bluuebunny/crossref_metadata_2025 huggingface dataset:
Présence de Typhula mycophaga sp. nov. sur Lycoperdon en Colombie-Britannique
Authors: Berthier J. , Redhead S. A.
Published: April 2011

Typhula mycophaga sp. nov., occurring on senescent basidiocarps of Lycoperdon pyriforme Pers. in British Columbia, is placed in the subgenus Microtyphula Berthier because of the morphology and the structure of its basidiocarps and its nongelatinized sclerotia which have a normal epidermoid structure. This species is distinguished by its habit, nonamyloid spores, nonclamped hyphae, and papillate superficial hyphae on the stipe.
Influence d'une déshydratation et d'une congélation (−196 °C) sur les ultrastructures des plantules d'Allium cepa. Étude après imprégnation métallique
Authors: Colson Monique
Published: April 2011

Artificial dehydration of 3-day-old seedlings of Allium cepa produces physiological and ultrastructural changes. Osmium fixation caused various alterations in dictyosomes, the endoplasmic reticulum, and the nuclear envelope. Seedling dehydration was accompanied by a lowering of the reduction capacity of various cell components. This lower reduction capacity also affected the same organelles in seed tissues. When seedlings were dehydrated, their tissues returned to a resting state, and became cold resistant. When artificially dehydrated seedlings were treated with liquid nitrogen (−196 °C), cells only underwent slight changes. These alterations were reversible both after dehydration and after freezing to −195 °C. During rehydration, the changes in cell structures and their reactivity following the osmic fixation technique were observed. [Journal translation]
Resistant structures in the entomogenous hyphomycete, Nomuraea rileyi: an ultrastructural study
Authors: Pendland J. C.
Published: April 2011

Three types of resistant or resting structures were found to occur in the entomogenous hyphomycete Nomuraea rileyi when unfavorable conditions (e.g., low humidity) inhibited conidiogenesis. Intrahyphal hyphae, which are regenerative hyphae within deteriorating parent hyphae, were observed in both the disintegrating larval tissue of Anticarsia gemmatalis and the extracuticular fungal mat. Thick-walled hyphae and chlamydospores were found in the external mat, and lipid-filled, thin-walled hyphae were prevalent in the larval tissue. Chlamydospores formed as apical swellings of thick-walled hyphae. Resistant structures remained viable for at least 12 weeks. Upon rehydration, cells resumed metabolic activity and after several days, conidiophores and conidia were produced. Verification of the existence of such structures provides an explanation as to how the fungus survives in the field under adverse environmental conditions.
Structural changes in the developing fruit wall of Amelanchier alnifolia
Authors: Olson A. Randall , Steeves Taylor A.
Published: April 2011

The flower of Amelanchier alnifolia Nutt. (Maloideae) exhibits a polyandric androecium and a syncarpous, pentalocular, inferior ovary. Each of the five locules contains two ovules. The vascular system of the floral tube is composed of 10 major bundles in addition to numerous, secondary branches. Carpel vasculature consists of one dorsal and two ventral bundles with secondary traces in addition to an ovular trace from each ventral bundle. Although there is no core line, the approximate boundary between what has been interpreted as floral tube and carpel may be discerned. Numerous mitoses, substantial increases in cell diameters, and intercellular space formation contribute to the ultimate size and shape of the mature fruit. Fruits are mature approximately 38 days after petal drop. The mature fruit does not exhibit an extensive sclerenchymatous endocarp and, therefore, it differs from the more typical pomaceous fruits.
Distribution and variation in growth of Scirpus maritimus var. paludosus on the Canadian prairies
Authors: Lieffers V. J. , Shay Jennifer M.
Published: April 2011

Scirpus maritimus var. paludosus occurs in saline lakes in the prairie and parkland regions of Alberta, Saskatchewan, and Manitoba. Its distribution within wetlands is dependent upon the degree of salinity during germination and seedling establishment. In hypersaline wetlands, S. maritimus is found only on a narrow band on the upper slope of the basin; as these wetlands become dry, only the upper slope has mud flat salinities low enough to allow successful germination. In wetlands of the saline category, S. maritimus occurs over a broad area of the upper and middle slope, and in moderately saline wetlands it is usually outcompeted by freshwater species but may dominate the centre of the basin in low-water years. Canonical-correlation analysis of S. maritimus growth variables in 24 sites in Saskatchewan, Manitoba, and Alberta showed a large phenotypic growth response to different environmental conditions. On dry and highly saline sites, S. maritimus tubers developed short, and in most cases nonflowering, stems. In shallow water and reduced salinity, individual stems were larger and stem density and above-and below-ground biomass were at a maximum. In water greater than 40 cm deep and with low salinities, individual stems and inflorescences reached maximum size, but the much lower stem density resulted in reduced total biomass. Seed production was also influenced by the previous year's water levels. At those sites which were dry and then flooded the next year, more stems flowered and inflorescences were larger than at sites which had been flooded continuously the previous year.
Axenic cultures from basidiospores of Cronartium ribicola
Authors: Diner Alex M. , Mott Ralph L.
Published: April 2011

Axenic colonies of Cronartium ribicola were routinely established directly from basidiospores. The methods permit axenic spore collection from field-grown Ribes plants. The colonies grew to a maximum 5-mm diameter in 5–6 weeks, after which the size remained stable. The mononucleate hyphae remained virulent for at least 24 months without media change. Yeast extract, peptone, and bovine serum albumin supplements were required in the medium, but bovine serum albumin may be replaced by nucleic acids or a trace-element solution. Germinal hyphae, but not vegetative hyphae, exhibit both sensitivity to light and negative geotropism. These have noteworthy implications regarding the general pattern of tree infection within forest stands.
The application of Helotium to agarics. Part I. Nomenclature. Part II. Notes on selected species from Canada
Authors: Redhead S. A.
Published: April 2011

The typification of Helotium Tode 1790, is detailed. Tode's comments in the protologue indicated that Helotium hirsutum Tode was the more important species upon which the generic description was based. The earliest explicit (lecto) typification was proposed by Fries in 1825. Fries's selection of Helotium gibbum Alb. & Schw. supports, by proxy, the acceptance of the original Helotium hirsutum as type now that both combinations are recognized as synonyms of each other. Evidence is presented to demonstrate that an attempt by Donk in 1962 to lectotypify Helotium with Helotium glabrum Tode was made arbitrarily, without direct reference to the protologue. A single recent collection is designated as neotype for both H. hirsutum and H. gibbum. Hemimycena crispula (Quél.) Singer is considered to be conspecific hence making the genus Hemimycena sensu Singer a later synonym of Helotium. Shortly after the publication of the name Helotium by Tode, the generic name was applied to both ascomycetes and basidiomycetes by Gmelin in 1792. The formal division of the genus into two, based on rules in the current code of botanical nomenclature, did not occur until 1805 when De Lamarck and De Candolle completed the process started by Persoon in 1799. The type species of Helotium Pers. apud D.L. &D.C. H. aciculare (Bull.) Pers. apud D.L. &D.C. was selected by Fries in 1818. Thirty-two new combinations are proposed in Helotium Tode for species which were mainly Hemimycena previously. Three invalid species names are validated in Helotium and two new names are proposed to avoid the creation of later homonyms. In addition, Helotium cyphelloides sp. nov. on Carex and Helotium nebulophilum sp. nov. on moss are described. Helotium substellatum (Kühner) comb. nov. is reported for the first time from North America and Helotium albicolor (A. H. Smith) comb. nov. with Helotium hirsutum for the first time in Canada. All five occur in British Columbia. Mycena litoralis A. H. Smith is considered to be a synonym of Helotium pseudocrispulum (Kühner) comb. nov. which is recognized for the first time in North America.
An electron microscope study of Meria coniospora, an endozoic nematophagous Hyphomycete
Authors: Saikawa Masatoshi
Published: April 2011

Conidia of Meria coniospora Drechsler, an endozoic nematophagous fungus, were examined by electron microscopy at various stages of infection. The conidia are almost conical in shape and develop a knoblike structure at the apical end. Ultrathin sections show that the knob is always covered with a mucous layer, which is composed of a number of radiating fibrils. Attachment to the nematode's integument is by means of this fibrillose layer. The germ tube from the bud grows between the conidium and nematode and forms a tiny infection bladder in the integument.
Chemical characteristics of the foliage of some deciduous trees in southeastern Ontario
Authors: Ricklefs Robert E. , Matthew Kathryn K.
Published: April 2011

We collected foliage from 34 species of broad-leaved, deciduous trees in southern Ontario and determined an index of leaf toughness, weight per unit area, percent water, and percent of dry weight as available carbohydrate, crude fibre, hemicellulose, holocellulose, lignin, polyphenols, nitrogen, phosphorus, ash, potassium, calcium, and magnesium. We analyzed variation in these constituents within samples, among three sampling periods during one growing season, and among species.
Nostoc of Peltigera canina when lichenized and isolated
Authors: Bergman Birgitta , Hällbom Lars
Published: April 2011

The cyanobiont Nostoc sp. from the lichen Peltigera canina was compared at the ultrastructural level when in its free-living and lichenized stages, as were certain of its physiological characters. The main results may be summarized as follows. The isolated cyanobiont shows typical Nostoc characters and resembles N. sphaericum and N. punctiforme. When lichenized, the vegetative cells are enlarged from 2.5 to 4.5 μm in average diameter. The thylakoids increase in number. They are arranged in a reticular manner and spread throughout the cytoplasm. Phycobilisomes are found and the phycobiliproteins show chromatic adaptation. In the symbiosis the heterocyst frequency of Nostoc is considerably lower at the thallus margins than in more mature thalus parts and the nitrogenase activity correlates with the heterocyst frequency. For the first time, Nostoc akinetes are reported in a lichen.
Cylindrocladiella, a new genus to accommodate Cylindrocladium parvum and other small- spored species of Cylindrocladium
Authors: Boesewinkel H. J.
Published: April 2011

Cylindrocladiella, a new hyphomycete genus, is proposed for the small-spored species of Cylindrocladium. The small-spored species differ not only in the shape and smaller size of the conidia but especially in the type of branching of their conidiophores and the position and structure of the appendage with vesicle. Further differences are found in the cultural characteristics, chlamydospores, microsclerotia, and the teleomorphs. A new species, Cylindrocladiella infestans, is described.
Fine structure of sporangiole development in Choanephora cucurbitarum (Mucorales)
Authors: Higham Michael T. , Cole Kathleen M.
Published: April 2011

Spore development was studied in Choanephora cucurbitarum by using transmission and scanning electron microscopy. Sporangioles are produced by expansion of the ampulla wall. A two-layered spore wall is then constructed within the spine-covered sporangiole wall. The outer spore wall layer is longitudinally grooved and is devoid of spines or appendages. The inner wall layer is thinner and electron transparent. During wall production, dark-staining granular vesicles were observed in the spore cytoplasm. Their contents stained similarly to the material of the outer wall layer. Mature spores possessed a third, innermost wall layer. This was identified as a new wall layer, which was continuous with the germ-tube wall of germinated spores. Released spores were observed to be contained within the sporangiole during dispersal and germination.
Predicting depth to the water table based on species presence on an Oregon coast deflation plain
Authors: Newman K. W.
Published: April 2011

Vegetation on an Oregon coast deflation plain was related to changes in depth to the water table and time since the initiation of succession. A new method was evaluated for the prediction of water-table depth based on species presence or absence. It was found that for 96% of the quadrats, water-table depth was predicted to within 10 cm; for 73% of the quadrats it was predicted to within 5 cm. The method can be applied to other studies for predicting the value of environmental variables based on species presence.
Histopathology of cankers on Populus caused by Cytospora chrysosperma
Authors: Biggs A. R. , Davis D. D. , Merrill W.
Published: April 2011

Cuttings of poplar hybrid NE-388 (P. maximowiczii Henry × trichocarpa Torr. & Gray) were inoculated with mycelium of Cytospora chrysosperma (Pers.) Fr. Bark samples for histological study were taken at varying times after inoculation from slowly enlarging cankers, blackstem, control wounds, and uninoculated healthy plants. Histological examination revealed that slowly enlarging cankers are characterized by hyphae in the xylem and necrosis of the cambium ahead of visible bark symptoms, by large- and small-diameter hyphae both between and within host cells, and by hyphal aggregations associated with the leading edge of bark colonization. The blackstem symptom is characterized by rapid colonization of the cortex and phloem by large-diameter intercellular hyphae followed by the digestion of cell contents by small-diameter intracellular hyphae. Histochemical tests indicate degradation of pectic substances, loss of cellulose and starch, and deposition of wound gums. Lignification is not involved. Host response mechanisms associated with wounding and pathogen attack are similar. The underlying common denominators are the formation of a nonsuberized impervious tissue, followed by formation of necrophylactic periderm and redifferentiation of new phellogen and cambium.
Coprophilous fungal communities in semiarid to mesic grasslands
Authors: Angel Sr. Kathleen , Wlcklow D. T.
Published: April 2011

This investigation examined the composition of coprophilous fungal communities, with emphasis on the ascomycetous components thereof, on rabbit and cattle feces collected from short-grass (Nunn, CO), mixed-grass (Cottonwood, SD), and tall-grass (Shidler, OK) prairie ecosystems in the western United States. Fungal communities recorded for one dung type were always more similar to one another than to fungal communities from the other dung type, regardless of the grassland site from which samples were collected. The composition of the fungal community varied according to the age of the dung collected. Comparison of fungal communities on six age classes (0–54 months field exposure) of cattle dung from a semiarid grassland showed that communities were most similar on fecal collections nearest in age. The largest number of fungal species was recorded on fecal collections from the semiarid short-grass prairie. These results contrast sharply with species diversity patterns of other organism groups inhabiting these same grasslands. A hypothesis is presented that the greater species abundance of coprophilous fungal communities in semiarid grasslands is related to the slower rate of decomposition of individual fecal substrates and, thus, the availability of long-lived resource islands capable of supporting successive populations of fungal colonists. Communities on dung from the drier prairie sites (short grass and mixed grass) were more similar to one another than to communities from the more mesic tall-grass prairie. These results are contrasted with between-site comparisons of seed plants and small mammals. With one exception, decomposition dry weight losses during moist-chamber incubation for 80 days did not differ significantly (p > 0.05) among cattle dung samples regardless of the time dung was incubated in the field. Chemical analyses performed initially on field-aged cattle dung from the short-grass prairie site revealed similar percentages of various chemical components and this may account for the similarity of weight loss during moist-chamber incubation.
Interactive programs with graphics for leaf energy budgets
Authors: Kincaid Dwight T. , Miller Abigail M. , Schneider Robert B.
Published: April 2011

Interactive programs in BASIC for the leaf energy-budget equation are described. The programs are available on disc for the Apple II microcomputer and feature text output, screen graphics, multiple curves, exploration of curves by roving dots, entries for adaxial and abaxial cuticular and stomatal resistance, the Swinbank approximation, and Grashof–Reynolds numbers.
Notes on Tolypocladium and related genera
Authors: Bissett J.
Published: April 2011

The hyphomycete genus Tolypocladium W. Gams is compared with similar genera possessing swollen phialides and amerosporous conidia borne in slimy heads. Tolypocladium niveum (O. Rostrup) comb. nov. is proposed as the correct name for the type species. Cephalosporium balanoides Dreschler and Verticillium microsporum Jaap are redisposed in Tolypocladium, and two new species of Tolypocladium are described from tundra soils.
Le pneumatode chez Phoenix dactylifera L. I. Structure et ultrastructure
Authors: Belarbi-Halli Rosa , Dexheimer Jean , Mangenot François
Published: April 2011

Phoenix dactylifera roots possess air-containing structures or pneumatodes. Their mode of formation and their structure are described. They are derived from a generative layer. Their most remarkable features include the abundance of crystal-containing plasts and the occurrence of wall outgrowths which are associated with an amorphous matrix in intercellular spaces of young aerenchymous regions. The crystals show a positive response to labelling reactions of carbohydrates and proteins. [Journal translation]
Formation of sex organs in the A1 mating type of Phytophthora infestans induced chemically by A2 isolates of other species of Phytophthora
Authors: Shen Chong-Yao , Bower Leslie A. , Erwin Donald C. , Tsao Peter H.
Published: April 2011

Oogonia with attached antheridia, many of which contained mature thick-walled oospores, were formed in the A1 mating type of Phytophthora infestans after it had been paired with the A2 mating type of P. parasitica, P. palmivora, P. capsici, or P. infestans, on opposite sides of a polycarbonate membrane. The A2 culture discs, in both top and bottom positions in relation to the polycarbonate membrane, induced sex-organ formation in the A1 isolate of P. infestans. Sex organs were formed in P. infestans at 12, 15, 18, 21, and 24 °C, but they were most abundant at 15 and 18 °C and least at 24 °C. More sex organs in the P. infestans A1 isolate were induced by three A2 isolates of P. parasitica than by an A2 isolate of P. infestans. Evidence was presented that a diffusible oospore-inducing substance was produced by the A2 isolate of P. parasitica in the agar medium even when the A1 isolate of P. infestans was absent on the other side of the membrane. Because both P. infestans and P. parasitica are pathogenic to tomato and potato, such interspecific induction of the formation of selfed oospores in the A1 mating type of P. infestans could play an important role in survival and variation of P. infestans throughout the world.
Comparative water relations of container-grown and bare-root ectomycorrhizal and nonmycorrhizal Quercus velutina seedlings
Authors: Dixon R. K. , Pallardy S. G. , Garrett H. E. , Cox G. S. , Sander I. L.
Published: April 2011

A 2 × 2 factorial field experiment was conducted with black oak (Quercus velutina) to examine the effects of seedling production method (container-grown vs. bare-rooted) and inoculation with Pisolithus tinctorius on seedling water relations and soil–plant liquid flow resistance (Rs-P). Over the study period, bare-rooted and noninoculated seedlings exhibited midday values of leaf water potential (Ψ) which were lower than container-grown and Pisolithus-inoculated seedlings. During a mild drought in July similar trends were seen in predawn Ψ. Flow resistance between bulk soil and leaf was lower in container-grown and Pisolithus-inoculated plants than in bare-rooted and noninoculated plants; Rs–p was particularly high in bare-rooted plants which were not inoculated with Pisolithus. The exact mechanism(s) accounting for the differences in Rs–p of mycorrhizal vs. nonmycorrhizal plants could not be ascertained by the techniques employed. Low Rs–p in container-grown plants was associated with greater total root system length.
Habitat-dependent morphological and chemical variation in Picea mariana from northwestern Ontario
Authors: Parker William H. , Knowles P. , Bennett F. , Gray A. , Krickl T.
Published: April 2011

To determine whether local site differences corresponded to any morphological or chemical differentiation in Picea mariana, 10 cone-bearing trees were sampled from each of three semiadjacent stands near the Matawin River, Thunder Bay District, Ont.: (i) an upland forest on well-drained alluvial soil, (ii) an abandoned pasture on heavy soil, and (iii) a wet sphagnum bog. Nine cone characters and eight needle and twig characters were scored and analyzed. Differences among sites were generally small. Principal-components analysis demonstrated two major, independent trends of variation, one attributable mainly to cone characters and the other to needle characters. Bog trees tended to be more variable than the others with respect to cone characters but had similar levels of variation for needle and twig characters. Further comparisons were made based on foliar flavonoids of the 30 trees and isozyme characteristics of an expanded sampling of 60 trees. Flavonoid analysis indicated that a fraction of the bog trees possessed flavonoid diglycosides not present in the other trees. Five polymorphic enzyme systems were detected in electrophoretic analysis. Trees from the three sites had similar isozyme patterns with the exception of three bands that were unique to the bog site trees. Thus, the bog trees were more variable for cone, flavonoid, and isozyme characters but exhibited no greater variability for needle and twig characters. However, none of the data gave an indication of discrete ecotypes of black spruce corresponding to upland and lowland sites.
Morphogenetic potential of Fraxinus ornus under the influence of the gall mite Aceria fraxinivora
Authors: Anthony Ming , Sattler Rolf , Cooney-Sovetts Claire
Published: April 2011

Under the influence of the mite Aceria (Eriophyes) fraxinivora Nal., Fraxinus ornus L. produces galls which are transformed buds ("klunkerns") in the vegetative and reproductive region. In the vegetative region, to which this study is restricted, the following changes occur after infection by the mite: (i) modification and eventual inhibition of the growth of the main shoot apex; (ii) inhibition of internodal expansion; (iii) inhibition and deformation of leaf growth; (iv) increase in the diameter of the axis frequently coupled with fasciations; (v) development of supernumerary branches; and (vi) formation of a great number and variety of appendages on the leaves and stems including the shoot apex. This study focusses on the development of these appendages. Many of them develop like little leaves, others like determinate stems, or even rudimentary shoots, and still others like emergences. Intermediates between these types of appendages occur including intermediates between emergences and trichomes. The appendages may be simple or branched, nonvascularized or more or less vascularized, irregularly grouped or arranged in a more or less phyllotactic pattern, leaf or stem borne, and separate from each other or more or less continuous with each other. Much of the enormous variation is continuous. Ten continua are distinguished according to 10 different criteria. The galls are compared with galls of other taxa, which consist of a similar range of appendages, and with naturally occurring continua between morphological categories. It is concluded that under the influence of the mite Aceria fraxinivora, Fraxinus ornus expresses a morphogenetic potential to form a continuum between morphological categories which under normal circumstances is not manifested.
Ecological relationships of wild rice, Zizania aquatica. 2. Sediment – plant tissue nutrient relationships
Authors: Lee P. F. , Stewart J. M.
Published: April 2011

In this study the concentrations of elements in wild-rice tissue were related to the concentrations of elements in the sediment. In particular, the occurrence of similar concentrations and seasonal fluctuations of elements in wild-rice tissue was investigated. A model, based on the assumption of constant absorption per unit weight, illustrated how wild rice could have similar concentrations of elements in its tissue, even though the concentrations of the elements in the sediment varied both among and within stations. For a theoretical example with logistic growth characteristics, the model produced patterns which resembled the concentration fluctuations of elements found in wild-rice tissue. Utilizing actual leaf magnesium and wild-rice growth data, the model produced accurate representations of leaf magnesium concentrations but only after the emergent-leaf stage was reached. Seasonal fluctuations of concentrations of elements occurred in wild-rice tissue. Such fluctuations would negate any correlations with the concentrations of elements in the sediment. However, when these seasonal fluctuations were removed, those elements which differed in concentration in the tissue among the four sampling stations still had poor correlations with the corresponding elements in the sediment. Simple correlation with concentrations of elements in the sediment would therefore not account for the observed concentrations of elements in wild-rice tissue in this case.
Endomycorrhizal fungi occurring on orphan strip mines in Kentucky
Authors: Kiernan Jennifer M. , Hendrix James W. , Maronek Dale M.
Published: April 2011

Abandoned strip-mine sites in Kentucky which were mostly naturally revegetated were examined for the presence of endomycorrhizal fungi in the rhizospheres of established trees and other plants. Soil pH ranged from 3.2 to 7.1. Sixty-five percent of root samples examined were found to be mycorrhizal. Eight Glomus, three Gigaspora, and two Acaulospora species were positively identified. Plants sampled had one to eight different mycorrhizal species associated with them. The mean number of species per plant was 3.2. Spore numbers ranged from 0.4 to 53.0 spores per gram soil, with a mean value of 12.3 spores per gram. Strip-mine sites such as these may be a good source of ecologically adapted endomycorrhizal fungi for use in strip-mine reclamation.
Protein body inclusions in seeds of Eucalyptus maculata and Eucalyptus erythrocorys
Authors: White Michael J. , Lott John N. A.
Published: April 2011

Polarizing light microscope studies of sections of embryo tissues revealed the presence of birefringent druse crystals in certain protein bodies of Eucalyptus erythrocorys and E. maculata. Light and electron microscope studies show that the location, size, and structure of the protein bodies that contain druse crystals differ in these two species. These species also differ in the number of druse-containing protein bodies occurring per cell and the size and structure of the druse crystals. Energy-dispersive X-ray analysis, acid solubility, and microincineration tests showed that these druse crystals are composed of calcium oxalate. In both species the druse crystals were retained by the seedling during germination and early seedling growth. Seeds of both Eucalyptus species also contain globoid crystals in most, nonprotodermal protein bodies.
Morphometric relationships in Hordeum vulgare (Triticeae, Poaceae). II. Hordeum agriocrithon, H. distichum, H. lagunculiforme, H. spontaneum, and H. vulgare
Authors: Baum Bernard R.
Published: April 2011

Morphometric analyses of five morphs in Hordeum vulgare L. consisted of: computation of general statistics and frequency distributions by character for the entire data and for each morph separately; cross tabulation; various discriminant analyses; computation of Jardine and Sibson's (1968. Math. Biosci. 2: 465–482) information radius between the morphs followed by Bk clustering; and computation of phylogenetic trees from the transformed information radius matrix using three related methods. It is concluded that on the basis of morphometric data, excluding the traditional characters, that at least three morphs within H. vulgare (sensu lato) ought to be recognized as taxonomic entities. These are known as H. spontaneum C. Koch, H. distichum L., and H. vulgare (wild, two-row, and six-row barley, respectively). The hybrids and hybrid derivatives, often referred to as H. agriocrithon Åberg, are not regarded as entities but as products of interaction. The status of H. lagunculiforme Bakht. is uncertain and needs to be further investigated. It is postulated that a lagunculiforme-like entity might have been the progenitor of the group.
Plasticity in growth and patterns of dry matter distribution of two genotypes of Trifolium repens grown in different environments of neighbours
Authors: Turkington Roy
Published: April 2011

Replicates of two genotypes of Trifolium repens L., collected from a Poa pratensis dominated sward and a Dactylis glomerata dominated sward, respectively, were grown in swards composed of various proportions of P. pratensis and D. glomerata. These swards represented a range of environments of neighbours; an increasing proportion of P. pratensis was considered as an increasingly alien environment for individuals of T. repens collected from the D. glomerata dominated site, and vice-versa for the individuals from the P. pratensis dominated site. The individuals of T. repens were harvested on five occasions over a period of 27 months. Both genotypes responded to increasingly alien environments by producing more inflorescences and by distributing proportionately more dry matter to inflorescence production. Some evidence is also presented which suggests that allocation to stolons and inflorescences are alternatives and the balance of the trade off is dependent on the advantages of possibly producing new, better adapted offspring from seed, against the chances of a wandering stolon encountering a less hostile environment. Results are discussed in the context of environmental alienness, a major source of which is the different relative proportions of neighbours. The various genotypes of organisms which a relatively mobile plant species encounters are a major source of this environmental, or biotic, alienness.
Janetia mangiferae n.sp., and the Johncouchia n.gen. anamorph of Septobasidium pilosum from Brasil
Authors: Hughes S. J. , Cavalcanti Wlandemir de A.
Published: April 2011

Two anamorphs on leaves and branches of Mangifera indica from Brasil are illustrated and described: Janetia mangiferae n.sp. and Johncouchia mangiferae (Batista) comb. nov. (syn. Cladotrichum mangiferae Bat.). The latter is the type species of a new genus for the anamorph of Septobasidium pilosum Boed. & Steinm. and is compared with Aegerita webberi Fawcett.
Temporal changes in boreal forest tree canopy cover along a gradient of gamma radiation
Authors: Amiro B. D. , Dugle J. R.
Published: April 2011

A forest site in southeastern Manitoba has been irradiated by a point source of gamma rays continuously since 1973, and measurements have been made yearly to study the change in boreal forest canopy cover along the radiation gradient. After 10 years of chronic irradiation, a zone of total tree death has resulted from mean dose rates between 25 and 62 mGy h−1. Tree canopy cover was reduced at mean dose rates exceeding ~ 4.5 mGy h−1 and the largest reduction occurred in the first 2 years of irradiation. The temporal responses of seven woody species to gamma radiation are presented. Bebb's willow, trembling aspen, speckled alder, and paper birch were less sensitive to radiation than black spruce, balsam fir, and jack pine. The results confirm that gymnosperms are more sensitive to gamma rays than angiosperms.
Geoperception in primary and lateral roots of Phaseolus vulgaris (Fabaceae). III. A model to explain the differential georesponsiveness of primary and lateral roots
Authors: Ransom J. Steven , Moore Randy
Published: April 2011

Half-tipped primary and lateral roots of Phaseolus vulgaris bend toward the side of the root on which the intact half tip remains. Therefore, tips of lateral and primary roots produce growth effectors capable of inducing gravicurvature. The asymmetrical placement of a tip of a lateral root onto a detipped primary root results in the root bending toward the side of the root onto which the tip was placed. That is, the lesser graviresponsiveness of lateral roots as compared with primary roots is not due to the inability of their caps to produce growth inhibitors. The more pronounced graviresponsiveness of primary roots is positively correlated with the presence of columella tissues that are 3.8 times longer, 1.7 times wider, and 10.5 times more voluminous than the columellas of lateral roots. We propose that the lack of graviresponsiveness exhibited by lateral roots is due to the facts that they (i) produce smaller amounts of the inhibitor than primary (i.e., strongly graviresponsive) roots and (ii) are unable to redistribute the inhibitor so as to be able to create a concentration gradient sufficient to induce a pronounced gravitropic response.
The hybrid identity and taxonomic status of Pyrola sikkimensis (Ericaceae) from eastern Himalaya
Authors: Haber Erich
Published: April 2011

Pyrola sikkimensis is recognized as being of hybrid origin between P. minor and P. rotundifolia s.l. on the basis of several distinctive floral features that characterize hybrids of Pyrola in which one of the parents is P. minor. The similarity in morphology of P. sikkimensis to P. media, an amphidiploid between P. minor and P. rotundifolia, suggests that P. sikkimensis is conspecific with P. media.
Effet stimulant de la poly-D-lysine sur l'entrée en mitose de cellules G2 du méristème racinaire d'Allium sativum
Authors: Benbadis M.-C. , Delage M. , Daouse G.
Published: April 2011

Cell proliferation in Allium sativum L. primary root meristems is stimulated by poly-D-lysine. This effect has been studied on asynchronous and on hydroxyurea-synchronized meristems using cell kinetics techniques and DNA microdensitometry. The rapid increase of mitotic indices is the result of the onset of mitosis in 4C cells which are arrested in G2. However, neither the initiation of DNA synthesis in G1 cells, nor the labelling index of roots continuously incubated with tritiated thymidine, are altered. Thus, poly-D-lysine has a selective effect on G2 cells, triggering the onset of mitosis in those cells. Our results, which show that mitosis can be induced in G2 cells by an exogenous supply of a polycationic compound, are discussed in relation to the occurrence and the features of G2-arrested cells within root meristems.
Effects of CO2 enrichment and temperature on growth in two C4 weeds, Echinochloa crus-galli and Eleusine indica
Authors: Potvin Catherine , Strain Boyd R.
Published: April 2011

Mathematical growth analyses were carried out on two C4 grasses, Echinochloa crus-galli and Eleusine indica, to test the influence of CO2 enrichment and temperature on growth. Echinochloa populations from Québec, North Carolina, and Mississippi and a single population of Eleusine from Mississippi were grown for 48 days at two CO2 concentrations (350 and 675 μL∙L−1) and three temperature regimes (28:22, 24:18, and 21:15 °C). CO2 enrichment generated an increased root dry weight and induced an earlier development of inflorescences. Net assimilation rate, the only other parameter to respond to CO2 enrichment, was higher for plants grown at high CO2 concentrations during the first harvest interval. Biomass partitioning was affected by temperature. Root dry weight was greater in plants grown at 21:15 °C while more leaf area was produced in warmer temperature regimes. Only plants from Québec maintained normal growth rates under the 21:15 °C regime, suggesting that northern C4 plants are better suited for growth at low temperatures than southern ones.
Periclinal and oblique divisions in the surface layer of the shoot apex of tomato (Lycopersicon esculentum)
Authors: Sawhney V. K. , Sekhar K. N. Chandra
Published: April 2011

The occurrence of periclinal and obliquely oriented planes of mitotic figures and cell walls in the outermost layer of the tomato (Lycopersicon esculentum Mill.) shoot meristem is reported. The frequency of such divisions was low, but periclinally and obliquely oriented walls were distributed throughout the surface layer of the meristem and the young leaf primordia.
Relationships among morphology, geography, and interfertility in Medicago
Authors: Small Ernest , Lefkovitch L. P.
Published: April 2011

A numerical examination was conducted of the relationships among 99 morphological characters, geographical distribution, and ability to hybridize among the 55 species of the Old World genus Medicago (Leguminosae) currently recognized. Nearest morphological neighbours were found to be much more likely to be crossable than other species combinations. More than half of the species combinations proved to have sympatric geographical ranges. Sympatric species were not found to be significantly more crossable than nonsympatric species. Sympatry was not found to be significantly different in frequency among closely related species than among less closely related species. Using Lefkovitch's measure of biogeographical distance, a positive relationship between morphological divergence and geographical separation was demonstrated. However, the relationship was not strong. This may be due to the very large mean intercentroid distance found between the 54 pairs of nearest morphological neighbours, about 2800 km. This suggests that geographical divergence has developed so extensively between even the most closely related species of Medicago that random species migrations have substantially obscured relationships.
Vegetation sequence on three boreal Manitoban rock outcrops and seral position of Opuntia fragilis
Authors: Frego Katherine A. , Staniforth Richard J.
Published: April 2011

The vegetation sequence on granitic outcrops containing Opuntia fragilis (Nutt.) Haw. was examined at three sites in southeastern Manitoba. The experimentally determined species sequence supported those in the literature: (0) bare rock – pioneer lichens, (1) primary moss mat, (2) secondary moss and lichen mat, (3) tertiary moss and lichen mat, (4) stress-tolerant ruderals, (5) stress-tolerant perennials, (6) perennial grasses, and (7) chamaephytes and phanerophytes. The primary factor determining the sequence was substrate depth, presumably because of its effect on moisture retention. The species composition of the earliest seral stages (0–3) was consistent at all three sites, presumably as a result of propagule availability and the extremely xeric nature of the sere. Variations in the species of subsequent stages may be attributed to the more restrictive dispersal mechanisms of mesic species. Local variations in vegetation scale and pattern were caused by slope, disturbance, crevices or depressions, and encroachment of forest at the forest–outcrop ecotone. Opuntia fragilis, a stress-tolerant perennial, was the first vascular plant in the sequence and colonized mats in stage 2 (occasionally 3). It did not persist in stage 5.
The ultrastructure of Ulothrix mucosa. II. The flagellar apparatus of the zoospore
Authors: Lokhorst G. M. , Star W.
Published: April 2011

The actual spatial configuration of the flagellar apparatus of the quadriflagellate zoospore of Ulothrix mucosa Thuret has been reconstructed by serial sectioning analysis. This apparatus shows an architecture quite similar to that found in related Ulvophyceae. Common characteristics are the differently leveled basal body pairs; the 180° rotational symmetry of the flagellar apparatus; the proximal overlap of the upper basal bodies which are displaced with respect to each other in the counterclockwise direction; terminal caps; four cruciately arranged microtubular roots (R2, R4); a distinctly striated distal connecting fibre that interconnects the upper basal bodies; and striated bands (SB1) that join the R4s to the lower basal bodies. Specific features are the arrangement of the R4 in a three over one configuration when entering the proximal region of the flagellar apparatus; the differently shaped proximal sheaths and their association with a proximal sheath connecting band; the presence of two system II fibres (rhizoplasts) which arise from the lower basal body pair; the striated bands (SB2) that connect the R2s to the lower basal bodies; the distinct striation of the system I fibre, which is not only intimately associated with the R2, but also with the R4 (not earlier reported for an ulvophycean alga); and, finally, the relevant displacement of the lower basal body pair in a counterclockwise direction of approximately half a basal body diameter. In light of these findings the taxonomic status of the Ulotrichales as well as of the Ulvophyceae is discussed.
Gibberellinlike activity in phloem sap of the oil palm tree (Elaeis guineensis)
Authors: Otusanya O. O. , Adebona A. C.
Published: April 2011

During a 1-year cycle the acidic, ethyl acetate soluble gibberellinlike activity in the phloem sap of the emergent male inflorescence of the oil palm tree (Elaesis guineensis Jacq.) was assayed with barley half-seeds after separation on paper chromatography. Gibberellinlike substances which cochromatograph with gibberellic acid 3 were translocated to the male emerging inflorescence stalk. Their quantity was maximal (45 μg L−1 of sap) in late November, and minimal (1.5 μg L−1 of sap) during March to August.
The status and distribution of Carex subimpressa (Cyperaceae)
Authors: Reznicek A. A. , Catling P. M.
Published: April 2011

Carex subimpressa, originally described as a hybrid of C. hyalinolepsis and C. lanuginosa, has been reported over a wide area and beyond the range of C. hyalinolepis. Consequently it has been accorded specific rank. Various aspects of morphology reflected in scatter diagrams as well as intermediate stomatal structure revealed through scanning electron microscopy and sectioning support the hybrid origin as originally proposed. This is further supported by field studies of natural populations where both putative parents were invariably present. Reports from beyond the range of one or both parents are the result of misidentification. The diagnostic character combination includes sparsely pubescent perigynia 4.2–6.4 mm long, with relatively short beaks, leaves 4.5–11 mm wide, and ligules 1.8–9 mm long.
Analyzing growth in cell cultures. I. Calculating growth rates
Authors: Singer Susan R.
Published: April 2011

Growth is the major parameter used to assess novel phenotypes derived from plant tissue cultures. Any quantitative analysis of growth must have an explicit rational basis. Frequently this criterion is not met. For example, the calculation (W2 − W1)/W1(W1 = initial weight; W2 = final weight) approximates neither linear nor exponential growth. Yet, it is a common method of analysis, as is the related calculation W2/W1. When absolute growth values provide insufficient information, meaningful relative growth rate equations can be utilized. Relative growth rates should be evaluated as ln (W2/W1)/(t2 − t1) for t = time, thereby yielding a constant growth rate for exponentially growing cell lines. Linear growth (root growth, for example) can be approximated by 2(W2 − W1)/((W1 + W2)(t2 − t1)). All methods of analysis we have encountered assume that relative growth at a given instant depends on total mass. The possibility exists that growth may actually be proportional to mass raised to some power less than one. For example, growth could be limited to a thin outer shell of a spherical callus. Then the relative growth rate would equal 3(W21/3 − W11/3)/(t2 − t1). Data can be seriously distorted when inappropriate calculations are used. Such distortions are exacerbated when comparisons are made. In all cases an adequate assessment of growth kinetics for each cell line and each treatment is essential.
Lead translocation and localization in Allium cepa roots
Authors: Wierzbicka Małgorzata
Published: April 2011

Based on autoradiographic (210Pb) and ultrastructural studies, it was determined that lead is taken up from solution with the same intensity along the length of Allium cepa L. roots. As expected, the rate of uptake is dependent on the lead concentration and exposure time of the roots to lead salts. Lead takes about 80 min to penetrate radially through consecutive root tip layers in the meristematic zone. Lead is first deposited on the root surface, and then is translocated radially through the middle lamella (apoplast) of root cap cells. The lead reaches protoderm cells and meristematic cells of the hypodermis, where it penetrates into the symplast. Lead passes through consecutive ground meristem tissue layers at the rate of 1 cell layer/5 min. Its deposition in the ground meristem tissue is surprisingly nonuniform. It is deposited uniformly in the first six layers, but in the deeper (7th to 10th) layers, lead deposits are encountered in intercellular spaces and the middle lamellae, then in the cell walls near the plasmalemma, and finally in vacuoles.
Oxalic acid and calcium oxalate produced by Leucostoma cincta and L. persoonii in culture and in peach bark tissues
Authors: Traquair J. A.
Published: April 2011

Oxalic acid and crystals of calcium oxalate were produced during growth of Leucostoma cincta and L. persoonii on potato dextrose agar and in peach bark tissues. The identification of calcium oxalate was based on solubility characteristics, the results of KMnO4 titration, positive staining with silver nitrate – dithiooxamide, and crystal morphology as observed with light and scanning electron microscopes. Oxalic acid was detected by gas chromatography. This is the first report of oxalic acid production by both Leucostoma species causing peach canker. Calcium oxalate crystals observed on or near hyphae in culture were similar to crystals in artificially inoculated peach bark tissues. Addition of oxalic acid solutions alone to inner bark tissues caused maceration and necrosis. These results indicate a role for oxalic acid in the early stages of pathogenesis by Leucostoma spp. Tetragonal (bipyramidal) and prismatic calcium oxalate crystals formed on bark wounds treated with oxalic acid solutions were similar to those observed in infected tissues and in culture media amended with oxalic acid.