bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in pathogenicity among and within Mycosphaerella pinodes populations collected from field pea in Australia
Authors: Wroth J M
Published: April 2011

Ninety-nine single ascospore isolates of Mycosphaerella pinodes (Berk. & Blox.) Vestergr. from widely separated locations in southern Australia varied greatly in their ability to cause disease in leaves and stems of 10 host genotypes when assayed at two inoculum pressures. There were highly significant differences between the infection pressures, isolates, and host genotypes that accounted for most of the variance. A small proportion of the variance included a highly significant host genotype beta isolate interactions in leaves and stems and a highly significant host genotype beta isolate beta environment interaction in leaves. The continuous variation in disease responses among isolates precluded classification into distinct pathotypes. A cluster analysis of the data revealed that many isolates were closely related irrespective of the host cultivar or location from which they were collected. The relationship between mean host resistance and the variation among isolates was assessed, and it was concluded that increasing host resistance was unlikely to increase variation in the pathogen population; therefore, resistance should be relatively stable.Key words: Ascochyta blight, Pisum sativum, host-pathogen interaction, cluster analysis.
Subterranean structures and mycotrophy of the achlorophyllous Triuris hyalina (Triuridaceae)
Authors: Imhof Stephan
Published: April 2011

Triuris hyalina Miers, an unusual achlorophyllous plant, was investigated for subterranean morphology, root anatomy, and mycotrophy. Stems with scale leaves extend subterraneously to a depth of 15 cm. Pairs of adventitious roots develop at the scale leaves and clumps of apparently radiating roots, formed by accumulations of side shoot and scale leaf developments, occur. Roots consist of epidermis, short cell exodermis, three distinct layers of cortex parenchyma, endodermis, and an extremely reduced central cylinder with one or two central tracheidal xylem elements. The fungus associated with T. hyalina roots exhibits thick-walled, 6-9 µm thick, aseptate external hyphae. It penetrates the epidermis by developing appressoria and enters the cortex solely through the short cells of the exodermis. In the cortex cells, the aseptate hyphae start to coil. In the outer cortex layer, hyphae are thin, frequently branched, and most densely coiled. In the middle cortex layer they are thicker and less densely coiled, and mostly appear degenerated to clumps of amorphous fungal material. The inner cortex layer rarely becomes colonized. Vesicles occur in the outer and the middle cortex layers. This mycorrhizal pattern is interpreted as an adaption to attain a sustainable use from the endophyte. It is suggested that the mycorrhiza in Triuris hyalina be interpreted as a type of arbuscular mycorrhiza (AM). Implications for systematics and ecology are discussed.Key words: Triuris, Triuridaceae, root structure, anatomy, arbuscular mycorrhiza, myco-heterotrophy.
On an undescribed species of Fibulobasidium
Authors: Bandoni R J
Published: April 2011

A new fungal taxon, Fibulobasidium sirobasidioides Bandoni sp.nov., is described and illustrated. Basidiomata develop beneath the bark of recently dead branches and trunks of Acer macrophyllum Pursh in British Columbia; they are characterized by superficially Sirobasidium-like chains of basidia.Key words: Fibulobasidium, Sirobasidium, Sirobasidiaceae, taxonomy.
Saxifragaceae of the Canadian Arctic Archipelago: a contribution to a DELTA database for interactive identification and illustrated information retrieval
Authors: Aiken Susan G , Dallwitz Michael J , McJannet Cheryl L , Gillespie Lynn J , Consaul Laurie L
Published: April 2011

A re-assessment of members of the family Saxifragaceae in the Canadian Arctic Archipelago is presented as a traditional key and annotated checklist that recognizes 17 taxa. The information on which this paper is based is recorded in a developing DELTA database that aims to collect the following data: place of valid publication; synonymy, usually limited to names that have been associated with the Canadian Arctic; common name(s), if applicable; vegetative and floral morphological characters; data on the distribution, including information about the northernmost record of the taxon; habitat preferences of each species; notes on the species as an environmental indicator; indigenous knowledge; and expanded notes conveying additional information. The database also contains maps, illustrations of characters useful for identification, and colour photographs and line drawings of the taxa. Appendices list characters recorded in the database, brief taxonomic notes, and a sample species description. The data are available on the Internet at http://biodiversity.uno.edu/delta/ as natural-language descriptions and as an INTKEY interactive identification and information-retrieval package for Windows.Key words: Arctic, Canada, DELTA, Internet, Saxifragaceae, taxonomy.
Precipitated iron and manganese plaques restrict root uptake of phosphorus in Lobelia dortmanna
Authors: Christensen Kasper Kjellberg , Sand-Jensen Kaj
Published: April 2011

Plaques of Fe and Mn on root surfaces of submerged aquatic plants are formed in reduced organic sediments with high concentrations of reduced soluble Fe and Mn. Since oxidized metal compounds have a high capacity for P binding, we grew Lobelia dortmanna L. for 6 months on four sediment types, in which the content of organic matter ranged from 0.32 to 1.73%, to test the influence of plaques on assimilation of P and biomass development. Concentration of oxidized Fe and Mn in plaques on Lobelia roots increased significantly with the content of organic matter in the sediment. Lobelia with high concentrations of Fe in the plaques showed very low tissue content of P and low biomass despite the fact that these plants were from the two organic sediments with high concentrations of P. Plants from the two sediments with low content of organic matter and P showed, in contrast, low plaque concentrations but higher biomass and P content. No significant correlations between the content of Fe and Mn in root plaques and in stems and leaves of Lobelia were found. The results suggest that the formation of plaques on Lobelia roots on sediments rich in reduced Fe and Mn restricts uptake of P and biomass production because P is adsorbed to oxidized Fe and Mn in the plaques.Key words: iron plaque, Lobelia dortmanna, macrophyte, organic matter, phosphorus.
Genetic and environmental sources of variation in leaf morphology of Sphagnum fallax and Sphagnum isoviitae (Bryopsida): comparison of experiments conducted in the field and laboratory
Authors: Såstad Sigurd M
Published: April 2011

Gametophores from mixtures of the closely related Sphagnum fallax (H. Klinggr.) H. Klinggr. and Sphagnum isoviitae Flatberg, from two localities were clonally propagated in axenic culture and back transplanted from laboratory to field conditions, as well as reciprocally transplanted between the same localities. Genetic and environmental effects on leaf morphology were estimated to assess the taxonomic merit of these characters. Differences between populations exceeded between-taxon differences and could not be taken as evidence of two separate species. Plastic responses were apparent in the reciprocal transplant experiment, and a species-specific norm of reaction could be discerned in one character. Compared with the field experiments the species- and population-level genetic variances increased in the laboratory. This indicates that increased differences between species and populations were an artefact of experimental conditions, rather than caused by environmental effects opposing genetic effects on morphology in the field. Among-clone variances remained relatively stable across all experiments, as did residual variances indicating that the clonal propagation process did not elevate developmental noise. Contrasting responses between clonally propagated and field collected gametophores provide indirect evidence of changing levels of genetic and plastic variation throughout ontogeny.Key words: cultivation experiment, phenotypic plasticity, phenetics, Sphagnum, morphology.
Arbuscular mycorrhizae promote establishment of prairie species in a tallgrass prairie restoration
Authors: Smith M R , Charvat I , Jacobson R L
Published: April 2011

The effect that arbuscular mycorrhizal (AM) inoculum has on the development of an early successional tallgrass prairie restoration was investigated in field plots of a recently disturbed area in Minnesota, U.S.A. Mycorrhizal inoculum reproduced from a native prairie was placed below a mix of prairie seed. Two sets of control plots were established, those with seed only and those with seed and a sterilized soil. By the end of 15 months, plants in the inoculated plots had a significantly greater percentage of roots colonized by AM fungi. While inoculation had no effect on total percent cover of plants, percent cover of native planted grasses was significantly greater in the inoculated plots than in the two sets of controls. The increase in percent cover of native grasses may increase the rate of succession by allowing these grasses to outcompete the ruderal species also present at the site. Our findings suggest that inoculation with arbuscular mycorrhizae promotes the development of early successional tallgrass prairie communities.Key words: mycorrhizae, prairie, reclamation, plant community, inoculation, restoration.
Does past contact reduce the degree of mutualism in the Alnus rubra - Frankia symbiosis?
Authors: Markham John H , Chanway Chris P
Published: April 2011

Although most vascular plants have symbiotic relationships with soil microbes, and there is an extensive theoretical literature on the evolution of mutualism, there has been little experimental examination of the evolution of mutualism between plants and their microbial symbionts. We inoculated red alder (Alnus rubra Bong.) seedlings from three high- and three low-elevation populations with crushed nodule suspensions containing the nitrogen fixing bacterium Frankia from either the parent trees (familiar strains) or the other plant population sampled within the parent watershed (unfamiliar strains). The inoculated seedlings were planted on three high- and three low-elevation sites. Growth was monitored over the second and third year following planting, after which the whole plants were harvested. The proportion of nitrogen derived from fixation was estimated from the ratio of stable nitrogen isotopes in the harvested leaves. On low-elevation sites, which had high soil nitrogen, plants with familiar Frankia strains were half the size and derived less fixed nitrogen from their symbionts compared with plants inoculated with unfamiliar Frankia strains. On high-elevation sites, which had low soil nitrogen, the type of inoculum had little effect on plant performance, although plants with familiar inoculum were consistently larger than plants with unfamiliar inoculum. These results suggest that the degree of mutualism in this symbiosis depends on environmental conditions and may decrease with time.Key words: coevolution, Frankia, Alnus rubra, mutualism, nitrogen fixation, symbiosis.
Biotic and abiotic characteristics of ecosystems on acid metalliferous mine tailings near Sudbury, Ontario
Authors: Bagatto Giuseppe , Shorthouse Joseph D
Published: April 2011

INCO Ltd., a large mining company near Sudbury, Ont., deposits vast amounts of tailings on its property. These tailings contain elevated levels of Cu, Ni, and sulphides, and to curtail dust and acid drainage, INCO has undertaken a long-term project to cover its tailings with vegetation. Yearly amelioration of fresh tailings with limestone and fertilizer, followed by seeding with various grasses and herbs, transplanted conifers, and the later colonization of volunteer species of plants from adjoining forests, has resulted in the formation of ecosystems of varying age and complexity. To assess the long-term effectiveness of INCO's vegetation techniques, we studied floral diversity, attributes of developing soils, and the accumulation of Cu and Ni in various plant species growing on tailings at different stages of development. Habitat disturbance by tailings deposition, and its subsequent floral recolonizaton, is an example of "anthropogenic succession." Tailings that do not receive amelioration in the form of lime, fertilizer, and seeding remain free of vegetation, other than sparce clumps of the metal-tolerant grass Deschampsia caespitosa (L.) Beauv. Once amelioration begins, various species of grasses and herbs are able to subsist and within 8 years volunteer species begin to colonize. Substrate pH of dried tailings is less than 4 while the pH in upper horizons ranges from 5 to 6, increasing as the sites become more florally diverse; however, pH at lower depths remains less than 4. Substrate organic content in upper horizons at restored sites ranges from 4.5 to 5.0%. Water-soluble concentrations of Cu and Ni in upper horizons ranges from 1 to 5 µg/g dry mass, and 0.5 to 6 µg/g dry mass, respectively, and both metals decrease with increasing floral diversity. Levels of Ni increase at lower depths indicating greater substrate mobility. Levels of Cu and Ni are higher in plants from tailings than in those from control sites; however, concentrations do not decrease in plants from older and more florally diverse tailings sites. Root tissues contain significantly higher concentrations of Cu and Ni than aerial tissues. Monitoring air with moss plates indicates that dispersal of airborne metallic dust remains a problem.Key words: mine tailings, Sudbury, anthropogenic succession, copper, nickel, acid, monitoring.
Effect of culture media on antheridial configuration in Phytophthora boehmeriae
Authors: Gao Z M , Zheng X B , Lu J Y , Ko W H
Published: April 2011

The position of the antheridium on the oogonium of Phytophthora boehmeriae was greatly affected by culture media. Agar medium containing lecithin and basal salts and corn grain agar favored the production of paragynous antheridia, while corn meal agar, lima bean agar, vegetable juice agar, and tomato agar were conducive to formation of amphigynous antheridia. The effect of culture media on antheridial configuration was found to be due to nutrient concentration. A high concentration of nutrients in the media was favored the formation of amphigynous antheridia, and a low concentration of nutrients favored paragynous antheridia.Key words: antheridial configuration, oogonium, nutrients, Phytophthora boehmeriae.
Genetic evidence that butternut canker was recently introduced into North America
Authors: Furnier Glenn R , Stolz Allison M , Mustaphi Raka M , Ostry Michael E
Published: April 2011

Butternut (Juglans cinerea) is seriously threatened by a canker disease caused by Sirococcus clavigignenti-juglandacearum, a fungus with no known sexual stage. This pathogen was first reported in 1967 and is now found throughout the native range of butternut, suggesting that it was introduced into North America. We used randomly amplified polymorphic DNA (RAPD) markers to examine genetic variation in S. clavigignenti-juglandacearum over a large portion of the native range of butternut. The 55 RAPD fragments were all found in all 86 isolates of the fungus. This complete monomorphism is consistent with the fungus having been introduced into North America as a single isolate and suggests that if resistant butternut genotypes are found, the pathogen will not likely be able to rapidly evolve genotypes that can attack them.Key words: Sirococcus clavigignenti-juglandacearum, Juglans cinerea, RAPD, randomly amplified polymorphic DNA.
Histopathology of Albugo tragopogonis on stems and petioles of sunflower
Authors: Krüger H , Viljoen A , Van Wyk P S
Published: April 2011

Stem lesions in sunflower caused by Albugo tragopogonis (Pers.) S.F. Gray developed individually from primary infections and did not result from a systemic infection. Cell division and callose formation were not observed, but weak lignin deposition occurred in infected tissues. Hyphae occurred intercellularly in stems in the cortex, cambium, vascular rays, and pith. In petioles parenchymatous tissue was heavily colonized in contrast to lightly colonized collenchymatous hypodermis. The middle lamellae of cells in infected tissue were dissolved, and cells degenerated and eventually collapsed. Stem infections lead to deterioration of tissue integrity, weakening of stems, and finally to lodging of stems (breaking over).Key words: Albugo tragopogonis, Helianthus annuus, histopathology, stem lodging.
Histochemical and microspectrophotometric analyses of early wound responses of resistant and susceptible Populus tremuloides inoculated with Entoleuca mammata (=Hypoxylon mammatum)
Authors: Bucciarelli B , Ostry M E , Fulcher R G , Anderson N A , Vance C P
Published: April 2011

Stem tissue of resistant and susceptible genotypes of Populus tremuloides Michx. wounded or wound-inoculated with Entoleuca mammata (Wahlenberg: Fr.) J.D. Rogers & Y.-M. Ju was prepared for histochemical and microspectrophotometric analysis. Samples were collected over a 96-h period. Parenchyma cell walls associated with the response zone of infected resistant and susceptible genotypes accumulated phenolic substances having lignin-like properties. Features of the lignified zone distinguished resistant from susceptible genotypes. This zone in the resistant genotype was uniformly lignified, while in the susceptible genotype, it was discontinuous. Wound callus developed in the infected resistant but not in the susceptible genotype. In the former, callus developed internal to the lignified zone, contained phenolic substances, and was visible 48 h after inoculation. In the susceptible, callus failed to develop. Wounded tissue of both genotypes displayed no distinguishing response characteristics. Both produced equivalent amounts of callus, accumulated similar levels of lignin-like substances, and deposited it in identical locations. It is concluded that resistant P. tremuloides limits infection by E. mammata by two distinct mechanisms: (i) by the development of an intact and localized lignified barrier zone and (ii) by the development of wound callus rich in phenolic substances. The susceptible is ineffective at developing either of these barriers.Key words: aspen, Hypoxylon canker, disease resistance.
Translocation and incorporation of strontium carbonate derived strontium into calcium oxalate crystals by the wood decay fungus Resinicium bicolor
Authors: Connolly Jon H , Shortle Walter C , Jellison Jody
Published: April 2011

The white-rot wood decay fungus Resinicium bicolor (Abertini & Schwein.: Fr.) Parmasto was studied for its ability to solubilize and translocate ions from the naturally occurring mineral strontianite. Resinicium bicolor colonized a soil mixture culture medium containing strontianite sand, solubilized strontium ions from this mineral phase, translocated the ions vertically, and reprecipitated the strontium into strontium-containing calcium oxalate crystals. Storage of the Sr in crystals was highest in mycelial cords and was dynamic in character. These results suggest that non-mycorrhizal saprotrophic fungi should be evaluated for their potential participation in forest nutrient cycling via biologically weathering parent material and translocating the mobilized mineral nutrients vertically within soils.Key words: fungi, strontium, calcium oxalate, translocation, soil, minerals nutrient cycling.
Morphologie et ultrastructure du pollen dans le genre Utricularia L. (Lentibulariaceae)
Authors: Lobreau-Callen Danielle , Jérémie Joël , Suarez-Cervera Maria
Published: April 2011

This palynological study of the genus Utricularia (Lentibulariaceae) deals with 39 species spread through 26 of the 35 sections that compose the genus. The pollen varies from tricolporate to zonocolporate or to zonoporate. The tectum is smooth, rarely ornamented (SEM). Nine pollen types are distinguished of which six have been studied with the TEM. The tectum is regular, the infratectum generally granular. The foot-layer is thick if the number of apertures is reduced and thin or absent if the endoapertures form an endocingulum. The endexine is thick if the foot-layer is thin, and made up of lamellae and rarely of costae bordering the endoapertures. In the porate pollen, the foot-layer and endexine are absent. Diverse in the terrestrial and lithophytic species, the pollen tends to be oblate and planaperturate in the epiphytes, zonocolporate with numerous apertures in the floating aquatic species, and ornamented in those of flowing water. The species considered the most primitive are terrestrial with tricolporate pollen. All the other types are derived, especially those with a significant increase in the number of apertures, associated or not with the absence of a foot-layer or an endexine. In the genus Utricularia and the Lentibulariaceae in general, the variation in pollen is much less related to habitat than to the evolutionary history of each species.Key words: pollen, morphology, exine, ultrastructure, Utricularia, Lentibulariaceae.
Ultrastructural and cytochemical study of colonization of xylem vessel elements of susceptible and resistant Dianthus caryophyllus by Fusarium oxysporum f.sp. dianthi
Authors: Ouellette G B , Baayen R P , Simard M , Rioux D
Published: April 2011

The colonization processes of the xylem in the susceptible carnation cv. Early Sam and the resistant cv. Novada were studied ultrastructurally following inoculation with Fusarium oxysporum f.sp. dianthi. Samples from 1 to 3 cm above the incision were collected over 5 weeks and processed following conventional procedures as well as with probes for cellulose, N-acetyl-glucosamine, and pectin. The fungus grew profusely in the vessel lumina of the susceptible cultivar. Some of the colonized vessels were lined with coating material connected to the fungal cell wall and extending into the host cell wall through microfilamentous-like structures. Coatings did not label for pectin or cellulose. The pathogen crossed from one vessel element to another (and at times to parenchyma cells) usually directly through pit membranes; often the invading structures of the fungus appeared to be either only membrane-bound or formed solely of microfilamentous-like entities. The fungus subsequently invaded extensively, generally by means of microhyphae, the vessel intercalary walls from the pit membranes and vessel wall junctures. Microhyphae had thin or imperceptible walls and contained only some of the normal cytoplasmic components. Initially, the invading hyphae dislocated the host cell walls, apparently mechanically more than by lysis; however, more pronounced lysis occurred following general tissue invasion. Host parenchyma cells seemed relatively unaffected, even after the surrounding walls had undergone severe degradation. Colonization of resistant plants was restricted. Degradation of tissues did not occur and microhyphae were not observed. Inoculated vessel elements in the 'Novada' plants contained numerous fungal cells and little occluding material, whereas the surrounding vessels were almost completely occluded. The initially invaded xylem became tangentially compartmentalized by parenchyma cell wall thickenings and by hyperplastic parenchyma. Occasionally, hyperplastic tissues were slightly re-invaded, forming secondary invasion pockets. Vessel-occluding material varied in structure and opacity, not only from vessel to vessel but also within the same vessel, and contained microfilamentous-like structures and other types of fine fibrillar material. Some vessel elements in or near the secondary invasion pockets contained only the finer fibrils that reacted strongly with an antibody specific for pectin. Vessel elements rarely contained tyloses.Key words: cellulose, chitin, Dianthus caryophyllus, Fusarium wilt, gels and gums, host wall degradation, microhyphae, pectin, tyloses.
Surface pollen spectra from southern Vancouver Island, British Columbia, Canada
Authors: Allen Gregory B , Brown Kendrick J , Hebda Richard J
Published: April 2011

Analyses of surface samples of 84 sites from southern Vancouver Island were used to characterize pollen and spore spectra of modern vegetation types. Xeric Quercus garryana Dougl. and grassland associations can be identified by Quercus pollen and abundant nonarboreal pollen, respectively. Coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) forests are distinguished by high proportions of Pseudotsuga and low Pseudotsuga to Tsuga heterophylla (Raf.) Sarg. ratios. Coastal Western Hemlock zone forests have abundant Tsuga heterophylla pollen. Dry Coastal Western Hemlock subzones have diagnostically abundant Pseudotsuga and Tsuga heterophylla pollen, and intermediate Pseudotsuga to Tsuga heterophylla ratios. Moist Coastal Western Hemlock variants are characterised by little or no Pseudotsuga pollen and high Pseudotsuga to Tsuga heterophylla ratios. The Mountain Hemlock zone exhibits abundant Tsuga mertensiana (Bong.) Carr. pollen percentages and notable nonarboreal pollen and spore values. Relatively high Alnus values are not necessarily indicators of dominant alder stands, especially when obtained from open communities. Pseudotsuga to Tsuga heterophylla ratios are useful as a proxy measure of mean annual precipitation between 700 and 2700 mm.Key words: pollen and spores, surface spectra, Vancouver Island, biogeoclimatic zone, vegetation, precipitation.
Thelocarpella gordensis gen. et sp. nov. (Ascomycetes lichenisati, Acarosporaceae)
Authors: Navarro-Rosinés Pere , Roux Claude , Bellemère André
Published: April 2011

Thelocarpella gordensis Nav.-Ros. et Cl. Roux gen. et sp. nov., a crustose lichen with endolithic thallus, is only known from the type locality, in Provence (south-east of France), on calcareous sandstone. This species is characterized by entirely immersed perithecioid ascomata, a hamathecium consisting of a typical paraphysoid network, multispored asci (more than 1000 spores in optical section), and colourless small oblong spores. The genus Thelocarpella differs from Thelocarpon by having bitunicate asci with a distinctly thicker wall. Heterogeneity of the genus Thelocarpon and the systematic position of Thelocarpella and Thelocarpon are discussed. The genus Trimmatothelopsis Zschacke is considered a synonym of Acarospora A. Massal. and Thelocarpon robustum Eitner identical with Acarospora smaragdula var. murina (Sandst.) H. Magn.Key words: lichens, Thelocarpella, Thelocarpon, taxonomy.
Identification of a protein secreted by the blister rust fungus Cronartium ribicola in infected white pines and its cDNA cloning and characterization
Authors: Ekramoddoullah Abul Kalam Mohammed , Tan Yingchun , Yu Xueshu , Taylor Doug William , Misra Santosh
Published: April 2011

Previously we showed that a white pine protein Pin m III (a member of PR10 family of pathogenesis-related proteins) is up-regulated by infection in the white pine blister rust pathosystem. In this study, a blister rust fungal protein, Cro r I, which is similar in size to Pin m III (19 kDa), was detected in the infected white pine tissues. The N-terminal amino acid sequence of Cro r I isolated from infected pine foliage and from fungal mycelia was identical. Rabbit antibody was prepared to a synthetic N-terminal peptide and was purified by immunoaffinity. The purified antibody was used in a Western immunoblot to quantify the amount of Cro r I in various tissues. In western white pine seedlings the amount of Cro r I was significantly (p < 0.0001) higher in infected tissues of cankered seedlings than the infected tissues of resistant seedlings. In sugar pine seedlings, the amount of Cro r I was also significantly (p < 0.01) higher in infected tissues of susceptible seedlings than in resistant seedlings. Furthermore, Cro r I is secreted by the blister rust fungus and was found to be translocated to the healthy tissues of cankered white pines. Cro r I is a major protein that could be extracted from infected foliage by vacuum infiltration. The level of Cro r I detected in the mycelium of different isolates varied. The cDNA of Cro r I was isolated by reverse transcription - polymerase chain reaction. Comparison of the DNA sequence and the deduced protein sequence with data bases revealed that it is a previously undescribed protein. The calculated molecular weight from the deduced protein sequence of Cro r I was 16.7 kDa and the calculated isoelectric point was 9.55. Protein sequence analysis showed that Cro r I has two potential N-linked glycosylation sites in its sequence.Key words: translocation, elicitor, antibody, amino acid sequence.
Contrasting dispersal phenologies in two fleshy-fruited congeneric shrubs, Rhus aromatica Ait. and Rhus glabra L. (Anacardiaceae)
Authors: Li Xiaojie , Baskin Jerry M , Baskin Carol C
Published: April 2011

The avifrugivore availability hypothesis predicts that summer-fruiting species will have an extended fruiting season and slow fruit removal, and the foliar flag hypothesis predicts that fruit dispersal in autumn-fruiting species coincides with fall bird migration. Phenology of fruit removal from plants of the early summer-fruiting shrub Rhus aromatica Ait. (var. aromatica) and of the later summer-fruiting shrub Rhus glabra L. (Anacardiaceae) was studied primarily to test the avifrugivore availability and foliar flag hypotheses of fruit dispersal, respectively. Fruits of R. aromatica ripened synchronously in early June, and 77-89% of them were gone from the plants by the early July, thus failing to support the avifrugivore availability hypothesis. The pattern of rapid fruit removal in this species, which was consistent throughout a 3-year period, is in contrast with previous reports of dispersal until September and even the next summer. Display size (at both infructescence and clump levels) had no effect on removal rate in R. aromatica. Fruits of R. glabra matured in August, and about 20% of them remained undispersed the following spring. In both species, fruit removal was mostly due to dispersers rather than to natural fruit fall. No correlations were found between fruit characteristics (pulp weight, pulp-to-seed ratio, moisture content of pulp) and probability of removal during the dispersal season in either species. Browsing by mammals, most likely white-tailed deer, was responsible for the rapid removal of fruits from R. aromatica plants during the 1st week after they turned mature-red; thereafter, most fruit removal was by birds. Two removal peaks were found for R. glabra fruits: a small one in September and a large one in winter to early spring. These peaks correspond to the fall migration season for migratory birds and the scarcity of food for winter-resident birds, in the study area, respectively. Thus, the dispersal pattern of R. glabra fruits does not support the foliar flag hypothesis.Key words: avifrugivore availability hypothesis, foliar flag hypothesis, fruit characteristics, fruit dispersal by birds or mammals, fruiting phenology, Rhus aromatica, Rhus glabra.
Dominance ofFrankiastrains in stands ofAlnus incanasubsp.rugosaandMyrica pensylvanica
Authors: Clawson Michael L , Gawronski Jeffrey , Benson David R
Published: April 2011

To address issues of dominance and diversity of Frankia spp. strains, we sequenced 16S rRNA genes from root nodules and strains collected from Alnus incana subsp. rugosa (Du Roi) R.T. Clausen and Myrica pensylvanica Loisel. stands. Of 22 strains isolated previously from A. incana, 16 had the same partial rDNA sequence; the remaining 6 strains composed five additional groups. The groups identified by 16S rDNA analysis corresponded to phenotypic groups established previously by one- and two-dimensional polyacrylamide gel analysis, colony and hyphal morphology, and carbon source utilization patterns. Dominance of one strain was also evident in nodules collected from a single M. pensylvanica stand. The dominant strain had a partial 16S rDNA sequence identical to that of Frankia alni strain CpI1.Key words: Frankia, Myrica, Alnus, actinorhizal, root nodules, nitrogen fixation, symbiosis, 16S rRNA.
In vitro culture of arbuscular mycorrhizal fungus and Frankia for inoculation of micropropagated Casuarina equisetifolia L.
Authors: Mark Genevieve Louise , Hooker John E , Hahn Alexander , Wheeler Chris T
Published: April 2011

Micropropagated, rooted, and calli explants of Casuarina equisetifolia L. were inoculated with Frankia UGL 020605S and the arbuscular mycorrhizal fungus (AMF) Glomus mosseae, in single and dual co-culture, in vitro. Different micropropagation media formulations were evaluated for their capacity to stimulate germination of G. mosseae spores and growth of Frankia. Murashige and Skoog basal nutrient (half strength) medium, supplemented with 6-benzylaminopurine (BAP), 2,4-dichlorophenoxyacetic acid (2,4-D), and pyruvate was selected for the in vitro co-culture of C. equisetifolia callus explants, G. mosseae, and Frankia. This medium (M4) supported 70% AMF spore germination with 44 and 34% of the germinating spores producing single and branched hyphal strands, respectively. Hoaglands (quarter strength, modified by Hoaglands and Arnon (1950)) nutrient medium (M5) with no supplements was selected for the in vitro co-culture of rooted C. equisetifolia explants, G. mosseae, and Frankia and supported 57% AMF spore germination with 29 and 40% of the germinating spores producing single and branched hyphal strands, respectively. Both media supported significant growth of Frankia. In both cases agar was substituted with Terragreen(r). AMF appressoria and intercellular hyphae were observed in rooted C. equisetifolia at 28 days; arbuscule formation occurred at 56 days postinoculation. Frankia infection was evident after 28 days. This was observed in both dual and single in vitro co-cultures. No specific immunofluorescent or immunogold reactions to monoclonal antibodies (mABs) anti-Frankia < 8C5 > and anti-G. mosseae < F5G5 > were evident in C. equisetifolia callus explants.Key words: arbuscular mycorrhizal fungi (AMF), Frankia, Casuarina, micropropagation, immunofluorescent labelling.
Effects of the exposure of roots of Alnus glutinosa to light on flavonoids and nodulation
Authors: Hughes M , Donnelly C , Crozier A , Wheeler C T
Published: April 2011

Exposure of the roots of Alnus glutinosa (L.) Gaertn. to white light stimulated within 5 days a substantial increase in the content of quercetin and kaempferol, two major flavonols in acid hydrolysates of both roots and root exudates. Both compounds were detected also in hydrolysates of root extracts of Myrica gale and Casuarina equisetifolia, the latter a species not nodulated by Frankia strains effective on Alnus. A 7-fold reduction in nodulation of seedlings 12 days after inoculation with Frankia preincubated for 24 h with kaempferol supported the possibility that flavonols might be involved in the regulation of nodulation. Nodulation of seedling roots that were inoculated with Frankia and then exposed to light was inhibited by 50% after 11 days compared with seedlings with darkened roots. This effect of light treatment was preceded by a 30-fold increase in quercetin and kaempferol. The inhibitory effects on nodulation of preincubation of Frankia with kaempferol persisted for 18 days after inoculation, but there was no significant effect on nodulation after prolonging exposure of the root system to light for 40 days. The data support indirectly the suggestion that the balance between stimulatory and inhibitory flavonoids in roots and root exudates may contribute to the regulation of nodulation of actinorhizal plants.Key words: Alnus glutinosa, flavonoids, Frankia, kaempferol, nodulation, roots.
Nucleotide sequences of the 2-oxoacid ferredoxin oxidoreductase and ferredoxin genes fromFrankiastrain EuIK1, a symbiont ofElaeagnus umbellataroot nodules
Authors: Yoo Won Young , Sung Si Bum , An Chung Sun
Published: April 2011

A genomic clone, pEuNIFII, was isolated by screening a genomic library of Frankia strain EuIK1, a symbiont of Elaeagnus umbellata Thunb. root nodules. A 1.5-kb fragment of pEuNIF4.0, which contained ORF2 and N-terminal part of nifS, was used as a probe. A 7.2-kb BamHI fragment of pEuNIFII, which was proven to be adjacent to the probe, was subjected to sequence determination. The sequence analysis suggested one partial ORF followed by three open reading frames (ORFs). Two ORFs next to nifS encodes an a subunit (672 amino acids) and b subunit (347 amino acids) of a 2-oxoacid ferredoxin oxidoreducatase (OR), respectively. The third ORF encodes 114 amino acids of a 7Fe-type ferredoxin (Fdx). All ORFs are transcribed in the same direction as other nif genes. Alignment of the deduced amino acid sequences from frankiae OR revealed the motifs of gamma and alpha domains seen in other ORs in the a subunit, and the beta domain in the b subunit. Frankia or shows about 44% nucleotide sequence similarity with nifJ from Klebsiella pneumoniae, while frankiae fdx shows about 56% similarity with fdxI from Azotobacter vinelandii. These genes are reported for the first time in Frankia, and putative roles of their products in symbiosis is discussed in relation to nitrogen fixation and carbohydrate metabolism.Key words: 2-oxoacid ferredoxin oxidoreductase, ferredoxin, nucleotide sequence, Frankia EuIK1.
Soil seed banks in young, closed-canopy forests of the Olympic Peninsula, Washington: potential contributions to understory reinitiation
Authors: Halpern Charles B , Evans Shelley A , Nielson Sarah
Published: April 2011

During early stand development, coniferous forests of the coastal Pacific Northwest commonly pass through a period of dense shade and intense competition during which the abundance and diversity of understory plants decline dramatically. In young, managed forests, silvicultural thinning has been proposed to enhance the structural and floristic diversity of the understory. Although germination of buried seeds is likely to be stimulated by thinning, we know little about the composition of the soil seed bank in these forests. We used the greenhouse emergence method to assess the potential contribution of the seed bank to understory reinitiation in 40- to 60-year-old, closed-canopy forests on the Olympic Peninsula, Washington. Seed banks were well developed (610-7009 germinants/m2), containing 46 native and exotic species representing a diversity of life forms. However, many common forest understory species were absent; only 11 species were typical understory plants and these comprised <10% of all germinants. In contrast, 30% of all species and 50% of all germinants were exotic, ruderal forbs. Wind-dispersed annuals and perennials dominated litter samples, whereas ruderal forbs and graminoids with limited dispersal dominated soil samples. Our results suggest that silvicultural thinning will enhance the establishment of ruderal, exotic species but will contribute little to the regeneration from buried seed of the vast majority of forest understory plants.Key words: canopy closure, forest understory, seed germination, soil seed bank, succession, understory reinitiation.
How does density and nutrient stress affect allometry and fruit production in the heterocarpic species Atriplex sagittata (Chenopodiaceae)?
Authors: Mandák Bohumil , Pyek Petr
Published: April 2011

Plants of Atriplex sagittata Borkh. were grown under different density and (or) nutrient conditions, and the effect of stress on plant allometry and variation in particular biometrical parameters was studied. Increasing density significantly reduced total weight, basal diameter, stem length, and number of branches. Nutrient deficiency had a negative effect on the total weight and basal diameter only, and the density × nutrients interactions were all nonsignificant. Basal diameter was the best predictor of the total weight, explaining 93.6% of the variation in the whole data set. The relationship between total plant weight and basal diameter was unaffected by growth conditions, indicating that competition determined the position of a plant along the line describing the allometric relationship between both variables but did not seem to alter the relationship. However, the allometric relationships between total weight and stem height and between total weight and number of branches found at low density were significantly different from those at high density, indicating a faster increase in total weight at low densities. Branching, and consequently plant form, were affected by competition. Branch length consistently increased with total plant weight in plants grown under high density, but for low density plants, such an increase was recorded only in branches of the middle section of the stem. In each fruit type, the total weight of fruits produced was more closely predicted by branch weight than by branch length. Allometric relationships between fruit production and branch weight differed among particular fruit types, with a faster increase in the production of type A than in that of types B or C. Competition had less effect on the mean size of type B fruits compared with that of types A or C. Fruits of types C and A had higher variation in mean weight, than type B fruit. Variation in total weight of fruits per plant was of a higher order of magnitude than that in the mean fruit weight. The results show that plants of A. sagittata grown under contrasting conditions change both their allometry and the number of particular fruit types produced. Nevertheless, the question of whether the shift in the fruit ratio is a function of allometric constraints or the result of a basic shift in allometry needs further study.Key words: allometry, Atriplex sagittata, Chenopodiaceae, density stress, nutrient stress, heterocarpy.
Role of gibberellins in the development of floral organs of the gibberellin-deficient mutant, ga1-1, of Arabidopsis thaliana
Authors: Goto Nobuharu , Pharis Richard P
Published: April 2011

The gibberellin-deficient mutant, ga1-1 (NG5) of Arabidopsis thaliana, when induced by 16-h-long days, will form floral buds. However, the flower stalk is very short and floral organs within the flowers remain undeveloped; petal growth is arrested, with the petals being scaly and translucent, the stamens are abortive, the filaments do not elongate, and the pollen does not mature. Sepals and pistils are also underdeveloped. All of the above defects of this mutant can be completely eliminated if certain gibberellins (GAs) are applied to the young floral buds. That is, the applied GA acts to normalize not only plant height but also development of floral organs, thereby yielding good seed set from self-pollination. There were appreciable differences in the efficacy of different GA structures in normalizing the various floral organs. For seed production, the order of efficacy was 2,2-dimethyl GA4 > GA7 > GA3 = GA4 > GA1 > GA5 = GA9. When 2,2-dimethyl GA4 was used to determine an optimal GA dose, the following pattern emerged: filament elongation and pollen development, 1-10 ng; petal and pistil growth, 1 ng; sepal growth, 0.1 ng; papilla elongation, 0.01 ng. However, one application at these doses was insufficient to normalize the flowers, which were formed one after another, and a continuing supply of GA at the optimal dose was required for normal flower development and seed set. We conclude from this work that GAs play an essential role in the development of floral organs of Arabidopsis and that petals and stamens (filaments and pollen) in particular develop normally only when GAs are present at the optimal level.Key words: Arabidopsis thaliana, floral organ development, gibberellin, gibberellin-deficient mutant, petal and pollen development, reproductive function.
Management issues in aquatic macrophyte ecology: a Canadian perspective
Authors: Chambers Patricia A , DeWreede Robert E , Irlandi Elizabeth A , Vandermeulen Herbert
Published: April 2011

During the past few decades, attempts to manage excessive abundance of freshwater macrophytes, decreasing abundance of marine eelgrass (Zostera marina L.), and abundance and diversity of seaweeds have yielded modest successes, some short-term recoveries, and other complete failures. As many broad principles apply to the management of all aquatic plants, the aim of this paper was to synthesize the issues and provide direction for the management of freshwater rooted macrophytes, eelgrass, and marine macrophytic algae and place them in a Canadian context. Specifically, we examine biomass and landscape objectives for macrophyte management, assess the role of environmental manipulation for the management of macrophyte assemblages, and provide direction for managing macrophyte assemblages within the context of ecosystem sustainability. Finally, we advocate that, given the unexpected outcomes that may arise from uncontrolled events (e.g., weather, inherent variability in life history characteristics), management interventions should be designed in such a way that it is possible to make valid conclusions about the outcome of any given management action (i.e., design the management action to be a scientific experiment).Key words: macrophyte, algae, eelgrass, herbivores, nutrients, landscape ecology.
The inheritance of mating type and growth rate inChoanephora cucurbitarum
Authors: Yu Ming-Qiu , Ko Wen-Hsiung
Published: April 2011

When isolates of Choanephora cucurbitarum (Berk. & Rav.) Thaxt with similar growth rate and colony appearance were crossed, the mating-type distribution of zygospore progeny fit the ratio of 1(+):1(-):2(+,-). However, germsporangiospore progeny from the same pairs fit a 1(+):1(-) ratio but not a 1(+):1(-):2(+,-) ratio. When isolates with different growth type (F for fast and S for slow) were crossed, the resulting zygospore progenies fit a 1(+):1(-) ratio but not a 1(+):1(-):2(+,-) ratio. Their growth type distribution also fit a 1F:1S ratio. All the sporangiospores tested were multinucleate.Key words: genetics, heterokaryon, mating type, segregation, zygospores.
Long-term reconstruction of the fire season in the mixedwood boreal forest of Western Canada
Authors: Johnson E A , Miyanishi K , O'Brien N
Published: April 2011

Climate modelling studies have predicted an increase in fire frequency with global warming as well as suggesting a longer fire season occurring later in the year. We used 160 years of fire scars in Pinus banksiana Lamb. dating from 1831 to 1948 and written fire records from 1927 to 1995 for Prince Albert National Park in the southern boreal forest to look for evidence of changes in the duration and timing of the fire season (defined as the months when large areas burn) that may have accompanied past changes in fire frequency. The Park's time-since-fire distribution had indicated two such changes: one around 1890 and the other around 1945, both in the direction of decreasing fire frequency. Both fire scars and written fire records indicated that the dominance of the spring fire season (April-June) has remained unchanged over the past 160 years. A small number of scars suggested that the fire season may have extended slightly into the summer (July) prior to 1890 when the fire cycle was much shorter and that the fire season may have shifted to a slightly earlier spring start after 1945 when the fire cycle was much longer.Key words: fire season, boreal forest, fire frequency.