bluuebunny/crossref_metadata_2025 huggingface dataset:
On the phylogeny of Ophiostoma, Ceratocystis s.s., and Microascus, and relationships within Ophiostoma based on partial ribosomal DNA sequences
Authors: Hausner G. , Reid J. , Klassen G. R.
Published: April 2011

Phylogenetic analysis of partial rDNA sequences suggests that Ophiostoma should remain the sole genus of the Ophiostomataceae, and this should be the sole family within the Ophiostomatales, whereas Ceratocystis s.s. would be best disposed within the Microascales. Although morphological criteria suggest that the genus Ophiostoma is heterogeneous, analysis of partial small subunit rDNA sequence data shows that Ophiostoma (excluding O. roraimense) represents a monophyletic taxon. Analysis of a partial large subunit rDNA data set, which included sequences from 55 species assignable to Ophiostoma, failed to support the strict subdivision of the genus based on either ascospore characters or the nature of the anamorph. Key words: Ceratocystis, Microascus, Ophiostoma, partial rDNA sequences, phylogeny.
Cortical responses in Japanese black pine to attack by the pine wood nematode
Authors: Ishida Kyoko , Hogetsu Taizo , Fukuda Kenji , Suzuki Kazuo
Published: April 2011

Anatomical and cytochemical changes in the current-year stem cuttings of Japanese black pine (Pinus thunbergii) were investigated in the early stage of infection by a virulent isolate and an avirulent isolate of pine-wood nematode (Bursaphelenchus xylophilus), and an avirulent isolate of another nematode species, Bursaphelenchus mucronatus. Accumulation of lignin- and suberin-like substances around the resin canals in the cortex was shown as a new symptom of the infection by these isolates. Experiments with girdled cuttings demonstrated that more nematodes inhabit and move in the bark than in the xylem and pith at the early stage of infection by the virulent isolate. Death of pine cells occurred first in the epithelial cells of resin canals in the cortex after inoculation with the virulent isolate and then in the cortex and periderm, pith and xylem, and finally the cambium. In branches of 5-year-old seedlings inoculated with avirulent and B. mucronatus isolates, wound periderm was formed surrounding resin canals in the cortex, and cortical cells surrounding the wound periderm were alive. Evidence indicates that nematodes first enter resin canals in the cortex and then invade the surrounding cortical tissue, and that the ability of the virulent nematodes to move into the cortical tissue may be greater than that of the other isolates, accounting for differences in virulence. Key words: Bursaphelenchus xylophilus, Bursaphelenchus mucronatus, virulence, periderm, pine wilt disease, pine-wood nematode.
Microprojectile-mediated DNA delivery to the Salicaceae family
Authors: Devantier Yvonne A. , Moffatt Barbara , Jones Catherine , Charest Pierre J.
Published: April 2011

A transient gene expression system was developed for the Salicaceae family using microprojectile-mediated DNA delivery (Biolistic™) to cell suspensions. Using Populus nigra × Populus maximowiczii line NM1, 10 variables were optimized. Optimum transient gene expression under the 10 conditions tested was obtained with a 7- to 9-day-old cell suspension. Highest transient levels were observed with samples positioned 13.5 cm from the stopping plate and bombarded with 1.6-μm gold particles coated with 1 μg of DNA precipitated with CaCl2. Assaying for β-glucuronidase gene expression was performed 1 day after bombardment. The fate of the microparticles in the bombarded cells was studied, showing that 58.9% of cells expressing the β-glucuronidase gene had microparticles located in the nucleus or its vicinity and the remaining cells had microparticles in the cytoplasm. Cell suspensions from five different lines (P. nigra × P. maximowiczii lines NM1 and NM6, Populus deltoides × P. nigra line DN106, Populus tremula × Populus alba line 7171-B4, and Salix alba sanguined line SA-2) yielded transient gene expression. The relative strengths of β-glucuronidase expression in the lines tested were NM1 = 7171-B4 > NM6 > DN106 > SA-2. Six plasmid constructions were also tested in line NM1 for transient β-glucuronidase gene expression. The x-glucuronide histochemical assay did not reveal any differences, but the methyl umbelliferone glucuronide fluorescent assay yielded the following relative levels of transient gene expression with the different promoter sequences: 35S-35S-AMV enhancer = 35S-AMV enhancer > 35S-35S = 35S-35S-AMV enhancer with the β-glucuronidase – neomycin phosphotransferase fusion > 35S. Four transgenic cell lines of P. nigra × P. maximowiczii were characterized for kanamycin resistance and neomycin phosphotransferase II gene activity. Polymerase chain reaction and Southern hybridization analyses indicated the presence of the β-glucuronidase and neomycin phosphotransferase II genes in the genome of three of these transgenic lines. Key words: microprojectile, particle bombardment, Salicaceae, poplar, willow.
Phaeotheca dimorphospora increases Trichoderma harzianum density in soil and suppresses red pine damping-off caused by Cylindrocladium scoparium
Authors: Yang D. , Bernier L. , Dessureault M.
Published: April 2011

A fungal antagonist, Phaeotheca dimorphospora, was tested for its ability to control damping-off of red pine (Pinus resinosa) caused by Cylindrocladium scoparium. In vitro, the germination of seeds coated with P. dimorphospora microconidia was significantly increased by 10% compared with uncoated seeds. In experiments carried out in Petri dishes, addition of P. dimorphospora into soil significantly reduced the population of C. scoparium and disease incidence. In the greenhouse, application of P. dimorphospora into the top layer of soil reduced pre- and post-emergence damping-off by 79.5%. Under greenhouse conditions, P. dimorphospora stimulated the population of Trichoderma harzianum, a well-known antagonist of soil-borne plant pathogens. In soil treated with P. dimorphospora, the number of propagules of T. harzianum was 100–500 times higher than in the untreated control, whereas the population of C. scoparium decreased rapidly and was not detectable 1 month after sowing. Key words: Phaeotheca dimorphospora, Trichoderma harzianum, Cylindrocladium scoparium, damping-off, biological control, fungal antagonist, Pinus resinosa.
Diurnal and seasonal variations in gas exchange and water relations of lowland and upland black spruce ecotypes
Authors: Abidine Abdenbi Zine El , Stewart James D. , Plamondon André P. , Bernier Pierre Y.
Published: April 2011

Gas exchange and water relations were measured on seedlings from two pairs of upland and lowland black spruce (Picea mariana (Mill.) BSP) populations. The seedlings were planted under natural atmospheric conditions in exterior sand beds. Measurements were carried out on eight separate days during the summer of 1992. Diurnal and seasonal responses of gas exchange and water relations parameters to natural changes in environmental factors were analyzed for possible ecotypic differences. Differences were found among the four populations and within one of the two upland–lowland pairs. However, no differences could be linked significantly to an upland–lowland ecotypic differentiation. The physiological responses are discussed with respect to diurnal and seasonal changes in environmental factors and to similarities with results from an earlier experiment involving mature trees from the same four populations. Key words: Picea mariana, water stress, net photosynthesis, stomatal conductance.
Nutrient limitations in the northern pitcher plant Sarracenia purpurea
Authors: Chapin Carmen T. , Pastor John
Published: April 2011

The idea that carnivorous plants capture insects to supply limiting nutrients is often conjectured but rarely tested with fertilization trials or the construction of nutrient budgets. Accordingly, Sarracenia purpurea plants were analyzed for nitrogen and phosphorus after a 4-month fertilization of the pitchers with nitrogen, phosphorus, micronutrients, combinations thereof, and insect material. Neither the number of leaves produced in the same season nor average leaf mass differed significantly between treatments. Nitrogen and phosphorus concentrations were significantly higher in those leaves that received the respective treatments. Plots of concentration versus content indicated that plants were nitrogen and phosphorus limited. A nutrient budget for nitrogen was determined by soil mineralization, insect removal from the pitchers, and rainwater analysis. This budget showed that nitrogen in captured insects is one-tenth the annual plant requirement. However, soil N mineralization is sometimes more than adequate to supply demands were it to be exploited. Key words: carnivory, Sarracenia purpurea, nutrient limitation.
Fungi-vegetation relationships in aPinus sylvestrisforest in central Norway
Authors: Såstad Sigurd M.
Published: April 2011

The macrofungal Basidiomycete community of a Pinus sylvestris forest was investigated in 50 plots, 2 × 2 m, to see how vegetation composition and space influenced the distribution of saprotrophic and ectomycorrhizal fungi. Mantel tests and partial Mantel tests revealed a relationship between total cover of the field layer and mycorrhizal fungi, and total cover of the bottom layer and saprotrophic fungi. These results are consistent with the predictions that mycorrhizal fungi are mainly influenced by plant species present in the root zone, whereas saprotrophic fungi are mainly influenced by the plant species of the bottom layer. Variation in the abundance of tree species did not influence the distribution of macrofungal species at this scale. The spatial patterns of fungal distribution found in this study did not deviate significantly from a random distribution. Indirect ordination showed that the ectomycorrhizal fungi mainly responded to a gradient in cover of the field layer, whereas the saprotrophs seemed to respond to a complex gradient of cover of field and bottom layer, moisture, and paludification. A direct ordination using both vegetation and fungi descriptors indicated that some of the covariation in the saprotrophic fungi and the bottom layer might be coordinated responses to changes in the field layer. A considerably higher β diversity was found among the fungi than in the vegetation. Key words: basidiomycetes, saprotrophic fungi, mycorrhizal fungi, fungi–vegetation relationships, Mantel test, ordination.
Elemental composition of globoids in the perisperm tissue of various seeds
Authors: West M. Marcia , Flannigan Derrick T. , Lott John N.A.
Published: April 2011

The mature seeds of some angiosperms contain perisperm tissue derived from remains of the nucellus tissue of the ovule. In our transmission electron microscopy studies, the perisperm tissues of the seeds of Yucca brevifolia, Coffea arabica, Beta vulgaris, Piper nigrum, and Zostera capricorni contained naturally electron-dense globoids. Energy dispersive X-ray analysis of globoids from the perisperm tissues of these seeds revealed varying levels of phosphorus, potassium, magnesium, and calcium, results that are consistent with the presence of the mineral nutrient store called phytate. Phosphorus, potassium, magnesium, calcium, and other mineral nutrients, likely stored as phytate, have routinely been located in globoids of endosperm, female gametophyte, and embryo tissues of seeds. Key words: perisperm, globoids, mineral nutrient reserves, phosphorus, seeds, energy dispersive X-ray analysis.
Long-distance wind dispersal of tree seeds
Authors: Greene D. F. , Johnson E. A.
Published: April 2011

Long-distance seed dispersal figures prominently in most plant conservation biology arguments, yet we possess little more than anecdotes concerning the relationship among deposition (seeds/m2), source strength (seeds/m2), and distance. In this paper we derive two simple models for long-distance deposition. The models are tested at the scale of 100–1600 m from the source and found to be within 5-fold of the observed deposition. There is no discernable decline in deposition for the range 300–1600 m. While we hesitate to extend model predictions to greater distances, both the models and the empirical results allow us to assert that rare wind-dispersed species in woodlots (dispersal distance around 1 km) are effectively isolated from one another at the temporal scale of 1000 years. Key words: plant conservation biology, wind dispersal of seeds, metapopulations.
Dissemination of the mycoparasite Scytalidium uredinicola by Epuraea obliquus (Coleoptera : Nitidulidae)
Authors: Currie Cameron R.
Published: April 2011

This study aims to identify the role of the beetle Epuraea obliquus Hatch in disseminating Scytalidium uredinicola Kuhlman et al., a mycoparasite of western gall rust, Endocronartium harknessii (J.P. Moore) Y. Hiratsuka. The study was conducted in a lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm., stand near Hinton, Alberta. Mycoparasite spores were observed on the integument of adult beetles collected from western gall rust. In field and greenhouse experiments, adult beetles inoculated with spores of the mycoparasite caused significant numbers of S. uredinicola infections on western gall rust. Since E. obliquus adults migrate between galls, the beetle can transfer the mycoparasite from parasitized to unparasitized galls. Scanning electron microscopy showed that spores of the mycoparasite were common on the body of overwintering beetles. It is believed that these overwintering spores are viable because a culture was successfully established from them. This suggests that beetles emerging in the spring can disseminate S. uredinicola to previously uninfected galls. Epuraea obliquus is an important insect vector of S. uredinicola in western Canada. Key words: mycoparasite, vector, spore dispersal, western gall rust, pine stem rusts.
Powellomyces, a new genus in the Spizellomycetales
Authors: Longcore Joyce E. , Barr Donald J. S. , Désaulniers Nicole
Published: April 2011

Powellomyces (order Spizellomycetales) is erected for soil-inhabiting chytrids previously classified in Entophlyctis. Fischer's narrative and figures indicate that Entophlyctis was originally described to accommodate aquatic, chytridialean species, and consequently this is not an appropriate genus for spizellomycetalean species. Powellomyces hirtus sp.nov. and Powellomyces variabilis nom.nov. both develop exogenously but differ in distribution of rhizoids on germlings and in colour of colonies in culture. Key words: Chytridiales, Entophlyctis, Powellomyces, Spizellomycetales.
The in vitro effect of allelopathy and various fungi on marsh reed grass (Calamagrostis canadensis)
Authors: Winder Richard S.
Published: April 2011

Allelopathy and endophytic fungi were evaluated as factors affecting the biological control of marsh reed grass, Calamagrostis canadensis (Michx.) Beauv., a weed of boreal reforestation areas. Leachate from marsh reed grass straw inhibited root growth into liquid and agar media and increased foliar necrosis. Most seedlings harboring endophytic species of Fusarium and Chaetomium were healthy in agar controls, but all such seedlings were diseased when grown in agar with straw leachate. The straw leachate and various fungi had distinct impacts on the virulence of Colletotrichum sp., a potential biocontrol agent for marsh reed grass. In comparisons of control and allelopathic media, Colletotrichum sp. stimulated the overall vigor of reed grass while reducing vigor in the allelopathic medium. Individual isolates of fungi in the genera Epicoccum, Drechslera, and Fusarium were uniformly antagonistic to Colletotrichum, whereas antagonism in individual isolates of Chaetomium, Alternaria, and Stemphylium depended on the presence or absence of allelopathy. Another Fusarium isolate increased the virulence of Colletotrichum sp. in both media, as did two applications of Colletotrichum sp. Allelopathic compounds, Fusarium sp., and Colletotrichum sp. are potential components of a strategy for biological control of marsh reed grass. Key words: weed, biological control, bioherbicide, mycoherbicide.
Effects of ultraviolet on polyphenolics of Umbilicaria americana
Authors: Swanson Andrew , Fahselt Dianne
Published: April 2011

The foliose lichen Umbilicaria americana Poelt & Nash was exposed to spectrally altered radiation in three growth chamber experiments and one field experiment. After 1 week in growth chambers the phenolic content (% w/w) increased significantly under a spectral band including visible light and UV-A, and the increase was greater when intensity was higher. Under exposure to both UV-A and UV-B the concentration of phenolics was lower than with UV-A alone and, depending on dosage, approached or achieved control levels. In a population of U. americana on a vertical rock face, the interaction between filter treatments and collection dates had a highly significant effect on phenolic levels (P = 0.01). In thalli protected from UV-B, phenolic levels were higher than in those exposed to natural sunlight in June and October, but the same response was not observed in July and August. Thallus groupings covered by filters that admitted both UV-B and UV-A accumulated less phenolics than controls in August, but on other sampling dates contained the same concentrations. Key words: Umbilicaria americana, UV-A, UV-B, depsides, tridepsides.
HCO3−efflux and the regulation of the intracellular Cipool size inSynechococcusUTEX 625
Authors: Salon Christophe , Canvin David Thomas
Published: April 2011

Cyanobacterial cells of Synechococcus UTEX 625 were suspended in increasing extracellular inorganic carbon (Ci, up to 1 mM) under steady state photosynthesis conditions in a cuvette connected to a mass spectrometer. Photosynthetic CO2fixation, net CO2, and net HCO3−transport increased with increased extracellular Ciup to 100 μM [C1], with HCO3−transport contributing the most to the maintenance of the internal Cipool. When the extracellular [Ci] was increased above 100 μM, CO2, fixation and net CO2transport increased toward their maximum rates but net HCO3−transport progressively declined. At an extracellular [Ci] of 1 mM, the net HCO3−transport rate was only 15% of its value at 100 μM extracellular [Ci]. Under steady state photosynthesis conditions, the gross HCO3−transport rate remained at its maximum value at extracellular [Ci] above 100 μM either when CO2transport was precluded (i.e., in the presence of 200 μM Na2S) or when HCO3−transport was measured with H14CO3−and silicone oil filtration. As HCO3−efflux, calculated using the permeability coefficient determined at low [Ci], could not account fully for the decrease of the net HCO3−transport rate, Ciefflux and CO2, efflux were measured at high extracellular [Ci] during the initial period of darkness. With increasing intracellular [Ci] Ciefflux over intracellular [Ci] increased linearly but CO2, efflux over intracellular [Ci] was constant, hence the HCO3−efflux obtained by the difference between the Ciand the CO2efflux increased hyperbolically. Using HCO3−and CO2, efflux, we calculated that the permeability coefficient of the cell envelope for HCO3−but not for CO2increased with increasing intracellular [Ci]. When the HCO3−efflux was measured under steady state Ciflux conditions in the light, the permeability coefficient of the cell envelope for HCO3−also increased with increasing intracellular [Ci]. Reasons for the change in whole cell permeability to HCO3−at high extracellular [Ci] are discussed. Key words: Synechococcus UTEX 625, blue green algae, cyanobacteria, active HCO3−transport, HCO3−leakage, Ciconcentrating mechanism.
Cold-shock-stimulated γ-aminobutyric acid synthesis is mediated by an increase in cytosolic Ca2+, not by an increase in cytosolic H+
Authors: Cholewa Ewa , Bown Alan W. , Cholewinski Andrzej J. , Shelp Barry J. , Snedden Wayne A.
Published: April 2011

Synthesis of the nonprotein amino acid γ-aminobutyric acid is stimulated within minutes by diverse environmental factors. Synthesis (L-Glu + H+– γ-aminobutyric acid + CO2) is catalysed by L-Glu decarboxylase, a cytosolic enzyme having an acidic pH optimum. This study uses isolated Asparagus sprengeri (Regel) mesophyll cells to investigate the possible role of Ca2+in stimulated γ-aminobutyric acid synthesis. Abrupt cold shock (20 °C to 1 °C) stimulated γ-aminobutyric acid levels from 2.7 to 5.6 nmol/106cells within 15 min. This 100% increase was reduced to 28% in the presence of the Ca2+channel blocker lanthanum, and was significantly reduced by incubation with 1 mM of the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide. Incubation at 20 °C with 25 μM calcimycin, a Ca2+ionophore, increased levels by 61% within 15 min. A fluorescent Ca2+indicator demonstrated that cytosolic Ca2+increased within 2 s of cold shock, followed by a return to initial levels within 25 s. In contrast, comparable experiments indicate a rapid and prolonged decrease in cytosolic H+. L-Glu decarboxylase isolated from asparagus cladophylls was stimulated 100% by addition of 500 μM Ca2+and 200 nM calmodulin. This activity was reduced to control values by the calmodulin antagonist. Collectively, the data indicate that cold shock initiates a signal transduction pathway in which increased cytosolic Ca2+stimulates calmodulin-dependent L-Glu decarboxylase activity and γ-aminobutyric acid synthesis. This mechanism appears independent of increased H+. Key words: cold shock, GABA, Ca2+, H+.
Late-glacial – early Holocene vegetation, climate, and fire at Sutherland Pond, Hudson Highlands, southeastern New York, U.S.A.
Authors: Maenza-Gmelch Terryanne E.
Published: April 2011

Accelerator mass spectrometry dated pollen, plant-macrofossil, and charcoal records from Sutherland Pond (41°23′29″N, 74°02′16″W), located in the Black Rock Forest, provide a detailed account of forest history during the late-glacial – Holocene transition in the Hudson Highlands, lower Hudson Valley, southeastern New York. Pollen assemblages dating more than 12 600 radiocarbon years before present (years BP) are dominated by herbaceous and shrub types (Salix, Betula, Alnus, Ericaceae, Cyperaceae, Gramineae, and Tubuliflorae), with some arboreal types (Pinus and Picea), apparently representing an open landscape possibly with scattered trees. At 12 600 years BP increased organic deposition and pollen influx and the first occurrence of macrofossils indicate dramatic environmental change. Mixed assemblages of boreal and temperate taxa (Picea, Abies, Betula papyrifera, Quercus, Ostrya – Carpinus, and Fraxinus) are evident from 12 600 to 11 200 years BP. Low charcoal influx suggests that fire was a minor component of early woodland development beginning around 12 600 years BP. A Picea–Abies–Alnus assemblage, suggesting a cool climatic episode, dominates between 11 200 and 10 120 years BP, with rapid onset and termination each occurring within 150 years. Fire activity is also low during this colder interval. Warmer conditions, reestablished by 10 120 years BP, are inferred from expansion of Pinus strobus and increasing Quercus and Ostrya–Carpinus, followed by replacement of B. papyrifera by Betula populifolia and increased charcoal influx. Key words: late glacial, pollen, plant macrofossils, fire, accelerator mass spectrometry radiocarbon dating, New York.
Host and geographical distribution of Verticicladium trifidum, Thysanophora penicillioides, and similar fungi on decaying coniferous needles
Authors: Maanen A. van , Gourbière F.
Published: April 2011

Dematious hyphomycetes such as Verticicladium trifidum and Thysanophora penicillioides are examples of equivalent species occupying the same ecological niche in different fungal successions. These two species fructify through the stomata of coniferous needles a few months after litter fall. Litter samples of 23 coniferous species from different European sites were examined to explain the fungal distribution. Thysanophora penicillioides colonized Abies, Picea, Pseudotsuga, and Tsuga needles, whereas V. trifidum was restricted to Pinus and Cedrus. Sometimes other fungal species occupied the stomata: on Pinus pinea needles, the niche was occupied by Cladosporium spp. and Alternaria alternata; Chaetopsina fulva have been found only on Pseudotsuga needles and Thysanophora canadensis on Picea. Verticicladium trifidum was apparently absent on Pinus litters from cold climates (high altitude or latitude) and probably from warm mediterranean regions, suggesting a climatic determinism. However, coexistence of Verticicladium and Thysanophora in some samples or colonization of some Pinus litter by Thysanophora suggests that these distributions result from competition rather than strict host specificity. Key words: ecological niche, equivalent species, conifers, needles, Verticicladium trifidum, Thysanophora penicillioides.
Electron microscopy of two nematode-destroying fungi, Meristacrum asterospermum and Zygnemomyces echinulatus (Meristacraceae, Entomophthorales)
Authors: Saikawa Masatoshi , Oguchi Masami , Ruiz Rafael F. Castañeda
Published: April 2011

Infection of nematodes by Meristacrum asterospermum and Zygnemomyces echinulatus was initiated by conidia adhering to the nematode's cuticle. Each conidium developed an infection peg to penetrate the nematode after adhesion. In M. asterospermum, an infection peg just under the penetration was found in ultrathin sections, in which the peg's cell wall was broken into several lobes that were covered entirely with an amorphous mass of electron-opaque substance. Septa formed in the apical portion of aerial conidiophore under conidiation. The septal wall was nonperforate and often contained electron-opaque inclusions. Vegetative hyphae of Z. echinulatus had typical bifurcate septa, but septa at both ends of the pedicel of conidia were often slightly deformed. Key words: infection of nematodes, Meristacrum asterospermum, septum, Zygnemomyces echinulatus.
Development and ultrastructure of the endodermis in the primary root of cork oak (Quercus suber)
Authors: Verdaguer Dolors , Molinas Marisa
Published: April 2011

The endodermis maturation process was studied in the primary root of the cork oak (Quercus suber L.) with emphasis on the chemical nature of the cell wall and on the possible role of tannins. Tannins were found in endodermal and adjacent cortical cells in all maturation stages. We discuss our findings in relation to the previous literature in other woody and herbaceous species. The results of the histochemical tests showed differences in the aliphatic compounds of the suberin between the Casparian strip suberin and the suberin layer deposited in state II cells. Plasmodesmata were present in radial and tangential walls during the entire maturation process. The significance of plasmodesmata and of the suberin deposition pattern is discussed in relation to apoplastic and symplastic transport in roots. Key words: Casparian strip, endodermis, primary root, suberin, Quercus suber L.
Pollen analysis and ordination of lake sediment-surface samples from coastal British Columbia, Canada
Authors: Pellatt Marlow G. , Mathewes Rolf W. , Walker Ian R.
Published: April 2011

Surficial sediment samples from 42 lakes, distributed from sea level to alpine elevations of coastal British Columbia and northwest Washington, were analyzed for pollen and spores. Pollen analysis revealed characteristic differences among the assemblages of the Coastal Western Hemlock, Mountain Hemlock, and Engelmann Spruce – Subalpine Fir biogeoclimatic zones (the Alpine zone is less clearly identifiable). Cluster analysis and detrended correspondence analysis (DCA) correctly group the sites according to their biogeoclimatic zones and also by geographic origin. DCA indicates a high correlation between the biogeoclimatic zones of the sample sites and annual precipitation (−0.89), January temperature (−0.77), annual temperature (−0.64), and growing-season precipitation (−0.68). Further analysis of the samples and eight environmental gradients using canonical correspondence analysis groups the pollen assemblages from the study sites into biogeoclimatic zones in relation to annual precipitation, growing-season precipitation, annual snowfall, annual temperature, and growing degree-days. These data are useful for testing whether or not postglacial pollen assemblages have modern analogues. Key words: modern pollen analysis, vegetation, ordination, multivariate statistical analysis, biogeoclimatic zones, British Columbia.
Membrane deterioration during senescence
Authors: Thompson J. E. , Froese C. D. , Hong Y. , Hudak K. A. , Smith M. D.
Published: April 2011

The lipid bilayers of plant membranes are normally liquid crystalline, reflecting the inherent rotational motion of membrane fatty acids at physiological temperature. With the onset of senescence, the chemical composition of membrane lipids changes resulting in lipid phase separations within the bilayer. These phase changes render the membranes leaky and lead to loss of essential ion gradients and impairment of cell function. The separation of lipid phases appears to be attributable to an accumulation of lipid metabolites in the bilayer that are formed during turnover and metabolism of membrane lipids. These metabolites are normally released from membranes as lipid–protein particles found in the cell cytosol and within organelles. The lipid–protein particles also contain catabolites of membrane proteins and appear to serve as a vehicle for removing lipid and protein metabolites that would otherwise destabilize the bilayer. They bear structural resemblance to oil bodies, which are abundant in oil seeds, and have been found in leaves, cotyledons, and petals as well as in insect and animal tissue. The accumulation of lipid metabolites in senescing membranes and ensuing separation of lipid phases appear to reflect impairment of lipid–protein particle release from membranes as tissues age and to be a seminal cause of membrane dysfunction with advancing senescence. Key words: lipid bilayer, lipid phase separation, lipid–protein particles, membrane, oil body, senescence.
On the allelopathic potential of certain terpenoids, phenolics, and their mixtures, and their recovery from soil
Authors: Inderjit  , Muramatsu Michiyasu , Nishimura Hiroyuki
Published: April 2011

A study was conducted to understand the effects of certain phenolics, terpenoids, and their equimolar mixture through agar gel and soil growth bioassays and their recovery from soils. The eight compounds selected for this study were p-hydroxybenzoic acid, ferulic acid, umbelliferone, catechin, emodin, 1,8-cineole, carvone, and betulin. Lettuce (Lactuca sativa L.) was used as test species for agar gel and soil growth bioassays. Root and shoot growth of lettuce was inhibited for all the above except emodin and catechin. However, in soils treated with different phenolics and terpenoids, only root growth of lettuce was inhibited, whereas shoot growth was promoted. Recovery of p-hydroxybenzoic acid and umbelliferone was higher in unautoclaved soils, while that of catechin was lower. Recovery in relation to degradation of compounds and the significance of additive activities of compounds are discussed. Key words: phenolics, allelopathy, terpenoids, soil, Lactuca sativa.
Experimental study of gene flow between wild and cultivated Pennisetum glaucum
Authors: Renno J. -F. , Winkel T. , Bonnefous F. , Bezançon G.
Published: April 2011

Under natural conditions, wild and cultivated pearl millet, Pennisetum glaucum (L.) R.Br., exchanged genes for millenia and, nevertheless, maintain high morphological differentiation. Under experimental conditions in the Sahel, hybridization between wild and cultivated pearl millet was measured using isozymic markers and interpreted in relation to the phenology of the plants. Gene flows were asymmetric, engendering 8% of hybrids in the progeny of the wild phenotype, 45% in that of the cultivated phenotype, and 39% in that of the intermediate "shibra" phenotype; these last two phenotypes constitute the sample of cultivated pearl millet. The proportion of hybrids in the progeny of the wild sample was time dependent during the flowering phase of cultivated pearl millet. The proportion of hybrids produced by the cultivated pearl millet was not time dependent. In the seeds produced by the cultivated phenotype along its reproductive phase, the proportion of viable seeds was negatively correlated with the frequency of hybrids. Likewise, the speed of germination of seeds produced by the cultivated or the shibra phenotypes was negatively correlated with the frequency of the hybrids that they contained. The effects of balancing among genetic intermixing, isolation and reproduction barriers, and differential anthropic and natural selection pressures are discussed to better understand the evolution and the maintenance of the polymorphism of Pennisetum glaucum. Key words: pearl millet, wild pearl millet, Pennisetum glaucum, gene flow, domestication, hybrid.
Effect of the intracellular inorganic carbon pool on chlorophyll a fluorescence quenching and O2photoreduction in air-grown cells of the cyanobacteriumSynechococcusUTEX 625
Authors: Li Qinglin , Canvin David Thomas
Published: April 2011

Simultaneous measurements were made of O2exchange, inorganic carbon (Ci) accumulation and assimilation, and chlorophyll a fluorescence of the cyanobacterium Synechococcus UTEX 625. The addition of Cito cells at the CO2compensation point resulted in quenching of chlorophyll a fluorescence in the presence or absence of the CO2fixation inhibitor, iodoacetamide. The magnitude of quenching was related to electron flow to terminal electron acceptors such as CO2and O2. When photosynthetic CO2fixation was allowed, the rate of electron transport, as expressed by (F*m– F)/F*m, was highly correlated with the onset of photosynthesis. When CO2fixation was inhibited by the addition of iodoacetamide, the observed fluorescence quenching was consistent with the enhanced rate of O2photoreduction that occurred when Ciwas added. There was a close correlation (r = 0.98) between the magnitude of O2-dependent fluorescence quenching and the amount of O2photoreduction. The degree of stimulation of electron flow to O2photoreduction was dependent on the inorganic carbon concentration. The K1/2(Ci) for extracellular Ciwas 1.36 ± 0.13 μM (mean ± SD, n = 3) and K1/2(Ci) for the intracellular Cipool was 1.4 ± 0.18 mM (mean ± SD, n = 3). The reduction of N,N-dimethyl-p-nitrosoaniline was also stimulated by the addition of Ci, whereas the addition of Cihad no effect on the reduction of 2,6-dimethylbenzoquinone and ferricyanide. The results suggest that Cistimulates electron flow in photosystem I. Key words: cyanobacteria, O2photoreduction, fluorescence, Ciconcentrating mechanism, inorganic carbon pool, linear electron transport, kinetic study.
Mating system of Calluna vulgaris: self-sterility and outcrossing estimations
Authors: Mahy Grégory , Jacquemart Anne-Laure
Published: April 2011

The evolutionary significance of a mixed mating system is currently under debate. Calluna vulgaris (L). Hull, a widespread European shrub, is likely to undergo mixed mating because of geitonogamy. Mating system was investigated in three populations of C. vulgaris by means of greenhouse controlled crosses, pollen tube observations, and outcrossing rate estimations from allozyme markers. The species is highly self-sterile, most probably as a result of early inbreeding depression. Mean fruit set and mean seed number per fruit following hand self-pollination were 48 and 13%, respectively, of those following cross-pollination. Pollen tubes produced by self pollen penetrated the ovary with the same success as those from cross-pollination. Multilocus estimates of the outcrossing rates ranged from 0.71 to 0.90, and two estimates were significantly different from 1.00. Calluna vulgaris could thus be classified as being mixed mating with predominant allogamy. Single-locus estimates did not differ significantly from multilocus estimates suggesting that biparental inbreeding did not contribute to the apparent selfing rate. The maintenance of high early inbreeding depression despite an intermediate level of selfing is discussed with respect to recent theories on mating system evolution. Key words: Calluna vulgaris, mating system, self-sterility, pollen tubes, outcrossing rate, inbreeding depression.
Frost tolerance and hardening capacity during the germination and early developmental stages of four white spruce (Picea glauca) provenances
Authors: Coursolle C , Bigras F J , Margolis H A
Published: April 2011

Frost tolerance during the germination stages of four white spruce (Picea glauca (Moench) Voss) provenances (between 45°37' and 50°17'N) was studied at four different developmental stages (imbibed seed, radicle, cotyledon, and young seedling), and their hardening capacity was determined for the latter three stages. Hardening capacity was examined by submitting radicle-stage germinants to two temperature-photoperiod treatments (20:15°C - 16-h photoperiod or 5:5°C - 8 h) for 14 days and by submitting cotyledon and young seedling stage germinants to four treatments (20:15°C - 16 h; 20:15°C - 8 h; 5:5°C - 16 h; 5:5°C - 8 h). Frost tolerance was determined immediately after these treatments. Latitude of origin showed no clear pattern with respect to either frost tolerance or hardening capacity at any of the developmental stages. Imbibed seeds had the greatest degree of frost tolerance. With the exception of the most northern provenance, radicle-stage germinants did not respond to a 5:5°C day:night temperature and 8-h photoperiod hardening treatment. A low-temperature treatment of 5:5°C increased the frost tolerance of cotyledon and young seedling stage germinants, while their response to a shortened photoperiod (8 h) was quite variable. However, an 8-h photoperiod did enhance the effect of the low-temperature treatment at the young-seedling stage. Thus, the timing of germination in the field appears to be an important factor in the ability of germinants to tolerate freezing stress.Key words: germination stage, frost tolerance, hardening capacity, photoperiod, temperature.
Ectomycorrhizas of regenerating stands of lodgepole pine (Pinus contorta)
Authors: Bradbury S M , Danielson R M , Visser S
Published: April 2011

The ectomycorrhizal community associated with regenerating lodgepole pine (Pinus contorta Loud.) after clear-cutting in southwestern Alberta was investigated in 6-, 10-, and 19-year-old cut blocks and their adjacent 90-year-old undisturbed control stands. Twenty different mycorrhizal taxa were found in the 90-year-old undisturbed stands. Of these 20, 13 mycorrhizal taxa were found in the 6-year-old cut blocks, and 15 mycorrhizal taxa were found in both the 10- and 19-year-old cut blocks. The most common associate of all stand ages was Mycelium radicis atrovirens Melin (MRA), which overall colonized 29% (weighted average) of the root tips. Species or groups accounting for greater than 10% of the mycorrhizas in one or more age classes included Piloderma fallax (Karst.) Jül. (15% overall), Piloderma byssinum (Karst.) Jül. (11%), Cenococcum geophilum L. (8%), Russula-like (8%), Suillus brevipes (Pk.) Kuntze (5%), Suillus tomentosus (Kauff.) Sing., Snell & Dick (5%), and Lactarius deliciosus (L.:Fr.) S.F. Gray (2%). Although several mycorrhizal fungi exhibited significant differences in percent relative abundance of root tips colonized, when comparing cut blocks to their controls, there was no evidence to suggest that the suite of mycorrhizal fungi colonizing roots of young lodgepole pine trees was replaced by a different suite of mycorrhizal fungi in mature stands. Extensive fruit body collections, totalling 43 species of ectomycorrhizal fungi, throughout the study sites support this contention.Key words: Pinus contorta ectomycorrhizas, clear-cutting, second-rotation forests, succession.
Distribution of herbs and shrubs in relation to landform and canopy cover in riparian forests of coastal Oregon
Authors: Pabst Robert J , Spies Thomas A
Published: April 2011

In this study we characterized the distribution of herb and shrub species relative to landform and forest canopy attributes of streamside forests in the moist, conifer-dominated mountains of coastal Oregon. Species cover and environmental data were collected along transects at 94 sites. Species with relatively similar distributions were classified into 10 species groups to identify major patterns in the vegetation. Although these patterns were highly variable, ordination and gradient analyses indicated that vegetation composition is ordered along a complex environmental gradient running from streamside to hillslope. Similarly, species diversity followed a decreasing trend from active fluvial surfaces to lower hillslopes. Vegetation patterns were related to specific landforms, topographic positions, microsites, and coniferous tree cover within the trans-riparian gradient. We hypothesize that the environmental features correlated with these patterns are surrogates for the underlying mechanisms responsible for them. These are (i) hillslope processes and associated moisture gradients; (ii) hydrological disturbance; (iii) tolerance of saturated, valley-floor soils; (iv) shade tolerance; and (v) mineral soil disturbance. This study indicates that valley-floor and lower-slope plant communities are distinct elements in these forest landscapes, supporting the assumption that riparian zones require a different management and conservation strategy than upland forest communities.Key words: riparian vegetation, ordination, gradient analysis, species groups, landform. Nomenclature is based on that of Hitchcock and Cronquist (1973).
Genetic resemblance of allotetraploid Aster ascendens to its diploid progenitors Aster falcatus and Aster occidentalis
Authors: Allen Geraldine A , Eccleston Cindy L
Published: April 2011

Polyploidy is an important process in the evolution of the flowering plants. We used isozyme electrophoresis to examine genetic variation in populations of the western North American Aster ascendens Lindl., a dibasic allopolyploid species with n = 13 and 26, and its parent taxa, Aster falcatus Lindl. (x = 5) and Aster occidentalis Torr. & Gray (x = 8). Isozyme evidence confirms the derivation of A. ascendens from these two taxa. All populations and a high proportion of individual plants of A. ascendens possessed combinations of the alleles found in the parent species, and many individuals showed evidence of duplicated loci. However, fixed heterozygosity appeared to be less common than expected. Populations of A. ascendens resembled A. occidentalis much more closely than A. falcatus, and an UPGMA cluster analysis based on genetic identities showed that A. ascendens and A. occidentalis populations were closely intermingled, whereas A. falcatus populations were distinct. These results suggest that (i) A. ascendens has originated from multiple hybridization events involving different populations of A. occidentalis, and (ii) diploidization involving differential silencing of genes derived from A. falcatus may have occurred in A. ascendens.Key words: Aster, genetic variation, isozymes, allopolyploidy, diploidization, gene silencing.
Predicting the combined effect of herbivory and competition on a plant's shoot mass
Authors: Reader R J , Bonser S P
Published: April 2011

This study tested whether the shoot mass of a plant growing with both herbivores and neighbours present could be predicted using results of a herbivore-exclusion and neighbour-removal experiment. Since herbivory and competition from neighbours reduce shoot mass in different ways (i.e., tissue loss versus reduction in resource availability), we predicted that the shoot mass of a plant growing with both herbivores and neighbours present should equal the product of three terms; namely, the shoot mass of a plant growing without herbivores or neighbours present, the fraction to which herbivores alone reduced this shoot mass in the herbivore-exclusion treatment, and the fraction to which neighbours alone reduced this shoot mass in the neighbour-removal treatment. We tested this prediction for six herbaceous species, each growing in a different habitat. Values of shoot mass predicted for plants growing with herbivores and neighbours present did not differ significantly (P = 0.05) from actual values of shoot mass measured for the six species. Based on this result, we conclude that combined effect of herbivores and neighbours on shoot mass can be predicted accurately by simply multiplying the individual effects of these two factors, since herbivores and neighbours often have independent, complementary effects on shoot mass.Key words: plant growth, interactive effects, predators, neighbour effects.
Reexamination of taxa in Leptosphaeria originally described on host species in Ranunculaceae, Papaveraceae, and Magnoliaceae
Authors: Ahn Young-mee , Shearer Carol A
Published: April 2011

Type and authentic herbarium specimens of 16 taxa of Leptosphaeria found on hosts in Ranunculaceae, Magnoliaceae, and Papaveraceae were reexamined and reevaluated for their taxonomic position. The original taxonomic placements of Leptosphaeria haematites, Leptosphaeria papaveris, Leptosphaeria vitalbae, and Leptosphaeria weberi are confirmed. Leptosphaeria clematicola is described as a new species. Five species of Leptosphaeria are transferred to the other genera: Leptosphaeria agminalis, Leptosphaeria aucta, Leptosphaeria ranunculi, Leptosphaeria vitalbae Niessl, and Leptosphaeria stictoides are to Dothideopsella, Nodulosphaeria, Diademosa, Massariosphaeria, and Dothiora, respectively. Leptosphaeria andrijevicensis and Leptosphaeria incruenta are treated as synonymies of Phaeosphaeria minuscula and Broomella vitalbae, respectively. The previous synonymies of L. agminalis with Leptosphaeria rimalis, Leptosphaeria lasiosphaerioides with Nodulosphaeria modesta, Leptosphaeria bocconiae with Trichometasphaeria gloeospora, and Leptosphaeria pleosporoides with L. vitalbae are supported. Shared characters of the five species of Leptosphaeria mentioned above are presence of scleroplectenchyma in the ascomal wall, immersed to erumpent ascomata, oblong to cylindrical asci, and three to five septate, yellow-brown ascospores.Key words: Ascomycetes, Pleosporales, morphology, systematics.
Postglacial recolonization and the biogeography of Palmaria mollis (Rhodophyta) along the Northeast Pacific coast
Authors: Lindstrom Sandra C. , Olsen Jeanine L. , Stam Wytze T.
Published: April 2011

We used random amplified polymorphic DNA (RAPD) markers to examine the distribution of genotypes of Palmaria mollis (Setchell et Gardner) van der Meer et Bird, a red alga. We sampled populations along the Northeast Pacific coast from northern Washington to southwestern Alaska, an area extensively glaciated during the last ice age. Our objective was to determine whether the tracks of postglacial recolonization could be extracted from the extant pattern of genotype distribution in a species with limited dispersal capabilities. Thirty-eight individuals from 14 sites were sampled for RAPD markers using nine different random primers. As expected, individuals from the same population were more closely related to each other than to individuals from other populations. Relationships among populations, however, did not necessarily reflect geographic proximity. Rather, populations fell into groups corresponding approximately to outer and inner coastal sites: the northwestern end of Vancouver Island and the Queen Charlotte Islands formed one outer coast group, which associated with sites from Prince William Sound, the Alaska Peninsula, and Sitka, Alaska; the eastern side of Vancouver Island and Ketchikan, Alaska, represented one group of inner sites, which associated with sites near Juneau, Alaska and the eastern end of the Strait of Juan de Fuca. We conclude that this pattern does not represent a single postglacial recolonization event. Key words: biogeography, dispersal, genetic distance, Palmaria mollis, RAPDs, Rhodophyta.