bluuebunny/crossref_metadata_2025 huggingface dataset:
Underwater localization of pure tones by harbor seals (Phoca vitulina)
Authors: Bodson Anaïs , Miersch Lars , Dehnhardt Guido
Published: September 2007

The underwater sound localization acuity of harbor seals (Phoca vitulina) was measured in the horizontal plane. Minimum audible angles (MAAs) of pure tones were determined as a function of frequency from 0.2to16kHz for two seals. Testing was conducted in a 10-m-diam underwater half circle using a right/left psychophysical procedure. The results indicate that for both harbor seals, MAAs were large at high frequencies (13.5° and 17.4° at 16kHz), transitional at intermediate frequencies (9.6° and 10.1° at 4kHz), and particularly small at low frequencies (3.2° and 3.1° at 0.2kHz). Harbor seals seem to be able to utilize both binaural cues, interaural time differences (ITDs) and interaural intensity differences (IIDs), but a significant decrease in the sound localization acuity with increasing frequency suggests that IID cues may not be as robust as ITD cues under water. These results suggest that the harbor seal can be regarded as a low-frequency specialist. Additionally, to obtain a MAA more representative of the species, the horizontal underwater MAA of six adult harbor seals was measured at 2kHz under identical conditions. The MAAs of the six animals ranged from 8.8° to 11.7°, resulting in a mean MAA of 10.3°.
Measuring fish abundance in a weir trap using an acoustical-optical platform
Authors: Miksis-Olds Jennifer L. , Stokesbury Kevin D. E.
Published: September 2007

Data recorded by a bottom mounted survey platform deployed within the opening of a fishing weir were used to calculate species specific abundance estimates for comparison to the weir catch. Abundance estimates were calculated from the combination of sonar and video information recorded by the Acoustical-Optical Platform (AOP). Echo counting was used to detect individual moving targets in the sonar images with the application of a background removal technique utilizing a moving average filter. Video images provided species identification of acoustic targets. Video images and differences in target strength distributions reflected a change in dominant species from each deployment which was confirmed with the weir catch. The algorithm used to calculate AOP abundance estimates was most accurate in predicting abundance for species comprising at least 13% of the overall catch by weight. Close agreement between the species specific AOP estimates and absolute abundances of each species suggests that the combination of acoustic and video data is a powerful combination for accurately identifying fish species and predicting abundance.
Nonlinear shear wave interaction in soft solids
Authors: Jacob Xavier , Catheline Stefan , Gennisson Jean-Luc , Barrière Christophe , Royer Daniel , Fink Mathias
Published: September 2007

This paper describes nonlinear shear wave experiments conducted in soft solids with transient elastography technique. The nonlinear solutions that theoretically account for plane and nonplane shear wave propagation are compared with experimental results. It is observed that the cubic nonlinearity implied in high amplitude transverse waves at f0=100Hz results in the generation of odd harmonics 3f0, 5f0. In the case of the nonlinear interaction between two transverse waves at frequencies f1 and f2, the resulting harmonics are fi±2fj(i,j=1,2). Experimental data are compared to numerical solutions of the modified Burgers equation, allowing an estimation of the nonlinear parameter relative to shear waves. The definition of this combination of elastic moduli (up to fourth order) can be obtained using an energy development adapted to soft solid. In the more complex situation of nonplane shear waves, the quadratic nonlinearity gives rise to more usual harmonics, at sum and difference frequencies, fi±fj. All components of the field have to be taken into account.
Outer hair cell active force generation in the cochlear environment
Authors: Liao Zhijie , Feng Shengran , Popel Aleksander S. , Brownell William E. , Spector Alexander A.
Published: September 2007

Outer hair cells are critical to the amplification and frequency selectivity of the mammalian ear acting via a fine mechanism called the cochlear amplifier, which is especially effective in the high-frequency region of the cochlea. How this mechanism works under physiological conditions and how these cells overcome the viscous (mechanical) and electrical (membrane) filtering has yet to be fully understood. Outer hair cells are electromotile, and they are strategically located in the cochlea to generate an active force amplifying basilar membrane vibration. To investigate the mechanism of this cell’s active force production under physiological conditions, a model that takes into account the mechanical, electrical, and mechanoelectrical properties of the cell wall (membrane) and cochlear environment is proposed. It is shown that, despite the mechanical and electrical filtering, the cell is capable of generating a frequency-tuned force with a maximal value of about 40pN. It is also found that the force per unit basilar membrane displacement stays essentially the same (40pN∕nm) for the entire linear range of the basilar membrane responses, including sound pressure levels close to hearing threshold. Our findings can provide a better understanding of the outer hair cell’s role in the cochlear amplifier.
Time-reversal focusing of elastic surface waves with an asymmetric surface layer
Authors: Norville Pelham D. , Scott Waymond R.
Published: September 2007

The effectiveness of time-reversal focusing is evaluated in the presence of an asymmetric surface layer that changes the direction of the propagating waves, but does not continually scatter or block the propagating wave front. Interactions between the wave front and the surface layer are dependent on the depth and material properties of the asymmetric surface layer and its orientation in the medium with respect to the incident wave. Time-reversal focusing is shown to perform significantly better than other excitation methods for the purpose of delivering energy to the location of a buried land mine.
Synthesis, Oxidation and Photophysical Properties of Novel Derivatives of Acyclic Aromatic Amines
Authors: Kósa Csaba , Mosnáček Jaroslav , Bílešová Adela , Kasák Peter , Kronek Juraj , Danko Martin , Kollár Jozef
Published: September 2007

Conjugated acyclic arylamine derivatives, N-(4-methylphenyl)-N-(2-methyl-1-phenylpropyl)amine and N-(4-methoxyphenyl)-N-(2-methyl-1-phenylpropyl)amine, have been synthesized and characterized. Their photophysical properties have been investigated in polar methanol and non-polar cyclohexane solutions, and in PS and PMMA polymer matrices. The influence of the environment polarity as well as of the substituent in para-position of the aryl on the absorption, emission spectra and the fluorescence quantum yield has been studied. In the absorption and emission spectra, the observed absorption and emission band maxima were red shifted and the observed quantum yield was higher in the polar solution in comparison with the non-polar solution or polymer matrices. The distance of short- and long-wavelength absorption maxima in the methoxy derivative was larger and the emission band was red shifted in comparison with the methyl derivative. Chemical and photochemical oxidation of the prepared amines gives unstable nitroxides. High intramolecular quenching was observed in polymer matrix after photochemical oxidation of the amines.
Kinetics of Glycerol Biotransformation to Dihydroxyacetone by Immobilized Gluconobacter oxydans and Effect of Reaction Conditions
Authors: Raška Jiří , Skopal František , Komers Karel , Machek Jaroslav
Published: September 2007

Biotransformation of glycerol to 1,3-dihydroxyacetone was carried out in an isothermal isochoric batch reactor with Gluconobacter oxydans immobilized in poly(vinyl alcohol) gel capsules. The reaction course was described with a three-step kinetic model. Two reaction schemes were proposed and compared with 8 kinetic experiments at 25 °C. The experimental dependences of glycerol and dihydroxyacetone concentrations on reaction time were simulated very well by the autocatalytic model. The effects of reaction temperature and initial concentrations of yeast extract and glycerol were studied. Temperature 25-30 °C, initial yeast extract concentration 2-4 g l-1 and initial glycerol concentration 20-50 g l-1 were found as optimal. The determined rate constants can be used to advantage for industrial production of dihydroxyacetone from glycerol.
Rehydration of Calcined Mg-Al Hydrotalcite in Acidified Chloride-Containing Aqueous Solution
Authors: Kostura Bruno , Kovanda František , Valášková Marta , Leško Juraj
Published: September 2007

The rehydration of periclase-like Mg-Al mixed oxide obtained by calcination of hydrotalcite- like precursor with a Mg/Al molar ratio of 2 was carried out in KCl-HCl solutions at various pH and constant concentration of Cl-. A buffer equilibrium accompanied by leaching out of Mg2+ cations from the solid was observed during rehydration, when reconstruction of the layered hydrotalcite structure takes place. With increasing HCl concentration in the rehydration solution, the Mg/Al molar ratio in the obtained solid gradually decreased from about 1.5 to 0.3. An anomaly was found, when the increasing concentration of acid resulted in increasing pH of final solution. The XRD measurements showed that the initially formed hydroxide form of hydrotalcite is transformed into randomly interstratified forms of the Mg-Al hydroxide hydrate/Mg-Al chloride hydroxide hydrate, which are accompanied by the release of OH- anions into solution. The crystalline structure of rehydrated product decreased as Mg2+ cations were released into solution, which was accompanied by incorporation of Cl- into the solid.
Morphological and anatomical development in the Vitaceae. I. Vegetative development in Vitis riparia
Authors: Gerrath Jean M. , Posluszny Usher
Published: September 2007

The vegetative development of natural populations of Vitis riparia is reported in detail for the first time, using a combination of three-dimensional and histological techniques. The initiation of both uncommitted primordia (which can develop into either inflorescences or tendrils) and leaf primordia is documented and correlated with their position in the primordium initiation cycle. There are four possible states: (i) a leaf at a lower tendril node, which arises on the flank of a dome-shaped apex directly above a leaf; (ii) a leaf at either an upper tendril node or a tendrilless node, which arises on the flank of a broad apex directly above a tendril; (iii) a lower uncommitted primordium, which arises very high on the apical flank, separated from the subjacent leaf by the initiation of one primordium on the opposite side of the apex; and (iv) an upper uncommitted primordium, which arises on the apical flank, separated from the subjacent leaf by the initiation of two primordia on the opposite side of the apex. This study shows that there is evidence to support the view that the uncommitted primordium is both terminal and lateral. We have extended the reports of the presence of tendril hydathodes in Vitis to this species. Axillary bud initiation and development are the same as has been reported for other species of Vitis, with each winter bud being initiated in the axil of the basal prophyll of the previous one.
Cadmium alters the growth of the ectomycorrhizal fungus Paxillus involutes: a new growth model accounts for changes in branching
Authors: Darlington Alan B. , Rauser Wilfried E.
Published: September 2007

Cadmium reduced the growth rate of Paxillus involutus in pure cultures either on agar or liquid medium. On Cd-containing agar most of the mycelium grew submerged rather than on the surface as occurs on Cd-free agar. Cadmium increased hyphal density by both increasing the number of laterals at a branch point and decreasing the distance between branch points. These variables were included in a new model to determine the specific growth rate on the basis of mycelial length for the fungus growing on agar. The degree to which Cd reduced the specific growth rate was the same whether based on mycelial length from agar plates according to the new model or on mycelial mass from a liquid medium. The new model for specific growth rate (length) derived from agar cultures is particularly suited to those situations where a growth-modifying agent alters the branching frequency and the distance between branch points.
Long-term effects of 2,4-D application on plants. II. Herbicide avoidance by Chenopodium album and Thlaspi arvense
Authors: Hume Larry
Published: September 2007

Research plots in a wheat–wheat–fallow rotation at Indian Head, Sask., were sprayed annually with 2,4-dichlorophenoxy-acetic acid (2,4-D) for 36 consecutive years. Two species susceptible to 2,4-D, Chenopodium album L. and Thlaspi arvense L., were dominant in these plots. From 1981 to 1983, C. album and T. arvense seedlings that emerged during four periods of the growing season were marked and their mortality, seed production, and size recorded. From these data and other studies, 10 ways in which C. album and T. arvense managed to survive herbicide application were identified. These are intermittent germination, herbicide tolerance, small size of late-emerging seedlings, short life cycle, hardiness, failure of control practices, long-term dormancy, seed dispersal, viability of immature seeds, and winter annual life cycle of T. arvense.
Numbers and distribution of apothecia of Sclerotinia sclerotiorum in relation to white mold of white bean (Phaseolus vulgaris)
Authors: Boland G. J. , Hall R.
Published: September 2007

Relationships between the distribution and numbers of apothecia of Sclerotinia sclerotiorum (Lib.) de Bary and the distribution and incidence of white mold of white bean (Phaseolus vulgaris L.) were investigated in a field plot at Arkell, Ont., in 1981 and 1982. The spatial distributions of both apothecia and disease were aggregated and were most consistently described by the negative binomial distribution, although the Poisson, Poisson binomial and logarithmic with zeros distributions were also significant for some sampling dates. Numbers of apothecia were correlated with disease incidence within areas 1.4 (r = 0.07–0.67), 36 (r = 0.11–0.72), and 108 m2 (r = 0.21–0.95). The quantitative relationships between apothecia within a field of beans and the incidence of white mold may be useful in predicting the disease.
Histology of chrysanthemum roots exposed to salinity stress and Phytophthora cryptogea
Authors: Swiecki T. J. , MacDonald J. D.
Published: September 2007

Rooted cuttings of Chrysanthemum morifolium 'Paragon' grown in nutrient solution were given a 24-h pulse exposure to salinity by amending the solution with 200 mequiv. NaCl/L. The cuttings were then returned to nonsalinized solution; one half were inoculated with motile zoospores of Phytophthora cryptogea Pethybr. & Laff, and the other half were maintained as non-inoculated controls. Nonstressed cuttings also were inoculated with P. cryptogea, and roots from all treatments were sampled at various intervals thereafter for light and electron microscopy. Penetration of nonstressed roots by P. cryptogea was frequently limited to three or four cell layers 6–12 h after inoculation. Formation of appositions adjacent to hyphae, increased wall staining density, and accumulation of osmiophilic material in cell vacuoles were associated with sites of limited penetration. In contrast, hyphae of P. cryptogea rapidly colonized salinity-stressed roots, causing extensive necrosis within 12–24 h after inoculation. The cytological responses to infection seen in nonstressed roots were rarely observed in stressed roots, indicating that salinity stress inhibits active root defense mechanisms.
The incompatibility system and relative ectomycorrhizal performance of monokaryons and reconstituted dikaryons of Laccaria bicolor
Authors: Kropp Bradley R. , Fortin J. A.
Published: September 2007

The incompatibility system of four Laccaria bicolor collections was studied and found to be bifactorial with multiallelic mating type factors. One of the collections studied was a biological species of L. bicolor that was intersterile, but morphologically identical, with the others. Seedling growth parameters and ectomycorrhiza formation were measured after inoculation with (i) four sibling mating type monokaryons of a collection from Canada and from Sweden; (ii) four dikaryons formed by crossing the two compatible mating type pairs within each of these collections; and (iii) 16 dikaryons formed by crossing each mating type monokaryon from Canada and Sweden in all possible combinations. Each seedling growth parameter showed significant differences resulting from inoculation with different cultures. Ectomycorrhizal formation was also different depending on the culture used as inoculum. Possibilities for using the differences among cultures in studies of the genetics, physiology, and morphogenesis of the ectomycorrhizal symbiosis are discussed. The possibility of creating improved strains of ectomycorrhizal fungi for use in forest management is also discussed.
Variation in Erigeron philadelphicus (Compositae)
Authors: Morton J. K.
Published: September 2007

Plants of Erigeron philadelphicus L. var. glabra Henry, E. philadelphicus forma angustatus Marie-Victorin & Rousseau, and E. provancheri Marie-Victorin & Rousseau were grown in cultivation, where all retained their characters and had a diploid chromosome number of 2n = 18. Variety glabra was found to be an ecotype of E. philadelphicus which is only known from salt marshes at Port Albemi, Vancouver Island, B.C. It is distinguished by its subglabrous stem, leaves, and involucres and its somewhat fleshy leaves. Erigeron provancheri and E. philadelphicus f. angustatus are very similar to each other in morphology. They represent different populations of a single taxon, E. philadelphicus ssp. provancheri (Marie-Victorin & Rousseau) J. K. Morton stat.nov. It is distinguished by its perennial subglabrous habit, small size, small capitula, and white or nearly white ligulate florets. Only four populations are known: a population from the tidal estuary of the St. Lawrence near Quebec City; one in a similar habitat on the Hudson River near New York; one on the Waits River in Bradford, VT; and one on dolomite rocks along the shores of Lake Huron at the tip of the Bruce Peninsula and on nearby islands.
Inflorescence and flower development in Costus scaber (Costaceae)
Authors: Kirchoff Bruce K.
Published: September 2007

The inflorescence of Costus scaber terminates an erect axis of a sympodial rhizome system. Primary bracts are borne on the inflorescence in spiral monostichous phyllotaxy. One-flowered cincinni occur in the axils of these bracts. Each cincinnus consists of an axis bearing a terminal flower and a secondary bract on the anodic side of the flower. A tertiary bud forms in the axil of this bract but does not complete development. The inflorescence terminates by cessation of growth of the apex and precocious development of the primary bracts. Floral organs are formed sequentially beginning with the calyx, and continuing with the corolla and inner androecial whorl, outer androecial whorl, and gynoecium. All flower parts, except for the calyx, originate from a ring primordium. Regions of this primordium separate to form the corolla and inner androecial members. It was not possible to determine the sequence of androecial member formation. The labellum is composed of five androecial members, three from the outer whorl and two from the inner. The third member of the inner whorl forms the stamen and its petaloid appendage. The gynoecium forms from three conduplicate primordia. The margins of two of these primordia are the product of phyietic fusion.
Laboratory comparisons of five seed-trap designs for dry, windy environments
Authors: Johnson C. K. , West N. E.
Published: September 2007

Five seed-trap designs were tested for relative seed-trapping ability in a wind tunnel. Seeds of 12 plant species were blown over random combinations of seed-trap designs with an average wind speed of 16 km∙h−1. Results showed significant effects of seed-trap design on the number of seeds collected by the traps. Seed traps simulating the ground surface (gravel, marbles, loose soil) caught significantly (P < 0.05) fewer seeds than those simulating soil depressions or holes (glued dirt, funnel). Gravel surfaces trapped significantly (P < 0.05) more seeds than the surfaces with marbles. Results of this study may be used in the selection of seed traps for use in the field where sticky surfaces are unsuitable because of drying and dust.
A new species of Beauveria isolated from Scottish moorland soil
Authors: Bissett John , Widden Paul
Published: September 2007

Beauveria caledonica sp.nov. is described from moorland soil in Scotland. The species is characterized by short-cylindrical conidia borne in acropetal sequence from conidiogenous ceils that elongate sympodially to form a long denticulate rachis. Occurrence of the species was negatively correlated with cellulolytic activity in the soils studied.
Estimating above- and below-ground macrophyte production in Scirpus tidal marshes
Authors: Giroux Jean-François , Bédard Jean
Published: September 2007

Different methods to estimate primary production of Scirpus marshes of the St. Lawrence estuary were compared. Quadrats 25 × 25 cm and cores 10 cm in diameter were found to be the optimal size to sample above- and below-ground standing crops, respectively. Ash content for different plant parts of various species was measured to obtain more accurate estimates of organic matter. A series of allometric equations relating stem height and mass were developed to estimate aerial standing crop from permanent nondestructively sampled plots. This method, however, overestimated standing crop compared with the destructive (harvest) method. The relationship between the above- and below-ground standing crop was also determined for the dominant species and used to predict belowground biomass without destructive sampling. Finally, the Smalley method provided the best estimates of net annual above- and below-ground production when losses attributed to decomposition were not considered. For less intensive studies, however, the methods based on peak standing crop and on the difference between maximum and minimum biomass would yield good approximations of above- and below-ground production.
Seed germination In Acacia auriculiformis: developmental aspects
Authors: Pukittayacamee P. , Hellum A. K.
Published: September 2007

Germination of Acacia auriculiformis A. Cunn. ex Benth. seeds was related to seed development. Full physiological development of seeds, indicated by maximum seed dry weight, was reached 82 days after anthesis; however, maximum percent germination was not reached before day 89. Later, germination declined gradually as dormancy and mortality increased. Most seeds were capable of germination without pretreatment at the time of collection, indicating that seed coats were not impermeable to water. Germination of seeds with moisture content from 14 to 29% can be achieved. Anatomical studies revealed that seeds reached maturity after compressing the parenchyma cells against the inside of the seed coat. The physical properties of the seed coat, therefore, did not control its permeability to water. After the developmental period, seed dormancy increased by further drying of seeds during storage.
The gelatinous fibres of Caesalpiniaceae
Authors: Ranjani K. , Krishnamurthy K. V.
Published: September 2007

Twenty-seven species of Caesalpiniaceae were studied to compare the gelatinous fibres of root and stem wood. Species that possessed gelatinous fibres in root wood also possessed them in stem wood, but only two taxa showed the reverse condition. Gelatinous fibres did not exhibit an organ-dependent specificity in their transectional distribution. In roots, the gelatinous fibres generally differentiated immediately after initiation of secondary growth, whereas in most stems they differentiated considerably after the onset of secondary growth. The positive correlation detected previously between the distribution pattern, as well as the number of gelatinous fibres, and the eccentricity of the stem or root could not be verified. Even perfectly noneccentric roots and stems showed variations in the distribution pattern and number of gelatinous fibres. In roots, generally, all fibres were gelatinous, whereas in stems both gelatinous and normal fibres were present and showed different distributional patterns. All three types of gelatinous fibres (convolute, thick, and intermediate) recognised by earlier workers and based on the gelatinous layer were observed in this family. Gelatinous fibres of this family formed lignified, partially lignified, and nonlignified gelatinous layers. Differences were also noticed in the relative thickness of the gelatinous layer.
Détermination de l'identité isotopique de l'azote fixé par le Frankia associé au genre Alnus
Authors: Domenach A. M. , Kurdali F. , Danière C. , Bardin R.
Published: September 2007

To use the 15N natural abundance method to evaluate the symbiotic nitrogen fixation by actinorhizal trees, it is necessary to determine the isotopic identity of assimilated nitrogen from two sources: the soil and the air. This study reports an isotopic value of fixed nitrogen by two alder species (Alnus incana (L.) Moench and Alnus glutinosa (L.) Gaertn. growing on nitrogen-free medium in greenhouse experiments. The δ15N value of the aerial parts was −2. This value was stable with time and did not depend on the Frankia strains used. This value could be used to estimate the nitrogen fixation in the natural ecosystem. Other parameters such as the mobilization of nitrogen reserves and the choice of the reference plant must be investigated to apply this method. The nodules of these two alder species were enriched in 15N relative to the rest of the plant but there was no relationship between symbiotic effectiveness of Frankia strains and 15N enrichment of nodules. On the other hand, for naturally growing trees, an enrichment in 15N was found primarily in the vesicles of nodules that are the sites of nitrogen fixation.
Distribution of carbofuran and dimethoate in flowers and their secretion in nectar as related to nectary vascular supply
Authors: Davis A. R. , Shuel R. W. , Peterson R. L.
Published: September 2007

The distribution of two systemic insecticides (carbofuran, dimethoate) in floral parts and nectar of Ajuga reptans L. (Lamiaceae), Brassica napus L. (Brassicaceae), and Vicia faba L. (Leguminosae), which differ in their types of nectary vascular supply, was determined. Radioactivity was detected in all floral organs when excised flowering plant tops were cultured in sucrose solution containing a combination of 14C-labelled and formulated (unlabelled) insecticide. In A. reptans and B. napus, combined nectary tissue and nectar contained the most radioactivity on a fresh weight basis. Radioactivity was detected in floral nectar of all species, and in extrafloral nectar of V. faba. Estimated concentrations of insecticide were much higher in extrafloral than in floral nectar of V. faba; the presence of xylem in the nectary vasculature to the former may be responsible. However, the presence of xylem is not necessary for the secretion of systemic insecticides by nectaries.
Studies of the lichen genus Ochrolechia. 1. A new classification for Pertusaria subplicans and P. rhodoleuca
Authors: Brodo Irwin M.
Published: September 2007

A reexamination of the ascus structure, spore type, and chemistry of the saxicolous lichens Pertusaria subplicans Nyl. and P. rhodoleuca Th. Fr. has revealed them to be better classified within the genus Ochrolechia. The following new combinations have therefore been introduced: Ochrolechia subplicans (Nyl.) comb.nov. and O. rhodoleuca (Th. Fr.) comb.nov. Ochrolechia rhodoleuca is apparently restricted to northern Europe, leaving O. subplicans as the name of the American material. It is possible to discern two ecologically defined subspecies within O. subplicans, each with slight chemical and morphological distinctions: subsp. subplicans and subsp. hultenii (Erichs.) Brodo comb.nov. A method is described for determining the precise location of gyrophoric, alectoronic, and variolaric acids within an ascoma by using a combination of conventional ultraviolet and spot-test techniques.
Symmetry in plants: phyllode and stipule development in Acacia longipedunculata
Authors: Sattler Rolf , Luckert Doris , Rutishauser Rolf
Published: September 2007

Both phyllodes and so-called stipules develop on a whorl platform that surrounds the shoot apex. Phyllodes usually are initiated as radial primordia. During their development, although they become acrovergent and show a slight differentiation gradient from the abaxial towards the adaxial side, they retain a circular outline in transection until maturity. Longitudinally they differentiate into a basal pulvinus, a photosynthetic zone, and a terminal mucro. While only one concentric vascular bundle is formed in the pulvinus region, a cylindrical vascular network differentiates in the photosynthetic zone and only one collateral bundle surrounded by sclerenchyma develops in the mucro. In terms of both external symmetry and internal organization, phyllodes show a striking resemblance to stems, whereas so-called stipules appear more leaf-like because of their dorsiventral symmetry. After a detailed discussion of the role symmetry plays in various complementary interpretations of phyllodes and so-called stipules, symmetry transformations in angiosperms in general are illustrated. It is concluded that symmetry, growth pattern, and position do not constitute criteria that allow us to assign all known developmental pathways to mutually exclusive categories such as caulome or phyllome. Transformational analysis is suggested as a more adequate and dynamic tool for understanding the diversity of plant form.
Apical control of band elongation in Antithamnion defectum (Ceramiaceae, Rhodophyta)
Authors: Garbary David , Belliveau Daniel , Irwin Robert
Published: September 2007

Cell elongation in the Ceramiaceae typically occurs by means of one or two bands located apically and (or) basally in each cell. In axial cells of Antithamnion defectum two bands are present; however, most cell elongation occurs as a result of new wall deposition in bands at the base of each axial cell. In cells of determinate branches, only the basal band is present. In experimental conditions in which apical cells of indeterminate branches are differentially excised, location of the primary elongation band can be reestablished in relation to remaining indeterminate axes. Thus, the primary elongation band in axial cells is always basal with respect to indeterminate apical cells. When all indeterminate apices are removed, band growth becomes highly disrupted, and diffuse, irregularly located bands are formed. These results suggest that regulation of band position and elongation is through apical control.
The conidia of Typhula incarnata. 1. The ultrastructure of conidiogenesis
Authors: Metzler B.
Published: September 2007

Monokaryotic strains of Typhula incarnata Lasch ex Fr. are able to produce small, unicellular, hyaline blastoconidia in basipetal sequence. The conidia are encapsulated by sticky mucilage and are derived from conidiogenous projections, each at the distal end of a conidiogenous cell. These structures elongate with formation of each new conidium. Tiny wall scars, visible in the transmission electron microscope, indicate an annellidic mode of conidiogenesis. However, the proliferation shows a weak sympodial tendency, owing to the partial plasticisation and integration of the preceding ring scars. This pattern was hitherto unknown for Basidiomycetes.
The conidia of Typhula incarnata. 2. Their function as spermatia
Authors: Metzler B.
Published: September 2007

The conidia of monokaryotic strains of Typhula incarnata Lasch ex Fr. failed to germinate. However, homing reactions in compatible mycelia were induced. The homing branches of hyphae often fused with conidia. As a result of dikaryon formation the production of clamp connections took place. These characteristics, their “wet” surface, and their minute size permit us to term the conidia of T. incarnata "spermatia."
A comparative study of cultural and electrophoretic characteristics of the Eurasian and North American races of Ophiostoma ulmi
Authors: Jeng R. S. , Bernier L. , Brasier C. M.
Published: September 2007

Cultural characteristics and isoenzyme and soluble protein patterns on polyacrylamide gradient gels were compared in field isolates of the aggressive subgroup of Ophiostoma ulmi. Fourteen isolates were tested, 7 of the Eurasian race and 7 of the North American race. Values of fresh weight, dry weight, acetone powder weight, and water content of the flask-grown mycelia of Eurasian isolates were significantly higher than corresponding values measured in the North American isolates. The intramycelial protein content was the same for both races. Toxin (cerato-ulmin) production in the culture filtrates, expressed on the basis of dry mycelial weight, was greater in the North American isolates. Isoenzymes of peroxidase, tetrazolium oxidase, and certain protein bands can be used as biochemical markers to distinguish the two races. Results strongly suggest that isolate 83 is a hybrid between the Eurasian and North American races.
Chloroplast genomic variation and phylogeny in Medicago section Intertextae
Authors: Rose R. J. , Schlarbaum S. E. , Small E. , Johnson L. B.
Published: September 2007

Restriction endonuclease analysis of chloroplast DNA (cpDNA) was conducted on Medicago ciliaris, Medicago intertexta, Medicago muricoleptis, and Medicago granadensis, which comprise section Intertextae of the genus Medicago. Numerical taxonomic analyses of cpDNA data by a variety of techniques indicated the same species relationships found in a previous study when these numerical analyses were applied to phenotypic and karyotypic characters. The correspondence between cpDNA, general morphology, and karyotypic data suggests that all data mirror general evolution. Data from this study support earlier proposals of a close relationship between Medicago ciliaris and Medicago intertexta, with these species evolving from a common lineage and a later, independent evolution of Medicago muricoleptis and Medicago granadensis from Medicago intertexta.
Leaf conductance of four species growing in a subarctic marsh
Authors: Lafleur Peter
Published: September 2007

This paper describes measurements of leaf conductance made with a diffusion porometer on four wetland species growing in a coastal marsh on James Bay. The measurement period covered most of the growing season. In general, leaf conductance for the sedge, Carex paleacea, was larger than for three woody species, Alnus rugosa, Salix bebbianna, and Salix discolor. No distinct pattern was observed in maximum conductance throughout the growing season; however, leaf conductance demonstrated distinct diurnal trends for all species. The response of leaf conductance to various environmental variables was examined and it was found that conductance of all species was most strongly related to the atmospheric vapour pressure deficit. Two models for predicting leaf conductance from environmental variables showed moderate success.
Mycorrhizal dependence and growth habit of warm-season and cool-season tallgrass prairie plants
Authors: Hetrick B. A. Daniels , Kitt D. Gerschefske , Wilson G. Thompson
Published: September 2007

Warm-season (C4) and cool-season (C3) mycorrhizal grasses were 63–215 and 0.12–4.1 times larger in dry weight than non-inoculated controls, respectively. Nonmycorrhizal warm-season plants did not grow and frequently died, while cool-season plants grew moderately well in the absence of mycorrhizal symbiosis. Like warm-season grasses, tallgrass prairie forbs were highly dependent on mycorrhizal symbiosis, even though they are not known to employ the C4 photosynthetic pathway. Thus, phenology may be more critical than photosynthetic pathway in determining mycorrhizal dependence. Warm-season grasses and forbs had coarser, less frequently branched root systems than cool-season grasses, supporting the hypothesis that mycorrhizal dependence is related to root morphology. Cool-season grasses may have developed more fibrous root systems because mycorrhizal nutrient uptake was not effective in the colder temperate environment in which they evolved. In contrast, warm-season plants and dependence on mycorrhizal fungi may have coevolved, because both symbionts are of tropical origin.
Aptitudes germinatives comparées de graines de Rumex acetosella issues de populations correspondant à des stades distincts d'une succession postculturale
Authors: Escarré J. , Houssard C.
Published: September 2007

Germination of Rumex acetosella L. was studied under a variety of experimental conditions to determine whether populations from old fields of different ages (fallow for 6 months to 15 years) differed in seed weight and germination rate and in plant biomass and flowering rate of the resulting plants. Fresh seeds collected from these natural populations showed differences in germination that varied with the date of harvest and the number of years since the field was last cultivated: seeds of the youngest population harvested in July germinated the best and were lighter than those of the other populations. Different fertilizer levels applied during the growth of the mother plants from seeds collected in the original old fields affected the mean weight and the germination rate of the resulting seeds, regardless of the density of cultivation of the mother plant. However, the effect of different fertilizer levels on mean seed weight varied with the origin of each population. Heavy seeds (mean weight > 0.6 mg) of mother plants from the populations of fields abandoned over 2 years ago germinated better than light seeds (mean weight < 0.6 mg). There was no significant difference between heavy and light seeds in terms of percent germination for seeds from mother plants that came from the "youngest" field. These differences in germination rate observed in field-collected seeds were also found in light seeds of the offspring generation: light seeds of the mother plant from the population belonging to the more recently abandoned old field germinated the best. Plants grown from heavy seeds that came from the other populations of older fields had more biomass than those resulting from light seeds. This difference has not been observed between individuals resulting from light and heavy seeds of the youngest population. On the other hand, these individuals had a higher flowering rate than those resulting from the older populations. These results are interpreted in relation to the successional status of the populations: high flowering and early germination rates are suitable characteristics for establishment of plants on bare ground or after a disturbance, whereas heavy seeds with more reserves ensure germination and enough biomass of the resulting plants in density-dependent conditions.
Distribution of scaled chrysophytes in 17 Adirondack (New York) lakes with special reference to pH
Authors: Siver Peter A.
Published: September 2007

Thirty-four scaled chrysophyte taxa are described from 17 Adirondack lakes located in either Hamilton or Franklin counties. Ten taxa, Synura sphagnicola, Syn. echinulata, Syn. petersenii, Mallomonas acaroides var. muskokana, M. hamata, M. caudata, M. crassisquama, M. galeiformis, Spiniferomonas trioralis, and Chrysosphaerella longispina, were found in more than 40% of the study lakes. Mallomonas acaroides var. muskokana, M. hamata, Syn. sphagnicola, Syn. echinulata, and Spiniferomonas coronacircumspina were common and important components of the phytoplankton floras in lakes with a pH < 5.4; however, M. hamata and Sp. coronacircumspina were noticeably absent from bog lakes. Synura sphagnicola and Syn. echinulata were as common in samples with a pH between 5.4 and 7 as they were below pH 5.4. Mallomonas crassisquama, M. caudata, M. pseudocoronata, and Synura spinosa were found in a significantly greater percentage of samples from circumneutral lakes and were lacking from waters with a pH < 5.4. Differences in species distributions between Hamilton County (higher mean pH) and Franklin County lakes further supported the observed pH ranges of the common taxa. Similarities and differences are made with a study of Smol et al. (Can. J. Bot. 62: 911–923), who described the distribution of scaled chrysophytes from the surface sediments of Adirondack lakes.
Stomatal conductance and stomatal behavior in Populus clones and hybrids
Authors: Ceulemans R. , Impens I. , Imler R.
Published: September 2007

Responses of abaxial, adaxial, and total leaf conductance to incident photosynthetic photon flux density, solar irradiance, and changing leaf water potential, as well as diurnal and seasonal patterns of stomatal conductances, were examined under field conditions for six Populus clones. Clones belonged to the species P. trichocarpa and to different interspecific crossings including P. deltoides, P. nigra, and P. maximowiczii. Black Cottonwood clone Columbia River showed stomatal behavior different from other clones in many aspects: (i) it was the only clone with hypostomatous leaves; (ii) its stomata remained open for a longer period of time, both diurnally and seasonally; (iii) the hysteresis effect in stomatal response to solar irradiance during the day was less pronounced; and (iv) its stomata showed hardly any response to declining leaf water potential. Leaf area duration and seasonal stomatal activity showed considerable clonal differences, which are in agreement with girth growth increment patterns. Clone Columbia River showed a much longer leaf life-span with considerable stomatal activity near late autumn, which might explain the substantial late-autumn girth growth increment of this clone.
Vasculature and ultrastructure of the floral and stipular nectaries of Vicia faba (Leguminosae)
Authors: Davis A. R. , Peterson R. L. , Shuel R. W.
Published: September 2007

The floral nectary of Vicia faba L. (faba bean, broad bean, or field bean) consists of a disk which bears a long, basal, tapered projection. Large, open stomata, located at the tip of the projection, probably serve as exits for nectar. Phloem is present in the floral nectary. The extrafloral nectary consists of numerous secretory and nonsecretory trichomes aggregated on the abaxial surface of each stipule. Both xylem and phloem are present in the stipule beneath the extrafloral nectary. In both nectary types, large companion cells accompany the phloem. Epidermal and parenchyma cells of the floral gland, as well as the companion cells, develop wall ingrowths and are therefore transfer cells. Ultrastructural evidence suggests a granulocrine mechanism of nectar secretion in the floral nectary, wherein both apoplastic and symplastic routes for prenectar movement and escape appear feasible. Floral and extrafloral nectar differ in sugar concentration and in the predominance of sucrose, both of which are higher in exudate from floral nectaries.
Aquatic macrophytes in Adirondack (New York) lakes: patterns of species composition in relation to environment
Authors: Jackson Stephen T. , Charles Donald F.
Published: September 2007

A study of aquatic vegetation of 31 small, dilute, and unproductive lakes in the Adirondack Mountains of New York shows that macrophyte species composition is primarily related to variation in pH and associated factors. Among the lakes, surface water pH ranged from 4.5 to 7.8; conductivity ranged from 11.9 to 58.7 μS/cm. Relationships between aquatic vegetation and environmental factors were studied using detrended correspondence analysis (DCA). Submersed and floating-leaved taxa were analyzed separately from emergent taxa. Correlations between DCA axis 1 and pH-related factors (pH, alkalinity, Ca, Mg, Na, Al, conductivity, elevation) were strong for both submersed plus floating-leaved and emergent taxa. No significant correlations were found with water color, transparency, or trophic status indicators (total P and chlorophyll a). Between-lake variation in composition of aquatic vegetation in Adirondack lakes follows a pH "complex-gradient." Influences of elevation, morphometry, and substrate are secondary. Our results indicate that acidification of softwater lakes could be accompanied by significant changes in aquatic macrophyte assemblages.
Alpha-amylase in seed hulls of developing Brassica campestris
Authors: Caeseele L. Van , MacGregor A. W.
Published: September 2007

Extracts of hulls from developing Brassica campestris and Brassica napus seeds were examined for α-amylase activity. The enzyme was compared with α-amylase from barley pericarp and germinated barley seeds, using isoelectric focusing. Enzymes of similar isoelectric point (pI) were present in B. campestris, B. napus, and barley pericarp. Additional bands of activity were present in B. napus. The major α-amylase component of germinated barley has a high pI, but no corresponding isozyme was detected in the other three samples. The increase in total activity of α-amylase in Brassica seed hulls coincided with the increase in starch granule size in the epidermal cell layer, with maximum activity approximately 16 days after pollination.
Scierification of juice sacs in pummelo (Citrus grandis) fruit
Authors: Shomer Ilan , Chalutz Edo , Vasiliver Rosa , Lomaniec Ella , Berman Monica
Published: September 2007

Granulation of juice sacs in pummelo (Citrus grandis L.) fruit was found to occur upon ripening. The juice sac tissue consisted of epidermal and subepidermal cell layers, an elongated cell layer, and juice cells. The granulation was accompanied by the appearance of opaque white regions inside transparent tissue. The subepidermal cells of the granulated tissue were disordered and the cell walls of the elongated and the juice cells were distinctly thickened. An ultrastructural study has shown that the subepidermal cell walls of granulated juice sacs were distorted and had swollen regions. The cell walls of both the elongated and the juice cells had secondary thickening with pits. The total dry weight, cellulose (as glucose), lignin, and hemicellulose (as xylose) were significantly higher and insoluble proteins were lower in granulated juice sacs than in non-granulated ones. The content of insoluble neutral sugars such as rhamnose, arabinose, mannose, and galactose decreased as a result of granulation, as did that of soluble sugars glucose, fructose, sucrose, and organic acids. Thus, it seems that granulation of pummelo fruit juice sacs is a result of lignification of the juice cells, which leads to the formation of sclerenchyma.