupings of species. Stand structural factors that correlate best with lichen mat development include tree density, basal area, and canopy cover. Changes in the leaf area index and associated litterfall loading appear to precipitate the replacement of terrestrial lichen mats in "old-growth" stands. Interestingly, this trend was reversed in mature stands where winter harvesting of trees removed canopy cover without disturbing the forest floor surface. Lichen cover in these sites, 15 years after harvest, exceeded that of comparably aged fire-origin stands. Summer harvesting (with a presumed greater disturbance of soils) did not trigger a similar rebound of lichen communities. Instead, vascular plants appeared to invade these sites, following a seral sequence different from that occurring in fire-origin stands.Key words: terrestrial lichens, pine woodlands, caribou habitat.
Penetration and infection of Sclerotinia sclerotiorum by Coniothyrium minitans
Authors: Huang H. C. , Hoes J. A.
Published: April 2011

Coniothyrium minitans is a destructive parasite of Sclerotinia sclerotiorum that kills hyphae and sclerotia. Hyphal tips of the parasite penetrate cell walls of the host without the formation of specialized structures. Host cytoplasm disintegrates and cell walls collapse as a result of infection. Microconidia and intrahyphal hyphae were produced by S. sclerotiorum in infected colonies.