bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitosis in Phlyctochytrium irregulare
Authors: McNitt Rand
Published: September 2008

Mitosis in zoosporangia of the chytrid Phlyctochytrium irregulare is described from electron microscope observations and also from light microscope observations of both living and haematoxylin-stained thalli. At the onset of prophase the centriole complex replicates, and the complexes migrate to polar positions. The semi-persistent nucleolus is appressed to the nuclear envelope as the nuclear pockets invaginate, finally rupturing to create polar fenestrae, through which spindle microtubules penetrate the nucleus from the region of the centrioles at prometaphase. Metaphase chromosomes form an equatorial plate. Initial separation at anaphase seems to be accomplished mainly by shortening of chromosome-to-pole microtubules; additional anaphase and telophase separation is accomplished by elongation of the nucleus. A system of perinuclear endoplasmic reticulum is formed during prophase and is completed by metaphase. It persists during all division stages after its formation. Features of this mitotic apparatus are discussed with reference to earlier light microscope studies of chytrid mitosis. The ultrastructure of P. irregulare's mitotic apparatus is similar to that of certain unicellular green algae.
Nonpolar movement of N6-benzyladenine-14C in coleoptile, stem, petiole, and floral organ sections
Authors: Koevenig James L.
Published: September 2008

Movement of N6-benzyladenine-methylene-14C in Avena sativa coleoptiles, Colens blumei stems and petioles, and Cleome hassleriana stamen filaments, gynophores, and pedicels was studied by suspending sections horizontally between donor and receiver agar cylinders and determining radioactivity in receivers by scintillation counting. No polar movement was found in any of the plant organs. In time-course experiments using oat coleoptiles, the amount of radioactivity in receivers continued to increase for 24 h and the velocity was 1.5-2 mm/h, suggesting movement by passive diffusion. More radioactivity moved through stamen filaments and gynophore sections from mature expanded flowers than through those from young buds, apparently as a result of larger uptake and exit areas in expanded flowers. A significantly greater acropetal and basipetal movement through young pedicels is not due to area differences and probably results from a metabolic difference.
Origin of androgenetic callus and haploid geranium plants
Authors: El-Nil M. M. Abo , Hildebrandt A. C.
Published: September 2008

Geranium (Pelargonium hortorum Bailey) anthers, containing uninucleate immature pollen at the tetrad stage, were incubated on a modified White's medium at 28 ± 2 °C with 16 h light alternating with 8 h darkness at 23 ± 2 °C. The daughter cells derived from pollen were observed as a colony of four cells after 9 days, and 20 cells after 18 days. Nuclei of cells of the colonies formed were large and diffuse similar to the vegetative nuclei. Examination of dissected anthers after an incubation period of 1 month showed that the induced calli were in the pollen grain sac and not attached to the anther connective tissues. Established calli were subcultured on Murashige and Skoog medium for organoid differentiation. Plants differentiated from the anther callus of varieties Sincerity, Pink Camelia, and Salmon Irene were haploid (2n = 18), had single florets with five petals, and set viable seed.
Effects of lindane on cell structure of pea roots
Authors: Charnetski W. A. , Lichtenstein E. P. , Evert R. F.
Published: September 2008

Lindane affected growth of pea plants (Pisum sativum L.). Threshold concentrations of the insecticide at which no inhibitory effects could be noticed were established to be between 1 and 2 ppm. Below that level, plant development was stimulated, while above it primary roots were shortened, thickened, club-shaped, and lacked secondary root and root-hair development. Growth of the green plant parts was also significantly reduced.Changes in root morphology associated with lindane phytotoxicity were examined by scanning electron microscopy. A lack of secondary root and root-hair development, disruptions of the epidermal layer, "extraneous" surface tissue on roots grown in lindane-treated sand, as well as increased vacuolation in the region of elongation, were noticed. The disorganization and enlargement of the pericycle and lateral root initials created mechanical stresses which resulted in the disruption and breaking of cortical and epidermal tissue.Cytological changes in pea root tissue were investigated using light and transmission and scanning electron microscopy. The occurrence of anomalous cell wall development, both as simple cellulosic bars projecting into or traversing a cell and as random networks of material in the lumen of the cell, was noticed. The possible misinterpretation of multinucleate cells, as seen by light microscopy, is projected in view of the greatly enlarged and lobed nuclei identified through transmission electron microscopy. These nuclei were seen to inhabit more than one cell simultaneously by virtue of incomplete wall formation. Intramitochondrial crystals were identified; the frequency of their occurrence increased with increased lindane concentration in sand.
The effect of toxin from Helminthosporium maydis (race T) on isolated corn mitochondria: swelling
Authors: Gengenbach B. G. , Miller Raymond J. , Koeppe D. E. , Arntzen C. J.
Published: September 2008

Studies of the effects of Helminthosporium maydis race T toxin on mitochondria isolated from Texas male-sterile cytoplasm (cms-T) and nonsterile cytoplasm (N) corn have been conducted. Toxin added to cms-T mitochondria caused an energy-independent swelling in several media containing different osmoticants. Electron micrographs indicated that the swelling was caused by a specific disruption and vesiculation of the inner mitochondrial membrane. Toxin-induced swelling was correlated with an increase in the rate of NADH oxidation and a decrease in the rate of malate + pyruvate oxidation. We suggest that the toxin is not acting as a specific ionophoric agent or uncoupler but rather is causing a change in rate of substrate oxidation simply as a consequence of membrane disruption. We cannot definitely determine, however, whether changes in electron transport rates are due to interaction of the toxin with specific carriers in the mitochondrial electron transport pathways or whether the change in membrane configuration has altered the accessibility of various substrates to their oxidation sites.Mitochondria from four different N genotypes were unaffected by toxin. Mitochondria from five cms-T genotypes were all disrupted by the toxin, but each to a different extent. There was a correlation between the response of cms-T mitochondria to toxin and their field susceptibility to H. maydis within cms-T genotypes.
Soluble and lamellar proteins in seedlings of barley and its virescens mutant in relation to chloroplast development
Authors: Jhamb Swadesh , Zalik Saul
Published: September 2008

When Gateway barley and its mutant were grown at 600 ft-c and 20 °C the soluble leaf proteins separated into 21 discrete bands by acrylamide gel electrophoresis. The most intense broad band of low mobility probably was fraction I protein and was present in 4-, 6-, and 8-day-old seedlings. At 4 days the amount of this protein in the mutant was small but it increased with age. At 8 days no differences were observed in the electrophoretic patterns of the two lines.On treatment of chloroplast lamellae with 0.5% sodium dodecyl sulfate several proteins were separated electrophoretically from Gateway barley at 4, 6, and 8 days. When grown at 600 ft-c and 20 °C, 4-day-old seedlings of the mutant lacked some of the proteins but at 8 days the gel patterns of Gateway and its mutant were similar. When grown at 1400 ft-c and 23 °C the mutant compared to Gateway lacked some proteins even at 8 days.Under 600 ft-c and 20 °C the mutant had about one-third as much chlorophyll as the normal at 8 days and under 1400 ft-c and 23 °C it had only about one-fifth as much. Electron microscope studies of the leaves showed that Gateway barley had well-developed chloroplasts under both growth conditions at 4 days, whereas the plastids of the mutant were not well developed at 4 or 6 days. By 8 days under the lower light intensity the mutant contained normal plastids but under the higher intensity the plastids were still not well developed. A relationship between chloroplast morphology and the proteins and pigments present was noted.
Heavy-metal tolerance in algae isolated from contaminated lakes near Sudbury, Ontario
Authors: Stokes P. M. , Hutchinson T. C. , Krauter K.
Published: September 2008

Chemical analyses of lake waters in the Sudbury smelting area indicated abnormally high levels of metals, especially of copper and nickel. Two of the algal isolates from these contaminated lakes, a Scenedesmus species and a Chlorella species, were chosen for study. Their growth, as determined by cell number, was tested under controlled conditions in defined media. Nutrient conditions, pH, and concentration in solution of copper and nickel were used as variables in bioassays. In comparison with laboratory strains of similar algae, in medium with no chelate (ethylenediaminetetraacetic acid) the isolated lake strains were found to be tolerant of the heavy metals nickel (Scenedesmus) and copper (Scenedesmus and Chlorella). The patterns of response to metals in solution differed markedly between laboratory and lake strains. The ecological implications are considered.
Phytogeography and ecology of the lichen family Umbilicariaceae in southwestern Alberta
Authors: Bird C. D. , Marsh A. H.
Published: September 2008

Eleven species of the genera Omphalodiscus and Umbilicaria in the lichen family Umbilicariaceae are reported from a 13 400-km2 area in the mountains and foothills of southwestern Alberta. Previous reports of Umbilicaria arctica and U. cylindrica are, or are felt to be, in error. Umbilicaria cinereorufescens is reported as new to Alberta. The distribution and habitats occupied by each of the taxa are described and a key to all species is provided. All taxa obligately occur on rock and in most cases are only on silicate rocks. Ten of the species are Circumpolar, Arctic–Boreal Alpine–Montane, and one is American, Cordilleran.
Evidence for close association of peroxidase, polyphenol oxidase, and IAA oxidase isozymes of peanut suspension culture medium
Authors: Srivastava O. P. , Huystee R. B. van
Published: September 2008

Peroxidase, polyphenol oxidase, and indole-3-acetic acid (IAA) oxidase were detected in a 7-day-old medium of a peanut cotyledon cell suspension culture. Preliminary separation of the isozymes of these three enzymes was achieved by acetone fractionation and acetic acid extraction. By means of zymograms on polyacrylamide gels, five anionic and two cationic peroxidase isozymes were identified. Staining of the gels for polyphenol oxidase and IAA oxidase revealed an Rf pattern for a number of isozymes that was identical with that found for peroxidase. These isozymes were separated using ion-exchange chromatography. Again the elution pattern for the isozymes of the three enzymes was so similar that it can be regarded as an enzyme possessing all the three types of activity.
A study on the degradation of arachin by proteolytic enzymes
Authors: Huystee R. B. van
Published: September 2008

The prime purpose of this proteolysis study was to direct attention to alternate means of measuring proteolytic activity other than the determination of free amino acids. The release of peptides from a macromolecular protein during incubation with either papain, pronase, or trypsin was determined by measuring the presence of 280-nm-absorbing molecules in the fractionation range of Sephadex G 25 eluant after incubation. The formation of larger proteinaceous constituents by proteolysis of arachin was analyzed by disc electrophoresis on polyacrylamide gels. Using these techniques it was noted that papain was the most efficient proteolytic agent for the degradation of arachin.
Bud development in western hemlock. I. Annual growth cycle of vegetative buds
Authors: Owens John N. , Molder Marje
Published: September 2008

Vegetative apices of mature Tsnga heterophylla (Raf.) Sarg. were studied throughout the annual growth cycle. Apices become mitotically active during the last week of March. Leaf primordia elongate, causing the buds to swell, while the apex remains small and produces bud scales. Axillary buds are initiated about mid-April. Little shoot elongation occurs before vegetative buds burst in mid-May. After bud burst, rapid shoot elongation occurs for about 7 weeks, during which time the apex also elongates and the rest of the bud scales are initiated. There is a marked increase in mitotic activity in the apex during the transition from bud-scale initiation to leaf initiation, which occurs early in July when the grand phase of shoot elongation is complete. This is believed to be the time when vegetative apices undergo transition to become reproductive apices. Leaf primordia are initiated in rapid succession until mid-August, when two-thirds of the final number of leaves are initiated and the subtending shoot is fully elongated. From mid-August until mid-November, no shoot elongation occurs, leaf primordia are initiated more slowly, and mitotic activity in the apex gradually decreases. After all of the next season's leaves have been initiated, about mid-November, mitotic activity in the apex stops and the vegetative buds become dormant.
Competitive ability of oat stem rust races in mixtures
Authors: Martens J. W.
Published: September 2008

Mixtures of races of oat stem rust (Puccinia graminis Pers. f. sp. avenae Eriks. and E. Henn.), differing in virulence, were cultured on susceptible plants in growth cabinets for five uredial generations at 15, 20, and 25 °C and in the field. The races with fewest genes for virulence maintained or increased their levels in the growth cabinets in all cases but were consistently outperformed by races with more genes for virulence under field conditions. The field results are in general agreement with the course of evolution of physiologic races of oat stem rust in Canada over 50 years; they suggest that the number of genes for virulence carried by a given race, other than those required for successful parasitism, is probably not the key determinant affecting its success in nature.
The regulation of peroxidase activity by gibberellin and auxin in pea stem segments
Authors: Ockerse Ralph , Mumford Laura M.
Published: September 2008

Peroxidase activity in excised stem segments of Pisum sativum L. cv. Progress No. 9 increases linearly during incubation in buffered medium. Gibberellic acid (GA) causes a slight reduction in activity whereas indoleacetic acid (IAA) treatment completely prevents this rise. Excision produces two new cathodic isoperoxidases near the cut ends. Their appearance is prevented by cycloheximide, actinomycin D, and IAA; G A enhances this IAA-induced repression. GA alone stimulates one of the isozymes but does not affect the other one. Peroxidase leakage is stimulated by GA and inhibited by IAA treatment. The activity is entirely confined to the isoperoxidases produced in response to injury.IAA oxidase activity in incubated segments was slightly elevated over that of freshly cut ones. However, differences in activity among hormone treatments were small. IAA oxidase was also demonstrated in growth media and only IAA treatment reduced activity. Both peroxidases in the medium were isolated by column chromatography. Surprisingly, the purified isozymes appear to be essentially devoid of IAA oxidase activity.
The conidial state of Peziza ammophila
Authors: Paden John W.
Published: September 2008

The conidial state of Peziza ammophila is considered to be a reduced Oedocephalum-type. Conidia are holoblastic and are borne on often curved or procumbent conidiophores. They are ellipsoid, ellipsoid-fusoid, or obovate, continuous, at first smooth and hyaline, becoming golden brown and roughened with large warts. Germination of conidia has not been seen.
Cytochalasin B: effects on root morphogenesis in Allium cepa
Authors: Thomas D. des S. , Lager N. M. , Manavathu E. K.
Published: September 2008

Cytochalasin B (CB) applied at 30 μg/ml to seeds of onion, Allium cepa, from the start of imbibition, produced a reversible inhibition of mitosis and axis elongation. Inhibition appeared only after the 4th day and increased progressively thereafter. Mitotic inhibition by a 24-h pulse of CB applied to 6-day-old seedlings increased with root length. These results suggest that CB affects plant mitosis indirectly, possibly via inhibition of transport. CB did not produce polyploid or multinucleate cells.Cytochalasin B (30 μg/ml) supplied for 3 days to roots of onion bulbs, growing in water, produced morphological changes which are expressed here as percentages of the controls. Root length decreased (44%) while diameter increased (148%). Cortical cell lengths decreased (53%) and diameters increased (128%) when measured at 9 mm from the root tip. These compensatory changes resulted in comparatively minor decreases in root (97%) and cell (90%) volume, indicating that CB, even at the high concentration used, was not acting primarily as a general metabolic inhibitor. Cell counts along diameters at comparable distances, 130 cortical cells from the apical initial region, showed no change in the number of cells representing cortex and stele.
Fungi from Canadian coniferous forest soils
Authors: Widden P. , Parkinson D.
Published: September 2008

The fungus flora from four pine forest soils was investigated. Qualitative studies used a soil-washing method, whereas quantitative investigations were performed using a direct observation technique. Results indicate that the fungus populations on litter and humus from all four forest soils are fairly similar, with Cladosporium herbarum, Aureobasidium pullulans, Alternaria sp., and various members of the order Sphaeropsidales being common in the litter, and Trichoderma and Penicillium species increasing in frequency in the F and H layers. The fungi isolated from the mineral soil horizons were more varied in nature, but certain genera seemed to be found frequently; these included Mortierella, Chrysosporium, Oidiodendron, Paecilomyces, Cylindrocarpon, Torulomyces, and sterile dark fungi.A detailed investigation of a Pinus strobus forest at St. Williams, Ontario, revealed no distinct seasonal patterns in the relative frequencies of the species of fungi.Quantitative studies showed that, in all soils, mycelial content decreased with depth from the humus. A comparison of the four sites showed a wide variation in fungal mycelium, varying from 30 m/g dry soil under Pinus strobus (in the A1 horizon) to 1540 m/g under P. contorta during May. Seasonal data from the P. strobus forest indicate a peak in mycelial content during August.
Conidiogenesis in Termitaria snyderi (Fungi Imperfecti)
Authors: Khan Saeed R. , Aldrich Henry C.
Published: September 2008

Termitaria snyderi Thaxter forms small discoid lesions on the exoskeleton of different species of termites. Its conidiogenesis has been studied by light and electron microscopy. The phialides are oriented parallel in a closely packed sporodochium. The conidia are produced endogenously in basipetal succession from a fixed conidiogenous locus and are liberated when the tip is broken off the phialide as a result of the force applied by the formation of new conidia. The area of the phialide beyond the locus forms a tubular collarette. The conidium initial buds out at the locus and after it has received its organelles and reached a certain size it is delimited by a centripetally growing transverse septum. The region of the growing septum has many vesicles which may be involved in cross wall synthesis. Conidia are cylindrical, uninucleate, and double-walled. They have mitochondria, endoplasmic reticulum (ER), conspicuous lipid droplets, and vacuoles. Each conidiophore has long mitochondria, elongate nuclei, and much endoplasmic reticulum. The plasmalemma of the conidiophore is highly convoluted.
Postinfectional inhibitors from plants. VII. Tolerance of capsidiol by fungal pathogens of pepper fruit
Authors: Ward E. W. B. , Unwin C. H. , Stoessl A.
Published: September 2008

Alternaria alternata and Fusarium oxysporum were isolated from field-grown peppers (Capsicum frutescens L.) and the antifungal sesquiterpene, capsidiol, was demonstrated in A. alternata lesions. In laboratory experiments, both fungi induced strongly antifungal diffusates and the activity was shown to be due to their content of capsidiol, or in the case of F. oxysporum to a combination of capsidiol and capsenone. Growth of the non-pathogen Monilinia fructicola was completely inhibited by the A. alternate diffusate at one-eighth and by the F. oxysporum diffusate at one-quarter of the original concentration. The inducing fungi were also inhibited by their own diffusates 80% and 50% respectively but, in spite of this, effectively parasitized fruit tissue.
Conifer water potential as influenced by stand density and environmental factors
Authors: Wambolt Carl L.
Published: September 2008

An investigation of several conifer species was conducted to evaluate the influence of atmospheric, edaphic, topographic, and vegetation variables of the environment on water potential. Correlation coefficients averaged close to 1.0 for the relationship of plant density to water potential when other environmental influences were static. This was interpreted as quantitative evidence of the intraspecific competition for available moisture by plants. Water potential values of 21 stands of coniferous trees, 3 each of seven species, were quite highly correlated (R = 0.84) to elevation, percentage sand, temperature, relative humidity, and vapor pressure deficit, even though the stands were found in widely divergent habitats.
A scanning electron microscopic study of epicuticular waxes of glumesin Avena magna, A. murphyi, and A. sterilis
Authors: Baum B. R. , Hadland V. E.
Published: September 2008

The ultrastructure of epicuticular glume waxes in two tetraploid Avena species, A. magna and A. murphyi, and in one hexaploid species, A. sterilis, has been studied and documented with the aid of the scanning electron microscope (SEM). The usefulness of this approach for taxonomy and diagnostic purposes has been evaluated, and the specific configurations of those epicuticular waxes compared in relation to the genomes.
Floral development of Hydrocleis nymphoides
Authors: Sattler R. , Singh V.
Published: September 2008

After the inception of three sepal primordia, three petal-stamen (CA) primordia (bulges) are formed in alternisepalous positions. On each of these bulges a petal is initiated, followed by a pair of stamens relatively high up on the bulge, where it is continuous with the floral apex. Growth extends between the three bulges, thus forming an inconspicuous circular rim around the floral apex. As this rim increases in size, further stamens and eventually staminodia are formed centrifugally on the rim. Five or six carpel primordia are initiated centrally to the first-formed pairs of stamen primordia long before all stamens and staminodia have appeared. In spite of considerable deviations from the trimerous monocotyledonous floral construction, the primary organogenetic pattern is trimerous (with the exception of at least the pentamerous flowers) and it is comparable to the primary patterns found in Alisma, Butomus, and other Alismatales. Thus, the study of the earliest developmental stages reveals a common plan that is elusive in later developmental stages and mature flowers.
Genera coelomycetum. X. Ellisiella, Samukuta, and Sakireeta
Authors: Raj T. R. Nag
Published: September 2008

Evidence is presented in support of the earlier disposition of Ellisiella Sacc. as a synonym of Colletotrichum Cda. Corrected nomenclature and synonymy is given for the fungus so far known under the name Ellisiella caudata (Peck) Sacc. Ellisiellina biciliata Camara is reduced to synonymy with Dinemasporium gramineum Lév. Samukuta Subram. & Ramakr. and its type species S. berkeleyii Subram. & Ramakr. are treated as synonyms of Neottiospora Desm. and N. caricina (Desm.) Höhn. respectively. Sakireeta Subram. & Ramakr. is reduced to synonymy with Tiarosporella Höhn., which is enlarged to include three species: T. paluclosa (Sacc. & Fiori) Höhn., T. graminis (Piroz. & Shoem.) comb. nov., and T. madreeya (Subram. & Ramakr.) comb. nov. Emended generic descriptions are given for Neottiospora and Tiarosporella.
Morphogenesis of the stamenless-2 mutant in tomato. II. Modifications of sex organs in the mutant and normal flowers by plant hormones
Authors: Sawhney Vipen K. , Greyson Richard I.
Published: September 2008

Application of gibberellic acid (GA3) to young plants of a single gene recessive stamenless-2 (sl2/sl2) mutant of tomato produced 'phenocopies' of the normal plants. Unlike the untreated sl2/sl2 mutant, flowers of GA3-treated plants bore no external ovules, possessed more yellow-pubescent stamens and fewer carpelloid stamens per flower, and produced laterally fused stamens. Stamen length at maturity was similar to normal flowers. In addition, viable pollen resembling the normal was produced in GA3-treated sl2/sl2 flowers. It was also found that GA3 was more effective than GA4+7 in inducing stamen development. Normal plants treated with GA3 produced multicarpellary and multilocular ovaries. Indoleacetic acid (IAA) induced the carpellization of stamens in sl2/sl2 flowers but had no apparent effect on the flowers of normal plants. It is proposed that added gibberellins promote maleness in systems where there is an inhibition or abnormality of stamen development, whereas they stimulate femaleness (possibly through an increase in auxin content) in systems with normal stamen development.
Delayed germination in seeds of Phacelia dubia var. dubia
Authors: Baskin Jerry M. , Baskin Carol C.
Published: September 2008

Not all seeds of a particular seed crop of the winter annual Phacelia dubia var. dubia germinate the first autumn after their dispersal in spring, and germination of a given seed crop is spread over several years. Nondormant seeds that do not germinate in autumn are induced into secondary dormancy by low winter temperatures and must afterripen again during summer before they are capable of germinating. Seeds that do not afterripen the first summer after dispersal are prevented from doing so until at least the next summer because winter temperature conditions prevent afterripening. These responses of the seeds to the environment insure that germination will occur only in autumn, the only season of the year that is suitable for seedling establishment and eventual completion of the life cycle.
Inhibition by actinomycin D of the increase in hydrolase activity induced in dandelion root tissue by treatment with 2,4-dichlorophenoxyacetic acid
Authors: Rutherford P. P. , Deacon A. C.
Published: September 2008

Actinomycin D was found to inhibit the increase in hydrolase activity induced in dandelion (Taraxacum officinale Weber) root tissue by treatment with 10−5 M solutions of 2,4-dichlorophenoxyacetic acid (2,4-D). The results obtained from transfer experiments suggest that the 2,4-D - induced increase in hydrolase activity is, at least in part, dependent upon the continued synthesis of a messenger RNA.
Glucose, fructose, and sucrose influx into Nitella flexilis
Authors: Wallen D. G.
Published: September 2008

The uptake of 14C-labeled glucose, fructose, and sucrose into Nitella flexilis has been investigated by varying concentrations of sugars, by the use of competition experiments, by the use of inhibitors, and by varying conditions of temperature. The kinetic studies and the complex interaction between the sugars were characteristic of a carrier-mediated system maintained by metabolic energy. Glucose and fructose appear to have different sites of entry though each can influence the other. It is suggested that sucrose is hydrolyzed at the plasmalemma, glucose and fructose then entering the cells.
Cytology of Rosellinia mammiformis and R. aquila
Authors: Rogers Jack D. , Stiers D. L.
Published: September 2008

The chromosome number of Rosellinia mammiformis is n = 6. Ascospores are uninucleate when formed, becoming binucleate by mitosis. One of the nuclei degenerates; maturing ascospores are uninucleate. Ascospores show apical appendages that are proliferations of the outermost wall or perispore. The chromosome number of Rosellinia aquila is tentatively n = 6. Ascospores are at first uninucleate, becoming binucleate by a mitosis. One of the nuclei degenerates and is often cut off in an appendage. Maturing ascospores are uninucleate and show two types of appendages. Secondary appendages are formed from the perispore. Primary appendages are cut off from the spore body by a septum and are surrounded by the secondary appendage. In addition, a double primary appendage, part of which probably functions to trap a degenerating nucleus, is described. The significance of these results is discussed.
Keissleriella emergens, a perfect state of Diplodia tumefaciens in roots of poplar
Authors: Zalasky Harry
Published: September 2008

The perfect state of Diplodia tumefaciens (Keissleriella emergens (Karsten) Bose) is described from the infected roots of Populus balsamifera.
Local lesions as sources of biologically pure strains of tobacco mosaic virus
Authors: Boxall Mary , MacNeill B. H.
Published: September 2008

The integrity of the local-lesion technique in producing genetically homogeneous isolates of tobacco mosaic virus from Nicotiana glutinosa has been verified using strains doubly labeled with genetic markers governing symptomatology and host range.
Apparent stimulations of plant growth by air pollutants
Authors: Bennett James P. , Resh Howard M. , Runeckles V. C.
Published: September 2008

A survey of recent literature on the effects of low levels of air pollutants on plants, and the results of our experiments with low levels of ozone (< 0.1 ppm) on bean (Phaseolus vulgaris), barley (Hordeum vulgare), and smartweed (Polygonum lapathifolium) indicate stimulations of various growth parameters when compared with growth in clean, filtered air. Increasing knowledge of the composition of air in various regions of the world has been interpreted by some as evidence of increased air pollution. We argue that such a conclusion may not necessarily be valid, and that the observed levels of individual constituents may be indicative of long-term air composition. The similarity between the ambient levels of pollutants reported from numerous locations and those which result in stimulations of plant growth when compared with clean air, suggests that plants exhibiting such stimulations have adapted to low pollution levels, and hence are at a disadvantage when grown in clean air. We argue that the use of filtered air controls in experiments on the effects of air pollutants on plants is therefore unrealistic and misleading, and should be replaced by the use of ambient levels of pollution.
Verticillium wilt of chrysanthemum: relative water content and protein, RNA, and chlorophyll levels in leaves in relation to visible wilt symptoms
Authors: MacHardy William E. , Hall Robert , Busch Lloyd V.
Published: September 2008

Shifts in host metabolism during early stages of foliar infection and symptom development are examined. Verticillium dahliae Kleb. invaded and colonized chrysanthemum leaf tissue before symptom expression. Similar numbers of fungal propagules were recovered from non-symptomatic and symptomatic parts of a leaf lobe. No changes in relative water content, tissue permeability, RNA, and protein levels and only a slight decrease in chlorophyll level were detected within infected leaf tissue before the appearance of visible wilt. These data are discussed in relation to the possible role of senescence in the Verticillium wilt syndrome in chrysanthemum.
Juglans eocinerea n. sp., Beaufort Formation (Tertiary), southwestern Banks Island, Arctic Canada
Authors: Hills L. V. , Klovan J. E. , Sweet A. R.
Published: September 2008

A new fossil walnut, Juglans eocinerea sp. nov, very similar to the fossil Juglans tephrodes Unger and the extant butternut Juglans cinerea L., is described and illustrated based on nut specimens from the Beaufort Formation (Miocene?) on southwestern Banks Island. Extremely good preservation permitted the following external measurements: length, maximum width, maximum width to base, maximum thickness, maximum thickness to the base, and the internal measurements: seed length, seed width, maximum seed depth, divided width, length and width of the major septum, and wall thickness.In addition, ratios such as length to width, length to maximum width to base, length to height, length to distance from maximum height to base, length to seed length, seed length to width, length to length of major septum, and seed depth to height are calculated.These measurements were also made on the fossil J. tephrodes Ung., and the extant species J. nigra L. and J. cinerea L.Comparisons with modern and fossil forms indicate that the fossil is most closely related to the fossil Juglans tephrodes, but is also very similar to Juglans cinerea. It is suggested that the fossil is ancestral to both J. tephrodes and J. cinerea and that it explains the anomalous occurrence of the latter species in North America.
Nutrient limitations to plant production in two tundra communities
Authors: Haag Richard W.
Published: September 2008

Nitrogen and phosphorus nutrition were investigated as limiting factors to primary production in a lowland wet sedge meadow and an upland birch–willow–heath community.Response to nitrogen fertilization in both communities, including increased protein content and dry weight production, indicates that nitrogen supply limits production in both soils. In the upland community, phosphorus supply does not limit production, but in the lowland sedge meadow, dilution of the soil solution may decrease phosphorus availability and render this element limiting to production.Nitrogen, if available, can be taken up and metabolized into organic compounds despite low soil temperatures. Phosphorus metabolism may be directly limited by low soil temperatures and low available nitrogen levels.Low soil temperature exerts an indirect limitation on plant production through limitation of organic matter decomposition and microbial nitrification, thus limiting the rate of nitrogen cycling.The importance of a low nutrient regime in the Arctic may be seen in the widespread occurrence of xeromorphic characters in many taxa, which thus require minimal mineral nutrition to best use their photosynthetic capacity. The low nutrient regime may partially explain the high proportion of perennial plants in the Arctic, since these species can accumulate a nutrient pool over time from a deficient environment.
Developmental studies of the floret in Oryzopsis virescens and O. hymenoides (Gramineae)
Authors: Kiew Kam Yee
Published: September 2008

Development of the floret of Oryzopsis virescens and O. hymenoides was studied. Evidence from this study and from other studies on grass floret development has brought the following interpretations. Histogenesis of the lemma, palea, posterior lodicule, and gynoecial wall is similar, and indicates their foliar nature. They are determinate organs, have a shallow site of initiation, and exhibit marginal growth. The anterior lodicules differ from them in having a deeper initiation site. The interpretation of the anterior and posterior lodicules as reduced perianth structures of one whorl rather than as structures de novo is preferred. The callus is formed by the downward projection of the base of the lemma. Developmentally, the stamens are stem-like. The gynoecium consists of a unit ascidiform gynoecial wall surrounding a terminal ovule. There are two styles, each of which develops from a lateral portion of the gynoecial wall. The floret apex is not used up in the formation of the gynoecial wall. The residual floret apex develops into the ovule. The grass gynoecium may be considered acarpellate.
Growth kinetics of Marquis wheat. VI. Genetic dependence and winter hardening
Authors: Macdowall F. D. H.
Published: September 2008

An examination was made of the ability of the previously defined growth parameters to distinguish between Marquis and several other cultivars of wheat under controlled non-hardening (25 °C) and hardening (2–4 °C) temperature conditions. The spring wheats Marquis and Pitic were compared with the winter wheats Cappelle, Talbot, Rideau, and Kharkov. The maximum growth coefficient, kmL, for cv. Pitic significantly exceeded all others, those for Cappelle and Rideau were intermediate, and that for Talbot was lowest, but the range for winter wheats was not different from that for spring wheats at either temperature. Considerably reduced growth occurred under the lower temperature but neither the inverse relationship that is generally recognized to exist between plant growth and hardiness nor the recent evidence for growth in hardening tissues themselves were supported by any quantitative match between the growth parameters and freeze tolerance. It was concluded that the intrinsic growth coefficient, rather than the gross growth coefficient with its storage component, must be determined for correlation with hardening.
Liquid scintillation counting of 35SO42− and other ions in perchlorate digests of plant tissue
Authors: Peirson D. R.
Published: September 2008

An efficient, reliable, and economical technique is described which eliminates the problems associated with liquid scintillation counting of 35SO42−. Acid digests of plant tissue are prepared for application to either filter paper or glass fiber, which acts as a carrier in the scintillator solution. The digests are also suitable for the assay of a number of other radioactive and stable isotopes.
The determination of an efficient sampling intensity for studying beta diversity in plant communities
Authors: Hume L. , Day J. C.
Published: September 2008

The procedure described in this paper, when applied to data collected in a pilot study, enables determination of an efficient sampling intensity for studying beta diversity in a plant community. A statistic, Sβ, is introduced as a measure of beta diversity. The method can be applied where (1) many species are to be observed, (2) quadrat sampling is to be used, and (3) presence:absence data are desired.
Pathogenicity of variant strains of the wheat stem rust fungus isolated from axenic culture
Authors: Maclean D. J. , Scott K. J.
Published: September 2008

One dikaryotic variant and nine monokaryotic variants, which arose spontaneously from axenic cultures of Puccinia graminis Pers. f. sp. tritici Erikss. & E. Henn, were tested for pathogenicity on wheat. Four variants (including the dikaryon) were highly pathogenic, the remaining six showing little or no pathogenicity. Non-pathogenic variants produced no detectible necrotic reaction in the host. Pathogenic variants sporulated after infection of wheat, although the type of spore and their relative abundance varied widely between strains. Successful infection of detached leaves was always accompanied by formation of 'green islands' at the infection site. A histological and cytological study showed that wheat leaves infected with a pathogenic monokaryotic variant resembled wheat infected with wild-type (dikaryotic) rusts. The results are discussed in relation to host-pathogen compatibility.
Nitrogen fixation in the rhizosphere of freshwater angiosperms
Authors: Bristow J. Michael
Published: September 2008

Acetylene reduction by bacteria in the rhizosphere of Glyceria borealis and Typha sp. was studied under anaerobic and aerobic conditions. Under anaerobic conditions, when roots and rhizomes were incubated with rhizosphere sediments at 25 °C without glucose, acetylene reduction to ethylene was calculated to be 37 μmol g−1 day−1 and 3.6 μmol g−1 day−1 for Glyceria and Typha respectively. The rates were generally lower under aerobic conditions. Washed roots (without sediment) also showed high activity. The reduction of acetylene to ethylene had a Q10 of 4.5 in the Glyceria system. It is estimated that N2 fixation in the rhizosphere of this species may reach 60 kg ha−1 year−1.
Seed infection and latent infection of sunflowers by Plasmopara halstedii
Authors: Cohen Yigal , Sackston W. E.
Published: September 2008

Sunflowers bud-inoculated with Plasmopara halstedii became systemically infected with downy mildew and produced infected seeds at 15 to 30 °C. Oospores were observed in seeds of inoculated and also naturally infected plants from the field. Infected seeds gave rise to symptomless plants. Infected seeds proved effective as inoculum, inducing infection in 14 to 89% of the plants inoculated at 20 °C. Most of the infections (80%) were symptomless (latent).Systemic infection occurred, but latent infection was more frequent, in plants grown in soil containing debris of mildewed plants. Latent infection also occurred in uninoculated plants through belowground contact with systemically infected plants. Seed produced by plants with latent infection may carry the pathogen, and may give rise to more plants with latent infection, accounting for widespread dissemination of the disease before plants with typical symptoms are observed.
The role of cotyledons in growth and development of woody angiosperms
Authors: Marshall P. E. , Kozlowski T. T.
Published: September 2008

The role of photosynthetically active cotyledons in the growth of young woody angiosperm seedlings was studied over a 35-day period under controlled environmental conditions. Two experiments were performed. In the first, cotyledons of Robinia pseudoacacia, Ulmus americana, and Ailanthus altissima were removed or covered at 7, 14, or 21 days after seedling emergence. In the second experiment, seedlings of Robinia pseudoacacia, Betula alleghaniensis, and Acer saccharum were grown over a range of light intensities. Removing or covering Robinia cotyledons of seedlings of any age resulted in lower dry weights of roots and stems than in controls. Removing or covering cotyledons of only 7-day-old Robinia seedlings retarded dry weight increase of foliage. Robinia seedling heights were unaffected by cotyledon covering or removal. Covering Ulmus americana cotyledons had no significant effect on dry weight increment of stems or foliage or on seedling height. Removal of Ulmus cotyledons from 7-day-old seedlings inhibited dry weight increase of roots, stems, and leaves and inhibited height growth. Removal of Ailanthus cotyledons inhibited dry weight increment of roots, stems, and leaves more than did covering of cotyledons. Species varied greatly in cotyledon development and response to light intensity. Cotyledon size was affected by light intensity in Robinia, but not in Betula or Acer. Responses of cotyledons to light intensity differed from those of foliage leaves. Cotyledon photosynthesis appeared to have a very important role in seedling growth in Robinia and Ailanthus and a less important role in Ulmus.
Ultrastructure of callus tissue of Zea mays
Authors: Johnson Judy W. , Holden David J.
Published: September 2008

Corn coleoptile nodal tissue was used to study the callusing of corn inbred and hybrid varieties. A comparison of callus cells and coleoptile parenchyma cells was made with electron micrographs. The callus cells resembled meristematic cells in having more ribosomes, and had a greater number of mitochondria and plastids than nodal parenchyma cells. There was a high incidence of lomasome-like bodies in both types of cells. The callus cells were characterized by having small vacuoles scattered throughout the cell, whereas the nodal parenchyma tissue was composed of cells with mostly a single large vacuole surrounded by a thin parietal cytoplasm.
Light effects on fruiting in Panus tigrinus var. tigrinus
Authors: Bobbitt Thomas F. , Crang Richard E.
Published: September 2008

In the Basidiomycete Panus tigrinus var. tigrinus, continuous fluorescent light results in increased production of numbers of abnormal fruiting bodies. With progressively longer dark periods before continuous light there is a decrease of abnormal fruits. The total number of fruiting bodies remains relatively constant regardless of light/dark treatment. However, no fruiting occurs under conditions of total darkness. Differentiation between normal and abnormal fruiting bodies begins after light exposure, and the normal primordia develop a dark pigmentation near the tip. Such pigmentation is believed to be significant in inducing normal basidiocarps.
Gibberellic acid induced elongation of lettuce hypocotyls and its inhibition by colchicine
Authors: Sawhney V. K. , Srivastava L. M.
Published: September 2008

Lettuce (Lactuca sativa L.) seedlings treated with gibberellic acid (GA) for 72 h produced hypocotyls 600% longer than the water controls. The process of elongation was accelerated by GA. Also, for maximum elongation, presence of GA was not necessary after 20 h. Short term treatments of seedlings with GA indicated that the seedlings were most 'sensitive' to GA after 8 h of growth in water. Colchicine inhibited the GA-induced elongation. Its effect was maximal if it was applied within the first 2 h after GA treatment irrespective of the stage of hypocotyl development; the inhibition was progressively lessened after 2 h and lost after 36 h. These kinetic data are presented together with measurements of hypocotyl cell lengths and widths and provide a basis for correlated ultrastructural studies.
Release of peroxidase from soybean hypocotyl cell walls by Sclerotium rolfsii culture filtrates
Authors: Barnett Neal M.
Published: September 2008

Up to 24% of the peroxidase of purified cell walls of soybean hypocotyls was released by incubation of cell walls with hydrolytic enzymes secreted by the fungus Sclerotium rolfsii. This estimate is based on comparison of peroxidase activity recovered in the medium with peroxidase activity in unincubated cell walls, estimated by a new assay. The peroxidase-release reaction occurs at 0 °C at half the rate at 30 °C. The peroxidase-release reaction occurs almost equally fast in the pH range of 3.5 to 8.0. The release of peroxidase from cell walls cannot be attributed solely to arabanase, polygalacturonase, or cellulase in the culture filtrate, although on Sephadex G-75 chromatography these activities overlap the peroxidase-releasing activity. Culture filtrate released less than 5% of the hydroxyproline protein of the cell walls.
The origin of Trifolium lupinaster (Leguminosae) in Alaska
Authors: Murray David F. , Drury Horace F.
Published: September 2008

Evidence suggests that previous activity of the Alaska Agricultural Experiment Stations is responsible for the disjunct occurrence of T. lupinaster in North America at three widely separated localities in Alaska.
Deux nouvelles espèces de levures isolées de la phyllosphère de l'Orge
Authors: Miranda L. Rodrigues de , Diem Hoang G.
Published: September 2008

Two new species of Candida Berkhout are described from the phyllosphere of barley.
Isozymic changes in relation to root initiation in mung bean
Authors: Frenkel Chaim , Hess Charles E.
Published: September 2008

Mung bean (Phaseolus aureus Roxb.) cuttings were used to study enzyme changes during root initiation. Gel electrophoresis of protein extracts from the hypocotyl tissue revealed the emergence of a major protein complex during the early stages of root initiation. This protein fraction showed multiple enzymatic function including polyphenol oxidase, peroxidase, and indole-3-acetic acid oxidase. Two root-promoting substances, indoleacetic acid (IAA) and catechol, enhanced the activity of the protein complex during the early stages of root initiation. The significance of this isozymic activity with respect to the modulation of rooting promoting factors is discussed.