bluuebunny/crossref_metadata_2025 huggingface dataset:
Independent Meshing of Contact Surfaces in 3D Boundary Element Method Contact Analysis
Authors: Sahli A. , Guemmour M. B. , Kebdani S. , Boutchicha D. , Rahmani O.
Published: May 2008

This paper deals with the development of two new boundary element algorithms for solving 3D, frictional, and linear elastostatic contact problems. The main contribution of this research is that solving 3D boundary element models with nonconforming discretizations becomes possible for the first time by using the proposed algorithms. The new algorithms provide the contact constraint equations that will be added to the underdetermined linear system of equations. These algorithms are implemented in a new 3D boundary element code using C++ and verified using several numerical examples. For the models studied, the results using the new boundary element algorithms match well with the finite element results and clearly demonstrate the feasibility of the new boundary element approach for 3D contact analysis.
Blue light stimulated oxygen uptake mediated by FMN in a colorless Chlorella mutant
Authors: Lee D. , Sargent D. F. , Taylor C. P. S.
Published: May 2008

In a colorless Chlorella mutant we have found only a very slight enhancement of oxygen uptake in blue light unless FMN is added to the medium. Inhibitor studies and control experiments show that a biological oxidation is involved in the increased oxygen uptake in addition to the well-known photochemical oxidations caused by free FMN. We conclude that FMN is a necessary cofactor in the blue light stimulated oxygen uptake observed in this mutant. Because of its direct role in the process FMN probably also functions as the primary light receptor. The relationship of this enhanced oxygen uptake to the blue light enhancement effects reported by others is considered briefly.
Investigations of the flowering of Saccharum. I. Ontogeny of the inflorescence
Authors: Moore Paul H.
Published: May 2008

Early development of the inflorescence of two hybrid clones in the genus Saccharum is presented. Stages of inflorescence development are described for those phases having potential for either further reproductive development or reversion to vegetative growth. The stage of irreversible reproductive growth is ontogenetically much later for Saccharum than for other plants.
Conjugation and chlamydospores in Sporobolomyces odorus
Authors: Bandoni R. J. , Lobo K. J. , Brezden S. A.
Published: May 2008

Conjugation was observed in mix-mated pairs of 16 Sporobolomyces odorus isolates. The mating tests suggest a simple bipolar mating system. Conjugation resulted in the development of dikaryotic hyphae with clamp connections, and in chlamydospore formation. This dikaryotic phase closely resembled that of Sporidiobolus johnsonii. The chlamydospores germinated by the production of promycelium-like structures or of dikaryotic hyphae.
The systematic position of Claytonia bostockii
Authors: McNeill J. , Findlay Judy N.
Published: May 2008

Claytonia bostockii Porsild (Portulacaceae), an endemic to S.W. Yukon and adjacent parts of Alaska, whose systematic position in the Claytonia/Montia generic complex has not hitherto been examined, is shown to possess the distinctive 'Montiastrum-type' of spiniferously saccate pollen. It is suggested that C. bostockii be referred, along with the closely related C. vassilievii and the less similar C. linearis and C. dichotoma, to Claytonia Section Montiastrum Gray. Distinguishing characters are tabulated.
Autecology of a filamentous alga, Ctenocladus circinnatus (Chlorophyceae), in saline environments
Authors: Blinn Dean W.
Published: May 2008

Six highly saline habitats in arid regions of British Columbia, Nevada, and California with the chaetophoralean Ctenocladus circinnatus Borzi were investigated to characterize the unique environment of this alga. Seasonal patterns within three of these habitats were analyzed to reveal those parameters determining the restricted distribution of Ctenocladus. Sodium was the dominant cation in combination with any major anion, such as SO4−, CO3−, HCO3−. Seasonal salinity fluctuations of the water solutions were large (< 10– > 100 millimhos). Ctenocladus tolerated these high salinities and temperatures (−3 to 28 °C) as akinetes formed early in the summer and they survived as akinetes until dilution of the water solutions the next spring. The period for optimum vegetative development was short (6–12 weeks) because of an increase in salinity and temperature of the waters.Akinete germination in the laboratory was optimal between 9 and 26 °C and temperatures above 34 °C destroyed akinetes. Conversely, the freezing of akinetes produced no adverse affects. Laboratory studies showed germination and vegetative development retarded at pH below 8.0 with akinetes destroyed below 7.0. Light is essential for germination with low light intensities (214 lx) stimulating germination. Light intensities above 12 000 lx destroyed akinetes within 5 days. Sexual reproduction in both the field and laboratory was absent. The significance of the akinete and lack of sexual reproduction are correlated with laboratory and field data and the restricted distribution of Ctenocladus.
Photosynthetic assimilation and translocation of 3H- and 14C-organic compounds after 3HHO and 14CO2 were simultaneously offered to a primary leaf of soybean
Authors: Thompson Robert G. , Nelsons C. D.
Published: May 2008

After assimilation of both 3HHO and 14CO2 by soybean (Glycine max L.) in the light, the percentage of nonexchangeable 3H was similar to the percentage of 14C distributed in each of the identified sugars, amino acids, and organic acids with the exceptions of glycine–serine and glutamic acids. Glycine–serine contained proportionally more 14C than expected on the basis of percentage of 3H; and glutamic acid contained proportionally more 3H than expected on the basis of 14C. Both 3H- and 14C-organic compounds were translocated in the same proportions to various parts of the plant and in both cases the main compound translocated was apparently sucrose. The metabolism of dark-assimilated 3H was different from dark-assimilated 14C, but in both cases it did not contribute significantly to the total metabolism of the plant.
Effect of a Typhula sp. on the growth of strawberry and other plants at low temperatures
Authors: Lockhart C. L.
Published: May 2008

At temperatures simulating spring growing conditions, a Typhula sp. induced poor growth and killed strawberry plants. After soil inoculation with this Typhula, small dark lesions were observed on the roots of alsike clover, the growth of timothy was reduced, but the growth of red clover, oat, pea, and rye was not affected.
Seasonal cytological changes in secondary phloem parenchyma cells in Robinia pseudoacacia in relation to cold hardiness
Authors: Pomeroy M. K. , Siminovitch D.
Published: May 2008

Electron microscopic studies of cytological changes in phloem parenchyma cells of the living bark of black locust, Robinia pseudoacacia L., indicate that seasonal augmentation in total protoplasm, including mitochondria, lipid bodies, and, particularly, membrane-bound vesicles derived from invaginations and folding of the plasmalemma are closely related to the seasonal cycle of frost resistance. The structural organization of the endoplasmic reticulum also varies seasonally. In summer it is present as long cisternae-like units, which, during autumn and winter, appear to be replaced by a vesicular form of endoplasmic reticulum. Starch content does not appear to be closely related to initiation of the hardening process, but maximum hardiness is not developed until nearly all of the starch has disappeared from the cells. The observations support the view that the total expression of frost resistance in plant cells involves participation of the following three mechanisms: (1) augmentation of total protoplasm, extending to organelles, surface membranes, and other structural components of the cell; (2) lipid transformations; and (3) starch–sugar transformations.
Structural changes in a Hieracium floribundum (Compositae) population associated with the process of patch formation
Authors: Reader R. J.
Published: May 2008

The contribution of yellow devil hawkweed (H. floribundum) to the total standing crop of an abandoned pasture in southern Ontario increased from approximately 8% to 70% as H. floribundum colonized the pasture by forming patches containing as many as 3400 rosettes/m2. Within the hawkweed population, there was a significant (P < 0.05) shift in the distribution of standing crop from reproductive to vegetative structures and within the vegetative structures from leaves to roots and rhizome during the process of patch formation. These shifts presumably occurred in response to changing environmental conditions (i.e., increasing light availability, reduced soil moisture levels, greater intraspecific competition). The mechanism by which the allocation pattern changed was more likely phenotypic plasticity than genetic change since H. floribundum is an apomict and vegetative reproduction accounted for most recruitment into the population.The frequency distribution of population members in dry weight classes became more negatively skewed during the process of patch formation, but the distribution did not approach log-normality as predicted in some studies. Significant (P < 0.05) differences were observed in the allocation patterns of individuals belonging to different weight classes in the population. Only the largest plants in the population allocated dry weight to reproductive structures.
The external force method for measuring hydraulic conductivity and elastic coefficients in higher plant cells: application to multilayer tissue sections and further theoretical development
Authors: Ferrier Jack M. , Dainty Jack
Published: May 2008

The external force method for measuring hydraulic conductivity and elastic coefficients in higher plants cells (Ferrier and Dainty, 1977, Can. J. Bot. 55: 858–866) is applied to multilayer tissue sections, and the theoretical analysis further developed. Measurements on storage tissue cells of red beet (Beta vulgaris) and artichoke (Helianthus tuberosis) give values for the water potential equilibration time constant (τ) of between 1 and 2 min, and values for cell membrane hydraulic conductivity (Lp) between 2 × 10−7 and 4 × 10−6 cm s−1 bar−1. Measurements on leaves of the aquatic plant Potamogeton lucens give similar values for τ, and lower values for Lp. Some limitations of the external force method are discussed.
Colonization of conifer needles by aquatic hyphomycetes
Authors: Bärlocher Felix , Oertli J. J.
Published: May 2008

Dead needles of Abies alba, Pinus sylvestris, P. leucodermis, and Sequoia gigantea were immersed in a stream for 28 days and then examined for conidiophores of aquatic hyphomycetes. Contrary to statements in the literature, these fungi were found to colonize untreated needles. However, numbers of species and conidiophores were significantly higher on needles treated with steam before immersion than on untreated needles; both values were also higher on cut surfaces (mesophyll) than on intact surfaces (epidermis with cuticle) of longitudinally halved needles.Addition of untreated needle powder (Sequoia, P. leucodermis) to malt extract agar depressed linear growth of pure cultures of five aquatic hyphomycetes. The inhibition persisted when a 0.2-μm membrane filter was placed between medium and fungal cultures. On water agar, by itself unsuitable for fungal growth, low doses of needle powder allowed growth of the same fungi. At higher doses, inhibition again became predominant. Steam distillation of needle powder yielded three fractions: solid residue, soluble residue, and steam distillate. Steam distillate did not influence fungal growth on the two media, while the other two fractions supported growth on water agar but did not lead to a clear dosage–effect curve on malt extract agar.
Photosynthesis and nonstructural carbohydrate concentration in leaf blades of Panicum virgatum as affected by night temperature
Authors: Ku S. B. , Edwards G. E. , Smith Dale
Published: May 2008

Panicum virgatum is considered a relatively cold-tolerant C4 species to low night temperature from analysis of top growth, photosynthesis, dark respiration, and day–night fluctuation of nonstructural carbohydrate concentration in leaf blades grown under temperature regimes of 30–30, 30–20, and 30–10 °C. There was little influence of night temperature of 10 to 30 °C on top growth, although 20 °C night temperature was optimum. Plants grown under low night temperature (10 °C) showed a slightly reduced rate of photosynthesis early in the photoperiod, while plants at 30 °C night temperature had the highest rates of dark respiration. The time required for the plants to reach maximal photosynthetic rate from the beginning of the photoperiod was prolonged with decreased night temperature, being 1.0, 1.5, and 2.5 h for plants grown at 30–30, 30–20, and 30–10 °C regimes, respectively. Photosynthetic rates progressively declined during the rest of the photoperiod. The change in photosynthetic rate during the photoperiod and influence of night temperature on photosynthesis was highly correlated with the change in stomatal resistance to CO2 transfer (r = −0.9). Starch and total sugars in leaves accumulated slightly with time after initiation of the photoperiod and then were reduced to low levels during the night at all temperatures. Night temperature had no effect on the accumulation of these nonstructural carbohydrates during the day or on depletion from the leaves during the night.
The distribution of Macrocystis integrifolia in British Columbia as related to environmental parameters
Authors: Druehl Louis D.
Published: May 2008

The general distribution of the brown alga Macrocystis integrifolia Bory in British Columbia is related to seasonal seawater temperatures and salinities. This species is restricted to regions having little seasonal variation of seawater temperature and salinity or regions where the lower salinities occur during the winter. Locally, Macrocystis distribution is restricted to moderately wave-exposed areas or areas subjected to appreciable tidal currents, provided solid substrate is available. The vertical distribution is usually determined by substrate availability and sea urchins. Macrocystis blade morphology varies regularly with wave exposure. However, transplant studies indicate that this may, in part, be genetically determined and thus may not be a plastic phenotypic response.
Isoenzyme complexes as indicators of genetic diversity in white spruce, Picea glauca, in southern Ontario and the Yukon Territory. Formic, glutamic, and lactic dehydrogenases and cationic peroxidases
Authors: Tsay Ruey C. , Taylor Iain E. P.
Published: May 2008

A centre of genetic diversity for white spruce, Picea glauca (Moench) Voss, is suspected in and around a refugial region in the Yukon Territory. Seed from the refugium (30 samples), a neighbouring region (42 samples) and from southern Ontario (50 samples) was examined for isoenzymes of formic (FDH), glutamic (GDH), and lactic (LDH) dehydrogenases and cationic peroxidases (CP). FDH patterns were uniform. There were three GDH bands which appeared in five patterns. Eleven isoenzymes of LDH were detected in 21 patterns. There were 25 CP bands and the pattern from each collection (containing 7–13 bands) was unique.The results from GDH, LDH, and CP analyses revealed differences between seed from the refugium and the adjoining regions. The patterns for LDH supported the hypothesis that the refugium was a centre of diversity but the GDH and CP patterns were more diverse outside the refugium. The LDH and CP analyses showed that the genetic resources of the two regions in the Yukon were more diverse than those in southern Ontario. Analysis of divergence showed that these differences were significant at the 1% level of probability.
A double staining technique for improved contrast of thin sections from Spurr-embedded tissue
Authors: Bray D. F. , Wagenaar E. B.
Published: May 2008

A double staining procedure using potassium permanganate and lead citrate is described. The technique, involving treatment of sections with a 1% solution of potassium permanganate followed by lead citrate staining, is shown to be more effective in producing contrast in Spurr-embedded tissue than the conventional uranyl acetate – lead citrate method.
Within-crown variation in dormant long-shoot apices of mature trees of Pinus resinosa
Authors: Riding Richard T.
Published: May 2008

Dormant long-shoot buds were harvested from two 45-year-old trees of Pinus resinosa. The shoot apices were examined for variation in shape, size, and histochemical staining in relation to their position in the crown. On nonshaded branches from the exposed south side of the trees there were no significant differences in size and shape of shoot apices associated with height in the crown. However, on the north side of the tree there was a marked increase in height and height–diameter ratio, and a decrease in diameter of shoot apices from branches below the point where the canopy closed and branches were subject to continual shading. Within the shaded portion of the crown, there were no significant differences in the size and shape of the apices studied. Megasporangiate strobili primordia were found in buds with terminal shoot apices having a low height–diameter ratio (<0.400), whereas microsporangiate strobili primordia were found in buds with terminal shoot apices having a relatively high height–diameter ratio (>0.400). Staining intensity for total carbohydrates, total proteins, and RNA decreased with decreasing height in the crown. There were no great differences in stain intensity between shoot apices from sun and shade branches from the same whorl. Therefore, the potential of a branch appears to be related to the size of the shoot apex which is correlated with its exposure within the crown.
The distribution of silicon deposits in the rhizomes of two Andropogon species
Authors: Sangster A. G.
Published: May 2008

Two deposition sites for silicon, both perivascular, were detected by electron-probe microassay in rhizomes of field specimens of Andropogon gerardii Vitman and A. scoparius Michx. (i) Si was confined, in both species, to several layers of cells immediately outside the stele, occurring therein as silica aggregates restricted to the inner tangential walls (ITW). These Si-accumulating cells exhibited similarities in position, shape, and wall thickness, as well as silica deposits, to root endodermal cells of the same species. (ii)In A. gerardii only, Si was deposited additionally in the central region of the stele, on the ITW of sheath cells surrounding the larger vascular bundles.A comparison of the silica aggregates of the rhizomes in terms of distribution, morphology, and X-ray intensity is made between the two Andropogon species, as well as of the corresponding root deposits. These aggregates may be of significance in aiding the retention of water and solutes within the rhizome.
Stereograms to aid group recognition and trend identification in vegetation data
Authors: Fewster P. , Orlóci L.
Published: May 2008

When vegetation data are summarized on the basis of some method of ordination, a search for distinct groups or trends is greatly facilitated if the cloud of sample points is viewed under a lens stereoscope in three dimensions. The present paper describes a simple method to construct stereograms and illustrates their application in a classification problem.A stereogram is composed of two images of a three-dimensional object. The left image and the right correspond respectively to sightings with the left eye or the right eye of the observer. The diagrams are placed side by side at a specified distance apart, and when viewed with the aid of a stereoscope, the images will merge resulting in a three-dimensional picture.
Influence de la photopériode sur la fasciation et la phase reproductrice du Celosia cristata (Amarantacées)
Authors: Driss-Ecole D.
Published: May 2008

Plants of Celosia cristata L. are removed from an 8- to a 16-h photoperiod or from a 16- to an 8-h photoperiod after 20 or 30 days of culture. The percentages of fasciated stems and of reproductive meristems observed at the 70th day of culture are calculated for control and removed plants. Thus, it is shown that there is an important phase in the plant ontogenesis. This phase corresponds to a new proliferating activity of the corpus on day lengths of 16 h and 8 h.
The taxonomical identity of the perfect state of Pyricularia grisea and its allies
Authors: Yaegashi H. , Udagawa S.
Published: May 2008

Magnaporthe grisea is proposed as a comb.nov. for Ceratosphaeria grisea Hébert, the perfect state of Pyricularia grisea (Cke.) Sacc. Pyricularia grisea is very close morphologically to P. oryzae Cav., well known as the causal agent of blast disease on rice. Magnaporthe was recently established in the Diaporthales to accommodate a single species, M. salvinii (Catt.) Krause & Webster, which was described as the cause of stem rot of rice with conidial state known as Nakataea sigmoidea Hara. Based on a review of the taxonomic characters of Ceratosphaeria grisea, the desirability is discussed of its inclusion in the genus Magnaporthe.
Plasmalemma alteration during cold acclimation of Hedera helix bark
Authors: Stout Darryl G. , Steponkus Peter L. , Cotts Robert M.
Published: May 2008

The transverse relaxation rate of water protons of nonacclimated Hedera helix L. cv. Thorndale (ivy) bark decreased in the presence of added extracellular Ca2+, Mg2+, or CO2. Evidence that the decreased transverse relaxation rate is due to decreased plasmalemma water permeability is presented. The decrease in plasmalemma water permeability induced by Ca2+ and CO2 was less in cold-acclimated ivy bark than in nonacclimated ivy bark, indicating that the process of cold acclimation altered a functional property of the plasmalemma. It is not known if the functional change in the plasmalemma is related to the degree of plant cold hardiness or is simply a low temperature response.
Mycochrome system and conidial development in a nonphotoinduced isolate of Helminthosporium oryzae
Authors: Yamamura Saburo , Kumagai Tadashi , Oda Yoshiharu
Published: May 2008

The effect of light on conidial development of a nonphotoinduced isolate of Helminthosporium oryzae was investigated. Near-ultraviolet light was not required for conidiophore induction, but conidial development was suppressed by blue light applied at a definite stage of conidiophore development, and the conidiophores were dedifferentiated into longer, slender aerial hyphae. Furthermore, the effect of blue light could be reversed by immediate exposure to near-ultraviolet light and the effects of these two spectral regions were alternatively reversible.Thus, it is concluded that a photosensitive system, called mycochrome, is involved in the conidial development of this fungus.
Glycoproteins containing hexosamine in bean leaves
Authors: Racusen David , Foote Murray
Published: May 2008

During normal bean leaf growth, there was almost no change in the solubility classes of glycoprotein. Chloroplasts from mature leaves contained one-third of the insoluble glycoprotein. Glucosamine feeding produced a 10-fold increase in the insoluble glycoprotein of chloroplasts within 16 h. This was accompanied by the appearance of particles surrounding the starch grains and a considerable decrease in starch content.The low and fairly uniform levels of glycoproteins in growing leaves suggest that they play consistent structural or enzymic role rather than serving as reserve foodstuffs as in seeds. However, the abrupt increase in chloroplast glycoprotein upon feeding glucosamine indicates that the synthesis of this special glycoprotein is limited by endogenous precursors.
Rapid, contamination-free sowing of surface-sterilized seeds and spores
Authors: Courtis William S.
Published: May 2008

A novel method and apparatus for rapid aseptic sowing of small seeds and spores by hypodermic syringe is described. The advantages of this method are enumerated.
A new Grovesiella on grand fir
Authors: Funk A.
Published: May 2008

A new discomycete (Helotiales) is described from grand fir (Abies grandis (Dougl.) Lindl.) in British Columbia, Canada; Grovesiella grantii n.sp. occurs on dead branches and as a secondary invader of cankers and dieback produced by other fungus pathogens.
Comparative studies of the exotoxins of Pseudomonas glycinea and Pseudomonas phaseolicola
Authors: Murch Randall S. , Patil Suresh S.
Published: May 2008

A sensitive and quantitative bioassay, based on the ability of the exotoxin of Pseudomonas glycinea to inhibit ornithine carbamoyltransferase of bean, was employed in a comparative study of the P. glycinea and P. phaseolicola toxins using high-voltage electrophoresis, thin-layer chromatography, ultrafiltration, and Sephadex-gel chromatography. The P. glycinea toxin (glytoxin) has an elution volume/void volume (Ve/V0) ratio different from that of phaseotoxin when chromatographed on Sephadex G-25. Glytoxin passes through a membrane filter with an exclusion limit of 500 daltons whereas phaseotoxin does not. High voltage electrophoresis in buffers of different pH values showed that glytoxin, like phaseotoxin, migrates as an anion but shows greater mobility than phaseotoxin. Both toxins degrade on thin layers of silica gel. Glytoxin induces chlorosis in bean and soybean leaf tissues, and like phaseotoxin, is an inhibitor of ornithine carbamoyltransferase but not of aspartate carbamoyltransferase. Glytoxin is presumably responsible for the accumulation of ornithine which was observed in soybean leaves infected with P. glycinea. Our studies show that glytoxin and phaseotoxin are similar but not identical.
Silene alba and S. dioica in North America and the generic delimitation of Lychnis, Melandrium, and Silene (Caryophyllaceae)
Authors: McNeill J.
Published: May 2008

Evidence is presented from numerical studies of herbarium and cultivated specimens and from observations on time of flowering that North American weed populations of white cockle are referable to the European Silene alba (≡ Lychnis alba ≡ Melandrium album) and are not, as has been suggested, the products of hybridization between that species and S. dioica. The present status and distribution in North America of S. alba, S. dioica, and the hybrids between them are described. Evidence for different generic circumscriptions of Silene, Lychnis, and Melandrium is analysed and the limited applicability of the capsule dehiscence character is demonstrated. Recent treatments that accept Lychnis in a narrow sense and assign most of the North American species of the group to a large genus Silene are accepted pending further study. Two new subspecific combinations (S. uralensis subsp. attenuata (Farr) McNeill and S. uralensis subsp. montana (S. Watson) McNeill) are proposed.
The alpine tundra vegetation of Signal Mountain, Jasper National Park
Authors: Hrapko Julia O. , Roi George H. La
Published: May 2008

Signal Mountain forms the NW terminus of the Maligne Range in the Main Ranges E of the Continental Divide in the Canadian Rocky Mountains. The summer climate of the alpine zone on Signal is cooler and moister, with narrower temperature ranges, than that of Jasper townsite in the montane zone. Parent materials are Precambrian sandstones and conglomerates, with some siltstones and slates. Soils are Regosols, Brunisols, and Gleysols of pH 4.5 to 6.5. The alpine flora includes 157 vascular, 57 bryophyte, and 53 lichen species. Quantitative sampling of the major alpine community types (ct's) of Signal was followed by a 780-m transect study from the tree line on the dry, exposed SW slope to the tree line on the moist, protected NE slope. Dwarf shrubs predominate in most but not all ct's. Dryas octopetala is dominant in eight relatively xerophytic, lichen-rich, and chionophobous ct's where snow cover is shallow. Salix arctica, S. nivalis, Antennaria lanata. Carex nigricans, Cassiope tetragona, C. mertensiana, Phyllodoce glanduliflora, and Arctagrostis arundinacea are dominant or codominant in five relatively mesophytic and chionophilous ct's where snow cover is deeper and more persistent. The ct's and their habitats are described, compared on a community ordination, and their distribution and abundance are plotted on the alpine transect.
Relationship between occlusion of xylem elements and disease symptoms in leaves of cotton plants infected with Verticillium dahliae
Authors: Misaghi I. J. , DeVay J. E. , Duniway J. M.
Published: May 2008

The relationship between plugging of xylem elements and subsequent wilting, chlorosis, and necrosis of limited leaf areas was studied in cotton plants (Gossypium hirsutum L.) infected by Verticillium dahliae. In contrast with xylem elements which extended into nonchlorotic areas of infected leaves, the lumens of xylem elements extending into chlorotic areas of infected leaves were occluded with a dark brown substance, and the vessel walls were noticeably thickened. There was a positive correlation between the number of occluded xylem elements and the degree of chlorosis: among 72 infected leaves tested, the average percentage of occluded xylem vessels in veins extending into chlorotic areas and nonchlorotic areas of leaf blades were 28 and 6, respectively. These results suggest that regional chlorosis and necrosis of leaves of cotton plants infected by V. dahliae may be due to water stress created by localized plugging of xylem elements. When sections from midribs or petioles of leaves of healthy plants were placed in solutions of several enzymes or other substances, only methyl alcohol (2.5 × 10−5 M to 2.5 × 10−2 M) or pectin methyl esterase at 100 μg/ml caused browning and plugging of xylem vessels typically associated with wilt leaf symptoms of Verticillium wilt.
Typhula ishikariensis and its varieties, var. idahoensis comb.nov. and var. canadensis var.nov.
Authors: Årsvoll K. , Smith J. Drew
Published: May 2008

On genetical evidence Typhula FW, T. idahoensis Remsberg, and T. ishikariensis lmai should be considered as one species, and by priority the T. ishikariensis applied to it. Based on morphological characters the following taxonomic ranking is suggested: T. ishikariensis Imai var. ishikariensis, T. ishikariensis Imai var. idahoensis (Remsberg) comb.nov., T.ishikariensis Imai var. canadensis Smith & Årsvoll var.nov.Within this Typhula complex the latter two varieties differ most clearly morphologically, but are most closely related genetically. They are both found only in North America, while var. ishikariensis also occurs in Europe and Asia. Var. canadensis can be distinguished morphologically from the other two varieties by its smaller sclerotia and sporophores, by its more profuse production of aerial mycelium in culture, and the tendency of its sclerotia to be produced in bands, radial rows, and suspended in the aerial mycelium rather than in concentric rings. The only reasonably reliable way of separating the other two varieties is on sclerotial characters. Rind cells of var. idahoensis are more irregular in outline, with more lobate, occasionally digitate cells than var. ishikariensis.
Taxonomy of the tribe Triticeae (Poaceae) using various numerical taxonomic techniques. III. Synoptic key to genera and synopses
Authors: Baum Bernard R.
Published: May 2008

Synopses of genera of Triticeae (including Elymus trinii which is not classified within any genus here) were elaborated and are here documented. A generic classificatory key together with four auxiliary keys are also provided: these are not analytical keys normally found in most treatments whose purpose is to identify every case to taxon. The synopses and keys were generated by computer using Pankhurst's program for generating diagnostic keys. Canonical analyses were performed on the six groupings obtained previously from a numerical taxonomic classification of the genera of this tribe. Canonical loadings, to be used for placement of the OTUs and graphic separation of the groupings, are provided. This paper does not treat the multitude of natural and artificial hybrids.
Phosphoenolpyruvate carboxylase activity from Avena coleoptile tissue. Regulation by H+ and malate
Authors: Hill B. C. , Bown A. W.
Published: May 2008

Preparations of phosphoenolpyruvate (PEP) carboxylase activity from Avenu sativa coleoptile tissue were assayed by measuring the incorporation of labelled bicarbonate into a derivative of oxaloacetic acid or by coupling oxaloacetic acid production to malate dehydrogenase activity and the oxidation of NADH. Malate inhibition of PEP carboxylase activity was found to be noncompetitive, was not due to a mass action effect on the coupled enzyme system or to chelation of Mg2+, and probably involved direct inhibition of the enzyme by malate. Maximal PEP carboxylase activity was exhibited around pH 8.0 and increased 125% between pH 7.0 and pH 7.6. Inhibition by 4 mML-malate was virtually complete at pH 7.0 and decreased to 10% inhibition at pH 8. This information is discussed in the light of data which demonstrates that in response to IAA. coleoptile tissue accumulates malate and secretes H+. The regulatory properties of PEP carboxylase are consistent with a role in malate production which could resist increases in intracellular pH resulting from an auxin-stimulated H+ efflux.
Reproductive strategies and growth patterns in four legumes
Authors: Turkington R. A. , Cavers P. B.
Published: May 2008

The partitioning of dry matter into component plant parts has been traced for four legumes. The four species were chosen to represent different positions along the r-K continuum. Three of the species, Medicago lupulina, M. sativa, and Trifolium pratense, behaved essentially as predicted by r- and K-selection theory. However, the stolons of T. repens are formed within 7 weeks of germination and thus permit this species to reproduce sooner than Medicago lupulina can reproduce by seed. In this way, T. repens can behave as an r strategist in an environment imposing density-dependent regulation (a ‘K' type environment).
Spore release of some decay fungi of southern hardwoods
Authors: McCracken F. I.
Published: May 2008

Spore release was observed in eight decay fungi of southern hardwood near Stoneville, Mississippi. During June–September, daily spore release peaks of Irpex mollis, Fomes geotropus, F. rimosus, and Polyporus lucidus occurred in evening and those of F. everhartii and P. fissilis occurred at night. Means were 17–30 °C and 60% RH or higher during peaks. Afternoon peaks were also recorded for P. fissilis, P. sulphureus, and P. dryadeus from November to February when daily temperature was high (means = 10–16 °C) and RH decreased (means = 63–76%). Phenological data indicate that temperature is the most important periodic stimulus.
The mosses of Labrador, Canada
Authors: Brassard Guy R. , Weber David P.
Published: May 2008

A comprehensive review of the mosses of Labrador is presented, incorporating all previously published reports and much new data accumulated during field and herbarium studies since 1970. A total of 348 species of mosses are documented for Labrador, of which 40 are new to that region. Grimmia atrata is new to North America, and a major southern range extension is reported for Oligotrichum falcatum. Four species of 'copper mosses' occur together at Nachvak, northern Labrador. Illustrations of Mielichhoferia elongata and a large falcate form of M. mielichhoferi are presented, with comments on differentiating the two species. A preliminary bryogeographical analysis indicates that at least 75 moss species of southern affinity have their northern limit for eastern North America in Labrador, and a smaller number of predominantly arctic moss species have southern limits in Labrador.
Electron microscope study of vegetative cell division in two species of Marchanda
Authors: Fowke Larry C. , Pickett-Heaps Jeremy D.
Published: May 2008

Cell division in Marehantia polymorpha and M. berteroana was examined with the electron microscope. Distinct preprophase bands of microtubules, typical of higher plants, were not observed. Most of the spindle microtubules in early prophase appeared to insert into polar MTOC's. The behaviour of the nuclear envelope, nucleolus, and chromosomes was typical of higher plant divisions. Cytokinesis was accomplished by centrifugal cell plate growth in a phragmoplast. Numerous coated vesicles were associated with the developing cell plate.
Surgical studies on growth and xylem differentiation in the cotyledonary shoots of flax
Authors: Raju M. V. S. , Marchuk W. N. , Polowick Patricia L.
Published: May 2008

Growth and xylem differentiation in cotyledonary shoots were studied by partially isolating one shoot surgically in nondecapitated and decapitated flax plants (Linum usitatissimum var. noralta). Three types of cuts were made. The first type separated the shoot from the hypocotyl and the second from the epicotyl. The third type of cut was made at the node separating the two shoots, which, however, remained independently connected with the hypocotyl and epicotyl. In nondecapitated plants, the lateral shoots were inhibited. They had at their bases primary xylem strands, some of which were connected with the hypocotylary stele; the strands contained predominantly tracheids. In decapitated plants, the separated shoot grew vigorously when it was connected with both hypocotyl and epicotyl or hypocotyl alone. Such shoots contained at their bases abundant secondary xylem strands which were connected with the hypocotylary stele; the strands included predominantly vessels. The shoot that was isolated from the hypocotyl but connected with the epicotyl was inhibited even though it had abundant secondary xylem strands at its base. Results of this study suggest that growth of the cotyledonary shoot is dependent on the prior development of adequate xylem connections with the hypocotylary stele.
The development of cells in the coenocytic endosperm of the African blood lily Haemanthus Katherinae
Authors: Newcomb William
Published: May 2008

The endosperm of the African blood lily Haemanthus Katherinae Bak. follows the helobial pattern of development in which two chambers of endosperm are formed. In the earliest observed stage of development a large micropylar chamber and a smaller dome-shaped chalazal chamber of endosperm are present. Both are coenocytic and contain wall ingrowths of the transfer cell type along the embryo sac wall. Freely growing walls grow centripetally from the embryo sac wall, branch, and eventually meet, forming a layer of cells along the embryo sac wall. This process occurs first in the micropylar chamber. After four or more layers of endosperm cells are present, phragmoplasts form in association with karyokinesis and give rise to cross walls situated between the freely growing walls. When 10 or more layers of endosperm cells are present, free wall-less cells are present in the central vacuole near the edge of the cellular endosperm of the micropylar chamber. The free cells originate from mitosis of nuclei at the inner wall-less edge of the endosperm and the subsequent pinching off and release of the free cells into the large central vacuole. The free cells may undergo karyokinesis and become binucleate. The chalazal chamber of endosperm also becomes cellular by means of freely growing walls.
Structure and host–actinomycete interactions in developing root nodules of Comptonia peregrina
Authors: Newcomb William , Peterson R. L. , Callaham Dale , Torrey John G.
Published: May 2008

Correlated fluorescence, bright-field, transmission electron, and scanning electron microscopic studies were made on developing root nodules of Comptonia peregrina (L.) Coult. (Myricaceae) produced by a soil actinomycete which invades the root and establishes a symbiosis leading to fixation of atmospheric dinitrogen. After entering the host via a root hair infection, the hyphae of the endophyte perforate root cortical cells by local degradation of host cell walls and penetration of the host cytoplasm. The intracellular hyphae are always surrounded by host plasma membrane and a thick polysaccharide material termed the capsule. (For convenience, term intracellular refers to the endophyte being inside a Comptonia cell as distinguished from being intercellular, i.e.. between host cells, even though the former is actually extracellular as the endophyte is separated from the host cytoplasm by the host plasmalemma.) Numerous profiles of vesiculate rough endoplasmic reticulum (RER) occur near the growing hyphae. Although the capsule shows a positive Thiery reaction indicating its polysaccharide nature, the fibrillar contents of the RER do not, leaving uncertain whether the capsule results from polymers derived from the RER. Amyloplasts of the cortical cells lose their starch deposits during hyphal proliferation. The hyphae branch extensively in specific layers of the cortex, penetrating much of the host cytoplasm. At this stage, hyphal ends become swollen and form septate club-shaped vesicles within the periphery of the host cells. Lipid-like inclusions and Thiery-positive particles, possibly glycogen, are observed in the hyphae at this time. Associated with hyphal development is an increase in average host cell volume, although nuclear volume appears to remain constant. Concomitant with vesicle maturation, the mitochondrial population increases sharply, suggesting a possible relationship to vesicle function. The intimate interactions between host and endophyte during development of the symbiotic relationship are emphasized throughout.
In vitro culture of western red cedar (Thuja plicata). II. Induction of male strobili from vegetative shoot tips
Authors: Coleman Warren K. , Thorpe Trevor A.
Published: May 2008

Vegetative shoot tips of mature western red cedar (Thuja plicata Donn) were cultured on defined nutrient media. In the presence of high concentrations of various gibberellins, microsporangiate strobili were induced from the vegetative tips during an 8-week period under continuous illumination. No strobili were induced by GA3 under short-day (SD; 8-h photoperiod) conditions or continuous darkness. The ontogenetic stages of strobilus induction and development in culture were similar to those reported for intact plants. Prolonged culture produced externally mature male strobili. However, histological examination of the sporogenous tissues revealed either abortion of the tissues or an apparent arrest in early meiosis. Wide concentration ranges of either IAA or NAA in the presence or absence of 1 × 10−4 M GA3 did not qualitatively modify the early development of male strobili or induce female strobili, although 1 × 10−4M IAA completely inhibited induction of the male strobili by GA3. Benzylaminopurine or kinetin suppressed the induction of male strobili by GA3, while Ethrel or abscisic acid at the concentrations tested had no apparent qualitative effects on microsporangiate strobili formation.
The genus Suaeda (Chenopodiaceae) in Canada
Authors: Bassett I. J. , Crompton C. W.
Published: May 2008

The taxonomy of Suaeda spp. occurring in Canada has been studied. It is concluded that four species are present: Suaeda moquinii (Torrey) Greene, S. calceoliformis (Hook.) Moq., S. maritima L., and S. rolandii I. J. Bassett & C. W. Crompton sp.nov. Suaeda moquinii (2n = 18) is only known from the badlands of Saskatchewan and Alberta; S. calceoliformis (2n = 54) is widespread across Canada; S. maritima (2n = 36) is mostly present along the Atlantic coastline; S. rolandii (2n = 90) is found only in Quebec, New Brunswick, and Nova Scotia. Suaeda maritima spp. richii comb. nov. is rare in eastern Canada. Several names applied to these taxa are discussed.
Cell enlargement during leaf development in Catharanthus roseus
Authors: Nyman Leslie P. , Dengler Nancy G.
Published: May 2008

Cell enlargement and tissue differentiation have been examined using the leaf plastochron index (LPI) as a measure of developmental stage in Catharanthus roseus (L.) G. Don. Observations were made from plastic-embedded, 2-μm serial sections and measurements were made using a microprojector. At the earliest stages examined, six cell layers are present; periclinal divisions in the third abaxial layer give rise to seven cell layers at maturity. The initial six layers are similar in size, shape, and staining characteristics but palisade cells are slightly elongated. Relative rates of change in leaf length are high during early stages before LPI 1.0 whereas relative rates of change in leaf thickness increase after LPI 1.0 largely because of continuing high rates of change in palisade cell height. The predominant plane of enlargement in palisade mesophyll is perpendicular to the predominant plane of enlargement in spongy mesophyll. Relative rates of change in cell height in upper epidermis are higher than in lower epidermis throughout most of the period of development and absolute rates of change in cell size in upper epidermis are always higher than in lower epidermis. Formation of intercellular space in mesophyll seems well correlated with rates of change in cell width in developing dermal layers. These observations show how the rate, duration, and direction of cell expansion in each tissue type results in the histology of the mature leaf.
The characteristics of seasonal and ontogenetic changes in the tissue – water relations of Acer, Populus, Tsuga, and Picea
Authors: Tyree M. T. , Cheung Y. N. S. , MacGregor M. E. , Talbot A. J. B.
Published: May 2008

The Scholander–Hammel pressure bomb has been used to measure ontogenetic and seasonal changes in π0 (the osmotic pressure of the symplasm at zero water potential), πp (the osmotic pressure of the symplasm at ‘incipient plasmolysis’), εmax (the bulk elastic modulus near maximum turgor), and a number of other water relations parameters in single leaves of Acer saccharum and several species of Populus and in shoots of Tsuga canadensis and Picea abies. In newly emerged leaves of Acer, Populus, and Picea, π0, πp, and εmax are all small but rise rapidly with leaf development. These parameters stabilize at a maximum value or slowly increase with progress in season. In Acer, εmax declines shortly before senescence. In developing leaves, the water content reaches a maximum before the soluble solutes; this accounts for the low values of π0 and πp.In Tsuga π0 cycles through an annual maximum in winter and a minimum in summer. These changes may correlate with frost hardiness.
Structural studies of the development of infection structures of cowpea rust, Uromyces phaseoli var. vignae. I. Nucleoli and nuclei
Authors: Heath Michèle C. , Heath I. Brent
Published: May 2008

Light microscopical observations of living germ tubes and infection structures of cowpea rust were combined with an ultrastructural study to show that a nucleolus was present in the interphase nucleus at all stages of development from uredospore germination through to new uredospore formation. Vacuolate nucleoli were common in germ tubes but only nonvacuolate nucleoli were observed at other stages of fungal development. When grown on oil-containing collodion membranes, germinating uredospores, germ tubes, appressoria, and infection hyphae without haustorial mother cells all contained nucleoli composed primarily of nongranular material. Predominantly granular nucleoli were observed in developing uredospores and all parasitic stages in the leaf after the formation of the first haustorial mother cell. However, the fact that granular nucleoli were also seen in a membrane-grown infection hypha after haustorial mother cell formation suggested that the host was not required to stimulate the resumption of nucleolar activity. Electron-opaque patches, presumed to be condensed chromatin, were most prominent in the nucleoplasm of haustorial mother cells and virtually absent in germinating uredospores and germ tubes. The significance of this observation is discussed. A reduction in nuclear volume was observed in living material prior to cytokinesis in the appressorium and the substomatal vesicle. Evidence suggested that this reduction was produced by the expulsion of part of the nucleoplasm, plus the nucleolus, during mitosis rather than before as suggested for other rusts. Nuclei of haustorial mother cells and haustoria were also smaller than those in intercellular hyphae but the mechanism by which this was achieved could not be determined.