bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies of the infection of lupin leaves by Pleiochaeta setosa
Authors: Harvey Ian C.
Published: September 2008

The penetration and establishment of Pleiochaeta setosa in lupin leaflets was studied with light microscope and scanning and transmission electron microscopes. Healthy lupin leaves were also studied at the ultrastructural level. Conidium germination, appressorium formation, and host penetration were found to take place non-synchronously, and the method of penetration of the pathogen through either the cuticle or stomata was determined by the method of inoculation. Disease symptoms were manifested 17 h after inoculation. The ultrastructure of stomatal penetration involved the formation of no specialized structures. Appressoria adhered to the host surface by means of adhesion blocks which penetrated the wax layer. Penetration through the cuticle was by a thin-walled infection peg that expanded below the cuticle to form a swollen infection hyphae from which hyphae ramified indiscriminately throughout the host. It is suggested that extracellular enzymes diffused in advance of the invading pathogen. The ultra-structure of the host reaction is described together with that of the invading fungus.
Formation of microsclerotia and chlamydospores from conidia of Alternaria brassicae
Authors: Tsuneda A. , Skoropad W. P.
Published: September 2008

Conidia of Alternaria brassicae are transformed into microsclerotia on some naturally infected, partially decayed rapeseed leaves stored at 3 °C in the dark. On V-8 juice agar medium, formation of microsclerotia occurs after 2-week-old cultures are exposed to 3 °C for at least 6–10 days. When rose bengal is added to the medium, growth is restricted and the transformation of conidia into microsclerotia is also initiated during gradual desiccation. Mature microsclerotia are darkly pigmented, many-celled, unevenly spheroidal, and about 60–150 μm in diameter. Microsclerotia are resistant to desiccation and freezing. On a 1% malt extract solution, germination of frozen–thawed microsclerotia results almost exclusively in the direct production of conidiophores and conidia, and germination of untreated microsclerotia results primarily in the production of germ tubes that extended into hyphae.Chlamydospores also form within conidium cells after cold temperature (3 °C) treatment or during gradual desiccation in cultures. Conidia placed on natural soil at room temperature become empty or form endocellular chlamydospores.
Studies on Gracilaria. 5. In vitro life history of Gracilaria sp. from the Maritime Provinces
Authors: Bird N. , McLachlan J. , Grund D.
Published: September 2008

The life history of Gracilaria sp. was completed in culture demonstrating a typical Polysiphonia-type life history. Carpospores released by plants collected in nature developed into tetrasporophytes and subsequent release and germination of tetraspores gave rise to a gametophytic generation morphologically similar to the tetrasporophyte. Development of tetrasporophytes from carpospores released by the carposporophytic generation completed the life history. A male to female ratio of 1:1 was found for plants originating from tetraspores and only female plants grown in the presence of male plants formed fertile cystocarps. Detached plants showed the greatest reproductive potential; reproductive maturation of these plants occurred in 8–10 weeks after spore germination. Vegetative propagation through rapid regeneration of adventitious branches from wound tissue was observed.
Canavanine utilization by Phytophthora sp.
Authors: Weaks T. E. , Binder F. L.
Published: September 2008

Three isolates of Phytophthora that are pathogens of legumes and three that are nonpathogens were tested for sensitivity to L-canavanine. Growth of only one pathogen was affected by this amino acid. Phytophthora megasperma var. sojae race 1 was inhibited by canavanine when cultured in the basal medium. When starved mycelium of this isolate was treated with canavanine, total uptake of [H3] uridine and L-[H3] leucine and incorporation of these labeled compounds into insoluble fractions of trichloroacetic acid were enhanced. This demonstrated that under these conditions, canavanine supported some synthetic processes in the fungus.Of the Phytophthora sp. tested that are nonpathogens of legumes, one was affected by canavanine. Growth of P. cactorum was enhanced to a low degree. When asparagine (1.5 × 102 M) was replaced by canavanine (1.8 × 10−4 M) in the basal medium, growth was significantly higher than that in the asparagine-deficient basal medium. Labeling experiments with P. cactorum demonstrated that canavanine enhanced incorporation of [H3]uridine and L-[H3]leucine into insoluble fractions of trichloroacetic acid. Phytophthora cactorum apparently detoxifies canavanine and utilizes it in growth-supporting activities.
An ultrastructural analysis of the changes in organelle arrangement and structure between the various spore types of Saprolegnia
Authors: Holloway Shirley A. , Heath I. Brent
Published: September 2008

Serial-section analysis of synchronous spore populations of a species of Saprolegnia show that the organelles of primary and secondary zoospores undergo a sequence of changes in both arrangement and morphology during the change from motile spores to cysts and vice versa. The morphological changes include elongation and shortening of mitochondria, reversible stacking of endoplasmic reticulum cistemae, and formation and use of bars and newly described K bodies. These observations show that considerable synthetic and assembly activity occurs in the various spore stages. All organelles remain in characteristic locations in the motile spores but most become randomly arranged in the cysts, thus demonstrating the existence of some unsuspected and as yet undefined morphogenic cytoplasmic components. The functional implications of the described changes are discussed.
Porphyrin and peroxidase synthesis in cultured peanut cells
Authors: Huystee R. B. Van
Published: September 2008

The activity of 5-aminolevulinic acid synthetase (δ-aminolaevulinate synthase, EC 2.3.1.37) in achlorophyllous peanut cells in suspension culture was determined in the presence of 1 mM levulinic acid. It never exceeded 10% of the activity in green tissue. A feedback inhibition by protoheme may be the cause of low enzyme activity. The concentration of protoheme was 10- to 20-fold greater in these cultured cells than in leaves. The pool of protoheme was shown to act as a reservoir for peroxidase synthesis. This synthesis continued for 48 h in the presence of levulinic acid. The heme prosthetic group of peroxidase was only slowly labelled during the feeding with [14C]5-aminolevulinic acid.
Mycorrhizae of Abies concolor in California
Authors: Alvarez Isabel F. , Cobb Jr. Fields W.
Published: September 2008

Nine different types of mycorrhizae were observed on naturally occurring white fir seedlings in the north central Sierra Nevada, including one formed by the ubiquitous Cenococcum graniforme. The macro- and micro-scopic characteristics and reactions to different chemical reagents are described for five types. Possible mycorrhizal fungi of white fir are listed. Nursery-grown seedlings examined were ectomycorrhizal; intracellular penetration was not observed. None of the naturally occurring mycorrhizal types were found on nursery seedlings.
Herbicide tolerance developed in cell suspension cultures of perennial white clover
Authors: Oswald T. H. , Smith A. E. , Phillips D. V.
Published: September 2008

Cell suspension cultures of perennial white clover (Trifolium repens L. cv. Regal Ladino) were selected for tolerance to the phenoxy analogs (2,4-dichlorophenoxy)acetic acid (2.4-D), 2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), and 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB). Cells demonstrating up to 6.2-fold increase in tolerance to 4 μg/ml 2,4-D, 7.7-fold increase in tolerance to 8 μg/ml 2,4,5-T, and 3.0-fold increase in tolerance to 2 μg/ml 2,4-DB were obtained within 5 days under the selection procedures. The selection pressures were the phenoxy analogs applied at phytotoxic levels. Whereas the cells that survived each pressure subsequently demonstrated tolerance to all analogs, the cells selected with 2,4-DB as the pressure were more tolerant to all three analogs than were cells selected with 2,4-D or 2,4,5-T. Tolerance, thus gained, was transmitted through succeeding asexually propagated cell generations.
Anatomical and histochemical changes in germinating seeds of Pinus radiate treated with Tordon herbicides
Authors: Ayling R. D.
Published: September 2008

Tordon 22K (picloram) and Tordon 50D (1 part picloram + 4 parts 2,4-dichlorophenoxyacetic acid) did not affect the germination of Pinus radiata seeds, but seedlings developed flaccid cotyledons, reduced in length in some instances, and elongated and twisted in others. Hypocotyls and radicles were swollen and reduced in length.Cell vacuolation was extensive in treated embryos, and epicotyls appeared less conical compared with the controls, possibly as a result of reduced cell expansion and alterations in the normal plane of division. In the lower hypocotyls-root tissues, an area of proliferating small-diameter cells formed as a result of rapid and aberrant cell divisions and the failure of these cells to expand normally.Starch and lipid metabolism were reduced in treated tissues, especially in the small cell area. Protein bodies were present in all cells of the embryos and were apparently unaffected by herbicide treatment. RNA content appeared to be greater in cytoplasm of cells in the sheath of small cells and the nucleoli of cortical cell nuclei were enlarged, especially in tissues treated with Tordon 50D.It is suggested that both herbicides acted similarly to induce aberrations in the normal plane of cell division, possibly by altering nucleic acid metabolism.
A new technique for the study of floral histology and morphogenesis: tissue strips made from orientated and cleared thick microtome sections
Authors: Ritterbusch A.
Published: September 2008

The technique allows one to obtain orientated microtome sections from a large or small sample as well as a tissue strip in the area adjacent to the microtome section from the same sample. The strip can be handled like a whole mount, and the different cell layers can be viewed by differential interference-contrast (Nomarski) microscopy. The strip in combination with the available microtome sections gives a total picture of the tissues in question. The technique offers great advantages in many developmental or purely histological studies, especially in the study of complicated dorsiventral flowers, as demonstrated by our example.
Embryogenesis and plant regeneration in Brassica napus anther cultures
Authors: Keller W. A. , Armstrong K. C.
Published: September 2008

Anthers of two cultivars of Brassica napus were cultured on a medium previously used for B. campestris but modified with the addition of 100 mg/ℓ L-serine. The frequency of embryogenic anthers obtained was about 1%. Transfer of anthers from a 10% to a 2% sucrose level after 1- and 2-week culture periods failed to increase the number of embryos obtained and did not result in the production of embryos capable of direct development into plantlets. Although most embryos obtained in this study lacked the ability to develop a shoot system, plants were recovered by inducing shoot formation on hypocotyl expiants cultured on a cytokinin-containing medium.A total of 31 plants were regenerated, 9 of which were examined cytologically and found to be diploid. triploid, or tetraploid. Evidence for the microspore origin of the plants was accumulated and possible mechanisms of diploidization and polyploidization were considered.
Variation of Polyporus tomentosus in cultural characteristics and pathogenicity on conifer seedlings
Authors: Whitney R. D. , Bohaychuk W. P.
Published: September 2008

Polyporus tomentosus Fr. cultures newly isolated from wood showed faster growth rates, greater chlamydospore numbers at 20 °C, higher average oxidase reactions, and higher disease ratings on seedlings of white spruce and Norway spruce than did cultures maintained on artificial media for 1 year or longer.Data from 30 isolates were analyzed for 63 characters using a principal components analysis as an ordination technique. Variables which had considerable influence on the ordination were pathogenicity on seedlings, isolate growth rate, chlamydospore production, and mat color on artificial media. Pathogenicity was higher among isolates from sporophores with straight setae than among those from sporophores with strongly curved or hooked setae (P. tomentosus var. circinatus F. sensu Haddow).Low pathogenicity on seedlings is an additional character associated with P. tomentosus var. circinatus Fr. which Haddow (Br. Mycol. Soc. Trans. 25: 179–190) separated on the basis of curved setae in the hymenium. Straight setae were always associated with stipitate sporophores and curved setae consistently occurred on sessile sporophores.
The alpine flora of Teresa Island, Atlin Lake, B.C., with notes on its distribution
Authors: Buttrick Steven C.
Published: September 2008

A comprehensive inventory of the vascular plants is provided for the alpine zone of Teresa Island in Atlin Provincial Park, British Columbia. A total of 161 taxa were identified from collections made during a research program conducted in the summers of 1974, 1975, and 1976. Of these taxa Arnica louiseana var. frigida, Draba lactea, Lupinus kuschei, Oxytropis huddelsonii, Poa lettermanii, Senecio sheldonensis, Senecio yukonensis, and Stellaria longipes var. edwardsii have a restricted or otherwise interesting distribution in British Columbia.Preliminary observations indicate that the local distribution of all the taxa is controlled by three environmental gradients: snow duration, moisture, and topography. Five different alpine habitat types are recognized as a result of different combinations of these gradients. These habitat types are (1) fell-fields and boulder fields, (2) meadows and shrub fields, (3) snow beds, (4) seepage sites, and (5) drainage areas. The habitat types and relative abundance of each taxon are listed.
Effect of soil temperature on the pathology of Alternaria radicina on carrots
Authors: Benedict W. G.
Published: September 2008

The temperature of muck soil infested with Alternaria radicina Meier, Drechsler, and Eddy was found to have a marked effect upon the severity of root dieback or rusty root of carrots, Daucus carota L. When the surface of steam-sterilized muck soil was artificially reinfested with as few as 50 spores of A. radicina per square centimetre, less than 1% emergence occurred below 18 °C in controlled soil-temperature experiments. In muck soil naturally infested with A. radicina, carrot seedling emergence over the whole range of temperatures, 10–28 °C, was little more than half that obtained in steam-sterilized similar soil. The severity of root dieback increased sharply with decreasing temperature below 18 °C in both artificially reinfested and naturally infested soil. Alternaria radicina was found actively growing on carrots in naturally infested soil at and below 16 °C, but, when similar soil was steam sterilized and artificially reinfested after seedling emergence, A. radicina infected the young carrots in soil up to 26 °C. Alternaria radicina was consistently isolated both from carrots with symptoms of root dieback or rusty root and from the muck soil in which the carrots had been grown and had produced symptoms of root dieback or rusty root. An analysis of variance of the root weight data of the five cultivars of carrots used showed that the effect of soil temperature was independent of the effect of the infested soil on root growth. A multivariate analysis of variance affecting all means of root weight of the five cultivars showed that, in general, any selected number of carrot cultivars would each vary in root weight according to the soil temperature and to the infested soil significantly and independently.
The origin of Dryopteris campyloptera
Authors: Gibby Mary
Published: September 2008

In an attempt to establish the origin of the North American tetraploid Dryopteris campyloptera, hybrids have been synthesized and the chromosome pairing at meiosis investigated. It seems probable that it is derived from two diploid species, D. assimilis and D. intermedia. Dryopteris austriaca, a tetraploid species from Europe, is derived from the same diploid species but it may well have had an independent origin.
Young plastids in shoot apical cells of a genetic albino strain of Nicotiana (Solanaceae)
Authors: Susalla Anne A. , Mahlberg Paul G.
Published: September 2008

The ultrastructure of young plastids in shoot apices of a genetic albino strain of Nicotiana was examined by transmission electron microscopy. Typical young plastids were variable in shape and contained prolamellar bodies in various stages of organization. Thylakoids were few in number, some originating from the prolamellar body while others appeared free in the densely ribosomal stroma. Peripheral areas of the young plastids contained electron-transparent vesicles and tubules which were either in proximity or connected to the inner plastid envelope. Osmiophilic globules occasionally occurred in association with prolamellar bodies. Relatively large starch grains were common; cytoplasmic invaginations into the plastids were less common. Young plastids in the genetic green shoot apex closely resembled those of the genetic albino. These results indicate that organization of large-type grana in plastids of mature phenotypically green, genetic albino leaves occurs beyond the apex stage of germinated seedlings of this strain of Nicotiana.
Winter and spring changes in the microsporogenous cells of the Scotch pine as revealed by Feulgen photometry and Auramin fluorometry
Authors: Kupila-Ahvenniemi Sirkka
Published: September 2008

Sporogenous cells of Scotch pine microsporangia were separated from the other tissues of the strobilus. This made it possible to spread them on slides as a one-cell layer for cytophotometric studies. Feulgen photometry using Schiff s reagent showed that during the overwintering period the DNA level of these cells remained more or less constant. The nuclei in a microsporangium were not fully homogeneous in size and stainability. DNA synthesis occurred in the spring, preceding and overlapping the cell divisions that led to the formation of pollen mother cells. Auramin fluorometry showed that in spite of the steadiness of the DNA quantity, the sporogenous cells were not in a state of complete rest during the winter. Their stainability fluctuated so that it increased during the middle of the winter, reached a peak in February, and then dropped. Higher dye attachment was seen again in the May material. The factor(s) causing the wintertime fluctuation is unknown at the present.
Histological studies on host-cell necrosis conditioned by the Sr6 gene for resistance in wheat to stem rust
Authors: Samborski D. J. , Kim W. K. , Rohringer R. , Howes N. K. , Baker R. J.
Published: September 2008

Seedlings of resistant (Sr6) and susceptible (sr6) near-isogenic lines of wheat (Triticum aestivum L.) were inoculated with a race of stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn.) that was avirulent on the line with Sr6 and they were kept at 19, 25, 26, and 27 °C. Fluorescence microscopy was used to detect autofluorescing necrotic host cells and rust colonies after these were stained with a fiuorochrome (Calcofluor White M2R New).In leaves containing the Sr6 gene, a smaller percentage of colonies grown at 25 °C had necrotic cells associated with them than those that were grown at 19 °C. The incidence of colony-associated necrosis in these leaves could be further reduced by increasing the temperature to 26 °C and 27 °C. Similarly, the number of necrotic host cells per colony decreased with an increase in temperature. Colonies in genotypically resistant leaves were usually smaller than those in genotypically susceptible leaves, but the differences in colony sizes between these two lines decreased at the higher temperatures.When infected plants containing the Sr6 gene were kept for varying times at 25 °C and then were transferred to 19 °C, there was significantly less fungal growth and more necrosis than in plants kept continuously at 25 °C. This necrosis occurred largely in those cells that were invaded after the transfer to 19 °C, when the Sr6 gene was activated.
The combined effects of temperature, leaf wetness, and inoculum concentration on infection of cucumbers with Pseudoperonospora cubensis
Authors: Cohen Yigal
Published: September 2008

The infection of susceptible cucumber leaves by Pseudoperonospora cubensis was investigated under controlled conditions in a 6 × 3 × 4 factorial experiment with 72 combinations of temperature, inoculum concentration, and leaf-wetness duration. The minimum, maximum, and optimum levels of each factor for symptom production were found to depend on one or both of the other factors. The minimal temperature for infection was 20 °C with 2 h of wetness and this decreased to 10–15 and 5–10 °C with 6 and 12 h of wetness, respectively, according to the inoculum load. The maximal temperature for infection was 25 °C, except for a single treatment in which some infection occurred at 28 °C. Optimal temperatures for infection were 20, 15–20, 10–20, and 5–20 °C at dew periods of 2, 6, 12, and 24 h, respectively. The shortest dew period needed to establish infection was 2 h. A sharp increase in infection was associated with extending the dew period to 6h. Further lengthening of the dew period resulted in more infection under unfavorable combinations of temperature and inoculum concentration. An inoculum load of 10 sporangia/cm2 was minimal for infection under favorable combinations of temperature and wetness, and higher loads were needed under unfavorable combinations. The optimal inoculum concentration was 1000 sporangia/cm2 under most inoculation circumstances. The implications of the variable behaviour of the pathogen to disease development in the field are discussed.
Mesophyll cell walls in hemlock, Tsuga canadensis
Authors: Fischer R. , Dengler N. G.
Published: September 2008

Observations have been made on the walls of the mesophyll cells in the leaves of hemlock, Tsuga canadensis, to determine if there were any structural features which would account for the relatively high resistance measured at the mesophyll cell surface in infiltrated leaves by Tyree et al. (1975). There was no indication of an internal cuticle based on histochemical tests of fresh sections and the appearance of the wall in electron micrographs. Examination of Alcian-blue-stained fresh sections and thin sections of material treated with ruthenium red indicated that mesophyl) cell walls may be covered with a mucilaginous layer that retards the evaporation of water to intercellular spaces.
Electron microprobe analyses of salt distribution in the halophyte Salicornia pacifica var. utahensis
Authors: Weber D. J. , Rasmussen H. P. , Hess W. M.
Published: September 2008

The halophyte Salicornia pacifica var. utahensis grows in the desert saline playa. The fused leaves form succulent stems and have apparently isolated tracheids in the palisade region as observed by scanning electron microscopy. Frozen shoots were fractured under liquid nitrogen and scanned for Na+, K+, and Cl− with an electron microprobe X-ray analyzer. In young shoots, the palisade cells were low in salts, and the spongy cells had higher concentrations. The salt in the spongy cells provides a high osmotic pressure permitting the plant to absorb more water from the soil. As the shoots matured, the concentration of salts increased in the spongy cells, and the amount of salt in the palisades also increased. The salt ions in the palisades were excluded from the organelles and were mainly present in the vacuoles. Eventually, the leaf section collapsed because of the high salt in the palisade and spongy cells, but the vascular region in the shriveled section continued to function. The sections adjacent to the dead shriveled section remained green and succulent. The salt tolerance appeared to be based on the exclusion of the salt from the photosynthetic cells and on the ability of the succulent stem to function even though sections were dead owing to high salt concentration.
Slow leaf rust development on durum wheat
Authors: Statler G. D. , Nordgaard J. T. , Watkins J. E.
Published: September 2008

Several durum wheat (Triticitm durum) cultivars exhibiting susceptible or moderately susceptible reactions to the leaf rust fungus (Puccinia recondita tritici) were evaluated for slow rusting. Percentage severity and reactions for P. recondita tritici on each cultivar were evaluated periodically after initial infection. Logit analysis of disease progress curves was used to compare cultivars. The durum wheats consistently exhibited low rust severities in the field. The durums were always characterized by lower infection rates than the susceptible bread wheat cultivar Thatcher (Triticum aestivum). The area under the disease progress curve was smaller for the durum wheats than for Thatcher. The high correlation between apparent infection rate and the final rust severity indicated that final rust severity could be used as an indication of infection rate. The high correlation coefficient for the apparent infection rate between the two top leaves indicated that either leaf would provide an accurate evaluation of the cultivar. Yields of the durum wheat cultivars were not increased by controlling leaf rust. Yields of the susceptible bread wheat cultivar Thatcher were significantly increased by controlling leaf rust. The slow rusting displayed by the durum wheat cultivars studied apparently provide adequate protection against leaf rust under North Dakota conditions.
The relative decomposition potential of habitats variously affected by surface coal mining
Authors: Lawrey James D.
Published: September 2008

In a 20-year-old abandoned surface coal mine area in eastern Ohio, fiber glass litter bags containing leaves of Robinia pseudoacacia, Pinits resinosa, and Acer rubrum were set out in three habitats: a non-vegetated strip-mined area, a strip-mined area dominated by Robinia pseudoacacia, and an adjacent unstripped area dominated by Fagus grandifolia and Acer saccharum. From 1 to 6 months after litter fall, there were statistically significant differences in Robinia and Acer leaf litter dry weight between the bare strip-mined habitat and either of the vegetated habitats, both strip-mined and unstripped. After 6 months of decomposition time, rates of decomposition based on dry weight loss became equalized for all litter types in all habitats except for Robinia leaves between the non-vegetated and the vegetated strip-mined habitats. This indicates that changes in decomposition potential because of strip-mining influence the early stages of litter decay. Calculated values for soil pH, texture, organic carbon content, and trace element content indicated that soils from strip-mined habitats contained greater levels of heavy metal cations and were more acidic. Soils from the control area unaffected by mining contained high percentages of sand-sized particles and low concentrations of trace elements, including metals. Soil respiration data measured by manometric techniques in January and April showed significant differences between the strip-mined habitats and the unaffected habitat. In addition, numbers of soil fungi isolated from soil samples of each habitat were higher in the unstrippedcontrol area than in either of the strip-mined areas. Leaf litter decomposition processes appear to be functionally more resistant to environmental impact than is apparent when structural diversity and complexity of soil populations are considered.
Plant-insect relationships between common milkweed Asclepias syriaca (Gentianales: Asclepiadacees) and the European skipper Thymelicus lineola (Lepidoptera: Hesperiidae)
Authors: McNeil Jeremy N.
Published: September 2008

European skipper adults aggregate on common milkweed and their legs and (or) proboscis often become entangled in the flowers. Occasionally this results in the loss of legs or in the death of the insect. Normally the insects escape unharmed and frequently carry with them milkweed pollinia, attached to the extremity of their tarsi. Thus the European skipper, an insect pest, may act as a pollinating agent of a weed pest, the common milkweed.
The Endomycetaceae: new concepts, new taxa
Authors: Redhead Scott A. , Malloch David W.
Published: September 2008

The Endomycetaceae is redefined and expanded to include yeasts and fungi bearing ascocarps or ascophores but is restricted to genera producing either galeate ascospores or other characteristics indicating affinities to the central genus Ceratocystis. The genus Endomyces is emended and a neotype is selected for the type species, E. decipiens. Endomyces cortinarii sp. nov. and Phialoascus borealis gen. et sp. nov. are described. A key to the genera admitted to the Endomycetaceae and listed below is included: Ambrosiozyma, Amorphotheca, Ascoidea, Botryoascus, Cephaloascus, Ceratocystiopsis, Ceratocystis, Endomyees, Europhium, Hansenula, Hormoascus. Pachysolen, Ophiostoma. Phialoascus, and Stephanoascus. Zendera gen. nov. (Schizosaccharomycetaceae) and Galactomyces gen. nov. (Onygenaceae) are described. The following new combinations are made: Zendera tetrasperma (Macy et Miller) comb, nov., Z. ovetensis (Peláez et Ramirez) comb, nov., Galactomyces geotrichum (Butler et Petersen) comb. nov., G. reesü (van der Walt) comb, nov., and Magnusiomyces magnusü (Ludwig) comb. nov.
Taxonomy of the tribe Triticeae (Poaceae) using various numerical techniques. I. Historical perspectives, data accumulation, and character analysis
Authors: Baum Bernard R.
Published: September 2008

A taxonomic study of the Triticeae at the generic level is needed for both practical and theoretical purposes. Many genera in this tribe contain species of prime importance to agriculture. It appears from many previous studies in many different disciplines, that the genera are very close to each other so that there are difficulties in properly defining them; but this very fact brings all the members of that group up to a high degree of importance for gene transfer purposes because of their close evolutionary relationships.The first paper in this series deals with the definition of 45 characters and their states, and evaluates their interrelationships and relative degree of importance for classificatory and diagnostic purposes. This is done through examination of conventional and new characters, and scrutinous verification of characters used hitherto by different authors in different areas at various times in the last 100 years. Analysis of the data was done using Estabrook's information theoretic model of character analysis and various other techniques, such as multidimensional scaling, principal component analysis, and clustering. It is concluded that no necessary correlation exists between the usefulness of a character for discriminating a particular genus and the value of the same character for distinguishing genera in the tribe and classifying them.
Embryology of Festuca microstachys (Gramineae)
Authors: Maze Jack , Bohm Lesley R.
Published: September 2008

As the ovary wall develops, some similar events are seen in the dorsal and upper portions. These are as follows: (1) the deposition of many starch grains in most of the ground meristem cells; (2) considerable cell growth in most of the ground meristem cells; (3) the development of a thick outer wall on the outer protoderm of the ovary; and (4) elongation in the protoderm cells lining the inner part of the ovary. Unlike the upper ovary wall, starch grains appear in the outer protoderm cells of the dorsal ovary wall. A cytoplasmically dense layer of cells subjacent to the inner protoderm of the dorsal ovary wall continues to undergo cell division when other ground meristem cells are enlarging. This layer of cytoplasmically dense cells is the only recognizable layer in the ovary wall when the seed is mature. The ovule is bitegmetic, hemianatropous, and tenuinucellate. Integuments are protodermal in origin and both are mostly two cells thick. Cell division is more prolonged in the inner than in the outer integument and the inner layer of the inner integument develops safraninophilic granules in the cytoplasm of its cells. The outer integument is stretched and obliterated before the inner. As a result of faster growth in the basal end of the nucellus, the ovule undergoes a change in orientation from orthotropous to hemianatropous. Periclinal divisions are rare in the nucellar protoderm. The nucellus is eliminated by the time that the seed is mature. Megagametophyte development is normal and callose is associated with megaspores. Unlike most grasses, only three antipodals form but each antipodal is large and contains what appear to be many atypical nuclei. The endosperm initially lacks cell walls but they appear later in development. When the endosperm is cellular, its surface layer is meristematic. Starch grains are numerous in the endosperm cells and the cells have thick walls. The thick walls are a possible source of stored energy. A cuticle on the surface of the endosperm may serve a protective function. Different types of grass ovules are the result of different degrees of the same developmental phenomenon at comparable sites. Relationships as determined by cluster analysis of a similarity matrix based on detailed embryological data show that four members of the tribe Stipeae cluster together and this cluster is separate from a cluster consisting of F. microstachys and Agrostis interrupta. Furthermore, the degree of similarity between the four stipeae was higher than that between F. microstachys and A. interrupta. This correlates well with the modem opinion that Festuca and Agrostis are in separate tribes.
Reduction in the transmissibility of a greenhouse-maintained isolate of aster yellows agent
Authors: Chiykowski L. N.
Published: September 2008

A celery-infecting isolate of aster yellows agent (isolate A), maintained in the greenhouse since its isolation from the field in 1958, was found to be significantly less transmissible by the aster leafhopper. Macrosteles fascifrons (Stål) than a similar isolate (isolate B) obtained from the same area in 1972. The difference in transmissibility was greatest in male insects, especially those given acquisition access periods as adults. Transmission of isolate A was increased to equal that of isolate B when leafhoppers were injected with inocula prepared from inoculative leafhoppers. No differences were found between isolates in their incubation periods in plants and insects or in their ability to infect asters. On the basis of earlier data and present findings, it is suggested that isolate A has undergone a change in transmissibility during its maintenance in plants grown under artificial conditions.
Role of toxins in etiology of root rot disease of wheat
Authors: Pringle Ross B.
Published: September 2008

Although no host-specific toxin, nor a great quantity of any toxic substance, has been found in culture filtrates of 26 different isolates of Helminthosporium sativum, the amount of the toxic metabolite, victoxinine, produced by these strains, may be correlated generally to their aggressiveness towards wheat.
Peridial composition of white fructifications in the Trichiales (Perichaena and Dianema)
Authors: Schoknecht Jean D. , Keller Harold W.
Published: September 2008

The nature of the peridial deposits in the genus Perichaena and in a species of Dianema has been defined by a combination of scanning electron microscopy, x-ray microanalysis, and various chemical techniques. These crystalline deposits in the peridium have proven to be primarily calcium oxalate. Some species of Perichaena and the Dianema also incoiporate silicon crystals on the peridium. The white and non-white phases of different species of Perichaena were compared and found to have similar elemental composition of peridia.
A new basic chromosome number in the genus Lotus
Authors: Angulo M. D. , Real M. C.
Published: September 2008

All species of the genus Lotus s. str. which have been karyologically studied to date have shown a basic chromosome number x = 6. A new basic chromosome number x = 5 has been found in a species of Lotus botanically classified as L. castellanus Boiss. and Reut. This finding is highly interesting for the study of the evolutionary trends of this genus which is agriculturally and scientifically very important. The structural characteristics of the new karyotype are described.
Glutamate dehydrogenase from Vicia faba
Authors: Fawole M. O.
Published: September 2008

Glutamate dehydrogenase (GDH: EC 1.4.1.2, L-glutamate: NAD+ oxidoreductase (deaminating)) from Vicia faba was assayed spectrophotometrically and was active with NAD+, NADH, or NADPH, but not with NADP+. The enzyme was localized in the particulate fraction. Activity on polyacrylamide gels was readily detected using NAD+ but only with a high concentration of coenzyme and prolonged incubation with NADP+. Each of the seven varieties of V. faba examined possessed seven NAD-GDH isoenzymes. The number of isoenzymes remained un-changed during the germination of the variety conqueror, although there was some variation in the intensities of the bands.
Association of microbodies, Woronin bodies, and septa in intercellular hyphae of Cymadothea trifolii
Authors: Camp Russell R.
Published: September 2008

This ultrastructural study describes the origin of Woronin bodies from microbodies in intercellular hyphae of the plant pathogen Cymadothea trifolii. In this fungus the development of Woronin bodies begins with the appearance of electron-dense material within the microbody. Subsequently, this material is confined to a developing evagination of the delimiting microbody membrane. Eventually the protrusion containing the electron-dense material is released as a Woronin body via an exocytotic mechanism. Woronin bodies are frequently found near septal pores and probably contribute to the formation of septal pore plugs.
Root cap structure in the fern Ophioglossum petiolatum: light and electron microscopy
Authors: Peterson R. L. , Brisson J. D.
Published: September 2008

A correlated light and electron microscope study of the root cap of the fern Ophioglossum shows that a central and peripheral region can be distinguished. Central cells develop large distally displaced amyloplasts, somewhat thickened cell walls with plasmodesmata mainly in the transverse walls, vacuoles (many of which contain dense osmiophilic inclusions), and proximally located endoplasmic reticulum. Young peripheral cells have randomly located amyloplasts, vacuoles (some of which contain osmiophilic deposits), and rather uniformly and slightly thickened cell walls with a few plasmodesmata. With age, the peripheral cells undergo many changes including a loss of starch and the appearance of many plastoglobuli in the plastids, a thickening of cell walls (particularly on the outer tangential wall), and an eventual breakdown of the cytoplasm. During wall thickening, dictyosomes which pinch off two types of vesicles, electron-dense vesicles and those containing fibrillar material, are abundant in the cytoplasm. Both types of vesicles fuse with the plasmalemma and apparently release their contents into the wall. The root apical cell and its immediate derivatives are characterized by a large nucleus, plastids with small starch grains, many small vacuoles mostly containing dense osmiophilic deposits, and a cell wall with a large number of plasmodesmata.
Some bog chytrids
Authors: Sparrow F. K. , Lange Lene
Published: September 2008

Twenty different chytridiomycetes were isolated from a small sphagnum bog in northern Michigan. Three of these are considered to be new, namely. Rhizophydium porosum n.sp., R. undulatum n.sp., and Phlyctochytrium incrustans n.sp. The identity of several are left in doubt, in particular one tentatively assigned to Catenaria sphaerocarpa.
Development of an ineffective pea root nodule: morphogenesis, fine structure, and cytokinin biosynthesis
Authors: Newcomb William , Syono Kunihiko , Torrey John G.
Published: September 2008

Roots of the garden pea Pisam sativum L. cv. Little Marvel inoculated with Rhizobium leguminosarum strain 1019 produce small white nodules which are ineffective in fixing atmospheric nitrogen. Analyses of cytokinin contents of the nodules at different ages using extraction, purification, and thin-layer chromatographic separation showed that the cytokinins zeatin and zeatin riboside and isopentenyladenine and its riboside were present in greatest amounts early in nodule development and decreased thereafter. A new unidentified cytokinin was present in older nodules. The early stages of the infection process in the ineffective nodules were similar to those observed in effective nodules. However, bacteria released from the bacterial thread via an unwalled droplet were not always surrounded by a host membrane. In later stages of nodule development many infected cells contained rhizobia with no enclosing membranes so that the bacteria were free within the host cytoplasm. Such cells showed very low frequencies of mitochondria, of polyribosomes, and endoplasmic reticulum. Thus, the biosynthetic capacity of the cells appeared to be impaired and membrane synthesis defective. The failure of the nodules to develop nitrogenase activity is probably related to the failure of membrane formation around the bacteria. Abnormalities in amyloplast formation were also noted, as well as structural differences in the nodule, including a higher proportion of uninfected cells and earlier cessation of mitotic activity in the nodule meristem than occurs in effective nodules of pea. Transfer cells were observed in the pericycle in both effective and ineffective nodules.
Factors influencing ascospore germination in three species of Sporormiella
Authors: Asina Shirin , Jain Kanti , Cain R. F.
Published: September 2008

Ascospore germination of Sporormiella intermedia, S. isomera, and S. minima requires sodium acetate as an exogenous source of energy. Maximum ascospore germination occurs at a concentration of 5.0 g/ℓ of sodium acetate in the medium. Among the physical factors studied, the pH of the medium was found to be crucial: germination occurred within a very narrow pH range (5.0–7.0) and reached an optimal level at pH 5.5. The ascospores of S. intermedia and S. isomera germinated between 10 and 30 °C while those of S. minima germinated between 10 and 40 °C. The optimal temperature varied for each species (10–20 °C for S. intermedia; 20–25 °C for S. isomera; 30–35 °C for S. minima). At 30 °C and above, a globose vesicle formed in all three species before the formation of the germ tube. Light had no influence on ascospore germination, nor were external supplies of nitrogen or vitamins necessary for spore germination.
Factors influencing growth and ascocarp production in three species of Sporormiella
Authors: Asina Shirin , Jain Kanti , Cain R. F.
Published: September 2008

Three species of Sporormiella (S. intermedia, S. isomera, and S. minima) grew and fruited over wide ranges of pH and temperature. The optimum pH was 7.0 or above and the optimum temperature range for S. intermedia and S. isomera was between 15 and 25 °C and for S. minima between 15 and 35 °C. Light did not affect either growth or fruiting. Ammonium acetate, D-alanine, and L-proline were excellent nitrogen sources for growth and fruiting. Several of the best utilized carbon sources were the following carbohydrates: monosaccharides: D(+)-xylose, D-glucose, fructose, and D-mannose; disaccharides: D(+)-cellobiose and maltose; polysaccharides: Alphacel, dextrin, and starch; sugar alcohols: mannitol and sorbitol. Growth increased linearly with an increase in the concentration of carbon from 1 to 8.0 g/ℓ. Sucrose was poorly utilized by S. intermedia and S. minima while S. isomera failed to utilize it entirely. None of the species studied utilized lactose. Alphacel yielded (at all concentrations) the maximum number of ascocarps. In the case of the other carbohydrates, S. intermedia and S. isomera produced the maximum number of ascocarps at very low concentrations of carbon (1.0 g/ℓ). Maximum production of ascocarps for S. minima was obtained with higher concentrations of carbon. Sporormiella isomera required an exogenous supply of thiamine for growth and ascocarp production while S. intermedia required both thiamine and biotin. Sporormiella minima grew with thiamine but fruited only with the addition of biotin to the medium. All three species grew well in basic synthetic liquid medium (Containing glucose as a carbon source and potassium nitrate as a nitrogen source) but none of them formed ascocarps.
Oxygen transport rates through mats of Lemna minor and Wolffia sp. and oxygen tension within and below the mat
Authors: Morris P. F. , Barker W. G.
Published: September 2008

A boundary-layer model has been used to describe the movement of dissolved oxygen through a vegetation mat of Wolffia sp. or Lemna minor. In an environment where light and temperature are held constant, the reaeration rate of the water below the mat is a linear function of mat thickness. In the light, the rate of oxygen transfer into water through a 10.5-mm mat is 4.4 times higher for Wolffia and 2.9 times higher for L. minor than in the dark. In the light the rate of oxygen transfer through Wolffia mats is significantly lower in August and September than in early summer. A seasonal shift in transport rates through L. minor mats has not been conclusively established. The efficiency of gas transfer through washed Wolffia and L. minor mats 8 to 16 mm in thickness varies from 4.0 to 47.0% of the estimated gas exchange rate for a small protected lake. The rate of gas transfer through the mat is higher than might be expected considering the close packing of the component fronds. The shape of the oxygen profile in the upper portion of a photosynthetically active mat indicates that much of the oxygen produced by photosynthesis of the submerged fronds may be lost to the atmosphere.When the light intensity falls below the level required to exceed the compensation point, dissolved oxygen levels in the water trapped between the fronds are quickly reduced to very low tensions despite the proximity of the entire mat to the oxygen-saturated air–water interface.
Cell wall elastic properties of Chara corallina
Authors: Vinters H. , Dainty J. , Tyree M. T.
Published: September 2008

Transcellular osmosis measurements are combined with measurements of the kinetics of relative length change, when Chara corallina cells are transferred from artificial pond water to polyethylene glycol (mol wt 300 to 400) of higher osmotic pressure to yield the constant k, which relates relative volume change ΔV/V to relative length change Δl/l (ΔV/V = k Δl/l). The value of k is 3.5 and is temperature independent between 7 and 30 °C. Static and kinetic estimates of the bulk modulus, ε, indicate that ε is temperature independent and has a value between 500 to 650 bars at high turgor pressures. The value of ε declines as the turgor pressure declines. We show how ε and k are related to Young's modulus and to Poisson's ratio for anisotropic C. corallina cell walls and point out that the previous treatments of the problem are in error.
The Fungi of Ontario. II. Erysiphaceae (mildews)
Authors: Parmelee J. A.
Published: September 2008

Twenty-eight species in six genera are recognized, described, illustrated, and their distribution in the province of Ontario and adjacent Quebec and Manitoba recorded. Keys based on fungus morphology provide access to the species treated and an alternate access is given by a generic host index. New hosts and new distribution records are noted within species treatments. Microsphaera on Vaccinium, long regarded in North America as part of the complex species M. penicillata, is given species recognition as M. vaccinii.