bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution, production, and diversity of C3- and C4-dominated communities in a mixed prairie
Authors: Barnes Paul W. , Tieszen Larry L. , Ode David J.
Published: August 2008

The vegetation composition and standing crop of 44 stands, representing a diversity of topographic sites, were examined in a Northern Great Plains mixed prairie to determine the distribution, diversity, and relative production of different C3 and C4 dominated plant communities. Cluster analysis identified seven species groups at the 40% similarity level; these have been identified as seven community types: high prairie, midprairie, low prairie, meadow, depression, mud flats, and marsh. Environmental variables which showed the highest significant correlation with the three axes of a modified Bray and Curtis indirect ordination were soil moisture regime, soil potassium, and soil nitrate. Analysis of δ13C biomass values indicate that the greatest abundance (nearly 50%) of C4 biomass occurs in low prairie with roughly one-third of meadow and high prairie biomass contributed by C4 species. C4 biomass contribution appears greatest on soils relatively low to moderate in nitrate, potassium, phosphorous, and moisture, yet C4 species cooccur with C3 species where these resources are low. Both productivity and species diversity are related to topographic features but productivity does not appear to be functionally determined by the relative proportion or contribution of C4 taxa. The greatest number of C4 species occupy upland slopes and ridges and within these habitats C3 and C4 grasses may be distributed differently depending on slope exposure.
Anatomical features and silica depositional patterns in the rhizomes of the grasses Sorghastrum nutans and Phragmites australis
Authors: Sangster A. G.
Published: August 2008

Rhizomes of field-grown specimens of two grasses, Sorghastrum nutans (L.) Nash and Phragmites australis (Cav.) Trin., were prepared for anatomical study and silicon analysis using light microscopy, scanning electron microscopy, and energy dispersive X-ray microprobe analysis. Silicon deposition, as detected by the latter, was restricted in S. nutans essentially to four perivascular zones in a transect across the rhizome; two being associated with the outer vascular bundles and endodermal region of the cortex, and the other two zones with the sclerenchyma and central vascular bundles of the stele. No comparable silicon deposition was detected for P. australis, none being present above background levels both in transections and digested material of mature functional rhizomes. Contrasting aspects of silicon localization as well as differences in basic plan of rhizome anatomy exhibited by these two species are discussed in relation to differing habitat requirements and to previous root and rhizome studies.
The biology of the annual Salicornia europaea agg. at the limits of its range in Hudson Bay
Authors: Jefferies R. L. , Jensen A. , Bazely D.
Published: August 2008

The biology of a marginal population of the annual Salicornia europaea agg. has been examined at La Pérouse Bay, Manitoba, on the shores of Hudson Bay. Plants were confined to south-facing sites which became hypersaline in summer, but which were not covered by tides. The difference in temperature of surface sediments between south- and north-facing slopes was as much as 7 °C. Although most seedlings emerged in June, germination continued throughout the summer, but plants that appeared late in the season failed to set seed. Mortality of both seedlings and adult plants was low. Seeds or seedlings from a south-facing slope were transplanted during a 2-year period within the same site, into another south-facing site, to a north-facing site, and to an intertidal site. Germination either failed to occur or else was poor at the latter two sites. In addition, seed production of mature plants was low compared with that for individuals transplanted within south-facing sites. Additions of nitrogen to north-facing slopes increased overall seed output per plant, but the ratio of unripened to ripened seeds remained the same as that in plants from untreated plots. The results are discussed in relation to the ecology of marginal populations.
Genetic variation within and between populations of the asexual plant Puccinellia × phryganodes
Authors: Jefferies R. L. , Gottlieb L. D.
Published: August 2008

Puccinellia × phryganodes (Trin.) Scriber and Merr is widely distributed in Arctic salt marshes. In North America the species, which is capable of extensive clonal growth, appears to be a sterile triploid (2n = 21); seed set has never been observed. Consequently it was predicted that the level of genetic variation would be low, both within and between populations. Examination of electrophoretic mobilities of isozymes of 12 enzyme systems in plants from three widely separated populations in Arctic Canada indicated a high level of variability both within and between the populations. The unexpected discovery of significant amounts of genetic variability suggests that sexual processes occur in this species.
Acetylene reduction and hydrogen evolution by nitrogenase in a Rhizobium–legume symbiosis
Authors: Edie Scott A.
Published: August 2008

The relationship between acetylene reduction and hydrogen evolution in air was examined in peas (Pisum sativum L. cv. Alaska) inoculated with Rhizobium leguminosarum strain 3740, which lacked uptake hydrogenase activity (Hup−). In the absence of a system for recycling hydrogen, changes in the relative efficiency of N2 fixation (RE), which is defined as RE = 1 − (hydrogen evolved in air)/(acetylene reduced), presumably reflect an altered capacity of nitrogenase to allocate electrons between protons and N2. The RE of plants grown without combined nitrogen declined during the vegetative phase of growth and increased after flowering. Continuous high light or elevated CO2 conditions in the absence of nitrate maintained throughout ontogeny accentuated decreases in RE. When nitrate was present in the growth medium declines in RE during the vegetative phase were lessened. These results are consistent with the concept that the electron allocation coefficient of nitrogenase varies in the absence of uptake hydrogenase activity.
Temporal patterning of blooming phenology in Pedicularis on Mount Rainier
Authors: Adams Virginia Dale
Published: August 2008

The temporal patterning of flowering of five sympatric species of Pedicularis in a subalpine meadow is documented. Two species bloom early in the growing season, one is intermediate, and two flower toward the later part of the season. The differences between species are related to the range of blooming periods (in days), the number of inflorescences at maximum bloom, and the time of peak bloom. No significant variation in flowering pattern occurred during the years of observation (1977, 1978, and 1979). More than 93% of the time individual bumblebees continued to forage on the same Pedicularis species as was previously visited; yet when switches in the diet of the bees occurred, they were more likely to be to another species of Pedicularis. Although individuals of other genera were in bloom, the bees switched to the Pedicularis species most synchronous in time and space to the previously preferred Pedicularis species. Counts were made of the number of pollen grains per flower, the reward for foraging bees. The last species to flower had the greatest reward but also had the largest ratio of the number of pollen grains to the number of ovules as compared with the previously flowering Pedicularis species. These results suggest that pollinator sharing is an important evolutionary force but that the quantity of the pollen reward may be more related to the number of ovules.
Effects of surface amendation of two mine spoils in Alberta, Canada, on vesicular–arbuscular mycorrhizal development of slender wheatgrass: a 4-year study
Authors: Zak John C. , Parkinson Dennis
Published: August 2008

The effects of amendation of two mine spoils (oil sands tailings and a subalpine coal mine spoil) on the development of vesicular–arbuscular (VA) mycorrhizae with Agropyron trachycaulum were examined over 4 years. Each spoil was either amended with peat, fertilizer, or sewage sludge or left unamended. Plants were sampled in late August of the second and fourth growing season and the level of infection expressed as length of mycorrhizal root per 10 cm3 of spoil. Plants on the peat-amended oil sands spoil, as compared with the other treatments, had the highest rates of infection. Infection levels increased in the fertilized plots over the 4 years. Mycorrhizae were not detected in the sewage-amended plots until the 4th year. Infection levels from the amended subalpine spoil did not change significantly between the 2nd and 4th year. Mycorrhizal root lengths were highest in the peat-amended spoil as compared with the control and sewage-treated plots. Rates of infection in the fertilized spoil were not significantly different from the other treatments. The initial application of an amendment to a mine spoil may have significant long-term effects on the development of VA mycorrhizae and the success of a revegetation program. Changes in the mycorrhizal status of plants on these habitats may occur only slowly with time.
Pinus banksiana forests of the Fort Vermilion area, northern Alberta
Authors: Purchase John E. , Roi George H. La
Published: August 2008

Thirteen undisturbed Pinus banksiana Lamb. forests on Eutric Brunisols, derived from dune sands in the lower Peace River Valley, were analyzed quantitatively. Fort Vermilion has a dry, continental, subarctic macroclimate. Stands varied in age from 15 to 97 years, with tree volume increasing from 19 in younger to 193 m3 ha−1 in older stands. Cover of trees averaged 49%, shrubs 7%, dwarf shrubs 27%, forbs 6%, graminoids 1%, feather mosses 4%, caribou lichens 2%. Based on recurrently dominant species of well-developed vascular strata and growth-form guilds, a PINUS BANKSIANA/ROSA ACICULARIS/ARCTOSTAPHYLOS UVA-URSI – LATHYRUS OCHROLEUCUS community type is postulated for xeric sandhill habitats. This type is probably seral to a Picea glauca (Moench) Voss climax, but frequent fires prevent this. Plant succession during the sampled 80-year age interval is characterized by (i) increasing dwarf shrub, forb, and graminoid cover, (ii) stabilization of vascular species richness at ca. 35 species per stand, (iii) decline and stabilization of Simpson's dominance index, (iv) increasing Shannon–Weaver diversity, and (v) progressively gentler dominance–diversity slope angles. The niche preemption model (geometric series) of species structure fits younger and older better than middle-aged stands, based on goodness of fit of regression lines (r2) to dominance–diversity curves.
A comparative study of the changes of peroxidase patterns during wheat, rye, and triticale kernel maturation
Authors: Asíns M. J. , Benito C. , Vega M. Pérez de la
Published: August 2008

A comparative study on the electrophoretic patterns of embryo plus scutellum, endosperm, and internal and external coats of rye (Secale cereale L. and Secale vavilovii Grossh.), tetraploid wheat (Triticum turgidum L. durum), and hexaploid Triticale during kernel maturation has been carried out. Each kernel part of each species showed a characteristic pattern, and slow pattern changes from the beginning of the study (5 days after pollination) until kernels reached maturity (dry kernels) were observed. The triticale peroxidase patterns were very similar to tetraploid wheat patterns, and only few rye isozymes were clearly observed, probably due to overlapping with wheat isozymes. The possible influence of rye genome on the expression of wheat isozymes in triticale is also discussed.
Effects of sulfuric acid rain on decomposition rate and chemical element content of hardwood leaf litter
Authors: Lee Jeffrey J. , Weber David E.
Published: August 2008

Simulated sulfuric acid rain (pH 3.0, 3.5, or 4.0) or control rain (pH 5.6) was applied to decomposing leaf packs of 10 hardwood species. Changes in weight and chemical element concentrations were followed for 408 days. Leaf-pack weight decreased most rapidly under the intermediate acid treatments, especially at pH 3.5. The ratio of the decomposition rate of leaves at pH 3.5 to the decomposition rate of the control leaves varied from 1.10 for Quercus garryana to 12.57 for Quercus palustris. As expected, control decomposition rates tended to be higher for species with low C:N ratios and high base content. However, there was no apparent relationship between sulfuric acid rain effect on decomposition rate and initial chemical element content. The lack of a relationship to either S concentration or S:N ratio suggests that the sulfuric acid rain did not enhance decomposition by supplying S; however, the rain S was undoubtedly more available than organic S. For all treatments except pH 3.0, Mn concentrations tended to increase during decomposition; at pH 3.0, Mn concentrations increased initially and then decreased. After 408 days, Mn concentrations were considerably lower at pH 3.0 than under any other treatment. Manganese was the only element whose concentration was found to depend on sulfuric acid rain treatment.
Reaction anatomy and reorientation in leaning stems of balsa (Ochroma) and papaya (Carica)
Authors: Fisher Jack B. , Mueller Richard J.
Published: August 2008

Young trees of balsa (Ochroma pyramidale) and papaya (Carica papaya) were repotted at approximately 45° from the vertical or as vertical controls. Leaning trees of both species reoriented toward the vertical. The apical region curved upward within hours and the basal region, with extensive secondary growth, began to reorient within 2 days. The anatomical basis of this change was investigated. No gelatinous (tension) fibers formed, but eccentric growth (more secondary tissue on the upper side) occurred, and a characteristic reaction anatomy was found which is described for each species. Statistically significant differences in longitudinal surface contraction or expansion, phloem ray dilation, and phloem ray cell lengths were found between upper and lower sides of reoriented stems. The possible role of the separation of primary phloem fiber groups and differential growth of phloem ray cells in axis movement is discussed.
Abscisic acid blocks antheridiogen-induced antheridium formation in gametophytes of the fern Ceratopteris
Authors: Hickok Leslie G.
Published: August 2008

Growth and differentiation of haploid gametophytes of the fern Ceratopteris are influenced by antheridiogen and abscisic acid. Antheridiogen induces the premature formation of male sex organs (antheridia), while abscisic acid, at a concentration of 10−4 M, completely blocks antheridia formation, even in the presence of antheridiogen. In addition, abscisic acid stimulates rhizoid production at concentrations of 10−6–10−5 M but becomes inhibitory at higher concentrations. Meristem development, which is normally at the margins of gametophytes, is often submarginal or central in the presence of abscisic acid and results in the formation of cup-shaped female gametophytes bearing archegonia.
Endogone pisiformis: axenic culture and associations with Sphagnum, Pinus sylvestris, Allium cepa, and Allium porrum
Authors: Berch S. M. , Fortin J. A.
Published: August 2008

Endogone pisiformis is described in pure culture on various normal mycological media. The usually coenocytic mycelium is characteristically coloured yellow and bears numerous lipid-fllled hyphal swellings. Under axenic conditions, hyphae are attracted to Sphagnum, but the fungus has neither sporulated on nor parasitized the Sphagnum. Endogone pisiformis does not form ectomycorrhizae under the conditions studied with inoculated Pinus sylvestris although the fungus may survive in its rhizosphere. Germinated Allium porrum and Allium cepa seeds, moribund roots, and shoots were colonized by Endogone pisiformis which formed densely branched, fine hyphal structures and lipid-filled hyphal swellings within these plant tissues. The possibility is raised that these structures are homologous to the arbuscules and vesicles of vesicular–arbuscular mycorrhizal fungi. Examination of other Endogone species may elucidate the phylogeny of this genus.
Comparative ultrastructural analysis of mycorrhizal associations
Authors: Scannerini Silvano , Bonfante-Fasolo Paola
Published: August 2008

Electron microscopy is a powerful tool in understanding functional mechanisms in symbiosis (i.e., recognition and transfer of nutrients between partners), but mycorrhizal associations are not yet so well known as host–pathogen and host – mutualistic bacterial associations. However, the study of mycorrhizal ultrastructure has provided some interesting information. In fact unknown symbionts can be recognized with electron microscopy and mycorrhizae can be classified according to a sequence linking intercellular and intracellular interactions between host and fungus. General conclusions can be drawn from this ultrastructural sequence. (i) The most significant cytological feature in mycorrhizae is the presence of an interface through which partners communicate along a vast surface area. This is the key area for symbiotic interactions (both recognition and nutrient transfer) and can vary a great deal mostly in intracellular interactions. (ii) The ultracytochemical aspects of those interfaces, mostly as regards the components of the interfacial matrix, appear quite different from those of host–pathogen associations and suggest a compatibility mechanism. (iii) As regards the transfer of nutrients, even though it has been claimed that transfer of nutrient in all intracellular interactions is achieved by a digestion mechanism of the fungus by the host, available ultrastructural data are not consistent with this hypothesis.
The physiology of vesicular–arbuscular endomycorrhizal symbiosis
Authors: Hayman D. S.
Published: August 2008

The enhanced growth of plants infected by vesicular–arbuscular (VA) mycorrhizal fungi results primarily from improved uptake of soil phosphate. Extra phosphate reaches the root through the fungal hyphae, which tap the soluble P in soil beyond the phosphate-depletion zone near the root surface. This mechanism can explain the many corrrelations between root geometry and mycotrophy and other nutritional effects of VA mycorrhizae such as increased uptake of zinc and copper ions. Recently VA mycorrhizae have been shown to increase the levels of chlorophyll and some hormones in plants and to alleviate water stress. Legumes are now receiving considerable attention because VA mycorrhiza affects nitrogen fixation in them indirectly by its action on P uptake. In this review the physiology of the VA mycorrhizal symbiosis is discussed in categories reflecting successive stages in its formation and function: (i) activation of the VA mycorrhizal propagules; (ii) penetration and initial infection of the host plant; (iii) spread of infection in roots; (iv) response of the plant; the components and mechanisms of VA mycorrhizal systems; (v) benefits to the fungus; carbon sinks; and (vi) imbalances in the symbiosis. It is suggested that studies on the physiological complexities of VA mycorrhizal associations should take more account of the biological diversity of VA mycorrhizal fungi and the wide range of host–endophyte–soil specificities.
Interactions of nitrogen and carbon in the physiology of ectomycorrhizae
Authors: France R. C. , Reid C. P. P.
Published: August 2008

The interactive role of nitrogen and carbon in the physiology of ectomycorrhizae (ECM) is examined. Nitrogen availability in forest soils dictates that inorganic forms are absorbed by ECM. The basic aspects of nitrogen metabolism (i.e., absorption, assimilation, translocation) in trees appear similar to those of other higher plants. Ectomycorrhizal fungi are selective in nitrogen preference but can generally utilize both ammonium and nitrate. Absorption of nitrogen from soil by ECM is dependent on the extent of absorbing surfaces and absorption efficiency. Carbon utilization by ECM fungi is less specific in pure culture than in symbiotic association. Fungi, as well as noninfected roots, can fix bicarbonate for specific amino acid biosynthesis. Carbohydrate movement preferentially occurs from host to fungus in the ECM. Fungal sheath absorption of nitrogen and accumulation through assimilatory enzymatic processes create a storage pool for nitrogen in the fungus. Directional transport of specific amino acids from fungus to host is metabolically mediated. Synergism occurs in carbon utilization and amino acid transport owing to the symbiosis. Partitioning of nitrogen within the tree is regulated by root-system and shoot-system sinks. A conceptual model is presented which encompasses the various aspects of the nitrogen and carbon physiological interactions in ECM.
The biology of mycorrhiza in the Ericales
Authors: Read D. J.
Published: August 2008

The types of mycorrhizal structure seen in the Ericaceae and in the closely related families Pyrolaceae and Monotropaceae are reviewed briefly. Ericoid, arbutoid, and monotropoid mycorrhizas are characterized. The processes of infection and of establishment of the mature ericoid mycorrhizal association are discussed from the structural, ultrastructural, and functional viewpoints. Infection provides an enhancement of N and P supply to the host plant. The enhancement of N supply arises from an improved exploitation of "available" ammonium ions and from the capacity, provided exclusively by the mycorrhizal fungus, to utilize simple organic nitrogen compounds. The endophyte also provides increased phosphatase activity and access to what are otherwise only slightly available organic sources of phosphates. In addition to enhancement of host nutrition in circumstances of low nutrient availability, it is shown that ericoid mycorrhizal infection leads to restriction of uptake of metallic elements when these are present in high concentration. Infection thus provides resistance to heavy metal toxicity. The significance of these observations is discussed in relation to the capacity of plants with ericoid mycorrhizas to exploit marginal ecological situations in temperate, boreal, subarctic, and alpine regions throughout the world.
The role of mycorrhizae in plant ecology
Authors: John T. V. St. , Coleman D. C.
Published: August 2008

The effects of vesicular–arbuscular mycorrhizae (VAM) and ectomycorrhizae (ECM) on plant ecology are considered, with emphasis on four areas. The first of these is mycotrophy in wild plants. We suggest that many natives have lower nutrient demands than crop plants and may therefore be less responsive to mycorrhizal infection. Pot experiments must be interpreted with caution because their outcome is strongly influenced by such factors as soil type and pot size. The second topic is the role of mycorrhizae in competition. Mycorrhizae have been shown to figure in plant–plant competition for limited resources. Several lines of indirect evidence suggest that mycorrhizae are involved in allelopathic interactions between plants. Mycorrhizae could aid in competition between plants and microorganisms. Mycorrhizal roots are sometimes found in humus layers of the forest floor. It has been postulated that mycorrhizal fungi influence the decomposition of plant detritus. The most important role of mycorrhizal roots in the organic layer may be, in many cases, a close physical association with the most nutrient-rich microsites of the heterogeneous soil volume. The ability to allocate absorbing tissue to localized organic matter zones has been documented for roots of forest trees and for hyphae of VAM fungi. The advantageous physical placement may result in greater nutrient acquisition for the plant than would occur if root and hyphal distribution were random. Third, the occurrence of mycorrhizae in natural communities has not frequently been documented in ways that show the abundance of infection in the whole community. Future surveys in natural ecosystems should include a measure of the relative abundance of the major plant species in the community. The final topic is carbon allocation to the symbiosis. We suggest that estimates for VAM from a few percent to ~50% of gross photosynthesis can be reconciled to some extent by considering the dynamic processes of root and mycelial turnover.
The floral development and floral anatomy ofCoris monspeliensis
Authors: Decraene L. P. Ronse , Smets E. F. , Clinckemaillie D.
Published: August 2008

The floral development of Coris was investigated to clarify its controversial relationship with either Primulaceae (Primulales) or Lythraceae (Myrtales). We demonstrate that Coris is strongly related to the Primulaceae but differs in a few important features, such as the presence of an epicalyx and partial zygomorphy. The saccate calyx and epicalyx with unilateral development encloses an actinomorphic flower. The stamen–petal tube has two sections that arise through three growth processes: a lower common part for stamens and petals and an upper section representing a fused corolla. The central ovule-bearing part of the ovary arises separated from the carpel wall. The formation of ridges with teethlike appendages between the ovules suggests a derivation of the free-central placentation from an axile arrangement. Several characters support the monotypic family Coridaceae near the Primulaceae. Key words: Coridaceae, Primulaceae, Lythraceae, floral development, floral vasculature, epicalyx, free-central placentation, common primordium, zygomorphy.
Changes in the plant endomembrane system associated with callose synthesis during the interaction between cowpea (Vigna unguiculata) and the cowpea rust fungus (Uromyces vignae)
Authors: Škalamera Dubravka , Heath Michèle C.
Published: August 2008

Electron microscopy and stereological analysis of cowpea (Vigna unguiculata) leaf tissue infected with the cowpea rust fungus (Uromyces vignae) revealed an increase in surface of plant endomembranes that was associated with callose synthesis or the presence of fungal haustoria. In the resistant cultivar in which the haustorium commonly becomes encased, an increase in surface of smooth membranes was observed in cytoplasmic regions adjacent to developing encasements compared with the regions away from the fungus or with any region in infected or uninfected callose nonsynthesizing cells. Cytoplasmic regions adjacent to the haustorium in callose nonsynthesizing cells had an increase in rough endoplasmic reticulum (ER). This increase was greater in a susceptible cultivar than in the resistant cultivar that was treated with tunicamycin to inhibit callose synthesis. In the latter situation, the lack of callose encasement allowed the haustorial neckband to form, but other ultrastructural signs of incompatibility remained, such as the presence of electron-opaque material associated with the extrahaustorial membrane. No differences between cultivars or treatments were observed in Golgi membranes. Our observations suggest that both callose synthesis and fungal presence are associated with de novo synthesis of membranes; callose deposition may require an increase in smooth membranes of uncertain origin, whereas the establishment of a haustorium may be dependent on increased synthesis of rough ER. Key words: callose, endoplasmic reticulum, resistance, stereology, tunicamycin.
Influence of the bioherbicide phosphinothricin on interactions between phytopathogens and their antagonists
Authors: Ahmad Iftikhar , Malloch David , Bissett John
Published: August 2008

Phosphinothricin is a microbial toxin currently under development as a selective weed killer in the cultivation of transgenic plants engineered to resist its presence. Here it is shown that phosphinothricin is inhibitory to antagonistic soil microorganisms including Bacillus subtilis, Pseudomonas flourescens, and many species of Trichoderma. Phosphinothricin was also inhibitory to the phytopathogenic fungi Rhizoctonia solani and Sclerotinia sclerotiorum. In contrast, phytopathogens Fusarium oxysporum and Pythium aphanidermatum were highly resistant to phosphinothricin. In pathogen–antagonist challenges, species of Trichoderma that parasitize F. oxysporum and P. aphanidermatum were eliminated when phosphinothricin was added to the growth media. Similarly, the ability of Pseudomonas fluorescens to exclude Pythium aphanidermatum was markedly affected by the presence of phosphinothricin in the media. The dominance equilibrium between Trichoderma species and the bacterium Bacillus subtilis was influenced in favor of the former at 0 and 5 mM concentrations of the herbicide and in favor of the latter at 1 mM concentrations. Pseudomonas fluorescens was unable to exclude Trichoderma species regardless of the phosphinothricin concentration in the media. Key words: phosphinothricin, pathogens, fungi, bacteria, antagonists, biocontrol.
Spore wall ontogeny inPseudoplectania nigrellaandPlectania nannfeldtii(Ascomycotina, Pezizales)
Authors: Li Li-Tzu , Kimbrough James W.
Published: August 2008

Pseudoplectania and Plectania currently belong to the Sarcosomataceae, tribe Sarcosomateae, a group with members lacking cyanophilic spore markings (absorbing a blue stain). The two genera are morphologically similar in having blackish discoid-shaped apothecia but differ in having globose and ellipsoid spores, respectively. Ultrastructural studies show that ascospores of Pseudoplectania nigrella (Pers. ex Fr.) Fuckel lack a secondary wall layer. On the contrary, Plectania nannfeldtii Korf has secondary spore wall ornamentation that is cyanophilic under a light microscope. The data suggest retention of Pseudoplectania nigrella in the Sarcosomateae; however, the position of certain species of Plectania needs to be reevaluated. Key words: Pezizales, Plectania, Pseudoplectania, Sarcosomataceae, spore ontogeny, ultrastructure.
Vegetative interactions among mycelia of Laccaria bicolor in pure culture and in symbiosis with Pinus banksiana
Authors: Bastide Paul Y. de la , Piché Yves , Kropp Bradley R.
Published: August 2008

Mycelial interactions of Laccaria bicolor strains were studied in pure culture and after inoculation onto mycorrhizal hosts. Monokaryon–monokaryon and dikaryon–monokaryon crosses were performed on an agar medium that enhanced nuclear migration to study mating events. The first observance of clamped hyphae, their location, evidence of nuclear migration, and the occurrence of dikaryon–monokaryon matings varied among crosses. One monokaryon–monokaryon and two dikaryon–monokaryon combinations were selected for seedling inoculation to compare their mycorrhizosphere interactions with those observed on agar medium. Seedlings of Pinus banksiana were grown for 20 weeks in a mycelium inoculated soil medium. Three seedlings from each treatment were selected at harvest and ectomycorrhizae reisolates were subject to randomly amplified polymorphic DNA analysis to identify genotypes. This analysis was also done for mycelial samples of the same crosses on agar medium. Variation in the mycobiont genotype was observed for different root isolates from the same seedling, which had been initially inoculated with a compatible monokaryon–monokaryon or a dikaryon–monokaryon strain combination. Root isolates from seedlings receiving the latter treatment included a new dikaryotic genotype produced by a dikaryon–monokaryon mating. Seedling growth was reduced with ectomycorrhizal colonization, most likely because of the photosynthate requirements of the mycobiont during this study. The nature of mycelial interactions and the potential value of a genetically variable mycobiont are discussed. Key words: Buller phenomenon, ectomycorrhizae, intraspecific variability, mycelial interactions, RAPD analysis.
Quantitative analysis of sexual dimorphism inAsparagus
Authors: Machon N. , Boulc'h V. Deletre-Le , Rameau C.
Published: August 2008

In the dioecious perennial Asparagus officinalis, female function, estimated by the number of berries per plant and seeds per berry, was positively correlated with stem diameter and height and negatively correlated with stem number. In contrast, male function, estimated by the mean production of pollen per flower and by the number of male flowers per ramet, was positively correlated with stem number and negatively correlated with stem diameter and height. These correlations, which are calculated between mean values per genotype, are in accordance with sexual dimorphism in this species: male plants produce more but thinner stems than female plants. We propose that morphological constraints at the plant level could have favoured the evolution of dioecy in this species. Key words: Asparagus officinalis, dioecy, sexual dimorphism, pollen production, seed set.
A chromosome atlas and interspecific – intergenic index for Lotus and Tetragonolobus (Fabaceae)
Authors: Grant William F.
Published: August 2008

Basic chromosome numbers in Lotus are x = 5, 6, and 7. It is considered that evolution has proceeded in the genus by means of a descending aneuploid series from an eight-chromosomed ancestor. Chromosome numbers for species of Tetragonolobus are based on x = 7. Somatic chromosome numbers are reported for 108 species and 38 varieties. The chromosome numbers for five species (L. hamatus Greene, 2n = 14, L. haydonii (Orcutt) Greene, 2n = 14, L. hintoniorum B.L. Turner, 2n = 14, L. mearnsii Britton, 2n = 14, L. utahensis Ottley, 2n = 14) and seven varieties (L. argophyllus (Gray) Green var. argenteus Dunkle, 2n = 14, L. dendroideus var. traskiae (Eastwood ex Noddin) Isely, 2n = 14, L. heermanii (Durand et Hilgard) Greene var. orbicularis (Gray) Isely, 2n = 14, L. junceus (Benth.) Greene var. biolettii (Greene) Ottley, 2n = 14, L. strigosus var. hirtellus (Greene) Ottley, 2n = 14, L. strigosus var. tomentellus (Greene) Isely, 2n = 14, L. uliginosus ssp. vestitus (Lange) A. Pedersen, 2n = 12) are reported for the first time. Natural diploid, tetraploid, and hexaploid plants are reported for L. alpinus. Several species are reported as possessing B chromosomes. Mixoploidy is reported to occur in three species (L. alpinus, L. glacialis, L. glareosus). In addition, chromosome numbers are given for plants regenerated from calluses grown in tissue culture having both heteroploidy, euploidy, and mixoploidy. Root nodules are reported with tetraploid and octoploid cells in addition to the normal number of chromosomes. Trisomie series have been partially developed in L. tenuis and L. uliginosus. Polytene chromosomes were observed in suspensor cells of three species of Lotus. Feulgen cytophotometric measurements, to determine the DNA nuclear content, were made for 16 species of Lotus and one species of Tetragonolobus. The majority of the studies in Lotus concern the economic species L. corniculatus, L. tenuis, and L. uliginosus. Interspecific hybridization was carried out in different combinations between diploids, autoploids, and amphidiploids. Intergeneric hybrids were attempted by somatic hybridization, protoplast fusion, and asymmetric hybridization between Lotus and other species (Glycine max, Medicago sativa, Oryza sativa). Key words: chromosome numbers, DNA values, Fabaceae, Lotus species, interspecific hybrids, intergeneric hybrids, Tetragonolobus.
Phenotypic plasticity in leaves of four species of arctic Festuca (Poaceae)
Authors: Ramesar-Fortner Nicole S. , Dengler Nancy G. , Aiken Susan G.
Published: August 2008

Leaf phenotypic plasticity of 12 morphological, anatomical, and growth traits was investigated using four species of arctic Festuca (F. baffinensis, F. brachyphylla, F. edlundiae, and F. hyperborea). Plants collected around 78°N in the Canadian Arctic Archipelago were grown for 10 weeks at the University of Toronto in growth chambers in continuous light, under four regimes of temperature and moisture. Significant differences were found between leaves at the time of field collection and leaves of the same plant at the end of the experiment in (i) leaf blade length, (ii) surface vestiture, both in trichome density and angle of the trichomes to the blade surface, and (iii) characters seen in leaf cross sections: blade width, rib thickness, and inter-rib thickness. The four species responded similarly to the experimental conditions, indicating that most of these changes represent part of the developmentally inevitable component of plasticity rather than species-specific adaptations. Trichome density was the only characteristic for which species showed different patterns of response, with a unique pattern of response in F. edlundiae. This and certain growth traits support the taxonomic status of this newly recognized species. The significant effects of temperature and to a lesser degree, water treatments on these leaf anatomical traits indicate that they should be used with caution for the purposes of taxonomy and identification. Key words: Festuca, leaf blade anatomy, phenotypic plasticity.
Reduced Genetic Variability in First-Generation Hatchery Populations of Atlantic Salmon (Salmo salar)
Authors: Verspoor Eric
Published: August 2008

Levels of genetic variation were measured in first-generation Atlantic salmon (Salmo salar) cultured for stock enhancement programs in eastern Canada and compared with variation in wild stocks. One regulatory and 19 structural protein loci were screened of which 10 were polymorphic. Mean heterozygosity and number of alleles per locus were positively correlated with the effective number of adults (N) used to establish the hatchery groups and averaged 26 and 12% lower, respectively, than wild stocks. The observations are consistent with a loss of genetic variability in the hatchery salmon from random drift caused by using small numbers of salmon for broodstock.
Multivariate Analysis of Correlations Between Environmental Parameters and Cadmium Concentrations in Hyalella azteca (Crustacea: Amphipoda) from Central Ontario Lakes
Authors: Stephenson M. , Mackie G. L.
Published: August 2008

Cadmium concentrations in Hyalella azteca collected from 69 central Ontario lakes ranged from 0.13 to 56.6 μg/g dry mass. Principal components analysis followed by multiple linear regression found three principal components, interpreted as water hardness, total cadmium, and dissolved organic carbon concentrations, to be significantly [Formula: see text] correlated with cadmium concentrations in H. azteca. Cadmium concentrations in H. azteca were independent of cadmium concentrations in littoral sediments. It is suggested that cadmium ions compete with calcium ions for uptake sites on the gill surfaces of H. azteca. High concentrations of dissolved organic carbon may complex free cadmium ions and reduce their concentration in solution, leading to lower cadmium concentrations in H. azteca.
Empirical Models Predicting Ingestion Rates of Black Fly Larvae
Authors: Morin Antoine , Back Christian , Chalifour Alain , Boisvert Jacques , Peters Robert H.
Published: August 2008

Field experiments were performed in a gutter system to examine the effect of body size, water temperature, seston concentration, and particle type on the ingestion rate of Simulium venustum/verecundum larvae. Ingestion rates rose exponentially with increasing temperature between 9 and 19 °C (Q10 = 2.19, 95% CI 2.09–2.29) and rose asymptotically with seston concentration (range 0.7–30 mg∙L−1). Small larvae were more sensitive to variations in seston concentration than older instars. The type of particles offered also influenced the ingestion rate of larvae. Once corrected for body size, water temperature, and seston concentration, the data show that larvae ingested more of the natural seston and of a yeast suspension than of suspensions containing kaolinite. Ingestion rates of other simuliid species generally co-occurring at the outflow of lakes in early summer were of the same magnitude as those of S. venustum/verecundum, although significant differences were detected among species. Specific ingestion rates of simuliids decline with increasing mass, are similar to those measured for benthic detritivores, and tend to be higher than those of marine and freshwater zooplankton of similar size. The models are discussed with respect to black fly control with particulate larvicides.
Effect of Stochasticity on Optimal Harvesting Strategies in Some Lumped-Parameter Fishery Models
Authors: Lovejoy William S.
Published: August 2008

This paper introduces some methods for anticipating the difference between optimal harvesting strategies in a fishery model with stochastic recruitment and in the corresponding deterministic model with recruitment equal to its expected value. It extends known results on the sign of the difference and presents ways to estimate the magnitude. Two classes of lumped-parameter models are discussed. In myopic models, the policy difference is likely to be insignificant. In more general models with downward sloping demand for fish and increasing marginal cost of fishing effort, a heuristic measure is introduced that can suggest the direction and magnitude of the policy shift.
Effets chimiques et cytologiques de la contamination expérimentale de I'huître Crassostrea gigas Thunberg par l'argent administré sous forme dissoute et par voie alimentaire
Authors: Martoja Roger , Ballan-Dufrançais Christiane , Jeantet Anne-Yvonne , Gouzerh Pierre , Amiard Jean-Claude , Amiard-Triquet Claude , Berthet Brigitte , Baud Jean-Pierre
Published: August 2008

not available
Predicting Nighttime Dissolved Oxygen Loss in Aquaculture Ponds
Authors: Madenjian Charles M. , Rogers Gary L. , Fast Arlo W.
Published: August 2008

The Whole Pond Respiration–Diffusion (WPRD) model was evaluated for brackish-water ponds. The WPRD model accurately describes the nighttime decline of dissolved oxygen concentration (DO) in both freshwater and brackish-water ponds. DO, water temperature, and wind speed were monitored overnight in marine shrimp (Penaeus vannamei and P. monodon) ponds at Amorient Aquafarm Inc. (Kahuku, Oahu) and at the Mariculture Research and Training Center (Hakipuu, Oahu) during July through December 1986. The model performed well for calm nights (wind speed between 1 and 2 m∙s−1) and for relatively windy nights (wind speed greater than 7 m∙s−1). Diffusion of oxygen into the ponds, particularly at Amorient, was important in determining the nighttime DO decline. The model has yielded accurate predictions of dawn DO for a variety of aquaculture ponds and meteorological conditions.
Is Research on Environmental Factors Useful to Fisheries Management?
Authors: Walters Carl J. , Collie Jeremy S.
Published: August 2008

The study of environmental effects on fish distributions and recruitment rates has become a major research focus with substantial funding. This research is justified by rather vague claims about understanding the causes of variability and making more accurate predictions based on this understanding, claims which often do not bear close inspection. Improved prediction is often impossible in principle because environmental factors are not predictable even if fish responses are. In some fisheries, prediction could be achieved more cheaply and reliably by direct monitoring programs such as precruitment surveys of year-class strengths. In others, prediction is unnecessary because of existing feedback tactics for regulation, or would be primarily valuable to particular industrial interest groups and hence should not necessarily be subsidized by public research investment. Better understanding is needed for situations in which the effects of environmental factors are confounded with the effects of stock size and fishing. In these cases the key uncertainties will not be resolved by continued correlative and biological process studies and will instead require bold management experiments in which environmental studies are coupled with deliberate manipulation of stock sizes through changes in harvest policies.
Selection of traffic accident countermeasures
Authors: Seneviratne P. N. , Seneviratne A. P.
Published: August 2008

A decision theory approach is proposed for selecting the optimal accident countermeasure when estimates of future accidents at a site and expected proportion of the accidents likely to be prevented by a countermeasure are uncertain. The decision model is transformed into a microcomputer program and a numerical example is used to illustrate the aptness of the approach and its ability to allow analysts to combine empirical data with informed judgment to make decisions systematically. The potential of the program to be expanded to operate with an extensive built-in knowledge base of accident and countermeasure attributes is discussed. Key words: decision theory, probability, expert systems, utility, uncertainty.
Individual driver route guidance systems and their implications for traffic control
Authors: Aerde M. Van , Case E. R.
Published: August 2008

While the basic concept of guiding individual drivers en route to their destination using on-board computers was introduced more than two decades ago, a practical implementation of this concept has only become possible as part of the current microcomputer–communications revolution. This paper assesses the potential role of these on-board route guidance systems as a means of better assisting drivers to make routing decisions and to improve the quality of the data available to the central traffic control system. The assessment indicates that the potential capabilities of these systems are controlled by the type of communications between the on-board units and the central control system, the level of on-board intelligence that is provided, and the integration of these activities within the traffic control model. Key words: traffic control, individual route guidance, driver information systems.
Underpinning of existing industrial plant foundation
Authors: Marzouk H.
Published: August 2008

As a result of environmental changes in the design requirements, many old industrial structures for chemical, power plants, and processing mines now face the problem of changing their process equipment to meet the new code requirements. In most cases, new pieces of equipment, such as scrubbers and filters, are introduced to the process cycle. This kind of equipment is usually very heavy and creates massive loads on the existing foundation.Many existing concrete foundations are unable to safely support the additional loads. It is necessary to increase the existing foundation capacity using the underpinning technique. Normally, the underpinning procedure includes shoring and jacking up of the existing structure. Due to the dynamic nature of loading, it is often required to shut down the plant for the foundation underpinning. However, the high cost of such a shutdown (0.5 to 1.0 million dollars a day) makes it necessary to develop new underpinning techniques to double the capacity of the concrete foundation while the plant is in full production. This paper describes the case of underpinning a chemical plant near Regina. Three design alternatives were proposed for the underpinning. A suitable design method was adopted and the construction was completed during the spring of 1985. Key words: underpinning, strengthening, footings, steel grillage, concrete repair, pile cap, deep beam, construction procedure.