bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of secondary sporidial production by a wheat-bunt fungus, Tilletia caries
Authors: Churchill A. C. L. , Mills Dallice
Published: September 2008

The kinetics of secondary sporidial production was determined for each of two haploid strains of Tilletia caries in a defined liquid culture medium. Four distinct sporidial types were identified on the basis of developmental stages observed during culture. They were classified as follows: class I, ungerminated filiform and lunate sporidia; class II, germinated sporidia with an attached, emerging secondary sporidium; class III, germinated sporidia that produce hyphae; and class IV, senescent sporidia and cells with atypical morphology. The doubling time for the respective spore classes of one haploid strain was 17.7, 15.2, 13.1, and 15.8 h. The doubling time for presumptive viable sporidia (classes I–III) of this strain was 15.4 h, whereas in the other strain of the same mating type, it was 9.5 h. Each strain attained a cell density of approximately 5–7 × 107 viable spores per millilitre at stationary phase, and class-I sporidia were the predominant viable spore type present. The lunate and filiform sporidia contained a single nucleus as shown by iron hematoxylin and DAPI (4,6-diamidino-2-phenylindole) nuclear stains.
Some sporocarpic Endogonaceae from eastern Canada
Authors: Berch Shannon M. , Fortin J. André
Published: September 2008

The known geographic distributions of Endogone pisiformis, Endogone incrassata, Endogone lactiflua, Glomus macro-carpum, Glomus radiatum, and Glomus vesiculifer (Endogonaceae) are extended into the northwest of mainland Canada. Descriptions and observations of taxonomic and ecological features of these collections are provided. Morphologically, these six fungi resemble collections reported from elsewhere in North America. Azygospores are reported, for the first time in the genus, for Endogone pisiformis.
Hyperparasitism of Puccinia violae by Cladosporium uredinicola
Authors: Traquair J. A. , Meloche R. B. , Jarvis W. R. , Baker K. W.
Published: September 2008

Cladosporium uredinicola Speg. is a necrotrophic hyperparasite of the rust fungus Puccinia violae (Schum.) DC on Viola odorata L. Its hyphae penetrate urediniospores directly, but coagulation and disintegration of rust cytoplasm may occur prior to penetration. Only slight swelling of the infecting hyphal tip occurs, and penetration tubes and intracellular hyphae of C. uredinicola were seen in urediniospores.
Néoformation de bourgeons adventifs sur des portions de bourgeons végétatifs de Picea pungens cv. Foliis aureis cultivées in vitro
Authors: Chrétien Louise , Vieth Joachim
Published: September 2008

Portions of vegetative buds of Picea pungens were inoculated on an agar medium containing the following growth substances: 2,4-dichlorophenoxyacetic acid (2,4-D), 2-isopentenyladenine (2ip), and 2,3,5,-triiodobenzoic acid (TIBA). Bud neoformation and their subsequent development into shoots were obtained after 6 and 12 weeks of culture.
Seasonal response of ponderosa pine to inoculation of the mycangial fungi from the western pine beetle
Authors: Paine T. D.
Published: September 2008

The hypersensitive response obtained by inoculating the two mycangial fungi of the western pine beetle, Dendroctonus brevicomis LeC, and the blue-stain fungus, Ceratocystis minor Hedge, into ponderosa pine was measured during three different seasons in the same 12-month period. The lesions were produced faster and were significantly longer in the fall than in the summer. Similarly, lesions were longer and were produced faster when inoculations made in the summer were compared with spring inoculations. However, the response to a nonpathogenic fungus, a Penicillium sp., was not different from the response to mycangial fungi, suggesting that lesion production is a generalized response to infection that isolates fungus-colonized tissue from the rest of the tree. Ethanol extracts of hypersensitive-response lesions produced during the spring did not reduce growth of the mycangial fungi or C. minor when bioassayed at concentrations similar to those found in host tissue. This is different from other bark beetle–host tree systems that have been investigated.
Patterns of initial saprophytic fungal colonization of grass roots from two severely disturbed soils
Authors: Zak John C. , Parkinson Dennis
Published: September 2008

Development of the root-surface fungal assemblages of Agropyron trachycaulum grown on amended oil-sands tailings and a subalpine coal-mine spoil from Alberta (Canada) was followed over one growing season. Fungi were isolated, using a root-washing procedure, from the region of main seminal and nodal roots 4 cm from the root–hypocotyl axis. Fungal colonization of the root surfaces was rapid, with equilibrium numbers of species reached 2 weeks after plant emergence. Although the application of either fertilizer, peat, or sewage sludge to these spoils had no effect on the general form of the colonization curve, peat amendation did result in significantly higher numbers of species on the root surfaces. Species turnover within all assemblages was high throughout the growing season. The amount of species replacement ranged from a low of 67% to a high of 91% between consecutive 4-week sampling periods. Thus, although the number of species was relatively constant, species composition changed considerably. The structure of the root-surface fungal assemblages was characterized by a large proportion of rare species. The species abundance distributions were essentially negative exponential. Neither time nor amendation had any significant effect on these distributions. The large incidence of rare species within the assemblages suggests that these root surfaces represent nonequilibrium systems with respect to species occurrences.
Microsporogenesis in genic male-sterile lines of barley (Hordeum vulgare)
Authors: Herd Y. R. , Steer M. W.
Published: September 2008

Pollen development has been studied by various microscopical techniques in five genic male-sterile lines and in male-fertile lines of barley (Hordeum vulgare L.). Two of the male-sterile lines (msg,,ho and msg,,fz) exhibited apparently identical abnormalities: defective cytokinesis at the end of meiosis 1. Another male-sterile gene (msg,,fg) also appeared to cause defects at this stage; in this case nuclear restitution was incomplete. In the male-sterile line msg,,gf a failure of the periclinal division of the inner secondary parietal layer occurred, so that a tapetal layer was not formed. Development was normal through meiosis in anthers from msg,,fp plants until the early vacuolated microspore stage when normal sporopollenin production was inhibited.
Quantitative and qualitative comparison of root exudates of mycorrhizal and nonmycorrhizal plant species
Authors: Schwab Suzanne M. , Leonard Robert T. , Menge John A.
Published: September 2008

At 6 weeks after seed germination, the rate of leakage of carbohydrates and amino acids from roots was significantly higher in three plant species (Sorghum vulgare Pers., Lycopersicon esculentum Mill., and Citrus aurantium L.) that normally form vesicular–arbuscular mycorrhizae (VAM) than in three species (Chenopodium quinona Willd., Phytolacca americana L., and Saponaria vaccaria L.) that do not form VAM. There were no sugars, amino acids, or carboxylic acids that were consistently detected in root exudates of VAM-forming species that were also consistently absent from the exudates of non-VAM species. Although rates of root exudation over long time periods were lower in non-VAM species, at early stages of seedling establishment, the rate of exudation was greater in roots of Chenopodium quinona than in roots of Citrus aurantium. These results suggest that the overall rate of exudation may be an important factor in maintaining VAM in most plant species, but no specific compound could be identified as promoting VAM formation.
Cytological observations of early infection process by Fusarium oxysporum f. sp. radicis-lycopersici in tomato plants
Authors: Charest Pierre Mathieu , Ouellette G. B. , Pauzé F. J.
Published: September 2008

A survey of the initial infection phases of Fusarium oxysporum Schlecht. f. sp. radicis-lycopersici Jarvis and Shoemaker in tomato roots demonstrated that the epidermis was colonized from 12 to 24 h after inoculation. Until 96 h the pathogen was usually limited to the outer cortical area, where fungal cells were found to be either intercellular or intracellular. Host cell wall thickenings and papilla formation were noticeable in the cortical cells but totally absent in the endodermis and the vascular stele. In the cortical area, cytoplasm and walls of affected host cells were mostly disintegrated when the whole root tissues were colonized about 144 h after inoculation. Between 96 and 120 h, hyphae were visible in the endodermis, and 24 h later the vascular stele was colonized. In the latter area, parenchyma cells generally reacted as in the inner cortical area and invasion of vessels proceeded directly through middle lamella and pit membranes. When colonized, vessels contained fibrillogranular material interspersed with bubbles and an osmiophilic coating material. This coating material lined the vessel secondary wall and pit cavities and appeared thicker in the more occluded vessels. The possible implications of these observations on symptoms expression in this and similar plant diseases are discussed.
Zygopolaris borealis, a new gut fungus (Trichomycetes) living in aquatic mayfly larvae
Authors: Lichtwardt R. W. , Williams M. C.
Published: September 2008

A new species of Harpellales, Zygopolaris borealis, is described from the hindgut of larval Ephemeroptera of the family Heptaginiidae. It is morphologically distinct from the type species, Z. ephemeridarum, which lives in Baetidae and Ephemerellidae. In addition to comparing the two fungi, new observations on the type species are recorded.
Water loss from the developing caryopsis of wheat (Triticum aestivum)
Authors: Lee D. R. , Atkey P. T.
Published: September 2008

The measured rate of water loss from a developing wheat grain would accommodate a unidirectional flux of water associated with the translocation stream into and through the caryopsis. The few stomata located within the crease of the grain could potentially contribute to approximately 18% of the measured rate of water loss. The maximum value of the cuticular resistivity of the grain is a relatively low 40 s∙cm−1.
Four new Mallomonas species of the Torquatae series (Chrysophyceae)
Authors: Nicholls K. H.
Published: September 2008

Four new species of Mallomonas (Chrysophyceae), Mallomonas scrobiculata sp. nov., Mallomonas serrata sp. nov., Mallomonas labrinthina sp. nov., and Mallomonas favosa sp. nov., are described from transmission electron microscopy of silica-scale structure of specimens from lakes and ponds in Ontario, Canada. All four are of the Torquatae series (characterized by the uniquely shaped anterior collar scales with attached bristles and rhomboidal body scales lacking bristles) and are distinguished from others in the series (e.g., M. mangofera Harris & Bradley, M. alveolata Dürrschmidt, and M. pumilio H. & B. em. Asm. Cronb. & Dürrs.) by the distinctive (and constant) structure and ornamentation of their scales.
Graviresponsiveness and cap dimensions of primary and secondary roots of Ricinus communis (Euphorbiaceae)
Authors: Moore Randy , Pasieniuk John
Published: September 2008

After branching from the primary root, secondary roots of castor bean (Ricinus communis) grow laterally for 15–20 mm, after which they bend downward (i.e., become positively gravitropic). During the first 10 mm of growth, the lengths of caps of secondary roots increase from 120 ± 26 to 220 ± 28 μm. Although this increase is statistically significant (P < 0.1%), the resulting secondary roots are only minimally graviresponsive. A subsequent doubling of the lengths and widths of the root caps (i.e., to 420 ± 34 and 450 ± 41 μm, respectively) is positively correlated with the onset of gravicurvature. The graviresponsiveness and dimensions of caps of positively gravitropic secondary roots are not significantly different from those of positively gravitropic primary roots. These results indicate that (i) a statistically significant increase in the length and length:width ratio of a root cap does not necessarily result in the root becoming positively gravitropic, (ii) there may be a minimum cap length and (or) width necessary for graviresponsiveness, and (iii) the degree of graviresponsiveness exhibited by a particular root may be related to the size of its root cap.
Effects of caffeine treatment alone and in combination with gamma exposure on cultured peanut cells
Authors: Inoue M. , Huystee R. B. van
Published: September 2008

Cell growth, mitotic index, and peroxidase activity were measured, and radioimmunoassay with [35S]methionine for peroxidase synthesis was carried out on peanut suspension cells treated with 10−5 M caffeine with or without 50 kR gamma exposure. Decreases in the amount of peroxidase in the medium from caffeine treatment were thought to be induced by events causing simultaneous mitotic reduction and degradation of peroxidase by gamma exposure. However, the data based on a comparison of the rate of total protein and of peroxidase synthesis suggest that caffeine treatment induces quantitative and qualitative changes in the rate of peroxidase synthesis. The data on qualitative differences were obtained from peroxidase extraction without or with high ionic strength buffer.
Shoot ontogeny in Arctostaphylos uva-ursi (bearberry): the annual cycle of apical activity
Authors: Remphrey W. R. , Steeves T. A.
Published: September 2008

Phenological investigation of shoot ontogeny in the prostrate shrub Arctostaphylos uva-ursi (L.) Spreng. (bearberry) at two sites in Saskatchewan, Canada, revealed that most growth occurred from May to July. Vegetative bud swell and leaf primordium initiation began around the 1st of May. Following bud burst in late May, elongation of most shoots continued for 3 to 5 weeks. Most bearberry shoots were not completely preformed; that is, several neoformed foliage leaves were initiated during current-year shoot extension in addition to the leaves that had been preformed during the previous season and had overwintered in the bud. In many shoots, a terminal inflorescence was initiated in the latter part of May of the year prior to anthesis. During conversion to the flowering state, the terminal apex initiated seven to nine floral bracts, each subtending a bud. In vegetative terminal shoots, bud-scale initiation also began in mid-May to late May and new terminal buds were first evident in early to mid-June. Following the initiation of bud scales and transitional leaves, the production of preformed foliage-leaf primordia continued until about August 1. Protruding lateral buds were evident histologically in the axils of preformed leaves during the initial stages of bud swell. On long, dominant shoots numerous neoformed leaves were initiated and shoot extension was often prolonged well into August. Second-flush terminal and lateral shoots, which resulted from the expansion of neoformed leaves and internodes, were also observed. The occurrence of neoformed growth in a large proportion of shoots suggests an exploitive, opportunistic growth strategy in this species.
β-1,3-Glucanase and the spread of tobacco mosaic virus in Nicotiana and Phaseolus
Authors: Kearney C. M. , Wu J. H.
Published: September 2008

The β-1,3-glucan callose is thought to form a seal which surrounds viral local lesions and prevents viral spread in many plant hosts. Therefore, we investigated the role of host β-1,3-glucanase in facilitating viral spread. The following were compared for lesion size (indicating viral spread rate) and β-1,3-glucanase activity: (i) inoculated excised leaves of Phaseolus vulgaris L. cv. Pinto supplied with sugar (small lesions) or deprived of sugar (large lesions); (ii) Nicotiana glutinosa L. infected with the VM strain (small lesions) or the U1 strain (large lesions) of tobacco mosaic virus; and (iii) Nicotiana sylvestris Spegaz. infected with the VM strain (small lesions) or the U2 strain (large lesions) of tobacco mosaic virus. In all cases, the larger, more rapidly spreading viral lesions did not have significantly higher levels of β-1,3-glucanase activity than the corresponding smaller lesions. Nicotiana sylvestris leaves with a systemic viral infection had a β-1,3-glucanase activity lower than that of leaves with local lesions. Finally, β-1,3-glucanase activity was stimulated to the same extent by a slowly developing abiotic necrosis as by local lesions of tobacco mosaic virus, β-1,3-Glucanase activity may therefore increase during localized viral infection as a result of the wounding associated with necrotic viral lesions.
Vegetative development of Uromyces appendiculatus var. appendiculatus in Phaseolus vulgaris
Authors: Gold R. E. , Mendgen K.
Published: September 2008

The morphology of intercellular and intracellular hyphae derived from basidiospores of Uromyces appendiculatus var. appendiculatus is described. Light and electron microscopic observations of the bean rust fungus were made on susceptible leaves of Phaseolus vulgaris from 3 to 10 days after inoculation. Following egress from invaded epidermal and palisade parenchyma cells, the fungus grew rapidly and developed extensive intercellular mycelium. An amorphous to fibrillar extracellular matrix was deposited between fungal and host cell walls. Intercellular hyphae grew closely appressed to the mesophyll cells and penetrated them to form intracellular hyphae from either a terminal or nonterminal mother cell. Intracellular hyphae were fingerlike, sometimes septate, and generally remained terminal in the invaded mesophyll cell. Occasionally the fungus exited the cell to become an intercellular hypha or an intracellular hypha in an adjacent host cell. The plant rarely exhibited a resistantlike reaction at sites of penetration into mesophyll cells.
Ultrastructural studies on conidiomata, conidiophores, and conidiogenous cells in six lichen-forming Ascomycetes
Authors: Honegger Rosmarie
Published: September 2008

The conidiomata, conidiophores, and conidia of six lichen-forming Ascomycetes were investigated using the scanning electron microscope, and conidium development in two of these species was studied by transmission electron microscopy. Phialidic (micro) conidium formation was observed in the mycobiont of Parmelia tiliacea, Physconia pulverulacea, and Cladonia furcata (Lecanorales), in Lobaria laetevirens (Peltigerales), and in Caloplaca aurantia (Teloschistales). Annellations, first described by Vobis on the basis of light and transmission electron microscope investigations, were also found in scanning electron microscope preparations of macroconidia bearing conidiogenous cells of Lecanactis abietina (Opegraphales). Ultrastructural and developmental studies on conidiophore structure and conidium formation may be of interest for taxonomic and evolutionary considerations in lichen-forming fungi.
Further observations on the growth of flax rust fungus in axenic culture
Authors: Boasson Rosalinda , Shaw Michael
Published: September 2008

Axenic cultures of flax rust (Melampsora lini (Ehrenb.) Lév.) grown from sterile uredospores on a defined liquid medium in 125-mL Erlenmeyer flasks exhibited an incubation period of 12 to 20 days followed by a period of rapid growth and sporulation. A heat shock (31–33 °C for 2–2.5 h) administered 3 h after seeding the medium did not induce the formation of infection structures, but doubled the number of vegetative colonies initiated and increased total growth per flask (protein/flask) in 4 weeks by 20-fold. The optimum timing of the heat shock corresponded closely with the maximum rate of germ tube emergence. Ambient CO2 was not essential for germination or perception of the heat shock, but was essential, during the first half of the incubation period, for the subsequent development of vegetative colonies. CO2 fixation occurred at all stages of growth from 1 day onward, 14CO2 being incorporated into ethanol-insoluble and ethanol-soluble fractions, including amino acids. Growth rate following the incubation period was not affected by the initial pH of the medium between 5.0 and 6.0, but the incubation period was shorter at pH 6.0.
A polyethylene glycol based medium for in vitro germination of cashew pollen
Authors: Subbaiah C. C.
Published: September 2008

A medium, comprising polyethylene glycol 4000, sucrose, boron, and calcium, for in vitro germination of pollen in cashew (Anacardium occidentale L.) gave 90–95% germination as well as excellent pollen tubes comparable with those found in vivo. The better performance of this combination compared with media containing only sucrose and inorganic elements is discussed in relation to the superiority of polyethylene glycol to sucrose as an osmoticum.
Interférence du chénopode blanc (Chenopodium album), chez l'avoine et la luzerne : seuils de nuisibilité
Authors: Lapointe Anne-Marie , Deschênes Jean-Marc , Gervais Paul , Lemieux Claudel
Published: September 2008

The competitive threshold of Iamb's-quarters (Chenopodium album L.) in alfalfa and oats was studied in the greenhouse and in the field. In oats, the competitive threshold of Iamb's-quarters was reached at a density of 1000 plants/m2 in the field. In the greenhouse, the weed could not compete with oats when both were sown simultaneously. When Iamb's-quarters was sown 15 days earlier than oats, crop yields were significanty reduced under a density of 800 plants/m2. The competitive threshold of Iamb's-quarters in alfalfa was reached at a density of 200 plants/m2 in the greenhouse and 1000 plants/m2 in the field. The difference between the results of the two experiments was mainly caused by the growth conditions (soil type, fertility, humidity) which were quite different and influenced both the weed and the crop. Two harvest treatments were compared and it seems preferable to take the first cut of alfalfa at the 10% bloom stage rather than at the vegetative stage. A cut taken at the vegetative stage had a negative effect on alfalfa. This effect did not seem related to the weed but rather to a weakening of the legume. A close relationship existed between the number of individuals per square metre and the biomass of Iamb's-quarters, on one hand, and the yield of alfalfa or oats, on the other hand. The classes of Iamb's-quarters with the largest densities, or the highest biomass, were the most competitive.
Localisation structurale et ultrastructurale d'activités peroxydasiques dans les parois du mésophylle et des fibres en cours de lignification chez l'alfa (Stipa tenacissima)
Authors: Harche M.
Published: September 2008

Using diaminobenzidine as substrate, peroxidase activity was localized in the walls of parenchyma cells and differentiating fibres. In mature fibres and parenchyma a slight activity could be recognized in primary walls only. In parenchyma cells, peroxidase activity was fairly inhibited with heat, potassium cyanide, and aminotriazole, which could indicate the presence of catalase within the cell walls. However, in plasmodesmatal regions peroxidases were- resistant to the above inhibitors. Syringaldazine oxidase activity was present only in the primary wall and the outer part of the secondary wall of differentiating fibres. The parallelism between lignification and peroxidase activity in the secondary walls supports the hypothesis of the involvement of these enzymes in the lignification process.
Initiation and development of cankers caused by virulent and cytoplasmic hypovirulent isolates of the chestnut blight fungus
Authors: Russin J. S. , Shain L.
Published: September 2008

Stems of American chestnut were inoculated with a virulent (V) isolate of Endothia parasitica alone or containing different agents for cytoplasmic hypovirulence (CH). The V isolate (EP 155) initiated cankers in cork borer wounds 0,1,2,4,7,14,21, or 28 days old. Infection of this V isolate with CH agents Hl2 (EP 780), HMU (EP 868) or HT2 (EP 905), restricted canker development to wounds 0–7 days old, Odays old, or to none of the wounds 0–28 days old, respectively. Inoculation of several wound types with V or CH conidia collected from cankers or agar cultures resulted in few cankers. Measurement of electrical resistance (ER) of bark at different heights along chestnut stems indicated that ER was lowest at stem bases. Cankers initiated artificially at stem bases with mycelium from V or CH isolates were smaller and enlarged more slowly than did cankers initiated at more elevated stem positions. Areas of cankers initiated in detached chestnut stems in which moisture contents were regulated were inversely related to moisture content and directly related to ER of chestnut bark.
Taxonomic studies in wall barley (Hordeum murinum sensu lato) and sea barley (Hordeum marinum sensu lato). 2. Multivariate morphometrics
Authors: Baum Bernard R. , Bailey L. Grant
Published: September 2008

The demarcation of the Old World species in Hordeum L. section Hordeastrum Doell. has been the subject of considerable controversy. The present paper reports the results of a morphometric analysis of the wall and sea barleys (H. murinum L., H. marinum Huds., and their allies). A sample of 227 accessions was scored for 39 characters, and the resulting data matrix was divided into three groups on the basis of lodicules and cpiblast characters. These three groups were then subjected to several aspects of discriminant analysis (stepwise discriminant analysis, linear discriminant analysis, canonical analysis of discriminance, and nearest neighbor discriminant analysis) both on untransformed and log-transformed data. The results indicate that the wall and sea barleys consist of five distinct groups worthy of morphological specific rank. These correspond to H. marinum sensu stricto, H. geniculatum All., H. glaucum Steudel. H. murinum sensu stricto, and H. leporinum Link. Ranges for 37 characters within these five taxa are presented. A key to the five species and one hybrid (reported in the first paper of this series) is supplied. Our conclusions are discussed in the context of various taxonomic treatments of the group.
Boundary-zone formation in peach bark in response to wounds and Cytospora leucostoma infection
Authors: Biggs A. R.
Published: September 2008

Seedlings of peach (Prunus persica (L.) Batsch cv. Halford) were mechanically wounded or inoculated with mycelium of Cytospora leucostoma (Pers.) Fr. Bark samples for histological study were taken from margins of visibly affected areas at varying times after treatment. Histological examination revealed that host responses to wounding and pathogen colonization were basically similar, differing only in timing and extent of responses examined. Nonspecific host responses included gum production, changes in cell wall polysaccharides, cell wall lignification, and formation of suberized impervious tissues as part of the process of necrophylactic periderm formation. The presence of the fungus was associated with inhibited differentiation of living tissues; and, as a result, host processes responsible for impervious tissue and necrophylactic periderm formation were affected adversely.
Reduction in growth of hybrid poplar following field exposure to low levels of O3 and (or) SO2
Authors: Reich Peter B. , Lassoie James P. , Amundson Robert G.
Published: September 2008

A field fumigation system was modified from one described elsewhere, and used to expose unenclosed hybrid poplar plants (Populus deltoides × trichocarpa) to low levels of O3 and (or) SO2. A 3 × 3 factorial design was employed, allowing for analysis of individual effects and potential interactions between the two pollutants. Two experiments were conducted during the summer of 1980. During the experiments, levels of ambient SO2 and O3 were near zero (<0.01 ppm) and low (mean, 0.04 ppm), respectively. Pollutant treatments included exposure to ambient air or to ambient air plus additional O3 and SO2 for 5–6 h/day. Fumigations with O3 and SO2 were made on 17 of 27 (first experiment) and 13 of 20 (second experiment) days, respectively. Exposure to two greater than ambient levels of O3 (mean concentrations, 0.06 or 0.08 ppm) and (or) SO2 (mean concentrations, 0.06 or 0.11 ppm) resulted in reductions in growth, dry matter accumulation, and leaf longevity. No significant interactions between the pollutants were observed and O3 had approximately a three times greater negative effect than SO2 on either a concentration or dose basis. All significant pollutant effects were linear with respect to total dose or average exposure concentration. The negative impact of low doses of O3 suggests a need for concern, since low level O3 pollution is chronic during the growing season in much of eastern North America.
An action spectrum for photoinhibition of conidium formation in the fungus Alternaria solani
Authors: Honda Yuichi , Nemoto Masayasu
Published: September 2008

An action spectrum for photoinhibition of conidium formation in Altemaria solani (Ellis et G. Martin) Sorauer was determined by exposing colonies to monochromatic radiation between 232 and 722 nm. Following photoinduction of conidiophores by near-ultraviolet radiation, inhibitory exposures were made 5–7 h into the dark period, using monochromatic radiation. Radiation longer than 530 nm was not effective for inhibiting conidium formation. The action spectrum has maxima at 480, 455, and 435 nm in the visible region, 381 nm in the near-ultraviolet region, and 273 nm in the far-ultraviolet region. The action spectrum is divided into three parts by two troughs at 303–316 nm and 396–415 nm. These characteristics of the action spectrum indicate that the photoinhibition of conidium formation is a typical blue photoresponse with an increased activity in the far-ultraviolet region.
Response of Phaseolus vulgaris protoplasts to chemical components of fungal origin
Authors: Griffiths Helen M. , Anderson Anne J.
Published: September 2008

Colletotrichum lindemuthianum is the causal agent of anthracnose in Phaseolus vulgaris L. (French bean). The α and β races of the fungus were used in this study with French bean cultivar ‘Great Northern’. Whole plants inoculated with the α race developed brown lesions on the hypocotyls (susceptible response). The β race caused small limited lesions, indicating a more resistant interaction. Extracellular products and cell wall materials were isolated from β race cultures and extracellular products from α race cultures. The extracts were size fractionated. By using a cotyledon bioassay, elicitor activity was demonstrated on ‘Dark Red Kidney’ within fractions from the α race. Fractions from the β race had little activity on ‘Dark Red Kidney’ or ‘Great Northern’ cotyledons. Protoplasts were isolated from ‘Great Northern’ bean hypocotyl tissue and incubated with the fungal fractions. Even at low concentrations (0.01 μg glucose equivalent∙mL−1), the β race culture filtrate rapidly killed a greater percentage of protoplasts (30%) than the α race (15%). The β race wall extract had little effect upon protoplast viability. The proportion of nonviable protoplasts depended on the incubation period and the concentration of the fungal material. Heat treatment of the culture filtrates and wall extract did not decrease their lethal effects. The results suggest that protoplasts may be valuable in examining the nature of certain plant–pathogen interactions.
Species-specific responses to water stress of gas exchange parameters mimicked by applied abscisic acid
Authors: Bunce James A.
Published: September 2008

Net photosynthetic rates and leaf conductances to water vapor were measured in Abutilon theophrasti, Amaranthus hypochondriacus, and Glycine max after injecting abscisic acid into petioles of attached leaves. Changes in substomatal carbon dioxide partial pressure were measured in air in each species for various degrees of inhibition of the photosynthetic rate. Changes in the initial slope of photosynthesis versus substomatal carbon dioxide partial pressure were also characterised in two of the species. Responses to abscisic acid were compared with responses to water stress. Abscisic acid reduced photosynthetic rate and conductance in air in proportion to the amount applied. In no case was the relative decrease in substomatal carbon dioxide partial pressure as large as the relative decrease in photosynthesis. This indicated that nonstomatal inhibition of photosynthesis occurred. The changes in substomatal carbon dioxide partial pressure as photosynthesis was progressively inhibited and the changes in initial slope of photosynthesis versus substomatal carbon dioxide partial pressure were distinct for each species and were the same for abscisic acid and for water stress. The data strongly suggest that the reductions of both photosynthetic capacity and conductance by water stress are mediated by abscisic acid in these species.
Isolement et culture de protoplastes à partir de petioles et de tiges de deux variétés de patate douce (Ipomoea batatas)
Authors: Sihachakr Darasinh , Ducreux Georges
Published: September 2008

Protoplasts isolated from petioles and stems of two varieties of sweet potato showed high plating efficiency, and rhizogenic calli were obtained. The yield of protoplasts and the rate of survival of cell division were statistically analysed. Results are discussed in relation to the identification of different protoplast subpopulations and their histological origin.
Comparison of isolates in the Chaetomium aureum species group by esterase isoenzyme analysis
Authors: Szécsi Á. , Tóth S.
Published: September 2008

Soluble protein extracts from 19 isolates of Chaetomium were subjected to isoelectric focusing in polyacrylamide gel rods. The isoelectric point (pI) values of esterase isoenzymes were determined and the data used to calculate coefficients of similarity. Isolates of C. aureum and C. trilaterale were electrophoretically distinct, whereas isolates of C. confusum, C. humicola, C. rubrogenum, and C. trilaterale were not distinguishable electrophoretically from each other. The profiles A, B, F, and G can be used to distinguish the species of C. atrobrunneum, C. aureum, C. cupreum and C. fusiforme. These results partly agreed with the morphologically based classification of the C. aureum species group. Certain esterase bands were found to be useful as diagnostic markers for differentiating Chaetomium species.
Organogénèse de la fleur de Symplocarpus foetidus (Araceae)
Authors: Barabé Denis , Forget Suzanne , Chrétien Louise
Published: September 2008

The flowering cycle of Symplocarpus foetidus in volves 2 years. During the 1st year, the different flower parts are formed. The spadix, spherical at the beginning, elongates gradually to an ovoid–cylindrical shape. The flower primordia take a quadrangular shape when the four perianth parts and stamens are beginning to differentiate. In the first stages of its growth, the developing ovary is in a superior position. At the end of its growth, as a result of the type of development of the flower of Symplocarpus, it becomes completely inferior. Generally, at the end of the 1st year of the flowering cycle, the gynoecium consists of a small protuberance at the top of the unilocular ovarian cavity. During the 2nd year, the ovary closes and penetrates into the axis, the style forms, and the unique suborthotropic ovule develops. Our study of the flower's organogenesis shows that the inferior position of the ovary does not result from an invagination of the aerenchyma of the inflorescence axis although the ovary is completely enclosed in the axis of the inflorescence at maturity. The analysis of serial sections shows that the tissue of the flower originates from an organogenic zone distinct from the aerenchyma of the inflorescence axis. Symplocarpus is the only Araceae to possess an inferior ovary. The authors consider this genus to be an advanced genus in this family.
The biosystematics of Arnica fulgens and A. sororia (Asteraceae)
Authors: Downie Stephen R. , Denford Keith E.
Published: September 2008

Arnica fulgens Pursh and A. sororia Greene are sympatric throughout most of their ranges in northwestern United States and adjacent southwestern Canada. These taxa were previously recognized as two morphologically overlapping varieties or not very well separated species. A study of their floral and vegetative morphology, using TAXMAP cluster analyses, foliar flavonoid chemistry, reproductive biology, and ecology indicates that they are distinct species. Studies of reproductive behaviour reveal them to be amphimictic (2n = 38) and self-incompatible. Artificial hybridization experiments between the two species were unsuccessful.
Localization of cadmium in granules within differentiating and mature root cells
Authors: Rauser W. E. , Ackerley C. A.
Published: September 2008

Cadmium was found in electron-dense granules inside root parenchyma cells of Agrostis gigantea Roth and of Zea mays L. (maize) exposed to 3 mmol m−3 CdSO4. Cadmium-bearing granules were found in the cytoplasm and vacuoles of differentiating and mature cells and in nuclei of undifferentiated cells. Cadmium-bearing granules were absent from cell walls and epidermal cells. In addition to Cd, the electron-dense granules contained variable proportions of Ca, Fe, Ni, P, Pb, and Zn.
Cytotaxonomic studies on Polygonum section Polygonum in eastern Canada and the adjacent United States
Authors: Wolf Steven J. , McNeill J.
Published: September 2008

A total of 183 chromosome counts on plants representing nine species of Polygonum section Polygonum in eastern Canada and the United States is presented. Documented counts are published here for the first time for P. franktonii (2n = 60) and P. neglectum (2n = 40 and 60). In addition, previously unreported counts for P. achoreum (2n = 60), P. aviculare (2n = 40), and P. fowled (2n = 60) are presented. A review of previously published counts and an examination of voucher specimens have revealed a number of errors, negating many reported counts, including all of those for P. erectum and most of those for P. buxiforme. Polygonum arenastrum and P. raii are entirely tetraploid (2n = 40) and P. franktonii and P. ramosissimum entirely hexaploid (2n = 60), whereas the remaining species have both tetraploid and hexaploid elements. In contrast to previous reports, no diploid or octoploid plants have been detected.
The effect of short-term aphid feeding on the partitioning of 14CO2 photoassimilate in three legume species
Authors: Hawkins C. D. B. , Whitecross M. I. , Aston M. J.
Published: September 2008

The short-term effects of the feeding of cowpea aphids (Aphis craccivora Koch) and pea aphids (Acyrthosiphon pisum (Harris)), both Homoptera: Aphididae, on 14C translocation and plant growth of broadbean (Vicia faba L. cv. Aquadulce), cowpea (Vigna unguiculata (L.) Walp. cv. Caloona), and garden pea (Pisum sativum L. cv. Victory Freezer) seedlings were investigated, but not all plant–aphid combinations were utilized. Within 10 days of infestation, aphid feeding reduced the flux of translocate to the roots, changed the assimilate partitioning pattern in affected shoots, and apparently induced assimilate sources to become assimilate sinks. Cowpea aphid feeding also caused more lateral branches to be formed in broadbean. Some of these effects may be related to the imbibing of translocate by aphids, while other effects may result from a series of interactions involving substances in the saliva of aphids, plant hormones, and the assimilate ratio of sources–sinks. The amount of radioactivity found per unit weight of aphid tissue increased between days 5 and 10 in all four plant–aphid combinations. This may indicate that the nymphs were incapable of feeding on the larger phloem elements. Except for the decreased rate of translocation to the roots, the effect of aphid feeding on translocation is plant–aphid species specific.
Long-term regeneration dynamics and successional trends in a northern Swedish coniferous forest stand
Authors: Steijlen Ingeborg , Zackrisson Olle
Published: September 2008

The natural age and stand structure of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and birch (Betula pubescens Ehrh.) was studied in a virgin forest stand in northern Sweden. The stand has been unaffected by fire during the past 500 years. It is suggested that the variations in age structure and invasion pattern are the result of low-frequency climatic fluctuations influencing seed production, germination, and early survival of seedlings. The periods of climatic amelioration that occurred during the 1870s and during this century have been especially favourable to pine, resulting in a pine-dominated regeneration underneath a tree layer where spruce and birch are the most abundant species. This is contrary to generally accepted theories concerning postfire successional trends in this part of the boreal zone. It is concluded that small gap-phase replacement of trees by climatically induced regeneration and mortality events probably is the reason for the general weak correlation between age and size of trees. It is also concluded that this postfire succession will not lead to a total spruce dominance during a continuous succession under prevailing climate regimes.
Intraspecific and interspecific growth variation of ectomycorrhizal fungi at different temperatures
Authors: Cline Michael L. , France Raymond C. , Reid C. P. Patrick
Published: September 2008

Geographically distinct isolates of the ectomycorrhizal fungi Pisolithus tinctorius, Cenococcum geophilum, Thelephora terrestris, and Suillus granulatus showed definite temperature optima for growth in pure culture. Temperatures promoting the greatest fungal growth varied interspecifically and intraspecifically over the temperature treatments of 16, 21, 27, 32, and 38 °C. Of the four fungal species, Pisolithus tinctorius exhibited the greatest growth at the higher temperature treatments, with growth optima for all isolates occurring between 21 and 32 °C. The maximum temperature for growth of Cenococcum geophilum was 27 °C, with optimal mycelial growth occurring between 16 and 27 °C, depending upon the particular isolate considered. Suillus granulatus showed greatest mycelial growth at 27 °C and below, with temperature optima for the different isolates ranging from 16 to 32 °C. The pure-culture growth of Thelephora terrestris was high relative to the other fungal species examined with growth optima between 21 and 27 °C. The degree of intraspecific variation of mycelial growth in response to temperature was high for all fungal species, indicating the existence of physiologically distinct genotypes. Attempts to relate fungal growth performance to geographic origin of isolate showed a trend for Pisolithus tinctorius. However, no such relationships were apparent for the other species.
Mating incompatibility and cultural distinctions between Coprinus phaeosporus and C. psychromorbidus
Authors: Traquair James A.
Published: September 2008

Coprinus phaeosporus Karsten was incompatible with C. psychromorbidus Redhead & Traquair in dikaryon × monokaryon matings. Differences in optimal temperature, growth rate, and colony morphology on potato dextrose agar support the mating evidence that these fungi are distinct species.
Corolla depth and nectar concentration: an experimental study
Authors: Plowright R. C.
Published: September 2008

The effect of corolla depth on nectar concentration was examined both by field surveys of nine different species and by experimental manipulation of the spurs of flowers of Aquilegia caerulea. The surveys showed that the relationship between concentration and corolla depth was influenced by present and past environmental conditions. The Aquilegia caerulea experiment demonstrated, as expected, that nectar evaporates much faster in flowers with small effective corolla depths than in those with deep corollas. These results affect the usefulness of arguments about the adaptive significance of nectar concentrations. Here it is suggested that the dilute nectars reported from hummingbird flowers are a secondary consequence of their having evolved deep tubular flowers.
Effects of hardening and plant age on development of resistance to cottony snow mold (Coprinus psychromorbidus) in winter wheat under controlled conditions
Authors: Gaudet D. A. , Chen T. H. H.
Published: September 2008

The development of resistance in winter-wheat seedlings to the cottony snow mold pathogen, Coprinus psychromorbidus Redhead et Traquair, was studied under controlled-environment conditions. Resistance was measured by the percentage of inoculated plants surviving after incubation at −3 °C for 8–12 weeks. The number of weeks of prehardening growth prior to inoculation, fresh weight, LT50, and tiller number were positively correlated with resistance to C. psychromorbidus. Prehardening temperatures of 7 and 15 °C favored development of snow mold resistance compared with 2 °C, but the LT50 (50% killing temperature) values of uninoculated plants were not significantly different. After 1 and 2.5 weeks growth at 20 °C, plants hardened at 2 °C and 12-h day length gradually increased in resistance to snow mold from 1 to 15 weeks of hardening. Development of resistance to C. psychromorbidus in winter wheat was most influenced by the amount of prehardening growth, and the development of freezing resistance played a minor role in disease resistance development. This form of resistance, which develops with increasing plant age, appeared to reduce the rate of infection and disease development by C. psychromorbidus.
The influence of bacteria on trap induction in predacious hyphomycetes
Authors: Rucker C. J. , Zachariah K.
Published: September 2008

The induction of traps by the nematode Panagrellus silusiae in four fungal isolates of Dactylaria brochopaga and Arthro-botrys conoides was strongly influenced by several species of bacteria, which increased the yield mostly in light. In darkness with a stagnant atmosphere and a developing mycelium their effects were drastically altered; some bacteria then promoted the appearance of an abundance of megatraps in Dactylaria brochopaga.
Fruit removal rates from aggregated and isolated bushes of the red elderberry, Sambucus pubens
Authors: Denslow Julie Sloan
Published: September 2008

In July in northern Wisconsin, the red elderberry (Sambucus pubens (Michx.) synchronously ripens large panicles of bright red, small, watery, sweet drupes. During 1982 and 1983, I monitored bushes aggregated along an old logging track or isolated in tree-fall clearings to investigate the effects of isolation, crop size, and fruit quality on fruit removal by birds. All three factors significantly affected rates of fruit removal, although fruit removal rates were primarily a function of crop size. More fruits per bush per day were removed from large crops of both aggregated and isolated plants. Fruits were not removed disproportionately faster from plants with large than with small crops in either habitat. These results do not support the hypothesis that differential probability of dispersal success is an important selective factor in the evolution of delayed first reproduction or supraannual fruiting periodicities. However, removal rates from aggregated plants were lower than from isolated bushes in tree-fall clearings, probably an effect of local competition for frugivores. Sugar content of the pulp (but not fruit size) also significantly affected rates of fruit removal.