bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in phenolic constituents of maize silk infected with Fusarium graminearum
Authors: Reid L. M. , Mather D. E. , Arnason J. T. , Hamilton R. I. , Bolton A. T.
Published: April 2011

The concentration of phenolic compounds in the silks of five maize inbred lines ('CO272', 'F7', 'F2', 'A641', and 'CO266') of varying susceptibility to Fusarium graminearum was determined at three stages of silk development. The level of phenolic compounds in noninoculated silk tissue increased with silk development for only two of the inbreds. A suspension of F. graminearum spores was sprayed on the exposed silk of the same inbreds. Silk tissue collected from the silk channel 1 to 14 days after this inoculation was analyzed for phenolic compounds. The level of phenolic compounds increased relative to a water control in the most resistant line 'CO272' and decreased relative to water controls in susceptible lines. From thin layer chromatography of the phenolic extracts, flavones were the major phenolic compounds present. Five flavones were identified using high performance liquid chromatography: iso-orientin, iso-vitexin, maysin, luteolin, and apigenin. Key words: maize, corn, Fusarium graminearum, silk, phenolic, flavone.
Phylogenetic origin of the Monotropoideae inferred from partial 28S ribosomal RNA gene sequences
Authors: Cullings K. W. , Bruns T. D.
Published: April 2011

Despite more than 100 years of detailed analysis of morphology and macromolecules, the phylogenetic origin of the Monotropoideae remains unclear. In this study partial sequences from the 28S rRNA gene were used to test two alternative hypotheses: (i) that the Monotropoideae share a most recent common ancestor with the Arbutoideae in the Ericaceae or (ii) that the Monotropoideae is the end result of a gradual transition from autotrophism to mycotrophic parasitism in the Pyrolaceae. Our results support the hypothesis that the Monotropoideae and the Arbutoideae are a monophyletic group and that the Monotropoideae should be included in the Ericaceae rather than the Pyrolaceae. The Monotropoid species Pleuricospora fimbriolata could not be placed within either the Monotropoideae or the Arbutoideae with any degree of confidence, leaving open the possibility that the Monotropoideae is polyphyletic. Key words: Monotropoideae, Ericaceae, 28S rRNA gene, PCR, molecular systematics.
The phylogenetic relationships of the anaerobic chytridiomycetous gut fungi (Neocallimasticaceae) and the Chytridiomycota. II. Cladistic analysis of structural data and description of Neocallimasticales ord.nov.
Authors: Li Jinliang , Heath I. Brent , Packer Laurence
Published: April 2011

We investigated the phylogenetic relationships of the Chytridiomycota and the chytridiomycetous gut fungi with a cladistic analysis of 42 morphological, ultrastructural, and mitotic characters for 38 taxa using both maximum parsimony and distance algorithms. Our analyses show that there are three major clades within the Chytridiomycota: the gut fungi, the Blastocladiales, and the Spizellomycetales–Chytridiales–Monoblepharidales. Consequently, we elevated the gut fungi to the order Neocallimasticales ord.nov. Our results suggest that a modified Chytridiales, including the Monoblepharidales, is a monophyletic group. In contrast the Spizellomycetales are paraphyletic because the Chytridiales arose within them. The separation of the traditional Chytridiales into two orders is thus doubtful. Although the Blastocladiales are closer to members of the Spizellomycetales than the Chytridiales, the cladistic analyses of both structural and rRNA sequence data do not support the idea that the Blastocladiales were derived from the Spizellomycetales. We suggest emendations to the classification of the Chytridiomycota and note which groupings require further analysis. Our phylogeny for the currently recognized species of gut fungi is inconsistent with the existing classification. Nonetheless, pending further investigations, we prefer to retain the existing, easily defined genera for which a key is provided. Key words: Chytridiomycota, rumen fungi, phylogeny, morphology, ultrastructure, mitosis.
Morphology and zoospore ultrastructure of Lacustromyces hiemalis gen. et sp.nov. (Chytridiales)
Authors: Longcore Joyce E.
Published: April 2011

As part of a baseline study of chytridiomycete fungi in two Maine lakes, a polycentric, chitinophilic, and heretofore undescribed zoosporic fungus was found. The tubular thallus of Lacustromyces hiemalis gen. et sp.nov. has intercalary thin-walled zoosporangia, has thick-walled resistant sporangia, and does not grow at temperatures greater than 23 °C. Transmission electron microscopy revealed that its zoospores are a variant of the chytridialean type. The microbody – lipid globule complex is of a previously undescribed type, lacking a rumposome or other membrane cisterna and consisting of multiple lipid globules enclosed in a microbody that extends towards the kinetosome. Three kinds of microtubule roots arise near the kinetosome, a root leading to the microbody, a ribosomal root, and a microtubule organizing center that gives rise to microtubules that extend singly into the cytoplasm. Key words: Chytridiales, fungus, Lacustromyces, lake, ultrastructure, zoospore.
Production of uredinia and telia by stalactiform blister rust in British Columbia
Authors: van der Kamp B. J.
Published: April 2011

Records of uredinia and telia production on the alternate hosts of Cronartium coleosporioides in British Columbia and inoculation of Castilleja miniata with aeciospores collected from various locations showed that rust isolates from dry areas of the interior of British Columbia do not produce uredinia and may have lost the ability to do so. Collections from somewhat wetter areas produced uredinia or mixtures of uredinia and telia immediately following aeciospore inoculations, and field collections from such areas in June commonly had mixtures of uredinia and telia. Loss of the uredinial stage may be a response to climates that are often unsuitable for the spread or survival of the rust on the alternate host. Key words: stalactiform rust, uredinia, telia, rust life cycle.
Panicle, spikelet, and floret development in orchardgrass (Dactylis glomerata)
Authors: Fraser Joanna , Kokko Eric G.
Published: April 2011

The initial stages of panicle, spikelet, and floret development in field-grown 'Kay' orchardgrass were examined using scanning electron microscopy. Spikelets arose from a complex multilevelled sequence of initiation from branch apices. Spikelets developed indirectly in a two-tiered progression: (i) an acropetal and basipetal sequence of first order, second-order, and third-order inflorescence apices, and (ii) an acropetal development within subclusters of higher-order lateral branch inflorescence apices. The panicle had the unique feature of dorsiventrality as well as bilateral symmetry. The basal apex from first-order, second-order, or third-order apices developed on the same side of the main axis as the first-order apex. The two glumes subtending each spikelet primordium developed alternately and acropetally. Development and initiation of florets within spikelets was basipetal within the panicle, basipetal within clusters and subclusters of spikelets on lateral branches, and acropetal within spikelets. Within florets, paleas developed later than lemmas. Key words: Dactylis glomerata, cocksfoot, scanning electron microscopy, development, panicle.
Growth and physiological responses of sorghum cultivars exposed to excess H+ and the herbicide metolachlor
Authors: Wilkinson R. E. , Duncan R. R. , Meredith S. A. , Hatzios K. K.
Published: April 2011

The growth responses of six grain sorghum (Sorghum bicolor (L.) Moench) cultivars exposed to single and (or) combined treatments of the herbicide metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methlethyl)acetamide) and excess H+ were investigated under growth chamber conditions. The sorghum cultivars tested were '38M', '58M', 'GP-10', 'SC574', 'SC283' (inbred lines), and 'Funk G522DR' (F1 hybrid). Shoot lengths were measured on seedlings from each cultivar grown for 14 days in white quartz flintshot sand treated with metolachlor at 0, 0.25, 0.5, 1.0, and 2.0 mg/kg. Pots were watered with 100 mL of 0.1 M acetate at pH 6.0, 5.5, 5.0, 4.5, or 4.0 on alternate days. A sorghum mutant ('58M') shown to have enriched gibberellin levels and '38M', a second sorghum mutant, were essentially immune to either metolachlor (2 mg/kg) or excess H+ concentration (pH 4.0). 'Funk G522DR' was sensitive to both excess H+ concentrations and metolachlor, and interactions between these two stresses were evident. The remaining cultivars were intermediate in response to both excess H+ concentration and metolachlor. Glutathione contents and glutathione S-transferase activities of the metolachlor-resistant 'GP-10' and the metolachlor-sensitive 'Funk G522DR' were comparable. Thus, enriched gibberellin levels may be a major factor in the differential response of the tested sorghum cultivars to metolachlor and (or) excess H+ stresses. Phenological response in relation to multiple stresses is discussed. Key words: pH, metolachlor, gibberellin, acid soil.
Morphologie et structure des hyphes externes observées sur le péridium des Tuber à écailles: évolution au cours du développement de l'ascocarpe
Authors: Barry D. , Callot G. , Janex-Favre M. C. , Parguey-Leduc A. , Pargney J. C.
Published: April 2011

Macro-, micro- and ultra-structural analyses were carried out at the soil–ascocarp interface of different species of Tuber (T. aestivum, T. melanosporum, T. uncinatum) during the organogenesis of the ascocarp. Four external hyphae networks are described: a double network at the upper part of the young ascocarp, hyphal tufts at the tip of the pyramidal scales, and short hyphae extending from the sterile veins of the gleba. This external hyphal system establishes a continuum between the soil and the ascocarp and assures the nutritional autonomy of the subterranean fructification. Key words: truffle (Tuber), ascocarp, hyphae (structure), microstructural analysis.
Biocontrol potential of rust of groundnut by Acremonium obclavatum
Authors: Gowdu B. Jayapal , Balasubramanian R.
Published: April 2011

Acremonium obclavatum was frequently found associated with pustules of the rust fungus Puccinia arachidis on groundnut in Madras, India. Inoculation of A. obclavatum before, with, or after inoculation with P. arachidis reduced the number and size of uredosori both on intact and detached leaves of groundnut plants. Treatments with A. obclavatum resulted in reductions in number of pustules and uredospores, delay in maturity and opening of uredosori, and reduced viability of uredospores. The application of culture filtrates of A. obclavatum also reduced the number and size of pustules on intact and detached groundnut leaves. The potential use of A. obclavatum in biological control of groundnut rust is discussed. Key words: groundnut, Arachis hypogaea, groundnut rust, Puccinia arachidis, Acremonium obclavatum, biological control.
Correlation between generated morphological character data and flavonoid content of species in the Muhlenbergia montana complex
Authors: Herrera-Arrieta Yolanda , Grant William F.
Published: April 2011

Taxonomic descriptions in English and Spanish and a key to 16 closely related species of the Muhlenbergia montana (Nutt.) Hitchc. complex were generated by means of DELTA computer programs, using data gathered from a morphological character list. Data from chromatographic analyses of the flavonoid content of 14 species were recorded in DELTA format and analyzed separately. Both data sets when analyzed independently, and together they suggest that Muhlenbergia virescens (H.B.K.) Kunth is ancestral with other species evolving from it in specific geographic regions. The data provided a basis for clearly separating the annual species (Muhlenbergia crispiseta and Muhlenbergia peruviana) from the perennial species in this complex. A phenetic comparison of the morphological and chemical features suggests a different rate of divergence for chemical and morphological characters among species in this closely related group of taxa. Key words: Muhlenbergia montana, Poaceae, Gramineae, flavonoids, taxonomic descriptions.
Structural and histochemical features of Stylosanthes scabra (Leguminosae; Papilionoideae) seed coat as related to water entry
Authors: Serrato-Valenti G. , Cornara L. , Ferrando M. , Modenesi P.
Published: April 2011

The structural and histochemical features of the seed coat of Stylosanthes scabra Vog. were investigated by bright-field and fluorescence light microscopy, and scanning electron microscopy. The palisade cells consisted of two parts, different in structure and in histochemical characteristics: an upper furrowed part and an irregularly ending cylindrical part. The former showed a light line just below the outer ends that owing to the presence of callose, could act as a water barrier. In the hilar region a raised circular outgrowth all around the hilar fissure consisted of two parts: the rim aril, a rampart-like border of vertically oriented cells, and the remaining part with a roughly triangular-shaped cross section called funicular remnants. The rim aril showed affinity with alcian blue and did not fluoresce with either auramine O or aniline blue. It did not hinder water entry. The funicular remnants, except the parts towards the hilar fissure, reacted positively with ferric chloride and vanillin and fluoresced intensely with aniline blue and auramine O. Thus it is possible that three substances are involved in impermeability at this level: phenolics, callose, and hydrophobic lipid substances. In the hilar area, another more internal water barrier could be the prominent light line. Key words: Stylosanthes scabra, seed coat, structure, histochemistry.
Avian dispersal of Frankia
Authors: Paschke Mark W. , Dawson Jeffrey O.
Published: April 2011

Nests of six common bird species in central Illinois, U.S.A. were collected and examined for the presence of Frankia capable of infecting Alnus glutinosa and Elaeagnus umbellata. Serial dilutions of nest extracts were used in a bioassay to estimate the number of Frankia nodulation units for these two host species in each nest. Nests of two bird species contained soil as a nest component and had high concentrations of Frankia nodulation units. Nests of two bird species that did not use soil in nest building also had relatively high levels of Frankia. Results indicate that some bird species can transport Frankia, possibly by moving soil for nest building and also by other unknown mechanisms. Key words: actinorhizae, bioassay, bird nests, Frankia dispersal, Alnus glutinosa, Elaeagnus umbellata.
Nutrition of ovule, embryo sac, and young embryo in soybean: an anatomical and autoradiographic study
Authors: Chamberlin Mark A. , Horner Harry T. , Palmer Reid G.
Published: April 2011

Photosynthesizing soybean plants were exposed to 14CO2 to study the incorporation of labeled water-insoluble photosynthates in ovules at various developmental stages. Using autoradiographic techniques on sectioned material, we show that the distribution of labeled carbon in different ovular tissues is regulated spatially and temporally. During zygote through globular stages of embryo development, labeled assimilates accumulate in integumentary tissue adjacent to the micropylar and chalazal poles of the embryo sac. A chalazal vascular trace and two adfunicular vascular strands are the pathways for accumulation of 14C in these regions. Up through the proembryo stage, movement of labeled photoassimilates into the lateral regions of the embryo sac seems blocked by a cuticle-like layer between the endothelium and embryo sac. At the globular embryo stage, the greatest accumulation of label is still at the chalazal and the micropylar ends of the embryo sac, but fragmentation of the cuticle-like barrier coincident with cellularization of endosperm allows channeling of labeled carbon from adjacent integumentary tissue into the embryo sac as well. Autoradiographic evidence for carbon flow into the embryo sac can be correlated with ultrastructural and morphological changes in time in ovular and endosperm tissues enclosing the embryo. Key words: autoradiography, embryo sac, Glycine, nutrition, ovule.
Fine structure of ascosporogenesis in Ceratocystiopsis proteae
Authors: Wyk P. W. J. Van , Wingfield M. J.
Published: April 2011

The development and ultrastructure of the ascoma, asci, and ascospores in Ceratocystiopsis proteae were studied and compared with that of other genera in Ceratocystis sensu lato. Ascospore delimitation commenced with the formation of double delimiting membranes in the ascus as is true in other species in Ceratocystis s.l. The ascospore wall developed between these membranes. In contrast with three wall layers observed in other species, only two wall layers were observed in C. proteae. Falcate sheaths previously reported in light-microscopic studies were not observed. The falcate appearance of ascospores may be ascribed to the adherence of a matrix to the outermost wall layer during ascospores release. Differences between this species and others in Ceratocystis s.l. illustrate the problems that can arise from the use of single morphological characteristics in the taxonomy of this group. It is accordingly suggested that the genus Ceratocystiopsis requires taxonomic revision. Key words: Ceratocystiopsis, falcate ascospores, sheaths, centrum.
Seed dimorphism in relation to germination and growth of Cakile edentula
Authors: Zhang Jianhua
Published: April 2011

Previous studies showed that the two seed morphs produced from the upper and lower fruit segments of Cakile edentula differed significantly in their germinability and carry-over effects on the growth of the subsequent plants. By partitioning variables into seed-morph and seed-mass components, this study suggests that both seed germination and the growth of the subsequent plants depend on seed mass rather than seed morph. Plants from large seeds generally had greater leaf area, shoot to root ratio, biomass, and smaller leaf area ratio than those from small seeds. Within the same seed-mass class, plants from the lower fruit segment showed greater shoot to root ratio only at the end of the experiment. Since specific leaf area, leaf area ratio, and shoot to root ratio depended significantly on plant dry mass, the effect of seed mass on these variables may be actually achieved indirectly through the influence on plant size. Key words: seed dimorphism, seed mass, maternal effect, germination, growth, Cakile edentula.
Modem pollen spectra from west central British Columbia
Authors: Hebda Richard J. , Allen Gregory B.
Published: April 2011

Sixty-four moss and organic litter samples were collected from five biogeoclimatic zones distributed from sea level on the central coast of British Columbia onto the western edge of the Interior Plateau at 1000 – 1900 m and analyzed for pollen and spores. Four of the five biogeoclimatic zones produced characteristic pollen and spore spectra. The coastal western hemlock biogeoclimatic zone is characterized by Tsuga heterophylla, Alnus, and Cupressaceae. Significant levels of nonarboreal pollen (NAP), mainly Lysichiton and fern spores, occur in some sites. Interior Douglas-fir zone samples are dominated by Pseudotsuga and Tsuga heterophylla with notable Betula, Cupressaceae, and Alnus. Pinus pollen becomes the dominant type at the eastern margins of the interior Douglas-fir zone and dominates the Engelmann spruce – subalpine fir, montane spruce, and sub-boreal pine–spruce biogeoclimatic zones at high and intermediate elevations to the east. In the Engelmann spruce – subalpine fir zone, Abies pollen is characteristically more abundant than Picea, and notable percentages of NAP, especially Artemisia, occur. In the transition from Engelmann spruce – subalpine fir zone to montane spruce zone, Abies and Picea percentages are about equal or Picea predominates slightly, whereas in the montane spruce zone and sub-boreal pine spruce zones, Picea values exceed Abies values often four to five times. Percent pollen and spore versus percent taxon cover diagrams, despite widely spread values, reveal general relationships and background pollen rain values for major taxa valuable to the interpretation of fossil pollen assemblages. Pinus is greatly overrepresented with a regional background of 10–15%. At low to intermediate cover values, Tsuga heterophylla, Pseudotsuga, and Cupressaceae are represented more or less as they occur in the vegetation, with regional backgrounds up to 5%. Picea and Abies are underrepresented, with regional background value of 0–3%. Key words: pollen, surface spectra, biogeoclimatic zones, species cover, British Columbia.
Infection of beech leaves (Fagus sylvatica) by the endophyte Discula umbrinella (teleomorph: Apiognomonia errabunda): low-temperature scanning electron microscopy studies
Authors: Viret Olivier , Scheidegger Christoph , Petrini Orlando
Published: April 2011

The sequence of events leading to infection by Discula umbrinella of leaves taken from axenically grown beech seedlings was studied at the ultrastructural level. On the host surface, even under optimal conditions and when contact with the host is established, only approximately 70% germination can be observed. In hanging drops containing malt extract, germination is only approximately 10%, suggesting that abundant nutrient supply alone is not enough to promote germination. Incubation of conidia in leaf extracts, on the other hand, results in the induction of germination even if no contact with an appropriate support is established. Between 16 and 24 h after infection four stages of germination can be observed on beech leaves: (i) ungerminated conidia; (ii) germinating conidia producing long superficial hyphae; (iii) conidia with distinct, appressorium-like swelling at the end of the germ tube; and (iv) germinated conidia with a halo around the tip of the germ tube. Transmission electron microscopy shows that subcuticular penetration into the host occurs at places where halos are seen. Apparently only germination with formation of appressorium-like structures and halos leads to successful penetration. Application of conidia to the abaxial side of the host leaf results in the formation of structures similar to those observed on the adaxial surface. Conidial germ tubes penetrate the cuticular layers of the outer edges of the guard cells, but direct penetration through the stomata was rarely observed. Appressorium or halo formation, observed only on the host surface and never on other substrates, suggests host-specific induction of penetrating structures. The mode of penetration observed for D. umbrinella bears some similarities with that described for some biotrophs and pathogens, suggesting affinities between endophytes and pathogens. Key words: beech anthracnose, electron microscopy, endophytes, latent pathogens, ultrastructure.
Genetic transformation of the vascular wilt fungusVerticillium dahliae
Authors: Dobinson Katherine F.
Published: April 2011

To facilitate genetic analysis of pathogenicity of Verticillium dahliae, a vascular wilt pathogen, a DNA-mediated transformation system has been developed. Resistance to hygromycin B was obtained by transforming spheroplasts with the cosmid vector pAN7-2. Transformation efficiencies ranged between 3 and 5 transformants/μg vector DNA. The transforming DNA was integrated into the V. dahliae genome, in single and multiple copies and in tandem array. In several multicopy transformants, minor alterations in the integrated DNA sequences were evident following extensive vegetative growth in the absence of hygromycin B. Electrophoretic karyotype analysis also provided direct evidence of chromosome rearrangements in two transformants. The availability of a transformation system for V. dahliae will facilitate the cloning and characterization of genes that are important for pathogenicity and development. Key words: Verticillium wilt, fungal transformation, electrophoretic karyotype, hygromycin B resistance, chromosome rearrangement.
A seed trap for monitoring the seed rain in terrestrial communities
Authors: Schott Gary W.
Published: April 2011

Monitoring the seed rain of a species, population, or community is important to quantify that component of life history that follows anthesis yet precedes establishment in the seed bank or as a seedling. I have developed a unique seed trap that is ideal for monitoring the seed rain of a grassland community. The trap consists of a 10-cm diameter funnel attached by Velcro to one end of a 15-cm long PVC pipe. The trap is sunk into the ground with 1.5–2 cm protruding above the soil surface to prevent soil and ground-dwelling insects from entering the trap. A small cotton bag is attached to the stem of the funnel and acts as the reservoir for trapped seeds. I was able to trap propagules ranging in size from 0.5-mm seeds (Juncus interior) to > 2 cm long awned spikelets (Andropogon gerardii). Because this trap minimizes prédation, is easy to construct and monitor, and is inexpensive, it is superior to traps used by previous researchers. Key words: seed trap, seed rain, sampling methodology.
Chromosome location of mycorrhizal responsive genes in wheat
Authors: Hetrick B. A. D. , Wilson G. W. T. , Gill B. S. , Cox T. S.
Published: April 2011

Symbiotic relationships between wheat plants and mycorrhizal fungi may play an important role in the growth and productivity of wheat as a crop. Wheat cultivars differ in their ability to form such relationships, but little is known concerning the genetic basis of such differences. A set of intervarietal substitution lines having individual chromosomes from 'Cheyenne' (nonresponsive to mycorrhizae) substituted into 'Chinese Spring' (nonresponsive to mycorrhizae) were tested for mycorrhizal response in greenhouse experiments. Chromosomes 1A, 5B, 6B, 7B, 5D, and 7D of 'Cheyenne' had positive effects on the trait, with homologous groups 5 and 7 in the B and D genomes having the largest effects. Chromosome 5B of 'Hope', a nonresponsive cultivar, also had a positive effect in a 'Chinese Spring' background. In addition, the mycorrhizal responsiveness of a range of other cultivars and ancestors was tested to expand information on the trait in wheat and its relatives. Data on chromosome location of mycorrhizal-response genes and genotypic responsiveness will permit more effective genetic manipulation of this trait. Key words: pathogenesis, growth response, vesicular–arbuscular mycorrhizae.
Calcium translocation, calcium oxalate accumulation, and hyphal sheath morphology in the white-rot fungusResinicium bicolor
Authors: Connolly Jon H. , Jellison Jody
Published: April 2011

The white-rot fungus Resinicium bicolor was cultured on wood blocks in a modified soil block assay and was observed by environmental scanning electron microscopy and scanning electron microscopy. Resinicium bicolor was found to translocate calcium in mycelial cords in quantities greater than that found in the wood blocks and accumulated this calcium in the form of calcium oxalate. Calcium oxalate crystal clusters of mycelial cords were 3 × larger and far more numerous than the crystal clusters produced by the same fungus within the wood. Environmental scanning electron microscopy technology allowed for the examination of the hyphal sheath in a hydrated state. The hydrated hyphal sheath was found to be much thicker than the desiccated sheath observed after standard scanning electron microscope preparations. Calcium oxalate crystals were found to be embedded in the thick hyphal sheath, suggesting that previous observations of within-wall calcium oxalate precipitation may perhaps be better interpreted as artifacts generated during sample preparation. Key words: calcium oxalate, hyphal sheath, environmental scanning electron microscopy.
The effects of burning on Festuca hallii in the parklands of central Alberta
Authors: Gerling Heather Sinton , Bailey Arthur W. , Willms Walter D.
Published: April 2011

The response of Festuca hallii (Vassey) Piper to time of burning was examined on the Festuca–Stipa grasslands of the Aspen Parklands at the University of Alberta Ranch located 150 km southeast of Edmonton, Alberta. Two defoliation treatments (burning and mowing) were examined on five dates in 1978 (8 April, 27 April, 1 June, 31 July, and 18 October), corresponding to different phenological stages of F. hallii. Burning and mowing reduced the standing crop of F. hallii produced in the first growing season after treatment, but tiller densities increased. Defoliation in early spring (8 April) had little effect on the standing crop; apparently the increase in tiller density compensated for the reduction in tiller length. Inflorescence density also increased following burning or mowing from 8 April to 1 June. Soil temperature (3 cm deep) on previously burned or mown sites was greater than on the control the year after treatment. Festuca hallii tolerates single burns at any time of the year, but early spring fires have the greatest benefits by increased tillering and standing crop. Key words: standing crop, tiller number, leaf length, litter, defoliation, mowing.
Ecosystem health and integrity?
Authors: Wicklum D. , Davies Ronald W.
Published: April 2011

The concepts of ecosystem health and ecosystem integrity are discussed and found to be ecologically inappropriate. The phrase ecosystem health is based on an invalid analogy with human health requiring acceptance of an optimum condition and homeostatic processes maintaining the ecosystem at a definable optimum state. Similarly, ecosystem integrity is not an objective, quantifiable property of an ecosystem. Health and integrity are not inherent properties of an ecosystem and are not supported by either empirical evidence or ecological theory. Key words: ecosystem health, ecosystem integrity, ecosystem, management, sustainability.
Development of Cucurbita pepo pollen: ultrastructure and histochemistry of the sporoderm
Authors: Nepi M. , Ciampolini F. , Pacini E.
Published: April 2011

Sporoderm development is described in Cucurbita pepo, a species characterized by large spinous pollen grains covered by pollenkitt; i.e. the degeneration product of the tapetum. During the tetrad stage, separate types of primexine are observed for microspines and macrospines. At maturity these spines are affected differently by acetolysis: microspines contain polysaccharides as well as sporopollenin, and macrospine contain only sporopollenin. Unlike other species investigated so far, the intine begins to form at the early microspore stage and is very complex in the pore area where it forms a Zwischenkörper. The pore is covered by a protein layer of sporophytic origin and by the operculum. Just before anther opening, the pore protrudes, exposing part of the poral intine. Mature pollen has a thin callosic wall. The findings are discussed in the light of the fact that Cucurbita pepo pollen does not dehydrate prior to anthesis. Key words: Cucurbita pepo, pollen, sporoderm, exine, intine, sporophytic proteins.
Growth response ofFestuca altaica,Festuca hallii, andFestuca campestristo temperature
Authors: King Jane R. , Hill Michael J. , Willms Walter D.
Published: April 2011

In Alberta, the rough fescue complex consists of Festuca altaica Trin., Festuca hallii (Vasey) Piper, and Festuca campestris Rydb. The potential commercial value of these species for grazing, and their ecological significance, necessitates an increased understanding of their environmental adaptation. This study compared the growth response of the three species at five temperature regimes of 7:3, 12:8, 17:13, 22:18, and 27:23 °C (light:dark; 18-h photoperiod). Seedlings were established and grew for 10 weeks at 18 °C before being trimmed to a height of 3.5 cm and randomly assigned (36 pots of each species) to the growing environments. Growth was followed for 12 weeks. Temperature had a significant effect on most plant variables but the response differed among species. The optimal temperature for dry matter accumulation was 17:13 °C, and for tillering 12:8 to 17:13 °C. Festuca hallii and F. campestris exhibited a faster tillering rate than F. altaica, which had the heaviest tillers and highest leaf extension rate. The root to shoot ratio declined at temperatures above 17:13 °C. The significance of these observations to the geographical distribution of the species is discussed. Key words: rough fescue, defoliation, yield, growth analysis, adaptation.
The relationship of chrysophycean stomatocysts to environmental variables in freshwater lakes in British Columbia
Authors: Duff Katharine E. , Smol John P.
Published: April 2011

The relationships between the distributions of 82 chrysophycean cyst morphotypes and measured environmental variables in freshwater lakes in British Columbia were examined using ordination and regression statistics. After removal of unusual samples, 60 lakes were included in the analyses. Indirect and direct gradient analysis explained 23.2 and 14.0% of the variance in the cyst distribution data, and 31.4 and 53.7% of the variance in the cyst–environment relationship, respectively. Watershed area, Secchi depth and [Mg] were identified as the variables with the greatest contributions to the first ordination axis. Maximum depth contributed most strongly to axis 2. Constrained redundancy analyses were used to test the ability of individual environmental variables to explain the variance in the cyst data; no one variable was shown to have an overriding effect on cyst distributions. Five groups of cysts were identified using the ordination diagrams and the correlations between each cyst and each environmental variable. Partial least squares regression was used to construct inference models that quantified the relationship between the cyst distributions and four environmental variables (pH, [Mg], total phosphorus, and Secchi depth). For each variable, the best model included only those cysts which were significantly correlated with that variable. The inference model for pH yielded the strongest relationship (r2 = 0.51) and best predictive ability (root mean square error of prediction = 0.32). All the inference models showed a strong trend in the residuals, such that inferences at the low end of the observed gradient tended to be overestimates and inferences at the high end tended to be underestimates. Thus, paleolimnological inferences of past environmental conditions using these models will tend to underestimate the degree of change. Key words: British Columbia, phytoplankton, Chrysophyceae, stomatocysts, paleolimnology, eutrophication.
Morphogenèse comparée de protocormes du Cypripedium acaule (Orchidaceae) cultivés in vitro avec ou sans sucre
Authors: Leroux Gilles , Barabé Denis , Vieth Joachim
Published: April 2011

Seeds of the terrestrial orchid Cypripedium acaule from temperate regions contain an undifferentiated embryo consisting of about one hundred cells. These cells contain lipid and protein storage reserves. The development of the seeds was studied in vitro on a germination medium with or without dextrose (glucose). On the medium containing dextrose, proembryos develop and form a protocorm. From the anterior pole of the protocorm appears a "promeristem", a structure that will form a scale and the apex of the seedling. The formation of the root never precedes that of the apex. In the protocorm, the amount and size of starch grains show an increasing antero-posterior gradient. Only the apex, the procambium, and the secretory cells do not accumulate starch grains. On the medium without dextrose, the proembryos develop slowly into a protocorm, and a semi-meristematic region can be recognized at the anterior pole. However, no other tissue differentiation occurs and the protocorm soon degenerates without having undergone organogenesis. The protocorm accumulates a few starch grains, more voluminous and more numerous at the posterior pole, that agglomerate around the nucleus; but during the development, these rapidly disappear from the cells. Generally, all cells are strongly vacuolated. These observations indicate that orchid seeds cannot reach the seedling stage without a sugar input, which is ensured by a fungal symbiont in nature. Key words: Orchidaceae, morphogenesis, protocorm, starch, sugar effect, in vitro germination.
Discovery of permineralized plant fossils (coal balls) in the Bolsovian (e.g., Westphalian C) (Middle Pennsylvanian, Upper Carboniferous), Stellarton Basin, Nova Scotia, Canada
Authors: Lyons Paul C. , Millay Michael A. , Zodrow Erwin L. , Cross Aureal T. , Gillis Kevin S.
Published: April 2011

Permineralized plant fossils (coal balls) of Bolsovian age (ex Westphalian C) were discovered in the Foord seam of the Stellarton Basin of Nova Scotia. The coal-ball plants were preserved in a siderite–dolomite matrix and formed in a nonmarine intermontane setting. The coal-ball flora is dominated by arborescent lycopods and contains a few ferns, as well as occasional seed ferns, calamiteans, and cordaiteans. The following taxa were identified: Diaphorodendron, Paralycopodites brevifolia, Lepidocarpon lomaxii, Stigmaria, Scolecopteris, Botryopteris tridentata, Medullosa, Heterangium, Astromyelon, and Cordaianthus. This assemblage contains plants typical of Westphalian coal-swamp floras and helps fill a stratigraphie gap in Westphalian coal-ball floras of Euramerica. Key words: permineralized plants, coal balls, Carboniferous, Canada.
Wound healing in whole potato tubers: a cytochemical, fluorescence, and ultrastructural analysis of cut and bruise wounds
Authors: Thomson Norman , Evert Ray F. , Kelman Arthur
Published: April 2011

Healing was investigated in whole tubers wounded by cuts and bruises and compared with core, disc, and slice wounds. Bright-field, fluorescence, and transmission electron microscopy were used in conjunction with cytochemical analyses. Wound reaction cells bordering a wound site responded to wounding initially with deposition of callose at the primary pit fields followed by intussusception of lignin in the middle lamellae and primary walls and suberization along the inner surfaces of the primary walls. Suberization was initially detected by the presence of a prosuberin lamella in which suberin lamellae subsequently developed. Both lignin and the prosuberin lamella were first detected in wound reaction cells of the cortex at 4 h in cut, core, disc, and slice wounds and at 8 h in bruise wounds. Healing was completed with formation of a continuous wound cork cambium beneath the wound site. With lignification and suberization, wounded potato tubers apparently develop specialized barriers against potential pathogens and water loss. The overall healing process proceeds more slowly in bruise wounds than in cut wounds. Moreover, the capacity for wound healing decreases with increasing age of the tuber, or time in storage. Key words: lignin, prosuberin lamella, Solanum tuberosum, suberin, suberization, wound healing.
Leaf traits and shoot performance of an evergreen shrub, Ledum palustre ssp. decumbens, in accordance with latitudinal change
Authors: Kudo Gaku
Published: April 2011

Individual leaf traits, leaf age structure, and leaf dry mass of Ledum palustre ssp. decumbens were compared at three sites along a latitudinal gradient: temperate mountain (43°30′N), taiga (62°10′N), and arctic tundra (71°25′N). At the arctic site, L. palustre produced leaves having longer life-span, higher nitrogen concentration, and smaller size and specific leaf area (SLA) in comparison with that at the temperate mountain site. Although current leaf number and annual shoot growth were smaller, leaf dry mass per stem was larger at the arctic site than at the temperate mountain site. At the taiga site, those traits were within the range of the other two sites, with the exception of leaf size and total leaf number per stem, which were largest at the taiga site. Leaf life-span was negatively correlated to SLA and annual leaf number per stem and positively correlated to leaf nitrogen concentration. Thus, with increasing latitude, L. palustre produced fewer but more costly leaves and retained them for longer. Old leaves might have a resource storage function supporting new leaf production. Key words: latitude, leaf life-span, Ledum palustre, nitrogen, specific leaf area.
Analyse de la croissance primaire de rameaux de pommier (Malus ×domestica Borkh.) au cours d'une saison de végétation
Authors: Lauri P. E. , Térouanne E.
Published: April 2011

Primary growth resulting from the activity of the apical meristem of apple branches (Malus ×domestica Borkh., cv. Braeburn) was followed over one period of vegetation. For each metamere successively developed, foliar surface expansion as well as growth in length and in diameter of the lower internode were measured at regular intervals. These elementary parameters are resumed using two synthetic variables expressing for each metamere its overall dimension (T) and the relative significances of the foliar component (foliarization) or the axial component (axialization) (D). It appears that the evolution of the last two parameters are morphometric markers for the different ontogenetic phases covered by the branch over 1 year of growth. Two phases were especially studied: the transition preformation–neoformation (corresponding to the setting up of the first 9–11 metameres), characterized by strong axialization dynamics, and the intra-annual end of growth, preceded by an important foliarization of the underlying metameres. This analysis of primary growth using the metamere dimension and foliarization or axialization concepts is discussed on the basis of recent hypotheses related to the evolution of the physiologic function of branches during their setting in place. Key words: primary growth, preformation, neoformation, rhythmic growth, Malus ×domestica.
The effects of ultraviolet-B radiation and carbon dioxide on growth and photosynthesis of tomato
Authors: Hao Xiuming , Hale Beverley A. , Ormrod Douglas P.
Published: April 2011

Tomato (Lycopersicon esculentum Mill.) plants were exposed, in controlled environments with 2.7 kJ/(m2 ∙ day) background ultraviolet-B (UV-B) radiation from fluorescent and incandescent lamps, to ambient (380 μL ∙ L−1) or elevated (600 μL−1) CO2 combined with a total of 7.2 or 13.1 kJ/(m2 ∙ day) UV-B radiation to determine effects on growth and photosynthesis. Ten consecutive days of exposure to the higher level of UV-B significantly reduced total and stem dry weight, leaf area, and plant height compared with the lower level. Only leaf area and plant height were significantly reduced after 19 consecutive days of exposure. To investigate whether plants recover from UV-B damage, the UV-B exposures were halted for 3 days after 19 days of UV-B exposure and then restarted for a further 2 days. The largest reduction in plant growth was found after 3 days with no UV-B followed by 2 days of the higher level of UV-B. Plants did not recover from UV-B damage during the 3 days with background UV-B. Significant CO2xUV-B interactions were detected on stem dry weight after 10 consecutive days of the higher level of UV-B and on total dry weight, leaf dry weight, stem dry weight, and plant height after 3 days with no UV-B followed by 2 days of the higher level of UV-B. The higher dose of enhanced UV-B resulted in more severe damage at 600 μL ∙ L−1 CO2, than at ambient CO2. The higher level of UV-B did not affect the leaf net photosynthesis rate on a leaf area basis, although this UV-B level may have inhibited tomato growth through reducing the photosynthetic area. UV-absorbing compounds in leaves in the highest UV-B radiation level for 19 days were greater than for leaves with the lower dose. These UV-absorbing compounds in the higher UV-B dose diminished more than in the lower dose plants during the 3 days without UV-B. The UV-absorbing compounds maintained by plants exposed to the highest level of UV-B radiation may have protected plants from UV-B damage, particularly between 10 and 19 consecutive days of exposure. Key words: CO2, growth, Lycopersicon esculentum Mill., photosynthesis, tomato, ultraviolet-B radiation (UV-B), UV-absorbing compounds.
The effect of chelating agents on the later break yields of Agaricus bisporus
Authors: Beyer David M.
Published: April 2011

It has been hypothesized that substances that accumulate during the mushroom cropping period are responsible for decreased yields as a mushroom crop ages. The objective of this study was to determine whether chelators added to compost substrate at spawning would affect the later break yield of Agaricus bisporus. Different types of chelators were used to determine if specific ions were involved. Supplemented compost receiving hypnum peat, IR120 (sodium saturated) cation exchange resin, ethyleneglycol tetra-acetic, and citric acid significantly increased later break yield. However, IR120 (hydrogen saturated) cation exchange resin, ethylenediamine tetra-acetic and sphagnum peat moss added to supplemented compost at spawning did not significantly increase yield in later breaks. These results suggest the accumulation of calcium or another cation may inhibit later break yields. Key words: Agaricus bisporus, hypnum peat, ion exchange resins, chelation, citric acid.
Viability and abundance of seeds of submerged macrophytes in the sediment of disturbed and reference shoreline marshes in Lake Ontario
Authors: Westcott Kim , Whillans Thomas H. , Fox Michael G.
Published: April 2011

The seed banks of six Lake Ontario shoreline marshes were investigated to assess the potential for natural regeneration of sparse submerged macrophyte populations in marshes subjected to anthropogenic disturbance. Twenty-six core samples were taken in each of three disturbed marshes with sparse submerged vegetation, and the number of seeds was compared with samples from three reference marshes containing abundant submerged vegetation. Six cores from each of six marshes were examined to determine whether there was a difference between disturbed and reference marshes in seed density or seed distribution, and germination assays were used to assess differences in seed viability. Seeds of five submerged macrophyte taxa were identified in substrate samples of the six marshes. Mean seed density was significantly higher in the three reference marshes (4082 – 47 623 seeds/m2) than in the three disturbed marshes (0–2041 seeds/m2). The density of seedlings of submerged macrophytes germinating in reference marsh samples ranged from 333 to 2406 seedlings/m2, whereas no seedlings germinated from disturbed marsh samples. The deeper sediments (7–14 cm sediment depth) in the reference marshes had comparable seed densities to those in the shallower sediments, whereas seeds were found in only the deeper sediments of the disturbed marshes. These data suggest that regeneration from buried seeds is unlikely in the disturbed marshes, even if improvements occur in the environmental conditions that have historically inhibited the growth of submerged macrophytes. Key words: submerged macrophytes, anthropogenic disturbance, Lake Ontario, seed banks, natural regeneration.