bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and functional adaptations of eelgrass (Zostera marina L.) to the anaerobic sediment environment
Authors: Penhale Polly A. , Wetzel Robert G.
Published: April 2011

Structural and functional adaptations of the seagrass Zostera marina L. to the anaerobic sediment environment were examined both experimentally and under natural conditions along a transect including environmentally different sites in Izembek Lagoon, Bering Sea, Alaska. Aerobic root respiration rates, end products of anaerobic metabolism in roots and rhizomes, lacunal development, and internal gas volume and gas composition were compared among plants from three sites. Root respiration decreased across the transect from the intertidal site to the two subtidal stations of increased sediment anaerobiosis. Ethanol concentrations of roots and rhizomes were very low in all cases and shikimate could not be detected. Malate concentrations in the rhizome tissues were high in the midbed portion of the transect and lower at both the intertidal and deep edges of the bed; malate concentrations of root tissue followed a reciprocal pattern. The internal gas volume (lacunal space) of leaves and roots increased along the transect of increased sediment anaerobiosis. Anatomical observations of roots showed a similar trend with enhanced lacunal development at the most anaerobic site. Data collected in field and laboratory experiments in which the hydrogen sulfide concentration surrounding the roots and rhizomes was enhanced showed physiological adaptations characteristic of tolerance to anaerobiosis. The collective data indicate that Zostera marina is capable of responding to markedly different microenvironments.
Photoinduction des périthèces du Nectria galligena : production et activité photomorphogène des mycosporines
Authors: Dehorter Bertrand , Bernillon Jacques
Published: April 2011

Mycosporin I yield of Nectria galligena Bres. in response to duration, intensity, and spectral quality of illumination were evaluated by high-performance liquid chromatography (HPLC). Duration and nature of irradiation were essential light factors for an increase of mycosporin content in the mycelium. The most effective wavelengths were 320, 370, 420, 450, and 500 nm. In addition, it was demonstrated that mycosporin I and ascocarp production required very similar light conditions, and the rate of sexual reproduction as well as mycosporin I yield were correlated. Furthermore, photomorpbiogenic action of mycosporin I extracted from N. galligena was demonstrated. This substance, when added to culture broth, served as a partial substitute for the active light and induced fertile ascocarps in darkness. Moreover, it was shown that, while mycosporin I (related to reduced serine) characteristic of N. galligena was the most active compound, the type II mycosporins (related to reduced glutamine and glutamic acid) were also morphogenic effective. Because of its photodependent biosynthesis and its photomimetic (morphogenic and metabolic) activities, mycosporin I appears to be an outstanding mean for the the study of the sexual photoinduction in N. galligena.
Observations préliminaires sur l'organisation du cytosquelette des cellules végétales. Mise en évidence d'un “réseau microtrabéculaire”
Authors: Arsanto Jean-Pierre
Published: April 2011

Electron microscopic observations of particularly favourable sections of pericycle and vascular parenchyma cells fixed with glutaraldéhyde have revealed the existence of a network of exceedingly fine filaments in the cytoplasmic ground substance of plant cells. This highly intricated structure to which polysomes seem to be attached interconnects the cytoskeletal fibers and the various other cellular components. It corresponds evidently to the "microtrabecular lattice" described in animal cells. Moreover, this report points out that microfilaments, which are 6- to 8-nm putative actin filaments, contract with microtubules or sheets of agranular reticulum, to form privileged close relationships whose functional significance is discussed.
Représentation pollinique actuelle à Lanoraie (Québec), et méthodologie de l'analyse pollinique
Authors: Comtois Paul
Published: April 2011

We have undertaken the analysis of 45 surface samples from the Lanoraie peat bogs (45°58′ N, 73°20′ W), situated in the Saint Lawrence lowlands. A reassessment of the different pollen sources that contribute to the pollen rain is carried out. According to the ecology of the species recovered, two principal classes are recognized; proximal and distal. Each of these classes is subdivided in two subclasses according to their extent. The punctual and local sources compose the proximal class, and the regional and zonal sources compose the distal class. The use of similarity and association indices permits the identification of the different distal sources. Thirty-five percent of the distal species are associated among themselves. We identify three habitats: forest, fields, and bogs. We also observe that pollen analysis recovers only those species that make the dominant strata. The characteristic species of Lanoraie are Quercus sp., Salix sp., and the grasses. The strongest pollen productors are Ambrosia artemisifolia (36%), the grasses (10%), and Pinus strobus (8%). We have also outlined the vegetation communities of the proximal class. These communities are discussed first from the point of view of the associations, then from the point of view of the species. According to their hydric characteristics, the elements of the pollen flora are grouped in three types. This inventory should permit a better interpretation of the pollen analysis results in terms of vegetation succession.
A test of the accuracy of shade-tolerance classifications based on physiognomic and reproductive traits
Authors: Lorimer Craig G.
Published: April 2011

Traits such as live crown ratio and understory stem density are often used subjectively as a guide to grouping tree species into shade tolerance classes. The accuracy of this approach was tested on nine species in an upland oak forest by comparing a tolerance index based on measurements of live crown ratio and understory stem density with observed survival and growth rates of suppressed trees obtained from 19-year permanent plot records. A high correlation (r = 0.93) was found between predicted and observed tolerance indices. The observed tolerance of several species differs from traditional classifications but was correctly predicted by the tolerance index.
Growth experiments on morphological mutants of Gracilaria tikvahiae (Rhodophyceae)
Authors: Patwary Mohsin U. , Meer John P. van der
Published: April 2011

The growth of morphological mutants of Gracilaria tikvahiae was compared with that of wild-type clones in tanks of flowing seawater in a greenhouse. At low density four mutants grew faster than a related wild type, and two, MP-40 and MP-44, grew faster than any of the wild clones tested. Of the mutants, MP-40 consistently had the fastest growth rate at low density. At high density MP-40 and MP-44 again grew faster than wild type; however, MP-44 had the faster growth rate and gave the higher yields. Both of these mutants removed nitrogen (NH4+) from seawater faster than the wild types and both proved to be much more epiphyte resistant, with MP-40 scoring highest for both of these characteristics.
Uptake and accumulation of copper, nickel, and iron by Typha latifolia grown in solution culture
Authors: Taylor Gregory J. , Crowder A. A.
Published: April 2011

Concentrations of Cu, Ni, and Fe in leaf and root tissue of Typha latifolia L. grown in a series of solution cultures containing 5–100 μg g−1 Cu, 10–150 μg g−1 Ni, or 10–100 μg g−1 Fe were correlated with concentrations of the same metals in the growth medium. In contrast to plants growing in contaminated wetlands near Sudbury, Ont., plants grown in solution culture were unable to minimize entry of Cu and Ni into leaf tissue. Leaves of T. latifolia accumulated 467 ± 50 μg g−1 Ni and did not show toxicity symptoms. Leaf Cu concentrations reached 127 ± 28 μg g−1 and toxicity symptoms (reduced leaf elongation and biomass production) appeared at leaf Cu concentrations of approximately 80 μg g−1. Thus T. latifolia would appear to have internal Cu and Ni tolerance mechanisms. Possible mechanisms for the exclusion of Cu and Ni in the field are discussed.
Production, in vitro, de périthèces du Nectria ditissima, agent du chancre du hêtre (Fagus sylvatica). II. Effets de la composition carbone–azote du milieu nutritif et influence de la lumière
Authors: Dehorter B. , Perrin R.
Published: April 2011

Ascocarp production in Nectria ditissima Tul. was found to occur on a wide range of C and N substrates. However, all the organic acids, certain amino acids and ammonium salts tested prevented perithecial formation. Optimal production of ascocarps was observed with carbohydrates like lactose, dextrins, or maltose, with single N (isoleucine, phenylalanine, γ amino butyric acid) or mixed N sources (alanine, asparagine, glutamic acid). A C/N ratio ranging between 10 and 30 favoured perithecial production with an optimum when the C concentration was from 4 to 5 g/L or the N concentration from 150 to 250 mg/L. In liquid cultures at pH 5.5 and at 18 °C, N. ditissima developed perithecia only in the presence of light although light requirements were very low. Short duration of light (1 h/day) with a low intensity (10 μW∙cm−2) illumination was sufficient to trigger many ascocarps. Maximum sexual differentiation was induced at wavelengths 330, 380, 430, 480, and 500 nm.
Comparison of the flagellar rootlets and periplast in two marine cryptomonads
Authors: Gillott Marcelle A. , Gibbs Sarah P.
Published: April 2011

The flagellar rootlets and the cytoskeletal structures of the furrow–gullet region are described for two marine species of Cryptomonas. The rootlets of the two species are very similar, but are more reduced in C. sp. θ than in C. sp. [Formula: see text]. Four rootlets are present: a compound rootlet made up of a striated component of 60- to 80-nm periodicity overlain by three microtubules which extends anteriorly into the left lobe of the cell, a rhizostyle which descends to the nucleus and the posterior end of the cell, an ascending microtubular rootlet which passes anteriorly into the right lobe of the cell, and a lateral microtubular rootlet which curves around the dorsal side of the contractile vacuole. In C. sp. [Formula: see text], the rhizostyle consists of four winged microtubules; in C. sp.θ, it is reduced to three microtubules which lack wings. In C. sp.[Formula: see text], the ascending rootlet consists of five microtubules; in C. sp. θ, of three microtubules. In C. sp. θ, the lateral rootlet is reduced to a very short remnant. The rootlet systems of these two photosynthetic cryptomonads are similar to, but much reduced in complexity from, that of the leucoplast-containing cryptomonad Chilomonas paramecium. In the vestibulum and furrow–gullet region, the characteristic periplast plates are replaced by a modified periplast in C. sp. θ and a striated rim fiber in C. sp. [Formula: see text].
Effects of consecutive androgeneses on morphology and fertility in Nicotiana sylvestris
Authors: Paepe R. De , Prat D. , Knight J.
Published: April 2011

In Nicotiana sylvestris androgenetic haploid and doubled-haploid plants regenerated from isolated pollen grains show characteristic modifications in leaves and flowers as compared with the pollen source line. During successive cycles of androgenesis, their average dimensions decrease regularly up to the fifth cycle. Afterwards no significant decrease is observed, but other kinds of abnormalities appear, such as foliar outgrowths developing from leaf veins, in haploid and doubled-haploid plants, or from the somatic tissue of the ovules in haploids only. Doubled-haploid plants transmit their abnormalities through the first and second generations of selfing. Their fertility is greatly reduced because of physiological deficiencies when the plants are used as females, and low pollen fertility. Pollen from doubled haploids also has inferior androgenic capabilities.
Cytological studies of early stages of powdery mildew in barley and wheat. IX. Effect of various inorganic salts on the occurrence of autofluorescence at penetration sites of appressoria of Erysiphe graminis hordei
Authors: Kunoh H. , Yamamori K. , Ishizaki H.
Published: April 2011

The effect of various inorganic salts on the occurrence of autofluorescence at penetration sites of appressoria of Erysiphe graminis hordei in barley coleoptiles was examined by fluorescence microscopy. Divalent cations such as Ca2+, Mg2+, and Mn2+ enhanced fluorescence to varying degrees. Among them, Ca2+ had the greatest enhancing effect; intense fluorescence occurred around penetration sites within 10 min after the inoculated coleoptiles were transferred from water to CaCl2 solution. However, other divalent cations such as Zn2+ and Fe2+ showed cytotoxicity to coleoptiles and did not elicit fluorescence. Monovalent cations such as K+, Na+, and Li+ did not show any enhancing effect independently. Anions seemed to be associated with enhancement of the flurorescence in combination with their related divalent cations but not independently. An observed elimination of fluorescence by ethylenediaminetetraacetic acid suggests that the enhancing effect of some of the divalent cations may be associated with their interaction with a substance(s) which fluoresces only in combination with these cations.
Additional Hyphomycetes from freshwater swamps and hammocks
Authors: Schoknecht Jean D. , Crane J. L.
Published: April 2011

Collections of submerged, decayed plant material from freshwater swamps in Illinois and hammocks in Florida have yielded two new species, Intercalarispora nigra gen. et sp. nov. and Monodictys cruciseptata sp. nov. New records for North America include Zanclospora novae-zelandicae Hughes & Kendrick and Pseudopetrakia kambakkamensis (Subram.) M. B. Ellis.
Filamentous microorganisms from the Carboniferous of North America
Authors: Smoot Edith L. , Taylor Thomas N.
Published: April 2011

The remains of exceptionally well-preserved microorganisms consisting of spheres and short filaments are described from specialized phloem cells in a fern from the Upper Carboniferous (Pennsylvanian) of Kentucky. Although the affinities of these organisms are somewhat obscure, their small size (filaments approximately 1.0 μm in diameter) and distinctive morphology are suggestive of a relationship with the filamentous bacteria. The morphology of these organisms is compared with other previously described fossil bacteria as well as with eukaryotic fungi.
Biology of Trillium nivale (Liliaceae)
Authors: Nesom Guy L. , Duke John C. La
Published: April 2011

Trillium nivale Riddell exists in restricted populations that often are composed of many individuals. The species is primarily calciphilic, and its range is mostly within the limits of previously glaciated territory. At the study sites in central Ohio reproductive maturity usually is attained by plants 3–4 years old. Individuals of T. nivale live to be at least 8 years old; maximum longevity has not been determined but is probably considerably longer than 8 years. Meiosis and tetrad formation occur in July and August; preformed pollen in buds with relatively mature floral organs overwinter, and flowering occurs in late February through March of the next spring. Seeds mature in ca. 3 months after fertilization; an elaiosome is produced on each seed and the diaspores are disseminated by ants. Germination apparently occurs in early spring at least one season after seed production. Clonal growth is of limited importance; rhizomes very rarely produce offsets by lateral budding. Individuals of T. nivale are self-compatible, weakly protogynous, and facultatively xenogamous. We report n = 10 as the chromosome number in contrast to a previously published count of n = 12.
Ultrastructure of mitosis and the spindle pole body cycle in the smut fungus, Tilletia foetida
Authors: Hoffmann James A. , Goates Blair J.
Published: April 2011

The interphase nucleus in secondary sporidia of Tilletia foetida consists of mostly diffuse chromatin, one or two nucleoli, and an area of heterochromatin located opposite an electron-dense, extranuclear spindle pole body (SPB). The interphase SPB is an oval- to bar-shaped, double-structured disc that has a crystallinelike substructure. During nuclear migration into nascent sporidia, SPBs and nucleoli are randomly oriented. At the onset of division, chromatin begins to condense and the SPB becomes located on a nuclear protuberance. Cytoplasmic microtubules terminate at the SPBs and multivesicular bodies surround the SPBs from the early stages of SPB division to early postdivision. SPB discs become spheroid and each develops a medial, dense layer. Then, a basal, dense layer develops and elongates as the SPBs separate and become positioned on opposite sides of the nuclear protuberance. The nuclear membrane opens opposite the SPB during SPB division. The nucleolus is extruded into a nuclear bleb and degenerates. SPBs migrate to opposing sides of the nucleus and become diffuse as a microtubular spindle develops between them. Some spindle microtubules terminate at dense chromatin patches that are contiguous with the major mass of chromatin surrounding the spindle. During late division stages, spindle microtubules often appear to be closely juxtaposed. Except for polar openings adjacent to the SPBs, the nuclear membrane is entire until late division when it degenerates in the midregion of the nucleus. During early postdivision, the SPB condenses into a small, dense sphere as the chromatin and heterochromatin opposite the SPB become diffuse. The SPB then elongates into a dense bar and SPB material increases, except at the midportion, reforming the double structure of interphase.
Mitosis and the phylogeny of the genus Neocallimastix
Authors: Heath I. Brent , Bauchop Tom
Published: April 2011

Ultrastructural details of mitosis in species of the anaerobic chytridiomycete rumen fungal genus Neocallimastix are described in an attempt to clarify the phylogeny of the genus. Mitosis and spindle formation are entirely intranuclear and start with a group of kinetochores subtending a differentiated region of the nuclear envelope adjacent to extranuclear nucleus-associated organelles. Following duplication of the nucleus-associated organelles, a bipolar spindle develops among the kinetochores and elongates as the nucleus-associated organelles separate. At metaphase the kinetochores are spread along the spindle; heterochromatin is associated with them and also lies throughout the nucleoplasm remote from the spindle. During anaphase the kinetochore microtubules shorten and the two interdigitating arrays of nonkinetochore microtubules slide apart. Karyokinesis involves medial constriction of the nucleus and the persistent nucleolus. Mitotic nuclei in young thalli bear discoidal nucleus-associated organelles which are replaced by a variable number of centrioles in older thalli. These features are dissimilar from other described chytridiomycete mitoses and indicate either a distant relationship between the Neocallimasticaceae and other chytridiomycetes or substantial changes induced in the mitotic apparatus by the specialized environment of the organisms.
Carbon dioxide exchange rates and leaf nitrogen contents during ageing of the flag and penultimate leaves of five spring-wheat cultivars
Authors: Hunt L. A. , Poorten G. van der
Published: April 2011

Postanthesis carbon dioxide exchange and transpiration rates of flag and penultimate leaves of five spring-wheat (Triticum aestivum L. emend. Thell.) cultivars were measured from complete flag-leaf expansion to senescence. Leaf nitrogen contents were determined from anthesis to maturity. Both the absolute level of and the time-related decline of the carbon dioxide exchange rate varied among the cultivars. The flag-leaf carbon dioxide exchange rate decreased steadily throughout for one cultivar and slowly for a varying period and then rapidly for most others. The penultimate-leaf carbon dioxide exchange rate decreased throughout with one cultivar but did not decline in the period from 1 to 3 weeks postanthesis in others. The transpiration rate peaked at or near anthesis for the flag leaves and then either declined or fluctuated around the peak value for 3 weeks. The penultimate-leaf transpiration rate increased to a second peak late in ontogeny for most genotypes. In general, the time course of the transpiration rate matched that of the carbon dioxide exchange rate, but the transpiration rate at a specific carbon dioxide exchange rate was lower for penultimate than for flag leaves. The carbon dioxide exchange rate was linearly related to leaf nitrogen content, with the same regression applying for both flag and penultimate leaves; regressions were similar for all genotypes. There were no marked deviations from the overall carbon dioxide exchange rate – nitrogen regression that could be indicative of a "sink" influence on the activity of photosynthetic enzymes.
Cytogeographic studies on North American asters. II. Virgulus ericoides and V. novae-angliae in southern Ontario
Authors: Chmielewski Jerry G. , Semple John C.
Published: April 2011

Chromosome number determinations for 95 populations of Virgulus ericoides and 135 populations of V. novae-angliae from southern Ontario are reported for the first time. Although much of southern Ontario was sampled for these species, sampling was concentrated in the area formerly occupied by Ontario Island. All populations for both taxa were diploid (2n = 10), unlike the situation in several other asters that have been studied previously.
Microscopie de la mycoflore des aiguilles de sapin (Abies alba). II. Lophodermium piceae
Authors: Gourbière François , Pépin Régis , Bernillon Dominique
Published: April 2011

Colonization of Abies alba Mill, needles by Lophodermium piceae (Fckl.) Höhn. (Ascomycetes, Hypodermataceae) was studied by light and electron microscopy. Internal mycelium is at first extracellular and invades all the tissues of the needle; thereafter hyphae may penetrate all cells. Cytoplasm and walls of living cells (parenchyma, phloem, cellulosic transfusion tissues) are then lysed. Hyphae also invade thick-walled and lignified cells (epidermis, hypodermis, xylem, tracheids, and fibers of transfusion tissues) without major degradation of the cell wall. Ascomatal development is intraepidermic. Colonization of the needles is limited by black areas (the diaphragms), the structure of which is described. Lophodermium piceae is a primary saprophyte. Needles are colonized during senescence but ascomata appear only on fallen needles. There are about 230 ascomata per gram of needles. The ecology of this fungus is compared with that of Thysanophora penicillioides (Roum.) Kendrick on Abies needles and with that of Lophodermium pinastri (Schrad.) Chev. on Pinus needles.
Isolation and DNA analysis of protoplasts from developing female gametophytes of Picea abies (Norway spruce)
Authors: Hakman Inger , Arnold Sara von , Fellner-Feldegg Hugo
Published: April 2011

Female gametophytes of Picea abies were collected during their growth period (June and July). Tissues were prepared for light microscope examination of their development and for protoplast isolation and further DNA measurements. From archegonia initiation to early embryo development, protoplasts could easily be obtained from such gametophytes. Stained and fixed nuclei, prepared from the protoplasts, were subjected to flow cytometry and their DNA content was recorded to be half that of seedling derived nuclei.
The moss flora of the alpine – high subalpine Chowder Ridge area, western North Cascades Range, Washington State, U.S.A.
Authors: Spence John R.
Published: April 2011

Chowder Ridge, a high elevation area near Mt. Baker, Washington State, possesses a moss flora of 77 species based on collections made during two visits. Three species, Dicranum muehlenbeckii B.S.G., Rhacomitrium microcarpon (Hedw.) Brid., and Mnium arizonicum Amann, are reported new to Washington State. Coscinodon calyptratus (Hook.) C Jens. and Grimmia ovalis (Hedw.) Lindb. are noted for the first time from the west slope of the North Cascades. Chowder Ridge harbors an unusually large number of disjunts of the Rocky Mountain interior compared with typical sites on the west slope of the North Cascades, while the Pacific North American element is underrepresented. The bulk of the flora consists of species widespread in western North America.
Structure and ontogeny of Alnus crispa – Alpova diplophloeus ectomycorrhizae
Authors: Massicotte H. B. , Peterson R. L. , Ackerley C. A. , Piché Y.
Published: April 2011

Alnus crispa (Ait.) Pursh seedlings were grown in plastic pouches and inoculated with Frankia to induce nodules and subsequently with Alpova diplophloeus (Zeller & Dodge) Trappe & Smith to form ectomycorrhizae. The earliest events in ectomycorrhiza formation involved contact of the root surface by hyphae, hyphal proliferation to form a thin mantle, and further hyphal growth to form a thick mantle. Structural changes in the host, the mycosymbiont, and the fungus–epidermis interface were described at various stages in the ontogeny of ectomycorrhizae. Fungal hyphae in contact with epidermal cells in the regions of intercellular penetration and paraepidermal Hartig net developed numerous rough endoplastic reticulum cisternae. In more proximal regions of the mycorrhiza, these gradually became fewer in number and smooth. A complicated labyrinthine wall branching system also developed in the fungus in these regions. Concurrently, epidermal cells formed wall ingrowths in regions adjacent to Hartig net hyphae. There was a gradient in the formation of these epidermal transfer cells as the mycorrhiza developed, and an additional deposition of secondary cell wall over the wall ingrowths occurred as transfer cells senesced. Nonmycorrhizal control roots did not develop epidermal wall ingrowths. Electron-dense material, which was also autofluorescent, was deposited in the outer tangential walls of the exodermis contiguous to the paraepidermal Hartig net.
Regulation of vascular differentiation in leaf primordia during the rhythmic growth of Gnetum africanum
Authors: Mialoundama F. , Paulet P.
Published: April 2011

The growth of the principal axis of Gnetum africanum Welw. is achieved by successive growth and rest periods. During the phase of growth arrest, the terminal bud produces a single pair of leaf primordia containing no vascular tissue whereas observation of the terminal bud of the vinelike stem reveals that the oldest of the leaf primordia do contain vascular tissue before emerging. The differentiation of vascular bundles in the leaf primordia of the principal axis begins only with the return of the growth period during which time new young leaves are formed. The rhythm of formation of the leaves and their vascularization can be accelerated by removal of the young leaves. A prolonged exogenous treatment with abscisic acid after removal of the young leaves reestablishes the inhibition and prevents initiation of vascularization. It seems, therefore, that in the principal axis young leaves inhibit vascular differentiation of the leaf primordia, which may partly explain the inhibition of growth.
Analyzing growth in cell cultures. II. Effect of initial cell mass on growth
Authors: Singer Susan R. , McDaniel Carl N.
Published: April 2011

Numerous factors must be considered when analyzing growth in a cultured cell system. One extremely critical factor is the initial cell mass. The effect of initial mass (10 to 400 mg) on growth rate was assessed for cell lines tolerant and susceptible to the herbicides 3-amino-1,2,4-triazole (amitrole) and N-(phosphonomethyl)glycine (glyphosate). For a given cell line, the relationship between initial mass and growth rate was comparable in the presence and absence of the growth inhibitors. However, among cell lines the response varied. For one amitrole- and glyphosate-tolerant cell line, increased initial callus mass resulted in an increased relative rate of growth. However, the opposite effect was observed for another cell line which was also tolerant to both herbicides. For a third cell line which was herbicide sensitive no initial mass effect was observed. A fourth cell line (amitrole tolerant – glyphosate sensitive) also showed no initial mass effect except for the very small 10-mg calluses, which had significantly lower growth rates. The observed effect of initial mass was dependent on the method of calculating growth rates.
Annellidic conidiogenesis in Pithoascus schumacheri and redefinition of Pithoascus and related fungi
Authors: Valmaseda M. , Martínez A. T. , Barrasa J. M.
Published: April 2011

The presence of a Scopulariopsis Bainier anamorph in Pithoascus schumacheri (Hansen) von Arx is reported. Pithoascus langeronii von Arx is transfered to the monotypic new genus Pithoascina, on the basis of ascospore morphology and conidial state. The new combination Pithoascus stysanophorus (Matt.) Valmaseda, Martínez & Barrasa is also proposed. The relationship between the genera Pithoascus von Arx and Microascus Zukal is discussed.
Effects of SO2, O3, and SO2 and O3 in combination on photosynthesis and ultrastructure of two lichen species
Authors: Eversman Sharon , Sigal Lorene L.
Published: April 2011

Flavoparmelia caperata (L.) Hale and Umbilicaria mammulata (Ach.) Tuck, were exposed to 262 μg SO2 m−3, 59 μg O3 m−3, and 262 μg SO2 m−3 in combination with 59 μg O3 m−3 for 20 h over a 5-day period. Photosynthesis and ultrastructural observations were made after 12 and 20 h. At these low concentrations of pollutants, ultrastructural changes preceded and accompanied decreases in photosynthesis rates. Ozone was more phytotoxic than SO2. Ultrastructural damage was least with SO2 and greater and very similar with O3 and the combination of O3 and SO2. Photosynthetic data showed that SO2 ameliorates effects of O3. Electron micrographs showed increased accumulation of starch and cavity space around starch grains in the chloroplast and increased lipids in the cytoplasm in F. caperata; there was some increased starch in U. mammulata, but alterations were primarily in increased chloroplast opacity. Photosynthesis of U. mammulata was more sensitive to the pollutants than that of F. caperata. Ultrastructural damage was greater when samples were stored in the light than when they were stored in the dark between fumigations. The study shows that species vary in their responses to pollutants and that combinations of pollutants may give results different from those obtained with single pollutants.
A quantitative measure of introgression between lodgepole and jack pines
Authors: Wheeler Nicholas C. , Guries Raymond P.
Published: April 2011

Analyses of electrophoretic and morphological data for 37 populations of jack and lodgepole pine and their putative hybrids reveal (i) species are discrete, taxonomic entities that can be reliably distinguished; (ii) the two data sets yield concordant results with respect to species characterization and the detection and quantification of introgressive hybridization events; (iii) multiple localized introgressive hybridization events have occurred in Alberta and possibly the Yukon as a result of historical and ecological factors such as fire, glaciation, migration, edaphic preference; and (iv) introgression has probably had a significant evolutionary impact on these species in localized regions of the zone of species sympatry. Procedures developed elsewhere for the quantification of racial admixture in human populations provide sensitive estimates of gene exchange (introgression). Anderson's classic approach to the study of introgression using hybrid indices also provides relatively accurate accounting of gene exchange between taxa.
Thanatephorus pennatus sp.nov. isolated from mycorrhizal roots of Calypso bulbosa (Orchidaceae) from Alberta
Authors: Currah R. S.
Published: April 2011

A new species of Thanatephorus is described and illustrated based on fertile cultures derived from the mycorrhizal roots of two apparently healthy plants of Calypso bulbosa collected near Obed Summit, Alta. Thanatephorus pennatus sp.nov. is distinguished from other species of Thanatephorus by its globose basidiospores and its distinctive pattern of growth in culture. The role of T. pennatus as a mycorrhizal fungus is unknown.
In vitro pollen germination and viability of a Java × New Guinea Impatiens interspecific hybrid
Authors: Hicks C. B. , Stephens L. C. , Weigle J. L.
Published: April 2011

Pollen germination on 2% agar medium was investigated as a method of screening pollen viability, using ISU 7851-1, a Java × New Guinea Impatiens interspecific hybrid. A chi-square test showed that percentage pollen germination was related to corresponding seed set. However, some pollinations yielded seeds from pollen that tested in vitro as low as 0.5% germination. Other Impatiens genotypes were screened rapidly for pollen viability by microscopically scanning for pollen germination in vitro. ISU 7851-1 pollen diameter sizes ranged from 18 to 81 μm on agar medium, but only pollen grains of 45 μm and larger were capable of in vitro germination.
The effects of beaver in riverbank forest succession
Authors: Barnes William J. , Dibble Eric
Published: April 2011

The effects of beaver cutting on forest succession were studied on the banks of the lower Chippewa River in west central Wisconsin, U.S.A. Beavers were often found to be selective in their choice of woody plants, preferring ash and yellowbud hickory over all other species present. The effect of beaver cutting on tree density was substantial, with greatly reduced densities of trees in areas inhabited by beavers. The effects of beaver on the predicted composition of future generations of trees was also substantial. A major reduction in density is predicted for future populations of ash, hickory, and hackberry in areas of beaver activity, with a concomitant increase in the density of basswood and elm and possibly silver maple and prickly ash.
Development of Colletotrichum trifolii races 1 and 2 on alfalfa clones resistant and susceptible to anthracnose
Authors: Churchill A. C. L. , Baker C. J. , O'Neill N. R. , Elgin Jr. J. H.
Published: April 2011

Resistant and susceptible alfalfa clones derived from the cultivar Arc were spray inoculated with conidia from race 1 or race 2 isolates of Colletotrichum trifolii Bain in compatible and incompatible combinations. No significant differences were found in the frequencies of formation of immature or mature appressoria or in germ-pore formation by either race of C. trifolii on resistant or susceptible plants. These results indicate that incompatibility is not associated with the failure of conidia to germinate or to form appressoria with germ pores. In a small number of observations, penetration pegs were observed in tissue of both resistant and susceptible plants. Colletotrichum trifolii initiated infections in alfalfa by direct penetration of the epidermis via a penetration peg from the appressorium. Although the fungus spread rapidly throughout susceptible hosts, we observed fungus penetration only of epidermal cells of resistant hosts. Therefore, it appears that expression of alfalfa resistance to C. trifolii occurs near the time of epidermal cell wall penetration.
Seed-bank contributions to regeneration of shrub species after clear-cutting and burning
Authors: Morgan P. , Neuenschwander L. F.
Published: April 2011

Seed banks contributed significantly to regeneration of early seral shrubs after clear-cutting and fall broadcast burning of dense coniferous forests of the Thuja plicata/Clintonia uniflora habitat type in northern Idaho. Seeds were separated from 36 samples of soil and surface organic matter from 15 uncut forest stands. Total seed density averaged 1151 ± 1896 seeds/m2, and seed density for individual shrub species ranged from 1 ± 3 to 690 ± 1728 seeds/m2. Canopy cover of the "obligate" seed bank species, such as Ceanothus sanguineus and Prunus emarginata, was low or nonexistent in uncut forests, seed constancy and density in seed bank were high, and seedling regeneration on 2-year-old burns was abundant. Species that were "non-reliant" on seed banks, including Symphoricarpos albus and Rosa gymnocarpa, resprouted and no seedlings were found after burning. Response of "opportunistic" seed-bank species such as Rubus parviflorus and Rubus ursinus was intermediate; both seedling and sprout regeneration occurred after cutting and burning. These species existed in uncut stands both in the seed bank and in the understory. Burn severity affected germination and (or) seedling survival of Ceanothus sanguineus. Its percent canopy cover was greater on high-severity than on low-severity 2-year-old burns.
Fruit and seed set in Mayapple (Podophyllum peltatum): influence of intraspecific factors and local enhancement near Pedicularis canadensis
Authors: Laverty Terence M. , Plowright R. C.
Published: April 2011

The breeding system and determinants of fruit and seed production in a population of 114 patches of Mayapple (Podophyllum peltatum L.) were examined. Experimental crosses indicated that Mayapple patches are self-incompatible (clones) and that fruit and seed set were pollinator limited. Mayapple flowers are nectarless yet depend primarily on infrequent visits by nectar-searching bumblebees for pollination. The proportion of flowers setting fruit and ovules setting seed in Mayapple clones was inversely associated with the distance to neighboring clones and the distance to Pedicularis canadensis L. plants. Clones within 45 m of P. canadensis plants (which are heavily visited by bumblebees) showed significant increases in fruit and seed production compared with a similar group of more distant clones. This effect is interpreted as evidence for a facilitative interaction between Mayapple and P. canadensis.
Notes on the genus Xeromphalina (Agaricales, Xerulaceae) in Canada: biogeography, nomenclature, taxonomy
Authors: Redhead S. A.
Published: April 2011

Eleven of the 13 North American species of Xeromphalina are reported from Canada. A key to 14 North American and northern Eurasian species is given. Type specimens for 9 names were examined. In Canada, subgenus Heimiomyces is represented by two species: X. tenuipes (Schw.) Smith (sect. Heimiomyces) and X. fulvipes (Murr.) Smith (sect. Fulvipes). Subgenus Xeromphalina is represented by sections Xeromphalina and Mutabiles. Xeromphalina brunneola Miller and X. campanella (Batsch: Fr.) Kuhner & Maire are circumboreal species documented from across Canada. Xeromphalina kauffmanii Smith occurs in southern Quebec, Nova Scotia, Costa Rica, the eastern United States, and in Japan. Section Mutabiles stat.nov. is completely revised based on pigmentation of the pileipellis, on the distribution and types of pileocystidia, and on the pigmentation of the stipe, in addition to characters used previously in the genus. The term "circumcystidia" is coined for pileocystidia largely confined to a band around the pileus margin. In North America, the name X. cauticinalis (Fr.) Kühner & Maire frequently has been misapplied to X. cornui (Quél.) Favre, a common, widespread species in Canada. Xeromphalina fraxinophila Smith is reported from across Canada and the United States and in Eurasia. The name Marasmius cauticinalis is neotypified. In North America X. cauticinalis ssp. cauticinalis occurs in western areas. Xeromphalina cauticinalis ssp. pubescentipes (Peck) comb. et stat. nov. occurs in eastern areas in North America, in Japan, and together with ssp. cauticinalis in Europe. Xeromphalina parvibulbosa (Kauff. & Smith) comb.nov. occurs across North America. Xeromphalina cirris sp.nov. from montane or boreal coniferous forests floors in British Columbia, Ontario, Colorado, Idaho, New Mexico, Oregon, Utah, Washington, and Wyoming and X. campanelloides sp.nov. from coastal British Columbia and Washington, and eastern montane New York and Quebec, on coniferous logs, are described. Rhizomorphs are formed by all Canadian species except X. tenuipes.
Ultrastructure of dormant basidiospores of Agaricus campestris
Authors: Ruch Donald G. , North Mary C.
Published: April 2011

The basidiospore wall of Agaricus campestris Fr. consists of three distinct layers. The outer two layers are continuous around the spore, while the third layer originates only a short distance from the hilar appendage and quickly thickens to form the bulk of the wall material of the hilar appendage. The protoplast is surrounded by a typical plasma membrane which lacks distinct invaginations. Centrally located nonmembrane-bound lipid droplets comprise the bulk of the protoplasm. Spores are binucleate, but the two nuclei do not exhibit any distinct relationship to each other. Sausage-shaped mitochondria with only a few but well-delineated plate-like cristae are present. Scant endoplasmic reticulum occurs just beneath the plasma membrane. Ribosomes occur regularly attached to the endoplasmic reticulum and outer mitochondrial membrane, as well as being densely packed throughout the cytoplasm. The structure and possible functions of single membrane bound vacuoles and microbody-like organelles are discussed in relation to other basidiospores.
Pathology of Coelomomyces stegomyiae in adult Aedes aegypti ovaries
Authors: Lucarotti Christopher J. , Klein Marina B.
Published: April 2011

Coelomomyces stegomyiae (Chytridiomycetes, Blastocladiales) infection in adult female Aedes aegypti (Diptera, Culicidae) is located primarily in the ovaries. Fungal hyphae do not penetrate the germaria or follicles but instead lie between the tunica propria and epithelial sheath within each ovariole and between the epithelial sheath and the peritoneal sheath of the ovary. Aedes aegypti is an anautogenous mosquito requiring a blood meal for egg development; similarly, fungal hyphae in infected ovaries will not differentiate to form resting sporangia until after the mosquito has taken a blood meal. The fungus restricts receptor-mediated endocytosis of vitellogenin by the plasma membrane of the oocyte so that few, if any, vitellin yolk granules form. Thick-walled resting sporangia have formed 72 h after the blood meal has been taken and these will be oviposited by the females in place of the aborted eggs.
Genetic relationships between fertility and pathogenicity and virulence to rice in Magnaporthe grisea
Authors: Kolmer James A. , Ellingboe Albert H.
Published: April 2011

The genetic relationships between fertility and pathogenicity and virulence to rice in Magnaporthe grisea (Hebert) Yaegashi & Udagawa were examined in four initial-generation and two second-generation families. Two isolates of M. grisea, highly virulent to rice, were crossed with fertile isolates that are pathogenic on weeping love-grass (Eragrostis curvule) and goose-grass (Eleucine indice). Approximately 30 progenies from each of the four initial-generation families were evaluated for mating type, fertility, pathogenicity, and virulence to rice differential cultivars. Most of the progenies were either nonpathogenic to rice or produced intermediate infection types. The expected 1:1 segregation for female fertility was not observed in progenies of the initial-generation families. Two highly virulent isolates, and one fertile isolate that produced small grey flecks on one rice cultivar, were selected from one of the initial-generation families as parents for two second-generation families. Nearly one-third of the progenies from one of the second-generation families were highly virulent to rice. Female fertility segregated in the expected 1:1 ratio, independent of mating type, in both families. Mating type, female fertility, and pathogenicity to rice segregated randomly; however, progenies highly virulent to rice were exclusively mating-type A and female sterile.
A phenological and cytological study of pollen development in western hemlock (Tsuga heterophylla)
Authors: Colangeli Anna M. , Owens John N.
Published: April 2011

Pollen-cone development, which was divided into nine phenological stages, was compared with pollen cytology in eight field-grown western hemlock (Tsuga heterophylla (Raf.) Sarg.) clones in 1983 and three container-grown clones in 1984. Phenology proved to be an accurate indicator of cytology, independent of collection dates and rate of development. The breaking of dormancy, the resumption of development, and meiosis occurred during stage 1 (quiescent bud). During stage 2 (swollen pollen-cone bud) the tetrad of microspores separated. The exine wall was completely developed during stage 3 (bud burst). The one-celled microspores began to expand as a result of accumulation of reserves during stage 4, when the pollen cones were one-quarter to one-half emerged through the bud scales. The first cell division occurred during stage 5, when the cones were greater than half emerged. The second and third cell divisions occurred during stage 6, after the cones had completely emerged through the bud scales. The fourth and final cell division, resulting in mature five-celled pollen grains occurred during stage 7 (stalk elongation). Mature pollen consisted of two prothallial cells and a stalk, a body, and a tube cell. Pollen shed occurred at stage 8. The empty cones (stage 9) remained on the trees until the following winter. Some practical implications of relating pollen-cone phenology to cytology are discussed.
Changes in the hemicellulosic polysaccharides of Avena coleoptile cell walls during growth of intact seedlings
Authors: Herrera M. Teresa , Zarra Ignacio
Published: April 2011

The variations taking place in the major polysaccharides of the cell wall of Avena sativa L. cv. Victory coleoptiles were studied during growth. Two fractions were obtained, one corresponding to cellulose and the other to the hemicelluloses. The relative content of cellulose was greater in the basal regions of the coleoptiles and the proportion of this polysaccharide fraction increased in all regions during growth. The hemicellulosic fraction was composed of two parts, an insoluble one designated the HC A hemicellulosic fraction, whose main component was seen to be an insoluble xyloglucan, and a soluble part designated the HC B hemicellulosic fraction, composed of an arabinoxylan and a (β1-3)- or (β1-4)-glucan. This latter was degraded during the growth of the coleoptiles. The average molecular weight of hemicelluloses HC A and HC B decreased from the sub-apical zones to the basal zones of the coleoptiles; this was related to the growth capacity of each of the regions into which the coleoptiles were divided.
Recovery of net primary production in subalpine meadows of Mount St. Helens following the 1980 eruption
Authors: Pfitsch William A. , Bliss L. C.
Published: April 2011

The deposition of 5–10 cm of tephra from the 1980 eruption of Mount St. Helens had no more effect than subsequent yearly weather fluctuations on the net primary production of subalpine meadows. The net primary production of areas subject to cold mudflows slowly increased as surviving plants resprouted through the eroded surface and has remained below that of tephra deposition areas. The net primary production of tephra deposition areas fluctuated dramatically (coefficient of variation = 40%) in the seven summers following the eruption. An inverse relationship between net primary production and nutrient concentration of individual species contributed to stability in aboveground nutrient pools from year to year. The dominant community members responded similarly to differences among years in summer precipitation, with little evidence of compensatory growth that would help stabilize community production. Tephra greatly inhibited seedling establishment. Species density (number of species per square metre) and diversity (H′) declined in a community having species that rely on sexual reproduction for persistence and also in experimental tephra addition plots in a more species-rich community. These results indicate that although the short-term effect of tephra deposition on net primary production was minor, the long-term consequence will be of community simplification, which will contribute to fluctuation in net primary production in response to yearly weather patterns.