bluuebunny/crossref_metadata_2025 huggingface dataset:
Structures et composition élémentaire d'inclusions cristallines dans les grains protéiques cotylédonaires de Phaseolus vulgaris
Authors: Genevès Louis , Cachon Denis
Published: September 2007

The protein bodies of cotyledonary tissues of the dry seed of Phaseolus vulgaris contained numerous small globoids. Some minute crystals (0.1 μm) remained here and there, distinct in the nonstained ultrathin sections derived from samples fixed with glutaraldehyde. In the same parenchymatous sections, relatively thick, dark, alterable structures (one to a few micrometres) with no stable boundary were present. They appeared on the site of protein bodies. The nonfixed powders, derived from anhydrous cotyledonary tissues, showed many small globular crystals (0.1 μm), which were alterable, and also dark structures derived from the aggregation of crystal-like bodies which become alveolate. These two types were, respectively, similar to those observed in die sections. Dark thick crystals were also present; they were oblong or polyhedric and could be altered under irradiation. The elemental composition of these structures was defined with an electronic microprobe and X-ray spectrometry (Camebax apparatus). The minute crystals included in the globoids contained P and Ca; in some others, Mg or Fe was also detected. The dark, relatively thick structures contained P, Mg, and Ca, the latter being particularly abundant. The results were confirmed by microanalyses of the powders. The thick crystals, strongly calcified, also contained P and Mg.
Additions to the Mallomonas (Chrysophyceae) flora of Ontario, Canada, and a checklist of North American Mallomonas species
Authors: Nicholls K. H.
Published: September 2007

Twenty-three species and varieties of the chrysophyte Mallomonas (Mallomonadaceae) are reported from Ontario lakes and ponds. Identifications were based on electron microscopical details of siliceous scale and bristle structure and include seven taxa not previously reported from North America (M. peronoides (Harris) Momeu & Péterfi, M. alata f. hualvensis Asmund, Cronberg & Dürrschmidt, M. costata Durrschmidt, M. canina Kristiansen, M. pillula f. exannulata Harris, M. pumilio var. pumilio Harris & Bradley emend. Asmund, Cronberg & Dürrschmidt, M. pumilio var. munda Asmund, Cronberg & Dürrschmidt). Included also are several little-known species that have been reported only once or twice from North America. Mallomonas canina Kristiansen has many similarities with M. hindonii Nicholls and might be combined with it should examination of more material from other localities show there is a case for synonomy. Bristle structure, as a feature for distinguishing M. papilhsa var. papillosa from var. ellpsoidea, may no longer be supported since var. ellipsoidea bristles were found attached to var. papillosa scales. For consistency within the subgenus Mallomonopsis (sensu Asmund & Kristiansen 1986), the new combination Mallomonas bangladeshica (Tak. & Hay. emend. Wujek & Timpano) Nicholls comb.nov. is proposed. A listing of all North American reports of Mallomonas taxa (totalling 75) has been compiled. Of these, 66 Mallomonas species (and subspecies) have been reported from Ontario.
The chemotaxonomic significance of laricytrin and medicagenic acid in the tribe Trigonelleae
Authors: Jurzysta M. , Burda S. , Oleszek W. , Ploszynski M.
Published: September 2007

Flavonoids from fresh flowers of 35 species and medicagenic acid from leaf tissue of 44 species of the tribe Trigonelleae Schulz (Fabaceae) were examined using thin-layer chromatography. Moreover, medicagenic acid glycosides in the leaf tissue were also analyzed by the hemolytic test. Compounds tentatively identified as kaempferol, quercetin, myricetin, laricytrin, and medicagenic acid were present in hydrolysates of all species of the genus Medicago, including five species of debated taxonomic position, M. radiata, M. hybrida, M. cretacea, M. arborea, and M. lupulina. Laricytrin and medicagenic acid, while rarely occurring in the plant kingdom, may be regarded as chemical markers that distinguish the genus Medicago in Trigonelleae and may further support the placement of the five questionable species into Medicago. Laricytrin and medicagenic acid were also found in hydrolysates of three species of the section Buceras of the genus Trigonella (T. monantha, T. monspeliaca, and T. polyceratia) and were not found in any of the remaining tested species of Trigonella or in the genus Melilotus. This chemical affinity of the three Trigonella species to Medicago gives further support to the placement of these species in genus Medicago.
The vegetative structure of Medullosa endocentrica (Pteridospermopsida)
Authors: Hamer Jon J. , Rothwell Gar W.
Published: September 2007

A large suite of distinctive medullosan stems with attached branches, lateral buds, and leaves has been discovered in Upper Pennsylvanian sediments of the Appalachian basin. The specimens provide an opportunity to augment our knowledge of the vegetative structure of Medullosa endocentrica Baxter and to significantly expand the concept of the species. Stems are up to 2.3 cm in diameter and bear forking fronds with axillary branches or buds. This represents the first evidence for the mode of branching in medullosan pteridosperms. The stems have two vascular segments, each of which contains a sympodium of the eustele. Phyllotaxis approaches a 3/8 helix, and traces to each leaf diverge in a distinctive pattern over a distance of two internodes. Distal to the basal fork the fronds divide pinnately and bear pinnules that are most similar to Eusphenopteris. The uniformly slender stems, long internodes, consistent absence of attached adventitious roots, and delayed development of appendages below the stem apex provide evidence that M. endocentrica was a liana.
A new species of Bertia from China
Authors: Krug J. C. , Corlett Michael
Published: September 2007

Bertia sinensis sp.nov. is described and illustrated from Yunnan province, China. It is compared with B. moriformis var. latispora. The taxonomic position of Bertia is reviewed.
Morphological and anatomical development in the Vitaceae. II. Floral development in Vitis riparia
Authors: Gerrath Jean M. , Posluszny Usher
Published: September 2007

The anatomy, morphology, and ontogeny of the flowers of Vitis riparia are presented in this paper. The inflorescence is initiated as an uncommitted primordium, which in turn initiates a bract and then bifurcates to form inner and outer "arms." Both of the arms initiate inflorescence branches, first in a decussate pattern, then in a 2/5 phyllotactic spiral. These branches may initiate pairs of lateral primordia until a series of third- or fourth-order cymose inflorescence branches is initiated. Floral development begins when the calyx is initiated as three primordia, which first merge by meristem extension and then grow out to form an indistinctly five-toothed ring. The petals and stamens arise as five common primordia, alternating with the sepals. They divide into separate petal and stamen primordia. The gynoecium arises as a ring primordium. Two septae are initiated on the inner walls of the ring and grow together to form a two-loculed ovary. Two ovules arise from each septum. In male flowers the ovules form but do not mature, and the stigma and style fail to develop. The pollen is tricolporate. In female flowers the ovules are bitegmic and anatropous, the style is short, and the stigma is discoid or two parted. The pollen lacks furrows and pores. The yellowish disc arises from the base of the gynoecium and is more prominent in male flowers. The fruit is a one- to four-seeded bluish purple berry.
Ecological aspects of nitrogen fixation (acetylene reduction) associated with plants of a Minnesota wetland community
Authors: Eckardt Nancy A. , Biesboer David D.
Published: September 2007

Nitrogen fixation in association with four plant species of a Minnesota wetland, Typha latifolia L., Carex stricta Lam., Calamagrostis canadensis (Michx.) Beauv., and Lemna minor L., was estimated using the acetylene-reduction technique on soil – root cores. The estimated rates of nitrogen fixation (acetylene reduction) for plants growing in submerged soils, in kilograms per hectare per year, are T. latifolia, 0.91; Carex stricta, 0.47; Calamagrostis canadensis, 0.24; and L. minor, 1.90. Significantly higher fixation rates were found with plants growing in submerged areas than with those on the well-drained shore. These differences could not be correlated with differences in levels of extractable ammonium and nitrate in the substrate and were attributed to low redox potentials favoring nitrogenase activity in submerged areas. The seasonal trend in acetylene reduction activity appeared to be correlated with the reproductive stages of Typha, Carex, and Calamagrostis. Maximum acetylene reduction for these species was observed just after flower maturation, in early summer for Carex and Calamagrostis and late summer for Typha, suggesting that nitrogen fixation may be an important source of nitrogen in developing seeds. Overall, nitrogen fixation was estimated to supply as much as 11 kg N∙ha−1∙year−1 to this wetland community.
Enteroblastic first macroconidia in Fusarium crookwellense
Authors: Wyk P. S. Van , Venter E. , Wingfield M. J. , Marasas W. F. O.
Published: September 2007

The first conidium in Fusarium crookwellense can be produced enteroblastically following disintegration of the apex of the conidiogenous cell. Collarettes are morphologically distinct from those that arise when the first conidium develops from holoblastic replacement of the apex of the conidiogenous cell. Conidiogenous cell remnants may be present at the apex of the first conidium as a result of enteroblastic development.
Light and electron microscopical studies on Pseudoscourfieldia marina, a primitive scaly green flagellate (Prasinophyceae) with posterior flagella
Authors: Moestrup Øjvind , Throndsen Jahn
Published: September 2007

The supposedly primitive prasinophyte Pseudoscourfieldia marina has been established in culture and examined in detail. The cells swim by means of two unequal but parallel posterior flagella. Pseudoscourfieldia differs from other green flagellates in the structure of the flagellar root system, possession of a conspicuous leaflike attenuated extension from one basal body into the cell, the structure of the pyrenoid, which is invaginated by long extensions from the mitochondrial complex, and the structure of the scaly covering on the body. Pseudoscourfieldia shows distinct similarities to Nephroselmis, which is laterally biflagellate, and to the Tetraselmis group, which possesses four anterior flagella. The attachment of the hair scales on the flagella has been examined in detail for the first time in a green flagellate. The very short hair scales attach to the flagellar surface between each pair of longitudinal rows of scales known as Melkonian's rows, associated with the inside of every third scale in one row. This is probably a feature common to all prasinophytes with Melkonian's rows. Based on the many investigations now published, a classification for the prasinophytes, supposedly some of the most primitive green algae, is suggested. One class, two orders, and four families are recognized and defined, with 15 genera.
Characterization of plasma membrane bound cation-stimulated ATPase isolated from the roots of Cucumis sativus
Authors: Memon Abdul Razaque
Published: September 2007

A membrane fraction enriched with Mg2+- or Mn2+-dependent, monovalent cation stimulated ATPase was isolated from cucumber roots (Cucumis sativus L.) by an aqueous two-polymer phase system of Dextran T500 (6.5%, w/w) and polyethylene glycol (PEG) 3350 (6.5%, w/w) at pH 7.8. The ATPase activity associated with the upper PEG-rich fraction (plasma membrane) was characterized. The optimum pH for the activation by Mg2+ and Mn2+ was in the range 5.8–6.0. The activity was substrate specific for ATP. Kinetics with Mg2+ or Mn2+ followed a simple Michaelis–Menten relationship. The apparent Km for Mg2+ activation (0.60 mM) of the ATPase was about twice that of the apparent Km for Mn2+ (0.38 mM). ATPase was stimulated by monovalent cations and showed an order of cation preference of [Formula: see text]. Calcium inhibited the plasma membrane ATPase, apparently by a direct interaction with ATPase rather than by disrupting the MgATP2− complex.
The moss genus Dicranodontium (Dicranaceae) in Canada
Authors: Ireland Robert R.
Published: September 2007

A study of herbarium specimens of Dicranodontium was undertaken to facilitate the identification of the taxa present in Canada and to document their occurrence in the country. Keys, descriptions, illustrations, and distribution maps are provided for the four species in Canada, namely D. asperulum (Mitt.) Broth., D. denudatum (Brid.) Britt. in Williams, D. subporodictyon Broth., and D. uncinatum (Harv.) laeg. & Sauerb. One species, D. denudatum, has a disjunct distribution, being known from western British Columbia and southern Québec and Newfoundland. The other three species are known only from western British Columbia, predominantly the Queen Charlotte Islands. The rarity and restricted occurrence of these species is apparently due to the low sporophyte production resulting from the sterility of the majority of plants and to their preference for oceanic habitats. Only two species, D. asperulum and D. uncinatum, were seen with sporophytes.
Interactions of the nonhost French bean plant (Phaseolus vulgaris) with parasitic and saprophytic fungi. I. Fungal development on and in killed, untreated, heat-treated, or blasticidin S treated leaves
Authors: Fernandez Myriam R. , Heath Michèle C.
Published: September 2007

Germination, penetration, and subsequent growth of four saprophytic and five parasitic fungi nonpathogenic on French bean (Phaseolus vulgaris L. cv. Pinto) were examined on, or in, killed, untreated, and heat-treated or blasticidin S treated leaves in the presence (saprophytes only) or absence of additional nutrients. The saprophytes required either an external supply of nutrients or a diffusate from autoclaved leaves to germinate, and they subsequently did not attempt to penetrate untreated or heat-treated living leaves. In contrast, the parasites germinated well, and penetrated untreated tissue almost exclusively through stomata. For some parasites, preinoculation heat treatment increased the incidence of direct penetration and the degree of fungal growth in the tissue. The saprophytes and nonbiotrophic parasites all penetrated and grew well in leaves that had been killed by autoclaving or freezing. The data suggest that living, intact bean leaves are resistant to the fungal saprophytes tested because these fungi lack pathogenicity factors necessary for germination on, and penetration of, the leaf. Resistance to the parasites, in contrast, appears to reside in heat-sensitive and heat- or blasticidin S insensitive defenses in the leaf that may differ with the fungus.
Interactions of the nonhost French bean plant (Phaseolus vulgaris) with parasitic and saprophytic fungi. II. Fungal development after inoculation by injection or wounding
Authors: Fernandez Myriam R. , Heath Michèle C.
Published: September 2007

Germination and growth of four saprophytic and five parasitic fungi nonpathogenic on French bean (Phaseolus vulgaris L. cv. Pinto) were examined in leaves after the epidermis was bypassed by injection or wounding. In unheated leaves, only the parasites had the ability to spread from the wound site and to germinate and grow inside the tissue after injection. The saprophytes behaved similarly only after the leaves were given a preinoculation heat treatment, suggesting a sensitivity to heat-sensitive inhibitors. For two of the saprophytes, evidence for the presence of heat-insensitive inhibitors also was found. Unlike the intercellular growth following stomatal penetration, growth of all of the parasites was affected by heat-sensitive defenses once the epidermis was bypassed. The greater intercellular growth after injection as compared with stomatal penetration suggested that the guard cells play a significant role in the resistance of intact, unheated leaves to Cladosporium fulvum Cooke. Of the saprophytes examined, Neurospora crassa Shear & Dodge appeared to posses a number of attributes that might be considered as potential pathogenicity factors.
A synopsis of the genus Sanicula (Apiaceae) in eastern Canada
Authors: Pryer Kathleen M. , Phillippe Loy R.
Published: September 2007

A synopsis of the genus Sanicula in eastern Canada is presented. Four species and two varieties of these native woodland umbellifers are recognized. A key to the taxa, pertinent synonymy, comparative descriptions of diagnostic characters, and notes on the taxonomy, distribution, habitat, and rare status are provided. Illustrations of umbellet and fruit morphology, eastern Canadian dot maps, and North American range maps are also included for each taxon. The name S. canadensis L. var. grandis Fem. is revived, but it now represents a differently circumscribed taxon from that described by Femald. Sanicula odorata (Raf.) Pryer & Phillipe, which is neotypified here, must replace the long-accepted name S. gregaria E. P. Bicknell.
Effects of competition from shrubs on herbaceous wetland plants: a 4-year field experiment
Authors: Keddy Paul A.
Published: September 2007

While competition is known to occur among some species in some plant communities, we are not yet able to predict in which environments, or among which species, competitive interactions will be most intense. The objective of this study was to test for competition in a wetland plant community and then to determine which environments and which species were influenced by competition. The study site was the transition zone between shrubs and herbaceous plants on a lakeshore. To test for competitive release, shrubs were removed from treatment plots paired with controls in 25 sections of shoreline and cover of herbaceous species was monitored for 4 years. There were highly significant increases in cover, richness, and diversity in the removal plots, but less than one quarter of the individual species responded significantly. In general, these were small, partly evergreen species with high densities of buried seeds (e.g., Drosera intermedia, Hypericum boréale). On shores with frequent disturbance and low fertility there was no evidence for competitive release. The reduction in plant cover during a summer with high water levels suggests that lakeshores shift from abiotic to biotic structuring according to the water level in a particular year or series of years. Superimposed upon this is variation attributable to the type of shoreline and the type of species. Key words: competition, disturbance, exposure, lakeshores, Myrica gale, shrubs, wetlands, zonation.
Effect of the triazine herbicides Goltix and Igran on germination and growth of Aspergillus fumigatus, Fusarium oxysporum, Helminthosporium oryzae, and Verticillium agaricinum
Authors: Elwy E. E. A. , Osman M. , Rahman T. M. A. Abdel , Ismail I. M. K.
Published: September 2007

The effect of two triazines on spore germination, radial growth, and biomass production were studied in A. fumigatus, F. oxysporum, H. oryzae, and V. agaricinum. Igran inhibited spore germination of all species to some extent and at 1000 ppm completely inhibited spore germination in A. fumigatus and F. oxysporum. Goltix inhibited germination of F. oxysporum and H. oryzae, but stimulated germination of A. fumigatus and V. agaricinum. Germ tube length was significantly decreased at high herbicide concentrations. Both derivatives reduced radial growth rate as well as mycelial growth in liquid cultures. The level of inhibition depends on the herbicide, its concentration, and the fungal species.
Carex lacustris × C. trichocarpa (Cyperaceae), a new natural hybrid
Authors: Catling P. M. , Reznicek A. A. , Denford K.
Published: September 2007

The new natural hybrid Carex lacustris × C. trichocarpa is described from material found in southern Ontario and New York State. The plants are sterile with incompletely developed stamens and distorted pollen that failed to stain with lactophenol. The parentage is confirmed through intermediacy in distinctive morphological characters. The new hybrid possesses unique features of each parent including the red apices of the inner sheath bands of C. trichocarpa and the long ligules of C. lacustris. The flavonoid spectrum of the hybrid was found to be consistent with the proposed parentage. Luteolin glycosides were found only in C. lacustris, whereas tricin glycosides were restricted to C. trichocarpa. Although the hybrid had marker compounds from both putative parents, complementation was incomplete. The occurrence of this hybrid suggests that sedges with quite different chromosome numbers can and do form natural hybrids.
Microscopie de la mycoflore des aiguilles de Sapin blanc (Abies alba). IV. Décomposition de la cuticule, de l'hypoderme et de l'épiderme
Authors: Gourbière François , Pépin Régis , Bernillon Dominique
Published: September 2007

Degradation of protective tissues of coniferous needles (Abies alba Mill.) was examined by light and electron microscopy. Cuticle and hypodermis were destroyed at the beginning of the F1 stage, 1 year after needle fall. Hyphae from the superficial mycelium penetrated and colonized the cuticle, giving rise to numerous cavities throughout the cuticular layers. At the same time the cell wall of the hypodermis was invaded by soft rot fungi (type I) and hyphae grew within cavities within the secondary wall. During the F2 stage the epidermis was also destroyed by formation of cavities in the cell wall. At this time the remaining cuticle gave a typical wrinkled appearance to the needle surface. Hypotheses about the fungal species implicated in these activities are discussed. These processes do not affect residual cytoplasm of parenchyma cells and appear to be strongly different from white rot degradation of litter.
Spiniferomonas genuiformis and Spiniferomonas alata (Chrysophyceae): taxonomic implications of form variation
Authors: Nicholls K. H.
Published: September 2007

Spiniferomonas genuiformis Wujek and Bland, recently described as a new species from Florida, has been found in an Ontario freshwater pond. Its scale structure generally agrees well with that known for the type material, but considerable variation in the structure of the spine scales is described for the Ontario specimens. It is suggested that S. genuiformis may not be a valid species but a growth form of S. alata, since scales typical of those known for both "species" were found on individual cells.
Within and among plant variation in seed mass and pappus size in Tragopogon dubious
Authors: McGinley Mark A.
Published: September 2007

Individual seed mass of two seed morphs of Tragopogon dubious (L.) varied among plants and within and among flowering heads within individual plants growing near Salt Lake City, UT. Seeds of the light morph from the center of a receptacle were smaller than outer seeds, suggesting that variation in seed mass within heads was due to position effects. The total seed mass per head, seed number per head, and mean seed mass per head of both morphs declined in most plants over the season. Heads with larger total seed mass contained larger seeds both within and between plants so seasonal patterns in seed mass may be influenced by seasonal variation in the amount of resources available for investment in seeds. Seeds of the light colored morph had a greater dispersal potential than seeds from the dark colored morph because their disk loading was lower. Pappus size (both pappus radius and stalk length) increased with the number of seeds per head which may increase the efficiency of packaging fruits on the receptacle. Heads with a larger total seed mass allocated a smaller proportion of their resources to the dark seed morph which may serve to decrease the level of sibling competition experienced by the less dispersing seed morph. Thus, variation in investment in offspring may arise as a combination of developmental constraints and selection for variable investment.
Ecological relationships of wild rice, Zizania aquatica. 8. Classification of sediments
Authors: Day W. R. , Lee P. F.
Published: September 2007

Cluster and discriminant analysis classified sediments from potential and existing wild rice lakes into three major and three hybrid types. The three major sediment types were described as clay, organic, or flocculent, and the three hybrid types as organic – flocculent, organic – clay, or organic over clay. The major differences among the six sediment types were the percent loss-on-ignition, bulk density, phosphorus, cation, and pH values. Organic sediments were characterized by high phosphorus, cation, and loss-on-ignition values, and lower pH values. Clay sediments had the highest bulk density values, but were low in phosphorus. Flocculent sediments exhibited the lowest bulk density, phosphorus, and cation values, and the highest loss-on-ignition and pH values. The three hybrid sediment types had values for these variables intermediate to their parent types. Flocculent, clay, and organic–flocculent sediment types produced the lowest dry weights of individual wild rice plants. Best production (in terms of dry weight) occurred in organic, organic–clay, and organic over clay sediments that had loss-on-ignition values ranging from 29 to 49%, were slightly acidic (pH values of 5.9 −6.2), and had high phosphorus (> 1.0 g ∙ m−2) and cation values.
Comparative studies on myceliogenic germination of tan sclerotia of Sclerotinia sclerotiorum and Sclerotium rolfsii
Authors: Huang H. C. , Sun S. K.
Published: September 2007

Tan-colored sclerotia of Sclerotium rolfsii and of an aberrant strain of Sclerotinia sclerotiorum that were freshly harvested from 5-week-old cultures on potato dextrose agar or stored at room temperature in paper bags for 4 weeks germinated myceliogenically on moist field soil without exogenous nutrients. A comparative study by time-lapse photomicroscopy revealed similarity in the mode of myceliogenic germination of sclerotia of the two species. The germination appeared to be of the hyphal type in both species and was characterized by the emergence of individual hyphae through the rind. There was no evidence of eruptive type of germination in any of the strains tested. Although several hyphae often emerged through the same spot of the rind, these hyphae emerged singly, and the time-lapse photomicrographs showed no evidence of eruptive germination. While most of the germinated sclerotia of S. rolfsii developed into colonies within 4 days of incubation on moist soil, the development of colonies from germinating sclerotia of S. sclerotiorum appeared to be slow, taking up to 28 days. Results of the inoculation studies showed that mycelia from the germinated sclerotia of S. rolfsii were able to infect and cause seed rot and damping-off of canola and alfalfa, which were planted near the soil surface at a distance of at least 15 mm from the sclerotium, without providing exogenous nutrients.
Responses of arctic sedges to release from grazing: leaf elongation in two species of Carex
Authors: Kotanen P. M. , Jefferies R. L.
Published: September 2007

We have used demographic methods to determine whether increased rates of leaf elongation occur in two sedges, Carex subspathacea Wormsk. and Carex × flavicans Nyl., when heavily grazed by Lesser Snow Geese (Chen caerulescens caerulescens (L.)) at La Pérouse Bay, Manitoba. Rates of elongation of leaves declined as leaves aged. Most comparisons between grazed and ungrazed plots indicated that rates of elongation of leaves of grazed shoots were not significantly greater than corresponding rates for ungrazed shoots. No trends were evident. As reported elsewhere, increased production and turnover of leaves accounted for most of the regeneration of photosynthetic area following grazing in both species.
Paraveinal mesophyll, and its relationship to vein endings, in Solidago canadensis (Asteraceae)
Authors: Lersten Nels R. , Brubaker Curt L.
Published: September 2007

Paraveinal mesophyll is described from leaves of a common goldenrod species, Solidago canadensis L. (tribe Astereae). This is the first report of paraveinal mesophyll from the Asteraceae. It is a uniseriate middle layer consisting of horizontally lobed cells that form a lacy meshwork between veins. It abuts the tightly cylindrical bundle sheath at the level of the xylem in all vascular bundles. Vein endings, however, differ from other vascular bundles in two ways: sieve tube members may extend to the vein tip, end at an intermediate point, or be absent, and lateral bundle sheath cells distal to the terminal sieve tube member swell greatly or protrude horizontally and interdigitate with adjacent paraveinal mesophyll cells. Cells of both paraveinal mesophyll and bundle sheath have fewer and smaller chloroplasts than other mesophyll cells; the chloroplasts mostly lie adjacent to intercellular spaces. During leaf development, the paraveinal mesophyll layer differentiates before other mesophyll layers. Solidago canadensis paraveinal mesophyll resembles the well-studied paraveinal mesophyll of Glycine max, except for differences in its anatomical relationship to minor veins and vein endings.
Wind dispersed seeds and plant recovery on the Mount St. Helens debris avalanche
Authors: Dale Virginia H.
Published: September 2007

Seed dispersal and plant establishment were monitored for 4 years on the debris avalanche created by the 1980 eruption of Mount St. Helens. The number of plants on the deposit increased over time to a high of almost 2 plants/m2 by 1983. The number of species per 250-m2 plot has increased to a mean of 10.3 in 1983 with 76 species being present over the entire deposit. Four years after the eruption only 30% of the species present before the eruption had reestablished themselves, and average plant cover was less than 1%. The debris avalanche has been invaded primarily via wind-dispersed seed of early successional species that survived or have become established in adjacent disturbed areas. Most of the early successional species on the avalanche have plumed seeds that are adapted not only for long distance dispersal, but also for being trapped in wet areas or by spider webs. Fluctuations in the density of seeds dispersed to the deposit were related to variation in precipitation. Neither seed abundance nor plant density correlated with absolute distance to a seed source or soil texture conditions. Colonization patterns are more influenced by the available biota and prevailing climate conditions than by substrate alterations resulting from the eruption.
Polythetic generic separation in tribe Trifolieae subtribe Trigonellinae (Leguminosae)
Authors: Small Ernest
Published: September 2007

Numerical taxonomic studies were conducted on 164 species, including all of Medicago and Melilotus and most of Trigonella, the three genera of subtribe Trigonellinae, in order to clarify generic circumscription. The suite of 54 traditionally employed characters studied proved to be polythetic for all groupings of interest, i.e., no subset of individually fully discriminating characters was present, although the suite could be used collectively for discrimination. Medicago proved to be quite distinctive from Melilotus, but not from Trigonella. It was recently found that 51 species traditionally placed in Medicago and 32 species commonly excluded from this genus (and often placed in Trigonella) shared without exception a number of chemical, floral and seed characters, not studied here. That is, all of these 83 species can be assigned to Medicago, which is accordingly defined monothetically. In the present study it was found that characters used traditionally to circumscribe Medicago (with 51 species) by general morphological trends (i.e., polythetically) can also be used, although somewhat less effectively, to circumscribe Medicago in the broad sense (with 83 species). Therefore, prior to the recent discovery of characters that define Medicago monothetically, this genus was defineable only by general morphological trends, and these trends favored the narrower circumscription rather than the broader one now known to be justified. Variation between Trigonella and Melilotus also proved to be gradualistic for the characters studied. Unlike the Medicago–Trigonella problem, however, there are presently no known sets of individually diagnostic characters by which the continuum of variation should be split. These two genera are (arbitrarily) distinguishable as presently circumscribed, only tradition preventing the adoption of alternative, equally defensible ways of segregating them, or indeed of combining them. The study of Trigonella produced groupings essentially identical to the 12 sections of the classical monographer, Sirjaev, and clarified the relationships of several species. The study of Melilotus separated annuals and perennials, corresponding to the subgenera of the classical treatment of Schulz, but failed to reflect his sectional taxonomy. Melilotus bicolor is much closer to what is presently conceived of as Trigonella than to Melilotus.
A note on Trigonella (Melilotus) bicolor
Authors: Small Ernest , Jomphe Marcel
Published: September 2007

Melilotus bicolor Boiss. & Bal. in Boiss. was recently transferred to the genus Trigonella as T. bicolor (Boiss. & Bal. in Boiss.) Lassen. This note reviews the basis for this transfer, and provides the first illustrations and detailed description of this very poorly known, rare species.
Cytotaxonomic studies in Iberian, Balearic, North African, and Macaronesian species of Carex (Cyperaceae). II
Authors: Luceño Modesto
Published: September 2007

Meiotic studies on 26 taxa, including two hybrids, of the genus Carex are presented. Results obtained with the hybrid between Carex remota and Carex paniculata ssp. lusitanica were remarkable, since they showed a great number of configurations and even different chromosome numbers in metaphase I. The karyology of the Carex muricata group in the SW of Europe was studied for the first time. I also performed the first studies on the karyology of two species belonging to section Carex in the SW of Europe, namely Carex hirta, which gave the highest chromosome number reported so far for the genus Carex (2n = 114), and Carex lasiocarpa Erhr., for which I found a putative triploid whose chromosome number (2n = 78–85) was not constant in metaphase I. Agmatoploidy seems to be the most important process involved in the cytogenetic evolution of the species studied here. The idea of the existence of "fragile points" in the chromosomes is suggested to explain the formation of bivalents upon chromosome breakage. In addition, the chromosome number for Carex canariensis is reported here for the first time. Key words: Carex, Cyperaceae, cytogenetics, western Mediterranean.
The rotated-lamina syndrome. V. Partial lamina rotation and related features in Hamamelidaceae
Authors: Charlton W. A.
Published: September 2007

Shoots of Hamamelidaceae have been examined for the presence of the rotated-lamina syndrome, a condition in which young leaves in bud face towards one side of the shoot (normally the upper) rather than towards their own shoot apex. Early leaf development and bud organisation have been examined in representatives of eight genera with dorsiventral shoots and distichous phyllotaxis, and of four genera with radially symmetrical shoots and spiral or decussate phyllotaxis. Radially symmetrical shoots do not show any evidence of the syndrome. The distichous Corylopsis and Hamamelis species studied have leaf primordia that are asymmetrical from an early stage and show partial lamina rotation, the lamina facing obliquely towards the upper side of the bud. Mature laminae are usually asymmetrical. In Corylopsis rotation arises by torsion in the petiole region, and in Hamamelis by asymmetrical growth of the leaf base. Distichous examples without lamina rotation also have asymmetrical primordia in most cases, often have asymmetrical leaves, and all show the same asymmetrical development of the leaf base as found in Hamamelis. It is suggested that these features represent either (i) relics of rotated-lamina syndrome that was present in these cases but has been suppressed or (ii) early stages in evolution of rotated-lamina syndrome. It is suggested that suppression is the more likely interpretation. Corylopsis and Hamamelis may also be in the process of suppressing the syndrome. Key words: Hamamelidaceae, leaf, development, dorsiventrality, lamina rotation.
Bundle sheath and mesophyll cell differentiation in the C4 dicotyledon Atriplex rosea: quantitative ultrastructure
Authors: Liu Youqi , Dengler Nancy G.
Published: September 2007

In leaves of most C4 species, both bundle sheath and mesophyll cells are derived from ground meristem, yet at maturity differ in photosynthetic enzyme complement and in cell size, shape, and subcellular ultrastructure. This quantitative ultrastructural study of bundle sheath and mesophyll cell differentiation in Atriplex rosea shows that while developmental pathways of bundle sheath and meosphyll cells are generally coordinated, the timing of developmental divergence differs among individual characteristics. For instance, bundle sheath cells are larger, with more chloroplasts and more and larger mitochondria by 8 days after leaf emergence, while differential growth of mesophyll cell chloroplast peripheral reticulum and increase in thylakoids per granum in bundle sheath chloroplasts do not develop until after 12 days. Multigroup principal components analysis (M-PCA) of the data emphasizes that the greatest source of variation is overall size change as both cell types expand. M-PCA also identifies patterns of allometry within the data; for instance, mesophyll cell vacuoles and chloroplast peripheral reticulum undergo greater relative growth than do bundle sheath microbody area and number. The greater structural specialization of bundle sheath cells is reflected in higher growth rates from the time of divergence, but developmental change in both cell types continues until leaf expansion is complete. Most structural changes occur substantially after the stage of cell-specific expression of C4 enzymes. Key words: bundle sheath, mesophyll, C4 photosynthesis, leaf development, Atriplex rosea, multigroup principal components analysis.
Comparative leaf development of juvenile and adult Pseudopanax crassifolius
Authors: Clearwater Michael J. , Gould Kevin S.
Published: September 2007

We describe and compare leaf development in juvenile and adult shoots of Pseudopanax crassifolius, a strongly heteroblastic tree native to New Zealand. The shoot apical meristem is significantly larger in adult plants than in juvenile plants. Leaf primordia of the two forms are morphologically comparable at inception. The allometry of leaf length and width is similar in both forms up to a length of 7 mm. However, a shape index based on the relative position of maximum leaf width indicates that their morphology diverges when leaf primordia are 300 μm long. Laminae are initiated when the leaf primordium is shorter in adult shoots than in juvenile shoots. Maturation processes of the two leaf forms are similar. Cells and tissue types expand and differentiate in an acropetal direction. When leaf length, expressed as a proportion of mature leaf length, is used as a developmental index, the timing of all stages of leaf differentiation is comparable for the two leaf forms. The juvenile form is considered to be derived from the adult form by accelerated growth of the primordial leaf axis. Key words: Pseudopanax crassifolius, heteroblasty, leaf shape, development, allometry, New Zealand.
Ectopic formation of trichomes and stomata in floral organs of Arabidopsis thaliana induced by thidiazuron
Authors: Venglat S. P. , Sawhney V. K.
Published: September 2007

Thidiazuron (TDZ), a urea derivative, was applied to the inflorescences of Arabidopsis thaliana at early stages of development to study its effect on flower development. Scanning electron microscope observations revealed that TDZ induced the formation of branched trichomes on sepals and carpels and stomata on petals that are not normally produced on these organs. Concurrently, TDZ also suppressed the development of pollen grains in the anthers and ovules in the ovaries. In addition, TDZ induced an increase in the size of all the floral organs except stamens. These observations suggest that thidiazuron alters the differentiation processes in floral organs by inducing the production of traits that are characteristic of cauline leaves, i.e., trichomes and stomata. Key words: Arabidopsis thaliana, flower development, stomata, thidiazuron, trichomes.
Variation and integration in the rare grass Achnatherum (Oryzopsis) hendersonii: phenotypic comparison with parapatric common congeners
Authors: Rapson G. L. , Maze Jack
Published: September 2007

Phenotypic properties indicating levels of variation and integration were compared among three populations of a rare bunch grass, Achnatherum (Oryzopsis) hendersonii (tribe Stipeae), and one parapatric population of each of its common relatives Achnatherum (Stipa) lemmonii and Achnatherum (Stipa) thurberiana, sampled from the Colockum Pass area of central Washington, U.S.A. Twenty-five randomly selected plants from each population were measured for both vegetative and spikelet features. The vegetative features were represented by morphometric measurements taken from one leaf on a tiller and the flag leaf on a flowering culm. The spikelet features were based on two to eight spikelets per plant. The three data sets were analyzed separately to compare population level variation both among individuals and among variables (variable covariation). Phenotypic variation among individuals is lowest for A. hendersonii in estimators of both size and shape; within-individual phenotypic variation, as evaluated through among-variable correlation coefficients, is highest for A. hendersonii and lowest for A. thurberiana. The lower level of among-individual variation for A. hendersonii is consistent with biological beliefs about rare species; its higher among-variable variation may indicate less precise control of integration. Key words: rarity, morphological variation and integration, Poaceae, Achnatherum.
Web bearing resistance of W-shape beams framing over columns
Authors: Liu Y , Tang Q
Published: September 2007

The effect of cap plate thickness on the web behavior and resistance of W-shape steel beams framing over HSS columns is studied experimentally and analytically. Experimental and numerical results reveal that an increase in cap plate thickness results in increased web capacity. The degree of strength increase with cap plate thickness is higher for slender webs than for stockier webs. For long beams whose compression flanges reach yield in bending, a 38 mm cap plate is adequate to obtain the web strength specified in the current Canadian steel design code for relatively stocky webs. For slender webs, a simple analysis assuming uniform stress distribution underneath the cap plate results in an adequate cap plate. Key words: W shape, web bearing, web crippling, column loading, cap plate, elastic-plastic analysis, geometric imperfection.
Glass frit for concrete structures: a new, alternative cementitious material
Authors: Laldji Said , Tagnit-Hamou Arezki
Published: September 2007

With today's requirements for high-performance concrete, mix proportions containing cementitious materials as partial replacement of, or in addition to, Portland cement, are being used more frequently. The most commonly used cementitious materials nowadays are fly ash, silica fume, and ground, granulated blast-furnace slag. However, alternative supplementary cementitious materials can successfully be used as long as they meet the acceptance criteria stated in various specifications. This paper provides data on properties of structural concrete containing glass frit. The performance of this type of concrete is highlighted by its rheological and mechanical behaviour, as well as its durability. Later-age compressive, splitting tensile, and flexural strengths are well above estimated values, and in many cases, are higher than those obtained with the control concrete. Durability aspects and characteristics expressed by drying shrinkage, surface scaling, and chloride-ion permeability have shown that concrete incorporating glass frit has a very good potential for long-term resistance.Key words: glass frit, cementitious material, workability, mechanical properties, durability.
Development of a new class of precast concrete pipes - an experimental evaluation
Authors: Naggar H El , Allouche E N , Naggar M H. El
Published: September 2007

Concrete pipes represent the backbone of the municipal storm and wastewater collection systems of Ontario, Canada. Industry and academia partnered on a research effort that aimed at developing new precast-concrete pipe products that provide added value to the final user in comparison with existing products. This paper describes a full-scale experimental evaluation of the design, manufacturing, and performance aspects of a "cellular" concrete pipe, a precast concrete pipe in which multiple continuous conduits were incorporated within its wall. Two fully-instrumented prototype segments of the proposed cellular concrete pipe were manufactured using standard dry-cast manufacturing procedures. The pipe segments were subjected to a D-load test to evaluate their structural performance. The observed structural performance was found to be comparable to solid-wall specimens, particularly when a four-conduit configuration was used. Of the six materials used as conduits, PVC and aluminum were found to perform the best. The presence of the conduits appears to delay the on-set of major cracks, thus increasing the D-load value. Key words: precast, concrete, pipe, experimental, conduit system, trenchless construction methods.
Parameters governing the response of under-deck cable-stayed bridges
Authors: Ruiz-Teran A M , Aparicio A C
Published: September 2007

In the past quarter century, a number of bridges have been built that do not fit into the conventional types of cable-stayed bridges. These are under-deck cable-stayed bridges and combined cable-stayed bridges. In this paper we define the first of these two types and set out its mechanisms of response. We then establish and analyze the parameters that determine the permanent response and the response to live load of these bridges. Lastly, we draw conclusions relating to their behaviour and define design criteria for them with the aim of making cable-staying systems highly efficient and allowing the design of much lighter and slimmer structures.Key words: unconventional cable-stayed bridges, under-deck cable-stayed bridges, combined cable-stayed bridges.
Use of steel slag aggregate in asphalt concrete mixes
Authors: Asi Ibrahim M , Qasrawi Hisham Y , Shalabi Faisal I
Published: September 2007

There are three major steel-manufacturing factories in Jordan. All of their by-product, steel slag, is dumped randomly in open areas, causing many environmentally hazardous problems. This research was intended to study the effectiveness of using steel slag aggregate (SSA) in improving the engineering properties of locally produced asphalt concrete (AC) mixes. The research started by evaluating the toxicity and chemical and physical properties of the steel slag. Then 0%, 25%, 50%, 75%, and 100% of the limestone coarse aggregate in the AC mixes was replaced by SSA. The effectiveness of the SSA was judged by the improvement in indirect tensile strength, resilient modulus, rutting resistance, fatigue life, creep modulus, and stripping resistance of the AC samples. It was found that replacing up to 75% of the limestone coarse aggregate by SSA improved the mechanical properties of the AC mixes. The results also showed that the 25% replacement was the optimal replacement level. Key words: steel slag aggregate, asphalt concrete, Superpave, indirect tensile strength, fatigue, rutting, creep.