bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of exogenous glucose on mycorrhizal colonization in vitro by early-stage and late-stage ectomycorrhizal fungi
Authors: Hutchison Leonard J. , Piché Yves
Published: April 2011

Under aseptic conditions, seedlings of 12 common tree species found in eastern Canada (Alnus rugosa, Betula papyrifera, Betula alleghaniensis, Abies balsamea, Tsuga Canadensis, Pinus strobes, Pinus resinosa, Pinus banksiana, Larix laricina, Picea glauca, Picea mariana, and Picea rubens) were inoculated with 10 species of ectomycorrhizal fungi (Piloderma bicolour, Lactarius thyinos, Lactarius subpurpureus, Lactarius torminosus, Hebeloma longicaudum, Cenococcum geophilum, Suillus sinuspaulianus, Suillus tomentosus, Leccinum holopus, and Boletinus paluster) in the absence or presence of exogenous glucose (2 g/L). Early-stage ectomycorrhizal colonizers with a broad host range (e.g., H. longicaudum) appeared to be less dependent upon the exogenous carbohydrate supply for successful formation of ectomycorrhizae than were host-specific late-stage ectomycorrhizal colonizers (e.g., Lactarius subpurpureus). Further investigations revealed, however, that while levels of exogenous glucose (1.0 and 10.0 g/L) increased mycelial growth of late-stage ectomycorrhizal colonizers, a detrimental effect on the growth of the seedlings took place in the presence of these fungi, rather than a concurrent increase in colonization and infection of the host roots. It is suggested that secondary fungal metabolites toxic to the plants are released as a consequence of increased mycelial growth in response to an increase in glucose concentrations. Thus, when dealing with late-stage ectomycorrhizal colonizers and host plants in mycorrhizal synthesis experiments, the exogenous glucose concentration is critical. Key words: early-stage fungi, late-stage fungi, ectomycorrhizae, glucose, root colonization, fungal metabolites.
Influence of double-stranded RNAs on growth, sporulation, pathogenicity, and survival of Chalara elegans
Authors: Punja Zamir K.
Published: April 2011

Three strains of Chalara elegans from diverse geographical areas that contained multiple (4 or 5) double-stranded RNA fragments were compared with spontaneously derived cultures from these strains that were either partially cured or completely free of dsRNA. In the wild-type strains, presence of the dsRNAs was found to significantly enhance phialospore production and pigmentation of colonies, whereas radial growth and mycelial dry weight accumulation were reduced. The rate and overall percentage of phialospore germination on 1% Noble water agar were also significantly reduced by the presence of the dsRNAs. In two partially cured strains (only one 2.8-kb fragment remaining), pathogenicity to various plant tissues was significantly enhanced when compared with the wild-type strains containing multiple dsRNA. However, survival in field soil was enhanced in one strain and reduced in the other. In the completely cured strain, the loss of multiple dsRNA fragments was associated with enhanced growth, reduced phialospore production, and a complete loss of pathogenicity and capability for survival in soil. These results indicate that the effects of dsRNAs in C. elegans vary with the strain. In general, the presence of multiple dsRNAs in this fungus enhanced sporulation, altered colony morphology, and reduced growth and pathogenicity. However, since the complete loss of dsRNA was found to eliminate pathogenicity and reduce survival, it suggests that some dsRNA fragments in C. elegans may confer an advantage to this soil-borne facultative plant pathogen. Key words: black root rot, soil-borne plant pathogen, Thielaviopsis basicola.
Caulonemal gravitropism and amyloplast sedimentation in the moss Funaria
Authors: Schwuchow Jochen M. , Kim Donggiun , Sack Fred D.
Published: April 2011

Caulonemata of the moss Funaria were examined to determine whether they are gravitropic. Funaria and Physcomitrella were also evaluated to compare amyloplast sedimentation with that of Ceratodon. Protonemata were either chemically fixed in place or examined alive using infrared time-lapse videomicroscopy. Funaria caulonemata were found to be negatively gravitropic, i.e., they grew upwards in the dark. Upward curvature reversed temporarily before cytokinesis in Funaria, a phenomenon already known for Ceratodon and Physcomitrella. Most horizontal and upward-curving Funaria tip cells contained a broad subapical zone where plastid sedimentation occurred. In dark-grown Physcomitrella caulonemata, sedimentation was detected by the presence of a thin, amyloplast-free strip of cytoplasm at the top of the cell. These results suggest that gravitropism and subapical amyloplast sedimentation may be relatively common in moss caulonemata. Key words: Physcomitrella, moss, protonema, plastid, sedimentation, gravity.
Étude de l'architecture aérienne de quelques plantes tropicales à ramification basitone : vers une révision du modèle de Tomlinson
Authors: Cremers G. , Edelin C.
Published: April 2011

The study of tree architecture initiated in 1970 was followed by that of grasses and liana. Up to now, a larger number of observations were conducted on plants belonging to the Tomlinson's model. Wide variations were perceived at the level of upright part of each “article” or “module”. These observations suggest that the Tomlinson's model should not be considered as a distinct model but rather as a variant with basitone repetition, likely to appear within most of the other known models. Key words: plant architecture, basitone ramification, monocotyledons, dicotyledons. [Journal translation]
Porodisculus pendulus: systematics, cultural characters, and Canadian records
Authors: Ginns J.
Published: April 2011

The first documented records of Porodisculus pendulus in Canada are from southern Ontario and southwestern Quebec. The cultural characters of the fungus are described for the first time. The numerous and sometimes improper names applied to this fungus are detailed and discussed, and type specimens are indicated for the epithets. Allied species are discussed. The global distribution of the fungus, which includes Africa, Asia, Australasia, and the Americas, is expanded. Key words: Basidiomycetes, systematics, Porodisculus, biogeography.
Étude ampélométrique de feuilles adultes de somaclones du cv. Grenache N (Vitis vinifera L.)
Authors: Martinez Maria-Carmen , Boursiquot Jean-Michel , Grenan Serge , Boidron Robert
Published: April 2011

To obtain a broader variability of the Grenache N grapevine, somaclones were produced from anther calli and placed in two different environments: a poor sandy soil (Espiguette) and a richer silty clay soil (Chapitre). To evaluate the observed variations at the foliage level, an ampelometric study was conducted over three consecutive years. Various biometrical analyses revealed that (i) leaf size varies in relationship with the environment: in the poor soil, leaves are smaller than in the rich soil for the control clone as well as the somaclones; (ii) whatever the environment, indentation is deeper in somaclone leaves than in control leaves, even 10 years after outplanting; (iii) some somaclones with deeply or barely indented leaves have a more stable behaviour, while others have a leaf morphology changing with the year and the environment; (iv) leaf indentation parameters defined by the authors allow for a fairly good characterization among somaclones and control: indentation index X5, (S1 + S2)/(L + L1), appears to have the highest discrimination potential; vein length and angle parameters do not allow for discrimination. Representation of the somaclones based on a "theoretical leaf", obtained from the different measurements, gives interesting supplementary information for the interpretation of the results. Principal component analysis leads to more information on the parameters as well as on individuals. This method was therefore retained for further analyses. In conclusion, this study shows that before commercial introduction of a somaclone, one must ensure that the morphology always corresponds to the grapevine type. Key words: in vitro, somatic embryos, variability, morphology, indenting, principal component analysis, discriminant analysis. [Journal translation]
Role of resin canals in the early stages of pine wilt disease caused by the pine wood nematode
Authors: Ishida Kyoko , Hogetsu Taizo
Published: April 2011

The role of cortical resin canals in the early development of a pine wilt disease in Japanese black pine, Pinus thunbergii, was studied. A part of the bark of a 2 cm long segment from a current-year stem was removed by a tangential cut with a razor blade. Both cortex-exposed segments with cut cortical resin canals (designated as +RC segments) and those without cut resin canals (–RC segments) were obtained by chance. When a virulent nematode isolate (S6-1) was inoculated onto the cut surface, the surface of the +RC segments turned brown 4 d after inoculation, and in some segments this browning occurred more intensely around cortical resin canals. When segments were cut transversely at the middle, the transverse cut surface of the inoculated +RC segments was brown and fragile, but that of the inoculated –RC segments was pale green and stable, as was that of the non-inoculated controls. Correspondingly, tissue cells including epithelial cells of the cortical resin canal of the +RC segments were all dead, but those of the –RC segments and the controls were alive. When nematodes were inoculated onto the inner surface (cambium side) of a bark peeling at which cambial xylem cells were exposed, they did not kill the cambial cells. When inoculated on the transverse cut end of a bark peeling from which nematodes would enter resin canals, nematodes killed all cells in the peeling. The above results indicate that nematodes do not kill cortical cells immediately after inoculation but become harmful to pine cells after living in cortical resin canals. Key words: Bursaphelenchus xylophilus, pine wilt disease, pine wood nematode, Pinus thunbergii, resin canal.
Allelopathic effects of phenolic acids on nucleic acid and protein levels in soybean seedlings
Authors: Baziramakenga Régis , Leroux Gilles D. , Simard Régis R. , Nadeau Paul
Published: April 2011

Experiments were carried out, in a controlled environment during a 4-h incubation period, to examine the effects of phenolic acids on uptake by soybean (Glycine max (L.) Merr cv. Maple Bell) roots of phosphate and methionine and their incorporation into nucleic acids and proteins, respectively. Benzoic, p-hydroxy benzoic, vanillic, cinnamic, p-coumaric, and ferulic acids were used in the study. Nucleic acid and protein synthesis were assayed by the incorporation of32P and35S-methionine into soybean root. The uptake of32P was reduced by benzoic, cinnamic, vanillic, and ferulic acids, while p-hydroxybenzoic and p-coumaric acids increased slightly its absorption. At 250 μM, all allelochemicals tested reduced the incorporation of32P into DNA and RNA. Benzoic, cinnamic, ferulic, and vanillic acids reduced the uptake of32S-methionine, whereas p-hydroxybenzoic and p-coumaric acids increased its uptake. The methionine incorporation into proteins was reduced by all phenolic acids, except for p-coumaric acid and vanillic acid at 125 μM. These results suggest that interference with nucleic acid and protein metabolism by the phenolic acids is one of the main mechanisms by which they influence plant growth. Key words: Allelochemicals, mechanism of action, phenolic acids, phosphorus, proteins, methionine, ion uptake.
Host range of Exserohilum monoceras, a potential bioherbicide for the control of Echinochloa species
Authors: Zhang Wenming , Watson Alan K.
Published: April 2011

Fifty-six plant species in 43 genera and 19 families, selected by using the centrifugal phylogenetic method, were screened against Exserohilum monoceras, a fungus collected in the Philippines on Echinochloa colona. Trials were performed under both optimum greenhouse conditions with supplemental 24-h dew and natural field conditions with no dew supplement. The compatibility of host–pathogen interactions was characterized by the time and level of sporulation observed on detached inoculated leaves. All Echinochloa species proved to be highly susceptible to this fungus under optimum greenhouse conditions as well as in the absence of a dew supplement. Rottboellia cochinchinensis was also highly susceptible to this pathogen regardless of the presence of a supplemental dew period. Among the crops tested, only corn seedlings were slightly infected under supplemental 24-h dew conditions, but no disease symptoms were observed on corn in the absence of a dew supplement. Sorghum and sugarcane were hypersensitive to the pathogen under supplemental 24-h dew conditions, but no infection was detected in the absence of a dew supplement. All other species tested were immune to E. monoceras. Data on sporulation on detached leaves from inoculated plants indicated that E. monoceras was weakly compatible with corn. No disease symptoms and no conidia were detected on leaves of trap plants. In the field, E. monoceras produced no symptoms on corn plants. Key words: host range, bioherbicide, Exserohilum monoceras, Echinochloa crus-galli, Echinochloa colona, Echinochloa glabrescens.
New species of Mycosphaerella occurring on Eucalyptus leaves in Indonesia and Africa
Authors: Crous P. W. , Wingfield M. J.
Published: April 2011

Although Africa and Indonesia have not been particularly well surveyed for Mycosphaerella leaf spot fungi, several species are known to occur on Eucalyptus leaves in these areas. Three new species of Mycosphaerella with anamorph states are described from herbarium specimens and cultures in the present study. Mycosphaerella suttoniae and Mycosphaerella heimioides are described from Eucalyptus leaves from Indonesia. The former species is of particular interest, because its anamorph Phaeophleospora epicoccoides is the first species of Phaeophleospora linked to Mycosphaerella. Mycosphaerella irregulariramosa is described from Eucalyptus saligna growing in the Northern Province of South Africa. Both M. irregulariramosa and M. heimioides have Pseudocercospora anamorphs, and these are described as Pseudocercospora irregulariramosa and Pseudocercospora heimioides. Notes are also provided on the host range and geographic distribution of previously described species of Mycosphaerella on Eucalyptus leaves in other parts of Africa and in Indonesia. Key words: Eucalyptus, Kirramyces, Mycosphaerella, Phaeophleospora, Pseudocercospora, systematics.
Two species in the Ceratocystis coerulescens complex from conifers in western North America
Authors: Wingfield Michael J. , Harrington Thomas C. , Solheim Halvor
Published: April 2011

Two species of Ceratocystis are described from western North America. Ceratocystis rufipenni Wingfield, Harrington, & Solheim is associated with the North American spruce bark beetle Dendroctonus rufipennis infesting both Engelmann spruce (Picea engelmannii Parry) and white spruce (Picea glauca (Moench) Voss) in British Columbia. This fungus is a primary component of the bark beetle mycota and has a relatively high degree of virulence to Engelmann spruce. Ceratocystis douglasii (Davidson) Wingfield & Harrington was previously described as Endoconidiophora coerulescens f. douglasii. It is common on Douglas-fir lumber in western North America where it causes blue stain. Both fungi grow optimally at low temperatures and produce perithecia only after extended incubation under refrigeration. Ceratocystis rufipenni produces conidiophores mostly in association with perithecia, whereas conidia and conidiophores of C. douglasii are produced abundantly on wood and agar. Key words: Ceratocystis, Chalara, Dendroctonus, Ophiostoma, bark beetle – fungus interactions, symbiosis.
Végétation épigée et banque de semences du sol: leur contribution à la stabilité cyclique des pinèdes mixtes de Pinus halepensis et P. pinaster
Authors: Trabaud L. , Martinez-Sanchez J. J. , Ferrandis P. , Gonzalez-Ochoa A. I. , Herranz J. M.
Published: April 2011

After fire (a frequent phenomenon in the Mediterranean area), numerous seedlings appear from seeds of the soil seed bank that would not appear would there be no fire. Why this sudden advent? To which species do they belong? Vegetation records were made in a 12-year-old mixed pine forest of Pinus halepensis and P. pinaster. At the same time, soil samples were collected (5 cm deep). The direct method (identification with binocular lens of all encountered seeds after soil screening) was used to identify seeds to species. Seeds of species encountered in large quantity were subjected to viability tests. The seeds of two therophytes (Trifolium glomeratum, T. campestre) were subjected to thermal treatments. The soil seed bank was only partially reflecting the floristic composition of the pine forest. Three groups of plants were distinguished: (i) species observed both in aboveground vegetation and in the soil seed bank (21.9%); all were perennials, (ii) species encountered only in the vegetation (58.5%); those preferentially regenerated by vegetative means, and (iii) species observed only in the soil seed bank (19.5%); most reproduced only from seeds. The number of seeds in the soil was high and their distribution very variable. The higher the number of plots in which seeds of a species appeared, the more numerous were the total seeds of that species recorded. Thus, Cistus ladanifer was present in great quantity in all samples. In seeds of species subjected to thermal treatments, low temperatures (50–90 °C) did not increase germination rates, but exposure to high temperatures (130–150 °C) for long duration (10 min) killed the embryo. In conclusion, numerous seeds are present in a dormant stage in the soil. When a disturbance such as fire eliminates temporarily the aboveground vegetation, these seeds germinate. Thus, after a fire, the seedlings of these species proliferate, then these species disappear with representation by seeds in latent form in the soil when perennial aboveground vegetation has reoccupied burned areas. Key words: seeds, soil seed bank, fire, thermal treatments.
Descendances maternelles de hêtre tortillard (Fagus sylvatica L. var. tortuosa Pépin); développement au cours des quatre premières années: I. fertilité, vigueur et apparition du phénotype tortillard
Authors: Thiébaut B , Garniaux O , Comps B , Muller C
Published: April 2011

In Verzy forest (near Reims, France), seeds were sampled from some tortillard beeches (Fagus sylvatica L. var. tortuosa Pépin) after free pollination. After a dormancy breaking treatment performed in laboratory, seeds were sown in nursery and seedlings were cultivated for 4 years. The purpose of this study is to examine the fertility of tortillard beech and the occurrence of its phenotype during the first years of development. According to our experimental conditions, full and empty seed ratios, germination rate, and seedling annual survival rate were not significantly different from those reported for the European beech in literature. Among 486 tortillard maternal descendants, after 4 years, 25% of the individuals showed a special shape, characterized by reiterations, and could be considered as "tortillards". This phenotype appeared progressively during the second year of seedling development. The number of tortillards increased from one year to the next and their typical shape became more pronounced until they were 4 years old. These results show that the tortillard variety is no less fertile and vigorous than the European beech. Key words: Fagus sylvatica var. tortuosa, morphology, growth, fertility, strength.
Glycolaldehyde inhibition of CO2transport in the cyanobacteriumSynechococcusUTEX 625
Authors: Salon Christophe , Li Qinglin , Canvin David Thomas
Published: April 2011

In studies of the inorganic carbon (Ci) concentrating mechanism of cyanobacteria glycolaldehyde is often used to inhibit photosynthetic CO2fixation. As a partial inhibition of active CO2transport by glycolaldehyde under steady-state Ciflux conditions has been recently suggested, in this paper, using mass spectrometry, we investigate in detail the relationship between glycolaldehyde concentration ([GLY]) and CO2transport both during the initial period following illumination of a cyanobacterial cell suspension and during the so-called steady state when an internal Cipool has been allowed to develop. Carbon dioxide uptake following illumination of a cyanobacterial cell suspension was progressively reduced by increasing [GLY] in the medium, both in the absence or in the presence of carbonic anhydrase. The same features were found when either Ciin the form of bicarbonate was injected to a pre-illuminated cell suspension in the presence of carbonic anhydrase in the medium or a pulse of CO2was provided to the cells in the light without carbonic anhydrase in the extracellular medium. Although photosynthesis was completely abolished with 10 mM glycolaldehyde, CO2uptake was only inhibited 20% but was decreased further by higher [GLY]. Double reciprocal plots of CO2uptake versus initial [CO2] determined with a range of [GLY] showed the inhibition to be noncompetitive. To simultaneously study CO2uptake and CO2efflux, H13C18O3was used with cells in which CO2transport alone, or both CO2and HCO3-transport system were allowed to proceed. Cells were inhibited with either iodoacetamide or glycolaldehyde and the time course of the various CO2species in the medium demonstrated that CO2uptake was inhibited partially with glycolaldehyde resulting in a greater CO2efflux from the cells. When the cell suspension was again illuminated, in the presence of glycolaldehyde, initial CO2uptake was greatly reduced, and the extracellular [CO2] eventually rose to a level higher than that which would be expected to be in equilibrium with the amount of Cipresent in the medium. Results are discussed in terms of glycolaldehyde use in Citransport mechanism studies in cyanobacteria. Key words: Synechococcus UTEX 625, blue-green algae, cyanobacteria, CO2transport, HCO3-transport, CO2efflux, inhibitor, Ciconcentrating mechanism.
Branching and competitive hierarchies in populations of Galium aparine
Authors: Puntieri Javier G , Pysek Petr
Published: April 2011

The role of branching on the development of size hierarchies was studied on experimental populations of the annual herb Galium aparine L. (Rubiaceae). All branches of plants growing at high and low density were severed as plants developed, and the growth of individual plants, the development of growth and size inequalities, and the mean change in the size ranking of plants over time were compared with those of populations of naturally branched plants. Size allometries were analysed for all treatments. The effect of the branch-severing treatment on growth and size inequalities was not significant for crowded populations. The position of individual plants in the ranking of weights in crowded conditions was less variable for populations of unbranched plants than for those of branched plants. Size and growth inequalities among branched plants were not significantly affected by population density. The hypothesis that branching increases the development of competitive hierarchies in G. aparine populations is not supported by the results. The role of height growth limitation in crowded conditions as a constraint to competitive hierarchy development is discussed. Key words: allometry, branching pattern, competitive hierarchy, Galium aparine, intraspecific competition.
Spatial patterns and causes of overwinter seed mortality in Phytolacca americana
Authors: Hyatt Laura A
Published: April 2011

To examine the causes of spatial variation in overwinter seed survivorship for an early successional plant, an artificial seed bank study was carried out. The design of the study separated vertebrate and nonvertebrate causes of overwinter seed mortality over three spatial scales. Vertebrate activity reduced seed survivorship more in disturbed than in intact forest, and within disturbed forest seed survival in patch types differed by transect, suggesting that vertebrate foraging behavior varies within the landscape context. Nonvertebrate and abiotic effects also suppressed seed survival within disturbed forest to a small but significant extent more than in intact forest, and transects within the disturbed area varied in their effects on survivorship. A second study examined the short-term spatial patterns of vertebrate predation only and showed transect-level patterns of seed predation that differed from those found in the longer term study. These results illustrate not only large spatial variation in vertebrate predation, but also the potentially important influence of less frequently measured effects of seasonal changes, abiotic conditions, and invertebrate and pathogenic attack on seed survival. Key words: seed predation, spatial variation, seed survivorship, disturbance.
Ectomycorrhizal community structure across forest openings on naturally regenerated western hemlock seedlings
Authors: Kranabetter J M , Wylie T
Published: April 2011

We examined the diversity and distribution of ectomycorrhizal morphotypes on naturally regenerated western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings across small forest openings (50-75 m in diameter) in northwest British Columbia. The total and average morphotype richness decreased across the 4-year-old forest openings despite the rapid establishment of western hemlock and lack of soil disturbance. Average fungal richness decreased from 13.1 morphotypes under the forest canopy to 9.6 at the forest edge (27% reduction) and to 7.8 in the forest opening (40% reduction). Cenococcum geophilum, Mycelium radicis atrovirens, and Lactarius I were the most abundant ectomycorrhizae at each gap position, and none of the ectomycorrhizal fungi found in openings were eliminated by "late-stage" fungi in mature stands. This fungal distribution supports the "multistage" concept of ectomycorrhizal succession. Seedlings under the forest canopy had a total of 38 fungal morphotypes in a relatively even distribution pattern that corresponded well to the "random niche boundary" hypothesis. Fungal distributions were progressively less even for seedlings at the forest edge and opening than for seedlings beneath the canopy, perhaps because reduced fungal diversity and hyphal inoculum had affected the competitive balance of the ectomycorrhizal community.Key words: ectomycorrhizal community, diversity, succession, forest gaps.
The European S and F intersterility groups ofHeterobasidion annosummay represent sympatric protospecies
Authors: Garbelotto Matteo , Otrosina William J , Cobb Fields W , Bruns Thomas D
Published: April 2011

In those regions of Europe where they coexist, the F and S intersterility groups (ISGs) of Heterobasidion annosum (Fr.) Bref. are primarily found on Abies spp. and Picea abies (L.) Karst., respectively. Eighty-three isolates of H. annosum were collected from Abies alba Mill. from 19 sites in Italy, including 10 Abies-Picea mixed conifer stands in the eastern Alps. The ISGs of a subsample of 34 isolates were determined by ISG-diagnostic arbitrary-primed (AP) PCR primers. For a subsample of 16 isolates, including two S isolates from Norway and one S isolate from California, nuclear markers generated by AP-PCR analysis, and mitochondrial markers generated by restriction fragment length polymorphisms and sequencing of the ML5-ML6 region of the mitochondrial large ribosomal RNA gene indicated that, in Europe, (i) the F and S ISGs can be found in the same forest stand but they are two genetically distinct units with restricted gene flow between them; (ii) each of the two ISGs is monophyletic and may lack strong genetic substructuring in subpopulations; and (iii) the two ISGs are closely related to each other and their nearest common close relative is the allopatric S ISG from North America. By combining these results with paleobotanical information and results from previous studies, we postulate a recent sympatric divergence of these two groups driven by differential host specificity and mating barriers.Key words: species complex, protospecies, sympatric, mating barriers, host specificity.
Leaves ofKarwinskia axamilpensesp.nov. (Rhamnaceae) from Oligocene sediments, near Tepexi de Rodríguez, Puebla, Mexico
Authors: de León Patricia Valasco , Cevallos-Ferriz Sergio RS , Silva-Pineda Alicia
Published: April 2011

A new plant from the Los Ahuehuetes locality, near Tepexi de Rodríguez, Puebla, Mexico, is described based on its leaves. They are characterized by being ovate to elliptic, 4.5 cm long by 2.1 cm wide, having an entire margin, eucamptodromous venation, a midvein that is slightly curved and attenuated towards the leaf apex, seven pairs of secondary veins diverging at an acute angle from the midvein, percurrent tertiary veins forking or sometimes reticulated forming areoles, and having a petiole 1.3 cm long and 0.3 cm wide. An agglomerative nonhierarchical analysis with average linkage, based on the definition of 41 character states in 18 operational taxonomic units allows distinction between Karwinskia, Berchemia, and Rhamnus; the recognition of an extinct monotypic genus, Berhamniphyllum; and the identification of two fossil species of Karwinskia, among which the new plant from Puebla, Karwinskia axamilpense Velasco de León et al., is well defined. This new fossil leaf not only adds to the recently known Tertiary plants of the Los Ahuehuetes locality, but it gives new insights into the past flora of tropical North America and further supports the long history of some neotropical endemics, suggesting that, during the Tertiary, at least some areas in southern latitudes of North America could have been important for the origin and radiation of some taxa.Key words: Oligocene, Mexico, paleobotany, Rhamnaceae, Karwinskia.
Isozyme variation in heterothallic species and related asexual isolates of Pythium
Authors: Barr D. J. S. , Warwick S. I. , Désaulniers N. L.
Published: April 2011

A collection of 63 heterothallic and asexual (sexually sterile) isolates were compared by isozyme analysis, vegetative characters, and their ability to produce oospores in paired cultures. The collection included isolates identified as Pythium heterothallicum, Pythium intermedium, Pythium macrosporum, Pythium splendens, Pythium sylvaticum, and Pythium tracheiphilum, and several unidentified isolates. Isolates were separated into 41 multilocus genotypes as defined by 11 isozyme loci. The data were analyzed with previously published data for Pythium ultimum, and dendrograms were obtained from unweighted pair-group method, arithmetic average cluster analysis. Forty-six genotypes (including nine of P. ultimum) grouped into seven clusters and three solitary genotypes. Six clusters contained known isolates of the aforementioned species and the seventh contained P. ultimum. Isolates within both the P. heterothallicum and P. sylvaticum clusters produced oospores when grown in paired cultures. Two of three isolates in the P. splendens cluster produced oospores, but none of the isolates in the P. intermedium and P. macrosporum clusters produced oospores when grown in pairs. Genotypes belonging to the P. intermedium cluster separated into two sister groups that had morphologically different vegetative bodies. There were no consistent vegetative characteristics to distinguish the species P. macrosporum, P. heterothallicum, and P. sylvaticum. Isozyme analysis provides an effective means of identifying Pythium species that do not readily produce oospores in culture. Key words: Pythium heterothallicum, Pythium intermedium, Pythium macrosporum, Pythium sylvaticum, Pythium splendens, Pythium tracheiphilum.
Solid-state 13C NMR characterization of cell walls of ripening strawberries
Authors: Koh T. H. , Melton L. D. , Newman R. H.
Published: April 2011

Ripe and unripe cell walls isolated from the cortical tissues of strawberry (Fragaria × ananassa Duchesne cv. Yolo) using HEPES-buffered phenol of pH 6.5 were analysed using solid-state 13C nuclear magnetic resonance. Changes in cell wall components during ripening were investigated by separating the spectra, using proton spin relaxation editing, into three subspectra based on the mobility of the molecules. The subspectra can be assigned to rigid material (cellulose), semirigid components (primarily polygalacturonic acid) and semimobile (other detectable noncellulosic substances). The results show that, with ripening, separation between the semirigid and semimobile domains became more distinct. Associated with this, the ratio of noncellulosic material (i.e., pectins and hemicelluloses) to rigid cellulose decreased from 2.3 for unripe to 1.9 for ripe. The crystallinity of the cellulose molecules remained unaltered throughout ripening. Furthermore, our work indicates that the basic cellulose crystallite of strawberry cell walls appeared exceptionally small compared with other systems studied thus far. Key words: solid-state CP-MAS 13C NMR, cellulose, plant cell walls, strawberry, fruit ripening.
Mechanisms promoting recovery from defoliation in goldenrod (Solidago altissima)
Authors: Meyer G A
Published: April 2011

Plant responses to defoliation were examined using Solidago altissima and a leaf-chewing beetle (Trirhabda sp.). Plants were exposed to five intensities of defoliation (ranging from 0 to 85% leaf area loss) and effects on carbon gain, vegetative growth, and flowering were determined. Defoliated plants partially restored their capacity for carbon gain in the following ways: (i) activity of damaged leaves remaining after defoliation was increased via delayed senescence and enhanced photosynthetic rates and (ii) regrowth leaves on damaged plants had higher specific leaf area (leaf area per leaf mass) than comparable leaves on undamaged plants, but photosynthetic rates per unit area were equivalent to controls; thus, these leaves covered more area for a given investment in biomass with no loss in activity per unit area. Delayed leaf senescence and compensatory photosynthesis are commonly observed following defoliation, but increased specific leaf area is not generally recognized as a mechanism contributing to plant regrowth. In spite of these changes, total carbon gain capacity of defoliated plants was still less than that of controls after 3 weeks of regrowth. Overall plant performance was reduced by defoliation. Defoliated stems grew at a slower rate early in the season, added fewer new leaves in the first few weeks after defoliation, and had fewer lateral stems throughout the season. Damaged plants delayed flowering and maintained height growth later into the season than undamaged plants. Damaged stems reached heights comparable with undamaged stems by the end of the season, but they were thinner and their flower production was lower. Declines in plant growth and flowering were linear functions of the percentage leaf area loss, suggesting that even low levels of insect feeding are likely to affect plant performance.Key words: Solidago altissima, Trirhabda, defoliation, compensatory photosynthesis, insect herbivory, herbivore damage, plant compensation.
Fungi on Juncus roemerianus. 11. More new ascomycetes
Authors: Kohlmeyer Jan , Volkmann-Kohlmeyer Brigitte , Eriksson Ove E
Published: April 2011

Anthostomella atroalba sp.nov., Phaeosphaeria roemeriani sp.nov., and Rivilata ius gen. et sp.nov. are described from the endemic needlerush, Juncus roemerianus Scheele, in salt marshes of the U.S. east coast. Phaeosphaeria roemeriani is an obligate marine species growing in the base of the plant, whereas A. atroalba and R. ius can be considered terrestrial, because they develop exclusively in the upper, not inundated, part of the leaves. Rivilata, a member of Saccardiaceae, is compared with representatives of Phillipsiella and Schizothyrium.Key words: Anthostomella, Juncus, marine fungi, marsh, Phaeosphaeria, Rivilata.
Mycoparasitism of selected sclerotia-forming fungi by Sporidesmium sclerotivorum
Authors: Mischke Sue
Published: April 2011

Sporidesmium sclerotivorum Uecker, Ayers, & Adams is mycoparasite of sclerotia with potential for biocontrol. Sclerotia of fungi in the sclerotial lineage of the Sclerotiniaceae, including species of Sclerotinia, Botrytis, Amphobotrys, and Monilinia, stimulated germination of macroconidia of Sp. sclerotivorum. The mycoparasite readily colonized sclerotia of Sclerotinia spp. and Amphobotrys ricini (Buchwald) Hennebert both in soil and in vitro. Sclerotia of Botrytis spp. were parasitized only occasionally, and some Sclerotiniaceae were not parasitized. The limits on the ability of Sp. sclerotivorum to parasitize sclerotia support its classification as fastidious. Not even the first step in mycoparasitism, germination of Sp. sclerotivorum macroconidia, was triggered by sclerotia of fungi outside of the family. Amphobotrys ricini, the causal agent of gray mold of castor bean (Ricinus communis L.), is a newly recognized host of Sp. sclerotivorum, and sclerotia of this pathogen were destructively colonized by the mycoparasite.Key words: Amphobotrys ricini, biocontrol, host-parasite interaction, Sclerotiniaceae, Sclerotium cepivorum, signal.
Genetic diversity and population structure of disjunct Newfoundland and central Ontario populations of eastern white pine (Pinus strobus)
Authors: Rajora Om P , DeVerno Linda , Mosseler Alex , Innes David J
Published: April 2011

The dramatic decline of eastern white pine (Pinus strobus L.) populations in Newfoundland over the past 100 years presents an opportunity to determine and monitor population bottleneck effects on genetic diversity in trees. To provide benchmarks and indicators for monitoring genetic changes due to recent and future bottleneck events and to assist development of conservation strategies, we assessed genetic diversity and structure of six small, isolated white pine populations from two regions at the limits of its geographical range in Newfoundland for comparison with three populations from its central range in Ontario for 20 allozyme loci coding for 12 enzymes. On average, 47.8% of the loci were polymorphic, the number of alleles per locus was 1.75, and the observed and expected heterozygosities were 0.215 and 0.195, respectively. Although most of the alleles were widespread, unique alleles were found in three of the nine populations examined. The Newfoundland populations were as genetically variable as those from Ontario. Generally, all populations exhibited slight excess of heterozygotes at most loci. Only 6.1% of the detected genetic variation was among populations, and the remainder among individuals within populations. The genetic distances among the populations within a province or region were as great as those among populations between the provinces or regions. Canonical discriminant functions and cluster analysis from genetic distances separated nine populations into the same four groups. Neither provincial nor regional or geographic gradient-related patterns of population variation and differentiation were apparent. It appears that 8000 years of postglacial geographic isolation and recent population decline have had little or no detectable effect on genetic diversity or differentiation of disjunct Newfoundland white pine populations from their ancestral mainland populations. Assuming their adaptability, the Ontario seed sources may be acceptable for white pine restoration in Newfoundland.Key words : Pinus strobus, allozymes, gene conservation, genetic diversity and population structure, genetic drift, population bottleneck.
A revision of Boerlagiomyces with notes and a key to the saprobic genera of Tubeufiaceae
Authors: Crane J L , Shearer C A , Barr M E
Published: April 2011

Boerlagiomyces velutinus (Penz. & Sacc.) Butzin and Boerlagiomyces laxus (Penz. & Sacc.) Butzin are lectotypified and the latter species, considered by some mycologists to be a synonym of B. velutinus, is reinstated as a distinct species. Boerlagella effusa (Syd., P. Syd., & E.J. Butler) J.L. Crane, Shearer, & M.E. Barr, comb.nov. is transferred to Boerlagiomyces. These three species are redescribed and illustrated. A key is provided to the six recognized species of Boerlagiomyces. Boerlagiomyces macrosporus V.G. Rao & Varghese is redescribed and illustrated and is placed in Thaxteriella. Diagnostic characters separating genera allied to Boerlagiomyces are presented in a revised key to the saprobic genera of Tubeufiaceae. Thaxteriellopsis bambusicola Sivanesan & Sharma and Thaxteriellopsis lignicola K.S. Panwar & S.J. Kaur are transferred to Chaetosphaerulina and illustrated. New combinations are made in Acanthostigmella and Thaxteriella.Key words: fungal systematics, Tubeufiaceae, Loculoascomycetes.
Diversity and abundance of bryophytes, lichens, and fungi in relation to woody substrate and successional stage in aspen mixedwood boreal forests
Authors: Crites Susan , Dale Mark RT
Published: April 2011

We examined the effects of woody substrate and stand age on diversity and relative abundance of bryophytes, lichens, and fungi in trembling aspen (Populus tremuloides Michx.) mixedwood boreal forests in Alberta. Point sampling was carried out on surfaces of downed woody material in young (23-26 years), mature (51-63 years), and old (122-146 years) aspen mixedwood stands. Downed woody material was categorized into one of seven decay stages. Diversity and relative abundance of bryophytes, lichens, and fungi were related to decay stage of the log and to stand age. Old aspen mixedwood stands had the highest nonvascular species richness and the greatest diversity of woody substrates in each of the decay stages. The seven decay stages shared many species. Species of bryophytes, lichens, and fungi on particular decay stages were different across the age-classes, indicating that time, as well as structural attributes, were important in determining species assemblages. These results suggest that both the presence of old aspen mixedwood stands and downed wood in different stages of decay are important to maintaining assemblages of bryophytes, lichens, and fungi.Key words: bryophytes, lichens, decay, aspen mixedwood, downed woody material.
Can arbuscular mycorrhiza change the effect of root competition between conspecific plants of different ages?
Authors: Moora Mari , Zobel Martin
Published: April 2011

Seedlings and adults of Hypericum perforatum L., common St. John's wort, were grown together in an experiment of factorial design, where the presence of root competition and arbuscular mycorrhizal inoculation were used as treatments. There was moderate shoot competition, the intensity of which was not manipulated. To check the response of plants to arbuscular mycorrhiza in noncompetitive conditions, adults and seedlings were also grown singly in pots. Single individuals of seedlings and adults responded positively to mycorrhizal inoculation, with the response of seedlings significantly greater. In the competition experiment the positive effect of mycorrhizal colonization on seedling growth vanished, since with root competition, both mycorrhizal and nonmycorrhizal seedlings were of the same size. Without root competition, the shoots of mycorrhizal adults were much larger than of nonmycorrhizal adults, but under root competition the shoot weight did not differ. Arbuscular mycorrhiza increased the biomass differences between competing seedlings and adults. We did not confirm our hypothesis that mycorrhiza makes competition between seedlings and adults more balanced because of the stronger positive response of seedlings to inoculation. The positive effect of arbuscular mycorrhizae on growth vanishes in more crowded conditions. It was concluded that if mycorrhizal inoculation has age-specific positive effect of seedlings in field conditions, it is more probably due to higher tolerance to abiotic stress than due to higher competitive ability of seedlings.Key words: arbuscular mycorrhiza, intraspecific root competition, seedlings, Hypericum perforatum.
Annual-shoot growth and branching patterns in Nothofagus dombeyi (Fagaceae)
Authors: Puntieri J , Barthélémy D , Martinez P , Raffaele E , Brion C
Published: April 2011

During the growing seasons 1994-1995 and 1995-1996, weekly measures of length and number of internodes and morphological observations were made on annual shoots of 11- to 21-year-old Nothofagus dombeyi (Mirb.) Blume trees growing in northern Patagonia, Argentina. Growth period and shoot size at the end of the extension period were highly variable. Four main types of annual shoots could be identified according to the death or persistence of the apical meristem and the development or not of axillary branches during the growth season of main stem extension. For all shoots the maximum growth rate took place in late November and was followed by a slower growth rate or cessation of growth in early December to early January. For those shoots with a long growth period, a second growth peak took place in late January-February, and only those shoots with a growth rate higher than 35-40 mm/week developed axillary branches as they elongated. Results from bud dissections suggest that the early growth rate peak corresponded to the development of those structures preformed at the time of bud break. The death of the apical meristem of a shoot affected both the position and the relative size of axillary branching on that shoot.Key words: Nothofagus, annual shoot, growth dynamics, branching pattern.
Apical meristem formation during zygotic embryo development of white spruce
Authors: Yeung Edward C , Stasolla Claudio , Kong Lisheng
Published: April 2011

The first notable sign of shoot and root meristem development in zygotic embryos of white spruce (Picea glauca (Moench) Voss) was the appearance of starch in the respective poles of the embryo. Starch granules gradually accumulated in the subapical cells of the shoot pole and were soon followed by vacuolation in the subapical cells. Vacuolation reached its highest degree in these cells at the early embryo stage. With the formation of the large vacuolated cells, the surface cell layer at the summit of the shoot pole enlarged and differentiated into the surface initials of the shoot meristem. These cells were large with distinct nuclei. As the embryo matured, the large vacuoles within the subapical cells were replaced by small ones with a concomitant increase in the cytoplasmic density of the subapical cells. After germination, the surface initials remained distinct; however, the subapical cells had different fates depending on their location. The subapical cells located next to the surface initials became the central mother cells of the shoot meristem and those located near the cotyledon junction divided periclinally and gave rise to the epicotyl rib meristem. The remaining subapical cells near the procambium became part of the pith. In the root pole, starch could be found in the cap region terminating underneath the developing procambium at the club-shaped stage of embryo development. Two layers of root initials appeared at the junction between the developing procambium and the root cap. The initials were distinct as they were larger in size than surrounding cells. Cell division activity could not be detected in the layer of initials immediately next to the procambium, while mitotic activity could be seen in the adjoining layer next to the root cap. As the embryo matured, cells surrounding the root initials also took on structural characteristics similar to the root meristem initials. As a result, the region of the root meristem initials expanded in size, and the bilayered configuration became obscure. After germination, mitotic figures could be found in the root initials. As seedling continued to grow, fewer mitotic figures could be found in the root meristem cells adjacent to the procambium pole. In roots of mature plants, a group of isodiametric cells could be discerned between the procambium and the root cap. Mitotic activity was not readily detected within this group of isodiametric cells but mitotic figures could be found in surrounding cells.Key words: apical meristems, Picea glauca, white spruce, zygotic embryogenesis.