bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphometric variation in a hybrid zone between the weed,Silene vulgaris,and the endemic,Silene uniflorassp.petraea(Caryophyllaceae), on the Baltic island of Öland
Authors: Runyeon-Lager Helena , Prentice Honor C
Published: April 2011

On the island of Öland the weed, Silene vulgaris (Moench) Garcke, and the endemic, Silene uniflora Roth ssp. petraea, hybridize when brought into contact by anthropogenic disturbance. Variation was studied in transects across a hybrid zone where a linear population of S. vulgaris crossed the native habitat of S. uniflora ssp. petraea. Plants were scored for 20 morphological characters. Although individual characters showed clinal trends between weed and endemic, all plants were assignable to one or other parental species. Only 14% of the 554 scored plants showed intermediacy in one or a few characters, and ordinations showed two separate groups of samples. The low number of intermediates is discussed in terms of character choice, habitat separation, disturbance history, and reproductive ecology. The results of the study are consistent with the earlier observation that the species have remained morphologically distinct on Öland, despite evidence of sparse introgression of allozymes from weed to endemic. Disturbance is necessary not only for the creation of intermediate (hybrid) habitats but also for the establishment of the weedy parent. The transient nature of S. vulgaris populations is likely to be important in limiting introgression into S. uniflora ssp. petraea under the present disturbance regime.Key words: genetic assimilation, hierarchical partitioning of diversity, habitat disturbance, introgression, rare species, clines.
Effects of wetting and drying on seed germination and seedling emergence of bull thistle, Cirsium vulgare (Savi) Ten.
Authors: Downs Michael P , Cavers Paul B
Published: April 2011

Seeds of bull thistle, Cirsium vulgare (Savi) Ten., were exposed to varying numbers of cycles of wetting and drying, in both Petri dishes and pots of soil, to investigate the effects of exposure to such cycles on subsequent germination of the seeds or emergence of the seedlings. Following exposure to the cycles, seeds in Petri dishes were set to germinate in one of four diurnal environments: 20:10°C alternating light and darkness, 20:10°C constant darkness, 30:15°C alternating light and darkness, or 30:15°C constant darkness. Total percent germination was reduced after exposure to eight cycles of wetting and drying, and germination rate was reduced after exposure to two or more cycles. Percent germination was reduced at the higher temperature but light availability had little effect. Reduction in seedling emergence in pots of soil after exposure to an intermediate number of cycles was greater than in Petri dishes but not as great with exposure to eight cycles. Seedling emergence patterns in pots that experienced any wetting-drying treatment were bimodal, with a second pulse of emergence several weeks after the termination of the cycles. This suggests that some seeds were induced into a dormant state through exposure to the cycles of wetting and drying. Such induced dormancy may serve to prevent seed germination in the autumn, promoting an attenuated and intermittent pattern of germination.Key words: Cirsium vulgare, bull thistle, wetting and drying, seed germination, induced dormancy, intermittent germination.
Modes of cell-wall degradation of Sphagnum fuscum by Acremonium cf. curvulum and Oidiodendron maius
Authors: Tsuneda A , Thormann M N , Currah R S
Published: April 2011

Electron microscopy of cryo-fractured hyaline leaf cells of Sphagnum fuscum Klinggr. revealed that their cell walls consist of three layers: a thick central layer flanked on either side by a thinner, amorphous layer. Acremonium cf. curvulum W. Gams and Oidiodendron maius Barron, both isolated from partly decomposed S. fuscum plants, were capable of degrading leaf cell walls of Sphagnum. Where hyphae of A. curvulum accumulated, the amorphous, outer wall layer of S. fuscum was first fragmented and then removed. The exposed central wall layer consisted of bundles of microfibrils embedded in an amorphous matrix material. After the matrix material and the inner surface wall layer were mostly removed, degradation of microfibrils occurred and localized voids were produced. Unlike A. cf. curvulum, O. maius degraded all wall components more or less simultaneously. In both fungi, active and autolysing hyphae frequently occurred in proximity on the Sphagnum leaves.Key words: hyphomycetes, peat, phenolics, cellulose, SEM.
Post-dispersal losses to seed predators: an experimental comparison of native and exotic old field plants
Authors: Blaney C S , Kotanen P M
Published: April 2011

Invasions by exotic plants may be more likely if exotics have low rates of attack by natural enemies, including post-dispersal seed predators (granivores). We investigated this idea with a field experiment conducted near Newmarket, Ontario, in which we experimentally excluded vertebrate and terrestrial insect seed predators from seeds of 43 native and exotic old-field plants. Protection from vertebrates significantly increased recovery of seeds; vertebrate exclusion produced higher recovery than controls for 30 of the experimental species, increasing overall seed recovery from 38.2 to 45.6%. Losses to vertebrates varied among species, significantly increasing with seed mass. In contrast, insect exclusion did not significantly improve seed recovery. There was no evidence that aliens benefitted from a reduced rate of post-dispersal seed predation. The impacts of seed predators did not differ significantly between natives and exotics, which instead showed very similar responses to predator exclusion treatments. These results indicate that while vertebrate granivores had important impacts, especially on large-seeded species, exotics did not generally benefit from reduced rates of seed predation. Instead, differences between natives and exotics were small compared with interspecific variation within these groups.Key words: aliens, exotics, granivores, invaders, old fields, seed predators.
Copper uptake in Typha latifolia as affected by iron and manganese plaque on the root surface
Authors: Ye Z H , Cheung K C , Wong M H
Published: April 2011

The effects of iron (Fe) and manganese (Mn) plaque on the accumulation of copper (Cu) in Typha latifolia L. were investigated under laboratory conditions in nutrient solution cultures. Seedlings with and without Fe plaque on their roots, induced with 15 or 60 µg·mL1 Fe, were exposed to 0.04, 0.12, or 0.36 µg·mL1 Cu solutions, and seedlings with and without Mn plaque, induced with 15 or 60 µg·mL1 Mn, were exposed to 0.12 or 0.36 µg·mL1 Cu solutions for 24 days, respectively. In all cases, the amount and proportion of Cu adsorbed on the root surface increased with a higher concentration of Cu in the solutions. In the presence of Fe or Mn, T. latifolia adsorbed more Cu and had a higher proportion of Cu on its roots, especially the roots with heavy Mn or Fe plaque. Although more Fe than Mn accumulated on the roots in the form of plaque, the Mn plaque adsorbed more Cu. The data suggest that root plaque can act as a Cu reservoir, depending on the amount of Fe or Mn on the roots and the amount of Cu in the environment.Key words: wetland plant, heavy metal uptake, cattail, iron plaque, manganese plaque.
Chrysophyte microfossils record marked responses to recent environmental changes in high- and mid-arctic lakes
Authors: Wolfe Alexander P , Perren Bianca B
Published: April 2011

Rapid stratigraphic changes are recorded in recent assemblages of subfossil Chrysophyceae from the sediments of two highly contrasted arctic lakes, one situated in the polar desert of west-central Ellesmere Island, and the other on eastern Baffin Island in the mid-Arctic climatic zone. In Sawtooth Lake on the Fosheim Peninsula, concentrations of chrysophycean stomatocysts increase dramatically in sediments deposited since AD 1920. Only trace abundances of stomatocysts are encountered in older sediments. In Kekerturnak Lake, on the north coast of Cumberland Peninsula, scales of Mallomonas spp., previously absent from the sediment record, appear suddenly in the upper 5.5 cm of sediment and subsequently become ubiquitous in the top 1.0 cm. These results corroborate diatom stratigraphic data from other sites in the Canadian Arctic Archipelago, together suggesting that unprecedented ecological changes are presently occurring across this vast region. In all likelihood, these abrupt algal community shifts reflect the response of arctic lake ecosystems to well-documented climate warming since the Little Ice Age, with the implications that recent rates of environmental change are unprecedented in the context of the Holocene.Key words: Paleolimnology, arctic lakes, Chrysophyceae, stomatocysts, Mallomonas.
Cyllamyces aberensis gen.nov. sp.nov., a new anaerobic gut fungus with branched sporangiophores isolated from cattle
Authors: Ozkose Emin , Thomas Barry J , Davies David R , Griffith Gareth W , Theodorou Michael K
Published: April 2011

A new genus of the anaerobic gut fungi (Neocallimastigales), Cyllamyces aberensis gen.nov. sp.nov., with bulbous holdfast, branched sporangiophores and limited polycentric thallus development is described. The fungus was isolated from fresh cattle faeces. Free-swimming zoospores were spherical, uninucleate, and uniflagellate. After encystment, zoospores germinated and gave rise to a single, bulbous holdfast. One or several branched sporangiophores were produced from different locations on the holdfast, each bearing several spherical sporangia. DAPI staining of thalli indicated that nuclei were present in the holdfast, sporangiophores, and sporangia. As many as 12 sporangia were observed per thallus on up to 5 sporangiophores, with zoosporogenesis beginning 1618 h after encystment. Zoospore ultrastructure was examined by transmission electron microscopy and found to be similar to that reported for other anaerobic chytrid fungi. Organelles were evenly distributed throughout the cell, except for the posteriorly attached flagellum and associated attachment apparatus, the hydrogenosomes, which were mainly situated in the posterior parts of the cell and a posteriorly directed, beak-shaped nucleus. Limited polycentric thallus development (including branched sporangiophores), the possession of a single bulbous holdfast and the absence of rhizoids were stable features of this fungus that distinguished it from the other five genera of gut fungi. Therefore, we have used these characteristics to assign the fungus to a new genus, Cyllamyces, with the specific name C. aberensis.Key words: rumen, fungal taxonomy, Neocallimastigales, chytrid, zoospore ultrastructure.
Differentiation of the sudden death syndrome pathogen of soybean, Fusarium solani f.sp. glycines, from other isolates of F. solani based on cultural morphology, pathogenicity, and mitochondrial DNA restriction fragment length polymorphisms
Authors: Rupe J C , Correll J C , Guerber J C , Becton C M , Gbur, Jr. E E , Cummings M S , Yount P A
Published: April 2011

Forty-four isolates consisting of Fusarium solani (Mart.) Sacc. f.sp. glycines Roy, Fusarium solani f.sp. phaseoli (Burkholder) W.C. Snyder & H.N. Hans., and F. solani, collected from a variety of hosts and locations, were compared based on pathogenicity on soybean and mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs). The 24 isolates of F. solani f.sp. glycines caused more severe sudden death syndrome (SDS) foliar symptoms and root rot on soybean compared with all other isolates. All isolates of F. solani f.sp. glycines belonged to a single mtDNA RFLP haplotype. The other isolates of F. solani belonged to nine mtDNA RFLP haplotypes distinct from that of the SDS pathogen and did not cause significant levels of SDS. Three isolates of F. solani f.sp. phaseoli in a single mtDNA RFLP haplotype were very similar to isolates of F. solani f.sp. glycines in culture. One of these isolates consistently produced SDS-like symptoms in pathogenicity tests, although at a low frequency. Fusarium solani f.sp. glycines represent a genetically distinct subgroup within F. solani but may be related to F. solani f.sp. phaseoli.Key words: Fusarium solani f.sp. phaseoli, Glycine max, sudden death syndrome (SDS), mtDNA.
Effects of altitude on tracheid differentiation and lignification of Norway spruce
Authors: Gindl W , Grabner M , Wimmer R
Published: April 2011

The effect of altitude on lignification is important in developing an understanding of what drives natural variation in wood properties. Cambia of two Norway spruce trees, growing at altitudes of 580 and 1260 m a.s.l., were periodically sampled to measure tracheid dimensions and cellular lignin content. The low-elevation tree showed a higher rate of cell division with thicker cell walls and wider growth rings. The maturation phase of tracheids at high elevation was completed by the end of October while low elevation latewood tracheids were still lignifying. As revealed by ultraviolet microscopy, lignin content in single cells, as well as in complete tree-rings, was higher at high elevation. Rank correlation analysis indicated high negative correlation between lignin content of tracheid cell walls and corresponding wall thickness. It is hypothesized that trees growing at higher altitudes compensate for the thinner cell walls with an increased lignin content which helps to maintain mechanical integrity of the xylem.Key words: altitude, lignin, tracheid, wood formation, ultraviolet microscopy.
A re-evaluation of species limits in Canadian Arctic Island Puccinellia (Poaceae): resolving key characters
Authors: Consaul L L , Gillespie L J
Published: April 2011

This study examined morphological variation for species of Puccinellia that have traditionally posed problems of identification in the Canadian Arctic Archipelago. The first part of the study involved a re-examination of several characters that were difficult to define or describe. Microscopic examination of lemma and glume apices revealed that the characters "erose-ciliolate" lemma and glume apex margins are more accurately divided into two characters: degree to which they are erose, and presence of trichomes. These trichomes consist of acute or acuminate cells that protrude 1535 µm from the margin, sometimes with a spinulose tip up to 10 µm long. The term "thickened pedicel" is clarified to mean thickened below the apex in relation to the apex. The second part of the study involved preliminary morphometric analyses on the above-mentioned revised characters, plus other characters previously shown to have low plasticity in this genus, for 10 recognized species that are difficult to distinguish. Many species or species complexes resolved to a small degree, but no taxa formed distinct groups. Correlations among many characters were low, accounting for a low percentage of variation explained by the first few principal components. Hypotheses of species boundaries and a preliminary revised key to species and species groups, incorporating findings from this study, are presented.Key words: Puccinellia, Canadian Arctic, morphology, trichomes, principal components analysis, cluster analysis.
Suitability of Glomus intraradices in vitro produced spores and root segment inoculum for the establishment of a mycorrhizosphere in an experimental microcosm
Authors: Filion M , St-Arnaud M , Guillon C , Hamel C , Jabaji-Hare S H
Published: April 2011

Various experimental systems have been developed to study the mycorrhizosphere. In this study, a microcosm experimental system was constructed and optimized to simulate the environments of the mycorrhizosphere: the rhizosphere, the mycosphere, and the bulk soil, using beans (Phaseolus vulgaris L.) as host plants. We investigated, in a time-course study, the effect of axenically in vitro produced spore inoculum and root segment inoculum of the arbuscular mycorrhizal fungus, Glomus intraradices Schenck & Smith, on extraradical mycelium development, rapidity of mycorrhizal colonization, and plant growth under nonsterile soil conditions. Three concentrations of in vitro produced spores and three concentrations of root segment inoculum produced from open pot cultures were used. The two highest concentrations of spores used as inoculum resulted in faster and more abundant colonization than when root segments were used. A significant correlation was obtained between hyphal densities present in the rhizosphere and mycosphere compartments, and the amount of spore inoculum used. The densities of roots in the rhizosphere compartment and hyphae in the rhizosphere and mycosphere compartments were comparable with field-grown plants; thus, the system realistically mimics a natural mycorrhizosphere. The use of the microcosm described in this study, in combination with the in vitro produced spore inoculum of G. intraradices, represents an experimental approach well adapted for studying the microbial ecology of the mycorrhizosphere.Key words: AMF, microbial ecology, inoculum, mycorrhiza, mycorrhizosphere.
The effects of logs, stumps, and root throws on understory communities within 28-year-old aspen-dominated boreal forests
Authors: Lee Philip , Sturgess Kelly
Published: April 2011

This study examined the role of logs, stumps, and root throws on the understory composition of aspen-dominated boreal forests. Measures of microsite coverage and suitability, and vascular plant composition and abundance were taken from 28-year-old wildfire and harvest sites. Larger logs (>20 cm diameter) with soft surfaces were the most suitable for colonization by vascular plants. These logs covered more than five times the area of stumps or root throws in both harvest and wildfire sites. Detrended correspondence analysis revealed that logs and stumps were colonized by a significantly different assemblage of vascular plants than the forest floor of either disturbance type. Contrary to studies in other forest types, assemblages of plants on root throw pits and mounds were similar to those on the forest floor. Initial colonization patterns on logs and stumps in both wildfire and harvest sites were similar. However, on more decayed logs assemblages of vascular plants were more similar to their respective wildfire or harvest forest floor assemblages. Ordination of species suggested that tree seedlings and shade-tolerant herbs were disproportionately more abundant on logs and stumps.Key words: plant community assemblages, deadwood resources, coarse woody debris, root throws, logs, boreal forest.
Strigolactones seem not to be involved in the nonsusceptibilty of arbuscular mycorrhizal (AM) nonhost plants to AM fungi
Authors: Illana Antonio , García-Garrido José M. , Sampedro Inmaculada , Ocampo Juan A. , Vierheilig Horst
Published: April 2011

Although most land plants are hosts for arbuscular mycorrhizal fungi (AMF), a small number of plant families are arbuscular mycorrhizal (AM) nonhosts. There are indications that strigolactone levels in root exudates of AM nonhost plants are lower than in AM host plants, and it has been shown that in the strigolactone-deficient rms1 mutant (ccd8) of the AM host plant pea, the AMF colonization of roots is highly reduced. Application of the synthetic strigolactone analogue GR24 to this strigolactones-deficient mutant restored AMF colonization of roots. Our objective was to determine whether the application of GR24 to AM nonhost plants can affect their susceptibility to AMF. To test whether GR24 affects AMF colonization in our experimental system, we added GR24 to the strigolactone-deficient pea ccd8 mutant. Application of GR24 increased AMF colonization in the pea mutant to a similar level as in the pea wild type with normal strigolactone levels, showing clearly that in our experimental setup, application of the GR24 positively affects AMF colonization in strigolactone-deficient plants. Observation of cleared roots after application of GR24 to four AM nonhost plant species inoculated with the AMF Glomus intraradices showed that colonization did not occur.
Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 5. Changes in free arginine and Sakaguchi-reactive compounds during callus growth and in germinating seedlings of similar genetic origin
Authors: Durzan D. J. , Chalupa V.
Published: April 2011

In friable callus, grown on a defined medium with arginine, and in jack pine seedlings, from which callus was derived, at least 18 Sakaguchi-reactive compounds and two N-phosphoryl derivatives were detected. When final size of callus was reached, the N in these substances contributed 0.1% to the total gain in dry weight and less than 0.6% to the gain in N. This was equivalent to a loss of 3 to 7% of the arginine N in the medium. For each callus, the total content of Sakaguchi-reactive compounds increased as the relative growth rates for weight and volume decreased. The increase was more pronounced when daughter cells adhered to clumps than at earlier stages when cells separated from one another. On a unit weight basis and as the cultures reached final size, the total Sakaguchi-reactive substances fell as γ-guanidinobutyric acid increasingly dominated the guanidine fraction. Exogenously supplied γ-guanidinobutyric acid caused a decrease in the final size of the cultured calluses when compared with calluses supplied with arginine. Levels of some of the remaining unidentified guanidines correlated positively with growth rates of calluses. By contrast, during the first 10 days of seedling growth Sakaguchi-reactive compounds contributed 12% of the net gain in N. The sequence of dominance of guanidines during growth was similar in both callus types and in seedlings, although some differences were noted.
β-1,3-Glucans may be associated with cell plate formation during cytokinesis
Authors: Fulcher R. G. , McCully M. E. , Setterfield G. , Sutherland J.
Published: April 2011

Sections of young lateral-root meristems of corn seedlings and Jerusalem artichoke tuber slices treated to induce cell divisions were stained with aniline blue and examined by fluorescence microscopy. In both tissues intense yellow fluorescence, similar to that given by callose in sieve plates, was observed in cell plates of cells undergoing cytokinesis and in recently formed transverse cell walls of newly divided cells. Staining was found after both chemical fixation and rapid freezing and was removed by prior β-1,3-glucanase treatment. The staining was not present in older walls. The results suggest that a unique polysaccharide, probably a β-1,3-glucan, is associated with the early stages of cell wall formation in cytokinesis. The role and fate of the polysaccharide are unknown.
Vegetation gradients of minerotrophically rich fens in western Alberta
Authors: Slack Nancy G. , Vitt Dale H. , Horton Diana G.
Published: April 2011

The vascular plant and bryophyte vegetation of 50 stands in nine sites from the foothills of western Alberta were quantitatively sampled in order to determine the major vegetation gradients. These fens are mostly patterned, with pools of water (flarks), alternating with raised ridges (strings), and are minerotrophically rich. Mean calcium ion concentrations of the nine fens range between 18 and 37 ppm and mean pH values range between 6.8 and 7.9, with electrical conductivities varying from 140 to 456 μmho/cm (1 mho = 1S). One string community type, dominated by Tomenthypnum nitens, Betula glandulifera, and Larix laricina. and one flark community type, dominated by Scorpidium scorpioides, Drepanocladus revolvens, and Carex limosa, are described, with three phases recognized in the flarks. (The Scorpidium scorpioides phase is most prominent in the wettest flarks, with the Campylium stellatum – Scirpus spp. phase found in slightly drier habitats.) The water chemistry and vegetation of these rich fens compares well with similar mires described from eastern Canada and Fennoscandia. Indirect and direct gradient analysis techniques illustrate a wet–dry ecological series of bryophytes rich in Amblystegiaceae and lacking in Sphagnaceae.
Correlation between the deposition of fluorescent compounds in papillae and resistance in barley against Erysiphe graminis hordei
Authors: Koga Hironori , Mayama Shigeyuki , Shishiyama Jiko
Published: April 2011

Events in the development of powdery mildew fungi and responses of barley epidermal cells were compared not only among combinations of barley and among races of mildew differing in virulence but also between epidermal cells adjacent and nonadjacent to stomata. Differences in fluorescence intensity and in the size of papillae and haloes were not observed until 12 h after inoculation; however, the fluorescence intensity and size of papillae increased rapidly and the differences became obvious 15 h after inoculation when the parasite penetrated into host cells. Failure of fungal penetration in incompatible combinations was mostly associated with papillae either with or without collapse of epidermal cells. The greater the resistance of barley, the greater was the rate of fungal cessation of growth at the papilla stage and the stronger was the fluorescence intensity of papillae. Haloes were larger in susceptible than in resistant hosts, but they usually did not form at sites where haustoria were produced.On the other hand, in incompatible combinations (with the [Formula: see text] genes), host epidermal cells adjacent to stomata (A cells) were less resistant than the nonadjacent ones (NA cells). More than 80% of haustoria formed were restricted to A cells, and about half of the conidia located in A cells formed haustoria. Many parasites of the remaining population in A cells ceased growth, followed by host cell collapse. In NA cells, most penetration pegs were terminated at the stage of papilla formation. The fluorescence intensity of papillae in NA cells was much stronger than that in A cells.It was suggested that cytologically specific events of compatibility or incompatibility are expressed at the papilla stage and that the fluorescent compounds deposited at the infection sites might represent chemical factors which are associated with resistance expressed at the stage of penetration, although it is not known whether the compounds as well as papillae themselves are a primary cause of resistance or a result of some unknown resistance mechanism.On compare des aspects du développement des champignons responsables du blanc de l'orge et les réactions des cellules épidermiques de l'orge, non seulement entre combinaisons d'orge et entre races de blanc différant par leur virulence, mais aussi entre cellules épidermiques adjacentes ou non aux stomates.
Chemosystematic studies in the genus Pseudotsuga. IV. Inheritance and geographical variation in the leaf oil terpenes of Douglas-fir from the Pacific Northwest
Authors: Rudloff E. Von , Rehfeldt G. E.
Published: April 2011

Quantitative terpene analysis of the leaf oils of 433 wild Douglas-fir trees from 87 northwestern localities, 66 wind-pollinated progenies of 4 trees from Idaho, 100 trees from 5 localities represented in a provenance trial, and 76 trees from four full-sib families of F1 intervarietal crosses allowed assessment of biosynthetic pathways, geographic variation, and modes of inheritance. Hypothetical biosynthetic pathways, derived from the cooccurrence of terpenes implied that the variation in 17 monoterpenes could be represented by three or four biogenetic pathways. As a result, geographic variation between the coastal and Rocky Mountain varieties can be described by the relative percentages of β-pinene, the terpinene–sabinene group of terpenes, the camphene group, and perhaps limonene. An abrupt reduction in the production of the camphene group occurs in going from interior to coastal populations. Moreover, patterns of segregation within four full-sib intervarietal hybrid families suggested that production of high relative percentages of the camphene group was governed by a single dominant gene. The dominant allele is characteristic of the Rocky Mountain variety, but isolated occurrences were also found on dry sites in coastal British Columbia. The recessive allele occurs far into the range of the Rocky Mountain variety. The coastal variety is characterized by the synthesis of relatively large amounts of β-pinene and the terpinene–sabinene group and their mode of inheritance is quantitative. Although concentrations of these terpenes decline towards the Rocky Mountains, genes controlling high amounts occur in populations of Idaho and western Montana. The variation in β-pinene and terpenes of the terpinene–sabinene group does not appear to be clinal. Trees with 5–10% ocimene are predominant in eastern Oregon. This terpene was found only in less than 1% amounts in trees from the coastal region and Montana and was practically absent in a provenance from Arizona. Hence it may serve to differentiate Rocky Mountain populations.
Ultrastructure and the taxonomy of Eocronartium
Authors: Khan S. R. , Kimbrough J. W.
Published: April 2011

Eocronartium has long been considered a parasitic Auriculariales, perhaps representing an ancestral form of our modern-day rusts of higher plants. Septal ultrastructure of two collections of E. muscicola reveals a pore structure essentially identical to those of the Uredinales and Septobasidiales and different from those of other Auriculariales studied thus far.
Studies of herbicide toxicity and mode of action using isolated mesophyll cells and callus-derived cell suspensions
Authors: Davis D. G. , Shimabukuro R. H.
Published: April 2011

Enzymatically isolated mesophyll cells of peanut (Archis hypogeae L.) and callus-derived cell suspensions of peanut and soybean (Glycine max (L.) Merrill) were assessed for their usefulness in studies of the toxicity and (or) mode of action of two bipyridilium herbicides (diquat and paraquat) and of perfluidone. Isolated mesophyll cells were very useful for rapid analyses of photosynthetic inhibition by 1 or 10 μM concentrations of the bipyridiliums. Cells treated with perfluidone were not affected. The growth of nonphotosynthetic callus-derived peanut cell suspensions was inhibited strongly either in the light or in the dark at 1 and 10 μM concentrations of either bipyridilium compound. Growth was slowed in cells treated with 0.1 μM diquat but not paraquat. In contrast, callus-derived soybean cell suspensions grew well in 1 μM diquat or paraquat; 10 μM of either herbicide strongly inhibited growth.Ultrastructural analyses of isolated mesophyll cells were of limited usefulness in assessing herbicide toxicity and mode of action because both untreated and treated enzymatically isolated peanut mesophyll cells had damaged membranes with extensive lipid deposits. In contrast, callus-derived soybean cell suspensions of both treated and untreated cells were undamaged for up to 6 days so that reduced growth of the cultures was not caused by destruction of organelles.
Wood decomposition by Phellinus (Fomes) pini: a scanning electron microscopy study
Authors: Blanchette Robert A.
Published: April 2011

Decomposition of white pine (Pinus monticola Dougl.) and western larch (Larix occidentalis Nutt.) by the white-pocket rot fungus, Phellinus (Fomes) pini (Thore ex Fr.) A. Ames, was investigated using scanning electron microscopy. White tissues surrounded by apparently sound wood characterized the decay. Latewood was first to be colonized and degraded. A selective degradation of lignin was observed. The middle lamella between tracheids was completely decomposed. The primary and secondary cell wall contained a macrofibrillar structure indicating lignin was removed leaving a cellulose framework. Macrofibrils 0.2–0.4 μm were present. In white-pocket regions, ray parenchyma was completely degraded. Sound wood, bordering white-pocket areas, usually consisted of early wood and resin-filled ray parenchyma. Fungal hyphae and bore holes were present in surrounding wood but decay typical of white-pocket rot was not observed. In addition to white-pocket rot, P. pini causes a brownish decay in wood near sporophores and punk knots that is ultrastructurally similar to decay by a white rot fungus. The potential use of white-pocket rot decay as a livestock feed and use of P. pini in a biological pulping process for the production of paper is discussed.
Ultrastructural evidence for the existence of actinorhizal symbioses in the late Pleistocene
Authors: Baker Dwight , Miller Norton G.
Published: April 2011

Macrofossil actinorhizal root nodules discovered in sediments about 11 500 radiocarbon years old in northern Vermont, U.S.A., were studied by scanning electron microscopy. Evidence of an endophytic microsymbiont was observed within the cortex of the fossil nodules. A comparative study as undertaken using root nodules from species of Alnus, Dryas, Elaeagnus, Myrica, Shepherdia, and Vicia native to eastern North America in an effort to determine the identity of the fossils. From qualitative and quantitative differences observed among the root nodule endophytes, it was concluded that the fossil nodules contained actinomycetes morphologically similar to those of extant Elaeagnaceae. The fossils are probably from plants of Elaeagnus commutata and (or) Shepherdia canadensis based on independent evidence of the representation of these species in the plant macrofossil assemblage.
A technique for preparing Beauveria spp. for scanning electron microscopy
Authors: Quattlebaum E. C. , Carner G. R.
Published: April 2011

Vapor fixation for 96 h with 1% osmium tetroxide (OsO4) and 3–4 days air drying produced distortion-free specimens of Beauveria spp. for examination with the scanning electron microscope. A combination of 4 h OsO4 vapor fixation and freeze-drying also reduced disruption satisfactorily but specimens were not as well preserved as with the first method. Preparation methods that were ineffective in preventing collapse of hydrophilic structures were Cling Free® sprayed on specimens prior to examination, freeze-drying, critical-point drying (of unfixed material), and vapor fixation with glutaraldehyde.
The use of flavonoids in the taxonomy of Boykinia and allies (Saxifragaceae)
Authors: Gornall R. J. , Bohm B. A.
Published: April 2011

All taxa of Suksdorfia, Hieronymusia, and Boykinia (including the segregates Neoboykinia, Peltoboykinia, and Telesonix), and one species each of Bolandra and Sullivantia were examined for their flavonoids. A diverse array of flavone and flavonol mono-, di-, and tri-glycosides was found. 3-O-Methylation and 6-oxygenation were common, as was 3, 7-O-triglycosylation. Groups of flavonol monoglycosides with either charged or acetylating functions were also observed. Taxonomically, the flavonoid relationships are many, various, and somewhat reticulate, indicating a close relationship among all taxa. The data provide only limited help in defining generic limits. They do, however, support the placement of Boykinia jamesii in Boykinia, or near it (as Telesonix), rather than in Saxifraga. The data also favour the retention of Neoboykinia within Boykinia. The exceptionally simple flavonoid profile of Boykinia tellimoides could support its elevation to generic rank (Peltoboykinia) were it made on other grounds. The evolutionary trends of flavonoid reduction and diversification are seen operating in the genera. Parallelism involving several different flavonoid structures is common in the Saxifraginae and supports the inclusion of Chrysosplenium in the subtribe.
Cadmium toxicity on synchronous populations of Chlorella ellipsoidea
Authors: Lue-Kim H. , Wozniak P. C. , Fletcher R. A.
Published: April 2011

The primary phycotoxic effects of various concentrations (5–50 μM) of cadmium sulfate (CdSO4) on synchronous cultures of Chlorella ellipsoidea were determined during a 14-h light and a 10-h dark incubation cycle. At a concentration of 5 μM CdSO4 there was a slight stimulation in cell number, chlorophyll level, and dry weight whereas at higher concentrations (10–40 μM) a linear decrease in these parameters was evident. At even higher concentrations, 50 μM and above, cytolysis occurred. Inhibition of chlorophyll concentration and dry weight was greater the longer the cultures were exposed to cadmium. Cell division was completely arrested when toxic levels of cadmium were administered any time throughout the duration of the light phase. However, the severity of toxicity of cadmium, when applied during the dark phase, increased with the length of time of exposure. Cadmium toxicity also resulted in disturbances in cell division. Treated cells became larger than control cells. Unequal sporulation, microcolony and incipient microcolony formation, swelling, increased photolucence, and disruption of mitochondria occurred following treatment of cultures with toxic levels of cadmium. A further toxic effect of cadmium might relate to an increase in membrane permeability. Treatment of cultures with increasing concentrations of cadmium resulted in intracellular cadmium exceeding extracellular cadmium levels. The primary toxic effect of cadmium on synchronous cultures of C. ellipsoidea was attributed to a lack of cell division probably related to insufficient synthesis of chlorophyll and dry weight components as well as to a disruption of membrane integrity.
Cotyledon test for major gene resistance to white pine blister rust in sugar pine
Authors: Kinloch Jr. Bohun B. , Comstock Mardi
Published: April 2011

Major gene resistance (hypersensitivity) to white pine blister rust can be detected on cotyledons of inoculated sugar pine seedlings shortly after germination. The cotyledon test reduces the time required for evaluating resistant genotypes from a few years to a few weeks.
Structure and composition of a post-fire ascomycete community: role of abiotic and biotic factors
Authors: Zak J. C. , Wicklow D. T.
Published: April 2011

The role of certain abiotic and biotic factors in determining the structure of a post-fire ascomycete community was studied by the laboratory simulation of soil conditions occurring during and following a prairie fire. Aerated steam treatment of prairie soil (35, 40, 55, 70, or 85 °C for 60 s) was used to simulate the elevated soil temperatures generated during a grassland fire. Further manipulations included: (1) addition of ashed remains of prairie grasses to steamed soil surfaces, (2) the incubation of steam-treated soil samples layered over untreated prairie soil, and (3) addition of ash to steamed soil underlain with a layer of untreated soil to create a simulated burn.Across all treatments, species diversity and total number of species were significantly higher in soils steamed at 35, 55, or 70 °C than soils steamed at 40 or 85 °C. The greatest number of species per sample for steaming alone occurred in samples treated at 55 °C. The addition of ash to steamed samples or layering with untreated prairie soil significantly reduced species diversity and total number of species as compared with steamed soil alone. When ash and a subsurface layer of untreated soil were applied together, species diversity, total number of species, and mean number of species for samples steamed at 55 or 70 °C, were significantly greater than when either treatment was added separately. It was found that a simulated burn at 55 or 70 °C promoted the development of a community which most closely resembled a naturally occurring post-fire ascomycete community. This suggested that the structure of the post-fire ascomycete community was in part determined by (1) species responses to elevated soil temperatures, (2) ash deposition, and (3) biotic factors associated with the subsurface soil layers.
A newly discovered serotype of Gremmeniella abietina
Authors: Wendler P. B. , Gotlieb A. R. , Bergdahl D. R.
Published: April 2011

The Asian, European, and North American serotypes of Gremmeniella abietina were compared with 27 Vermont isolates using gel double diffusion and intragel cross absorption tests. An intermediate serotype, between the North American and European serotypes, was shown by means of cross absorption with antiserum prepared in response to a Vermont isolate. The majority of Vermont isolates resembled the Vermont intermediate in serological reaction, three resembled the European serotype, and two were of unknown serotypes. The serological data support possible hybridization between G. abietina isolates in Vermont as well as the identification of a new serotype in Vermont.
Gas exchange rates and nitrogen concentrations in two winter wheat cultivars during the grain-filling period
Authors: Migus W. N. , Hunt L. A.
Published: April 2011

CO2 exchange (CER) and transpiration (TR) rates of flag leaves, penultimate leaves, and the ear of two winter wheat cultivars (cv. Fredrick and cv. Bezostaya-1), were measured at intervals during the life of the flag leaf. These were grown at two levels of nitrogen (N), 105 and 210 mg L−1, supplied from the double ridge stage of apical development. Nitrogen concentrations and dry weights of the flag and penultimate leaves, and of various other plant parts, were also measured.CER of main culm flag leaves of both cultivars declined more slowly from ear emergence to approximately 2.5 weeks postanthesis than either before or after this period. Similarly, the CER pattern of main culm penultimate leaves of Fredrick showed a plateau during this same period. By contrast, CER of the penultimate leaves of Bezostaya declined more uniformly overtime. CER of illuminated ears declined steadily from anthesis, whereas CER in the dark decreased to a maximum negative value approximately 2 weeks postanthesis. Nitrogen treatment had little effect on these CER patterns, with the exception of Bezostaya penultimate leaves, in which the rate of decline was slower for the higher N treatment.Nitrogen concentrations of the flag and penultimate leaves, and in the nongrain ear component, decreased steadily during the grain-filling period for both cultivars and N treatments. Leaf N concentration also decreased during the preanthesis period in Fredrick at both N treatments, and in Bezostaya at the lower N treatment. The time – course of N concentration in the leaves was not closely mirrored by CER, indicating that factors other than the N concentration of the leaves were important in determining the pattern of CER.TR of the flag and penultimate leaves declined from full flag leaf expansion until anthesis and then rose during a 2- to 2.5-week-postanthesis period for both cultivars and N treatments, with the exception of Bezostaya at the lower N treatment. The increase in TR during the filling period suggests that the reduced rate of decline in CER at that time may have resulted, at least partly, because a reduction in gas phase resistance offset an increase in residual resistance.
Long-term effects of smelter pollution at Sudbury, Ontario, on forest community composition
Authors: Freedman B. , Hutchinson T. C.
Published: April 2011

Forest communities were quantitatively analyzed along a south-southeast transect from a large, 70- to 80-year-old smelter complex near Sudbury, Ontario. None currently exist within 3 km SSE of this smelter. At distances of up to 8 km, pockets of remnant forest communities of various sizes occur, mainly on protected slopes and in valley bottoms. Most hilltops are bare of vegetation, denuded of soil, and blackened from the effects of sulfur dioxide fumigations. Beyond this distance, the forests are more or less continuous, although there are still some bare hilltops as far as 15 km from the smelter. The forests which do occur are relatively depauperate in terms of tree diversity and biomass at the closer sites. Similar effects on the ground flora are also documented, although the forest canopy appears to be more greatly affected than the ground flora. Certain species are widely distributed in the inner polluted areas, while others, notably conifers and such ground flora components as bracken fern and most lichens and bryophytes, are absent from sites closer to the smelter.Some changes in the plant communities close to the Copper Cliff smelter have occurred subsequent to the building of a tall (380 m) smokestack in 1972. These have mainly occurred at sites where soils remain, where residual soil toxicity is not excessive, and where midsummer drought is not severe. Colonization has largely involved the spread of such pioneer grasses as Agrostis hyemalis var. tenuis, A. stolonifera var. major, and Deschampsia caespitosa, and more vigorous growth of certain surviving woody species. The recovery of denuded, blackened hilltops, essentially a primary succession on naked Precambrian bedrock, will be a much slower process.
A further comparison of Isoetes roots and stigmarian appendages
Authors: Karrfalt Eric E.
Published: April 2011

Four additional structural similarities between the roots of Isoetes and Stigmaria are reported. Proximal swellings and connectives are reported for the first time in Isoetes roots. The size ranges of the roots of Isoetes and Stigmaria are shown to overlap, and a definite epidermis is described for the first time on the roots of Stigmaria. The structural diversity present among the roots of various lycopods is reviewed. It is concluded that the root is of polyphyletic origin within the Lycopsida. The roots of Lycopodium and Selaginella show many similarities with stems and are considered to be derived from the stems of some rootless ancestor, whereas the roots of Isoetes and the lepidodendrids show many similarities with their own leaves and are considered to be derived from leaves or from some less specialized appendages from which both the leaves and roots of these plants were derived.
Spiniferomonas (Chrysophyceae) in Ontario lakes including a revision and descriptions of two new species
Authors: Nicholls Kenneth H.
Published: April 2011

The little known chrysophycean genus Spiniferomonas Takahashi is an important component of the phytoplankton of many Ontario lakes. Ten species have been found, only three of which (S. trioralis Tak., S. bourrellii Tak., and S. andersonii Green) are known previously from North America. Two species (S. andersonii, S. conica Tak.) are shown to be synonymous with the type species, S. bourrellii. Two new species are described (Spiniferomonas takahashii and Spiniferomonas serrata) and a revised key to all known species is presented.Spiniferomonas trioralis is the most abundant and widely distributed species in Ontario and is clearly eurytopic in its requirements for growth. It is common in a variety of lakes having Secchi disc visibilities of 2–10 m and pH and alkalinity ranges of 5.8–8.5 and 5–150 mg CaCO3/L, respectively.