bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation of chloroplast envelopes from Dunaliella tertiolecta
Authors: Goyal Arun , Thielmann Jens , Tolbert N E
Published: April 2011

Techniques have been developed to obtain Dunaliella chloroplasts and their outer and inner envelopes in high yield. With purified envelopes, we have identified two integral membrane proteins that are specifically induced by low CO2. These two proteins are located in the inner envelope, which is the proposed site for the active dissolved inorganic carbon transporter in unicellular green algae.Key words: algae, carbon concentration mechanism, chloroplast envelopes, dissolved inorganic carbon, Dunaliella, low CO2 induced proteins.
The plant communities of a foredune in southeastern Brazil
Authors: Henriques Raimundo Paulo Barros , Hay John DuVall
Published: April 2011

Species composition, biomass and environmental characteristics of a coastal plant community of southeastern Brazil, was studied using data from 110 quadrats collected on the foredune of Barra de Maricá, Rio de Janeiro, Brazil. Indirect and direct gradient analyses were used to describe the foredune community. Ordination by detrended correspondence analysis (DCA) indicated the existence of three vegetation groups: pioneer, embryo dunes and a zone of fixed dunes with blow out areas. The gaps observed between groups were attributed to discontinuities in environmental factors. Most of the variation in species composition was expressed by the second axis of the DCA ordination, which was correlated with the distance from the beach bank. The second axis is interpreted as a stress gradient, with high stress in the pioneer zone decreasing to fixed dunes. The coenocline analyzed by direct gradient ordination, was divided into three segments equivalent to Groups detected by DCA ordination. The important species were: Althernanthera maritima St. Hil. in the pioneer zone, and Sporobolus virginicus (L.) Kunth, Mariscus pedunculatus (R. Brown) T. Koyama, and Mitracarpus frigidum K. Sch. in the embryo dunes. The grassPanicum racemosum (Spreng) was associated with areas of fixed dune. that were also characterized by Mollugo verciticillata L. Both biomass and species richness were lower at the high stress disturbance ends of the gradient, with their maximum value in different portions of the middle range of the gradient.Key words: detrended correspondence analysis, direct gradient analysis, foredune communities, vegetation zonation.
New taxa and combinations of aquatic hyphomycetes
Authors: Descals Enrique , Marvanová Ludmila , Webster John
Published: April 2011

Actinosporella nom.nov. is proposed for Actinospora, a homonym of a plant genus. Anguillospora furtiva sp.nov. and Anguillospora rosea sp.nov. are described with their teleomorphs, respectively in Pezoloma and Orbilia (Leotiales). Gemmulina gen.nov. is erected for Tricellula botryosa, Variocladium gen.nov. for Scorpiosporium rangiferinum and Tricladium giganteum, and Ypsilina gen.nov. for Volucrispora graminea.Key words: aquatic hyphomycetes, conidial fungi, taxonomy, nomenclature.
L'osmorégulation et la régulation de l'eau dans les protoplastes de tubercules de radis (Raphanus sativus)
Authors: Cailloux Marcel , Do Chi Bao
Published: April 2011

In the present work it is found that protoplasts of the radish tuber with a disorganized cytoskeleton, thus dead, subjected to a hypotonic shock, obey the law of osmosis, while healthy ones absorb 6% more water. This means that some events related to metabolism are responsible for this difference. Furthermore, stimulating metabolism, by action on the Krebs cycle, results in absorption of water, while slowing it with an inhibitor of oxydative phosphorylation results in loss of water by the cells. It is concluded that a hydraulic control of turgor, modulated by the intensity of respiration, exists in these cells. This is probably due to a mechanism similar to that of osmoregulation. We call it hydroregulation.Key words: osmoregulation, water intake, water excretion, turgor, hydroregulation.
Changes in terpene content and emission in potted Mediterranean woody plants under severe drought
Authors: Llusià J , Peñuelas J
Published: April 2011

Terpene concentration and emission were studied in potted plants of some of the most common Mediterranean woody species (Pinus halepensis L., Pistacia lentiscus L., Cistus albidus L., Cistus monspeliensis L., Quercus ilex L., Quercus coccifera L., Phillyrea latifolia L., Phillyrea angustifolia L., and Arbutus unedo L.) under irrigation and under severe drought conditions that dropped relative water content to a range between 40% in Q. ilex and 85% in Phillyrea latifolia after withholding watering for one dry summer week. Terpene concentrations were detected in Pinus halepensis, Pistacia lentiscus, C. albidus, and C. monspeliensis, and they increased after withholding watering except in C. albidus. Terpene emission was detected in all species except Phillyrea angustifolia and A. unedo. Pinus halepensis showed the highest diurnal terpene emission rates of 86 µg·g-1 dry wt.·h-1 followed by C. albidus, Pistacia lentiscus, Q. ilex, Q. coccifera, Phillyrea latifolia, and C. monspeliensis (4 µg·g-1 dry wt.·h-1). Emitted terpenes represented from 0.33% of C fixed in C. monspeliensis to 10% in C. albidus. All species severely decreased their terpene emission rates under severe drought conditions. Emission by terpene-storing species (e.g., Pinus halepensis) was more related to temperature than in nonstoring species (e.g., Q. ilex), which showed emission relationships with photosynthetic rates. The monoterpenes alpha-pinene, beta-pinene, beta-phellandrene, and limonene and the sesquiterpene caryophyllene were the most abundant terpenes stored and emitted by these Mediterranean plant species.Key words: drought, Mediterranean conditions, terpene concentration, terpene emission, woody plants.
Taxonomy of Orphnodactylis kalmiae gen. et sp.nov. influenced by the hyperparasite Didymosphaeria kalmiae
Authors: Malloch David , Mallik Azim
Published: April 2011

The holotype of Dothidea kalmiae Peck, putitive cause of the twig blight disease of Kalmia angustifolia (Ericaceae) in North America, was examined and found to contain two species of ascomycetes. The original diagnosis of D. kalmiae included elements of both fungi. Additional material from other parts of North America were also examined and found to contain these two fungi. The two ascomycetes are determined to be (1) a member of the Phyllachoracecae characterized by black stromata and parasitic on Kalmia spp., and (2) a member of the genus Didymosphaeria parasitic in the ascomata of the first species. For reasons of nomenclatural stability and the availability of useful holotypes, Dothidea kalmiae is chosen to represent the hyperparasite and transferred to Didymosphaeria as Didymosphaeria kalmiae (Peck) Malloch and Mallik comb.nov. The species causing the twig blight is described as the type of the new genus and species Orphnodactylis kalmiae. Phyllachora wittrockii, the agent of a similar disease of Linnaea borealis (Caprifoliaceae), is transferred to Orphnodactylis as Orphnodactylis wittrockii (Erikss.) Malloch and Mallik. Two coelomycetes, members of the genera Diplodina and Phoma recorded in stromata of O. kalmiae by previous workers are described and illustrated. The life history of O. kalmiae is discussed briefly.Key words: Kalmia, sheep laurel, Didymosphaeria, Orphnodactylis, Phyllachora, hyperparasitism.
Induction of "filamentous structures" in wild type Antirrhinum majus flowers by benzylaminopurine
Authors: Blahut-Beatty Laureen M , Bonham-Smith Peta C , Sawhney Vipen K
Published: April 2011

The cytokinin, N6-benzylaminopurine (BAP), when applied to young inflorescences of wild-type Antirrhinum majus L., resulted in the formation of chimeric "filamentous structures" in the dorsal region of the third whorl, the position where a stamen primordium is suppressed in wild-type flowers. In addition, BAP induced similar filamentous structures in between the first and second whorls, and this response was concentration dependent. The basal region of the filamentous structures was similar to the filament of a stamen, while the distal portion resembled a petal. These observations suggest that cytokinins may be site-specific factors involved in the regulation of floral organ identity genes or genes that control floral symmetry, i.e., the CYCLOIDEA gene.Key words: Antirrhinum, benzylaminopurine, cytokinin, filament, floral genes, staminode.
Branches versus stems in woody plants: control of branch diameter growth and angle
Authors: Wilson Brayton F
Published: April 2011

The results of three studies at different stages of branch development demonstrated the importance of apical control of diameter growth in both stem formation and branch angle. Diameter growth is controlled by competition between branches and the stem for branch-produced photosynthate. Apical control of branch angle occurs only in species that can produce differential growth stresses. In those species, upward bending is largely regulated by the amount of branch diameter growth. The first study followed stem formation from current shoots in Kalmia latifolia L., a shrub without terminal buds or apical control of branch angle. When several current or older shoots were competing, the longest, most distal lateral shoot usually became the stem. Shoot angle was poorly correlated with eventual dominance. A more proximal lateral shoot on the underside of a leaning parent became the longest, dominant lateral in 24% of the parent shoots. The second study used stem girdles to test the hypothesis that the subjacent stem competes with the branch for branch-produced photosynthate. Results from Pinus strobus L. supported the hypothesis, but results from Betula lenta L. and Acer rubrum L. did not. The third study removed apical control from branches of six forest-shrub species by cutting off the stem above the branch. Branches of all species increased diameter growth after cutting the stem, but only branches of Ilex verticillata (L.) Gray, Hamamelis virginiana L., and Cornus amomum Mill. developed differential growth stress and bent upward. Treated branches of Gaylusaccia baccata (Wang.) K. Koch, Viburnum cassinoides L., and K. latifolia sagged as much as controls.Key words: apical control, diameter growth, branch angle, growth stress, reaction wood.
Interpreting pollen diagrams from wetlands: pollen representation in surface samples from Oil Well Bog, southern Ontario
Authors: Bunting M Jane , Warner Barry G , Morgan Clayton R
Published: April 2011

Pollen and spore analysis of surface sediment samples from 45 points within Oil Well Bog, a coniferous swamp near Cambridge, Ontario, was used to determine the possibility of identifying different wetland vegetation communities from their palynological record, and to assess the effects of variable wetland vegetation on the pollen representation of surrounding upland communities. The data obtained were mapped for individual taxa to allow direct comparison of the spatial patterns of vegetation abundance and the associated palynological assemblages, and cluster analysis was used to identify palynologically similar assemblages. Some wetland communities, such as swamp dominated by black spruce, do have distinctive pollen signatures, but not all the vegetational diversity observed is reflected in the palynological data, with similar pollen assemblages deriving from some communities which are vegetationally very different (e.g., shrub swamps dominated by Chamaedaphne calyculata and Ilex verticillata). The wetland pollen assemblages do reflect much of the floristic diversity of the surrounding uplands, although the different communities receive varying proportions of their pollen influx from upland sources (varying from less than 5% to over 90%), and wide variations in the percentage of a given upland pollen morphotype can be found within quite a short distance, depending on the nature of local wetland communities.Key words: palynology, swamp, surface samples, wetland.
Phenology and growth of shoots, needles, and buds of Douglas-fir seedlings with elevated CO2 and (or) temperature
Authors: Olszyk D , Wise Claudia , VanEss Erica , Apple Martha , Tingey David
Published: April 2011

Increased atmospheric CO2 and global warming may affect overall tree growth, but impacts of these combined stresses are largely unknown in terms of multiple growing season impacts on specific flushes. Thus, the effects of ambient or elevated CO2 (approximately 200 µmol·mol-1 above ambient) and ambient or elevated temperature (approximately 4°C above ambient) were evaluated for both main and second (lammas) flushes of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Established seedlings were grown for three full growing seasons in outdoor, sunlit chambers, which maintained diel and seasonal variation in climate. A reconstructed forest soil was used with a seasonal wet and dry cycle and without added fertilizer. Compared with ambient CO2, elevated CO2 had no impact on overall phenology and growth of terminal shoots, needles, or buds. In contrast, compared with ambient temperature, elevated temperature resulted in higher shoot and needle growth rates early in the season; reduced final terminal shoot length; and either reduced, increased, or unchanged final needle length, depending on season. Initiation of the lammas flush was delayed and (or) decreased at elevated temperature. Leading terminal bud break and growth occurred earlier; however, resting bud length was reduced, and bud width tended to increase with elevated temperature. Thus, at least during early seedling growth, elevated temperatures may reduce both main- and lammas-flush growth, thereby altering tree productivity, whereas elevated CO2 may have little effect on main or lammas growth at either the current or elevated temperature.Key words: climate change, leaf nitrogen, Pseudotsuga menziesii, shoot growth, lammas growth.
Delineation of the three brown rot fungi of fruit crops (Monilinia spp.) on the basis of quantitative characteristics
Authors: van Leeuwen GCM , van Kesteren H A
Published: April 2011

The three Monilinia spp., known as the brown rot fungi of fruit crops, are usually distinguished from each other on the basis of (qualitative) colony characteristics. We linked these qualitative features to unambiguously defined, quantitative colony and germ tube characteristics. A wide collection of isolates of Monilinia fructicola (Winter) Honey, Monilinia laxa (Aderhold & Ruhland) Honey, and Monilinia fructigena (Aderhold & Ruhland) Honey was used to determine growth rate and sporulation intensity on potato dextrose agar (PDA) at 22°C under two light regimes (darkness, 12 h light : 12 h dark). The following germ tube characteristics were determined on water agar after incubation for 18 h at 22°C in darkness: length of the (leading) germ tube, distance to the first branch, and the number of germ tubes per conidium. Increase in colony diameter from day 3 to day 5 and sporulation intensity measured after 14 days was the highest in M. fructicola, whilst M. laxa and M. fructigena showed considerable overlap in these features. The length of the germ tube after 18 h incubation was shortest in M. laxa, ranging from 161 to 466 µm. In M. fructicola and M. fructigena these ranges were 465-851 and 307-806 µm, respectively. The occurrence of more than one germ tube per conidium was most prominent in M. fructigena. Discriminant analysis on the basis of different combinations of the quantitative characteristics measured, showed that the combination of growth rate on PDA and length of the germ tube was sufficient to delineate the three brown rot fungi. One of 11 M. fructicola isolates was misclassified, the same held for M. fructigena (one misclassification of nine isolates). No misclassifications occurred in M. laxa.Key words: brown rot fungi, growth characteristics, Monilinia spp., taxonomy.
Molecular and conventional detection and identification of Cladosporium tenuissimum on two-needle pine rust aeciospores
Authors: Moricca S , Ragazzi A , Mitchelson K R
Published: April 2011

An integrated approach, based on the analysis of both molecular and morphological characters, has led to the unambiguous detection and identification of the rust hyperparasite Cladosporium tenuissimum from aeciospores of the two-needle pine rust fungi Cronartium flaccidum and Peridermium pini. Cladosporium tenuissimum was first detected from contaminated field-collected rust spores using the polymerase chain reaction (PCR) method. The similar-sized amplified DNA of the parasite was then separated from rust DNA using electrophoretic migration, reamplified separately with the nested PCR, and sequenced. Sequence comparison in the data banks enabled the hyperparasite to be recognised as a species of Cladosporium. Molecular detection was followed by conventional identification, obtained by plating rust spores on potato dextrose agar, a selective medium for rusts, since they are unable to grow on such a common substrate, and isolating the hyperparasite in pure culture. It was subsequently identified as C. tenuissimum. Traditional identification would not have been possible without guidance from the molecular data, which focused attention on the mycoparasite. Macro- and micro-scopic features of colonies are also given to help with future identification on spore sources from other geographical areas and, if this should occur, future identification on other rusts.Key words: mycoparasitism, PCR detection, traditional detection, Cladosporium tenuissimum, Cronartium flaccidum, Peridermium pini.
Ectomycorrhizal fungi associated with Arctostaphylos contribute to Pseudotsuga menziesii establishment
Authors: Horton Thomas R , Bruns Thomas D , Parker V Thomas
Published: April 2011

Chaparral on the central coast of California can occur as relatively stable patches of ectomycorrhizal Arctostaphylos directly adjacent to arbuscular mycorrhizal Adenostoma. Vegetation surveys and seedling survival assays show that Pseudotsuga establishes only in Arctostaphylos. We found no significant differences between Arctostaphylos and Adenostoma in allelopathy; light; temperature; or soil NH4+, NO3-, or K. Arctostaphylos soils tended to be higher in phosphate and were lower in pH, Ca, Mg, Ni, and Cr than those from Adenostoma. After 1 year of growth of Pseudotsuga seedlings in an Arctostaphylos patch, 17 species of fungi colonized both Pseudotsuga and Arctostaphylos. Fifty-six of 66 seedlings were colonized by fungi that also colonized Arctostaphylos within the same soil core. Forty-nine percent of the Pseudotsuga ectomycorrhizal biomass was colonized by fungi that were also associated with Arctostaphylos within the same core. Another 12% was colonized by fungi known to associate with Arctostaphylos from different cores. After 4 months of growth, Pseudotsuga seedlings in four of five Arctostaphylos plots were ectomycorrhizal and colonized by fungi in Russulaceae, Thelephoraceae, and Amanitaceae. Pseudotsuga seedlings in two of five Adenostoma plots were ectomycorrhizal but colonized by only two species of fungi in Thelephoraceae. These results provide compelling evidence that ectomycorrhizal fungi associated with Arctostaphylos contribute to Pseudotsuga seedling establishment.Key words: arbutoid, Douglas-fir, ectomycorrhizae, manzanita, RFLP, PCR.
The relationship of reproductive biology to the rarity of endemicAster curtus(Asteraceae)
Authors: Giblin David E , Hamilton Clement W
Published: April 2011

The fecundity of rare plants is a commonly used indicator of performance at the population or species level. However, accurately interpreting reproductive output requires an understanding of a particular species's breeding system. The purpose of this study was to determine if reproductive biology contributes to the restricted distribution of Aster curtus Cronq. We hypothesized that (i) A. curtus, like many Asteraceae species, is self-incompatible, and (ii) that pollinations between patches produce significantly more filled seeds than pollinations within patches. Fluorescent microscopy of pistils harvested after greenhouse pollination showed A. curtus to be partially self-compatible. Cross-pollination resulted in significantly more pollen grains per stigma and significantly greater pollen germination than self-pollination. Similarly, field pollination trials showed that between-patch crosses produced significantly more filled seeds than within-patch crosses. Nevertheless, within-patch pollinations produced substantial levels of filled seed. Results from the greenhouse and field trials suggest that the reproductive biology of A. curtus contributes little to its rarity. Understanding why A. curtus is rare has important implications to the conservation of the glacial outwash prairie. Moreover, the data from this research can be used in further developing predictive models for plant species rarity based on reproductive biology.Key words: Aster, endemic, Pacific Northwest, rarity, reproductive biology, self-incompatibility.
Tracing root development using the soft X-ray radiographic method, as applied to young cuttings of western red cedar (Thuja plicata)
Authors: Bidel LPR , Mannino M R , Rivière LM , Pagès L
Published: April 2011

To the best of our knowledge, this is the first soft X-ray radiographic study of the development of an entire young root system of western red cedar (Thuja plicata D. Don). The experimental device was adapted to radiographic constraints and allowed the plant to grow for several months. Successive radiographs revealed primary growth and differentiation, secondary growth, and primordium development. The younger (8-day-old) part of the root system appeared fully opaque. Afterwards, the stele and the cortex could be distinguished from each other progressively in a second zone where most of the primary differentiation had already occurred. Measuring early cambial growth was made possible by spacing the radiographs at 10-day intervals. Time-course developments of primordia and their histolysis cavities were traced for 8-15 days, depending on the sample. The acropetal sequences of primordia along the same adventitious root were shown. Primordia had different growth curves, most of which were nearly logistic. These meristems were produced by unequal primordia, which generated axes of unequal diameters. Our techniques provide new opportunities for understanding the differentiation of axes and defining potential root growth during primordium development.Key words: soft X-ray radiography, root development, primordia, root differentiation, radial growth, morphogenesis.
Black spruce (Picea marianna) architecture
Authors: Bégin Christian , Filion Louise
Published: April 2011

Genetically determined rules underlying black spruce (Picea mariana (Mill.) BSP) morphological development were revealed by using tree architecture analysis. Black spruce develops according to Rauh's model. Its relatively simple and well-hierarchized architecture comprises four categories of axes (A1-A4) and three distinct branching levels. First- and second-order axes (the trunk and branches) are monopodial, orthotropic structures with rhythmic growth and branching, and an unlimited life-span (or only limited by tree longevity). They are mainly devoted to spatial exploration and occupation. Axes A3 and A4 are monopodial, plagiotropic structures with a limited life-span, which are devoted to assimilation and reproduction. Female cones develop in terminal position on A3, whereas male reproductive structures develop in terminal or lateral position on A4. Reiteration (or duplication of axes) capacity is an important feature of the architecture of black spruce. Adaptive reiteration processes allow trees to renew their foliage and to reproduce vegetatively through layering. Traumatic reiteration processes tend to restore the tree's original architecture by replacing injured axes or parts of axes. In both cases, replicas originate from dormant buds located at the bottom of growth units (deferred or proleptic reiteration) or from growing axes (immediate or sylleptic reiteration).Key words: black spruce, growth form, tree architecture, architectural model, reiteration processes.
Effects of photoperiod and drought on the induction of crassulacean acid metabolism and the reproduction of plants of Talinum triangulare
Authors: Herrera A
Published: April 2011

To examine the effects of day length on the induction of crassulacean acid metabolism (CAM) by drought in the tropical species, Talinum triangulare (Jacq.) Willd. (Portulacaceae), plants were subjected to drought under different photoperiods. Nocturnal acid accumulation was 52 µmol H+··g-1 fresh mass (FM) in plants grown under a 10 h light : 14 h dark photoperiod and 76 µmol H+·g-1 FM in plants grown under 13 h light : 11 h dark, whereas it was only 10 µmol H+·g-1 FM in plants grown under 18 h light : 6 h dark. Plants were subjected to drought under short days and under short days with a night interruption of 1.5 h white light, aiming to simulate a long day, while minimally affecting daily carbon balance. Only droughted plants under normal short days accumulated acids during the night. Absence of CAM could not be attributed to differences due to photoperiod in either biomass allocation, chlorophyll content, or leaf water content. Photoperiod did not significantly affect fecundity in watered plants, whereas drought markedly reduced fecundity in plants with night interruption relative to plants under normal short days. Reproductive effort, calculated as seeds per gram leaf, was significantly higher in droughted plants under normal short days and watered plants with and without night interruption than in droughted plants with night interruption.Key words: CAM, crassulacean acid metabolism, drought, fecundity, induction, photoperiod, reproductive effort, reproduction, Talinum triangulare
Morphological analysis of genetically identified cattails Typha latifolia, Typha angustifolia, and Typha ×glauca
Authors: Kuehn Monica Marcinko , White Bradley N
Published: April 2011

Hybridization between the cattail species Typha latifolia L. and Typha angustifolia L. is frequent throughout northeastern and central North America. While studies are required to elucidate the ecological role of interspecific hybrids, morphological intergradation of the hybrids and parental species limits accurate identification. Although species-specific molecular markers have been developed, some researchers do not have the resources necessary for molecular analysis. Consequently, this study used genetically identified specimens of T. latifolia,T. angustifolia, and their hybrid Typha ×glauca Godr. to discriminate sound taxonomic characters for morphological identification. Leaf width, spike gap, spike width, and spike length were measured for 153 specimens of cattails from Massachusetts, Ontario, Quebec, and Manitoba. In addition, stigma width was measured using a compound microscope. Morphological data were used in discriminant analysis; approximately 90% of the classifications derived by discriminant analysis corresponded to the genetic identity. Discriminant analysis using stigma width, spike length, spike interval and leaf width provided accurate identification for 28 of 31 T. angustifolia specimens, 38 of 41 T. ×glauca specimens, and 20 of 25 T. latifolia specimens. Thus, discriminant analysis of morphological characters can be used to distinguish the hybrid cattail from the parental species with reasonable confidence when molecular resources are not available.Key words: Typha, cattails, discriminant analysis, DNA markers.
Initial events in the colonization of dyer's woad by Puccinia thlaspeos
Authors: Kropp Bradley R , Hooper Gary R , Hansen Dane R , Binns Mike , Thomson Sherman V
Published: April 2011

The initial events involved in basidiospore germination and infection of dyer's woad by Puccinia thlaspeos were studied using scanning electron microscopy and the polymerase chain reaction. The presence of dew was shown to promote infection but was not necessary. Under the conditions of this study, infection of leaf tissue could sometimes be detected using the polymerase chain reaction as quickly as 3 h after inoculation, but 6 h was usually required. Basidiospores and germ tubes were both attached to the leaf surface by an extracellular matrix, and the germ tubes produced appressoria before penetration into the leaf tissue. Penetration was direct rather than through the stomates, and colonization occurred via the growth of intercellular hyphae and haustoria.Key words: biological control, mycoherbicide, noxious weed, Puccinia, dyer's woad.
Siderophore formation in iron-limited cultures ofFrankiasp. strain 52065 andFrankiasp. strain CeSI5
Authors: Boyer Gregory L , Kane Stacie A , Alexander Jeffrey A , Aronson Dallas B
Published: April 2011

Frankia sp. strain 52065 (DDB 03010210) produces a high-affinity iron chelator or siderophore termed frankobactin to obtain iron needed for nitrogen fixation under iron-limiting conditions. Cultures of Frankia sp. strain 52065 and Frankia sp. strain CeSI5 (UFG 026605) were grown under iron-limiting and iron-replete conditions and examined for siderophore formation throughout the growth cycle using the HPLC55Fe-binding assay and the Csaky chemical assay. Both cultures produced frankobactin under iron-limiting, but not iron-replete, conditions. This is the first positive report of hydroxamate siderophore formation in a Frankia isolate other than Frankia sp. strain 52065. A detailed analysis of siderophore formation throughout the culture cycle shows the presence of a second, strong iron-binding compound in both Frankia sp. strain 52065 and Frankia strain CeSI5. Chemical characterization by mass spectroscopy indicates that this second siderophore, named frankobactin A, is likely to be the open oxazoline ring conformer of frankobactin. Solution concentrations of frankobactin and frankobactin A increased during the rapid growth phase of Frankia in culture, reaching a maximum concentration of 20-25 µM, then decreased once the cultures entered stationary phase. Uptake studies using55Fe-labeled frankobactin indicated this siderophore forms part of an inducible, high-affinity iron-uptake mechanism.Key words: hydroxamate, siderophore, frankobactin, iron, limitation, uptake.
Codon indices as a predictor of gene functionality in aFrankiaoperon
Authors: McEwan Neil R , Gatherer Derek
Published: April 2011

The mutational response index and measurements of codon bias were determined in eight potential open reading frames in a Frankia operon that encodes genes for nitrogen fixation. The functionality of the different open reading frames is assessed in light of these results and compared with previously published results, as is the applicability of these techniques to the assessment of translational function of putative open reading frames.Key words: Frankia, codon usage, codon bias, open reading frames, mutation pressure.
Regulation of nodulation in Discaria trinervis (Rhamnaceae) - Frankia symbiosis
Authors: Valverde Claudio , Wall Luis Gabriel
Published: April 2011

Nodulation in Discaria trinervis (Hook. et Arn.) Reiche was mainly located around the position of the taproot tip at the moment of inoculation with Frankia. Nodule distribution, but not final level of nodulation, was affected by the inoculum dose and the culture age of Frankia. Taproot inoculation resulted in distal suppression of nodulation of the growing root as early as 3 days after inoculation, that is, before the first nodules could be detected. Systemic inhibition in split root systems was maximal, but not complete, for a delay of 20 days between inoculations on both sides. Reinoculation of 9.5-week-old nodulated D. trinervis plants did not cause further nodulation. Nevertheless, nodule excision, with or without new inoculation, allowed the plant to develop new nodules not only at the infectible region of the young developing root but also in the region of prior existing nodules, where we observed arrested nodules at an early developmental stage. We conclude that root nodulation in D. trinervis might be controlled by two different pathways that operate through inhibition of infection and nodule development. One pathway is activated immediately after the first stages of root cell division are induced because of root inoculation with Frankia. The inhibition becomes systemic and is widespread in the root system before host cell invasion is carried out at the infection sites. The second pathway requires the presence of mature and N2-fixing nodules.Key words: actinorhiza, autoregulation, Discaria trinervis, feedback inhibition, Frankia, intercellular infection.
Seed germination, seedling emergence, and seed bank ecology of sweet fern (Comptonia peregrina(L.) Coult.)
Authors: Dow Melissa A , Schwintzer Christa R
Published: April 2011

We examined seed-bank seeds of sweet fern (Comptonia peregrina (L.) Coult.), an actinorhizal nitrogen-fixing shrub, to determine their distribution in the soil and to identify the factors that stimulate them to germinate following removal of the vegetation. Seeds were extracted from the soil of adjacent field and forest sites currently lacking sweet fern in Orono, Maine. Both sites contained approximately 2000 seeds·m-2with the greatest concentration at a depth of 60-80 mm. The seeds were 4.0-5.5 mm long, enclosed by a pitted, woody pericarp, and 8% contained embryos. Many seedlings emerged in disturbed plots (vegetation removed and upper soil mixed) in May and June 1997, but none appeared after 24 July. Seeds collected in May and June germinated readily in a growth chamber (30-45% germination) whereas only 2-5% of July- and August-collected seeds germinated indicating induction of secondary dormancy. August-collected seeds showed strong germination after >=15 days of moist chilling at 4°C indicating relief of secondary dormancy by chilling. Temperature fluctuation with an amplitude of 10°C strongly stimulated germination. Presence of annual secondary dormancy cycles and stimulation by strong temperature fluctuation assures that seed-bank seeds germinate under conditions that allow the seedlings to become established.Key words: actinorhizal plants, Comptonia peregrina, germination ecophysiology, secondary dormancy, seed bank, seedling emergence.
Environmental and genetic effects on the early survival and growth of the invasive grass Phalaris arundinacea
Authors: Morrison Shannon L , Molofsky Jane
Published: April 2011

Both genetic and environmental factors can determine whether an invasive plant species will establish. To determine how these factors influence the establishment of the invasive grass Phalaris arundinacea L. (reed canary grass), we grew three genotypes in 10 artificial environments and asked how a genotype's growth and survivorship was affected by environmental conditions. We found that genotype strongly influenced survivorship, but there was no significant effect of environment on survivorship. However, environmental conditions did significantly affect growth. Individual plants produced more aboveground and belowground biomass when grown singly than they did when grown with competitors. The identity of neighboring competitors had no effect. Although genotype had no significant efffect, there was a significant genotype × environment interaction. Clone 1 produced more root biomass than either clone 2 or clone 3 when there was no or little competition, but in competitive neighborhoods, clone 3 allocated relatively more biomass to roots than to shoots. Under ideal conditions in the greenhouse, clone 2 produced more tillers than the other two clones. Based on these results, it appears that clone 1 may have an advantage under sparse vegetative cover, but clone 3 may have a competitive advantage in highly competitive neighborhoods because it could preferentially allocate more biomass to roots. The presence of three growth patterns from such a small, localized sample suggests that different growth strategies are probably common within populations of reed canary grass and may be important for allowing reed canary grass to successfully invade new habitats.
The effect of refuge trees on a paper birch ectomycorrhiza community
Authors: Kranabetter J M
Published: April 2011

Live trees within forest disturbances could support refugia populations of ectomycorrhizae fungi from which to reestablish ectomycorrhiza communities during forest succession. The effectiveness of refuge paper birch trees (Betula papyrifera Marsh.) in maintaining a forest ectomycorrhiza community on birch seedlings, both in clearcuts and forests, in northwest British Columbia was examined. Seedlings next to refuge birch trees in clearcuts had equal levels of average morphotype richness and eveness as seedlings next to mature birch trees in forests. Seedlings outside of the rooting zone of refuge trees had significantly less average morphotype richness in both clearcuts and forests, decreasing by 38 and 15%, respectively. The ectomycorrhiza communities were also more unique (lower community similarity) next to refuge trees than for seedlings away from refuge trees, especially in clearcuts. These treatment effects could be explained by differences in the ability to disperse and establish between early-stage, multi-stage, and late-stage ectomycorrhiza fungi. The results suggest refuge trees would be effective in forest management as sources of inocula for multi-stage and late-stage fungi.
The Early Devonian (Pragian) zosterophyll Bathurstia denticulata Hueber
Authors: Kotyk Michele E , Basinger James F
Published: April 2011

Approximately 86 specimens of Bathurstia denticulata Hueber were collected from upper Bathurst Island and lower Stuart Bay beds of Bathurst Island, Canadian Arctic Archipelago. Bathurstia was a component of a zosterophyll-dominated flora of Pragian age (Lower Devonian) that existed at low paleolatitudes in northern Canada. The large collection of well-preserved materials permits reconstruction of the plant as a robust scrambler of about 30 cm in height. Stems bear short, shelf-like emergences in two rows, and branch isotomously, although sparsely. Rooting organs, representing some of the oldest known for land plants, arise from the main aerial axes, although they are also associated with small, subordinate shoots interpreted as plantlets. Numerous specimens are fertile, with sporangia borne in dense terminal spikes. Spikes include two rows of overlapping, discoid sporangia. Isospores are round and featureless, and assignable to the genus Calamospora. While Bathurstia apparently originated from among the isotomously branching bilaterally symmetrical zosterophylls, the phylogenetic relationships of Bathurstia to known taxa is unclear, although some resemblance to Serrulacaulis, Barinophytaceae, and the Gosslingiaceae can be documented. Bathurstia denticulata is now one of the best known of early land plants, and contributes significantly to our understanding of zosterophylls and their role in Early Devonian vegetation.Key words: Bathurstia, zosterophyll, Devonian, Canada, Arctic, evolution.
Peatland fragments of southern Quebec: recent evolution of their vegetation structure
Authors: Pellerin Stéphanie , Lavoie Claude
Published: April 2011

One of the main problems associated with small natural reserves is their progressive loss of ecological integrity owing to the influence of surrounding human activities. In southern Quebec (Bas-Saint-Laurent, Canada), peatlands are extensively mined to extract peat for the production of horticultural compost and are isolated within agricultural lands. Government environmental agencies have proposed that peat industries set aside 5-10% of a bog's area as a natural refuge for peatland plants and animals. Do these fragments constitute reliable refuges? Do they maintain their ecological characteristics over a long period? We studied the recent evolution of plant communities in peatland fragments using paleoecological techniques and a geographical information system. In the study area, some treeless fragments dominated by Sphagnum species have recently (since 1940) converted to forest sites. Macrofossil and dendrochronological analyses suggest that peat-mining activities were not the main factors responsible for the afforestation of peatland fragments. On the other hand, the isolation of the Bas-Saint-Laurent peatlands within an agricultural plain for more than 100 years may explain the afforestation process (drainage activities). Furthermore, fires may have accelerated afforestation by facilitating the spread of seeds of tree species with serotinous cones. Because most peatlands of the Bas-Saint-Laurent region are still affected by drainage and fires, it is probable that several open bog fragments will not maintain their treeless vegetation structure over a long period. Consequently, peatland fragments should not be considered as a solution to long-term conservation needs in southern Quebec, at least not for plant and animal species of open bogs. This study also shows that even ecosystems known to be resistant to invasions by exotic species (such as peatlands) can be strongly affected by fragmentation and by their surrounding environment on a long-term basis.Key words: peatland, peat mining, fire, fragmentation, conservation, Quebec.
Docking of the Central Metasedimentary Belt to Laurentia in geon 12: evidence from the 1.17-1.16 Ga Chevreuil intrusive suite and host gneisses, Quebec
Authors: Corriveau Louise , Breemen Otto van
Published: April 2011

The Chevreuil intrusive suite (1.17-1.16 Ga) represents a chronological field marker of regional extent that intruded the Central Metasedimentary Belt in the western Grenville Province of Quebec after peak metamorphism. Style and site of magma emplacement, and extent of deformation of Chevreuil plutons and dykes permit unravelling of the early Grenvillian evolution of the belt with respect to cratonal North America. The suite comprises a series of vertically layered gabbro stocks and monzonite-diorite-gabbro sheet intrusions, and a swarm of microdiorite dykes that cut across gneisses. The dykes display systematic variations in extent of deformation across the belt. We targeted U-Pb geochronology on gneisses within the identified strain windows; they preserve the record of a ca. 1.20 Ga high pressure-temperature (P-T) metamorphic event. The sheet intrusions define magmatic corridors all along, and concordant with, the western, northern, and eastern tectonic boundaries of the belt. The concordant and elongate shape of these bodies results from emplacement, not deformation. Chevreuil magmas thus sealed the belt boundaries largely in their current positions, with the implication that docking of Elzevirian and pre-Elzevirian terranes with cratonal North America predates 1.17 Ga. We interpret the 1.20 Ga metamorphism as evidence for the initiation of Grenvillian continent-continent collision during the culmination of the Elzevirian orogeny at ca. 1.22 Ga. Emplacement-related fabrics indicate that the Chevreuil suite and the coeval Morin anorthosite suite intruded during renewed orogenesis. This orogenic pulse (Shawinigan) is not accretionary, but represents a strongly partitioned, compressive, intraplate reactivation event.
Neoproterozoic slope deposits, Mackenzie Mountains, northwestern Canada: implications for passive-margin development and Ediacaran faunal ecology
Authors: MacNaughton Robert B , Narbonne Guy M , Dalrymple Robert W
Published: April 2011

The youngest formations of the Neoproterozoic Windermere Supergroup in northwestern Canada (Gametrail, Blueflower, and Risky formations) record the transition from slope to shelf deposition on a prograding passive margin. Eleven facies associations are recognized, representing environments ranging from carbonate- and siliciclastic-dominated continental slope to open carbonate shelf and siliciclastic shoreface. Seven simple sequences are recognized, which can be grouped into three composite sequences. Combination of the data presented here with previous work on underlying and overlying formations indicates that the sequence-stratigraphic record is least detailed in the deepest-water facies and most detailed in shelf facies, reflecting the relative inability of high-frequency relative sea-level oscillations to affect deposition in deep-water settings. Falling-stage deposits are especially common in the upper slope region. Several major sequence boundaries (unconformities) are clustered in the interval a short distance below the Precambrian-Cambrian boundary. The most significant of these occurs high in the Blueflower Formation, not at the top of the Risky Formation as commonly inferred. This interval containing several surfaces may reflect thermal uplift related to the rifting recorded in rocks of this age in the southern Canadian Cordillera. Renewed subsidence (thermal relaxation) commenced just prior to the Neoproterozoic-Cambrian boundary, giving rise to a thick succession of shelf to nonmarine basal-Cambrian deposits. Ediacaran body fossils previously reported from the studied units occur in a range of slope to shoreface environments, including some facies that were deposited below the photic zone. The most common taxa occur across a spectrum of facies and were apparently ecological generalists.
Cryostratigraphy of the Klondike "muck" deposits, west-central Yukon Territory
Authors: Kotler E , Burn C R
Published: April 2011

Four late Quaternary cryostratigraphic units are recognized in the unconsolidated valley-bottom deposits of the Klondike area, Yukon Territory. Three of the units, in ice-rich, loessal sediments of pre-Wisconsinan or Wisconsinan age, collectively compose the King Solomon Formation. They are overlain by a Holocene organic unit. The units are distinguished by their cryostratigraphic characteristics and oxygen-isotope ratios of included ground ice. The basal unit is the Last Chance Creek Member, a pre-Late Wisconsinan deposit, containing preserved ice wedges δ18O ~ -28 to -26; δD ~ -225 to -209). The overlying Quartz Creek Member, a Late Wisconsinan unit, is dominated by organic-rich loess. Massive ice is noticeably absent, although the sediments are ice rich. The isotopic composition of ice in this unit is characteristic of full-glacial conditions (δ18O ~ -32 to -29; δD ~ -234 to -257). An abrupt change to warmer and wetter conditions at the end of glaciation, prior to the Holocene, is recorded by the ice-rich, colluviated Dago Hill Member (δ18O ~ -28 to -21; δD ~ -164 to -225), which began accumulating by 11.62 14C ka BP. Large ice wedges originate in this unit, and, in places, penetrate the underlying full-glacial sediments. Even higher δ18O and δD values occur for ice in the Holocene organic unit (δ18O ~ -25 to -20; δD ~ -164 to -189). The majority of the massive icy bodies in the King Solomon Formation are ice wedges, but pool ice and aggradational ice are also exposed, especially in the Dago Hill Member. Massive icy beds formed by groundwater intrusion into permafrost occur at the lower contact of the Quartz Creek Member.