bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental morphology of stem galls of Diplolepis nodulosa (Hymenoptera: Cynipidae) and those modified by the inquiline Periclistus pirata (Hymenoptera: Cynipidae) on Rosa blanda (Rosaceae)
Authors: Brooks Scott E , Shorthouse Joseph D
Published: April 2011

Diplolepis nodulosa (Beutenmüller) induces small, single-chambered, prosoplasmic galls in stems of Rosa blanda Ait. Gall initiation begins when adult females deposit a single egg into the procambium of R. blanda buds. Pith cells at the distal pole of the egg lyse forming a chamber into which the hatching larva enters. Cells lining the chamber differentiate into nutritive cells, which serve as the larval food. Gall growth is characterized by the proliferation of parenchymatous nutritive cells causing gall enlargement. A separate gall vasculature does not form, but instead, gall tissues are irrigated by the existing stem vasculature. Maturation begins when gall tissues cease proliferating and differentiate into distinct layers concentrically arranged around the larval chamber. The innermost layer is composed of cytoplasmically dense nutritive tissue, followed by parenchymatous nutritive tissue, sclerenchyma, cortex, and epidermis. Parenchymatous nutritive tissue differentiates into nutritive tissue and is consumed by the larva. Galls of D. nodulosa are susceptible to anatomical modification by the phytophagous inquiline Periclistus pirata (Osten Sacken). Galls attacked by P. pirata become enlarged and multichambered, with little resemblance to inducer-inhabited galls. Periclistus pirata kill the larva of D. nodulosa at oviposition and deposit several eggs per host gall. Inquiline-occupied galls may contain the eggs of several females. Nutritive tissue induced by D. nodulosa disintegrates. Growth of attacked galls occurs prior to hatching of P. pirata eggs. At egg hatch, the gall appears as an enlarged hollow sphere and larvae disperse over the chamber surface and feed on parenchymatous tissue. Feeding induces tissue proliferation, which surrounds each larva within its own chamber. As galls mature, cells surrounding each larval chamber lignify forming a sclerenchyma sheath. Cells inside the sclerenchyma sheath differentiate into nutritive cells and are consumed by the inquiline larvae.Key words: Rosa, Cynipidae, gall, developmental morphology, inquiline.
Effect of pollen age on fruit set, fruit weight, and seed set in three orchid species
Authors: Proctor Heather C
Published: April 2011

The length of time that pollen remains viable after being removed from the anther may be subject to species-specific selection pressures, e.g., when the average transit time between anther and stigma is long, long-lived pollen may be favoured. Flowering plants that provide no reward to pollinators are predicted to have relatively long-lived pollen, because pollinators are less likely to immediately revisit flowers of a nonrewarding species. I studied the effect of pollen age on fertilization success in three species of orchids that provide little or no reward. Pollen was aged 0, 1, 2, 4, or 8 days outside of the anther and then placed on the stigmas of conspecific flowers. I collected and weighed all resultant fruits and used a subsampling technique to determine the number of embryonated seeds per fruit and the percentage of all seeds that had embryos. There was no evidence that pollen age affected fruit set, fruit weight, embryonated-seed number, or percentage of embryonated seeds in two species (Calopogon tuberosus (Linn.) Britton and Pogonia ophioglossoides (Linn.) Ker.). In the third, Cypripedium reginae Walt., 8-day-old pollen produced significantly lighter fruits with fewer embryonated seeds; however, the percentage of embryonated seeds was not affected. Although the pollen of these nonrewarding orchids appears to have an impressive life-span, it is difficult to make comparisons with other species because most previous studies have relied on laboratory tests of viability that appear to have little relation to performance of pollen in the field.Key words: pollen longevity, Orchidaceae, reproductive success.
A rapid method for the assessment of the macromycota. The fungal community of an evergreen cloud forest as an example
Authors: Guevara R , Dirzo R
Published: April 2011

The macromycota of an evergreen cloud forest was described using a simple method, intended to minimize taxonomic work but still provide an accurate account of diversity. The method showed that the fungal community in the area is spatially structured and that area sampled limited the recording of fungal richness in this study. Parameters derived from the Clench equation suggest that an area of 1 ha will maximize the proportion of recorded taxa and minimize sampling effort.Key words: fungal diversity, macrofungal communities, tropical mycoecology, El Triunfo.
Production of green haploid durum wheat plants by pollination of wheat with maize
Authors: Saïdi Najia , Chlyah Omar , Chlyah Hassan
Published: April 2011

Eight genotypes of Triticum turgidum L. ssp. durum (2n = 4x = 28) were pollinated by three varieties of maize (Zea mays L.) to obtain green haploid durum wheat plants. After pollination, plants were cut and maintained in a nutrient solution until the ovary developed, and the embryo was rescued through in vitro culture. The influence of both the wheat and the maize genotypes on ovary development and embryo and green haploid plant formation was apparent. Ovary development and embryo formation were observed in all wheat genotypes with at least one maize variety. Green plants were obtained from six of the eight cultivars tested. Sixty doubled haploid green plants were recovered after colchicine treatment.Key words: Triticum turgidum ssp. durum, Zea mays, intergeneric hybridization, embryo rescue, haploid green plants.
Plant biology and food science in Canada: a vision for the future
Authors: Layzell David B , Brisson Normand , Devine Malcolm D , Moloney Maurice M , Taylor Gregory J , Timmer Victor , Yada Rickey Y , Wood Kathryn
Published: April 2011

The Natural Sciences and Engineering Research Council of Canada (NSERC) recently announced a plan to undertake a "reallocations exercise" designed to provide support for new initiatives and emerging fields of research in a period of fiscal restraint. NSERC's Grant Selection Committees (GSC) were instructed to establish committees charged with preparing reports that respond to the question "Why is it important for Canada that your research community should receive some of the funds available for reallocation?" The Plant Biology and Food Science Grant Selection Committee (GSC03) responded by striking a committee representing the breadth of research it supports. Extensive input was obtained from the scientific community through a web site and electronic discussion group. A discussion document was then prepared and distributed to 34 "consultants" representing NSERC-funded researchers and leaders in the agricultural, food, and forest industries. After refining the report, a second draft was circulated to more than 90 scientists for further review. This process provided us with a collective "vision" of our discipline that focuses on the importance of fundamental research, guided by excellence, innovation through multidisciplinary approaches, international leadership potential, and relevance to Canada and Canadians. To achieve this vision, NSERC must introduce a strategy to attract, train, and retain our best young minds, establish a broad, realistic funding base, and create opportunities for more interaction among disciplines. Six specific recommendations were put forward to achieve these goals with a total request for $15.3 million in reallocated and new money. If funded, this initiative will provide GSC03 researchers with the support required to generate the ideas, communicate the insights, develop the skills, and educate the personnel that will be essential for Canada's participation in the biotechnology revolution that is transforming global agriculture, food, and forest industries. Moreover, fundamental knowledge of the interaction between plants and their environment will also help Canada play a leading role in the effective, responsible stewardship of planetary resources in the 21st century.Key words: Natural Sciences and Engineering Research Council of Canada, reallocations exercise, plant biology, food science, biotechnology, fundamental research.
Remnant seed banks and vegetation as predictors of restored marsh vegetation
Authors: Brown Stephen C
Published: April 2011

Selection of sites for wetland restoration requires analysis of probable success at recreating diverse natural vegetation. We studied the seed banks and the remnant vegetation at restoration sites to determine their degree of similarity to the vegetation that developed following restoration of wetland hydrology. The study sites had been used for forage crops and pasture following long-term drainage. The seed bank was a very poor predictor of plant species abundances following restoration. Similarity between remnant vegetation and restored vegetation was consistently higher than similarity values using seed banks at both restored and natural wetlands. Our results suggest that seed-bank analysis is an inefficient technique for predicting restored vegetation in sites with prolonged disturbance, and that analysis of remnant vegetation on the sites is probably more useful. However, results would probably differ at sites with tile drainage that have limited remnant vegetation or created wetlands with bare soil where seed germination would play a greater role in revegetation. In addition, seed-bank studies are important to determine if aggressive invasive species are present at potential restoration sites.Key words: seed banks, wetlands, restoration, marshes, vegetation.
A new approach to the study of apical meristem development using laser scanning confocal microscopy
Authors: Lemon Gordon D , Posluszny Usher
Published: April 2011

Epi-illumination light microscopy and scanning electron microscopy have been standard techniques for developmental studies of shoot apices. Recently, laser scanning confocal microscopy has gained popularity as a tool for biological imaging. We have adapted laser scanning confocal microscopy to study development in whole shoot apices. It was tested on angiosperm and fern apices using three fluorescent dyes; acriflavine, safranin O, and acid fuchsin, and compared with epi-illumination light microscopy and scanning electron microscopy. In all cases, acid fuchsin proved to be the best fluorochrome for examining shoot apices; having a high affinity for cell walls and nuclear material. The images produced with laser scanning confocal microscopy were sharper and clearer than images generated with epi-illumination light microscopy and scanning electron microscopy. Laser scanning confocal microscopy allows one to map patterns of cell division on the surface of an apical meristem, which is extremely difficult using other techniques such as scanning electron microscopy or epi-illumination light microscopy. Since the laser scanning light microscope records images digitally a method for digital plate production is described. Our methods can easily be applied to study the development of other plant structures on a cellular level such as root apical meristems, floral meristems, stomata, or trichomes, and reproductive organs in lower plants.Key words: confocal microscopy, apical meristem, development, fluorochrome, cytokinesis.
Hétérogénéité d'une lande haute à Ulex europaeus en relation avec la propagation du feu (Bretagne, France)
Authors: Hely Christelle , Forgeard Françoise
Published: April 2011

This study analyzes plant material in a high Ulex europaeus heath to provide information on the partitioning of this ecosystem for fire propagation models. The aboveground biomass, followed for 15 months, has a spatially heterogeneous distribution that is a result of the layered pattern of the various branches. This pattern creates an internal moisture gradient that decreases from the apex to the base of the plant. This gradient also varies according to the species phenology. New, green branches with a high moisture content are at the top of the plant (upper strata), whereas woody branches with a lower moisture content are found near the ground (lower strata). Dry branches and spines, which produce most of the litter, are homogeneously distributed throughout the plant. Temporally, the layered pattern is homogeneous through the year and thus creates a constant fire risk. Soil organic horizons are temporally, spatially, and compositionally heterogeneous. The L layer is always two to three times thinner and drier than the duff layer (F+H). The total depth, weight, and moisture content of the organic horizons vary considerably across both the plot and square metre scales. The distance from a plant has a significant influence on the depth distribution of the soil organic horizons. Fuel distribution on both the soil surface and the plant must be considered to understand fire behaviour in this ecosystem.Key words: architecture, biomass, fire, fuel, humus, moisture content.
Internal C:N balance and biomass partitioning ofCarex rostratagrown at three levels of nitrogen supply
Authors: Saarinen Timo
Published: April 2011

The long-term effects of high nitrogen supply on the growth and partitioning of biomass in a common sedge species, Carex rostrata Stokes, were studied in a greenhouse experiment. Special attention was paid to free amino acids and soluble sugars, representing biochemically available fractions of nitrogen and carbon, respectively, in the tissues of Carex. Plants were grown in peat in buckets, and nitrogen was added as ammonium nitrate (2, 5, and 10 g N m-2year-1) five times during two growing seasons. Changes in biomass allocation patterns became evident towards the end of the second growing season. The biomass of shoots was highest in the high-N treatment, resulting in a high ratio of aboveground to belowground biomass. The high biomass of shoots was due to both the high density of current-year shoots and later senescence in the high-N treatment. No differences were observed in the belowground biomasses. Changes in allocation patterns were accompanied by changes in the soluble fractions of carbon and nitrogen. The concentration of free amino acids (FAA) was significantly higher (both shoots and roots) and the concentration of total nonstructural carbohydrates (TNC) lower (roots only) in the high-N treatment. The concentration of total nitrogen also increased with increasing supply of nitrogen. The results indicate that a high long-term supply of nitrogen may shift the internal carbon to nitrogen balance of Carex towards higher availability of nitrogen. Compared with the carbon to nitrogen ratio, the TNC:FAA ratio seems to be a better indicator of the internal carbon to nitrogen balance. A low TNC:FAA ratio may enhance the allocation of biomass to shoots and also increase the density of shoots.Key words: amino acids, biomass partitioning, carbon, Carex, nitrogen, sugars.
Multiple independent losses of the plastid rpoC1 intron in Medicago (Fabaceae) as inferred from phylogenetic analyses of nuclear ribosomal DNA internal transcribed spacer sequences
Authors: Downie Stephen R , Katz-Downie Deborah S , Rogers Erica J , Zujewski Heidi L , Small Ernest
Published: April 2011

A previous polymerase chain reaction based survey for the occurrence of the intron in chloroplast gene rpoC1 revealed its absence in one of the eight species of Medicago (Fabaceae; Trifolieae) examined. We extend the survey of Medicago to include 65 of the 86 species, representing all 12 sections and seven of the eight subsections recognized in the most recent comprehensive treatment of the genus. Our results indicate that 17 species from five sections lack the intron and that three of these sections are heterogeneous with regard to intron content. DNA sequencing across the rpoC1 intron-exon boundary in three of these species reveals the precise excision of the intron from the gene. Phylogenies derived from nuclear ribosomal DNA internal transcribed spacer sequences, estimated using maximum parsimony and maximum likelihood methods, suggest that most of the previously recognized sections in Medicago are not monophyletic as currently circumscribed. Furthermore, these results suggest that the rpoC1 intron has been lost independently a minimum of three times during the evolution of the group. The occurrence of multiple independent intron losses severely reduces the utility of this character as a phylogenetic marker in Medicago.Key words: Medicago, Fabaceae, chloroplast DNA, rpoC1 intron, nuclear ribosomal DNA internal transcribed spacer (ITS) sequences.
Microbial processes and fungal community structure in soils from clear-cut and unharvested areas of two mixedwood forests
Authors: Houston APC , Visser S , Lautenschlager R A
Published: April 2011

Decomposer fungi and microbial processes were examined in harvested and adjacent unharvested areas of two mixedwood forests in northwestern Ontario. Seven to 9 years following harvesting, organic and mineral soil from treated and control areas was sampled with the objective of examining the impact of clear-cutting and site preparation on soil basal respiration, microbial biomass carbon (C), metabolic quotients (qCO2), microbial C to organic C ratios (Cmic:Corg), nitrogen mineralization, and fungal community structure. Relative sensitivity of fungal community indices at species and genus levels was also examined. Soil microbial processes and fungal community structure were similar in harvested and unharvested stands. Although reductions were not significant, basal respiration, microbial biomass C, qCO2, Cmic:Corg, and nitrogen mineralization tended to be lower in organic soil from the harvested sites than the unharvested sites, with the exception of qCO2. Fungal community structure indicated by rank abundance curves and indices of fungal richness, diversity, evenness, and dominance was similar in harvested and unharvested soil. When comparing organic and mineral soil layers, fungal richness, diversity, and community composition corresponded more closely in the harvested sites than unharvested sites. The isolation frequencies of all frequently found fungal species were equivalent in harvested and unharvested soil. In this study, identifying fungi to the genus level instead of the species level did not alter any major conclusions.Key words: harvesting, fungal community, microbial processes.
Chrysophycean stomatocyst flora from south-central Ontario lakes
Authors: Wilkinson Anna N , Smol J P
Published: April 2011

Chrysophycean stomatocyst morphotypes were identified and enumerated from the sediments of 55 Muskoka-Haliburton south-central Ontario lakes. Principal components analysis (PCA) and TWINSPAN cluster analysis showed that the distribution of cyst assemblages was most closely related to lake water pH. Cyst abundance varied with lake trophic status, decreasing in highly productive lakes. The diversity of the observed cyst assemblages was similar to that seen in other stomatocyst studies from temperate regions, with a total of 246 morphotypes noted. The Muskoka-Haliburton cyst flora contained a high proportion (22.8%) of as yet undescribed morphotypes and an abundance of cysts ornamented with circuli and small ridges. Fifty-six previously unidentified morphotypes were observed, 29 of which were studied in detail using scanning electron microscopy, and described using International Statospore Working Group guidelines. Six variants of common morphotypes, characterized by the presence of a siliceous envelope, are also described. Twelve new distinct morphotypes observed only using light microscopy are documented as unidentified forms.Key words: Chrysophyceae, stomatocyst, taxonomy, Muskoka-Haliburton, Ontario, lakes, paleolimnology.
Modalités d'allongement et morphologie des pousses annuelles chez le noyer commun, Juglans regia L. 'Lara' (Juglandaceae)
Authors: Sabatier Sylvie , Barthélémy Daniel , Ducousso Isabelle , Germain Éric
Published: April 2011

Shoot extension during a growth season has been investigated in three morphological types of floriferous annual shoots (monocyclic with or without a small axis with immediate development and bicyclic) on four types of parental branches within 4-year-old Juglans regia L. 'Lara' growing in the south-west of France. The morphological type of parental branches has an influence on the time of inception of monocyclic shoot extension. No correlation has been found between the parental shoot length and monocyclic shoot length, while a positive correlation has been found between parental shoot length and bicyclic shoot length. Bicyclic annual shoots expand during two successive flushes : in spring and summer, respectively. The intra-annual resting phase results in the presence of a series of cataphylls in the median part of the shoots. Spring shoots and summer shoots may be distinguished by variations in form and in number of foliar organs. Annual shoots exhibiting an acrotonic axis with immediate development or a summer shoot generally possess greater extension periods and lengths of spring shoots than the unbranched ones.Key words: Juglans regia 'Lara', persian walnut, shoot extension, primary growth, morphology, annual shoot.
Comparative study of dissolved inorganic carbon utilization and photosynthetic responses inNannochloris(Chlorophyceae) andNannochloropsis(Eustigmatophyceae) species
Authors: Huertas I Emma , Lubián Luis M
Published: April 2011

Four species of marine microalgae with similar morphology and life cycle, namely Nannochloris atomus Butcher, Nannochloris maculata Butcher, Nannochloropsis gaditana Lubian, and Nannochloropsis oculata (Droop) Hibberd, have been examined with respect to their affinity for different sources of dissolved inorganic carbon. External carbonic anhydrase activity was not found in any of these species, but the cell affinity for dissolved inorganic carbon (DIC) in Nannochloris species was affected by the inhibitor acetazolamide at a concentration of 400 µM. Measurement of photosynthetic rates and CO2compensation points at different pH values showed that the Nannochloris species had a greater capacity for CO2rather than HCO3-utilization. In contrast, the observed rates of photosynthetic oxygen evolution in Nannochloropsis species were greater than could be accounted for by the theoretical rate of CO2supply from the spontaneous dehydration of bicarbonate in the external medium. This indicates that these algae were able to transport bicarbonate across the plasmalemma. Furthermore, the K0.5(DIC) value at acidic pH showed that Nannochloropsis oculata could also use CO2as an exogenous carbon source for photosynthesis. Although the species of marine phytoplankton used in this study possess similar morphological characteristics and life cycle, there exist many differences in the mode of inorganic carbon utilization between these microalgae.Key words: Nannochloris, Nannochloropsis, inorganic carbon utilization, bicarbonate transport, CO2compensation point, photosynthesis.
Isolation and characterization of high-CO2 requiring mutants from Chlamydomonas reinhardtii by gene tagging
Authors: Fukuzawa Hideya , Ishizaki Kimitsune , Miura Kenji , Matsueda Shoji , Ino-ue Tatsuya , Kucho Ken-ichi , Ohyama Kanji
Published: April 2011

To isolate genes essential to the carbon concentrating mechanism and the CO2-signal transduction mechanisms, seven high-CO2 requiring mutants were isolated from Chlamydomonas reinhardtii by the insertion of nit1 gene encoding nitrate reductase. These mutants were grouped into two classes. Class I contains mutants that show a severe CO2-requiring phenotype (C1 and C3). Class II includes those with a moderate CO2-requiring phenotype (C2, C5, C7, C15, and C16). One of the class II mutants, C5, appeared to be defective in the utilization of intracellularly accumulated inorganic carbon. On the other hand, the mutant C16 appeared to be defective not only in the uptake of carbon but also in the induction of the periplasmic carbonic anhydrase gene, CAH1, as well as in the development of pyrenoid structure under low-CO2 conditions. These mutations in C5 and C16 mutants appeared to be caused by single insertional events of the introduced DNA fragment into the genomic DNA, suggesting that their corresponding genes could be tagged using the nit1 gene.Key words: carbon concentrating mechanism, carbonic anhydrase, gene tagging, insertional mutagenesis, nitrate reductase.
The functioning of the CO2 concentrating mechanism in several cyanobacterial strains: a review of general physiological characteristics, genes, proteins, and recent advances
Authors: Price G Dean , Sültemeyer Dieter , Klughammer Barbara , Ludwig Martha , Badger Murray R
Published: April 2011

Cyanobacteria (blue-green algae) possess an environmental adaptation for survival at low CO2 concentrations. The adaptation is known as a CO2 concentrating mechanism (CCM), and it functions to actively transport and accumulate inorganic carbon ( and CO2; Ci) within the cell and then uses this Ci pool to provide elevated CO2 concentrations around the primary CO2-fixing enzyme, ribulose bisphosphate carboxylase-oxygenase (Rubisco). It appears that the site of CO2 elevation is within a unique microcompartment known as the carboxysome, which is a proteinaceous polyhedral body that contains most, if not all, of the Rubisco within the cell. This review covers comparative aspects of physiology, genetics, and proteins involved in the cyanobacterial CCM with particular focus on recent advances. This review highlights information on three strains of unicellular cyanobacteria, namely Synechocystis PCC6803 (freshwater strain; for which a full genome database is now available), Synechococcus PCC7002 (coastal marine strain) and Synechococcus PCC7942 (freshwater strain). Genes that may be involved in the CCM, directly or indirectly, are summarized in tabular form. For Synechocystis PCC6803, the number of genes related to CCM activity is now in excess of 50; however, 19 of these components have the potential to code for several distinct type-1, NADH dehydrogenase complexes.Key words: cyanobacteria, CO2 concentrating mechanism, carboxysomes, genes, photosynthesis, transporters.
Mechanisms of carbon acquisition for endosymbiont photosynthesis in Anthozoa
Authors: Allemand Denis , Furla Paola , Bénazet-Tambutté Sylvie
Published: April 2011

In contrast to free-living photoautotrophs, endosymbiontic dinoflagellates of the genus Symbiodinium must absorb their inorganic carbon from the cytoplasm of their host anthozoan cell rather then from seawater. The purpose of this paper is to review the present knowledge on the source of dissolved inorganic carbon supply for endosymbiont photosynthesis and the transport mechanisms involved. Symbiodinium spp., generally known as zooxanthellae, live within the endodermal cells of their hosts, corals and sea anemones. They are separated from the surrounding seawater by the host tissues (oral ectodermal cell layer, collagenous basal membrane, endodermal cell, and perisymbiotic vesicles). The symbiotic association is therefore faced with the problem of delivering dissolved inorganic carbon to an endodermal site of consumption from an, essentially, ectodermal site of availability. Studies using original methods demonstrated that neither the internal medium (coelenteric fluid) nor paracellular diffusion could supply enough dissolved inorganic carbon for endosymbiont photosynthesis. A transepithelial active mechanism must be present in the host tissues to maintain the photosynthetic rate under saturating irradiance. A pharmacological approach led to propose a working model of dissolved inorganic carbon transport from seawater to zooxanthellae. This vectorial transport generates a pH gradient across the epithelium. The role of this gradient as well as the physiological adaptation of Symbiodinium spp. to symbiotic life are discussed.Key words: carbon concentrating mechanism, anthozoan, dinoflagellates, anion transport, symbiosis, transepithelial transport.
Two new hyphomycetes from rainforests of Cuba
Authors: Castañeda Ruíz R F , Guarro J
Published: April 2011

Two new dematiaceous hyphomycetes, Arachnophora hughesii R.F. Castañeda et Guarro found on decaying pods of Samanea samans and Camposporidium hughesii R.F. Castañeda et Guarro found on decaying bark submerged in stream, both in a tropical rainforest are described and illustrated. The former is distinguished by staurosporous conidia composed of a obconical, pale olivaceous, fimbriate basal cell, 1-2 subdoliiform, hemisphaerical to irregular, olivaceous central cells, and 2-5 tapered, horn-like or conical, 0-1 septate, pale, olivaceous arms. A Selenosporella-like synanamorph is present at the apex of the arms. Conidia fusiform to cylindrical, 10-15 euseptate, brown, verrucose, with several filiform, hyaline, branched or unbranched cellular appendages that arise from the last two subapical cells at right angles to the axis of the conidium characterized the latter. Notes on closely related species are given.Key words: Arachnophora hughesii, Camposporidium hughesii, hyphomycetes, mitosporic fungi, Cuba.
Diplococcium hughesii sp.nov. with a Selenosporella synanamorph
Authors: Wang CJK , Sutton B C
Published: April 2011

A dematiaceous hyphomycete, Diplococcium hughesii C.J.K. Wang & B. Sutton sp.nov., with a Selenosporella synanamorph, is described. It is characterized by dark, branched conidiophores bearing integrated, terminal, and intercalary conidiogenous cells. Pores are visible on the wall of the conidiogenous cells after conidium secession. Catenate conidia are acropleurogenous, subglobose to oblong, and 0-septate.Key words: hyphomycetes, dematiaceous genera, lignicolous, pleomorphic fungi.
New species of the aeroaquatic hyphomycete genus Clathrosporium and their relationship with Strumella Sacc.
Authors: Hennebert Grégoire Laurent
Published: April 2011

Clathrosporium Nawawi & Kuthubutheen is found to be synonymous with Strumella Sacc. (lectotypified by Strumella olivatra (Sacc.) Sacc.), a later illegitimate homonym of Strumella Fr. Consequently, Strumella olivatra is redisposed in Clathrosporium, alongside the type species Clathrosporium intricatum Nawawi & Kuthubutheen. Two new species, Clathrosporium delicatum Hennebert sp.nov. and Clathrosporium compactum Hennebert n.sp., are described and illustrated. These hyphomycetes are aeroaquatic, growing on periodically submerged plant material, leaves, and rotten wood. They produce pigmented, multicellular propagules comprising coiled, branching hyphae that disarticulate into arthroconidia when mature.Key words: aeroaquatic, hyphomycete, Clathrosporium olivatra, Clathrosporium vinosa, Clathrosporium delicatula, Clathrosporium compacta, Strumella, Spirosphaera, taxonomy.
Occurrence of the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana in soils from temperate and near-northern habitats
Authors: Bidochka Michael J , Kasperski June E , Wild Geoffrey AM
Published: April 2011

The occurrence of deuteromycetous entomopathogenic fungi was examined in 266 soil samples representing 86 locations across temperate and near northern habitats in Ontario, Canada. Entomopathogenic fungi were isolated by baiting the soil with waxworm larvae, Galleria mellonella L., and incubating at 8, 15, or 25°C. Entomopathogenic fungi were isolated from 91% of the locations sampled across Ontario. The most abundant species were Metarhizium anisopliae (Metschn.) Sorok. (357 isolates) and Beauveria bassiana (Bals.) Vuill. (187 isolates). Thirteen isolates of Paecilomyces spp. were also found. Beauveria bassiana was isolated more frequently in soils from near northern locations, relative to M. anisopliae. Beauveria bassiana was isolated more frequently from larvae baited in soils incubated at 8 and 15°C, while M. anisopliae was isolated most frequently at 25°C. Thus, B. bassiana is more psychrophilic than M. anisopliae. From 47 of the locations in a temperate area (southern Ontario and the Kawartha Lakes region), two sites, one from an agricultural habitat and one from a natural habitat, were sampled within 1 km of each other. In these locations, B. bassiana was predominantly recovered more often from soils of natural habitats, while M. anisopliae was recovered more often in agricultural habitats. The occurrence of M. anisopliae and B. bassiana was not related to soil type or pH.Key words: Metarhizium, Beauveria, entomopathogenic fungi, fungal population biology, soil ecology.
Le port autoportant des lianes tropicales : une synthèse des stratégies de croissance
Authors: Caballé Guy
Published: April 2011

Les lianes sont des végétaux ligneux grimpants et non autoportants. Mais les lianes sont capables d'autoportance dans les trois situations suivantes : (i) sous conditions de milieu limitantes (lumineuses surtout); (ii) en phase juvénile du développement morphogénétique; (iii) lors des épisodes d'expansion, de renouvellement ou de restauration morphologique. L'autoportance peut concerner tout ou partie du système aérien, l'ensemble des tiges ou quelques tiges seulement. En général, lorsque l'autoportance et la non autoportance affectent plusieurs tiges d'un même système aérien, ces dernières s'opposent aussi par les fonctions biologiques qu'elles exerçent : asexuée et sexuée, sans accrochage et avec accrochage, établissement et exploration. Lorsque l'ensemble du système aérien est autoportant (situations (i) et (ii)), la liane a un mode de vie comparable à celui d'un petit arbre ou d'un arbuste. Une synthèse des données d'architecture anatomique et de stratégie de croissance est présentée. Elle porte sur quelque 40 sites forestiers d'Afrique, d'Amérique et de l'Océan Indien et plus de 400 espèces d'angiospermes tropicales lianescentes. Le polymorphisme des lianes, révélateur des contrastes de vie en milieu tropical, trouve son expression la plus accomplie dans l'opposition des deux modes de vie, autoportant et non autoportant. Sur un plan évolutif, les lianes pourraient représenter une forme ligneuse originale qui aurait conservé ou acquis ces deux modes de vie. Les contraintes de l'environnement et (ou) du développement morphogénétique stimuleraient selon les cas l'organisation autoportante ou non.Mots clés : liane, autoportance, non autoportance, architecture anatomique, mode de vie, polymorphisme.
Physiological and biochemical responses of Sorghum vulgare plants to supplemental ultraviolet-B radiation
Authors: Ambasht Navin Kumar , Agrawal Madhoolika
Published: April 2011

Sorghum (Sorghum vulgare (Pers.) cv. MSH 51) plants were grown in the field under ambient and supplemental levels of ultraviolet-B radiation (UV-B; supplemental daily dose corresponding to a 20% reduction in the stratospheric ozone column). Gas exchange characteristics, biomass, and levels of photosynthetic pigments, flavonoids, catalase, peroxidase activity, and ascorbic acid were determined to evaluate the changes induced by enhanced levels of UV-B irradiation. Gas exchange analysis indicated that one of the reasons for the decline in photosynthesis is stomatal limitation. Enhanced UV-B also caused reductions in chlorophyll and carotenoid pigments after 60 days of exposure. Concentrations of UV-B absorbing pigments increased linearly with age. UV-B irradiation also increased phenolic compounds. Catalase activity decreased, while peroxidase activity increased in response to elevated UV-B. There was a decrease in total plant biomass and ascorbic acid content of plants exposed to UV-B. Thus, an enhanced level of UV-B irradiation over a long period has a cumulative unfavourable effect on a number of physiological and biochemical processes, leading to a reduction in dry matter production.Key words: UV-B radiation, Sorghum vulgare, photosynthesis, stomatal resistance, flavonoids, peroxidase.
The effect of an oak wilt epidemic on the genetic structure of a Texas live oak population
Authors: McDonald Bruce A , Bellamy Brenda K , Zhan Jiasui , Appel David N
Published: April 2011

Oak wilt is a fungal tree disease that has killed millions of live oaks (Quercus fusiformis Small) in the oak woodlands of central Texas. Allozymes were used to characterize the genetic structure of live oak populations prior to infection (pre-epidemic) and following passage of an epidemic wave (post-epidemic). Pre-epidemic trees (N = 112) were sampled along transects in front of an expanding disease front. Post-epidemic trees (N = 109) were survivors of an epidemic that swept through an area of approximately 28 ha over a period of 20 years. Significant differences in allele and genotype frequencies existed between pre- and post-epidemic populations. Gene diversity was lower for two of the four allozyme loci in the post-epidemic population. Departures from Hardy-Weinberg equilibria occurred for two loci and multilocus associations developed in the post-epidemic population. These results demonstrate that disease can have a significant impact on the genetic structure of a natural host population. We hypothesize that selection for increasing disease resistance was the dominant evolutionary force leading to genetic change in this plant pathosystem.Key words: host-pathogen interactions, population genetics, Ceratocystis fagacearum, coevolution.
Relationships between size, biomass allocation, reproduction, and survival in Triglochin palustris: implications for the effects of goose herbivory
Authors: Mulder Christa PH , Ruess R W
Published: April 2011

Triglochin palustris (arrowgrass) on the Yukon-Kuskokwim Delta reproduces primarily vegetatively, and is heavily grazed by geese. To link effects of herbivory on individuals to population-level effects, we examined relationships between plant size or biomass allocation and survival or reproduction by matching more than 400 individuals into groups and sequentially harvesting individuals from each group. We compared size and biomass allocation for nonreproductive plants and plants with either or both modes of reproduction in exclosed plots, and examined effects of clipping leaves or inflorescences in flowering and nonflowering plants. Survival and vegetative reproduction increased with plant size, particularly bulb size, but was unrelated to biomass allocation. Very small plants do not reproduce, very large plants produce both flowers and stolons, and intermediate sized plants produce either flowers or stolons. Inflorescences require greater biomass investment than stolons, resulting in decreased allocation to all vegetative plant parts except roots. Plants that produce flowers seldom regenerate overwintering bulbs on the parent plant, indicating a trade-off with survival. Geese may decrease flowering by reducing plant size and consuming inflorescences. Flowering plants have much higher rates of herbivory than other plants, suggesting that increased risk of herbivory results in low rates of flowering.Key words: Alaska, brant geese, sexual reproduction, subarctic salt marsh, vegetative reproduction.
The effects of collection date, IBA, plant gender, nutrient availability, and rooting volume on adventitious root and lateral shoot formation by Salix planifolia stem cuttings from the Ungava Bay area (Quebec, Canada)
Authors: Houle Gilles , Babeux Patrice
Published: April 2011

Salix planifolia Pursh ssp. planifolia is a shrub species presenting some potential for the restoration of disturbed sites in the Canadian Arctic and Subarctic. The performance of S. planifolia stem cuttings collected in the Kuujjuaq area, northern Quebec, was evaluated in relation to sampling period, plant gender, exogenous auxin and nutrient concentration, rooting duration, watering frequency, and soil volume. Cuttings collected in August, during the active growing season, did not perform as well as those collected in June, October, or February. The only performance variables influenced by plant gender were root number and shoot biomass, for which female cuttings were superior to males. Surprisingly, the application of indole-3-butyric acid inhibited adventitious root and lateral shoot number and biomass, particularly at the highest concentration (10 000 mg·L-1). Increased nutrient availability enhanced root, but not shoot, growth. The best performance was observed when cuttings were grown in a relatively large soil volume (200 mL), watered frequently (twice a day), and allowed a relatively long period to root (70 days).Key words: indole-3-butyric acid (IBA), nutritional status, plant gender, rooting of cuttings, Salix planifolia, sampling period.
A palynological investigation of true-moss (Bryidae) spores: morphology and occurrence in modern and late Quaternary lake sediments of Alaska
Authors: Brubaker L B , Anderson P M , Murray B M , Koon D
Published: April 2011

This study describes (i) spore morphology of 121 Alaskan species of true moss (Bryidae) and (ii) percentages of Bryidae and Sphagnum spores in mud-water interface samples from 46 Alaskan lakes and a late-Quaternary sediment core from Idavain Lake in southwestern Alaska. Bryidae spores were collected from herbarium specimens, prepared by standard palynological chemical treatment and described under light microscopy. An identification key based on spore shape, wall structure, and size recognized 11 major morphological groups. Although family, genus, or species identifications were not possible for most groups, spores of a few genera and species were distinctive. Bryidae spores occurred in 80% of the modern sediment samples, representing boreal forest and three areas of tundra (North Slope, Seward Peninsula, and southwestern Alaska). Bryidae and Sphagnum spore percentages showed greatest differences between the North Slope tundra and other vegetation types, whereas pollen percentages distinguished boreal forest from tundra regions as a group. Bryidae spores were present throughout the Idavain Lake record but were most common in late-glacial sediments. Variations in the abundance of Bryidae spores are consistent with or enhance paleoenvironmental interpretations based on pollen and other spore types.Key words: Bryidae, palynology, spores, Alaska, Quaternary, paleoenvironment.
Female gametophyte and embryo development of black spruce along a shore-hinterland climatic gradient of a recently created reservoir, northern Quebec
Authors: Sirois Luc , Bégin Yves , Parent Johanne
Published: April 2011

The development of female gametophytes and embryos in relation to cumulative growing degree-days was followed to see if the postulated cooling influence of the Robert-Bourassa reservoir (LG2, northern Quebec) slowed the reproductive process of black spruce (Picea mariana (Mill.) B.S.P.). During the 1996 growing season, three to five developing seed cones were harvested 11 times on nine trees distributed along a shore-hinterland gradient of the northern shore of the reservoir. The daily thermal sum (degree-days > 5°C) in the seed cone zone of the same trees was also monitored to describe the female gametophyte and embryo development of this species as a function of heat sum. The 23 developmental stages identified in this study confirm that the female gametophyte and embryo of P. mariana develop according to the same pattern exhibited by other Picea spp. These stages, although unequal in duration, succeeded each other according to a sigmoid function of the temperature sum. Direct temperature measurements taken 0, 25, and 100 m from the shore of the Robert-Bourassa reservoir suggest the interior trees experienced 107 more degree-days > 5°C than the shoreline trees during seed maturation. Although gametophyte development of the shoreline trees was delayed early in the growing season (Kruskall-Wallis, p = 0.05), this delay does not persist afterward. Despite the net cooling effect of the Robert-Bourassa reservoir, all studied trees achieved embryo maturation in 1996. During this growing season, the warmest since 1977, it took embryos 800-940 degree-days to mature. The shoreline trees reached this temperature threshold later than interior trees. It is suggested that the cooling effect of the Robert-Bourassa reservoir could contribute to the inhibition of embryo maturation in shoreline trees during growing seasons with less than 800 degree-days.Key words: black spruce, climate change, cone development, northern boreal forests, Picea mariana, seed maturation.
Cortical ontogeny in roots of the aquatic plant, Hydrocharis morsus-ranae L.
Authors: Seago, Jr. James L , Peterson Carol A , Enstone Daryl E
Published: April 2011

Tissues in adventitious roots of Hydrocharis morsus-ranae L. developed from a four-tiered apical meristem. A set of periclinal divisions in the outermost layer of the ground meristem produced a hypodermis, which was normally uniformly biseriate. Aerenchyma formed from the adjacent inner layer of the cortex by a series of cell divisions and cell lyses; three- to five-celled, radial aerenchyma strands formed by periclinal divisions in radial cell files 0.3-5 mm behind the apex. Intervening cells underwent anticlinal and periclinal divisions followed by cell lyses within 1 mm of the apex to produce air spaces. Aerenchyma formation in this species is unusual and presents a unique system suitable for a study of developmentally programmed cell death in parenchyma cells. The endodermis formed a complete Casparian band about 10 mm behind the root apex and did not develop further; it had neither suberin lamellae nor secondary walls. The hypodermis was parenchymatous and was without Casparian bands, suberin lamellae, and secondary walls. Following acid digestion, the wavy walls of the endodermis and the walls of the epidermis remained.Key words: aerenchyma, cell death, endodermis, Hydrocharis, hypodermis, root development.
Physical mapping of 45S rRNA genes in Cucumis species by fluorescence in situ hybridization
Authors: Chen Jin-Feng , Staub Jack E , Adelberg Jeffrey W , Jiang Jiming
Published: April 2011

The chromosomal locations of the genes coding for the 18S-5.8S-26S rRNA was investigated in Cucumis species using fluorescence in situ hybridization. Cucumber (Cucumis sativus L., 2n = 2x = 14) possesses four pairs of rDNA loci that were mapped to chromosomes 1C, 2C, 4C, and 7C. The distinctive hybridization sites of the 18S-5.8S-26S rRNA genes provide several useful cytogenetic markers for identification of chromosomes in C. sativus. The 18S-5.8S-26S rDNA genes have also been detected on two chromosome pairs, one major and one minor pair of loci, in melon (Cucumis melo L., 2n = 2x = 24) and on three pairs of Cucumis hystrix Chakr. chromosomes. The different number and pattern of rDNA sites is consistent with the hypothesis that considerable phylogenetic distance exists among these species.Key words: fluorescence in situ hybridization, 45S rRNA gene, cytogenetics, Cucumis sativus, Cucucmis melo, Cucumis hystrix.