bluuebunny/crossref_metadata_2025 huggingface dataset:
Plagiotropic architectural development of four tree species of the temperate forest
Authors: Millet Jeanne , Bouchard André , Édelin Claude
Published: April 2011

Four tree species of the temperate deciduous forests of south-western Québec have an architectural development that corresponds to Troll's model. Two of these species, American elm (Ulmus americana L.) and American basswood (Tilia americana L.), are mid-successional and the two others, American beech (Fagus grandifolia Ehrh.) and Eastern hemlock (Tsuga canadensis (L.) Carr.), are late successional. In the four species, the main stem is the result of the stacking of modules with plagiotropic development and secondary straightening. Nevertheless, the architectural analysis of these four species reveals that two growth patterns are present. In elm and basswood, the modules are differentiated from one another and are integrated into the hierarchical structure of the tree. In beech and hemlock, the modules are mixed and their apical meristems possess an autodifferentiation potential, which provides for a greater individuality within the tree structure. In spite of belonging to the same architectural model, differences in the development pattern favour a greater efficiency in stem growth for elm and basswood versus a greater shape plasticity, including a greater lateral branch development if required, in beech and hemlock.Key words: tree architecture, organization plan, Troll's model, plagiotropy, morphological differentiation of axes.
Yinmingella mitriformis gen. et sp.nov., a new sporodochial hyphomycete from submerged wood in Hong Kong
Authors: Goh T K , Tsui K M , Hyde K D
Published: April 2011

Yinmingella mitriformis gen. et sp.nov. (Hyphomycetes), occurring on wood submerged in Tung Chung River on Lantau Island, Hong Kong, is described and illustrated. It is unique in producing short, true chains of holoblastic, aseptate, smooth, black, mitriform conidia from dark brown, flask-shaped conidiogenous cells on hemispherical, black stromata. Yinmingella is compared with Hemibeltrania, Hemicorynespora, Mammaria, Janetia, Sporidesmium, and Stanjehughesia.Key words: cryo-SEM, dematiaceous Hyphomycetes, freshwater fungi, mitosporic fungi, systematics.
Ultrastructure of tracheid cell walls in radiata pine (Pinus radiata) mild compression wood
Authors: Singh Adya P , Donaldson Lloyd A
Published: April 2011

The structure of tracheid cell walls in mild compression wood of Pinus radiata D. Don was examined by confocal laser scanning fluorescence microscopy (CLSM) and transmission electron microscopy (TEM). Fluorescence microscopy using lignin autofluorescence revealed cell to cell variations in lignification of the cell corner middle lamella (CCML) and outer S2 (S2L) regions supporting observations made at higher resolution with TEM. The mild compression wood sample examined lacked the characteristic intercellular spaces of most grades of compression wood and thus represents the least severe grade of compression wood. TEM observations revealed evidence for radial striations in the S2 region probably representing regions of alternating high and low lignin concentration, which may be the precursor to the helical cavities found in severe compression wood. These radial striations typically showed a sinuous and branched structure, extending partly into the S2L region, where the orientation of lignin lamellae was predominantly tangential following the arrangement of the cellulose microfibrils. At high magnification lignin occurred in a patchy distribution overlaying the typical lamellate arrangement associated with normal wood. Significant variability in the lignification of the CCML region was also observed sometimes giving a patchy or granular appearance. The lignification of the CCML and the S2L regions was generally comparable, while S1 and S2 layers were less lignified. A residual S3 layer was sometimes present in the form of a very thin layer slightly more lignified than the adjacent S2 layer.Key words: compression wood, Pinus radiata D. Don, ultrastructure, confocal laser scanning microscopy, transmission electron microscopy, lignin distribution.
Cytogenetic and isozymic characterization of the narrow endemic speciesArtemisia molinieri(Asteraceae, Anthemideae): implications for its systematics and conservation
Authors: Torrell Montserrat , Bosch Maria , Martín Joan , Vallès Joan
Published: April 2011

We carried out a cytogenetic and isozymic study of Artemisia molinieri Quézel, Barbero, & R. Loisel (Asteraceae, Anthemideae), a narrow endemic species limited to two populations in southeastern France. Fine karyotype analysis, including fluorochrome banding, enabled us to discuss the systematic affinities of this taxon, which is closely related to Artemisia abrotanum L. and Artemisia chamaemelifolia Vill. Isozyme electrophoresis showed higher genetic variability than expected for a plant with a very restricted geographic distribution. These data, along with the results of a study of pollen viability and some ecological factors, led us to propose some ideas concerning the conservation strategy for this rare plant species.Key words: Artemisia molinieri, Asteraceae, cytogenetics, isozyme variability, systematics, conservation, narrow endemic species.
The influence of UV-B radiation on the superoxide dismutase of maize, potato, sorghum, and wheat leaves
Authors: Santos Isabel , Almeida José , Salema Roberto
Published: April 2011

The influence of UV-B radiation on superoxide dismutase (SOD, EC 1.15.1.1) with reference to the activity and types of isoenzymes was studied in leaves of C3 plants (potato, Solanum tuberosum L. cv. Désirée, and wheat, Triticum aestivum L. var. Almansor) and C4 plants (maize, Zea mays L. var. LG12, and sorghum, Sorghum Pr 8515 Pioneer). Plants were grown under controlled conditions in growth chambers with and without UV-B radiation. After 10 days of irradiation it was found that UV-B affected both the total activity of SOD and the number and amount of isoforms in all plants. The total specific activity of SOD increased significantly in wheat, maize, and potato, whereas a decline was induced in sorghum. Native gels revealed that UV-B caused preferential changes of the SOD isoforms in all plants used. Inhibition studies with cyanide and hydrogen peroxide showed that, in maize, UV-B radiation caused a large accumulation of one Mn-SOD and in contrast the level of the Cu,Zn-SOD isoforms decreased. In potato leaves, UV-B changed the pattern of SOD isoenzymes causing the appearance of one isoform and the disappearance of another. In wheat and sorghum the pattern of the isoenzymes was not altered, only their relative amounts. The rise in SOD activity in maize, potato, and wheat is possibly correlated with the tolerance of UV-B ascribed to these crops by different researchers and the sensitivity of sorghum to UV-B is possibly associated with the decrease in SOD activity.Key words: superoxide dismutase, UV-B, maize, potato, sorghum, wheat.
Variabilité génotypique de l'aptitude à la fixation symbiotique de l'azote chezAcacia cyanophyllaLindl.
Authors: Nasr Hafedh , Sghaier Tahar , Ghorbal Mohamed Habib , Dommergues Yvon René
Published: April 2011

Genotypic variability of the symbiotic nitrogen fixation ability on Acacia cyanophylla Lindl. The phenotypic and functional characteristics of four rhizobium strains isolated from nodules of Acacia cyanophylla Lindl., syn. Acacia saligna (Labill.) H. Wendl., and the inoculated host-plant genetic variability were evaluated. The evaluation used permitted the ranking of the tested rhizobium strains and seedlots according to their performance. The growth pattern of these strains indicated that A. cyanophylla was able to nodulate and fix N2with slow- and fast-growing rhizobium strains. The acetylene reduction activity test reflected a variable effectiveness of the strains depending on their site of isolation. Strains RFH383 and RFH483 were more effective than RFH183 and RFH283. The high antibiotic resistance acquisition by RFH183 and RFH283 strains seemed to be inversely related to their effectiveness. Acacia cyanophylla seedlings from five seedlots displayed a high variability regarding their growth, nodulation, and ability to fix nitrogen. The ability to fix nitrogen was greater in the seedlings from KL seedlot than those from EN, KR, and TZ seedlots. The qualitative assessment of the seedlots using correspondence factorial analysis showed that the seedlings from KL seedlot preformed better than those from KR and TZ. The seedlings from TN and EN seedlots displayed an intermediate behaviour pattern. Seed origin seemed to affect the growth, nodulation, and nitrogen fixation of inoculated A. cyanophylla. The behaviour of this species and that of its associated rhizobium strains appeared to be very sensitive to variations in site characteristics. Results suggested that the association between plants derived from KL seedlot and RFH383 strain may represent the best partnership allowing the improvement of symbiotic nitrogen fixation.Key words: Acacia cyanophylla, rhizobium, nodulation, N2fixation, genotypic variability, correspondence factorial analysis.
Using Lindenmayer systems to model morphogenesis in a tropical pasture legume Stylosanthes scabra
Authors: Wilson Peter A , Hanan James S , Room Peter M , Chakraborty Sukumar , Doley David
Published: April 2011

This paper summarizes the processes involved in designing a mathematical model of a growing pasture plant, Stylosanthes scabra Vog. cv. Fitzroy. The model is based on the mathematical formalism of Lindenmayer systems and yields realistic computer-generated images of progressive plant geometry through time. The processes involved in attaining growth data, retrieving useful growth rules, and constructing a "virtual plant" model are outlined. Progressive output morphological data proved useful for predicting total leaf area and allowed for easier quantification of plant canopy size in terms of biomass and total leaf area.Key words: Lindenmayer systems, modelling, Stylosanthes, morphogenesis, plant form.
Vascular stem resistance to black rot in Brassica oleracea
Authors: Ignatov A , Kuginuki Y , Hida K
Published: April 2011

The stem vascular system of several accessions of cultivated Brassica oleracea L. showed resistance to black rot caused by Xanthomonas campestris pv. campestris (Pammel) Dowson. Resistance prevented systemic spread of the pathogen in the vascular system of stem. It was race nonspecific and effective at the early stage of seedling growth. A major dominant gene (Rs; resistant in stem), responsible for expression of compete stem resistance in adult plants (more than six true leaves), was found in a Chinese kale line SR1. At least one more dominant gene with additive interaction was necessary to provide complete resistance in seedlings. In progeny of a cross with a cabbage line PI436606, kale SR1 stem resistance segregated independently of race-specific resistance from a PI436606. It can be considered as an alternative mechanism of plant defense, and a highly valuable feature for crops systemically infected by black rot during propagation in commercial nurseries.Key words: black rot, Xanthomonas campestris pv. campestris, Brassica oleracea, disease resistance, cabbage, kale, broccoli.
Ultrastructure, chemical composition, and recrystallization of epicuticular waxes: transversely ridged rodlets
Authors: Meusel Iris , Neinhuis Christoph , Markstädter Claus , Barthlott Wilhelm
Published: April 2011

Transversely ridged rodlets (Aristolochia-type) are of high systematic significance characterizing the ancestral Aristolochiales, Magnoliales, and Laurales. Sporadically, they also occur in various unrelated derived taxa. The ultrastructure, chemistry, and recrystallization of epicuticular waxes of nine species were investigated by high resolution scanning electron microscopy, gas chromatography, and mass spectrometry. Chemical analyses show that transversely ridged rodlets clearly differ in their composition. Waxes of one group are characterized by ketones, whereas a second group completely lacks ketones and is dominated by alkanes. Hentriacontan-16-one (palmitone) was found to be characteristic for transversely ridged rodlets of Aristolochia, Laurus, and Paeonia. Standard solutions were taken for recrystallization experiments under different conditions of solvent, crystallization velocity, and temperature. It was shown that transversely ridged rodlets or related crystals grow from total waxes of all species but never crystallize from individual compounds such as alkanes or palmitone. We concluded that transversely ridged crystals are formed by self-assembly based on a slow crystallization process and the presence of additives. This paper shows that transversely ridged rodlets occur convergently within angiosperms based on a similar mode of crystallization but a different chemical composition. The role of palmitone as a chemotaxonomic character of ancestral angiosperms is discussed.Key words: plant cuticle, epicuticular waxes, chemistry, ultrastructure, recrystallization, systematics.
Consequences of achene biomass, within-achene allocation patterns, and pappus on germination in ray and disc achenes of Aster umbellatus var. umbellatus (Asteraceae)
Authors: Chmielewski Jerry G
Published: April 2011

A familiar floral dimorphism that may have an associated seed heteromorphism, that is, the production of seeds with variable morphologies and ecological strategies, is the presence of both ray and disc florets in the capitula of most Asteraceae. Achenes of Aster umbellatus var. umbellatus Mill. were separated into the ray or disc type with either the pappus remaining attached and intact, or removed. Differential allocation of biomass between ray and disc achenes or heavy and light achenes was not observed. Germination was relatively low (disc achenes with pappus removed, 16.7%; ray achenes with pappus removed, 22.9%; disc achenes with pappus intact, 7.3%; and ray achenes with pappus intact, 7.2%) for each. Although achene weight did not affect the likelihood of germination, germination was 2.5-3 times greater among disc and ray achenes, respectively, for which the pappus was removed as opposed to intact. These results do not conform with previous thoughts relative to the advantageous role of the pappus in germination. As such, I suggest that in this species of Aster the key role of the pappus is to facilitate dispersal as opposed to encourage germination. Furthermore, the production of morphologically and ecologically indistinguishable ray and disc achenes by A. umbellatus var. umbellatus would suggest that the significance of heterogamous capitula, specifically the production of ray florets, rests in their attractiveness of pollinators.Key words: within-achene allocation patterns, germination, Aster.
Influence de perturbations anthropiques sur la composition et la diversité botanique des pelouses calcicoles de la vallée de la Seine en Haute-Normandie (France)
Authors: Dutoit T , Roche P , Alard D
Published: April 2011

The effects of two types of anthropic disturbances (reaping and plowing) were followed over 3 years, on four calcicolous meadows of the Seine valley (Haute-Normandie) in France, using the quadrat points method. Multivariate analysis performed on the overall data show that compositions and structures of the different plant communities are mainly influenced by the site geographic position along an ecological gradient developing from the Seine river estuary toward the uppper stream of the river. Over the 3 years of observation, a significant increase of the species diversity (Shannon's index) and richness was observed in the reaped plots compared with the plots that were abandoned after disturbances. However, there was no significant difference between the two treatments in the species diversity as well as richness. Results are discussed in view of conservative management of calcicolous meadows, since these seminatural ecosystems are especially threatened in Western Europe.Key words: calcicolous meadows, disturbances, species diversity and richness, conservation, Haute-Normandie, France.[Journal translation]
Carbon flux in a subalpine spruce-fir forest: pulse release from Hylocomium splendens feather-moss mats
Authors: Wilson Jennifer A , Coxson Darwyn S
Published: April 2011

Mature subalpine spruce-fir forests in western Alberta are often characterized by extensive feather-moss mat coverage of the forest floor surface. The ecosystem role of these mats has been described as one of a nutrient sink because of their ability to assimilate solutes from throughflow solutions and their role as a catchment area for litterfall and detritus. These bryophyte mats are subject to recurring episodes of wetting and drying during the summer months. We examined the potential for pulse release to throughflow solution of previously sequestered carbon held by Hylocomium splendens (Hedw.) B.S.G. During rehydration, pulse release, measured as total organic carbon (TOC), reached 1544 mg·m-2. At a stand level basis this represents up to 15 kg·ha-1 pulse release of readily soluble carbon from the live green layer of H. splendens moss mats during each rewetting event. Control throughflow collectors, where moss mats were replaced by an inert mulch layer, indicated that from 23 to 75% of this pulse release originated in the moss mats. High intensity rain events resulted in larger net TOC and K release, as did a pretreatment history of rapid drying of H. splendens fronds. These findings suggest that feather-moss mats may function, in part, as ecosystem capacitors, sequestering nutrients and carbon at low concentrations from atmospheric sources, which are later released at higher concentrations during rewetting events.Key words: bryophyte, pulse release, carbon cycling, moss, nutrient cycling, montane forest.
The effect of host defoliation on hemiparasitic-host interactions between Rhinanthus serotinus and two Poa species
Authors: Puustinen Susanna , Salonen Veikko
Published: April 2011

We determined in a greenhouse experiment whether experimental defoliation of the host affects the performance of the parasitic plant and whether the effects on the success of the parasite depend on the host species. We also asked whether two species of grass hosts differ in response to simultaneous defoliation and hemiparasitic infection. The experiment had a complete 2 × 3 × 2 factorial design, with host species (Poa annua L. or Poa pratensis L.) combined with defoliation (undefoliated, 50% defoliated, or 100% defoliated) and hemiparasitic infection (parasitized or unparasitized). Defoliation reduced the final biomass of both host species. However, total biomass and the number of flowers produced by the hemiparasitic Rhinanthus serotinus (Schönh.) Oborny was reduced only when the host was P. annua and when the host was completely defoliated. Rhinanthus infection significantly decreased the final biomass of both host species. However, the two hosts differed in their responses: the biomass of undefoliated P. annua plants was reduced four times more than that of undefoliated P. pratensis plants. The results indicate that the relative value of different host species depends on the intensity of defoliation.Key words: root hemiparasite, host defoliation, host-parasite interaction, Poa annua, Poa pratensis, Rhinanthus serotinus.
Ectomycorrhizal diversity and community structure in oak forest stands exposed to contrasting anthropogenic impacts
Authors: Baxter James W , Pickett Stewart TA , Carreiro Margaret M , Dighton John
Published: April 2011

We compared the ectomycorrhizal community structure of oak forest stands located in either an urban or a rural area. Urban stands had higher N deposition rates, soil heavy metal levels, and earthworm counts than rural stands. Ectomycorrhizal types were quantified on roots of mature oak (Quercus) in soil cores and on Quercus rubra L. seedlings grown in soil cores in the glasshouse. Twenty-six ectomycorrhizal types were distinguished on mature oak in rural soils versus 16 in urban soils. Nine ectomycorrhizal types were distinguished on Q. rubra seedlings grown in rural soils versus seven in urban soils. Despite fewer ectomycorrhizal types in urban soils, richness of ectomycorrhizal types per centimetre fine root of mature oak or Q. rubra seedlings did not differ between urban and rural soils. Ectomycorrhizal colonization (ectomycorrhizal tips/m fine root) was lower in urban than rural soil cores but higher on Q. rubra seedlings grown in urban versus rural soils. Fine root length per unit soil volume was higher in urban than rural stands. No difference in fine root length was observed between Q. rubra seedlings grown in urban and rural soils. These differences in ectomycorrhizal community structure between the urban and rural stands are likely due to anthropogenic impacts.Key words: air pollution, anthropogenic impacts, community structure, diversity, ectomycorrhiza, Quercus rubra.
Endodermal silicification in developing seminal roots of lowland and upland cultivars of rice (Oryza sativaL.)
Authors: Lux Alexander , Luxová Miroslava , Morita Shigenori , Abe Jun , Inanaga Shinobu
Published: April 2011

Silica deposition in two upland rice cultivars, IRAT 109 and Moroberekan, and one lowland rice cultivar, Koshihikari, were compared. X-ray microanalysis coupled with environmental scanning electron microscopy was used to examine fresh, unfixed, hydrated samples for analyses. The results showed silica deposition in seminal roots exclusively in endodermal cells. A clear basipetal increase in Si content was found in the endodermis of all cultivars. Comparison of silicification intensity between the three cultivars showed higher amounts of Si deposited in the endodermis of upland rice cultivars. This might be related to a higher drought resistance of these types of rice. In leaves, silica deposits were present in all epidermal cells with the highest concentration in silica cells. The amount of Si deposited in leaves was several times higher than in the root endodermis. No relationship between extent of leaf epidermal silicification was found when lowland and upland cultivars were compared.Key words: endodermis, environmental scanning electron microscope (ESEM), rice, root, silica deposits, X-ray microanalysis.
Genotypic variations among isolates ofMarasmius quercophilus, a white-rot fungus isolated from evergreen oak litter
Authors: Farnet A M , Roux M , Petit J Le
Published: April 2011

Marasmius quercophilus is a white-rot basidiomycete isolated from evergreen oak litter. This fungus plays an extensive role in litter degradation because of its cellulase, pectinase, and laccase production. Our objective was to investigate the potential genotypic polymorphism of this species using RAPD (random amplified polymorphic DNA) and the amplification and the sequencing of fragments ITS (internal transcribed spacer) from the rRNA repeat. An intraspecies polymorphism was observed for the M. quercophilus isolates studied as suggested by the tree found with RAPD data: seven subgroups were defined. The minimum similarity coefficient observed in these groups was 0.278. The sizes of fragments ITS 1 and ITS 2 were the same for each isolate (ITS 1: 320 bp and ITS 2: 450 bp), and the percentages of nucleotide variation were 1.25 and 1.11%, respectively. Few isolates from the studied population had the same RAPD pattern that would suggest a clonal development in some zones of the site of La Gardiole.Key words: Marasmius quercophilus, intraspecific variability, ITS, RAPD.
In situ analysis of introduced Frankia populations in root nodules of Alnus glutinosa grown under different water availability
Authors: Nickel Anja , Hahn Dittmar , Zepp Kornelia , Zeyer Josef
Published: April 2011

The competitive ability for nodulation of Alnus glutinosa (L.) Gaertn. plants by Frankia strains inoculated into soil with indigenous Frankia populations was studied at two matric potentials representing "dry" (-0.016 MPa) and "wet" (-0.001 MPa) conditions. In pots kept at a matric potential of -0.001 MPa, nitrate concentrations decreased within 3 weeks more than 10-fold to an average of approx. 200 µmol·(g soil dry wt.)-1. After 4 months, nitrate concentrations in these pots were 16 ± 16 and 277 ± 328 µmol·(g soil dry wt.)-1 (mean ± SD) for non-inoculated and inoculated soils, respectively. At a matric potential of -0.016 MPa, nitrate concentrations for non-inoculated and inoculated soils were 687 ± 491 and 1796 ± 1746 µmol·(g soil dry wt.)-1, respectively. Inoculated plants always grew better than their non-inoculated counterparts. The largest plants were found on inoculated soil at a matric potential of -0.001 MPa, whereas the smallest plants were found on non-inoculated soil at the same matric potential. At a matric potential of -0.016 MPa, plants grown on non-inoculated soil were not as tall as those grown on inoculated soil and were slightly chlorotic, indicating that the high level of nitrate in the soil was not providing optimal plant growth conditions. The number of nodule lobes formed on plants was not significantly different among treatments, though size and weight of lobes differed. Nodules from plants grown on inoculated soils always harbored vesicle-producing Frankia populations, while nodules from plants grown on non-inoculated soils harbored only Frankia with distorted vesicles or no Frankia at all. All strains in nodules from plants grown on non-inoculated soil were of Alnus host infection group IIIa. Nodules from plants grown on soil inoculated with strains ArI3 (group IIIa), Ag45/Mut15 (group IV), and AgB1.9 (group I) were also infected by Frankia strain Ag45/Mut15. These results indicate that by inoculation, Frankia populations could be established under conditions that did not favour vesicle formation in root nodules formed by the indigenous Frankia population. Inoculation even in soils with high nitrogen content might therefore be an appropriate strategy to enhance plant growth.Key words: competition, fluorescent oligonucleotide probes, inoculation, in situ hybridization, matric potential, nitrate, rRNA.
Development in theDatisca-Coriarianodule type
Authors: Berg R Howard , Langenstein Birgit , Silvester Warwick B
Published: April 2011

This structural study of development of infected cells in the Datisca Baill. - Coriaria Lindsay nodule type explores several unique features of their symbiosis that are similar in both species of plants, providing the following interpretations of infected cell development occurring in the nodule apex. Infection occurs without cytoplasmic bridge formation, causing vegetative hyphae to proliferate in the cell periphery and requiring much higher rates of infection, relative to other actinorhizae, to efficiently colonize the cell. Multiple infections of the cell produce a number of separate bacterial subcolonies within the plant cell and these develop synchronously to form the multilayered structure of the mature infected cell. A radial array of microtubules is probably responsible for positioning the symbiotic vesicles as a hollow sphere near the central vacuole. During development plasma membranes surrounding individual symbiotic vesicles fuse to cause a large-scale merging of symbiotic vesicles into a common matrix in the mature infected cell. During this process the interfacial matrix around both vegetative hyphae and symbiotic vesicles thickens and changes in quality: immunocytochemistry shows the presence of callose. There is a heterogeneity in nuclear number of infected cells, with most mature infected cells containing eight nuclei.Key words: actinorhiza, bacterial differentiation, callose, cytoskeleton, endoplasmic reticulum, infection.
Isolation and characterization of a cDNA clone encoding polyubiquitin from the root nodule ofElaeagnus umbellata
Authors: Kim Ho Bang , An Chung Sun
Published: April 2011

A cDNA clone encoding polyubiquitin was isolated from a root nodule cDNA library of Elaeagnus umbellata Thunb. by differential hybridization, and its molecular aspects were characterized. The polyubiquitin clone pEuNOD-PUB1 has an insert size of 1642 bp and has the capacity to code for a 458 amino acid residue polyubiquitin protein. The derived amino acid sequence indicates that pEuNOD-PUB1 encodes a polyprotein consisting of six repeats of ubiquitin monomer, except for the last repeat, which has two additional amino acids (Asp-Phe) to be removed in the course of polyubiquitin processing into monomer. The molecular mass of ubiquitin monomer, consisting of 76 amino acids, was predicted to be 8524 Da, and the pI value was predicted to be 7.57. The nucleotide sequence of ubiquitin monomers from pEuNOD-PUB1 showed 73.1-86.0% sequence similarity with those from other organisms. The polyubiquitin mRNA content was four to six times higher in the root nodules than in the leaves and roots. In situ hybridization results showed polyubiquitin transcripts were strongly detected in the meristem zone, in infected cells of the fixation zone, and in the central vascular system. Genomic Southern hybridization revealed that polyubiquitin genes are present as a small multigene family in the genome of E. umbellata.Key words: Elaeagnus umbellata, root nodule, cDNA, polyubiquitin, Northern hybridization, in situ hybridization.
Light quality (red:far-red ratio): does it affect photosynthetic activity, net CO2 assimilation, and morphology of young white clover leaves?
Authors: Heraut-Bron V , Robin C , Varlet-Grancher C , Afif D , Guckert A
Published: April 2011

We assessed the effects of red:far-red (R:FR) ratio on net CO2 assimilation, photosynthetic activity, and morphology of young white clover leaves developed under a simulated canopy light environment. Isolated cuttings of Trifolium repens L. were grown in controlled conditions under two irradiances in combination with two R:FR ratios. We used far-red light emitting diodes to reduce the R:FR ratio on leaves that were successively developing on the main stolon and were subject to strong competition for light within a sward. A leaf that developed under a low R:FR ratio had a lower chlorophyll content than the controls. However, this change had no consequences on the net CO2 assimilation rate and on the biomass allocated to shoots. The low R:FR ratio modified the leaf morphology by increasing the leaf area. A leaf that developed in lower irradiance had a lower net CO2 assimilation rate and a greater leaf area and petiole length than leaves that developed in higher irradiance. Therefore, irradiance was the main factor limiting the leaf CO2 assimilation under a canopy. Capture of light by clover leaves was improved by FR light only via modifications of leaf morphology, because there were no significant effects of FR light on photosynthesis.
Devenir de l'azote minéral dans une tourbière à Sphagnum fallax Klinggr. et Carex rostrata Stokes du Massif central (France)
Authors: Francez André-Jean , Loiseau Pierre
Published: April 2011

The fate of mineral nitrogen (N) in an oligotrophic fen, located in Monts de Forez (Puy-de-Dôme department), was studied by 15N tracking of 0.5 g (nitrogen)·m-2·year-1 ammonitrate labelled on both ions (30% excess). Simulating atmospheric deposits, an important nutrient source in mires, N additions were made at two periods of the year, June and August, 1986, and the fate of the nitrogen was measured in October of the same year. Nitrogen recovery was measured in the living parts of Sphagnum fallax Klinggr., aerial and hypogeous parts of Carex rostrata Stokes, and in peat. Vegetation preferably absorbed nitrogen in June, as compared to August, the period during which nitrogen allocation to hypogeous phytomasses of Carex was the highest. As compared to Carex, Sphagnum has strong nitrogen assimilation and holding potentials. A nitrogen competition potential index or "nitrogen sink power" (PCN), calculated from recovery and stock data, showed that Sphagnum was more efficient at intercepting nitrogen in August, when rainfall is the lowest in the studied area. In peat, nitrogen recovery was strongest in August. Most of the microbial processes seem to occur in the first 10 cm. Gross nitrogen mineralization and immobilization, calculated from organic matter degradation, were estimated as 11.4 and 6.9 g·m-2·year-1, respectively. The gross mineralization estimation according to the method of Fried and Dean was 17.2 g·m-2·year-1. This overestimation might be attributed to an underestimation of the nitrogen derived from input in plants and an overestimation of nitrogen from peat.Key words: 15N, nitrogen balance, nitrogen uptake, competition, retention, turfigenous process.
Diversity and host specificity of ectomycorrhizal fungi retrieved from three adjacent forest sites by five host species
Authors: Massicotte H B , Molina R , Tackaberry L E , Smith J E , Amaranthus M P
Published: April 2011

Seedlings of Abies grandis (Dougl.) Lindl. (grand fir), Lithocarpus densiflora (Hook. & Arn.) Rehd. (tanoak), Pinus ponderosa Dougl. ex Laws. (ponderosa pine), Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir), and Arbutus menziesii Pursh (madrone) were planted in mixture and monoculture in soil collected from three adjacent forest sites in southwestern Oregon (a clearcut area, a 25-year-old Douglas-fir plantation, and a mature 90- to 160-year-old Douglas-fir - pine forest) to determine the effect of host tree diversity on retrieval of ectomycorrhizal morphotypes. In this greenhouse bioassay, 18 morphotypes of mycorrhizae were recognized overall from all soils with a total of 55 host-fungus combinations: 14 types with ponderosa pine, 14 with Douglas-fir, 10 with tanoak, 10 with grand fir, and 7 for madrone. Four genus-specific morphotypes were retrieved (three on ponderosa pine and one on Douglas-fir), even in mixture situations, demonstrating selectivity of some fungal propagules by their respective host. Five types were detected on all hosts, but not necessarily in soils from all sites. The remaining nine types were associated with two, three, or four hosts, which indicates a wide potential for interspecific hyphal linkages between trees. More morphotypes were retrieved from the monoculture treatments compared with the mixture treatments, although the differences were not significant. Several examples of acropetal replacement of one fungus by another (interpreted as succession) were recorded on all hosts during the course of the experiment. These results illustrate the importance of different host species in maintaining ectomycorrhizal fungus diversity, especially fungi with restricted host range, and the strong potential for fungal linkages between trees in forest ecosystems.Key words: fungal succession, fungal communities, compatibility, Arbutus menziesii, Pseudotsuga menziesii, Pinus ponderosa, Abies grandis, Lithocarpus densiflora.
Platanthera lacera × leucophaea, a new cryptic natural hybrid, and a key to northeastern North American fringed-orchids
Authors: Catling Paul M , Brownell Vivian R
Published: April 2011

To evaluate the putative hybrid origin of fringed-orchids from York County, Ontario, morphological attributes of hybrid flowers were evaluated with respect to both a random sample of herbarium specimens and populations from the hybrid location. The putative hybrids were intermediate in spur length, petal width, and vertical distance across opening to the spur as well as in eight other quantitative characters. The hybrid is named Platanthera ×hollandiae Catling & Brownell (= Platanthera lacera (Michx.) G. Don × Platanthera leucophaea (Nutt.) Lindl.). With pale greenish-white flowers, partly reflexed lateral sepals, and a horizontally linear spur opening, the putative hybrid plants resemble P. lacera but can be readily distinguished by their relatively long spurs, relatively broad lateral petals, and ovoid instead of strap-shaped viscidium. A key including characteristics of the column is included that allows the separation of all northeastern North American fringed-orchids and their known natural hybrids.Key words: orchid, hybrid, Platanthera lacera, Platanthera leucophaea, Canada, Ontario.
Seeds of Thalictrum mirabile (Ranunculaceae) require cold stratification for loss of nondeep simple morphophysiological dormancy
Authors: Walck Jeffrey L , Baskin Carol C , Baskin Jerry M
Published: April 2011

Seeds of the eastern North American herbaceous polycarpic perennial Thalictrum mirabile Small have differentiated but underdeveloped (small) embryos that are physiologically dormant at maturity in September. Physiological dormancy was broken effectively by cold stratification at 1°C, but embryos required temperatures [Formula: see text]15:6°C for growth after physiological dormancy was broken. Gibberellic acid substituted for cold stratification. Breaking of physiological dormancy in seeds exposed to natural temperatures in a greenhouse occurred during winter, and embryo growth and germination occurred in late winter - early spring. Furthermore, seeds in the greenhouse remained viable until the second and third (spring) germination seasons. Thus, T. mirabile seeds have the capacity to form a short-lived persistent soil seed bank. Buried seeds of T. mirabile apparently go through an annual dormancy-nondormancy cycle. Seeds buried in September 1994 were nondormant when exhumed in April 1995 and April 1996 and incubated in light at 25:15°C for 2 weeks, but they were dormant in June 1995 and September 1995. Seeds of T. mirabile have nondeep simple morphophysiogical dormancy. This is the first report of nondeep simple morphophysiological dormancy being broken by cold, and not by warm, stratification.
Patterns of clonal occurrence in a mature cottonwood grove along the Oldman River, Alberta
Authors: Gom Lori A , Rood Stewart B
Published: April 2011

The conservation of the remaining riparian woodlands of western North America will benefit from a better understanding of cottonwood (poplar) regeneration. Following our discrimination of the 67 cottonwood clones present in an island population of 391 trunks, the present investigation characterized the grove's clonal architecture in terms of species, sex, spatial patterns, and beaver impacts. Large clones containing up to 53 trunks occurred near the river channel in areas prone to flooding, scouring, deposition, and beaver damage. Populus section Tacamahaca Spach. species Populus angustifolia James and Populus balsamifera L. produced larger (mean diameter = 9.2 m) clones with more ramets (mean = 6.7) than the section Aigeiros Duby species Populus deltoides Bartr. (7.3 m diameter, 2.7 ramets). The increased clonal nature of the Tacamahaca species is probably adaptive along steeper gradient streams in foothill regions where increased physical disturbance encourages clonal sprouting. Conversely, P. deltoides occurs along more gradually sloped reaches with finer substrates and smoother stage patterns that would favor seedling recruitment. The grove's clonal structure accounted for the female-biased sex ratio among trunks (204 females : 116 males) since the sex ratio was even among genets (49 females : 51 males). Clonality has contributed substantially to regeneration and grove composition, favoring certain genotypes and influencing woodland structural diversity and spatial distributions. Clonal characteristics differ across Alberta's cottonwood species and would influence the distribution of these native trees.Key words: asexual reproduction, beavers, clonality, cottonwoods, Populus, sex.
Vegetation development on reclaimed lands in the Coal Valley Mine of western Alberta, Canada
Authors: Strong W L
Published: April 2011

Revegetated lands within the Coal Valley Mine were sampled for species composition, woody plant frequencies, and tree heights. The vegetation on 68 sampled sites was dominated by a mixture of Festuca rubra L. and Trifolium repens L. Four distinctive plant communities were present. A Lodgepole pine/Willow/Lindley's aster community represented the most advanced stage of forest development, having a multilayered structure and composed primarily of indigenous species, although only 19 years old. Deciduous shrubs and trees (<50 cm tall) occurred on 43% of the sites (mean 364 plants/ha). Salicaceae were the primary species. Total plant cover averaged >85% in all community types with plant litter covering >75% of the ground surface. There were 123 plant species found growing on the mine with 77% indigenous species, although they represented <5% of the total vegetation cover. The height of planted Pinus contorta Loudon and Picea glauca (Moench) Voss were modelled over a 24-year period. Both species had reduced height growth and significant attrition for several years after planting. On average, however, surviving trees had 8- and 14-year heights similar to local provincial reforestation standards. It is hypothesized that tree canopy closure is a key factor in facilitating the naturalization of forest understory vegetation on reclaimed lands.Key words: succession, plant community development, afforestation, perturbation.
Phylogenetic analysis of the small subunit ribosomal RNA gene of the hyphochytrid Rhizidiomyces apophysatus
Authors: Hausner Georg , Belkhiri Abbes , Klassen Glen R
Published: April 2011

The potential relationship of the uniflagellate hyphochytrids with biflagellate stramenopiles is still not clearly resolved. Thus, we have expanded the number of isolates and taxa of hyphochytrids compared. The phylogenetic analysis of the small subunit ribosomal RNA sequence of Rhizidiomyces apophysatus Zopf based on neighbour-joining and parsimony methods showed that Hyphochytrium catenoides Karling and R. apophysatus are monophyletic and probably the closest relatives of the oomycetes. Our data also confirmed the monophyly of the stramenopiles, which includes heterokont algae along with nonphotosynthetic fungallike organisms, namely the Oomycota, Hyphochytriomycota, and Labyrinthulomycota.Key words: Hyphochytriomycota, heterokont algae, phylogeny, small subunit ribosomal gene.
STEAM CURING OF PORTLAND CEMENT MORTARS. A NEW CRYSTALLINE SUBSTANCE.: (Preliminary Paper)
Authors: Thorvaldson T. , Shelton G. R.
Published: April 2011

The steam-curing of Portland Cement Mortars in saturated steam at 100°, 125°, 150°, 175° and 200 °C. was studied both as to variations in the tensile strength of 2-day and 28-day mortar briquets and as to the changes which occurred in the crystalline matter in the cement. The rate of hydration of the cement, as shown by the disappearance of the original crystalline material, increased with the temperature of the saturated steam. Crystals of calcium hydroxide appeared almost at once, but after reaching a maximum decreased again in amount. At the same time, a new crystalline product appeared and increased in quantity as the amount of hydrated lime decreased. Some of the chemical properties of the new crystals are given. The stability of the new crystals when exposed to solutions of sulphates indicates that the great increase in the resistance of Portland cement mortars to alkali action produced by steam-curing is connected with the production of this crystalline material.
STUDIES IN ISO-UREAS AND ISO-UREIDES: II. THE CONDENSATION OF ISO-UREAS WITH DIKETONES AND KETONIC ESTERS
Authors: Basterfield Steward , Powell Edward C.
Published: April 2011

This investigation deals with the reaction of ethyl iso-urea with acetyl-acetone, oxalacetic ester, acetone-dicarboxylic ester, and acetyl-pyruvic ester. Several pyrimidines have been synthesised. So far, the condensation of acetyl-pyruvic ester has yielded only gums which could not be purified or converted into crystalline substances.
THE SPECIFIC EFFECTS OF MONOCHROMATIC LIGHT ON THE GROWTH OF PARAMOECIUM
Authors: Hutchinson A. H. , Ashton Miriam R.
Published: April 2011

Paramoecium was irradiated with monochromatic light and it was found that rays of different frequencies have specific effects upon its growth. Certain frequencies in the red, the yellow and the near ultra-violet parts of the spectrum were found to stimulate growth; some as in the green and in the far ultraviolet beyond 3000Å retarded it, and even killed the organism at a very low intensity. Other frequencies retarded or stimulated growth during early exposure and later produced the reverse effects.
STUDIES ON THE ACTION OF SULPHATES ON PORTLAND CEMENT: II. STEAM-CURING OF PORTLAND CEMENT MORTAR AND CONCRETE AS A REMEDY FOR SULPHATE (ALKALI) ACTION
Authors: Thorvaldson T. , Vigfusson V. A. , Wolochow D.
Published: April 2011

A study was made of the effect of steam-curing at various temperatures between 50° and 200 °C. on the resistance of Portland cement mortars to the action of solutions of the sulphates of sodium, magnesium and calcium. The methods used consisted in comparing the expansion of steam-cured and untreated mortar specimens during exposure to the solutions, and in determining the changes in the tensile strength of the more resistant mortars after long periods of exposure.A laboratory study of steam-curing as a remedy for the action of sulphates ("alkali") on Portland cement mortars, was made by determining the effect on the stability of the mortar as indicated by changes in volume and in tensile strength on exposure to sulphate solutions at 21 °C. The effect of steam-curing on the tensile and compressive strength of mortars and concrete was also studied.
CATALYSTS IN THE PREPARATION OF O-BENZOYLBENZOIC ACID AND ETHYLBENZENES BY THE FRIEDEL AND CRAFTS REACTION
Authors: Gallay W. , Whitby G. S.
Published: April 2011

In the preparation of o-benzoylbenzoic acid from benzene and phthalic anhydride, ferric chloride is a much poorer catalyst than aluminum chloride, but an equimolecular mixture of ferric and aluminum chlorides, although less active than aluminum chloride itself, possesses an activity greater than the sum of the activities of its components separately. Ferric chloride is not a catalyst for the combination of benzene and ethylene. Amalgamated aluminum is a better catalyst than aluminum chloride for both of the reactions mentioned.
FREEZING POINTS AND HEAT CAPACITIES OF AQUEOUS SOLUTIONS OF POTASSIUM CHLORIDE
Authors: Barnes W. H. , Maass O.
Published: April 2011

Freezing points for the system KCl–H2O are determined to 0.1° and 0.1% concentration over a range of concentrations including the eutectic. The solubility of potassium chloride in water at 25.22 °C. is measured. The heat capacities of a few rapidly and slowly frozen aqueous solutions of potassium chloride are investigated. The heat capacities of an approximately eutectic aqueous solution of potassium chloride are studied.Supercooling of aqueous solutions of potassium chloride is observed to be a constant factor under fixed cooling conditions, and its magnitude depends on the concentration of the solution. Aqueous solutions of potassium chloride, cooled rapidly to temperatures below the eutectic, are found to have approximately the same heat capacity values as those cooled slowly to the same temperatures. The heat of solution of potassium chloride at −10.7 °C. to form the eutectic concentration is calculated, and the relation between the phase rule diagram and heat capacities is discussed.
THE SPECIFIC EFFECTS OF MONOCHROMATIC LIGHT ON THE GROWTH OF YEAST
Authors: Hutchinson A. H. , Newton Dorothy
Published: April 2011

An isolated strain of Yeast, derived from Fleischman's preparation, when exposed to monochromatic light responds quite differently to light of different wave-lengths. Slight retardation in growth by red and orange light, stimulation by yellow and green, and increasingly marked retardation in the blue and violet, characterize the effects of the mercury lines of the visible spectrum. There is a sudden transition to stimulation in the near ultra-violet. (λ 3984 Å). Stimulation continues at λ 3650 Å and characterises the region λ 2894 Å to λ 2700 Å, but otherwise the lines employed in this investigation retard growth.Generally the effect either of stimulation or retardation is greater when the control is one of rapid growth rate, but the reverse is the case at the red end of the visible spectrum.