bluuebunny/crossref_metadata_2025 huggingface dataset:
Axenic culture of the downy mildew fungus Plasmopara halstedii in Agrobacterium rhizogenes-induced roots of sunflower (Helianthus annuus)
Authors: Zahka G. A. , Virányi F.
Published: December 2007

The downy mildew fungus, Plasmopara halstedii (Farlow) Berlese & de Toni, was cultured axenically in association with sunflower roots derived from petioles inoculated with Agrobacterium rhizogenes. An axenic zoosporangial suspension, obtained from sporulating cotyledons, was added to A. rhizogenes-induced root pieces on agar or in liquid nutrient medium. Roots showed profuse P. halstedii sporulation after 1 week. A comparative study in infection morphology with excised sunflower roots (not induced by A. rhizogenes) of the same cultivar showed no difference, both of which resembled P. halstedii infection in roots from intact plants. The dual-member cultures with A. rhizogenes induced roots were a good source of axenic P. halstedii inoculum, and zoosporangia remained viable for up to 2 monhts in dual-member cultures maintained at 18–20 °C. Noteworthy features were the balanced state of host and parasite and the prolific production of P. halstedii oospores. Key words: downy mildew, sunflower, Plasmopara halstedii, Helianthus annuus, root culture, Agrobacterium rhizogenes.
Two variants of wild emmer (Triticum dicoccoides) native to Israel: morphology and distribution
Authors: Poyarkova Helena , Gerechter-Amitai Z. K. , Genizi A.
Published: December 2007

A detailed morphological comparison between the narrow-spiked and the wide-spiked variants of Triticum dicoccoides growing in Israel revealed significant differences that became evident in almost all organs, both vegetative and reproductive, in juvenile and adult stages, on macro- and micro-morphological levels. Phenologically the two variants are also distinct, the narrow-spiked one usually heading later. While the narrow-spiked form is widely distributed in Israel, covering the entire range of T. dicoccoides in this country, the wide-spiked form is restricted to the vicinity of Lake Kinneret (Sea of Galilee) and to Mt. Gilboa. Spike color was not found to be a stable character in either variant of T. dicoccoides and therefore cannot be used as a criterion for infraspecific taxonomy. A tendency to increase grain number in a spikelet to three was observed in both variants, but it was expressed more strongly in the wide-spiked one. Key words: Triticum dicoccoides, wild emmer, intraspecific variation.
Studies in the Alismataceae. IX. Development of the flower in Ranalisma humile
Authors: Charlton W. A.
Published: December 2007

The solitary flower of Ranalisma humile has three sepals, three petals, 8–12 stamens, and numerous carpels. The first six stamens appear to arise in pairs associated with the petal primordia. With respect to the perianth and the first six stamens, the flower conforms to the basic trimerous pattern detected in other Alismatalean flowers, but it differs in other aspects of development. Organogenesis is unidirectional during the period of sepal and petal initiation, since both sepal and petal initiation occur first on the same side of the flower bud. After the initiation of the first six stamens there is no evidence that subsequent organs are initiated in any semblance of a trimerous pattern. The transition from stamen to carpel initiation occurs at some point after the initiation of the first six stamens, but it does not occur at a fixed point. There are six organogenetic sites above and alternating with the first six stamens, and these may be occupied indifferently by stamen or carpel primorida. The sequence of initiation of further carpel primordia is hard to define, but ultimately carpels appear to be arranged spirally. The features of floral organogenesis are discussed in relation to the position of Ranalisma among the Alismatales. Key words: flower, organogenesis, symmetry, unidirectional development, Ranalisma, Alismataceae, Alismatales.
Demethylation of the lignin model dimer 1-(3′,4′-dimethoxyphenyl)-2-(o-methoxyphenoxy)-propane-1,3-diol by the white-rot fungus Phlebia tremellosa
Authors: Reid Ian D.
Published: December 2007

Phlebia tremellosa dealkylates nonphenolic β-O-4-linked lignin model dimers; the phenolic products are oxidized by laccase. There is no evidence of α,β-cleavage as catalyzed by lignin peroxidase in some other white rot fungi. Methanol is the product of demethylation of 1-(3′,4′-dimethoxyphenyl)-2-(o-methoxyphenoxy)-propane-1,3-diol, and the demethylation reaction can be assayed by the release of radioactive CH3OH from the 4′-O14CH3 labelled compound. In older cultures, the methanol is metabolized to CO2. Demethylation is stimulated by oxygen and blocked by several common metabolic inhibitors. Both the mycelium and the extracellular medium are required for demethylation. Key words: lignin biodégradation, laccase, demethylation, lignin peroxidase.
Mineral analyses of storage reserves of Cucurbita maxima and Cucurbita andreana pollen
Authors: Skilnyk Hilary R. , Lott John N. A.
Published: December 2007

Cucurbita maxima and Cucurbita andreana are so closely related that hybridization is possible. These two species also have been shown to have very different levels of calcium storage in their seeds. Our neutron activation analysis studies have shown that the total amount of P, Ca, K, and Mg in pollen of the two species was similar. Energy dispersive X-ray analysis studies also showed that the composition of electron-dense particles in the tube cells of the two species was similar. Thus the differences in Ca levels in phytate reserves in the seeds of these two Cucurbita species do not appear to be paralleled by differences in mineral reserves in the pollen of the two species. Specimen preparation studies demonstrated that even though elements such as P, K, Mg, and Ca are mostly retained by an anhydrous fixation and embedding protocol, thin-sectioning of such blocks on a water-filled microtome boat resulted in major loss of elements. Key words: pollen, mineral nutrients, energy dispersive X-ray analysis, neutron activation analysis, phytate, Cucurbita.
Morphometric study of three closely related South American species of Hordeum section Stenostachys (Poaceae)
Authors: Baum Bernard R. , Bailey L. Grant
Published: December 2007

This study investigates the morphologically distinguishable characteristics of Hordeum santacrucense Parodi et Nicora and Hordeum setifolium Parodi et Nicora, two recently described species from southern South America that are very similar morphologically, and Hordeum patagonicum (Hauman) Covas, also from southern South America and morphologically similar to the above two species. The three entities have not been kept at the species level by some authors. This paper provides the results of a morphological investigation as justification for their retention at the specific level. The character lemma backs pubescent in about half lower part distinguishes H. patagonicum from the other two; the character lodicules glabrous, or with one or two cilia distinguishes H. setifolium from H. santacrucense with ciliate lodicule margins. Key words: South American Hordeum, multivariate analysis, lodicules, taxonomy.
Phylogenetic relationships among several African Cucumis species
Authors: Staub J. E. , Knerr L. D. , Holder D. J. , May B.
Published: December 2007

Cotyledons of seven African species within Cucumis, subgenus Melo, subgroup Myriocarpus (4x C. aculeatus, C. anguria var. anguria Meeuse, C. dipsaceus Ehrenb. ex Spach, C. ficifolius A. Rich, C. myriocarpus ssp. leptodermis Schweik., C. prophetarum, and 2x and 4x C. zeyheri Sond.), and 2x C. sativus L. of subgenus Cucumis were surveyed using horizontal starch gel protein electrophoresis to characterize interspecific and intraspecific variation. Cluster and classification and regression tree analysis of allelic frequencies among 14 polymorphic loci indicated that C. myriocarpus ssp. leptodermis, C. prophetarum ssp. dissectus, C. ficifolius, C. anguria var. anguria, and 2x and 4x C. zeyheri have biochemical affinities and could be distinguished from C. aculeatus and C. dipsaceus, which were similar. Within the first group, C. myriocarpus ssp. leptodermis and C. prophetarum ssp. dissectus accession formed a well-defined group. Cucumis prophetarum ssp. dissectus was more similar to C. myriocarpus ssp. leptodermis than to the C. ficifolius accessions evaluated. In the second group, two C. zeyheri accessions (C81321, C80346) were more similar to C. prophetarum ssp. prophetarum (C82069) than four other C. zeyheri evaluated. Cucumis sativus was dissimilar from all other species studied. Key words: evolution, biochemical genetics, isozymes.
Cytology and genetics of a dikaryotic strain of Lentinus edodes carrying two haplolethal factors
Authors: Hasebe K. , Murakami S. , Tsuneda A.
Published: December 2007

Basidiospore progeny of a dikaryotic strain (TMI-655) of Lentinus edodes showed abnormalities in germination and subsequent hyphal growth. In the basidia, meiosis and sporulation completed normally, and mature, uninucleate basidiospores were formed. On agar medium, about half of the basidiospores either failed to germinate or ceased to grow at early stages of germination (mostly before septation) and then degenerated. Among these, irregularly swollen spores showing an apparent sign of wall autolysis were commonly observed. The other half of the basidiospores succeeded in germination and developed into multicellular germlings, but only half of them (i.e., approximately one-quarter of the initial population) survived and formed colonies. Those germlings that failed to form colonies were characterized by spherical swellings, abnormal branching, and eventual death of the component cells. These results indicated the presence of two recessive haplophasic lethal factors that segregated independently and were operative at different developmental stages. Genetic analysis showed that both of the lethal factors were carried by one of the component nuclei of TMI-655 and were transmitted through dikaryotic–monokaryotic matings, and that one of the lethal factors was linked to the A incompatibility factor. Key words: cytology, genetics, basidiospore germination, haplolethal factor, Lentinus edodes.
Classification and ordination of southern boreal forests from the Hondo – Slave Lake area of central Alberta
Authors: Roi George H. La
Published: December 2007

Sixty-five undisturbed stands, spanning a wide range of physical habitats in the southern boreal subzone, were sampled in central Alberta using relevés, then classified with two-way indicator species analysis (TWINSPAN) and ordinated with detrended correspondence analysis (DECORANA), based on the estimated midsummer percent cover of 100 vascular plant species. Six floristically and ecologically distinct community types were recognized along soil-moisture and texture–nutrient gradients: oligotrophic PINUS BANKSIANA/ASTER LAEVIS on warm, xeromesic, nutrient-poor sand deposits; oligo-mesotrophic PINUS BANKSIANA/CORNUS CANADENSIS on cooler, xeromesic to submesic, low-nutrient sands; mesotrophic PICEA GLAUCA – POPULUS TREMULOIDES/ELYMUS INNOVATUS on mesic, medium-nutrient tills; eu-mesotrophic PICEA GLAUCA – POPULUS TREMULOIDES/RIBES TRISTE on mesic to hygromesic, nutrient-rich alluvium and till; oligotrophic PICEA MARIANA/RUBUS CHAMAEMORUS on cool, hygromesic to hygric, nutrient-poor peatlands; oligotrophic PICEA MARIANA/CAREX AQUATILIS on hygric to hydric, low-nutrient peatlands. The six community types and 19 species groups elucidated by TWINSPAN occupy distinct sectors on the two-dimensional DECORANA ordination that are associated with differences in moisture and nutrient availability. The community types are ecologically vicarious with boreal forest assemblages previously described for Alaska, central and eastern Canada, and northwestern Europe. Key words: cover, ecological series, gradient, moisture, nutrients, plant community, soil, vascular plant species, vegetation.
Variation in clonal structure in an eelgrass (Zostera marina) meadow on the Pacific coast of Canada
Authors: Harrison Paul G. , Durance Cynthia
Published: December 2007

The seagrass Zostera marina L. was studied in southwestern British Columbia at a site where habitat quality has been altered by construction of a port. Morphology, shoot density, and electrophoretic banding patterns for eight enzyme systems were compared in plants from locations that represented the center of the original population (main), a marginal habitat colonized by seedlings, a remnant isolated by changes in drainage patterns, and the subtidal edge of the main bed (deep). Compared with the original population, both the colony and remnant populations had lower shoot densities and shorter shoots. The mean number of banding patterns was lower at the colony and deep locations than at the main location. Clonal diversity was lowest at the main and deep locations. As expected, the colony population shared no clones with the original population. The absence of shared clones in the remnant and original populations suggests that sexual reproduction and seedling establishment are more important in the dynamics of perennial eelgrass populations than is generally believed. Electrophoretically the plants at the seaward margin of the site were the most distinct and uniform; their relation to the other plants is unknown. Key words: clonal plant, electrophoresis, microgeographic variation, population genetic structure, Zostera marina.
Copper and nickel pollution: frequency of endophytic fungi in Scots pine shoots and endophyte growth in vitro
Authors: Ranta H. , Neuvonen S. , Kääriäinen S. , Vesanto S.
Published: December 2007

The frequency of endophytic microfungi was measured from current-year shoots of Scots pine trees growing in Harjavalta, a heavily polluted area in western Finland. The copper (Cu) and (Ni) concentrations in bark plus phloem and needles of the same trees were measured. The frequency of isolates of endophytic taxa were either negatively (Hormonema sp. 2 and Sterile sp. 1) or positively (Hormonema sp. 1, BL132) correlated with the Cu and Ni concentration of bark plus phloem. Isolates of the most common endophytic taxa and the pathogenic Gremmeniella abietina from Harjavalta were grown in vitro in different levels of Cu (0.6 – 126 μg/mL) and Ni (0.3 – 50 μg/mL) separately and in combination. This experiment included also isolates of G. abietina and Hormonema sp. 1 from the northern (unpolluted) area. The concentrations of Cu and Ni that reduced the linear growth to 50% of control were estimated. The endophyte taxa with positively correlated frequency with increasing concentration of Cu and Ni in the shoots were able to withstand elevated levels of Cu and Ni in vitro. Compared with most of the other fungi, G. abietina isolates were particularly sensitive to addition of Ni. No evidence for intraspecific adaptation of G. abietina and Hormonema sp. 1 to Cu and Ni was found. Key words: endophyte, Gremmeniella, heavy metal, Hormonema, Scots pine.
Viability of aquatic hyphomycete conidia in foam
Authors: Sridhar K. R. , Bärlocher Felix
Published: December 2007

The viability of aquatic hyphomycete conidia trapped in foam was estimated with tetrazolium bromide. In fresh foam, 76 – 91% of all conidia had at least one viable cell; in old foam, these values were 20 – 43%. The average number of viable cells per conidium was higher in fresh than in old foam. Laboratory-produced conidia of Heliscus lugdunensis and Articulo-spora tetracladia had much higher numbers of viable cells than field-collected conidia. Viability as defined in this study (at least one viable cell per conidium) proved to be an excellent predictor of ability to germinate. Conidia of four species (two Canadian and two Indian strains) did not survive for more than 24 d when exposed to −17 °C, or to freeze – thaw cycles. Persistence of conidia through unfavourable conditions therefore seems limited. Key words: aquatic hyphomycetes, conidia, viability, germination.
Seedling establishment from seeds and seed banks in forests under long-term pollution stress: a potential for vegetation recovery
Authors: Komulainen M. , Vieno M. , Yarmishko V. T. , Daletskaja T. D. , Maznaja E. A.
Published: December 2007

Seed germinability of some common dwarf shrubs and seed-bank composition were studied in young pine forests along a pollution gradient from Severonickel smelter in Monchegorsk, northern Russia. Samples for seed germination and seed-bank trials were taken from sites representing different zones of pollution. Generally, germinability of dwarf shrub seeds was not affected by distance from pollution source, except for Empetrum nigrum ssp. hermaphroditium. The average density per site of seedlings that emerged from seed-bank samples varied between 278 and 416 seedlings/m2. Empetrum nigrum ssp. hermaphroditum and Betula sp. dominated in seed banks. Calluna vulgaris was also numerous at one site. As a whole, seed-bank taxa were well represented in the above ground vegetation. There were no significant differences in seedling density between sites for dominant taxa. Our results indicate that seeds can retain viability even under a heavy pollution load and thus form a potential for vegetation recovery in polluted sites. Key words: seed germination, seed bank, recovery, pollution, coniferous forest.
Effects of mycorrhizae, phosphorus availability, and plant density on yield relationships among competing tallgrass prairie grasses
Authors: Hetrick B. A. D. , Hartnett D. C. , Wilson G. W. T. , Gibson D. J.
Published: December 2007

A replacement series experiment was used to investigate the effects of mycorrhizae, phosphorus availability, and plant density on competitive relationships between three tallgrass prairie species of varying mycorrhizal dependencies. Under mycorrhizal conditions, the obligately mycorrhizal dependent warm-season grass Andropogon gerardii (big bluestem) was a better competitor in mixture with the nonmycorrhiza-dependent cool-season grass Koeleria pyramidata (Junegrass). In the absence of mycorrhizae, however, competitive effects of big bluestem were greatly reduced and Junegrass experienced competitive release. Relative yield totals increased when mycorrhizae were suppressed, suggesting greater intensity of interspecific competition in the presence of mycorrhizae. Thus, the competitive dominance of big bluestem in tallgrass prairie is strongly related to its mycorrhizal status. Elymus canadensis (Canada wild rye) outcompeted big bluestem both with and without mycorrhizae. Relative yield totals of this species mixture were also lower under mycorrhizal conditions, indicating that mycorrhizae increase the intensity of interspecific competition between them. Relative yields of wild rye competing with big bluestem increased in the absence of mycorrhizae, suggesting that it also experiences competitive release when big blue-stem are not mycorrhizal. The outcomes of competition were generally similar among the three total plant density treatments and between P-fertilized and nonfertilized treatments. However, interactions between mycorrhizal effects and plant density confirm that outcomes of interspecific competitive interactions may be density dependent in some cases. Key words: arbuscular mycorrhizae, de Wit replacement series, Andropogon gerardii, Elymus canadensis, Koeleria pyramidata.
Light and electron microscopy of the host–fungus interaction in the achlorophyllous gametophyte of Botrychium lunaria
Authors: Schmid E. , Oberwinkler F.
Published: December 2007

The host–fungus interaction between the achlorophyllous gametophyte of Botrychium lunaria and its fungal endophyte was studied by means of light and electron microscopy. Aseptate hyphae with a multilayered cell wall formed intracellular coils. The interface consisted of a thick layer of fibrillar matrix material, an electron-translucent zone, and the host plasmalemma. Several vesicles that show different stages of development and degeneration occurred within one host cell. Degenerating vesicles were encased by large amounts of an electron-translucent material. Arbuscules were not observed. The fungus did not infect the young sporophyte but degenerated within intact gametophyte cells. Key words: Botrychium lunaria, gametophyte, mycorrhiza, ultrastructure.
Nutritional and environmental factors affecting growth and antifungal activity of a sterile red fungus against Gaeumannomyces graminis var. tritici
Authors: Shankar M. , Kurtböke D. I. , Sivasithamparam K.
Published: December 2007

Growth and antifungal activity of a sterile red fungus against Gaeumannomyces graminis var. tritici (the take-all fungus) in vitro was greatly influenced by nutritional and environmental conditions. The utilization by the sterile red fungus of various carbon and nitrogen sources differed considerably at pH 5.5 and 6.5. Maximum growth of the sterile red fungus occurred when pectin was supplied as the carbon source at both pH levels. As nitrogen sources, NH4H2PO4 supported maximum growth at pH 5.5, whereas Ca(NO3)2 was the best at pH 6.5. Pectin strongly enhanced the antifungal activity of the sterile red fungus towards the take-all fungus as did Ca(NO3)2 supplied as a N source. There was, however, little or no antagonism in the presence of calcium citrate, arabinose, leucine, or arginine. In general, antagonism was optimal at 20 °C and at pH 5.5. Key words: sterile red fungus, Gaeumannomyces graminis var. tritici, biological control.
Species enrichment in a transitional landscape, northern lower Michigan
Authors: Scheiner Samuel M. , Istock Conrad A.
Published: December 2007

The hemlock – white pine – northern hardwood forest region of North America is a transition between the deciduous forests to the south and the boreal forests to the north. In a survey of vascular plant communities in northern lower Michigan we examined species diversity and landscape pattern. Surveying 47 sites we found 483 vascular plant species: 37 tree species, 67 shrub species, 4 vine species, and 375 herbaceous species; there was a mean of 74.3 ± 4.2 species per site. Mean Jaccard similarity among sites was 0.22 ± 0.01 and mosaic diversity, a measure of landscape complexity, was 3.01 ± 0.03. Using nonmetric multidimensional scaling and cluster analysis, two distinct groups of communities were differentiated: group I consisted of communities on mesic upland to wet lowland sites dominated by sugar maple, beech, hemlock, cedar, tamarack, and spruce; group II consisted of communities on xeric to dry-mesic upland moraines and level plains dominated by pines, red oak, birch, and aspen. Each group encompassed a separate south to north transition. Contrary to continental trends, species richness was greatest in sites with the greatest percentage of northern species. The region is more species-rich than adjacent regions to the south and north. We present four hypotheses to explain this species enrichment. Key words: boreal forest, deciduous forest, diversity, hemlock – white pine – northern hardwood forest, transition zone.
Early cellular events during organogenesis and somatic embryogenesis induced on immature zygotic embryos of sunflower (Helianthus annuus)
Authors: Bronner R. , Jeannin G. , Hahne G.
Published: December 2007

Both organogenesis and somatic embryogenesis can be induced in 6-mm immature zygotic embryos of sunflower, depending on the sucrose concentration of the induction medium; shoots were induced at a concentration of 3%, while embryos were formed at 12%. Both morphogenic events were direct, without intervening callus formation, and occurred in the lower third of the hypocotyl. Shoots and somatic embryos had a multicellular origin. They were initiated by periclinal cell divisions in the epidermis and the outer cell layers of the hypocotyl cortex within the 1st day of culture. The two types of morphogenic events could already be distinguished on the 2nd day of culture, in that proteins and lipids started to accumulate in the somatic embryogenic tissues but not in the shoot tissues. This system provides a model that can be used to study early biochemical and molecular events taking place in explants at the onset of organogenesis and somatic embryogenesis, as these two processes occur in a predictable manner and location. Key words: cytology, organogenesis, somatic embryogenesis, storage products, sucrose concentration, sunflower.
Ferredoxin–NADP+ reductase is the site of oxygen reduction in pseudocyclic electron transport
Authors: Goetze D. Christoper , Carpentier Robert
Published: December 2007

The effects of ferredoxin (Fd) and Fd–NADP+ reductase (FNR) on the oxygen photoreduction by photosystem I (PS I) in spinach (Spinacia oleracea L.) thylakoid membranes were investigated using a unique photoelectrochemical cell. This cell was previously shown to monitor the Mehler reaction products of photosynthetic oxygen reduction and represents an excellent tool for studying pseudocyclic electron transport. The magnitude of the photocurrent produced by the thylakoids was increased by as much as 40% in the presence of 60 μM Fd. If thylakoids were supplemented by both Fd and FNR, an additional increase of photocurrent was observed. All these reactions were inhibited by catalase, an enzyme that degrades H2O2, to demonstrate that O2 reduction was involved in all the photoreactions studied. The fact that more O2 was consumed in the presence of FNR was interpreted as evidence that the most effective site of oxygen reduction on the acceptor side of PS I is on FNR and not on Fd. The in vivo implication is that during pseudocyclic electron transport, NADP+ and oxygen directly compete for PS I electrons, with the former having significantly faster reaction kinetics. The advantageous physiological consequences of such a competition are (i) pseudocyclic electron transport would represent a true attenuating mechanism of the redox state of the NADP+–NADPH pool, (ii) oxygen would be a contingent acceptor under high illumination stress, helping to cope with the resultant elevated electron transport rates, and (iii) this mechanism is indisputably a faster response to stress than cyclic electron transport. Key words: Spinacia oleracea, photosystem I, thylakoid membranes, ferredoxin–NADP+ reductase, pseudocyclic electron transport, photoelectrochemistry.
Thiol and amino acid composition of the xylem sap of poplar trees (Populus ×canadensis 'robusta')
Authors: Schneider Andrea , Kreuzwieser Jürgen , Schupp Robert , Sauter Jörg J. , Rennenberg Heinz
Published: December 2007

Xylem sap of poplar trees was collected by vacuum extraction. Samples were taken year round and concentrations of thiols as well as amino acids were determined. Throughout the season glutathione was the predominant thiol in the xylem sap of poplar trees with concentrations ranging from 0.1 to 13 μM. Cysteine and γ-glutamylcysteine concentrations were 0.1–4 and 0.01–3 μM, respectively. The glutathione content was subject to strong seasonal fluctuations. Highest amounts of glutathione (13 μM) were observed in March, immediately before flowering of the catkins. Like γ-glutamylcysteine and cysteine, glutathione values reached further maxima at the onset of budbreak and leaf expansion in April and May. Also the amino acids investigated (glutamine, asparagine, glutamic acid, methionine, arginine) showed strong seasonal fluctuations in the xylem sap of poplar, with glutamine being the most abundant organic nitrogen compound (max. 13 mM). Highest amounts of amino acids were detected during April and May, the period of budbreak and leaf expansion, presumably owing to an increased degradation of storage protein. The sulfur-containing amino acid methionine was present in high amounts during the early growing season. It appeared to be the dominant reduced sulfur compound translocated in the xylem sap of poplar trees in April and May, whereas glutathione was the predominant organic sulfur compound in the xylem sap in March. The significance of storage and mobilization of reduced sulfur and organic nitrogen compounds for development of reproductive (catkins) and vegetative tissue (leaves and sprouts) in poplar trees is discussed. Key words: xylem sap, amino acid, thiol, transport, storage, mobilization.
Floral organ initiation and development in wild-type Arabidopsis thaliana (Brassicaceae) and in the organ identity mutants apetala2-1 and agamous-1
Authors: Crone Wilson , Lord Elizabeth M.
Published: December 2007

The flowers of Arabidopsis thaliana (Brassicaceae) were examined for histological events during organ initiation and later development. An inflorescence floral plastochron of the main stem raceme was used as a basis for the timing and staging of developmental events. Sepals, petals, stamens, and carpels in wild-type Landsberg erecta Arabidopsis are distinguishable as primordia in terms of cell division events associated with initiation, size, and component cell numbers. Flower organogenesis in the organ identity (homeotic) mutants apetala2-1 and agamous-1 was compared with that of the wild type. In both mutants, each whorl of floral organs initiates much like the wild type and only subsequently produces visibly altered organs with mosaic features. The flower organ identity mutants achieve their mature phenotypes by alterations in tissue differentiation that occur after initiation and early primordial development. Key words: Arabidopsis, apetala2-1, agamous-1, plastochron, homeosis, flower.
Antifungal compounds in aspen: effect of water stress
Authors: Kruger Brian M. , Manion Paul D.
Published: December 2007

A thin layer chromatography bioassay was used to detect antifungal compounds in tissue culture plantlets and potted seedlings of aspen. Catechol and the phenolic glycosides salicin and salicortin were identified as inhibitory compounds; a fourth compound was observed but was not identified. Inhibitory compound levels were estimated in eight tissue culture clones grown on unamended media and media amended with 0.22 M mannitol to induce water stress. Aspen tissue culture plantlets grown under water stress conditions had significantly lower levels of catechol, salicortin, and salicin. Significant clonal variation in levels of catechol, salicin, and the unidentified compound was also observed. Catechol, salicortin, and salicin were inhibitory to Hypoxylon mammatum when tested at levels similar to those employed in the thin layer chromatography bioassay. These results suggest that a reduction in the levels of inhibitory compounds in water-stressed aspen may be a factor in the water stress induced susceptibility of aspen to H. mammatum. Key words: Populus tremuloides, Hypoxylon mammatum, water stress, tissue culture.
Immunocytochemical localization of callose in the vascular tissue of tomato and cotton plants infected with Fusarium oxysporum
Authors: Mueller W. C. , Morgham A. T. , Roberts E. M.
Published: December 2007

Callose (β-1,3-glucan) was localized with the electron microscope in the contact cells surrounding vessels of tomato and cotton infected with Fusarium oxysporum by means of gold labelling with a polyclonal antiserum to β-1,3-glucan. The callose was deposited in the apposition layers formed after infection in the cells surrounding initially infected vessels. Callose was not detected in the contact cells surrounding secondarily infected vessels. Callose could be detected in the contact cells of resistant and susceptible tomato cultivars 4 h after inoculation. Key words: β-1,3-glucans, contact cells, gold labelling, Gossypium, Lycopersicon esculentum.
Species of Cortinarius subgenus Leprocybe, sections Orellani and Limonei, in North America
Authors: Thorn R. G. , Malloch D. W.
Published: December 2007

Descriptions and a key are provided to seven species of Cortinarius subg. Leprocybe, sect. Orellani and Limonei, that are found in North America, namely C. callisteus (synonym C. croceocolor), C. distans var. olympianus, C. gentilis (synonym C. confusus), C. limoneus (synonym C. whiteae), C. morrisii, C. rainierensis, and C. speciosissimus. Of these, C. rainierensis and C. speciosissimus were previously shown to contain the nephrotoxin orellanine. Reports of C. orellanus from North America were based on misidentifications of C. uliginosus or similar species of subg. Dermocybe. There are no apparent morphological features to distinguish C. speciosissimus, which has been found in eastern North America, from C. rainierensis, which is known only from the state of Washington in western North America, or from C. orellanoides, which was described from France. Since morphological characters were found for the distinction of sibling species discovered by biochemical and genetic studies in other genera, including Armillaria, we prefer not to accept or suggest the synonymy of these taxa until neotypes or lectotypes are selected for C. croceocolor and C. rubellus and these specimens are compared with types of the other available names using chromatography of fluorescent compounds or rDNA sequences. Key words: biosystematics, mushroom poisoning, orellanine.
Effects of elevated CO2 on time of flowering in four short-day and four long-day species
Authors: Reekie J. Y. C. , Hicklenton P. R. , Reekie E. G.
Published: December 2007

This study was undertaken to determine if the effect of elevated CO2 on flowering phenology is a function of the photoperiodic response of the species involved. Four long-day plants, Achillea millefolium, Callistephus chinensis, Campanula isophylla, and Trachelium caeruleum, and four short-day plants, Dendranthema grandiflora, Kalanchoe blossfeldiana, Pharbitis nil, and Xanthium pensylvanicum, were grown under inductive photoperiods (9 h for short day and 17 h for long day) at either 350 or 1000 μL/L CO2. Time of visible flower bud formation, flower opening, and final plant biomass were assessed. Elevated CO2 advanced flower opening in all four long-day species and delayed flowering in all four short-day species. In the long-day species, the effect of CO2 was primarily on bud initiation; all four species formed buds earlier at high CO2. Bud development, the difference in time between flower opening and bud initiation, was advanced in only one long-day species, Callistephus chinensis. Mixed results were obtained for the short-day species. Elevated CO2 exerted no effects on bud initiation but delayed bud development in Dendranthema and Kalanchoe. In Xanthium, bud initiation rather than bud development was delayed. Data on bud initiation and development were not obtained for Pharbitis. The negative effect of CO2 upon phenology in the short-day species was not associated with negative effects on growth. Elevated CO2 increased plant size in both long-day and short-day species. Key words: phenology, bud initiation, flower opening, size at flowering, photoperiodism.
Primary nitrogen assimilation in higher plants and its regulation
Authors: Oaks Ann
Published: December 2007

Characteristics of the enzymes involved in the assimilation of NO3− and NH4+, in particular the nitrate and nitrite reductases, glutamine synthetase, glutamate synthase, glutamate dehydrogenase, glutamate decarboxylase, and asparagine synthetase, are described. The cellular organization of these enzymes in root and leaf tissues are assessed in view of recent research developments that utilize various tissue blotting techniques. Regulation of nitrate assimilation is analyzed at the physiological, biochemical, and molecular levels. Key words: nitrate, ammonium, assimilation, regulation.
Clonal integration in Spartina patens across a nitrogen and salinity gradient
Authors: Hester M. W. , McKee K. L. , Burdick D. M. , Koch M. S. , Flynn K. M. , Patterson S. , Mendelssohn I. A.
Published: December 2007

We investigated physiological integration among ramets of Spartina patens when clones spanned a salinity gradient. Clones of S. patens were grown in paired pots with the ramets of the parent pot connected to the ramets of the daughter pot via a common rhizome. Half of these clones had the rhizome connection between parent and daughter pots severed immediately prior to treatment application. The parent pots were kept at low salinity (34.2 mM NaCl) and given two levels of labeled 15NH4Cl (0.036 or 0.714 mM NH4Cl). Daughter ramet pots were kept at the low N level (unlabeled 0.036 mM NH4Cl) and exposed to an increase in salinity to 513 mM NaCl. After 7 days, all daughter ramets had significantly elevated leaf Na levels. Daughter ramets connected to parents were able to maintain significantly greater leaf elongation rates than severed daughter ramets. Labeled 15N was translocated from parents to connected daughter ramets and high-N parents translocated more N to the belowground tissue of daughter ramets than low-N parents. Leaf proline, a nitrogen-containing osmoticum that accumulates only after a threshold of salinity stress is exceeded, was significantly increased only in severed daughter ramets, indicating that salinity stress was reduced in connected daughter ramets, possibly via parental water translocation. Key words: clone, physiological integration, proline, ramet, salt marsh, salt stress.
Subcellular localization of polyamines in embryogenie callus of white spruce (Picea glauca)
Authors: Amarasinghe Vindhya , Carlson John E.
Published: December 2007

Polyamines were localized in embryogenic callus cells of Picea glauca by the fluorescent dye o-phthalaldehyde and polyclonal antibodies raised against putrescine, spermidine, and spermine. Localization by both methods showed higher levels of polyamines in the nuclei and nucleoli than in the cytoplasm. In contrast with previous reports on cytochemical localization of polyamines in animal cells, stain was always excluded from the condensed chromatin of spruce somatic embryo cells. Key words: polyamines, cytochemistry, immunolocalization, white spruce.
Preparation of an antibody against a maize DNA polymerase holoenzyme: identification of the polymerase catalytic subunit
Authors: Coello-Coutiño P. , García-Ramírez E. , Vázquez-Ramos J. M.
Published: December 2007

Three different DNA polymerase activities can be separated from germinating maize axes through DEAE – cellulose chromatography. Of these, DNA polymerase 2 appears to be a replicative-type enzyme composed of several subunits. An antibody has been developed against the DNA polymerase 2 multisubunit complex, which mainly recognizes a polypeptide of molecular weight around 90 kDa. Polypeptides of molecular mass of 83, 70, 60, 55, 45, and 24 kDa are also recognized. Activity gels showed that the 90-kDa polypeptide possesses catalytic activity. DNA polymerases 1 and 3 are not recognized by the antibody and their activities are not reduced. However, DNA polymerase 2 activity is reduced by 70%. The nature of the different DNA polymerase accompanying subunits is discussed. Key words: DNA polymerases, maize embryo axes.
Additional clarification of the Medicago blancheana-bonarotiana-rotata complex
Authors: Small Ernest
Published: December 2007

This eastern Mediterranean complex consists of two annual species, between which there is substantial hybridization. Examination of type specimens showed that the two species are correctly named Medicago rotata Boiss. (a well-established usage) and Medicago bonarotiana Arcangeli (a name that has competed with Medicago blancheana Boiss.). The type of M. blancheana Boiss. is a hybrid of the two species, and the name has therefore been inappropriately used to designate the species that should be called M. bonarotiana. A key to the taxonomic components of the complex is provided. Key words: Medicago blancheana, Medicago rotata, Medicago bonarotiana, taxonomy.
Differences in recovery between a deciduous and an evergreen ericaceous clonal dwarf shrub after simulated aboveground herbivory and belowground damage
Authors: Tolvanen Anne
Published: December 2007

Insect and microtine rodent herbivory (defoliation and branch clipping, respectively) were simulated in stands of the deciduous Vaccinium myrtillus L. and evergreen V. vitis-idaea L. Rhizome connections around the treated plots were either left intact or severed. Recovery in the plots was monitored for two growth seasons, from 1991 to 1992. It was hypothesized that the evergreen V. vitis-idaea would suffer more from the simulated herbivory treatment than V. myrtillus, but that severing the rhizome connections would decrease recovery of both species, because clonal integration is disrupted and wounding may have a harmful influence on growth. After two growth seasons, recovery was complete from simulated herbivory in V. myrtillus, whereas the new dry biomass was reduced slightly (22 – 37%) or significantly (49%) compared with that of the control in V. vitis-idaea. Rhizome severing reduced the growth of the branches and ramets and the aboveground dry biomass by 34% compared with that of the unsevered control in V. myrtillus. In the evergreen V. vitis-idaea, severing slightly reduced growth, the effect being significant only in the clipped treatment. The results suggest that the deciduous V. myrtillus recovers more rapidly from simulated herbivory than the evergreen V. vitis-idaea. Rhizome severing is more detrimental to the growth of V. myrtillus, but less detrimental to recovery from simulated herbivory. Sexual reproduction decreases more in V. vitis-idaea than in V. myrtillus after damage. Key words: compensation, growth form, herbivory, rhizome severing, Vaccinium
Interactions between Norway spruce (Picea abies) and Heterobasidion annosum. II. Infection of woody roots
Authors: Heneen W. K. , Gustafsson M. , Brismar K. , Karlsson G.
Published: December 2007

Woody roots, 2 – 4 mm in diameter, of Norway spruce (Picea abies) were inoculated with an S strain of Heterobasidion annosum. After 8 – 20 days the roots were prepared for examination by light microscopy as well as transmission and scanning electron microscopy. The roots had one or several periderms and sometimes remnant cortex cells on the surface. The fungal infection was restricted to the remnant cortex cells and the rhytidome after an incubation period of 20 days. Accumulation of granular materials, most likely phenolic in nature, prevailed in the infected periderm cells. Fungal hyphae enclosed in these materials showed signs of degeneration. Based on these results, we conclude that the rhytidome acts as a successful barrier to infection of the inner parts of the root for at least 20 days following inoculation with H. annosum. Both structural and chemical defence mechanisms are involved. Key words: Norway spruce, Heterobasidion annosum, root infection, woody roots, microscopy.
Nitrogen fixation and photosynthesis in high arctic forms of Nostoc commune
Authors: Lennihan R. , Chapin D. M. , Dickson L. G.
Published: December 2007

Nostoc commune, a colonial cyanobacterium, has been suggested as an important contributor of nitrogen to terrestrial ecosystems in the Canadian High Arctic, yet little is known about the ecophysiology of this organism in arctic environments. This study focused on the physiological performance of macroscopic colonies of N. commune found on Devon Island, N.W.T. The objectives were to examine the influence of temperature, colony morphology, and seasonal phenology on nitrogen fixation rates and the effects of light and temperature on photosynthesis. Maximum rates of acetylene reduction in N. commune (2119 nmol C2H4∙g−1∙h−1) were higher than those previously recorded for arctic N. commune but lower than values reported for temperate poulations. Depending on the time of the growing season, the temperature optimum for acetylene reduction varied from 15 °C to greater than 20 °C. Photosynthetic temperature optima did not occur below 20–25 °C (the highest temperatures measured). Light saturation of photosynthesis was reached at low levels of irradiance (100–150 μmol∙m−2∙s−1 PPFD). Acetylene reduction rates varied strongly with colony morphology. Thin, fragile, flattened colonies had higher rates than thicker, more resilient, flattened colonies or spherical colonies. Cold post-thaw temperatures appeared to delay the recovery of maximum nitrogen fixation rates for 2–3 weeks following the onset of the growing season. Compared with two other species of cyanobacteria present on Truelove Lowland (Gloeocapsa alpina and Gleotrichia sp.), N. commune had higher rates of nitrogen fixation. Key words: Nostoc commune, cyanobacteria, High Arctic, nitrogen fixation, photosynthesis.
Root hair infection process and myconodule formation on Alnus incana by Penicillium nodositatum
Authors: Sequerra Jeanine , Capellano André , Faure-Raynard Monique , Moiroud André
Published: December 2007

Penicillium nodositatum infects the roots of alder trees and induces the formation of structures called myconodules, which are similar to young actinorhizae. Root infection of Alnus incana by P. nodositatum as well as myconodule development were studied by light and electron microscopy and observations were compared with those described for the infection by Frankia spp. We have established an obvious homology between the early steps of the infection caused by both microorganisms. The presence of the fungus near the roots induces deformation of root hairs. The infection site is probably localized in a folding of a deformed hair. As soon as hyphae penetrate into the hair, they become enclosed in a polysaccharide matrix. Initially, P. nodositatum colonizes a region near the infected root hair that may correspond to a slightly developed prenodule. Then a nodular primordium is initiated at some distance from the initial contact and the new nodular cortex is invaded by the fungus. The zone of infection is limited to the cortical cells by a barrier of tannins. Myconodules remain small and unilobed and have an outer morphology similar to that of an incompatible Frankia nodule. Key words: Alnus, myconodule formation, Penicillium, root hair infection.
Premières données sur l'architecture comparée des systèmes racinaires et caulinaires
Authors: Atger Claire , Edelin Claude
Published: December 2007

Since 1970, the architectural analysis of woody plants has given much information about structural and functional organization of tree crowns, their development, and reiteration patterns. In this study, we have extended this method to tree root systems. We describe the whole architecture of three species and we compare their root system and crown architectural patterns. Key words: architecture, tree, root system, crown, whole plant.