bluuebunny/crossref_metadata_2025 huggingface dataset:
A biosystematic study of the Carduus nutans complex in Canada
Authors: Desrochers A. M. , Bain J. F. , Warwick S. I.
Published: April 2011

The Carduus nutans L. complex in North America has been treated either as one species with four subspecies (ssp. nutans, ssp. leiophyllus (Petrovic) Stoj. & Stef., ssp. macrolepis (Peterm.) Kazmi, and ssp. macrocephalus (Desf.) Nyman) or as three species: Carduus nutans with two subspecies (ssp. nutans and ssp. macrolepis), C. thoermeri Weinm., and C. macrocephalus Desf. A biosystematic study of this complex, including morphological, flavonoid, and isozyme analyses, of 19 populations, was conducted to clarify the taxonomy of this complex in Canada. Both the morphological and flavonoid analyses clearly indicate the existence of only two closely related groups of taxa referable to ssp. nutans and ssp. leiophyllus. The classificatory discriminant analysis indicated correct classification rates of individuals of 93.6% and 96.0% for ssp. nutans and ssp. leiophyllus, respectively. Each taxon has a distinct flavonoid profile. Given the high mean genetic identity value (ī = 0.93) between the two taxa in the complex, and the estimates of genetic variability obtained, the taxa are best treated at the subspecific level, as ssp. nutans and ssp. leiophyllus.
Short-term effects of nitrate on nitrate reductase activity and symbiotic dinitrogen fixation in faba bean and pea
Authors: Chalifour Francois-P. , Nelson Louise M.
Published: April 2011

The effects of a short-term supply of combined nitrogen (N) on the Rhizobium–legume symbiosis were studied in faba bean (Vicia faba L.) and pea (Pisum sativum L.) nodulated by R. leguminosarum biovar viceae isolate 175F5 or 175F19 and subjected to increasing levels of [Formula: see text] (0, 5, 10, or 20 mol∙m−3) from 28 to 36 days after planting. Trends in N2-fixing activity (acetylene reduction) showed that faba bean was more tolerant to [Formula: see text] than pea with isolate 175F5 but not with isolate 175F19. Nitrite reductase activities in the leaf, root, and nodule cytosol fractions were severalfold higher than nitrate reductase activities for both hosts. The levels of these enzymes in the nodule cytosol, the absence of bacteroid nitrate reductase and the lack of induction of bacteroid nitrite reductase in response to [Formula: see text] addition are consistent with the lack of [Formula: see text] accumulation in nodules of both hosts. Therefore, it is unlikely that the inhibitory effects of [Formula: see text] on N2 fixation are due to [Formula: see text] inhibition of nitrogenase. The relative levels of nitrate reductase activity in the root and nodule cytosol fractions were, respectively, higher and lower in the two faba bean symbioses ([Formula: see text] tolerant) and in the pea–175F5 symbiosis ([Formula: see text] sensitive) than in the pea–175F19 symbiosis ([Formula: see text] tolerant).
Improving microspore culture as a rapeseed breeding tool: the use of auxins and cytokinins in an induction medium
Authors: Charne D. G. , Beversdorf W. D.
Published: April 2011

The effect of naphthaleneacetic acid (NAA), an auxin, and N6-benzyladenine (BA), a cytokinin, on microspore embryogenesis in two F1 (hybrids of rapeseed (Brassica napus L.) was investigated, using a two-factor, central-composite response surface design. Total embryo yields of both hybrids increased in a log-linear fashion with BA concentrations in the range 0.01–0.255 mg L−1; within this range, yields approximately doubled for every fivefold increase in BA concentration. NAA concentrations of 0.136–1.85 mg L−1 had no effect on embryo yields. Within the range of concentrations studied, neither growth substance had any effect on the proportion of cotyledonary embryos produced. When cotyledonary embryos were regenerated on B5 medium without hormones, no significant effects on either root development or shoot production attributable to the NAA–BA treatments could be detected. In general, higher embryo yields were associated with a slower rate of development, but a greater degree of morphological synchrony within individual cultures.
Studies on mycorrhizal associations in Harvard Forest, Massachusetts
Authors: Berliner Ruhama , Torrey John G.
Published: April 2011

An estimate was made of the abundance of different types of mycorrhizal associations in two plant communities of conifers and hardwoods in the Harvard Forest. Lists of plant species, the coverage of their foliage in the canopy and understorey layers, and the types of mycorrhizal associations for 45 species common in these communities are presented. Of the species examined, 91 % were mycorrhizal, representing most of the known major types, viz. ectomycorrhiza, vesicular–arbuscular mycorrhiza (VAM), ericoid, and monotropoid mycorrhiza. Of the 45 species studied, 22% of the species showed ectomycorrhizal, and 71 % VAM associations. A direct spore count was a more reliable method than the most probable number method for determining VAM occurrence in the soil. Spore numbers ranged from 4.4 to 11.8 spores/g oven-dried soil. In conifer stands, ectomycorrhizae were most common, although VAM were also observed in the conifer species. In hardwood stands, VAM were more frequent than in conifer stands, but mycorrhizae were heterogeneous and included a good proportion of the ericoid type. Ectomycorrhizae were more common in communities of low diversity; VAM occurred more frequently in communities of high plant species diversity.
Multiple metal stress in Triticum aestivum. Differentiation between additive, multiplicative, antagonistic, and synergistic effects
Authors: Taylor Gregory J.
Published: April 2011

Aluminum toxicity is an important factor limiting plant growth in soils with pH below 5.0. Because metalliferous soils are commonly acidic, understanding plant growth dynamics on such soils may require insight into the interaction between aluminum and other phytotoxic metals. To investigate potential interactions in the phytotoxicity of nickel and aluminum, seedlings of Triticum aestivum L. cv. Neepawa were grown for 14 days in solution culture with varying concentrations of nickel (0–60 μM), with or without 40 μM aluminum. Increasing concentrations of nickel were observed in roots (232–2318 μg ∙ g−1) and leaves (25–152 μg ∙ g−1) with increasing nickel in solution, but concentrations were reduced with addition of aluminum as a second phytotoxic metal (roots: 125–1314 μg ∙ g−1; leaves: 20–108 μg ∙ g−1). Aluminum was only detectable in roots of seedlings grown with aluminum and declined with increasing nickel in the growth solution (1446–530 μg ∙ g−1). Addition of nickel to growth solutions reduced both root (0.981–0.193 g) and leaf (2.608–1.030 g) weights. Aluminum as a second phytotoxic metal further reduced root (0.698–0.194 g) and leaf (2.245–1.111 g) weights at low concentrations of nickel in solution. Analysis of variance of the root weight data indicated a significant nickel × aluminum interaction, but this may not have been indicative of a biological interaction. Root weight, both in the presence and absence of aluminum, decreased to a common minimum at high concentrations of nickel in the growth solution, possibly reflecting biomass present at the onset of experimental treatments and the lag time required for the expression of the phytotoxic growth response. When root growth relative to control was expressed as weight above the empirical minimum (the root weight index), results of the analysis of variance were different. Significant main effects of nickel were detected, while main effects due to aluminum and the nickel × aluminum interaction were not significant. Despite antagonistic effects observed with metal uptake and accumulation, such results suggest that the combined toxic effect of nickel and aluminum can be explained by a simple multiplicative model.
Stem anatomy of Vaccinium section Cyanococcus and related taxa
Authors: Odell A. E. , Kloet S. P. Vander , Newell R. E.
Published: April 2011

Twenty-nine Vaccinium species were scored for 14 stem and twig characters to determine whether or not vegetative features would support current taxonomic delimitations within the genus. The data obtained show not only that the verrucose characteristic of the twigs, one of the character states that defines Vaccinium section Cyanococcus, is caused by the presence of raised stomata, but also that members of this section have a peculiar mode of periderm development. In addition to the type of periderm development, the occurrence of lignification in twigs and stems was also noted, but was found not to be taxonomically useful at the sectional rank.
Effects of silica level on some properties of Oryza sativa straw and hull
Authors: Balasta Maria Luisa F. C. , Perez Consuelo M. , Juliano Bienvenido O. , Vlllareal Corazón P. , Lott John N. A. , Roxas Domingo B.
Published: April 2011

Reduction of silica content of two rice varieties obtained by growth in hydroponic solutions (0–400 ppm added SiO2) increased leaf openness and decreased both stem bending hardness and hull weight. The number of silica bodies in the surface of leaf blades was similarly decreased. Mapping by energy dispersive X-ray analysis techniques showed high concentrations of silicon in silica bodies inside silica cells on leaf blades and uniform distribution on lemma and palea surfaces. Vascular tissues and bulliform cells were also rich in silica. Decrease in silica content to less than 10% dry weight increased the in vivo dry matter digestibility of straw in both varieties and increased the in vitro organic matter digestibility of IR36 straw.
A growth analysis of waterlogging damage in mung bean (Phaseolus aureus)
Authors: Musgrave Mary E. , Vanhoy Mary Alice
Published: April 2011

Mung beans (Phaseolus aureus Roxb.) were grown for 2 weeks in gravel–vermiculite soilless mix in a growth chamber and subjected to a 1-week waterlogging period followed by a 1-week recovery period. Sequential harvests were made to determine the time course of effects of waterlogging and subsequent recovery on growth parameters by techniques of growth analysis. Root dry matter was the first to be affected, along with an increase in leaf dry matter and specific leaf weight. After a 1-week waterlogging period, specific leaf weight had more than doubled in the stressed plants. Leaf area declined in relation to the control plants as did the ratio of root dry matter to shoot dry matter. During the recovery period there was an increase in the dry matter allocation to the roots relative to the shoot. Specific leaf weight fell to control levels although the rate of leaf area elaboration did not increase during this time, suggesting a redistribution of stored assimilates from the leaves. Net assimilation rate increased during the waterlogging period, probably due to a restriction in root metabolism and reduced translocation out of the leaf rather than to an increase in photosynthesis. Net assimilation rate of waterlogged plants was severely reduced compared with control plants during the recovery period. Both relative growth rate and leaf area duration declined during the waterlogging period and declined further subsequent to the waterlogging treatment. The results illustrate the interrelationships between root and shoot carbon budgets in mung bean during response to the stress of waterlogging.
Pollen wall formation in Abies concolor and a discussion on wall layer homologies
Authors: Kurmann Marie H.
Published: April 2011

Development of the pollen wall in Abies concolor (Gord. & Glen.) Lindl. is documented using ultrastructural techniques. Pollen wall formation is initiated by the deposition of a microspore surface coat and the formation of callosic protrusions in the proximal and lateral areas, outside the plasma membrane of the microspores enclosed in tetrads. The alveolar ektexine is then elaborated on these structures. Endexine formation starts with the appearance of tripartite lamellae to the inside of the microspore surface coat around the entire microspore. Both the ektexine and endexine are elaborated while the microspores are enclosed in tetrads by the callose wall. These results are utilized in assessing homologies between various wall layers in gymnosperm and angiosperm pollen. In considering criteria of homology, pollen wall development is discussed as a causal sequence and this discussion concludes that the ektexine and endexine in gymnosperm pollen are homologous with the ektexine and endexine in angiosperm pollen.
Dynamics of arbuscule development and degeneration in onion, bean, and tomato with reference to vesicular–arbuscular mycorrhizae in grasses
Authors: Alexander Tom , Toth Ronald , Meier Rose , Weber Hans Christian
Published: April 2011

A quantitative light and electron microscopic study of developing and degenerating arbuscules of the vesicular–arbuscular mycorrhizal fungus Glomus fasciculatum in onion, bean, and tomato was carried out to estimate three parameters during the colonization cycle and to compare these parameters with those in maize, oats, and wheat. The parameters are (i) Vv(a,c) the fraction of the host cell volume (c) occupied by the arbuscule (a); (ii) VV(cy,c) the fraction of the host cell volume occupied by host cytoplasm (cy); and (iii) SV(p,c) the ratio of the surface area of the host protoplast (p) to the volume of the whole host cell. Uninfected cortical cells contained 3.4% cytoplasm in onion, 3.1% in bean, and 3.5% in tomato. In cells with mature arbuscules, cytoplasm increased to 9.9% in onion, 14.2% in bean, and 13.6% in tomato. Cells with mature arbuscules contained 11.4% fungus in onion, 20.3% in bean, and 20.5% in tomato. The initial SV(p,c) in onion was 0.10 μm2/μm3 and in bean and tomato 0.11 μm2/μm3. This increased to 0.37 μm2/μm3 in onion, 0.82 μm2/μm3 in bean, and 0.54 μm2/μm3 in tomato by the time arbuscules were mature. Development of the arbuscule was estimated to take 2.5 days and occupied 33% of the total cycle time. The variation seen across host species can be used as an indicator of fungal and (or) host control for each parameter. Arbuscular parameters of onion were compared with those obtained by other authors.
Paraphysomonas caelifrica new to North America and an amended description of Paraphysomonas subrotacea (Chrysophyceae)
Authors: Nicholls K. H.
Published: April 2011

Two little-known unpigmented species of the chrysophyte genus Paraphysomonas are reported. Paraphysomonas caelifrica Preisig & Hibberd was found in samples collected from an Ontario pond in the autumn of 1985; it had not been reported previously from North America. An amended description is given of Paraphysomonas subrotacea Thomsen that includes reniform scales observed in the type material from Denmark and other localities including Ontario.
Cylindrocladium leucothoeae sp.nov.
Authors: El-Gholl N. E. , Leahy R. M. , Schubert T. S.
Published: April 2011

Cylindrocladium leucothoeae is described as a new species from leaf spots on Leucothoe axillaris from Florida.
The rusts (Uredinales) of arctic Canada
Authors: Parmelee J. A.
Published: April 2011

Fifty-three taxa in 11 genera are described and illustrated from the Canadian Arctic. Included are a key to the genera and keys to the species within each genus. Prior records in many journals mostly lacked illustrations. Herein light microscope photographs are complemented by SEM photographs to show spore wall ornamentation, an essential character in species delimitation.
Wild oat and barley interactions: varietal differences in competitiveness in relation to phosphorus supply
Authors: Konesky D. W. , Siddiqi M. Y. , Glass A. D. M. , Hsiao A. I.
Published: April 2011

Nine cultivars of barley (Hordeum vulgare L.) were separately planted with wild oat (Avena fatua L.) in sand culture at two external phosphorus concentrations. Barley cultivars differed substantially in their ability to compete with wild oat. Relative competitive abilities of the barley cultivars were strongly influenced by external phosphorus levels. The greatest effect of competition, particularly at low external phosphorus, was upon plant biomass rather than on internal total phosphorus concentration. The selection of cultivars that are able to compete effectively with wild oat may represent an alternative (biological) strategy to the traditional one of herbicide application.
The effects of pH and ammonium on the distribution of manganese in Triticum aestivum grown in solution culture
Authors: Macfie Sheila M. , Taylor Gregory J.
Published: April 2011

Roots of manganese-tolerant Triticum aestivum (cv. Norquay), grown in solution culture with 500–1000 μM manganese, showed brown discolouration, reflecting precipitation of manganese on root surfaces. Under similar conditions, roots of manganese-sensitive 'Columbus' lacked a precipitate and remained white. Precipitation of manganese on root surfaces was correlated with a plant-induced rise in pH of culture solutions above 5.5. Increasing ammonium in solution from 0.3 to 0.6 mM prevented the rise in pH, and precipitation of manganese was not observed. Dry weights of roots and leaves of 'Norquay' were higher than those of 'Columbus' over a range of concentrations of manganese (200–1000 μM), regardless of amount of ammonium supplied. With 0.3 mM ammonium in solution, roots of 'Norquay' accumulated approximately twofold higher concentrations of manganese than roots of 'Columbus', whereas concentrations of manganese in leaves were similar. With 0.6 mM ammonium in solution, concentrations of manganese associated with roots decreased and concentrations of manganese in leaves increased. Nonetheless, roots of 'Norquay' maintained twofold higher concentrations of manganese than roots of 'Columbus', and differences for leaves remained small. In contrast with previous reports, brown discolouration of roots of T. aestivum is not necessarily a symptom of manganese toxicity. Precipitation of manganese on root surfaces was related to pH of solutions, could be reduced by the addition of ammonium, and did not affect tolerance of manganese for the cultivars studied.
Chaetomium sinaiense sp.nov., a new soil ascomycete from Egypt
Authors: Moustafa A. F. , El-Din E. K. Ess
Published: April 2011

Chaetomium sinaiense sp.nov. is described and illustrated from Egyptian soil. It is characterized by undulate, articulate, smooth to finely verrucose ascomatal hairs, clavate asci, large, broadly fusiform, biapiculate ascospores, 20–22 × 16–18 μm, each with a single, mostly subapical, protuberant germ pore. A brief comparison with morphologically related species is included.
Morphological and chemical studies of Penicillium oxalicum, newly identified as a pathogen on greenhouse cucumbers
Authors: Jarvis W. R. , Barrie S. D. , Traquair J. A. , Stoessl A.
Published: April 2011

Identification of the fungus designated as Penicillium crustosum Thom causing stem and fruit rot of greenhouse cucumbers (Cucumis sativa) as Penicillium oxalicum Currie and Thom has been substantiated by morphological and chemical studies. Scanning electron microscopy and light microscopy revealed elliptical conidia produced on smooth-walled conidiophores characteristic of P. oxalicum. Colonies were velvety in texture and blue-green in color. Secalonic acid D and oxaline were isolated from Czapek – yeast extract agar cultures and identified through their physical constants and mass, infrared, ultraviolet, and proton nuclear magnetic resonance spectra. Secalonic acid D was obtained also from Czapek–Dox broth cultures together with a previously undescribed compound, which we have named penoxin. In addition, oxalic acid and calcium oxalate were detected in these cultures by gas chromatography and light microscopy of crystals. Morphological and chemical observations are consistent with published descriptions of P. oxalicum. This is the first report of P. oxalicum causing a storage rot of cucumber and tomato fruit. Key words: stem and storage rot, identification, penoxin.
Somatic embryogenesis and plantlet regeneration from cultured shoots and cotyledons of seedlings from stored seeds of black and white sprees (Picea Mariana and Picea glauca)
Authors: Attree S. M. , Budimir S. , Fowke L. C.
Published: April 2011

Embryogenic callus was induced from cultured explants of 12- to 30-day seedlings germinated from 10- and 4-year stored seeds of black and white spruce, respectively. Plantlets were regenerated from a 12-day black spruce seedling derived embryogenic callus. This is the oldest conifer seedling material shown to give rise to embryogenic callus, and the first demonstration in spruce that seedling-derived embryogenic calli are competent of plantlet regeneration. The effect of a cytokinin pretreatment on embryogenic callus induction from 12-day black spruce seedling shoot explants was investigated. Although an induction frequency of 18% occurred after 2 weeks preculture of shoot explants on medium containing 4.5 μM benzyladenine, the cytokinin pretreatment was not significantly superior to controls given no pretreatment (12%). Age of explant influenced embryogenic induction frequencies from black and white spruce. Explants from 21-day black spruce seedlings produced embryogenic calli at a frequency of 5%. In comparison, shoot explants from 12- and 30-day white spruce seedlings given no benzyladenine pretreatment displayed induction frequencies of 38 and 18%, respectively.
Cytochemistry and ultrastructure of the dehiscence zone of almond (Prunus dulcis) fruits
Authors: Weis K. , Polito V. S.
Published: April 2011

At maturity, the almond pericarp dehisces along the ventral suture, a region that originates by fusion of epidermal cells and subsequently differentiates into a separation layer. We have characterized the ontogeny of the fusion–dehiscence zone with emphasis on cell wall characteristics by using cytochemical methods for detection of pectin, cutin, cellulose, and lignin to examine the middle lamellae and primary and secondary walls in dehiscence-zone cells. Carpel margins became united postgenitally along opposing epidermal layers giving rise to the suture. Fusion-zone cells host epidermal characteristics, elaborated broad pectinaceous walls, and ultimately formed a discrete band of cells that dehisced along the original line of fusion by dissolution of cell wall pectins. Treatment of treeborne fruits with 1 ppm ethylene gas or extraction of sectioned material with cell wall hydrolases resulted in cell wall changes similar to those in predehiscent fruits.
A note on the taxonomic status of Euphrasia randii (Scrophulariaceae)
Authors: Downie Stephen R. , McNeill John
Published: April 2011

A reexamination of the phenetic relationships among the previously recognized infraspecific taxa of Euphrasia randii using principal component analyses and four clustering methods indicates that the recognition of these infraspecific taxa is unwarranted. This complex exists as one morphologically variable taxon, E. randii.
Relative fitness of races 1 (0) and 3 (0, 1) of rust (Puccinia helianthi) in mixtures on susceptible sunflower (Helianthus annuus)
Authors: Prud'homme Anne-Marie , Sackston W. E.
Published: April 2011

Race 1 (race 0 according to new international designation) of sunflower rust (Puccinia helianthi) remained dominant in the rust population for years after cultivars carrying the R1 gene conferring resistance were commonly grown, even though race 3 (0, 1), which is able to overcome R1, was present in nature when cultivars with R1 were first released. A mixture with originally equal proportions of races 1 and 3 was maintained for eight spore generations on line CM 303 susceptible to both races. Race 1 increased from 41% in the 1st generation to stabilize at 95% by the 5th. Factors that might contribute to the apparent greater fitness of race 1 under controlled conditions, including germination percentage of spores on the leaf surface, growth rate of germ tubes, formation of appressoria, size of mycelial colonies within leaves, size and density of pustules on leaves, and spore production, were compared. The critical factors appeared to be the higher germinability, more rapid germination, and more rapid formation of appressoria by spores of race 1.
Pollen morphology of Deinostema, Geochorda, Gratiola, Ildefonsia, Sophronanthe, and Tragiola (Scrophulariaceae, Gratioleae, Gratiolinae)
Authors: Argue Charles L.
Published: April 2011

The pollen grains of Deinostema, Geochorda, Gratiola, Ildefonsia, Sophronanthe, and Tragiola are single, isopolar to anisopolar, and radially symmetrical, with three or four equally spaced meridional colpi. Pollen grains of Ildefonsia and Geochorda are semitectate with a relatively well-developed to intermediate sexine 1 (interstitium). In Ildefonsia the sexine 2 (tectum) is comprised of a complex network of vertically overlapping, interwoven muri, and a baculate sexine 3 is present. In Geochorda the muri are not vertically interwoven and the sexine 3 is absent. The grains of Deinostema, Gratiola, Sophronanthe, and Tragiola are tectate–perforate, lack a baculate sexine 3, and have a reduced to intermediate sexine 1. All of the taxa examined except Geochorda are distinguished from the Mimulinae by pollen morphology. The pollen evidence in Deinostema, Gratiola, Sophronanthe, and Tragiola correlates with the floral data and is consistent with a mutual relationship among these genera. The pollen grains of Geochorda and Ildefonsia are distinct from one another and from those of the other genera examined. Pollen of the latter is of a morphotype not previously reported in tribe Gratioleae.
The influence of dung pats and molehills on pasture composition
Authors: Parish Roberta , Turkington Roy
Published: April 2011

The abundance and distribution of plant species, molehills, and dung pats were surveyed on eight occasions over 26 months in three adjacent pastures of different age. There were few features related to pasture age, but each pasture had a different disturbance regime. Dung deposition and molehill distribution usually fitted Poisson and negative binomial distributions, respectively. The abundance of some species responded to current disturbances, e.g., Trifolium repens, and others to disturbances in the previous season, e.g., Lolium perenne. Holcus lanatus abundance declined in areas of high disturbance, whereas Dactylis glomerata, Agropyron repens, and Taraxacum officinale abundance increased. The response patterns of these species are discussed in the context of season, year, pasture age, and type of disturbance. Key words: disturbance, dung, molehill, pastures.
Histological evidence of resistance to Endocronartium harknessii in Pinus contorta var. latifolia
Authors: Allen E. A. , Blenis P. V. , Hiratsuka Y.
Published: April 2011

Resistance to the western gall rust fungus, Endocronartium harknessii, was observed in 3-, 10-, 20-, and 33-month-old greenhouse-grown seedlings of lodgepole pine (Pinus contorta var. latifolia). Three sites of resistance were identified: epidermal, cortical, and cambial. In cases of epidermal resistance, penetration of the epidermis occurred, but infection was prevented by an apparent hypersensitive response. Cortical resistance occurred where infected cells in the cortex were successfully isolated by necrophylactic periderm and the infected tissue was exfoliated with the rhytidome. In cambial resistance, infections progressed to the vascular cambium where infected cells and cambial initials were inactivated. This resulted in abnormal secondary xylem development, characterized by a zone of pathological tissue extending from the pith to the epidermis. In a number of infected seedlings, cambial function was restored and infected lesions were overgrown. Live mycelium was often maintained in cortical lesions and in some cases reinvaded healthy cortical cells. These latent-type infections resulted in the initiation of gall formation up to 1 year after initial resistance to infection occurred. Key words: tree improvement, western gall rust, pine stem rust.
A new Botryoascus from the air of a poultry farm
Authors: Martínez Angel T. , González Aldo E. , Abarca Lourdes , Cabanes Javier
Published: April 2011

A new endomycetaceous fungus, Botryoascus cladosporoides, is described. This species differs from the previously described Botryoascus synnaedendrus in conidial structures and physiological characteristics and occurs in a very different habitat. Key words: yeasts, endomycetes, taxonomy, aeromycology.
Changes in forest fire frequency in Kootenay National Park, Canadian Rockies
Authors: Masters Alan M.
Published: April 2011

Time-since-fire distribution analysis is used to estimate forest fire frequency for the 1400 km2 Kootenay National Park, British Columbia, located on the west slope of the Rocky Mountains. The time-since-fire distribution indicates three periods of different fire frequency: 1988 to 1928, 1928 to 1788, and before 1788. The fire cycle for the park was > 2700 years for 1988 to 1928, 130 years between 1928 and 1788, and 60 years between 1778 and 1508. Longer fire cycles after 1788 and 1928 may be due, respectively, to cool climate associated with the Little Ice Age and a recent period of higher precipitation. Contrary to some fire history investigations in the region, neither a fire suppression policy since park establishment in 1919, nor the completion of the Windermere Highway through the park in 1923 appear to have changed the fire frequency from levels during pre-European occupation. Spatial partitioning of the time-since-fire distribution was unsuccessful. No relationship was found between elevation or aspect and fire frequency. Key words: fire cycle, Rocky Mountains, climate change.
Structural aspects of the leaves of seven species of Portulaca growing in Hawaii
Authors: Kim InSun , Fisher David G.
Published: April 2011

Seven species of Portulaca growing in Hawaii can be divided into two groups based on the morphology, anatomy, and ultrastructure of their leaves. Portulaca oleracea, P. molokiniensis, P. lutea, forming group A, have spatulate to obovate leaves, paradermal minor veins, and mesophyll cells that completely encircle the minor veins. The chloroplasts in their bundle sheath cells are larger than those in the mesophyll cells and have well-developed grana and reduced peripheral reticulum. Bundle sheath mitochondria are larger and more numerous than those in the mesophyll, and chloroplasts in the mesophyll cells have well-developed grana and peripheral reticulum. Portulaca pilosa, P. villosa, P. sclerocarpa, and P. "ulupalakua," forming group B, have lanceolate to oblong–oblanceolate leaves, peripheral minor veins, and incomplete wreaths of mesophyll cells. The choroplasts in their bundle sheath cells are about the same size as those in the mesophyll and have reduced grana and well-developed peripheral reticulum. The bundle sheath mitochondria are about the same in size and number as those in the mesophyll, and the mesophyll chloroplasts have well-developed grana and reduced peripheral reticulum. Groups A and B may be equivalent, respectively, to types ii and i of R. C. Carolin, S. W. L. Jacobs, and M. Vesk (Aust. J. Bot. 26: 683–698, 1978) and to coronary subtypes B and A of E. V. Voznesenskaya and Y. V. Gamalei (Bot. Zh. Leningrad, 71: 1291–1306, 1986), which constitute groupings of Portulaca species studied by those authors.
Physiological properties of the entomopathogenic hyphomycete Paecilomyces farinosus in relation to its role in the forest ecosystem
Authors: Harney Sharon , Widden Paul
Published: April 2011

Fifty-four strains of the entomopathogenic fungus Paecilomyces farinosus, half of which had been isolated from balsam fir litter and half of which had been isolated from naturally infected spruce budworm larvae, were evaluated for their use of a number of complex carbohydrates and other carbon sources, to determine their potential saprophytic ability. The fungi were also tested for (i) their ability to grow on and to decompose balsam fir litter, and (ii) their ability to survive desiccation, which is likely to occur in the tree canopy. The fungi produced a wide range of enzymes, including cellulases, chitinases, and proteases. They also grew on and decomposed balsam fir litter. A discriminant analysis showed a tendency for the strains isolated from spruce budworm to grow better on gelatin, whereas those from the litter grew better on cellulose. We conclude that P. farinosus is a versatile saprophyte, capable of opportunistically parasitizing spruce budworm larvae. These characteristics could be important when considering P. farinosus as a possible agent of biological control. Key words: Paecilomyces farinosus, entomopathogen, spruce budworm, saprophytic ability, hydrolases.
Root architecture of warm- and cool-season grasses: relationship to mycorrhizal dependence
Authors: Hetrick B. A. D. , Wilson G. W. T. , Leslie J. F.
Published: April 2011

Root architecture of five warm-season and five cool-season grasses was compared. The cool-season grasses had significantly more primary and secondary roots than warm-season grasses, and the diameter of primary, secondary, and tertiary roots of cool-season grasses was significantly smaller than that of warm-season grasses. Soil microorganisms, mycorrhizae, and P fertilization did not affect root number or diameter of the cool-season grasses; root number of warm-season grasses did respond to mycorrhizae and P fertilization, but not soil microorganisms. Specific root length of cool-season grasses was not altered by mycorrhizae, soil microbes, or P fertilization, and was significantly greater than that of warm-season grasses, particularly those inoculated with mycorrhizae. Topological analysis of root architecture revealed that mycorrhizal symbiosis inhibited root branching in warm-season grasses but had no effect on rooting strategy of cool-season grasses. In contrast, P fertilization did not substantially alter root branching in warm- or cool-season grasses. Apparently, root architecture of the mycorrhizal-dependent warm-season grasses is quite plastic, allowing energy expenditure for root development to be conserved; the root architecture of the less mycorrhizal-dependent cool-season grasses appears to be fixed and does not alter to accommodate the symbiosis. Key words: topology, rooting strategy, C3, C4.
The effect of some commercial pesticide carrier formulations on the germination of Pseudoaegerita matsushimae propagules
Authors: Premdas Peter David , Kendrick Bryce
Published: April 2011

Propagules of Pseudoaegerita matsushimae, an aero-aquatic hyphomycetous fungus commonly occurring on the surface of woodland ponds, were shown to germinate readily on moist surfaces. After an initial latency period of approximately 3 h during which less than 5% germination occurred, the ensuing 2–3 h saw 97% of all propagules germinate. This figure did not increase after 16 and 24 h. Using this information as a control, germinability was tested in many situations that simulated the application of pesticides and also their carriers. Oil emulsions or emulsifiable oil concentrates containing surfactants were up to 30% more toxic than mineral oils which did not contain such additives. The surfactant itself (Tween 80) did not significantly inhibit germination. Our initial studies indicated that aromatic carriers such as xylene or turpentine are highly toxic to Pseudoaegerita matsushimae propagules, whereas aliphatic carriers such as kerosene produce no significant reduction of germination. Key words: aero-aquatic fungus, pesticide carriers, aliphatic hydrocarbons, aromatic hydrocarbons, environmental impact.
Lateral root initiation in Marsilea quadrifolia. I. Origin and histogenesis of lateral roots
Authors: Lin Bai-Ling , Raghavan V.
Published: April 2011

In Marsilea quadrifolia, lateral roots arise from modified single cells of the endodermis located opposite the protoxylem poles within the meristematic region of the parent root. The initial cell divides in four specific planes to establish a fivecelled lateral root primordium, with a tetrahedral apical cell in the centre and the oldest merophytes and the root cap along the sides. The cells of the merophyte divide in a precise pattern to give rise to the cells of the cortex, endodermis, pericycle, and vascular tissues of the emerging lateral root. Although the construction of the parent root is more complicated than that of lateral roots, patterns of cell division and tissue formation are similar in both types of roots, with the various tissues being arranged in similar positions in relation to the central axis. Vascular connection between the lateral root primordium and the parent root is derived from the pericycle cells lying between the former and the protoxylem members of the latter. It is proposed that the central axis of the root is not only a geometric centre, but also a physiological centre which determines the fate of the different cell types. Key words: lateral root initiation, Marsilea quadrifolia, root histogenesis.
Distribution of silicon in cucumber leaves during infection by powdery mildew fungus (Sphaerotheca fuliginea)
Authors: Samuels A. L. , Glass A. D. M. , Ehret D. L. , Menzies J. G.
Published: April 2011

The distribution of silicon in the leaf epidermis of cucumber (Cucumis sativus L.) grown in hydroponic nutrient solutions supplemented with soluble silicates was examined using scanning electron microscopy and energy dispersive x-ray analysis. Silicon was found primarily in cells surrounding the bases of the trichome hairs. During infection by Sphaerotheca fuliginea (Schlecht.:Fr.) Poll., areas of host cell wall adjacent to the germinating hyphae showed altered surface morphology and high concentrations of silicon. Measurements of total hyphal length per colony showed the fungal colonies grown on silicate-treated plants were significantly smaller than fungal colonies grown on control plants. In the early stages of infection, the presence of high silicon surrounding colonies was correlated with lower fungal growth. Key words: silicon, x-ray analysis, hydroponics, Cucumis sativus, Sphaerotheca fuliginea.
Dormancy patterns in buried seeds of Datura ferox and D. stramonium
Authors: Reisman-Berman O. , Kigel J. , Rubin B.
Published: April 2011

Seasonal changes in seed dormancy of Datura ferox L. and D. stramonium L. were studied during 2 years in seeds buried in the field and compared with changes in dormancy of dry-stored seeds. Dormancy levels were evaluated by measuring the germination of exhumed and dry-stored seeds under 32:27 °C (nondormant seeds) or 32:12 °C (relatively dormant seeds). Levels of relative or full dormancy did not change during 2 years of dry storage in either species. Seed burial at 20 cm accelerated after-ripening, and primary dormancy disappeared earlier than at 5 cm. However, burial depths greater than 10 cm prevented germination in situ. This inhibition was not due to smaller daily fluctuations of soil temperature with increasing depth, since seeds buried at 20 cm and kept at 32:12 °C also failed to germinate. Transferring seeds to shallower soil layers allowed their germination. Cyclic seasonal changes in dormancy were found in buried seeds of D. ferox but not in D. stramonium. In D. ferox, dormancy was alleviated during the winter and germinability was maximal in early spring; the increase in dormancy was preceded by high late spring – summer temperatures. In D. stramonium most seeds near the soil surface germinated in the field in a brief flush in early winter, at temperatures under which D. ferox did not germinate. Key words: Datura, germination, dormancy, buried seeds, temperature.
Identification of indigenous and introduced symbiotic fungi in ectomycorrhizae by amplification of nuclear and mitochondrial ribosomal DNA
Authors: Gardes Monique , White Thomas J. , Fortin J. André , Bruns Thomas D. , Taylor John W.
Published: April 2011

We used the polymerase chain reaction (PCR) to amplify specific regions of the nuclear and mitochondrial genomes of fungi using DNA extracted from pure cultures as well as that directly from ectomycorrhizal rootlets. The internal transcribed spacer (ITS) of the nuclear ribosomal repeat unit and a portion of the mitochondrial large subunit ribosomal RNA gene were chosen as target sequences because both exist in high copy number and amplification primers for both discriminate between plant and fungal DNAs. These features provided a sensitivity and specificity sufficient for detection and analysis of a single mycorrhizal rootlet. We evaluated the variations in the amplified products with regard to the length, restriction endonuclease sites, and primary sequence for use in identification of genera, species, and strains of ectomycorrhizal fungi, with particular attention to selected Laccaria species. Accidental contamination of jack pine seedlings by Telephora terrestris was easily recognized. Amplification and direct DNA sequencing of a portion of the ITS were done for three strains of L. bicolor, one of L. laccata, one of L. proximo, and one of T. terrestris. The nucleotide sequence variation was 32% between L. bicolor and T. terrestris, and it ranged from 3 to 5% among the three Laccaria species examined and from 1 to 2% within L. bicolor. The degree of variation observed is sufficient to allow the use of specific oligonucleotides to characterize amplified ITS products. To demonstrate the feasibility of this approach we designed and tested a probe that enabled two isolates of L. bicolor to be distinguished by a single base-pair difference in a filter-based hybridization assay. In combination these methods now provide an important set of tools for the study of mycorrhizal ecology. Key words: internal transcribed spacer, LrDNA gene, mycorrhizal ecology, polymerase chain reaction, rDNA.
Integration among ramets of Trifolium repens
Authors: Turkington Roy , Klein Elena
Published: April 2011

Cuttings of Trifolium repens were grown in pots without neighbours. When individual interconnected stolons from these cuttings were directed into adjacent pots so that daughter ramets were growing with different grass neighbours, these neighbouring grasses had dissimilar effects on leaf number, leaf size, percent branching of nodes, stolon length, and shoot dry weight. When the T. repens cuttings were grown in pots with neighbours, the effects of different grass neighbours on subsequent growth of stolons and ramets evened out. Key words: integration, clone, ramet, neighbour effects, Trifolium repens.
Patterns of leaf development in anisophyllous shoots
Authors: Dengler Nancy G.
Published: April 2011

Comparisons of the development of the dimorphic leaves of anisophyllous shoots can be used to understand how ontogenies might be modified during evolution to produce morphological change. In anisophyllous shoots, leaves of different sizes are borne on the dorsal and ventral sides of plagiotropic stems. Anisophylly is regarded as an adaptation for light interception in strongly shaded habitats since the small size of dorsal leaves and orientation of leaf blades minimizes self-shading. Anisophylly affects not only the patterns of leaf development, but also shoot symmetry, phyllotaxis, and bud development. Pronounced anisophylly is widely distributed throughout the land plants as a result of convergent evolution, possibly in response to similar selection pressures. In taxa where the expression of anisophylly is fixed, leaf primordium size and correlated characters, including the development of procambium, differ between dorsal and ventral sides of the shoot from the first plastochron. In contrast, patterns of dorsal and ventral leaf growth and correlated characteristics diverge late in development, often at the time leaves expand from the bud, in taxa where the expression of anisophylly is facultative. These observations indicate that changes in the timing of developmental events can account for many, but not all, of the ontogenetic alterations that result in divergent leaf size and shape on the same shoot and, by implication, accompany the evolution of new taxa. Key words: leaf development, anisophylly, heterochrony.
The role of floral development in studies of legume evolution
Authors: Tucker Shirley C.
Published: April 2011

Comparative floral development is useful to test hypotheses of phylogeny and taxonomic relationships among legumes because it provides a greater understanding of character states. It can reveal homologies, as in the cupule, an anomalous and varied structure among species of Psoralea that originates by fusion of two or more small bracts. Convergence is demonstrated by comparing differing developmental pathways of specialized floral features such as dorsiventral heterostameny, eccentric corolla, porate stamens, and enantiostyly, among species of Cassia, Senna, and Chamaecrista. Naturally occurring homeosis can be identified, as in the example of stamens developing from uncommitted primordia in petal sites in Saraca declinata. Floral development among species in a genus is generally very similar, with any differences usually occurring only terminally. In contrast, ontogenies among related genera show more differences, and those differences may be accelerated, appearing earlier in ontogeny than interspecific differences. Floral development in Ceratonia siliqua, in the same tribe as the Cassia group, diverges strongly from the latter, lacking petals and having a unique type of inception of stamens. Developmental evidence supports removing Ceratonia from Cassieae. Key words: development, evolution, flower, legumes, ontogeny, phylogeny.
Molecular evolutionary analyses of the small and large subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase
Authors: Pasternak J. J. , Glick B. R.
Published: April 2011

The molecular evolution of the amino acid sequences of the mature small and large subunits of ribulose-1,5-bisphosphate carboxylase/oxygense (Rubisco) was determined. The dataset for each subunit consisted of sequences from 39 different taxa of which 22 are represented with sequence information for both subunits. Phylogenetic trees were reconstructed using distance matrix, parsimony and simultaneous alignment and phylogeny methods. For the small subunit, the latter two methods produced similar trees that differed from the topology of the distance matrix tree. For the large subunit, each of the three tree-building methods yielded a distinct tree. Except for the distance matrix small subunit tree, the tree-building methods produced topologies for the small and large subunit sequences from the nonflowering plant taxa that, for the most part, agree with current taxonomic schemes. With the full datasets, the lack of consistency both among the various trees and with conventional taxonomic relationships was most evident with the Rubisco sequences from angiosperms. It is unlikely that current tree-building methods will be able to reconstruct an unambiguous molecular evolution of either of the Rubisco subunits. Molecular trees, regardless of methodology, showed similar topologies for the small and large subunits from the 22 taxa from which both subunits have been sequenced, indicating that the subunits have changed to the same extent over time. In this case, similar trees were formed because only 4 of the 22 taxa were from dicots. Key words: ribulose-1,5-bisphosphate carboxylase/oxygenase, amino acid sequence, molecular evolution, phyletic trees.