bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative evaluation of pollen polymorphism in a tristylous weed,Lythrum salicaria(Lythraceae)
Authors: Mal Tarun K , Hermann Brian P
Published: April 2011

Tristylous breeding system consists of three different forms of flowers that differ reciprocally in the heights of stigmas and anthers within flowers. Apart from the style and stamen lengths, heterostylous species also demonstrate pollen and stigma polymorphisms. Tristylous Lythrum salicaria L. bears trimorphic, striate, tricolporate pollen with three true colpi and three pseudocolpi. Using a scanning electron microscope, we quantified pollen polymorphism in L. salicaria by measuring the length and diameter of pollen, and the length of colpi and pseudocolpi. Pollen grains from the long stamens are significantly larger than those from the mid stamens, followed by those from the short stamens. Despite significant differences in pollen size among long, mid, and short stamens, pollen morphometric traits demonstrate overlap among morphs. Pollen diameter also differed significantly between source populations. A discriminant function analysis separated long-level pollen from mid- and short-level pollen based on the canonical scores of measurements of pollen structure. The polymorphism of pollen in conjunction with that of the stigma may play a functional role in self-incompatibility mechanisms.Key words: Lythrum salicaria, purple loosestrife, Lythraceae, heterostyly, incompatibility, pollen polymorphism.
Involvement of a novel peroxidase isozyme and lignification in hydathodes in resistance to black rot disease in cabbage
Authors: Gay P A , Tuzun S
Published: April 2011

The physiological mechanisms associated with resistance of cabbage to black rot disease seem to be associated with the hydathodes. To investigate the role of hydathodes in disease resistance, total peroxidase activities, anionic peroxidase isozyme expression, and lignin deposition were determined in hydathodes of resistant (Hancock and Green Cup), partially resistant (Cheers), and susceptible (Strukton and Perfect Ball) cabbage varieties (Brassica oleracea L.) during pathogenesis with Xanthomonas campestris pv. campestris. Four-week-old plants were petiole-inoculated with a highly virulent strain of X. campestris pv. campestris (FD91L). Hydathodal fluids were collected daily over a 14-day period from infected plants as well as noninfected, mock-inoculated control plants. Hydathodal fluids of resistant varieties had greater peroxidase activity when compared to susceptible ones, with infected plants having higher peroxidase levels than noninfected plants. Isoelectric focusing revealed the presence of four anionic peroxidase isozymes in hydathodal fluids, with the most anionic one (pI of 3.6) accumulating only upon infection. Lignin deposition in and around the hydathodes was associated with the accumulation of this particular isozyme in hydathodal fluids. The evidence suggests that a rapid, systemic response is associated with resistance to the bacterial pathogen.Key words: peroxidases, hydathodes, isozymes, black rot disease, cabbage, Xanthomonas campestris pv. campestris.
Comparison of pollen and conifer stomates as indicators of alpine treeline in northwestern Canadian lake sediments
Authors: Pisaric Michael FJ , Szeicz Julian M , Karst Tammy , Smol John P
Published: April 2011

We compare fossil pollen and stomate assemblages in 29 lake sediment surface samples from mountainous regions in northwestern Canada to characterize the relationship between modern vegetation, and pollen and stomate deposition. Modern pollen spectra were dominated by arboreal taxa originating from lower elevation sites. Pinus pollen frequently reached 30% of the pollen sum, regardless of elevation. Alpine-tundra vegetation has lower pollen abundance, even in the alpine-tundra zone, where it dominates the sparse vegetation cover. Fossil stomates were observed in all but one site where trees currently exist in the vicinity of the lake, while no stomates were found in the sediments from alpine-tundra sites. The highest concentration of stomates occurred in lake sediments from closed-canopy forested areas. Our data suggest that different boreal forest types may be differentiated based on pollen assemblages and that the presence of stomates clearly distinguishes vegetation zones dominated by arboreal vegetation from alpine-tundra zones where trees are not present.Key words: pollen, conifer stomates, treeline, Pacific Northwest.
Effects of pH on cell morphology and carbonic anhydrase activity and localization in bloom-formingMougeotia(Chlorophyta, Charophyceae)
Authors: Arancibia-Avila Patricia , Coleman John R , Russin William A , Wilcox Lee W , Graham James M , Graham Linda E
Published: April 2011

A species of Mougeotia (C.A. Agardh) that was the dominant component of a metaphytic bloom-forming filamentous algal assemblage in an experimentally acidified lake (Little Rock Lake, Vilas County, Wisconsin, U.S.A.) was isolated into unialgal culture for analysis of pH effects on cell morphology and carbonic anhydrase activity and localization. External and total carbonic anhydrase activities at pH 8 were significantly greater than those at pH 5, but internal carbonic anhydrase activities were not significantly different at the two pH levels, as determined by use of a potentiometric technique. Ultrastructural immunogold labeling with a polyclonal antibody to Chlamydomonas periplasmic carbonic anhydrase suggested that an antigenically similar protein was located in the periplasmic space, inflated end walls, chloroplast, and peripheral cytoplasm of Mougeotia grown at both pH 8 and 5. Activity measurements and localization data were consistent with the hypothesis that a carbon concentration mechanism operates in this Mougeotia species at both high and low pH. Growth form, cell dimensions, chloroplast morphology, and cell wall ultrastructure were significantly different in cultures grown at pH 5 and pH 8. These structural and carbon acquisition features may contribute to Mougeotia's ability to form conspicuous metaphytic blooms in acidified waters.Key words: carbonic anhydrase, acidification, algal blooms, Mougeotia.
Changes in sterol composition with ontogeny of Blumeria graminis conidia
Authors: Muchembled Jérôme , Sahraoui Anissa Lounès-Hadj , Grandmougin-Ferjani Anne , Sancholle Michel
Published: April 2011

The total sterol composition of conidia of the obligate plant pathogen Blumeria (= Erysiphe) graminis f.sp. tritici has been analysed as a function of their ontogeny during sporulation. Two main classes of sterols were characterized: 24-ethylsterols (24-ethylcholesta-5,22-dienol, 24-ethylcholesterol, and Δ5-avenasterol) and 24-methylsterols (24-methylenecholesterol and episterol). Our results show that sterol composition is greatly modified during ontogeny of B. graminis conidia both at the qualitative and quantitative levels. In particular, 24-methylsterols, e.g., 24-methylenecholesterol and episterol, are the major sterols in old conidia whereas 24-ethylsterols, e.g., 24-ethylcholesta-5,22-dienol, 24-ethylcholesterol, and Δ5-avenasterol, are the main sterols in young conidia.Key words: Erysiphe, wheat powdery mildew, sterols, ontogeny.
The effect of gopher mounds and fire on the spatial distribution and demography of a short-lived legume in tallgrass prairie
Authors: Wolfe-Bellin Kelly S , Moloney Kirk A
Published: April 2011

Many studies have reported that gopher mounds can increase species diversity and spatial heterogeneity of plant communities, but few studies have experimentally linked these small-scale disturbances to spatial heterogeneity in the distribution of individual plant populations. In this study, we directly tested for a spatial relationship between the pattern of gopher mound production and the distribution of a short-lived legume, Medicago lupulina L., across a tallgrass prairie remnant. In addition, we conducted a 3-year study examining the demographic response of M. lupulina to mound and off-mound planting treatments, during which a spring fire occurred one year. We found that the spatial distribution of M. lupulina was positively correlated with the distribution of mounds. Germination was significantly greater off mounds in all years, while survivorship and fecundity were significantly greater on mounds in the 2 years without fire. During the fire year, survivorship was significantly greater off mounds and fecundity was approximately equal on and off mounds. We conclude that the positive spatial relationship between M. lupulina and mounds is caused by the direct dependence of M. lupulina on mounds for survivorship in most years. Gopher mounds provide microsites where plant competition and risk of herbivory are reduced. Overall, gopher mounds can directly produce spatial heterogeneity in the plant community, but the strength of this effect may be significantly modified in some years, particularly those in which a spring fire occurs.Key words: gopher mounds, fire, Medicago lupulina, disturbance, prairie, introduced species.
Sequences of psychrophilic fungi amplified from glacier-preserved ascolichens
Authors: DePriest Paula T , Ivanova Natalia V , Fahselt Dianne , Alstrup Vagn , Gargas Andrea
Published: April 2011

Ribosomal DNA sequences were amplified from subfossils of the ascolichen Umbilicaria cylindrica (L.) Delise ex Duby collected at the ablating edges of Greenland glaciers. Surprisingly, phylogenetic analysis indicated that the amplified rDNA sequences were not closely related to those of the lichen-forming fungus but rather represented two groups of psychrophilic basidiomycetes (orders Cystofilobasidiales and Sporidiales) and one group of ascomycetes (order Leotiales). Two of these groups, the Sporidiales and the Leotiales, include other fungi previously detected in DNA extracted from the grass clothing of the Tyrolean Iceman desiccated and frozen for over 3000 years and also in 2000- and 4000-year-old ice core samples from northern Greenland. Large subunit ribosomal DNA sequences representing the group Cystofilobasidiales were nearly identical to those of the basidioyeast saprobe Mrakia frigida. The adjacent internal transcribed spacer sequence was more than 98% similar to those from three samples of U. cylindrica from different sites that had been subjected to ice burial for various lengths of time, suggesting they also were Mrakia sequences. Although ancient contamination of multiple U. cylindrica specimens with fungi such as Mrakia cannot be ruled out, it is more probable that saprobic colonization of the subfossil tissues by psychrophilic fungi proceeded during recent ice melt.Key words: ancient DNA, small subunit ribosomal DNA, 18S ribosomal DNA, phylogenetic analysis, psychrophilic fungi, lichen-forming fungi.
Fungi in the winter diets of northern flying squirrels and red squirrels in the boreal mixedwood forest of northeastern Alberta
Authors: Currah R S , Smreciu E A , Lehesvirta T , Niemi M , Larsen K W
Published: April 2011

Gut contents of 138 northern flying squirrels (Glaucomys sabrinus) and 75 red squirrels (Tamiasciurus hudsonicus), which had been trapped from November to February in the boreal forest of northeastern Alberta, were examined to determine which fungi were consumed as food during the winter months in this habitat. Spores of epigeous Boletales, Russulaceae, and Cortinariaceae were most frequent and numerous. Hypogeous ascomycetes (unidentified species of Elaphomyces and Tuber) and basidiomycetes (unidentified species of Gautieria, Hymenogaster, Hysterangium, and Rhizopogon) were sometimes present in substantial amounts but were not as frequent as the remains of epigeous fungi. Guts sometimes contained remains of the tough or carbonaceous sporocarps of unidentified species of the Hymenochaetales, Diatrypaceae, Xylariaceae, and Bankeraceae. The spores of some rust fungi (e.g., Phragmidium fusiforme) along with the conidia (e.g., Helicoma sp.) and ascospores of microfungi (e.g., Sordariaceae) were also detected. Lichen tissues were absent, and this contrasts with previous suggestions that lichens are a winter food of sciurids in regions with substantial snowfall. A parallel analysis of 110 faecal pellets from northern flying squirrels collected in the same area from June to August confirms that fungi are important in its summer diet.Key words: Glaucomys sabrinus, Tamiasciurus hudsonicus, fungi, mycophagy, Sciuridae.
The 5S rDNA units in Kengyilia (Poaceae: Triticeae): diversity of the nontranscribed spacer and genomic relationships
Authors: Baum Bernard R , Bailey L Grant
Published: April 2011

The sequences of eighty 5S rDNA clones were obtained by polymerase chain reaction (PCR) amplification of DNA from 12 accessions representing eight species of Kengyilia. Orthologous sequences were grouped into five unit classes: long P1, long S1, long {Y1, short P1, and short S1. Both the long P1 and long S1 classes are prevalent in Kengyilia, whereas the rest are rare. The short S1 class has not been described previously in other Kengyilia species. Two clones represent the long {Y1 class, with only one clone reported previously in Kengyilia alatavica (Drobow) J.L. Yang, Yen & Baum and a single clone found in this investigation. The long H1 unit class reported earlier for Kengyilia rigidula (Keng and S.L. Chen) J.L. Yang, Yen & Baum, but not for K. alatavica, was not found in any of the eight species investigated. Therefore, its presence in K. rigidula may be the result of introgression from Elymus nutans Grisebach, an HS-genome species containing the long H1 unit class; the two are often found growing together and are known to yield sterile hybrids in those populations. The specific 5S DNA unit classes, except for the ones that were found in very low frequency and in few samples, may have a potential not only as markers for the identification of haplomes but also of hybrids containing a combination of genomes. This investigation indicated, along with previous studies, that the 5S unit classes either form integral parts of haplomes or remain conserved and identifiable within haplomes originating from distant species, indicating that concerted evolution in the 5S gene plays only a partial role as an evolutionary force.Key words: 5S DNA gene, molecular diversity, Kengyilia, Triticeae, concerted evolution.
Identity of Guignardia sp. inhabiting ericaceous plants
Authors: Okane I , Nakagiri A , Ito Tad
Published: April 2011

An ascomycete belonging to the genus Guignardia with a Phyllosticta anamorph was frequently isolated from living leaves of several ericaceous plants. Ecological study on assemblages of endophytes suggested that this fungus is a dominant endophytic fungus of ericaceous plants. The Phyllosticta anamorph was morphologically similar to Phyllosticta capitalensis P. Henn., which can be a pathogen of orchids. An authentic culture of P. capitalensis IFO 32914 (= CBS 226.77) produced an ascigerous stage on potato dextrose agar, the morphology of which was identical to the Guignardia sp. from ericaceous plants. Sequence data of the internal transcribed spacer regions of ribosomal DNA (ITS1 and ITS2, including 5.8S rDNA) supported the identity of the present fungus and P. capitalensis. Consequently, we describe this endophytic ascomycete found from ericaceous plants as Guignardia endophyllicola sp.nov., which has P. capitalensis as an anamorph. Previously known as a pathogen of orchids, the fungus was revealed to exist widely as an endophyte within ericaceous plants.Key words: endophytic fungus, Ericaceae, Guignardia endophyllicola, pathogenic fungus, Phyllosticta capitalensis, Orchidaceae.
Ultrastructure of the host-parasite interaction in leaves of Duchesnea indica infected by the rust fungus Frommeëla mexicana var. indicae as revealed by high pressure freezing
Authors: Mims C W , Rodriguez-Lother C , Richardson E A
Published: April 2011

A combination of scanning and transmission electron microscopy was used to examine the host-pathogen relationship in leaves of Duchesnea indica (Andrz) Focke infected by the rust fungus Frommeëla mexicana var. indicae McCain & Hennen. Samples for transmission electron microscopy were prepared using high pressure freezing followed by freeze substitution. This protocol provided excellent preservation of both host cells and fungal haustoria. Each haustorium of F. mexicana var. indicae possessed a long slender neck with a neck band and an expanded body that contained two nuclei positioned close together. The haustorial body was lobed and sometimes even branched but lacked septa. Details of the extrahaustorial membrane that separated each haustorium from the cytoplasm of its host cell were particularly well preserved. Extensive labyrinth cell wall ingrowths developed around haustorial necks, as well as elsewhere, in infected cells. These ingrowths appeared to be identical to those present in plant transfer cells. Transfer cells are thought to be involved in intensive solute transfer over short distances. This appears to be the first report of the development of transfer cells in response to infection by a plant pathogenic fungus.Key words: haustoria, transfer cells, freeze substitution, electron microscopy.
Dendroecology and climatic impacts for a relict, old-growth, bog forest in the Ridge and Valley Province of central Pennsylvania, U.S.A.
Authors: Abrams Marc D , Copenheaver Carolyn A , Black Bryan A , Gevel Saskia van de
Published: April 2011

We report on the 440-year dendrochronological history of a relict, bog forest in the Ridge and Valley Province of central Pennsylvania that contains extreme southern, disjunct populations of Picea mariana (Mill.) BSP and Abies balsamea (L.) Mill. The forest is dominated by Tsuga canadensis (L.) Carr. (49% relative importance value), Picea mariana (16%), and Acer rubrum L. (15%). The few remaining Abies balsamea trees are in a advanced state of decline. Many Nyssa sylvatica Marsh. and T. canadensis trees recruited from 1560 and 1700, respectively, until 1890. However, the majority of the other tree species recruited during a 40-year period following selective logging of the forest in the 1890s and fires in about 1900 and 1914. We found a scarcity of tree saplings and no evidence of recruitment into the tree-size class for any species after 1950. The master tree-ring chronology for both N. sylvatica and T. canadensis exhibits a marked increase after the 1890s logging and a decrease after a 1900 fire. In addition, a large number of releases in individual tree chronologies occurred over the last 400 years, indicating the frequent occurrence of small-scale disturbances. Tree-ring growth during the 20th century was reduced by droughts and cool temperatures in the 1920s and in the early to middle 1960s. Abies balsamea cores exhibit a marked growth decline in 1986. Tsuga canadensis growth was very low between 1970 and 1998, despite a generally warm and wet climate during that time. Picea mariana had a dramatic increase in growth during very warm and wet climate between 1995 and 1998. Most Abies balsamea trees have reached their pathological age of 50-85 years and have active Armillaria root rot, insect infestations, and very poorly developed crowns. These symptoms or severe growth declines are not present in Picea mariana. It appears that the 10 000 year history of Abies balsamea presence at Bear Meadows will end soon, with no opportunity to reestablish itself because of the lack of a local seed source. The results of this study suggest that relict tree populations in the eastern United States may be particularly sensitive to direct and indirect anthropogenic impacts and climatic variations, and represent important benchmarks for comparisons with future studies.Key words: tree rings, disturbance, climate, global change, central Pennsylvania.
Genetic and morphologic variation inPhyllodoceempetriformisandPhyllodoce glanduliflora(Ericaceae) in Mount Rainier National Park, Washington
Authors: Rochefort Regina M , Peterson David L
Published: April 2011

Genetic and morphological diversity of Phyllodoce empetriformis (Sw.) D. Don and Phyllodoce glanduliflora (hook.) Cov. were surveyed in Mount Rainier National Park in the Cascade Mountains of Washington State. Paired populations at high and low elevations were sampled at three study areas between 1720- and 2451-m elevation. Allozyme analysis of four polymorphic loci indicates high levels of genetic diversity within populations (P. empetriformis = 94.2% and P. glanduliflora = 93.4% of total diversity) and significant differences in allele frequencies among populations and study areas. Individual populations are composed of multiple clones with high ratios of local to widespread genotypes. The proportion of distinguishable clones ranges from 32 to 83% within individual populations. Within individual populations, 18-67% of genotypes were restricted to one population. Patterns of morphologic variation, estimated through measurements of leaf width, leaf length, stem extension, and plant height paralleled those displayed by allozyme analysis. Significant differences were found in leaf width and stem length for P. empetriformis and among greenhouse populations for leaf width (P. empetriformis) and leaf length (P. glanduliflora). Species conservation strategies for Phyllodoce should concentrate on the maintenance of within-population levels of diversity, protection of adjacent populations, and protection of safe sites for recruitment of new populations.Key words: conservation, Ericaceae, genetic diversity, morphologic variation, Phyllodoce.
Morphology and AFLP markers suggest three Hordeum chilense ecotypes that differ in avoidance to rust fungi
Authors: Patto M Carlota Vaz , Aardse Aernoudt , Buntjer Jaap , Rubiales Diego , Martín Antonio , Niks Rients E
Published: April 2011

In Hordeum chilense Roem. & Schult., a high variation in the level of avoidance to infection of barley leaf rust (Puccinia hordei Otth) occurs. Probably resulting from the properties of the stomata, the rust germ tube overgrows stomata, and the infection process fails in an early stage. In the present study we tested the hypothesis that the avoidance character occurs in certain morphologically and molecularly distinct ecotypes of H. chilense. Eighty-eight H. chilense accessions were inoculated with P. hordei to assess the level of avoidance. The accessions were described for 30 morphological characters and three AFLP primer combinations. Cluster analysis using both morphological and AFLP fingerprint data suggested three distinct clusters of accessions. One of the clusters had a particularly high level of avoidance. This putative subspecific taxon was characterized by shorter and wider spikes, more erect culms, a greater number of stomata per square centimetre on the abaxial leaf side, and a shorter uppermost internode until flag leaf. All accessions clustered in this subspecific taxon were collected from humid habitats. We conclude that H. chilense consists of at least three rather well defined, morphologically and genetically distinct subspecific taxa, one of which has a very high level of avoidance to barley leaf rust.Key words: AFLP fingerprinting, diversity, Hordeum chilense, avoidance, rust fungi, Puccinia hordei.
Differences in wetland plant community establishment with additions of nitrate-N and invasive species (Phalaris arundinacea and Typha ×glauca)
Authors: Green Emily K , Galatowitsch Susan M
Published: April 2011

Restored prairie pothole wetlands in North America are often enriched by nitrate-N (NO3-N) that has been lost from surrounding agricultural systems. In addition, these wetlands are increasingly colonized by invasive taxa including Phalaris arundinacea L. and Typha ×glauca Godr. To explore the impacts of NO3-N enrichment, suppression by invasive species, and the interaction of these factors on restored communities, we grew native sedge meadow communities from seed in greenhouse mesocosms and subjected them to NO3-N and invasive species for 4 months. Typha ×glauca did not reduce overall native community biomass and actually enhanced Aster spp. biomass. Phalaris arundinacea suppressed growth of the native community to an equal relative extent across all NO3-N levels. The shoot biomass of the entire native community in untreated plots was similar to the P. arundinacea fraction of the treated plots. Phalaris arundinacea demonstrated greater plasticity in root-shoot allocation than the native community over the range of NO3-N inputs. Proportional allocation to root biomass was greater for P. arundinacea than for the native community at all but the highest NO3-N level. Both factors may be important in explaining dominance of P. arundinacea over the native community in a range of fertility conditions. Regardless of NO3-N inputs, the restoration of diverse native wetlands requires strict control of P. arundinacea during community establishment, as evidenced by the relatively rapid rate of suppression of native community biomass by P. arundinacea compared with T. ×glauca.Key words: restoration, agricultural impacts, prairie pothole, root/shoot ratio.
Population differences in stable carbon isotope ratio of Pinus contorta Dougl. ex Loud.: relationship to environment, climate of origin, and growth potential
Authors: Guy Robert D , Holowachuk Diane L
Published: April 2011

Stable carbon isotope composition (δ13C) was used to examine genetic and environmental variation in water-use efficiency of 11 Pinus contorta Dougl. ex Loud. populations from western Canada. Sapwood cores from 20-year-old saplings established at three sites in British Columbia, and shoots of greenhouse-grown, first-year seedlings, were analyzed. δ13C values of whole sapwood and isolated cellulose were correlated at r = 0.990 (p << 0.0001, n = 10). There were genetic differences in δ13C among populations. A population from the wet Pacific coast (P. contorta var. contorta) stood out from the others, which were all from the drier continental interior (P. contorta var. latifolia Engelm). This population had the highest indicated water-use efficiency. δ13C values of most populations increased from the wettest to the driest site with no significant change in ranking. Mean yield (stem volume) of the P. contorta var. latifolia populations was positively correlated with δ13C. Population differences at the seedling stage were not as pronounced, but δ13C values of seedling shoots and sapling wood cores were correlated. Among the 10 P. contorta var. latifolia sapling populations, δ13C decreased with an index of summer dryness and, less so, with increased elevation. It appears, therefore, that the most water-use efficient and most productive populations originate from relatively moderate, low-elevation sites with reduced likelihood of water stress.Key words: water-use efficiency, isotope discrimination, lodgepole pine, phenotypic plasticity, provenance trials.
The taxonomic and phylogenetic utility of vegetative anatomy and fruit epidermal silica bodies in Carex section Phyllostachys (Cyperaceae)
Authors: Starr Julian R , Ford Bruce A
Published: April 2011

In Carex, vegetative anatomy and fruit epidermal silica bodies have been used to delimit species and sections, although frequent conflicts with traditional classifications have led many authors to question whether they can be used to infer evolutionary relationships. This conclusion, however, has largely been drawn from poorly circumscribed groups that have not been phylogenetically analyzed. This study was undertaken to assess the taxonomic and phylogenetic utility of these characters within Carex section Phyllostachys, a small (eight species), monophyletic group whose taxonomy and phylogeny has been extensively studied. Leaf and culm anatomy clearly separate the close species pair of Carex backii Boott and Carex saximontana Mackenzie, and they provide unique characters that distinguish Carex latebracteata Waterfall and Carex juniperorum Catling, Reznicek, & Crins. Anatomical and silica body characters strongly support the recognition of three species within the Carex willdenowii Willdenow complex (Carex willdenowii s.s., Carex basiantha Steudel, Carex superata Naczi, Reznicek, & B.A. Ford). Although unique characters were lacking in Carex jamesii Schw., infraspecific variation in its silica bodies was consistent with the high levels of genetic and morphological variation previously detected. Silica body characters support groups that are congruent with previous phylogenetic hypotheses derived from both morphological and molecular data. In contrast, vegetative anatomy, in this and previous studies, supports contradictory groups suggesting that its use in future phylogenetic studies below the sectional level in Carex may be limited.Key words: Carex, anatomy, silica bodies, cladistics, species circumscription.
Microtubules of the mycorrhizal fungus Glomus intraradices in symbiosis with tomato roots
Authors: Timonen S , Smith F A , Smith S E
Published: April 2011

In this study the presence and orientation of fungal microtubules were recorded in arbuscular mycorrhizal symbiosis for the first time. Visualization of the fungal microtubules was achieved by using a protocol specifically labelling only fungal tubulins. Microtubules of external mycelium, intraradical hyphae, arbuscules, and vesicles of the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith were examined when in symbiosis with tomato (Lycopersicon esculentum Mill.). Microtubules were organized as bundles in both external and intraradical hyphae. The bundles of microtubules extended directly from intraradical hyphae into the arbuscules, where the microtubules remained as bundles in the larger hyphae. In the fine fungal branches of the arbuscules, microtubules were seen as thinner filaments. Fungal microtubules were seen to connect the intraradical hyphae and arbuscules. In addition, microtubules of adjacent arbuscules could continue directly from one arbuscule to another. Microtubules reached to the basal cone of each vesicle, but the live vesicles, containing many nuclei, seemed devoid of any microtubular labelling.Key words: cytoskeleton, endomycorrhiza, filamentous fungi, tomato, tubulin, Zygomycota.
Clethra barbinervis, a member of the order Ericales, forms arbuscular mycorrhizae
Authors: Kubota M , McGonigle T P , Hyakumachi M
Published: April 2011

The mycorrhizal status of Clethra barbinervis, in the family Clethraceae of the order Ericales, was investigated. Mycorrhizal colonization of C. barbinervis roots collected from naturally occurring trees in two forests in Japan was determined monthly for 12 months. In addition, mycorrhizal colonization of C. barbinervis seedlings grown in pots of field-collected soil was evaluated. Field-collected C. barbinervis roots were extensively colonized by arbuscular mycorrhizal fungi that exhibited the Paris-type morphology. At both sites, total colonization ranged from 4287% of root length and arbuscular colonization ranged from 631% of root length during the year. At one site, hyphal-coil colonization was between 3761% year round; at the other site, it increased from between 3056% during August-November to as high as 80% in January. Year round at both sites, vesicular colonization was 7% of root length or less. The Paris-type morphology was also seen in pot-grown C. barbinervis seedlings. Total colonization of pot-grown C. barbinervis seedlings was 3456% of the root length over 520 weeks. To our knowledge, this study is the first report of the mycorrhizal status of a plant in the Clethraceae and the first report of arbuscular mycorrhizae in any member of the Ericales.Key words: Paris-type, Japan, seasonal pattern, arbuscular mycorrhiza, Ericales.
The influence of mycorrhizal colonization on the vegetative growth and sexual reproductive potential of Lythrum salicaria L.
Authors: Philip Leanne J , Posluszny Usher , Klironomos John N
Published: April 2011

Lythrum salicaria L., purple loosestrife, is a heterostylous, perennial plant with prolific and at times invasive vegetative growth and sexual reproduction. Sexual reproduction occurs following pollination and fertilization between two different floral morphs. We investigated the influence of the arbuscular mycorrhizal fungus, Glomus aggregatum Schenck and Smith emend. Koske, on the vegetative growth and sexual reproductive potential of L. salicaria. Mycorrhiza decreased plant biomass both aboveground and belowground. Flower production, number of days to anthesis, numbers of flowers per inflorescence, and inflorescence lengths were not significantly different between mycorrhizal and non-mycorrhizal treatments. However, pollen production per anther and per flower increased with mycorrhizal colonization. Though ovule production was not affected, some aspects of purple loosestrife morphology did change. Plants with mycorrhizae produced inflorescence (in lateral positions) further up the stem. In addition, flower distribution within an inflorescence differed according to morph (short, mid, and long style) such that in the mid and long morphs flower number increased with inflorescence length and was unevenly distributed, while in the short morph this distribution appeared even. The relative biomass of stems, leaves, lateral branches, and reproductive structures were not significantly different in mycorrhizal plants, whereas in the absence of mycorrhizal colonization, stem biomass was higher relative to other structures. This study suggests some vegetative and reproductive characteristics in purple loosestrife change with an association with arbuscular mycorrhizal fungi.Key words: purple loosestrife, arbuscular mycorrhizal fungi, plant reproduction.
Vegetation, hydrology, and development of a coastal mire in Hokkaido, Japan, affected by flooding and tephra deposition
Authors: Hotes Stefan , Poschlod Peter , Sakai Hiroshige , Inoue Takashi
Published: April 2011

Mires in coastal lowlands in Hokkaido, northern Japan, have repeatedly been affected by flooding events and tephra (aerially transported volcanic ejecta) deposition during their development. Vegetation, hydrology, and stratigraphy of Kiritappu Mire in eastern Hokkaido were investigated along two transects and are discussed in relation to disturbance by mineral deposition. The vegetation pattern showed little relation to past geologic events. Five plant communities, two of which (A and C) could be further divided into subgroups, were distinguished (A, Alnus japonica - Spiraea salicifolia community; B, Sasa chartacea community; C, Myrica gale var. tomentosa - Sphagnum fuscum community; D, Carex lyngbyei community; E, Carex subspathacea - Aster tripolium community). Water levels, pH, electric conductivity, and ionic composition of groundwater and surface water were measured in communities A-C. Mean water levels were similar in communities A and C; in community B, it was lower. The pH was higher in community A than in communities B and C. Ion concentrations were influenced by sea water at some sites. Plant macrofossils and ash contents of 31 cores were analysed. Sedge roots were the dominant peat component, often mixed with remains of Phragmites australis, Sphagnum spp., and Polytrichum juniperinum var. strictum. Ash contents were high, and up to nine different mineral layers consisting of tephra, sand, silt, and clay were detected. In some cases, mineral deposition induced changes in the macrofossil composition of the peat. However, in a greater number of cases, no changes in the macrofossil composition were found at the mineral layers, and most shifts were not related to mineral deposition.Key words: mire, vegetation, hydrology, disturbance, flooding, tephra.
On the annular growth pattern in Scirpus maritimus in an intertidal wetland: extension of the concept of cyclic development to within-clone spatial dynamics
Authors: Jelinski Dennis E , Karagatzides Jim D , Hutchinson Ian
Published: April 2011

In a seminal work on community organization and succession, A.S. Watt presented evidence to show that some plant communities are in dynamic but cyclical equilibrium with their environment. Watt held that the resultant vegetation may have a patchy structure made up of different developmental phases ranging from "youngest" to "oldest" (termed "juvenile", "mature", "senile", and "slack"). At any given location, the vegetation repeatedly cycles through these phases over time. We extend Watt's concept of cyclic succession and phasic development to the study of within-clone spatial dynamics in Scirpus maritimus L. (Cyperaceae) colonizing an early succesional brackish-water environment. Specifically, we hypothesized that shoot populations of S. maritimus could be categorized into distinctive phases based on stem density and height and that differences in the developmental stage may be driven by a combination of biotic and abiotic controls. Data indeed show the existence of a strong annular banding pattern for stem density and height. The clone centres were characterized by a slack phase surrounded by bands of senile, mature, and juvenile phases. Clone boundaries were highly truncated, typical of a phalanx growth strategy. Further analysis revealed that the chemical and physical environment varies between phases within clones, which may drive within-clone stem dynamics. We conclude with a model of phasic clonal growth for S. maritimus that posits the effects of demographic density-dependence and physico-chemical environmental control on annular growth and within-clone spatial dynamics.Key words: clonal development, wetlands, cyclic succession, population demography, Scirpus maritimus, Watt.
Autecology of Erythronium grandiflorum in western Canada
Authors: Loewen Dawn C , Allen Geraldine A , Antos Joseph A
Published: April 2011

Habitat requirements of the yellow glacier lily, Erythronium grandiflorum Pursh, were studied at 38 sites in southern British Columbia and southwestern Alberta. At each site we recorded densities of E. grandiflorum growth stages from seedling to flowering, environmental characteristics of the site, and percent cover of associated plant species. We carried out detrended correspondence analysis (DCA) of the sites based on cover of associated species, and examined rank correlations between site environmental variables and site ordination scores. Variation among sites was related primarily to elevation and the presence of deciduous vs. coniferous trees. All growth stages of E. grandiflorum were less abundant in coniferous forests than in open areas or sites with deciduous trees, suggesting that evergreen canopies restrict the species on many sites where it could otherwise grow. Although E. grandiflorum populations were most commonly found in subalpine meadows, they flowered more abundantly in low-elevation populations. Recruitment was frequent, with seedlings occurring at many sites; we also showed that detached bulb segments can give rise to new ramets. The present widespread distribution of E. grandiflorum may derive from a post-glacial period with extensive meadow habitat that was favourable for rapid spread.Key words: canopy cover, elevation, yellow glacier lily, post-glacial migration, subalpine meadows.
Climate and the distribution of C4 grasses along the Atlantic and Pacific coasts of North America
Authors: Wan Cindy SM , Sage Rowan F
Published: April 2011

In this study, relationships between temperature, precipitation, and the percentage of C4 grasses in local grass floras from the Atlantic and Pacific coastal regions of North America were examined. The proportion of C4 species in a local grass flora increased as latitude decreased on both coasts. At a given latitude, the C4 percentage on the Atlantic coast was higher than the Pacific coast. This difference was related to the Atlantic coast having greater July minimum temperatures than Pacific coast locations of similar latitude. Linear regression analysis showed that the proportion of C4 species in a local flora was positively associated with July minimum temperature on both coasts. The regression line between July minimum temperature and C4 representation was similar for each coast, indicating growth-season temperature has a similar control over C4 presence on the two coasts. Proportionally more of the annual precipitation fell in midsummer on the Atlantic than the Pacific coast, but this difference in the seasonal occurrence of precipitation did not alter the relationship between July minimum temperature and the contribution of C4 grass species to local floras. The Atlantic coast locations with the most precipitation had the highest C4 grass occurrence, indicating aridity alone did not increase the C4 representation in a grass flora. On both coasts, the proportion of NADP-malic enzyme C4 species in local C4 grass floras was positively correlated with mean annual precipitation; however, at equivalent percentages of NADP-malic enzyme subtype occurrence, precipitation levels were substantially lower on the Pacific than Atlantic coast. The trend between latitude and the percentage of C4 species in exotic grass floras was similar to the trend between latitude and the percentage of all C4 grasses in an entire grass flora. Thus, the C4 pathway appears to play no obvious role in enhancing the invasibility of exotic grasses in North America.Key words: bioinvasions, biogeography, C4 photosynthesis, C4 subtype, Poaceae, photosynthesis.
The influence of jack pine tree and tissue age on the establishment of infection by the jack pine dwarf mistletoe, Arceuthobium americanum
Authors: Robinson D E , Punter D
Published: April 2011

The purpose of this study was to test the hypothesis that infection of jack pine (Pinus banksiana Lamb.) by jack pine dwarf mistletoe (Arceuthobium americanum Nutt. ex Engelm.) increases with increasing tree age and decreases with increasing tissue age. One-, 2-, and 3-year-old tissues of 3-, 5-, and 7- year-old jack pines and 1-, 4- and 8-year-old tissues of 12-, 17-, and 22-year-old jack pines in Belair Provincial Forest were inoculated with seed of A. americanum in September of 1992 (year 1) and 1993 (year 2). Overwinter and postwinter seed removal, fungal and insect damage, and infection success were monitored from the time of inoculation to harvesting of inoculated branches. In years 1 and 2, overwinter seed displacement was 12.2 and 30.6%, while postwinter loss was 28.8 and 22.2%, respectively. Seed germination ranged from 14.3 to 38.1% and from 3.1 to 17.5%, respectively, in years 1 and 2. Infection success varied from 2.0 to 35.0% (year 1) and from 0.0 to 13.0% (year 2). Lower mean daily temperatures in January and February (p < 0.001) were hypothesized to have killed more seeds and thereby reduced infection success in year 2. Infection success did not increase with increasing tree age (year 1: p = 0.188; year 2: p = 0.807) in either year of the study. Infection success increased with increasing tissue age in year 1 (p < 0.001) but not in year 2 (p = 0.358). We rejected the hypotheses that susceptibility to infection by A. americanum increases with increasing tree age or decreases with increasing tissue age of jack pine. Infection success appears to be primarily dependent upon seed displacement caused by wind, snow, or rain.Key words: jack pine, dwarf mistletoe, infectivity, juvenile resistance, seed displacement.
Development of cell wall modifications in the endodermis and exodermis of Allium cepa roots
Authors: Ma Fengshan , Peterson Carol A
Published: April 2011

The cytological events of wall modification in the endodermis and exodermis of Allium cepa L. roots were examined with fluorescence and transmission electron microscopy. In the endodermis, Casparian bands, suberin lamellae, and tertiary walls developed in succession. At the site of the future Casparian band, the plasma membrane was bound to the wall before deposition of detectable hydrophobic components in the radial wall. Suberin lamellae were deposited on the inner faces of the primary walls, first along the outer tangential walls and then the inner tangential walls. On both walls, segments of the lamellae were formed earlier in primary pit fields than at nonprimary pit field regions. Suberin lamellae then extended to the radial walls. When they reached the Casparian bands, the lamellae intruded between the bound plasma membranes and the walls, so that the cells' plasma membranes remained intact. In this way, suberin lamellae that were continuous around the cells were laid down. Later, tertiary walls were deposited internal to the suberin lamellae. None of the wall modifications interrupted the symplastic connections of the endodermis. During suberin lamella and tertiary wall formation, more dictyosomes and ER profiles appeared than during Casparian band development. In the exodermis, although Casparian bands were readily detected with fluorescence microscopy, they were rarely detected with electron microscopy. Suberin lamellae were formed in long cells severing their plasmodesmata. As in the endodermis, dictyosomes and ER were prominent during suberin lamella formation. Tertiary walls were not formed in the exodermis.Key words: Allium cepa, Casparian band, endodermis, exodermis, suberin lamella, ultrastructure.
The population structure ofArmillaria ostoyaeandArmillaria sinapinain the central interior of British Columbia
Authors: Dettman Jeremy R , van der Kamp Bart J
Published: April 2011

The population structures of Armillaria ostoyae (Romagn.) Herink and Armillaria sinapina Bérubé & Dessureault were investigated at a study site near Williams Lake in the central interior of British Columbia. One hundred and twenty eight fungal isolates were examined from nine infection centers and individual genets were delineated using random amplified polymorphic DNA (RAPD) analysis and somatic incompatibility tests. Six A. ostoyae genets ranging in size from 0.70 to >15 ha were detected. The population structure of A. ostoyae was consistent with a clonal reproductive strategy, and infection centers were occupied by single A. ostoyae genets or ramets thereof. Eighteen relatively small A. sinapina genets were detected, with infection centers being occupied by multiple genets. Armillaria sinapina appears to be more pathogenic to coniferous hosts than previously reported in the region. Armillaria ostoyae appears to initiate new infections of available substrate via airborne basidiospores at a lower frequency than A. sinapina. However once established, A. ostoyae can spread quite aggressively and capture significant amounts of secondary resources, while A. sinapina is unable to do so. The results of somatic incompatibility tests used to differentiate genets corresponded with the results of RAPD analysis, with only one minor discrepancy.Key words: Armillaria, RAPD, population structure, genet, ramet, clone.
The population structure of Armillaria ostoyae in the southern interior of British Columbia
Authors: Dettman Jeremy R , van der Kamp Bart J
Published: April 2011

The population structure of Armillaria ostoyae (Romagn.) Herink was investigated at a study site in the interior cedarhemlock zone of the southern interior of British Columbia. Eight 500-m long, randomly placed transects located at least 500 m apart were systematically sampled and individual genets were delineated using Random Amplified Polymorphic DNA (RAPD) analysis. Average genet intersect length was 79 m, and an estimated 88% of the area surveyed was occupied by genets <2 ha in size. The spatial distribution of genets in relation to one another was quite complex, with isolates of the same genet often non-contiguous along the transect. The location of genets could not be determined from aboveground symptom expression. Isolates collected from adjacent hosts within small groups of symptomatic hosts (infection foci) did not necessarily belong to the same genet, but single genets could occupy several infection foci. There was no relationship between geographic distance and genetic similarity of genets, suggesting random mating events for genet origin and long term maintenance of genetic identity.Key words: Armillaria, RAPD, population structure, genet, ramet, clone.