bluuebunny/crossref_metadata_2025 huggingface dataset:
The colonization of dung pats and molehills in permanent pastures
Authors: Parish Roberta , Turkington Roy
Published: April 2011

The colonization of areas affected by molehills and dung pats was monitored in three adjacent pastures of different ages. Seedling establishment was infrequent, and most colonization took place by rhizomes, e.g., Agropyron repens and Poa compressa, or by stolons, e.g., Trifolium repens. Tillering species, e.g., Dactylis glomerata, Holcus lanatus, and Lolium perenne, were poor colonizers of disturbed areas. Invasion of gaps by a species was not proportional to its abundance in the pasture. Individual plants are eliminated at random by the disturbances. Small-scale disturbances tend to decrease community heterogeneity. Key words: disturbance, colonization, dung, molehill, pasture.
Phytochrome action and water status in seed germination of wild oats (Avena fatua)
Authors: Hou J. Q. , Simpson G. M.
Published: April 2011

Freshly harvested seeds of the genetic line CS40 of wild oats (Avena fatua L.) germinated in the dark. Brief (15 min) exposure to far-red light after imbibition inhibited germination. Germination after a brief exposure to red light, as either a single or a terminal exposure, was higher than that after a brief far-red light irradiation, but lower than dark germination. After the hydrated seeds were irradiated for a prolonged period with far-red light and dried for 7 days, they germinated poorly and failed to respond to brief red light irradiation after rehydration. Forty days after drying, however, the far-red light pretreated seeds were induced to germinate and showed a typical phytochrome-mediated response. Prolonged far-red light irradiation inhibited the germination of halved, freshly harvested seeds only when the seeds were imbibed in polyethylene glycol solutions with considerable negative water potentials. The scutellum and radicle of a halved seed responded to the far-red light treatment differently, but correlatively. The unexpected inhibitory effects of brief red light irradiation on the freshly harvested seed are related to the specific physiological system in the seed. Key words: light, seed halves, water potential, phytochrome, Avena.
A study of within and among population genetic variability in Ornithogalum montanum (Liliaceae)
Authors: Pigliucci M. , Serafini M. , Bianchi G.
Published: April 2011

Ornithogalum montanum (Liliaceae) is a bulbous perennial known to be extremely variable both karyologically and morphologically. We have investigated the intra- and inter-population variability at the genetic level using starch gel electrophoresis. Within and among demes variation was addressed by a combination of cluster analysis and ordination techniques (correspondence analysis and discriminant analysis). The main conclusions are the following: (i) there is a wide range of internal variability in the 13 populations studied; (ii) there are at least three independent patterns of variation among allele frequencies; (iii) the variation patterns are only partially explainable by geographic localization; (iv) 2 of the 13 demes seem to have originated after a recent bottleneck. The overall genetic variation of O. montanum confirms recent taxonomic studies that recognize it as a single taxon at the species level. General considerations about the evolution of O. montanum are made on the basis of comparative studies on karyology and morphology of this species. Key words: Liliaceae, correspondence analysis, discriminant analysis, electrophoresis, genetic variation, cluster techniques.
The effect of experimental defoliation on the growth and reproduction of a woodland orchid, Tipularia discolor
Authors: Whigham Dennis F.
Published: April 2011

Leaves of individuals of Tipularia discolor were subjected to 3 years of manual defoliation to simulate natural patterns of herbivory. Compared with controls, plants that were 100% defoliated did not reproduce sexually after two defoliations, the biomass of new belowground corms decreased significantly in the 1st year and each year thereafter, and leaf biomass declined significantly after three defoliations. Senescence of belowground corms and mortality of entire plants were highest in the 100% defoliation treatment. The responses of plants with 50% defoliation were intermediate. The study demonstrates that belowground corms are the first biomass component to be negatively impacted by complete and partial defoliation. Reductions in corm biomass resulting from leaf herbivory would eventually reduce leaf biomass and sexual reproduction. Key words: woodland herb, herbivory, biomass allocation, reproduction, Tipularia discolor, Orchidaceae, defoliation.
Phenology of northern populations of halophytic C3 and C4 grasses
Authors: Schwarz A. G. , Redmann R. E.
Published: April 2011

Phenological analyses of halophytic grasses in Saskatchewan (52°N latitude) showed that regrowth began earlier in the C3 species, Agropyron trachycaulum (Link) Malte and Puccinellia nuttalliana (Schulte.) Hitchc. than in the C4 species, Spartina gracilis Trin. and Distichlis stricta (Torr.) Rydb. Maximum plant height was reached at about the same time in both C3 and C4 species. C3 grasses had the maximum number of green leaves per plant during spring and autumn, and C4 grasses had these during midsummer. Species on a strongly saline site (P. nuttalliana and D. stricta) began flowering earlier than those on a moderately saline site (A. trachycaulum and S. gracilis). Within each site, C3 and C4 species flowered almost simultaneously. The results indicate that at cool northern latitudes temporal niche separation in C3 and C4 grasses is most evident in vegetative characteristics. Key words: phenology, C3, C4, halophytes, temporal niche separation.
Seasonal colonization of winter wheat in South Coastal British Columbia by vesicular–arbuscular mycorrhizal fungi
Authors: Cade-Menun Barbara J. , Berch Shannon M. , Bomke A. A.
Published: April 2011

Seasonal colonization patterns of vesicular-arbuscular mycorrhizal fungi at four sites were monitored in the roots of winter wheat through the October to August growing season, as were a variety of environmental factors which might influence these patterns. Fall colonization was observed at the two sites which were the most highly colonized at all five harvests. The other two sites were not colonized until late spring and never attained high levels of colonization. Soil phosphorus, soil moisture, and plant physiology were shown to be most highly correlated with these patterns, while temperature was not believed to be an important factor. Key words: endomycorrhiza, Glomus, Sclerocystis, Acaulospora, Scutellospora.
Déterminisme de la reproduction sexuée de Phaeosphaeria (Leptosphaeria) nodorum, agent de la septoriose du blé. I. Hétérothallisme et rôle des microspores
Authors: Halama P. , Lacoste L.
Published: April 2011

Recently identified conditions for in vitro perithecia formation made it possible to demonstrate the existence of previously suggested heterothallism in Phaeosphaeria nodorum. Of the 28 possible pairwise crosses between the eight cultures derived from the spores of a single ascus, 9 were fertile, whereas none of the cultures ever produced fertile perithecia on their own. This result is smaller than the one obtained in classical bipolar heterothallism and suggests the existence of another incompatibility mechanism. The growth and the colour of mycelia derived from eight single ascospores from the same ascus seem to cosegregate with the factor for heterothallism. The formation of microspores in colonies from single ascospores indicates that they may play a role in the formation of perithecia. Used for fertilization, these microspores showed that they were able to bring the complementary nucleus, thus enabling the differentiation of perithecia. However, they are able to germinate and do not behave strictly as spermatia. Key words: Phaeosphaeria, Leptosphaeria nodorum, heterothallism, microspores.
Biotransformation of lycorine by Cryptococcus terreus to a stimulant of budding in Cryptococcus dimennae
Authors: Garuccio I. , Onofri S. , Evidente A. , Arrigoni O.
Published: April 2011

Lycorine stimulates budding in Cryptococcus terreus. In lycorine-treated cultures, there is an increase in dry weight and even more in the number of cells. Cryptococcus dimennae is not affected by lycorine. The filtered medium of lycorine-treated cultures of C. terreus stimulates the growth of C. dimennae. The possibility that C. terreus is able to degrade lycorine and that a degradation product is able to stimulate budding in C. terreus and C. dimennae is discussed. Scanning electron microscopy analysis shows that cells in lycorine-treated cultures of C. terreus are round and smaller than those of the control. Similar differences are found in C. dimennae cells cultured in the filtered medium of C. terreus, whereas they appear identical if directly cultured either with or without lycorine. Key words: lycorine, yeasts, Cryptococcus.
Transfer cells in the sporophyte–gametophyte junction of Lycopodium appressum
Authors: Peterson R. L. , Whittier D. P.
Published: April 2011

The sporophyte–gametophyte interface in cultured Lycopodium appressum gametophytes consists of a sporophytic foot embedded in gametophyte tissue. Foot cells and contiguous gametophytic cells develop extensive wall ingrowths, making them transfer cells. Transfer cells in the foot of young sporophytes and in adjacent gametophyte cells have elongated, narrow wall ingrowths forming a labrynthine wall–membrane apparatus, numerous mitochondria, and plastids with variable amounts of starch. Transfer cells in older interfaces have thickened wall ingrowths, few mitochondria, plastids with numerous plastoglobuli and little starch, and a large central vacuole. Plasmodesmata do not develop between cells of sporophyte and gametophyte generations and these are, therefore, isolated symplastically during all stages of sporophyte development. Key words: Lycopodium, foot, haustorium, transfer cells, ultrastructure.
Sclerotial morphogenesis in Sclerotium cepivorum in vitro
Authors: Littley E. R. , Rahe J. E.
Published: April 2011

Sclerotial ontogeny, maturation, and aging in Sclerotium cepivorum are described using light and scanning electron microscopy. On potato dextrose agar, the mycelium spread, branching irregularly. Six days after inoculation sclerotial initials appeared, formed by hyphae branching and looping. From 6 to 8 days, the number and size of initials increased, and mucilagenous material appeared. By day 9, hyphal bundles formed in the mycelium. Between 9 and 11 days, spherical forms developed and the sclerotia grew. By day 12, an acellular matrix appeared, and to day 18 this matrix progressively obscured the surface hyphae and became black. A layer of ovoid rind cells developed at the surface. To examine the reduced survival of laboratory-produced compared with field-collected sclerotia, sclerotia from a variety of sources and conditions were compared. In general, the rind of sclerotia aged in dry conditions had a broken, irregular appearance versus fresh sclerotia or sclerotia aged under moist, axenic conditions. Sclerotia aged dry developed 1 to 4 layers of rind cells, while sclerotia kept moist developed only 1 or 2 layers. The structural and survival differences between laboratory-produced and natural sclerotia are attributable to differences in the moisture conditions under which they matured and aged. Key words: Sclerotium cepivorum, white rot, morphogenesis, sclerotia.
Mycoflora of strawberry in Ontario
Authors: McLean M. A. , Sutton J. C.
Published: April 2011

Mycelial fungi associated with leaves, flowers, and fruits of strawberry (Fragaria × ananassa Duchesne) were monitored in a field plot from August 1986 to July 1987. The principal fungi found on leaves of various developmental stages were Alternaria alternata, Botrytis cinerea, Cladosporium spp., Colletotrichum dematium, Coniella fragariae, Epicoccum purpurascens, Gliocladium roseum, Gloeosporium sp., Gnomonia comari, Penicillium spp., Trichothecium roseum, and Verticillium spp. A majority of the fungi were observed more frequently on leaves that were washed and then plated on agar media than on leaves that were plated without washing. Trichothecium roseum, however, was found mainly on the unwashed leaves. Principal fungi on calyces, petals, and fruits were A. alternata, B. cinerea, Gloeosporium sp., Pencillium spp., T. roseum, and Verticillium spp. Other fungi variously found on the flowers and fruits included Rhizopus stolonifer, Paecilomyces spp., C. dematium, and Fusarium spp. Many of the fungi found frequently on the strawberry plants were present at most or all stages of development and decline of the various plant organs. The mycofloral observations are discussed in relation to the biocontrol of strawberry diseases. Key words: strawberry, mycoflora, Botrytis cinerea, population dynamics.
A β-1,3-D-endo-mannanase from culture filtrates of the hyperparasites Verticillium lecanii and Aphanocladium album that specifically lyses the germ pore plug from uredospores of Puccinia graminis f.sp. tritici
Authors: Langen Gregor , Beibmann Bernd , Reisener Hans J. , Kogel Kalle
Published: April 2011

The hyperparasites Verticillium lecanii (Zimm.) Viegas syn. Verticillium hemileiae and Aphanocladium album (PreuB) W. Gams are capable of penetrating the hyphal walls and uredospores of the stem rust fungus Puccinia graminis f.sp. tritici, their potential host. The culture filtrates of both hyperparasites contain an array of polysaccharide-degrading enzymes that in concert, digest the walls of uredospores completely. We have now isolated an enzyme with β-1,3-D-endo-mannanase activity that is secreted by both hyperparasites into the culture medium in the presence of autoclaved walls of uredospores as a carbon source. The β-mannanase predominately lyses the germ pore plugs of uredospores as shown by electron scanning microscopy. The enzyme has an apparent molecular mass of 19 000 Da as revealed by medium pressure liquid chromatography using a Superose 12 gel filtration column. An enzyme with identical specificity was found in dormant and soaked uredospores. Since opening of the germ pore plug is a very early and crucial step in germination of uredospores, the implication of β-mannanases in the germination process is discussed. Key words: Aphanocladium album, germination, β-mannanase, hyperparasitism, Puccinia graminis, Verticillium lecanii.
Late Quaternary history of black spruce and grasslands in southwest Yukon Territory
Authors: Keenan T. J. , Cwynar L. C.
Published: April 2011

Pollen records from Long Last Lake and Two Horsemen Pond, near the centre of the arid region of southwest Yukon Territory, do not support the hypotheses that (i) black spruce was a dominant species in the region and (ii) the southwest Yukon supported widespread grasslands during most of the past 10 000 years. Black spruce became established between 8500 and 8000 BP, shortly after the arrival of white spruce, but its low pollen percentages (< 5%) indicate that it was a minor component of forests. Between 6000 and 5000 BP, white spruce populations decreased as black spruce and green alder increased, but black spruce remained a minor constituent of the forest, never becoming a dominant species as at Kettlehole Pond near the southeast margin of the arid southwest Yukon. The initial vegetation was a poplar woodland, dating from 9200 to 8500 BP at Long Last Lake. At both Long Last Lake and Two Horsemen Pond, the high percentages of herb pollen indicate that the forest was open, but the low values of grass pollen suggest that grasslands were not extensive. Coincident with the establishment of spruce woodland at 8500 BP, pollen of herbs declines and remains comparatively low until 1300 BP when herbs, including grasses, increase to maximum values for the period of record, indicating the grassland communities were probably never more abundant during the Holocene than they are now. Key words: southwest Yukon, black spruce, pollen analysis, paleoecology, climate change.
Orthodistichous phyllotaxy and dorsiventral symmetry on adult shoots of Cyclanthus bipartitus (Cyclanthaceae, Monocotyledoneae)
Authors: Wilder George J.
Published: April 2011

An adult shoot of Cyclanthus bipartitus may simultaneously exhibit orthodistichy and dorsiventral symmetry, i.e., adult features previously unreported for Cyclanthus. As in previously investigated adult shoots of C. bipartitus with spirodistichous phyllotaxy, specimens presently described have sympodial rhizomes that form renewal shoots and terminal inflorescences. The phyllotaxy, symmetry, and sympodial structure of these specimens, collectively, represent a new type of growth habit in the Cyclanthaceae. On a shoot with orthodistichy the basal portions of mature leaves define a concave surface, convex surface, sagittal plane, and frontal plane. Plants grow upright on forest-covered slopes, and the concave surface and convex surface of a shoot are slope-opposed and slope-facing, respectively. Most emergent adventitious roots arise from the convex surface. Aspects of the form, symmetry, development, and orientation of a shoot are interpretable as adaptations to unequal illumination on its slope-facing versus slope-opposed sides. Presence of conspicuous dorsiventral symmetry is correlated with poorly expressed mirror-image symmetry, and shoots are neither left-handed nor right-handed, contrary to the condition in various Cyclanthaceae. Present findings bolster the conclusion that C. bipartitus is an extremely variable species. Key words: Cyclanthaceae, Cyclanthus, morphology, symmetry, phyllotaxy.
The influence of pH on the toxicity of a low concentration of aluminum to white spruce seedlings
Authors: Nosko Peter , Kershaw Kenneth A.
Published: April 2011

Week-old white spruce seedlings were grown for 7 days at pH 4.5, 3.9, 3.65, or 3.5 using a continuous flow system to deliver experimental solutions. At each pH, seedlings received either no aluminum or 10 μM Al, a concentration 2 – 3 orders of magnitude lower than the reported minimum Al concentrations required to induce toxicity symptoms in seedlings of a variety of tree species. In – Al treatments, root elongation was reduced at pH 3.9 and root dry weight was reduced at pH 3.5, compared with seedlings grown at pH 4.5. Exposure to 10 μM Al caused further reduction of root growth, the magnitude of which increased as pH decreased. This suggests that seedling root growth was affected by the increased proportion of the total Al existing as phytotoxic Al3+ at lower pH values or by an interaction of Al3+ and H+. Neither pH nor Al affected shoot growth. Both acidity and Al could limit natural regeneration of white spruce by preventing seedling establishment. Key words: aluminum toxicity, soil acidity, forest decline, white spruce, Picea glauca, forest regeneration.
Comparative shoot regeneration in diploid and amphidiploid Brassica species and their interspecific hybrids
Authors: Narasimhulu S. B. , Prakash Shyam , Chopra V. L. , Arunachalam V.
Published: April 2011

Shoot regeneration response in interspecific hybrids of Brassica species were assessed in relation to the diploid pollen parents and amphidiploid female parents. Superior regeneration responses were observed in interspecific combinations of B. carinata and B. nigra (BBC), B. juncea and B. campestris (AAB), and B. napus and B. campestris (AAC). Though synthetic B. napus regenerated with a frequency less than that of the better regenerating parent (B. oleracea), higher regeneration response was observed in the hybrid between B. napus and B. campestris. Two triploid combinations of the genetic constitution ABC, one obtained by crossing synthetic B. napus with B. nigra and the other by crossing natural B. juncea with B. oleracea, showed low regeneration responses. The response improved substantially in a tetraploid of the constitution ABBC obtained by crossing B. juncea with B. carinata. Key words: Brassica, alloploids, shoot regeneration.
Application of chemotaxonomy of leafy spurges (Euphorbia spp.) in biological control
Authors: Holden Antony N. G. , Mahlberg Paul G.
Published: April 2011

Triterpenoid profiles from latex of 56 accessions of European leafy spurges (Euphorbia spp.) were analyzed by gas–liquid chromatography. Qualitative and quantitative differences for components of the profiles were employed to distinguish between accessions. Triterpenoid profiles were diagnostic for the species, E. amygdaloides, E. agraria, E. cyparissias, E. lucida, and E. seguierana and were similar for each of these species in accessions collected from distant areas of Europe. By contrast, the 37 accessions of the E. esula complex were separated into 15 groups on qualitative and quantitative differences for components in the profiles. Identical profiles were detected among neighbouring accessions as well as those in collections from widely distant sites; conversely, different profiles also were identified for such collections. Profiles among these groups were compared with profiles of 39 United States (US) accessions of leafy spurge from Montana, Nebraska, North Dakota, and South Dakota. Profiles of US accessions, which were less variable than those from Europe, grouped into only 3 of the 15 European groups, whereas one US group could not be placed directly into a European group. This study demonstrates that latex analyses of European leafy spurges can distinguish between spurge populations and will identify potential plant sources of biocontrol agents for application against their leafy spurge counterparts in North America. Key words: leafy spurge, Euphorbia, latex, triterpenoids, gas–liquid chromatography.
Mise en évidence, par la fluorescence de la chlorophylle, de la variabilité génotypique de la réponse à une contrainte hydrique chez le trèfle blanc (Trifolium repens) et l'ivraie vivace (Lolium perenne)
Authors: Ourcival J. M. , Méthy M. , Burgess R.
Published: April 2011

The genotypic variability of six interspecific neighbouring pairs of white clover (Trifolium repens L.) and perennial rye grass (Lolium perenne L.) has been examined in relation to chlorophyll fluorescence and leaf water content. Fluorescence was measured using wavelengths of 690 and 730 nm. The following indices of fluorescence were used: the fluorescence-decrease ratio at the two wavelengths (vitality index), their combination (adaptation index), and the ratio of the fluorescence intensities at 690 and 730 nm. The effect of the type of drought stress applied on leaf cutting and pot planted material was examined. The results show that the first two indices of fluorescence are precocious indicators of drought stress and that they allow to distinguish genetically close individuals. Fluorescence thus provides a mean of ranking genotypes of two species. Key words: fluorescence, vitality index, adaptation index, fluorescence ratio, relative water content.
Étude de quelques aspects du métabolisme carboné et azoté chez l'Arceuthobium oxycedri, gui nain du genévrier
Authors: Rey L. , Sadik A. , Fer A. , Renaudin S.
Published: April 2011

In juniper dwarf mistletoe, Arceuthobium oxycedri (DC) M. Bieb., a hemiparasitic and epiphytic Angiosperm characterized by very reduced and slow development, the chlorophyll content of the shoots is relatively high for a parasitic plant. However, gas exchanges reveal a low net gain in carbon, and the real photosynthetic intensity is only about 1.5 to 2 times higher than the respiratory intensity in these organs. In the endophytic system, which is also chlorophyllous, a small amount of photosynthetic activity also occurs. By studying 14CO2 assimilation and carboxylase activities in both organs, it was possible to determine the ability of the parasite to satisfy part of its carbon requirements. Following the administration of 14CO2, radioactivity was mainly recovered in carbohydrates and to a lesser extent in organic acids and amino acids. This demonstrates that A. oxycedri has some autonomy for the fixation and distribution of carbon into various compounds. On the other hand, the parasite, since it is epiphytic, is completely dependent upon its host for nitrogen. The study of the activities of the key enzymes of nitrogen metabolism ([Formula: see text] and [Formula: see text] reductases, glutamine synthetase, glutamate dehydrogenase, glutamate-oxalacetate transaminase) shows that nitrogen supply from the host certainly occurs mainly in the form of reduced nitrogenous compounds (ammonia and (or) aminated organic compounds). The numerous labelled amino acids recovered after administration of 14CO2 show that A. oxycedri is able to redistribute the imported nitrogen in various ways. Key words: Arceuthobium oxycedri, parasitic Angiosperms, carbon nutrition, nitrogen nutrition.
A quantitative model of leaflet initiation illustrated by Murraya paniculata (Rutaceae)
Authors: Jeune Bernard , Lacroix Christian R.
Published: April 2011

A modified mathematical model based on the concept of generative centers is proposed to describe organogenesis in young leaf primordia of Murraya paniculata. Measurements of specific parameters on leaf primordia at different stages of development support the basic assumptions of the model. These assumptions are exponential elongation and widening of primordia in the organogenetic phase and rhythmic production of lateral elements at a fixed distance from the apex of the developing primordium. In general, the model provides good estimates for growth parameters such as elemental growth rates. It also provides a relatively accurate description of the shape of the primordium during the organogenesis of lateral elements or leaflet primordia. Key words: leaf development, mathematical model, organogenesis, compound leaf, Murraya paniculata.
Genetic and macromorphologic evidence bearing on the evolution of members of Carex section Vesicariae (Cyperaceae) and their natural hybrids
Authors: Ford Bruce A. , Ball Peter W. , Ritland Kermit
Published: April 2011

A comparison of genetic distances between the short-beaked species (C. saxatilis, C. membranacea, and C. rotundata) and some long-beaked species (C. utriculata, C. rostrata, and C. vesicaria) of Carex section Vesicariae indicates that the short-beaked group is not monophyletic. Carex saxatilis is closely related to C. vesicaria, while C. membranacea and C. rotundata are related to C. utriculata. It is proposed that C. saxatilis is derived from a vesicaria-like ancestor, while C. membranacea and C. rotundata have evolved from a utriculata-like progenitor. Taxa identified as hybrids between various short- and long-beaked species are intermediate in morphology, heterozygous for diagnostic loci (which exhibited a high frequency of alternative alleles in the putative parents), and often sterile. On the basis of the evidence presented the following hybrids are recognized: C. × paludivagans (C. rotundata × utriculata); C. × stenolepis (incl. C. × grahamii, C. × mainensis, C. × anticostensis; C. saxatilis × vesicaria); C. × physocarpoides (C. saxatilis × utriculata); and C. membranacea × utriculata. Key words: Carex, evolution, hybridization, systematics, morphology, isozymes.
Allelopathic effects by Empetrum hermaphroditum on development and nitrogen uptake by roots and mycorrhizae of Pinus silvestris
Authors: Nilsson Marie-Charlotte , Högberg Peter , Zackrisson Olle , Fengyou Wang
Published: April 2011

Fennoscandian plant communities dominated by the evergreen dwarf shrub Empetrum hermaphroditum Hagerup appear to have negative effects on forest regeneration. Effects of water extracts of leaves of E. hermaphroditum on the development and nitrogen uptake by roots and mycorrhizae (Paxillus involutus Batsch (Fr.)) of Scots pine (Pinus silvestris L.) were studied in a greenhouse experiment. Among seedlings that did not receive E. hermaphroditum extract, mycorrhizal plants grew better than nonmycorrhizal plants and also had a higher shoot to root ratio. Nitrogen uptake per unit root length was 3 times faster in mycorrhizal plants. The uptake of nitrogen was 92 ng∙day−1 per dichotomous tip as compared with 22 ng∙day−1 per nondichotomous root tip (mycorrhizal plants had both dichotomous and nondichotomous tips, whereas uninoculated plants almost exclusively had nondichotomous tips). A low concentration of extract impaired nitrogen uptake in both mycorrhizal and nonmycorrhizal plants. Uptake per unit root length was reduced to one-third and one-tenth in mycorrhizal and nonmycorrhizal plants, respectively. Calculated per dichotomous tip per day, the uptake of nitrogen was reduced to only 0.9 ng. Additions of extract also retarded increases in root length and the numbers of root tips, although less markedly, but the percentage of dichotomous tips was more strongly reduced. Empetrum hermaphroditum extract also strongly inhibited the growth of Paxillus involutus on modified Melin – Norkrans agar medium. The spread of mycorrhizal infection (as indicated by the percentage of dichotomous tips) and uptake of nutrients by roots and mycorrhizae were more sensitive to the extract than seed germination and radicle growth, which were demonstrated to be affected under field conditions. Key words: allelopathy, Empetrum hermaphroditum, forestry, mycorrhiza, nitrogen.
Germination of Orobanche crenata seeds, as influenced by conditioning temperature and period
Authors: Hezewijk M. J. van , Beem A. P. van , Verkleij J. A. C. , Pieterse A.H.
Published: April 2011

The effects of conditioning temperature and length of the conditioning period on germination of seeds of the parasitic weed Orobanche crenata were investigated in vitro. Seed samples from Syria and Egypt, collected in various years, were compared. Optimum temperature for conditioning was 15–20 °C for Syrian seeds and 20 or 15–20 °C for Egyptian seeds. At 20 °C a conditioning period of 18 days was required for maximum germination. When conditioning at 20 °C was prolonged beyond 7 weeks, germination decreased. This effect was more pronounced for Egyptian seeds than for Syrian seeds. Germination of Syrian seeds was strongly reduced after conditioning for more than 4 weeks at 15 or 10 °C. A stepwise decrease in temperature during conditioning did not enhance this effect. The results of a tetrazolium test indicated that the seeds most probably did not die but developed secondary dormancy. Key words: Orobanche, germination, conditioning, temperature, dormancy.
Phenotypic variation of Chinese aspens and their relationships to similar taxa in Europe and North America
Authors: Barnes Burton V. , Han Fuqing
Published: April 2011

Morphological variation of leaves and pubescence of buds and shoots from Chinese aspen taxa (sect. Populus of Populus) were studied and compared with those of North American aspens. Data were analyzed for 648 clones from 19 Provinces of Chinese aspen taxa identified on herbarium specimens as P. bonatii Gomb., P. davidiana Dode, P. rotundifolia Griff. var. bonatii Gomb., P. rotundifolia Griff. var. duclouxiana (Dode) Gomb., and P. tremula L. In addition, data from field collections of intact shoots of 137 clones of P. davidiana (Heilongjiang, Jilin, and Shaanxi Provinces) and from 821 clones of P. tremula from Europe were also analyzed. Leaf morphology of herbarium specimens identified as P. davidiana, the most widely distributed Chinese taxon, varied markedly among populations, especially between northern and southwestern China. Clones of P. davidiana from northern and northwestern China were markedly different from those of the P. rotundifolia complex of southwestern China. However, clones identified as P. davidiana from southwestern China were similar to those of P. rotundifolia in leaf shape, number of teeth, and pubescence; they differed only in leaf size. Striking within- and among-population differences were found for field collections of P. davidiana in northeast China. Buds and seasonally determinate shoots of P. davidiana were glabrous in northeast and north-central China; pubescence increased markedly to the southwest. Buds and shoots of clones of the P. rotundifolia complex and P. tremula were predominantly pubescent. The Eurasian aspen taxa are enormously polymorphic in leaf morphology and pubescence; clinal variation along geographic gradients in China, Japan, and Europe are pronounced. Based on studies to date, we would tend to recognize P. davidiana and P. rotundifolia as races of P. tremula. It may be that in all of Eurasia there is but a single, highly polymorphic species, viz. P. tremula. Key words: aspens, China, Eurasia, Populus, morphology, systematics.
Morphologie et architecture des hêtres tortillards à Verzy (Fagus sylvatica var. tortuosa)
Authors: Thiébaut B. , Bujon P. , Haddad S. , Comps B. , Mercier J.
Published: April 2011

Growth is analysed both in ordinary and twisted beeches located in Verzy near Reims, France. Most variables of annual and multiannual growth are the same in the two types of trees. Stems in the twisted tree are markedly sinuous from the moment they begin to develop and remain so, whereas in the ordinary tree the sinuosities are attenuated and then the stems are straightened, right from the first years of development. In the ordinary tree, the straightening of the stems is regulated at the level of the ramified branches and the crown; this regulation establishes a strict hierarchy among the stems according to the order of the stems in the ramification. However, in the twisted beech, this regulation is absent and consequently sinuous stems are not straightened, lateral stems stand up, and reiterations start. Therefore, the frame of the ordinary tree is simple and only composed of one morphogenetic sequence before metamorphosis whereas frame development in the twisted tree consists of several sequences. Key words: morphology, architecture, Verzy, twisted beech, Fagus sylvatica var. tortuosa.
A new monotypic fungal genus, Allantomyces, and a new species of Legeriomyces (Trichomycetes, Harpellales) in the hindgut of a Western Australian mayfly nymph (Tasmanocoenis sp.)
Authors: Williams Marvin C. , Lichtwardt Robert W.
Published: April 2011

Allantomyces caenidarum sp.nov., a trichomycete fungus that lives in the hindgut of Tasmanocoenis sp. (Caenidae) mayfly nymphs in southwestern Western Australian streams, is described. In addition to normal trichospores and zygospores that serve to reinfest other nymphs, A. caenidarum also produces what may be modified trichospores that serve to increase gut infestation endogenously. The same species of mayfly also harbored a new species, Legeriomyces raus, which belongs to a genus previously known only from North America and Europe. Key words: Caenidae, Allantomyces, Australia, Tasmanocoenis, Trichomycetes, Legeriomyces.
Differentiation of aecidiospore- and uredospore-derived infection structures on cowpea leaves and on artificial surfaces by Uromyces vignae
Authors: Stark-Urnau M. , Mendgen K.
Published: April 2011

Aecidiospores and uredospores are the two dikaryotic spore forms of the cowpea rust fungus Uromyces vignae. After germination they can be induced to develop a series of infection structures including appressoria, infection hyphae, and haustorial mother cells. Haustoria are then formed within host cells. The differentiation of infection structures was compared on polystyrene membranes with defined topographies, on scratched polyethylene membranes, and in planta. On polystyrene membranes with defined topographies both sporelings showed highest rates of differentiation on ridges 0.3 μm high but aecidiosporelings responded less efficiently to this stimulus than uredosporelings. On scratched polyethylene membranes, almost 90% of both sporelings differentiated appressoria, but only 10% formed haustorial mother cells; haustoria were not observed. On the host plant, by contrast, only 50% of the sporelings differentiated appressoria, but most of these formed haustorial mother cells and haustoria. In planta haustorial mother cell development occurred approximately 6 h earlier than on inductive membranes. Infection structures formed on artificial membranes and on host plants were similar in morphology and nuclear condition. Key words: cowpea rust fungus, nucleus, appressorium.
Effects of inversion on plastid position and gravitropism in Ceratodon protonemata
Authors: Schwuchow Jochen , Sack Fred D.
Published: April 2011

When dark-grown tip cells of protonemata of the moss Ceratodon purpureus are turned to the horizontal, plastids first sediment towards gravity in a specific zone and then the cell tip curves upward. To determine whether gravitropism and plastid sedimentation occur in other orientations, protonemata were reoriented to angles other than 90°. Qualitative and quantitative light microscopic observations show that plastid sedimentation along the cell axis occurs in both upright and inverted cells. However, only some plastids fall and sedimentation is incomplete; plastids remain distributed throughout the length of the cell, and those plastids that sediment do not fall all the way to the bottom of the cell. Tip cells are gravitropic regardless of stimulation angle, and as in higher plants, the maximal rate of initial curvature is in response to a 120° reorientation. Infrared videomicroscopy, time-lapse studies of living, inverted protonemata indicate that amyloplast sedimentation precedes upward curvature. Together, these data further support (i) the hypothesis that amyloplast sedimentation functions in gravitropic sensing in these cells, and (ii) the idea that gravity affected the evolution of cell organization. Key words: gravitropism, inversion, plastid sedimentation, protonema, moss.
Development of vesicular–arbuscular mycorrhizae in sugar maple (Acer saccharum) and effects of base-cation ammendment on vesicle and arbuscule formation
Authors: Cooke Margaret A. , Widden Paul , O'Halloran Ivan
Published: April 2011

The development, condition, and incidence of vesicular–arbuscular mycorrhizae of Acer saccharum (sugar maple) seedlings grown in the greenhouse in natural sugar maple forest soil substrate were examined. The effects of the addition of a cation mixture containing calcium, magnesium, and potassium were also studied. The mycorrhizal structures observed were similar to those found in natural field conditions. Mycorrhizae developed intracellularly via hyphal coils, and arbuscules usually developed from these coils, forming arbusculate coils. This development is different from that observed in most annual crop plants. Vesicular–arbuscular mycorrhizal structures appeared within 30 days. The rate of mycorrhizal infection decreased, along with plant health, as the quantity of the added cations was increased, but the amendment did not affect the morphology of the infection. More vesicles were observed in the lowest level of application than in controls, suggesting a stress response and possible relationship between plant health and condition of the mycorrhizal association. Key words: Acer saccharum, development, vesicular–arbuscular mycorrhizae.
Effect of cropping history on the population structure of Typhula incarnata and Typhula ishikariensis
Authors: Matsumoto Naoyuki , Tajimi Akitoshi
Published: April 2011

Population structure of Typhula incarnata and Typhula ishikariensis, snow mold fungi, was determined by vegetative incompatibility on agar plates using isolates from 10 sites that differed in the extent of disturbance. Typhula incarnata populations were always diverse, with many different vegetative compatibility groups regardless of habitat differences, whereas diversity of T. ishikariensis populations differed according to habitat. Typhula ishikariensis populations in uncultivated lands were diverse; however, those from agricultural fields planted with perennial grasses became simpler with increasing number of years after the establishment of the host plant community. As a population, isolates from a new habitat were fast growers, less aggressive, and less competitive, and their sclerotia tended to germinate more rapidly than those from an old habitat. Where host plants were annual and the habitat was disturbed annually by tillage, population structure of T. ishikariensis was very simple. These results are discussed in terms of epidemiological differences between the pathogens and the effect of cultivation on population structure change. Key words: Typhula incarnata, Typhula ishikariensis, population structure, disturbance, snow mold fungi.
An analysis of growth, growth increments, and the integration of growth increments in a fertilizer test of Picea engelmannii in south-central British Columbia
Authors: Maze Jack , Vyse Alan
Published: April 2011

This study describes a 3-year study of growth in seedlings of Picea engelmannii planted in south-central British Columbia in 1986. Four different seedlots were used and each was subjected to six different levels of fertilization in the nursery and two on planting in the field; they were planted in three blocks. The seedlots planted as well as the interaction between blocks and the seedlots planted had a significant effect on seedling survival. The seedlot that showed the lowest rate of survival was the one displaced upward approximately 1180 m from its origin. The largest seedlings on planting, and in 1989, were from the same seedlot that showed the lowest rate of survival. Despite having the largest seedlings, that seedlot did not have the highest rate of growth. The greatest amount of variation in size, growth rate, and increments of growth is within each combination of treatments. Fertilization in the field was the experimental factor that had a consistent effect on growth and size, aside from size on planting where seedlot and nursery treatment were important. Field fertilizer treatments affected the integration of increments of growth in height and diameter. This treatment also affects energy flow through plants by its impact on growth rate, thus arguing for a correlation between the flows of energy and information. We are unsure if this correlation is causal or casual. Key words: growth rate, integration, Picea engelmannii trials.
Redifferentiation of moss protonemata: an experimental and immunofluorescence study of brood cell formation
Authors: Goode Jamie A. , Stead Anthony D. , Duckett Jeffrey G.
Published: April 2011

The formation of ovoid or spherical brood cells from chloronemal filaments by swelling and symmetrical subapical divisions preceded by phragmosomes, but not preprophase bands, is described in the mosses Physcomitrella patens, Dicranoweisia cirrata, Bryum tenuisetum, Bryum bicolor, and Rhytidiadelphus loreus. This is a widespread phenomenon that occurs in protonemal colonies cultured for long periods of time or allowed to dry out. It involves the redifferentiation of highly polarized chloronemal cells with a net axial array of microtubules into nonpolar cells containing microtubules with no preferred orientation. Brood cells in some species become thick walled and retain their viability for long periods even in a desiccated state. When transferred to new medium they immediately regenerate protonemata from new filaments of no fixed position. Experiments using activated charcoal, which prevents brood cell formation, and transferring protonemata or spores onto old medium in which brood cells had been produced previously, indicate that the redifferentiation process is triggered by substances released into the medium by protonemata. Addition of abscisic acid, an endogenous growth regulator in mosses, causes precocious brood cell formation in young cultures and is very likely the natural compound triggering their development and inducing their tolerance to desiccation. Key words: abscisic acid, activated charcoal, redifferentiation, desiccation tolerance, microtubules, polarity, protonema, regeneration.
Interhabitat variation in growth characteristics of temperate herbaceous perennials
Authors: Yoshie Fumio
Published: April 2011

Growth characteristics were investigated in 40 temperate herbaceous perennial species in relation to habitat. Some forest plants completed leaf development and shoot elongation before and during canopy closure. This rapid foliation involved expansion of only a small number of foliage leaves, disappearance of scale leaves, and a reduced shoot height. These species showed a determinate growth habit and early initiation of flowering. These are characteristics considered to have evolved in association with shade stress. In contrast, plants mainly found in exposed sites with a tall-herb vegetation continued leaf development and shoot elongation even in mid-August. These species possessed a determinate growth habit, not investing photosynthates into sexual organs at least during early vegetative growth, and showed late initiation of flowering. These characteristics appear to be related to competition for light. Plants in exposed sites without tall herbs also continued leaf development in mid-August, but they had rosette forms coupled with indeterminate growth habit and varying time of flowering initiation. These traits allow the plants to make maximum use of the growing season and are advantageous to vegetative regeneration after disturbance. On the basis of the leaf-development duration in this study and dormant states obtained in a previous study, three growth-rhythm categories can be recognized in relation to habitat. Key words: growth form, growth habit, growth rhythm, leaf-development duration, flowering initiation, shade stress, disturbance, competition.
Distribution ofArmillaria ostoyaegenets in aPinus resinosa–Pinus banksianaforest
Authors: Rizzo David M. , Blanchette Robert A. , May Georgiana
Published: April 2011

Diploid isolates of Armillaria ostoyae were obtained from 278 trees (including stumps, Pinus banksiana seedlings, and hardwood regeneration) and 78 solitary basidiomes on three 50 × 25 m plots (two clearcut and one uncut) in a Pinus resinosa – P. banksiana stand in northern Minnesota. Based on pairings among 439 isolates, 16 somatic incompatibility groups of A. ostoyae were distinguished on the three plots. Analysis of nuclear and mitochondrial markers suggests that many of the A. ostoyae genets are closely related and were possibly established by sib-related basidiospores. Analysis of molecular markers of 95 isolates representing the 16 somatic incompatibility groups delineated 16 nuclear and 8 mitochondrial haplotypes. All isolates tested within a somatic incompatibility group were identical for nuclear and mitochondrial haplotypes; a single exception consisted of a somatic incompatibility group with three different nuclear genotypes. The combination of somatic incompatibility and molecular data indicates the presence of at least 18 genets on the site. Large (up to 140-m diameter), spatially continuous genets intermingled with small, recently established genets and older, fragmented genets. The approach identified genetic and ecological processes; these include breeding strategies and pathogenicity. Key words: Armillaria ostoyae, somatic incompatibility, population structure, mitochondria.