bluuebunny/crossref_metadata_2025 huggingface dataset:
Leaf surface effects of environmental pollution on sugar maple (Acer saccharum) in Montreal
Authors: Sharma G. K.
Published: September 2008

Leaf surface patterns of Acer saccharum Marsh. were investigated from extremely polluted and relatively unpolluted locations in Montreal, Quebec. In the polluted locations, the values for stomatal frequency were lower, and for trichome density higher than the corresponding values in the relatively unpolluted locations. No variation was evident in the subsidiary cell complex. These patterns may suggest adaptive significance in polluted environments.
Inhibition of chlorophyll synthesis in Lemna minor by nalidixic acid
Authors: Frick Hugh , Jones Raymond F.
Published: September 2008

Nalidixic acid bleached Lemna minor during growth in white light on a medium supporting heterotrophic growth. Immature, vacuolate mesophyll cells from bleached tissue contained plastids with aberrant thylakoids and had less-electron-dense cytoplasm than normal cells. Mitochondrial shape appeared normal. Individual bleached plants regreened and regained normal rates of growth after transfer to nalidixic-acid- (NAL-) free medium. Frond multiplication was also inhibited by NAL during growth in darkness. Purine and pyrimidine ribonucleosides did not prevent NAL-induced bleaching or growth inhibition.
Ultrastructural observations on septal and merosporangial ontogeny in Linderina pennispora (Kickxellales; Zygomycetes)
Authors: Benny Gerald L. , Aldrich Henry C.
Published: September 2008

Septal ontogeny in Linderina pennispora Raper & Fennell is initiated by the ingrowth of material from the inner of the two layers of the cell wall. The growing point of the septum bifurcates and continues growth, forming a lenticular cavity into which the septal plug is deposited. This type of septal development occurs in all septa except those produced between the pseudophialides and the merosporangia and spores. The latter septal type initially is formed as previously described, but then additional wall material is produced both above and below the septum. In the merosporangiospore three layers of wall material are produced, the inner two layers give rise to the spore spines, and at maturity all wall layers coalesce and form a single, thick spore wall. Extra wall material in the apex of the pseudophialide gives rise to a multilobed and mottled vacuole that shrivels just before spore liberation. Mature merosporangiospores are the only structures with spore spines. Aerial spines are produced on all structures except the merosporangiospores, although a relatively larger number of the aerial spines are produced on the aerial hyphae than on the pseudophialides and the sporocladia. The possible functions of the spore spines and the aerial spines are discussed.
Electron microscopy studies of a developing Pythium oogonium
Authors: McKeen W. E.
Published: September 2008

The young Pythium oogonium is filled with mitochondria, endoplasmic reticulum, several nuclei, electron-dense ground plasm, and four types of vesicles. The vesicles responsible for the production of the reserve globule contain a spherical electron-dense globule which enlarges from a tiny drop until it occupies a large part of the vesicle. The reserve vesicles coalesce in the central region of the oogonium and form the reserve globule. Other vesicles probably lipid in nature enlarge and fuse with each other and aggregate in the outer zone. In the mature oospore, the small amount of cytoplasm and one nucleus are sandwiched between the vesicles and the reserve globule. Vesicles containing microtubules, and numerous small vesicles underlying the oogonial plasmalemma and wall are also present. The nuclei move to the outer zone of the oogonium before fertilization of the privileged nucleus with the antheridial nucleus. All except the privileged nucleus degenerate in the periplasm. The periplasm is delimited at the time of fertilization and contains a great deal of endoplasmic reticulum at first. Large vacuoles soon occupy much space in the outer periplasm and they continue to enlarge as the oospore wall is formed. By the time the oospore wall is completed the zone between it and the oogonial wall is almost empty.
Development of photoreductive activity in plastids of a virescens mutant of barley
Authors: Horak Arnost , Zalik Saul
Published: September 2008

Plastids were isolated from 4- to 8-day-old seedlings of Gateway barley and its virescens mutant. At 4 days the normal barley plastids were well developed with respect to chlorophyll content, ultrastructure, and photoreductive activity. In contrast the mutant plastids were low in chlorophyll, contained predominantly single thylakoids, and their activity was low at this stage. By 8 days the amount of chlorophyll in the mutant plastids had increased, they had well-developed grana and their photoreductive activity reached normal levels. There seemed to be a correlation between the structure of photosynthetic membranes and their photoreductive activity during the development of the mutant barley plastids. It was concluded that chlorophyll content did not limit photoreductive activity at the earliest stage of development.
Host range and properties of tobacco stunt virus
Authors: Hiruki C.
Published: September 2008

Tobacco stunt virus (TSV) was mechanically transmitted to 41 species in 9 families: i.e., Aizoaceae, Amaranthaceae, Apocynaceae, Caryophyllaceae, Chenopodiaceae, Cucurbitaceae, Leguminosae, Pedaliaceae, and Solanaceae. TSV remained infective for 60 h in 0.001 M 1-phenylthiosemicarbazide (1-PTC) in 0.01 M phosphate buffer, pH 6.8, but was infective only immediately after extraction in phosphate buffer. TSV in 1-PTC-phosphate buffer had a thermal inactivation point between 75 and 80 °C and a dilution end point between 10−2 and 10−3. Comparative studies made on reaction of host plants, serological reaction, and cross protection indicate that TSV is unrelated to a California isolate of tobacco necrosis virus.
Genera coelomycetum. XII. Tracyella and Amerodiscosiella
Authors: Raj T. R. Nag
Published: September 2008

Tracyella (Sacc.) Tassi, type species T. spartinae (Peck) Tassi, is redescribed. Tracyella aristata (Cooke) Tassi is accepted as the second species of the genus, T. andrasovszkyi Moesz is considered as a nomen dubium, and T. julia (Speg.) Moesz and T. minima (B. & C.) Moesz are excluded. It is suggested that a fungus recently reported from graminaceous hosts under the name Amerodiscosiella renispora Farr is in fact T. spartinae. Amerodiscosiella Farr and A. renispora are maintained as distinct, if doubtful, taxa of unknown affinities.
A new tissue essential to necrophylactic periderm formation in the bark of four conifers
Authors: Mullick D. B.
Published: September 2008

Impermeability to OSO4 of periderm-free zones around the feeding sites of balsam woolly aphid (BWA), Adelges piceae, in the bark of Abies, was caused by a non-suberized impervious tissue (NIT). NIT developed at mechanical injuries in living bark of Abies grandis, Abies amabilis, Tsuga heterophylla, and Thuja plicata in 3 to 4 weeks during summer. It was found at healed injuries regardless of the cause, biotic or abiotic, at abscission scars, and at old resin blisters and rhytidome. It is concluded that NIT precedes formation of necrophylactic periderms (NP), may provide environment necessary for NP formation in tissues internally abutting NIT, and is a marker for distinguishing NP from exophylactic periderms. The imperviousness of NIT to water resulted neither from suberin (seven tests) nor from callose (three tests), and was detected by an F–F test, which is based on penetration of 2% FeCl3 followed by 4% K3Fe(CN)6 through the bark for 3 days each. The formation of NIT in the absence, e.g. rhytidome, as well as in the presence of injuries, BWA, and disease agents, suggests that NIT production is not only a non-specific inherent process but may be the physiological basis of host response to diseases in bark. Pathogen-free, "non-induced" NIT formation at rhytidome as a control process for isolating the host component of host–pathogen interactions is discussed.
Parasitism of the sclerotia of Sclerotinia sclerotiorum by Microsphaeropsis centaureae
Authors: Watson A. K. , Miltimore J. E.
Published: September 2008

A plant pathogen, Microsphaeropsis centaureae Morgan-Jones, was found to be parasitic on the sclerotia of Sclerotinia sclerotiorum (Lib.) deBary.
Revision of the Seuratiaceae. II. Taxonomy and nomenclature of Seuratia
Authors: Meeker Joseph Andrew
Published: September 2008

Four species are accepted in the genus Seuratia Patouillard, one of which is represented in its type only by its imperfect state of Atichia. The type species of Seuratia is S. coffeicola Pat. =S. millardetii (Racib.) comb. nov. Seuratia millardetii is the perfect state of Atichia glomerulosa (Ach. ex Mann) Stein. A new combination, S. globifera, is given for a species originally collected in the Hawaiian Islands. The genera Phycopsis Mangin and Patouillard and Phaeophycopsis Batista, based on S. vanillae Pat. and a morphological variant of S. millardetii respectively, are synonyms of Seuratia. Two new species are described from Hawaii, S. maunauluana and A. solaridiscoidea. For the latter species no herbarium material is available for typifying a name in Seuratia, but rare collections containing asci are described. All the species are distinguishable on the basis of morphology of the conidia and their location on the colonies. The genus Seuratia is retained in the monotypic family Seuratiaceae Vuillemin (Myriangiales).
Resistance to Cronartium ribicola in Pinus monticola: an analysis of needle-spot types and frequencies
Authors: McDonald G. I. , Hoff R. J.
Published: September 2008

Two kinds of needle spots, red and yellow, were found 9 months after artificial inoculation of 2-and 3-year-old, nursery-grown western white pine seedlings with field-run Cronartium ribicola inoculum. The causal agent was verified by histological examination of samples of the two spot types, by exclusion of inoculum from a portion of the seedlings, and by comparison of stem symptoms originating from the two spot types. When seedlings from three populations and two inoculation years were classed according to spot type, the class proportion varied from 68.4 to 9.0% yellow-type plants, 5.7 to 63.9% red-type plants, and 25.8 to 41.7% double-type plants. However, the mean spot frequency of each class for all three populations exhibited little variation. One population yielded frequencies of 12.11, 9.55, and 20.12 spots per metre of needle length on yellow-type, red-type, and double-type seedlings respectively. The second population yielded 7.66, 9.85, and 17.14; and the third, 7.00, 9.14, and 18.49. The existence of distinct seedling classes combined with evidence that the sum of the means of the two single-type classes (12.11 + 9.55 = 21.66) was nearly equal to the mean of the double-type class (20.12) led the authors to conclude that field-run inoculum was composed of at least two races and that the pine seedlings exhibited differential resistance to those races.
Comparisons among isolates of Gremmeniella abietina by means of growth rate, conidia measurement, and immunogenic reaction
Authors: Dorworth C. E. , Krywienczyk J.
Published: September 2008

Growth records among a worldwide collection of isolates of Gremmeniella abietina revealed wide variation in response at different temperatures. Overall, the fungus was identified as a facultative psychrophile with extended capacity for growth at low temperatures and a thermal-death or growth-suppression point between 25 and 30 °C. The gross appearance of cultures, extent of spore septation, and appearance of heavily sporulating and pionnotal variants provide evidence to support a concept of separate North American and European physiologic races. This concept is further supported by comparisons among soluble proteins using immunologic methods, as a result of which a third (Asian) race is proposed. Gremmeniella abietina is defined as a single species in geographic disjunction with a minimum of three physiologic races. Formal subdivision of the species is discouraged in the absence of overwhelming evidence in support of such a requirement. The use of G. abietina and similar microorganisms with complex host ranges and aerially disseminated spore states as models in biogeographic analyses will be highly problematic if not impossible.
Low-temperature-induced cankers and burls in test conifers and hardwoods
Authors: Zalasky Harry
Published: September 2008

Frost cankers were induced by low-temperature treatments with freon in Pinus contoria var. latifolia, P. sylvestris, Malus sylvestris, Tilia cordata, Ulmus americana, and U. pumila. Temperatures of 0 to −30 °C were attained in the bark and 5 to −6.5 °C in the cambium. Frost burls and frost ribs were perpetuated by multiple treatments in P. contorta var. latifolia, P. sylvestris, M. sylvestris, T. cordata, Abies lasiocarpa, and Picea glauca. They were produced by modified cambium that gave rise to morphological chimeras characterized by resiniferous tissues or pitch pockets, spiral-grained and nodulated sapwood, and scabby bark. Dead bark, corky tissues, and solidified resin exfoliated from the periphery of the frost rib.The cambium was consistently killed at −6.5 °C, which was considered the lethal temperature. Changes in the surrounding freeze–thaw area of the bark often caused the 10-day-old cells of the restitution tissues to become multinucleate and the dividing nuclei to have c-mitotic end-to-end chromosomes and tripolar spindles.Burl growth ring of conifers and hardwoods develops a xylem ray underlay gradually succeeded by restitution xylem. The phloem ray overlay is unique because of its resiniferous corky tissues, which consist of inner layers of irregular parenchymatous cells and outer layers of distinctive sclereid-like cells with recurvate lobes. The rays of phloem and xylem also have resin cells and sclereid-like cells diffused throughout the body of the ray. Deformed cells show cytological changes in the cell wall, lumen, and pits. Vessels have changes in the number and position of pits and perforations. Differences and similarities between low-temperature and fungus-induced cells and tissues are noted.
Interspecific relationships and the question of introgression between Picea engelmannii and Picea pungens
Authors: Taylor Ronald J. , Williams Susan , Daubenmire R.
Published: September 2008

Three chemical markers presumed to be leucoanthocyanins and several morphological parameters were used in testing the hypothesis of introgression between Picea engelmannii Parry and P. pungens Engelm. Hybrid indices and a discriminant analysis were used to reflect intra-and inter-populational variation and interspecific relationship. In spite of extensive morphological overlap between the two species, the pattern of chemical expression was consistent with intermediate conditions infrequently occurring in three sympatric populations, suggesting hybridization. In these populations, introgression was further indicated by an unusual segregation of morphological characteristics. Possible selective pressures and resulting evolutionary trends involving the two species are discussed.
Effect of rifampin application time on crown-gall tumor induction by Agrobacterium tumefaciens
Authors: Anand V. K. , Heberlein G. T.
Published: September 2008

Rifampin was applied to Kalanchöe leaves, primary pinto-bean leaves, and carrot root discs at various times after inoculation with Agrobacterium tumefaciens. Inhibition of tumor induction was substantial and maximal when rifampin (200 μg/ml) was applied to the wound sites immediately after bacterial inoculation. The time period after inoculation during which rifampin remained inhibitory varied with the plant host used. Inoculated Kalanchöe leaves remained sensitive to rifampin for 36 h while pinto-bean leaves and carrot discs remained sensitive for 20 and 4 h, respectively. Rifampin failed to inhibit tumor induction when applied to plant wounds inoculated with rifampin-resistant mutants of A. tumefaciens. Tumor weight was typically enhanced by rifampin in the Kalanchöe and carrot assays when applied after the period in which it was inhibitory. The viability of A. tumefaciens in vitro and while on the plant was substantially reduced by rifampin. Nevertheless, the lethal effect of the drug on A. tumefaciens was insufficient to fully account for its inhibitory effect on tumor induction.
Studies on lichen-dominated systems. XIV. The comparative ecology of Alectoria nitidula and Cladina alpestris
Authors: Kershaw K. A.
Published: September 2008

The response of net photosynthesis and respiration in Cladina alpestris and Alectoria nitidula, at 0 and 150 μeinsteins m−2 s−1, 5, 10, 15, 20, 25, and 30 °C, and at all thallus moisture levels, is described. The two species have markedly contrasting responses, which correlates very well with their ecology at East Pen Island. Cladina alpestris is shown to occur in two physiological forms: one is restricted to beach ridge summits and the other is restricted to the lower slopes. The physiology of these two forms adapts them to either the cool, dry, ridge crests or the warmer, moister, ridge slopes. Marked acclimation of the temperature optimum of net photosynthesis in Alectoria nitidula is shown to occur between August and December. This is an acclimation of the photosynthetic mechanism of the algal component since respiration rates remain constant. Alectoria nitidula is shown to further acclimate to warm temperatures under air-dried conditions in the laboratory.
Studies on lichen-dominated systems. XV. The temperature and humidity profiles in a Cladina alpestris mat
Authors: Kershaw K. A. , Field G. F.
Published: September 2008

Data are presented for three average sets of weather conditions that show the temperature and humidity gradients which develop within the canopy of Cladina alpestris. Temperature gradients of up to 17 °C develop in late August under partially cloudy skies, and it is suggested that gradients in excess of 20 °C will be a normal feature in spruce–lichen woodland in July under clear skies. These findings are discussed briefly in relation to the growth of Cladina alpestris and the potential differences in physiological activity of the canopy strata.
Two infection sites of Hypoxylon mammatum in trembling aspen (Populus tremuloides)
Authors: Manion Paul D.
Published: September 2008

Observations and dissection of young naturally occurring cankers caused by Hypoxylon mammatum suggest that infection of second- and third-season-old stems and branches commonly takes place at the base of first- and second-season-old dead branches. A second but less common infection site is associated with galls caused by the insect Saperda concolor.
Multiple circadian rhythms regulate photoperiodic flowering responses in Chenopodium rubrum
Authors: King R. W.
Published: September 2008

In constant conditions that follow daily temperature cycles, a circadian rhythm of cell division (20-h period) was apparent at the shoot apex of seedlings of Chenopodium rubrum. There was also rhythmicity in capacity to flower (21- to 24-h period) when the seedlings were exposed at various ages to a 12-h dark period. Neither oscillation was evident in seedlings raised under constant conditions. Rhythmical changes in flowering (20- to 24-h period) were also found upon treatment of seedlings for 6 h at different times with solutions of glucose (0.4 M), gibberellic acid (10−6 M), or ethanol (0.1%). This latter rhythm was apparent in constant conditions in the light long after export of floral stimulus from the cotyledons. It is argued that rhythmicity at the shoot apex, possibly in cell division, confers a 20- to 24-h periodicity on the flowering responses of C. rubrum.By contrast, exposure of seedlings or adult plants to a dark period of varied duration revealed a rhythm in capacity to flower but with a considerably longer period (about 30 h). This rhythm was present whether or not seedlings had been raised in fluctuating temperatures. The oscillation was also distinctive in that it originated in the leaf. Exposure of only one leaf on an adult plant to different durations of darkness induced the 30-h rhythm of flowering. Therefore, more than one rhythm, a leaf and an apex rhythm, may control flowering in C. rubrum.
The apical apparatus of the suboperculate ascus
Authors: Samuelson Don A.
Published: September 2008

Cytochemical and ultrastructural studies have been made on the apical apparatus of six members of the suborder Sarcoscyphineae (Pezizales), an aggregate of cup fungi that displays unusually thick opercula. Various workers have placed these types into a group entitled the suboperculates, which demonstrate properties of the apical apparatus similar to both the inoper-culate and the true operculate Discomycetes. Recently, certain researchers have questioned the validity of the suboperculate apical apparatus as a stable phylogenetic indicator.Investigations were made from freshly collected material including Sarcoscypha coccinea, Phillipsia domingensis, and Wynnea americana, and from herbarium specimens including Cookeina sulcipes, Urnula craterium, and Pseudoplectania nigrella. Of the stains used for light microscope examination, Congo red proved to be the most successful for observing the opercula of fresh and revived material. Ultrathin sections for electron microscopic inspection were often treated with silver methenamine to enhance wall characteristics.The operculum is derived from the inner layer and bordered by a fibrillar zone of dehiscence which is typically absent in the outer layer. The degree of complexity of the apical apparatus ranged from a simple structure seen in Pseudoplectania to a sophisticated form found in Cookeina. The morphology of the operculum and its related components in unique enough to be implemented as a useful taxonomic criterion.
Bark beetle – fungal symbiosis. III. Ultrastructure of conidiogenesis in a Sporothrix ectosymbiont of the southern pine beetle
Authors: Happ George M. , Happ Christine M. , Barras Stanley J.
Published: September 2008

SJB 133 is an isolate of a variety of Ceratocystis minor that is found in a Sporothrix imperfect state as an ectosymbiont of Dendroctonus frontalis Zimm. Within the mycangium (fungal transport pocket of the beetle), SJB 133 grows in yeast-like fashion. Cells contain prominent vacuoles which appear to bridge between dividing cells. Hypha-like transition cells are also present. In continuous culture on potato carrot agar, SJB 133 produces sympodial conidiophores. The resulting conidia are quite similar to the yeast-like cells in the mycangium and the conidiophores resemble some of the transition cells.
Ageing characteristics of wood of healthy and sandhill-declined Citrus sinensis
Authors: Nemec S.
Published: September 2008

Cytological studies of starch, lipid, nuclei, dehydrogenases, and diaphorase activity in parenchyma of healthy and sandhill-declined trunk wood of Citrus sinensis 'Valencia' indicated that wood aged rapidly after a high metabolic activity near the cambium. Ethylene evolution and oxygen uptake were high in wood next to the cambium; ethylene was low in older wood and gas evolution was typical of older wood. Diseased wood contained less starch but more lipid than healthy wood. Lipid vessel plugs, caused by lipid leakage into vessels, and moisture content increased in wood as it aged. Characteristics of parenchyma cell ageing and wood color place it in the revised category of woods with a delayed, uncolored heartwood.
Analysis of greening in virescent mutants of maize by in vivo spectrophotometry
Authors: Hopkins W. G. , Hayden D. B. , Walden D. B.
Published: September 2008

A rapid, sensitive, and non-destructive method for analysis of chlorophyll mutants of maize is described. The method, based on in vivo absorbance characteristics of leaf tissue, enables a quantitative description of the status and pattern of chlorophyll distribution within single maize leaves.
Day-length influence on reproductive development and tillering in ‘Fergus’ barley
Authors: Fairey D. T. , Hunt L. A. , Stoskopf N. C.
Published: September 2008

Effects of variation in day length on spikelet and tiller development were studied in a two-rowed barley, Hordeum vulgare L. cultivar ‘Fergus.’ Spikelet number and the length of the spikelet-forming phase increased with progressive reductions in day length from 24 to 12 h. However, increases in spikelet number were offset by abortion of spikelet primordia during spikelet differentiation and elongation of the stem internodes. Floral initiation occurred at all day lengths, but intemode elongation and heading were markedly delayed at 12 h. The cessation of spikelet initial formation and the beginning of internode elongation did not occur simultaneously in any day length. The latter began just before or at double ridge formation.Tiller numbers were highest at 12 h and progressively decreased in longer day lengths. Each plant produced four primary tillers at all day lengths, and differences in tiller number were accounted for by secondary and tertiary tiller production.
The vegetation and chemical properties of patterned fens in the Swan Hills, north central Alberta
Authors: Vitt D. H. , Achuff P. , Andrus R. E.
Published: September 2008

Three patterned fens in north central Alberta were analyzed to elucidate vegetation patterns in vascular plants and bryophytes. Two flark associations dominated by Menyanthes trifoliata and Carex limosa, both of which had Sphagnum jensenii and Drepanocladus exannulatus phases, were recognized. The strings consist of two associations; one is dominated by Betula glandulosa, Tomenthypnum falcifolium, and Aulacomnium palustre; the second is dominated by Picea mariana, Sphagnum magellanicum, and Ledum groenlandicum. An intensive analysis of one fen reveals that these mires are ‘poor fens’ with a mean pH of 5.2 and Ca2+concentration of 2.3 ppm. The fens occur on low drainage divides and Ca2+ is depleted as water flows through the fens. An ecological series of bryophytes is described in the transitions between flarks and strings.
The quiescent center and primary vascular tissue pattern formation in cultured roots of Zea
Authors: Feldman Lewis J. , Torrey John G.
Published: September 2008

Roots of Zea mays cv. Kelvedon 33 were cultured in nutrient media supplemented with varying concentrations of sucrose. In some instances an individual root was grown successively for periods of time in several different concentrations of sucrose. From this work it was shown that the complexity of the vascular patterns in cultured roots as well as the size of the quiescent center could be manipulated by altering the levels of sucrose in the nutrient medium. The simplest vascular patterns were found in roots in which the quiescent center was most reduced in size. In roots with relatively larger quiescent centers more complex vascular patterns were observed. Based on these studies a proposal is advanced concerning the relationship between the quiescent center and the initiation and maintenance of primary vascular tissue patterns in roots.
Effects of aging on chlorophyll fluorescence and photosystem II electron transport in isolated chloroplasts
Authors: Fragata M.
Published: September 2008

The correlation between emission of energy and photochemical activity in isolated chloroplasts during aging was investigated. It was shown that aging hinders the intensity of chlorophyll-a fluorescence with a concomitant decrease of the photosystem II activity. In view of the parallelism between the action of exogenous fatty acids, especially C18-unsaturated acids, and the effects of aging, it is suggested that the thylakoid transformation during aging could result partly from conformational changes of the membrane polypeptides due to the presence of free fatty acids in the neighborhood of the protein molecules. It is possible that such a mechanism of fatty acid action may alter the fluorescence characteristics of chlorophyll as well as the tunneling of electrons in the photosynthetic membrane.
A new Coelomycete (Dwayalomella vaccinii gen. and sp. nov.) from Vaccinium angustifolium in Canada
Authors: Brisson J. D. , Pirozynski K. A. , Pauzé J. F.
Published: September 2008

Dwayalomella vaccini which was isolated in Québec from stems of lowbush blueberry (Vaccinium angustifolium Ait.) is described and illustrated with light and scanning electron micrographs.
Subunit structure of the 12S protein from seeds of Brassica juncea
Authors: MacKenzie S. L.
Published: September 2008

The 12S globulin from Brassica juncea seeds has been dissociated by 6 M urea: 0.1 M mercaptoethanol and the resultant products have been partially separated by preparative isoelectric focusing. Species that have the isoelectric points 4.75, 5.15, 5.40, 6.25, 6.70, 7.00, 7.20, 7.70, 8.30, 8.90, and 9.15 were detected. The results of poly aery lamide-gel electrophoretic analysis and the amino acid composition of the fractions suggested that the isoelectric species were distinct subunits.
Phycomycetes (Phytophthora spp. nov. and Pythium sp. nov.) associated with degrading mangrove (Rhizophora mangle) leaves
Authors: Fell Jack W. , Master I. M.
Published: September 2008

Fungi of the genus Phytophthora were found to be associated with the initial stages of leaf litter decay of Rhizophora mangle L. and other Rhizophora species in estuarine and coastal marine waters. Phytophthora appears to be an important component of red-mangrove litter degradation systems throughout the tropics, which includes the Atlantic, Pacific, and Indian Oceans. The distributions of Phytophthora vesicula Anastasiou et Churchland and four new species of Phytophthora are discussed, as well as their occurrence in other tropical marine allochthonous spermatophytic leaf litter. The descriptions of the new species and varieties, Phytophthora bahamensis, P. epistomium, P. mycoparasitica, P. spinosa var. spinosa, and P. spinosa var. lobata, are presented.Pythium was rarely observed in the mangrove litter system, although one species, Pythium grandisporangium sp.nov., is described.
The effect of vapor pressure deficit on diffusion resistance in Opuntia compressa
Authors: Conde Louis F. , Kramer Paul J.
Published: September 2008

Measurements of the diffusion resistance of Opuntia plants that were growing in a controlled environment were made with a porometer to determine the effect of vapor pressure deficit (vpd) on the diurnal pattern of diffusion resistance. When the vpd was high during the light period and low in darkness, diffusion resistance was greater during the day than at night. However, when the vpd was low during the day, diffusion resistance was lower during the day than at night. Thus diffusion resistance of Opuntia, at least under some conditions, is affected by the vpd of the atmosphere. This may explain the contradictory results that are reported by investigators working in different environments.
Fungi of Barro Colorado Island: new and interesting Hyphomycetes
Authors: Goos R. D. , Pirozynski K. A.
Published: September 2008

Twelve Hyphomycetes that were collected on Barro Colorado Island, Canal Zone, Panama, during July 1973 are reported. Botryomonilia scheeleae, gen. & sp. nov. and Uvarispora lignicola gen. & sp. nov. are described and illustrated.
Buried seed populations in the subarctic forest east of Great Slave Lake, Northwest Territories
Authors: Johnson E. A.
Published: September 2008

Buried seeds were studied in the subarctic forest east of Great Slave Lake, N.W.T., where 62 surface samples were collected in upland vegetation of different ages and compositions. No seeds germinated from any of the samples after cold treatment and exposure to warm, moist environment. Seeds were present in the soil, but most of them proved non-viable by the tetrazolium chloride test.Lack of viable buried seeds is consistent with a poleward decrease in the buried viable seed populations under forests. Possibly the gradient parallels a decrease in length of growing season and its effect on germination strategies. The lack of viable buried seeds provides a partial explanation of observed slow vegetational recovery after fire in subarctic forests.
Mating among isolates of three species of Sporobolomyces
Authors: Bandoni R. J. , Johri B. N. , Reid S. A.
Published: September 2008

Mating tests were made with the type strains of Sporobolomyces hispanicus Peláez & Ramirez, S. odorus Derx, and S. salmonicolor (Fischer & Brebeck) Kluyver & van Niel, and with 19 additional strains. These tests show that 21 of the strains are of two, intercompatible mating types. Since the three type strains are linked by compatibility, the names that have been applied are synonymous. Additionally, since mycelial and strictly yeast-like strains are compatible, the genus Prosporobolomyces Novák & Zolt appears to be unacceptable.
Seasonal variation of the terpenes of the leaves, buds, and twigs of blue spruce (Picea pungens)
Authors: von Rudloff E.
Published: September 2008

The variation in the relative amounts of the terpenes of the mature and young leaves, buds, and twigs of blue spruce was investigated during a full year. As with the spruces that were investigated previously, large changes were recorded only in the buds and in the young leaves after bud burst. The variations that were recorded in the latter for santene, tricyclene, camphene, camphor, bornyl acetate, and limonene were similar to those that were found in white spruce, but those of car-β-ene, α-pinene, and β-pinene differed. Several quantitative differences in the oil of the winter buds were also recorded. The variation of β-pinene correlated negatively with that of sabinene, γ-terpinene, and terpinolene. A transient diterpene alcohol of the geranylgeraniol type was found in the buds and young twigs during spring. The seasonal variation of the terpenes of the twig oil was smaller than the twig-to-twig variation within a tree. The implications for chemosystematic studies are discussed.
The thallic mode of conidiogenesis in the Fungi Imperfecti
Authors: Cole Garry T.
Published: September 2008

The current developmental concept of the thallic mode of conidiogenesis essentially involves the simple conversion and disarticulation of preexisting hyphal elements, in which extension growth has ceased, into conidia which are delimited by transverse septa. Two kinds of thallic development were originally interpreted from light microscopic investigations. In this paper, holothallic conidium formation, which is demonstrated by Geotricluim candidum, and enterothallic development, which is exemplified by Sporendonema purpurascens and Briosia cubispora, are compared and ultrastructural and karyological characteristics of these mechanisms of conidiogenesis are illustrated. Scanning electron microscopic analyses of conidium formation in Oidiodendron trancatum and Trichosporon beigelii and light microscopic investigations of Sympodiella sp. and Amblyosporium spongiosum have revealed that additional variations exist in the thallic mode of conidium ontogeny. On the basis of these new data, and a consideration of other species of imperfect fungi which demonstrate similar mechanisms of conidiogenesis, a revised concept of thallic development is presented.
Transformation tumorale chez le pois: passage d'un état précancéreux à l'état cancéreux
Authors: Kurkdjian A. , Manigault P. , Beardsley R. E.
Published: September 2008

Decapitated pea stems were infected by bacteria from virulent strains of Agrobacterium tumefaciens, sensitive or resistant to streptomycin, actinomycin, or rifampicin, and the antiobiotics were added at the same time as bacteria. At the concentrations used, they have no toxic action on plants. The determination of the number of ‘viable’ bacteria allowed us to describe a kinetic of the development of the bacterial population in vivo in relation to the inhibition of the continuous proliferation of the hyperplasia. The histological study agrees with this and allows the definition of two steps during the tumorous induction: the first one results in the formation of a callus with a limited growth (precancerous state), while the second is the maintenance of the anarchic and unlimited multiplication of the converted host cells (cancerous state).
Some effects of the nitrogen supply on growth and development of Cirsium arvense
Authors: McIntyre Gordon I. , Hunter James H.
Published: September 2008

The influence of nitrogen nutrition on the growth and development of Canada thistle, Cirsium arvense (L.) Scop., was investigated by growing seedlings in sand culture under controlled conditions. A preliminary experiment showed that seedlings at the cotyledon stage were very susceptible to injury by high salt concentration; a 10 × dilution of Hoagland's solution was required for successful establishment. Nitrate-N at 210 ppm caused severe leaf necrosis and inhibition of shoot and root bud growth, but provision of ammonium-N eliminated these effects.When seedlings were supplied with NH4NO3 at levels that ranged from 5.25 to 420 ppm N, shoot dry weight and root bud growth increased up to 210 ppm but decreased at 420 ppm, probably as a result of ammonium toxicity. By clearing roots with lactic acid it was shown that while growth of the root buds increased with the N level, the number of buds initiated was significantly reduced. When plants were grown initially at a low N level, a subsequent increase in the N supply permitted the root buds to escape from inhibition and develop as leafy shoots. This response suggested that under the experimental conditions, bud inhibition was due to internal competition for a limiting N supply.
The role of seed reproduction in the dynamics of established populations of Hieracium floribundum and a comparison with that of vegetative reproduction
Authors: Thomas A. G. , Dale H. M.
Published: September 2008

In the crowded parts of patches of Hieracium floribundum Wimm. and Grab., which were established for at least a decade in an ungrazed pasture, 7–10% of the population (3700 individuals/m2) flowered. Of the plants that flowered, 94% were alive a year later, but only 5% of these flowered. Abortion of flower heads was common; one half of all those which were initiated in early June had aborted by flowering time in early July. Freshly dispersed seed had a viability of 57%, which was reduced to 17% a year later, after its storage close to the soil surface. Less than 6% of the viable seed was innately dormant. Dry, laboratory-stored seed retained its viability for the year but was slower to germinate than soil-stored seed. In field conditions, germination was temperature inhibited during most of the growing season. Maximum daytime microsite temperatures of less than 32 °C, which is necessary for germination, were found to occur only in early spring and late fall. Successful seedling establishment accounts for 1% of the individuals in a crowded population. Based on the maximum sexual reproduction from plants in crowded populations, a seed has a probability of 1 in 20 000 of becoming an established seedling. A model of population dynamics in a high-density patch traces the fate of seedling establishment, surviving adults, and stolon-derived rosettes for a single year.
Physiological studies with the fungus Saprolegnia megasperma isolated from the freshwater nematode Neomesomermis flumenalis
Authors: Nolan Richard A.
Published: September 2008

The aquatic phycomycete Saprolegnia megasperma Coker is recorded for the first time from the freshwater nematode Neomesomermis flumenalis (Welch) Nickle. The optimum temperature for growth of the fungus is between 13 and 19 °C, and the optimum pH is between 5.2 and 5.7. The pH indicators tested were non-toxic to this isolate. The optimum concentration of phosphate was 15 mM. The optimum concentration of lactalbumin hydrolyzate under the conditions used was 4 g/litre. Glucose utilization occurred readily; 40% of the original level was utilized by day 3, and by day 4 the glucose level had dropped to 9.6% of the day 0 level. All of the detectable glucose in the medium had been utilized by day 5 under the test conditions. The utilization of ninhydrin-positive substances from media that contained lactalbumin hydrolyzate with and without glucose was determined. Under both conditions the following substances were taken up from the medium: glycerophosphoethanolamine, L-methionine sulfoxide, L-aspartic acid, L-threonine, L-serine, L-proline, L-glutamic acid, glycine, L-alanine, DL-cystathionine, L-methionine, L-isoleucine, L-leucine, L-tyrosine, L-phenylalanine, L-lysine, L-histidine, L-tryptophan, L-arginine, and L-valine. Ammonia and urea were produced in both media by the isolate. The polyamines, putrescine, cadaverine, spermidine, and spermine, were not detected as being released during autolysis.
Nematophagous fungi: a new endoparasite intermediate between Myzocytium and Lagenidium
Authors: Barron G. L.
Published: September 2008

Myzocytium intermedium is described as a new endoparasite of Rhabditis nematodes. It produces laterally biflagellate zoospores which track the host and encyst in the vicinity of the body orifices. Infection of mature nematodes is by means of germ tubes from encysted zoospores which penetrate through the body orifices.The thallus is filamentous, much-branched, and nodular in appearance. At maturity it divides to form numerous segments of irregular size and shape. In the vegetative phase the parasite resembles a Lagenidium. In the sexual stage, however, the young antheridium cannot be distinguished morphologically from either the oogonial or zoosporangial segments. No fertilization tube is produced and the antheridial protoplast migrates through a pore in the common wall to fertilize the oogonium. After fertilization, a thick-walled, smooth, spherical oospore is produced.
The vegetational zonation of the East Pen Island salt marshes, Hudson Bay
Authors: Kershaw K. A.
Published: September 2008

The extensive salt marshes at East Pen Island in Hudson Bay are described in quantitative terms and the well-marked sequence of species is characterized. The lower marsh is dominated by Puccinellia phryganodes and Carex subspathacea, with Hippurus vulgaris and Senecio congestus abundant in the salt pans. The midmarsh has well-developed swards of Dupontia fisheri and Celamagrostis neglecta, which give way to stands of Carex aquatilis in a well-developed freshwater marsh below the first beach ridge. The results are compared with other arctic salt marshes, and the development of a wide freshwater marsh in the upper zone of the salt marsh is described. This feature is perhaps unique to the Hudson Bay marshes and is a function of meltwater runoff from the surface of the permafrost table. This results in the high, standing water table at the top of the marsh, which is maintained by the permafrost table of the salt marsh itself.A transit survey of the marsh relates the quadrat samples to a high-tide datum point and allows interpretation of the vegetation sequence in terms of saltwater inundation. The depth of the active layer of the salt marsh is also described.
Host resistance to the fir engraver beetle. 1. Monoterpene composition of Abies grandis pitch blisters and fungus-infected wounds
Authors: Russell Charles E. , Berryman Alan A.
Published: September 2008

The monoterpene hydrocarbons of the cortical blister oleoresin of Abies grandis were compared, using gas chromatography, with those obtained from lesions that formed as a response of the tree to inoculation with cultured Trichosporium symbioticum, a fungus which is transmitted by the fir engraver beetle Scolytus ventralis. The resins from each source differed both quantitatively and qualitatively. Three terpenic compounds (tricyclene, camphene, and bornyl acetate) that are normally present in primary resin were not found in secondary resin. However, resins that formed in response to the inoculation contained higher concentrations of myrcene in three quarters of the trees and delta3-carene in one quarter of the trees that were sampled than resin from pitch blisters, which contained only trace amounts of these two compounds. These results suggest that conifers respond to fungus infection by producing monoterpenes which are more toxic, repellent, and (or) inhibitory to bark beetles and their associated fungi (e.g. myrcene and delta3-carene) at the expense of attractive or less biologically active compounds (e.g. camphene) which are present in the preformed resin system.
Physiological changes in the early stages of germination of pea seeds induced by aging and by infection by a storage fungus, Aspergillus ruber
Authors: Harman G. E. , Khan A. A. , Tao K. L.
Published: September 2008

Pea seeds age rapidly and may be infected by storage fungi, e.g. Aspergillus ruber, when stored under conditions of high relative humidity and temperature (92% relative humidity and 30 °C in these experiments). In the absence of microorganisms, pea seeds retain their viability for 6 to 8 weeks, although the speed of germination is reduced. In embryonic axes, aging is associated with a slower increase in O2 uptake, a delay in protein synthesis, smaller ATP and amino acid pools, and reduced activity of alkaline phosphatase (EC 3.1.3.1) and 3-phosphoglyceraldelyde dehydrogenase (EC 1.2.1.12). Axes recover from these changes during germination. Infection by A. ruber reduces germination. In axes from infected peas the onset of protein synthesis is delayed even more and the ATP and amino acid pools are smaller than in aged axes. Axes from infected seeds recover slowly, if at all.
Nuclear condition of the basidia, basidiospores, and mycelium of Marasmius perniciosus
Authors: Delgado Julio C. , Cook A. A.
Published: September 2008

Basidia, basidiospores, and mycelium were examined to determine the nuclear condition during different stages of growth of Marasmius perniciosus. Young basidia were binucleate and four mononucleate basidiospores developed after meiosis. The primary hypha from a germinating basidiospore was septate with uninucleate cells but persisted only for a short time and gave rise to mycelium resembling 'textura intricata.' Apparent fusion of hyphal branches resulted in dikaryotization, and subsequent formation of normal, binucleate hyphae with clamp connections at most septa suggests that the fungus is homothallic.
Cytokinin and inhibitor activity in roots and stems of sugar maple seedlings through the dormant season
Authors: Dumbroff E. B. , Brown D. C. W.
Published: September 2008

Cytokinin and inhibitor activity were followed in the roots and stems of 2-year-old maple seedlings exposed to normal overwintering conditions from early November through April. The production of new roots was also monitored, and all measurements were repeated with dormant control seedlings placed in a greenhouse from the beginning of the experiment and provided with warm temperatures and extended photoperiods. The level of cytokinin-like substances increased in the roots and stems of the outside group in March after a large surge in root activity that began in late February and continued through April. Cytokinins peaked just before budbreak, with the highest levels detected in the lateral roots. Three bands of activity were present on the chromatograms at Rfs 0.1, 0.6, and 0.9. Large cytokinin peaks were also observed in the non-chilled seedlings and were associated with two periods of active root growth and abnormal bud flush in the fall and spring. Abscisic-acid-like activity was detected in the roots and stems of both greenhouse and exposed seedlings, but it remained essentially constant in the stems. Changes that occurred in the roots were not associated with emergence of the buds from the dormant condition.