bluuebunny/crossref_metadata_2025 huggingface dataset:
Aspects arising from the use of inhibitors in phloem transport studies
Authors: Willenbrink Johannes
Published: April 2011

Experiments on the movement of 14C-assimilates through dissected vascular bundles of Pelargonium zonale are reviewed. Potassium cyanide (KCN) applied to the central bundle causes localized, reversible blockage of transport. Both antimycin and atractylate, but not ouabain inhibit the movement of metabolites through the phloem. The proton ionophore, CCCP completely suppresses translocation at 10−7 M, however, cell membranes are damaged. Valinomycin applied to cut bundles causes serious disturbances in carbon metabolism as shown by the increased label in sugar phosphates. Cytochalasin B does not affect translocation. Limitations on conclusions drawn from inhibitor studies are discussed.
Ultrastructural changes in sunflower root cells in relation to boron deficiency and added auxin
Authors: Hirsch Ann M. , Torrey John G.
Published: April 2011

The responses of sunflower root cells to conditions of boron deficiency and to the addition of exogenous auxin were studied on the ultrastructural level. Although gross morphological effects such as inhibition of root elongation and a change in the direction of cell expansion from longitudinal to radial are similar in both auxin-treated and boron-deficient seedling roots, ultrastructural changes are different in the two treatments. An increase in cell wall thickness and a loss of membrane integrity are seen as early as 6 h in seedlings grown without boron. Auxin-treated root cells do not show this response. A role for boron may involve maintenance of membrane integrity rather than determining endogenous auxin levels.
Contribution au problème des fusions : la métatopie dans l'inflorescence de Cornus sericea (syn. C. stolonifera)
Authors: Barabé Denis , Vieth Joachim
Published: April 2011

The purpose of this study is to provide a contribution to the problem of organ displacement and to explain the organization of the typical inflorescence of Cornus sericea L. Our analysis is based on anatomical and morphological data from normal and subnormal specimens.The singular nodal structure of the "normal" inflorescence of C. sericea results from two generalized deformations, a concaulescence and a recaulescence, appearing simultaneously. This phenomenon is particularly visible on the first pair of paracladia. These paracladia are united with the primary axis along a certain distance, and the inflorescential bracts are displaced along their axillary branches. Analysis of subnormal forms indicates that nodal deformation has a particular morphological nature which probably results from the activity of an intercalary meristem in the nodal region. In the case of the normal inflorescence, this segment cannot be considered homologous to either a node, a caulome, or a phyllome.The appendages carried by the first and sometimes by the second pair of paraclads, are appendicular organs, homologous to the foliaceous inflorescential bracts that we see on many teratological forms and in other species of Cornus.
An empirical regression function suitable for modelling spore germination subject to temperature threshold
Authors: Payandeh Bijan , Wallace D. R. , MacLeod D. M.
Published: April 2011

Nonlinear regression analysis and least squares approximation techniques were employed to express percent spore germination as a function of time and temperature. Two sets of spore germination data under varying temperatures were used. A seven-parameter nonlinear regression model was found to fit the data equally as well as previously used mixed linear and two-stage nonlinear regression models. The proposed model is very flexible and allows for the expression of temperature threshold effects. In addition to providing a common set of parameters applicable to the full range of temperatures under consideration, such estimated parameters are amenable to biological interpretation.
Chromosome numbers for Isoëtes in northeastern North America
Authors: Kott L. S. , Britton D. M.
Published: April 2011

Based on spore characteristics, five species and one distinct form of Isoëtes occur in northeastern North America. Two of the taxa, I. echinospora Dur. And I. eatonii Dodge, are diploids with a chromosome count of 2n = 22; three, I. riparia Engelm., I. tuckermanii A. Br., and I. macrospora f. hieroglyphica (Eat.) Pfeiffer, are tetraploids (2n = 44); and one, I. macrospora Dur., is decaploid (2n = 110).
Fusion of cell sap vacuoles subsequent to protoplast fusion
Authors: Constabel F. , Koblitz H. , Kirkpatrick J. W. , Rambold S.
Published: April 2011

The fusion of protoplasts isolated from leaves of Catharanthus roseus and Nicotiana glauca with protoplasts from Haplopappus gracilis cell cultures resulted in heavy precipitation of granules in vacuoles of the fusion products. The occurrence of this precipitate is seen as an indication that subsequent to protoplast fusion cell sap vacuoles fuse also.
Occurrence of tyloses and their ultrastructural differentiation from similarly configured structures in American elm infected by Ceratocystis ulmi
Authors: Ouellette G. B.
Published: April 2011

Tylosis formation in American elm was sparse during development of Ceratocystis ulmi infection in the period of highest tree susceptibility, as observed in numerous periodically sampled field-inoculated trees from 1970–1978. Tyloses are more frequent in greenhouse-grown than in field-grown trees. They are abundant, sometimes in invaded vessels, in field samples collected after acute wilting (in surviving trees) at the end of summer or during the following spring. Aborted, collapsed, or disintegrated tyloses have been observed. The first tylosis wall layer (continuous with the protective layer of the parenchyma cell) is thickened in some tyloses; papilla-like structures are present in others. Often, masses of osmiophilic material are located outside the tylosis, with strands extending into the tylosis wall. An almost translucent, often lamellate layer is deposited in more mature tyloses.Other structures having the external configuration of tyloses but differing from them in organization, form abundantly in vessels shortly after inoculation in both greenhouse- and field-grown trees. Called bubbles, these structures are similar to, and often in continuity with, a coating on inner vessel walls.These observations are discussed in relation to previous ultrastructural observations of infected elms and in general with other plant wilts of fungal origin.
Localized freezing predisposition to Botryosphaeria canker in differentially frozen woody stems
Authors: Wene E. G. , Schoeneweiss D. F.
Published: April 2011

Two-year-old seedlings of European mountain ash (Sorbus aucuparia L.) were differentially exposed to freezing temperatures. Basal portions of plants were maintained above 0 °C with electrical heating cables and insulation during a rapid drop in ambient air temperature from 5 to −30 °C. Plants were inoculated at three heights on the stem with a nonaggressive stem canker pathogen, Botryosphaeria dothidea, to determine the predisposing effect of differential freezing on the susceptibility of whole plant stems. Exposed portions of stems were predisposed to attack by B. dothidea but unfrozen portions remained resistant. The pathogen colonized frozen tissue near the margins of insulation but did not colonize unfrozen portions. This method provided an interface between resistant and susceptible tissue on intact whole plants.
The ultrastructure of quiescent buds of Tilia europaea
Authors: Cragg F.J. , Willison J. H. M.
Published: April 2011

Shoot apices from quiescent axillary buds of the European linden tree were collected at three periods during the winter and prepared for electron microscopy by freeze-fracturing without pretreatment (i.e., no chemical fixation or glycerol infiltration). Cell structures were well preserved and not damaged by ice crystal formation. Tissue fine structure was comparable with other winter-quiescent tissues (particularly cambia) and showed the following characteristics: plentiful oil droplets, smaller quantities of other storage materials (protein, starch), inactive dictyosomes, and unusual arrangements of endoplasmic reticula (particularly a peripheral reticulum). Oil droplets were not bounded by a membrane. The quantity of oil (by cytoplasmic volume) declined steadily through the winter, presumably fuelling metabolic activity. The relatively flaccid condition of plasma membranes indicated that osmotic pressure was similar inside and outside the cells. Membrane-particle partition coefficients (Kp) between plasma membrane fracture moieties was unusual (< 1), and the significance of this observation in relation to cold acclimatisation is discussed. The appearance of the mouths (neck constrictions) of plasmodesmata changed between midwinter (closed) and early spring (open) and the observations are interpreted to indicate dynamic changes in a sphincter controlling intercellular exchange.
Studies on lichen-dominated systems. XXIII. The control of seasonal rates of net photosynthesis by moisture, light, and temperature in Cladonia rangiferina
Authors: Tegler B. , Kershaw K. A.
Published: April 2011

The net photosynthetic response matrix to four light levels combined with four temperatures and for a full range of thallus hydration has been defined for a Cladonia–woodland population of Cladonia rangiferina in midsummer and early winter. Maximum rates of net photosynthesis are generated between 150 and 200% thallus water content by weight between 15 and 25 °C with low rates being generated at 5 and 35 °C. Light saturation occurs above 600 μE∙m−2∙s−1. There is no evidence of acclimation of photosynthetic optima to temperature but with the onset of early winter there is a marked decrease of respiration rate. An examination of the sensitivity of Cladonia rangiferina in an air-dry state to heat stress shows a rapid decline of net photosynthesis under 45 °C daytime stress. Although 35 °C initially reduces the level of net photosynthesis to some extent, over a 3-week experimental period no further decline is observed. It is suggested that this population of Cladonia rangiferina, which is markedly restriced to a position under the shade of Ledum shrubs, is protected there from the otherwise excessive heat load which occurs on the open Cladonia stellaris surface and which typically reaches 40 °C under full radiation conditions in summer.
Inheritance of pigment deficiencies and ultrastructural defects in plastids of Selaginella kraussiana var. aurea
Authors: Webster Terry R. , Tanno James A.
Published: April 2011

Selaginella kraussiana var. aurea is a pigment deficient cultivar with yellow–green foliage. When selfed, it produces green, yellow–green, and white (lethal) sporelings in a 1:2:1 ratio. This, together with results of further crosses show the aurea character to be controlled by a single nuclear gene with two partially dominant alleles. Chloroplasts of green sporelings possess a well-organized thylakoid system consisting of distinct grana and interconnecting frets. Plastids from yellow–green (aurea) sporelings exhibit a reduced thylakoid system with unusually long grana and aberrant fretwork. The reduced membrane content of aurea plastids is accompanied by a 60% deficiency in both chlorophyll and carotenoid content in mature aurea plants as compared with the green wild type. Plastids of white sporelings are irregular in shape and are apparently blocked at an early stage of development. They possess a very sparse, rudimentary membrane system. The aurea condition in S. kraussiana var. aurea is compared with similar conditions in tobacco, spruce, and soybean.
Mating-type interactions between sporidia of a wheat-bunt fungus Tilletia caries
Authors: Kollmorgen J. F. , Trione E. J.
Published: April 2011

Mating-type interactions between monokaryons (secondary sporidia and mycelia] of Tilletia caries were studied. Preconjugation pegs were produced by sporidia after displacement of stimulating (opposite mating type) cells and the pegs continued to elongate. Sporidia of opposite mating types conjugated when subjected to a treatment that would disrupt fimbrial connections. Multiple hyphal tips were produced by differentiating sporidia separated from monokaryons of opposite mating type. The response was sex specific. In some instances the factors causing these responses were apparently retained in the agar substrate.
Comparative ultrastructure and biochemistry of chytridiomycetous fungi and the future of the Harpochytriales
Authors: Gauriloff Larry P. , Delay Rona J. , Fuller Melvin S.
Published: April 2011

The ultrastructure of the zoospores of Oedogoniomyces lymnaeae and Monoblepharella sp. are reexamined using serial sections. The relative molecular weights of the ribosomal RNA of various chytridiomycetous fungi are also determined and compared. The fine structure of each of these zoospores is very similar. The nucleus and "nuclear cap" are centrally located in the zoospores. The anterior region contains lipid globules, a few large, empty vacuoles and numerous, small vesicles. The posterior region is filled with an electron-translucent material throughout which are scattered spherical mitochondria and large vacuoles with electron-opaque inclusions. The basal body complex is located at the center of the posterior end, and the rumposomal complex is adjacent to the plasmalemma in the posterior region of these zoospores. A system of cisternae that are associated with microbodies appears to connect the lipid globules in the anterior region with the rumposomal complex in the posterior region of these zoospores. Small differences in the structure and distribution of certain organelles are considered minor compared with the overall similarities between these two zoospores. It is suggested that Oedogoniomyces be transferred to the Monoblepharidales. The fine structure of the Harpochytrium hedinii zoospore is not only similar to that of the zoospores studied herein, but also resembles the zoospores of chytrids. The possible relationship of Harpochytrium to the Chytridiales is supported by zoospore ultrastructure and the relative molecular weights of ribosomal RNA. The data available at the present time suggest that the order Harpochytriales be abandoned and that Harpochytrium be considered either a genus of nematosporangial, operculate, eucarpic chytrids or a monoblepharidalean genus with Oedogoniomyces. It is recommended that speculation concerning the taxonimic relationship between Harpochytrium and other Chytridiomycetes be delayed until more data concerning other species of Harpochytrium and monoblepharidalean fungi are available.
Phenolics from Larix needles. XVI. Inter- and intra-clonal variation in Larix leptolepis
Authors: Niemann Gerard J.
Published: April 2011

The quantitative variation of needle flavonoids within and between different clones of Larix leptolepis was determined for leaves growing both on short and on long shoots. Minor quantitative differences were found between trees on one clone, but between different clones large variations occurred, especially for the C-glycoflavone vitexin. Needles growing on long shoots contained more kaempferol-3-(p-coumarylglucoside) and other acylated glycosides and somewhat more vitexin than short-shoot needles, but less kaempferol-, isorhamnetin-, and quercetin-and (or) laricitrin-3-glycosides. No correlation could be found between needle flavonoids and the resistance of some clones to Guignardia laricina.
Studies on the structure and elicitor activity of fungal glucans
Authors: Anderson Anne J.
Published: April 2011

Neutral sugar compositions of materials released from isolated mycelial walls of race 1 and race 2 of Fusarium oxysporum f. sp. lycopersici and Fusarium oxysporum f. sp. cubense were similar (5% ribose, 52% mannose, 28% galactose, 15% glucose). High molecular weight glucans were isolated by ion-exchange chromatography from the cell wall extracts of each of the Fusarium isolates. The linear chain linkage structure of the Fusarium glucans was predominantly 1—3 and 1—6. That of the Colletotrichum lindemuthianum glucans was 1—3 and 1—4. These Fusarium glucans were nearly as effective as glucans from Colletotrichum species at eliciting browning and phytoalexin production in green bean cotyledons. Tomato fruit and stem tissue showed browning and phytoalexin production when exposed to F. oxysporum f. sp. cubense spores. These symptoms did not develop upon treatment of tomato tissues with the Fusarium or Colletotrichum glucans that had elicitor activity in green bean.
Desiccation of oat grains during and following germination, and its effects upon protein synthesis
Authors: Akalehiywot T. , Bewley J. D.
Published: April 2011

After imbibition and germination, oat grains pass from a stage where they are insensitive to desiccation to a stage where they are sensitive. Desiccation of germinating grains results in more rapid completion of germination upon rehydration. However, when the initial imbibition (i.e. predesiccation) time of the grains is taken into account, the total time that the seeds are hydrated before germination is completed is the same as control (once-imbibed) grains. Hence it appears that events occurring prior to desiccation do not have to be repeated for germination to be completed. Grains desiccated during germination commence protein synthesis more quickly, and reform polysomes more quickly, than control (once-imbibed) grains. Likewise, RNA synthesis resumes more quickly. Desiccation of grains during the desiccation-sensitive stage results in almost total impairment of protein and RNA synthesis upon subsequent rehydration. Both ribosomes and poly(A)+-containing RNA are conserved in embryos desiccated during the insensitive stage, but poly(A)+-containing RNA is lost from embryos desiccated during the sensitive stage and there is a further decline upon subsequent rehydration.
Protein synthesis and leucine uptake during fusicoccin-stimulated growth of oat coleoptile tissue
Authors: Doo Ahmed C. , Bown Alan W.
Published: April 2011

Avena coleoptile sections were incubated with or without cycloheximide (CHI) in solutions containing indoleacetic acid (IAA), fusicoccin (FC), or IAA and FC. Resulting growth, incorporation of [3H]leucine into protein, and uptake of [3H]leucine into an ethanol-soluble fraction were determined. FC-stimulated growth was greater and less sensitive to CHI treatment than IAA dependant growth which was virtually eliminated by CHI. IAA alone had little or no influence on [3H]leucine utilization, whereas FC treatment stimulated [3H]leucine incorporation into protein by 36% and uptake into the ethanol-soluble fraction by 75%. CHI inhibited the incorporation of [3H]leucine label into protein such that no significant difference was observed in radioactivity in protein from control, FC-, or IAA-treated tissue. However, CHI did not inhibit the FC-stimulated uptake of [3H]leucine into the ethanol soluble fraction. Total uptake of [3H]leucine obtained from the sum of radioactivities in the protein and ethanol-soluble fractions was stimulated by FC approximately 54% in the absence of CHI and 92% in the presence of CHI. IAA in combination with FC stimulated a further increase in leucine uptake. It is proposed that IAA and FC stimulate growth through processes which differ in their dependency on protein synthesis, and that FC-stimulated incorporation of label into protein results from FC-stimulated leucine uptake, not FC-stimulated protein synthesis.
Etude du polymorphisme intraclonal chez le Verticillium albo-atrum, forme à microsclérotes. I. La morphogénèse des thalles à partir des microconidies et ses variations
Authors: Boisson Claude , Lahlou Houria
Published: April 2011

In vitro thallus regeneration from microconidia was studied to define the stages of morphogenesis of some Moroccan strains of Verticillium albo-atrum Reinke and Berthold, microsclerotial forms: germination of microconidia, initiation and growth of vegetative mycelium, formation of microconidia and microsclerotia. Wild-type phenotypic characteristics such as rate of radial growth, length of time for the appearance of microsclerotia, and morphological aspects of each strain were evaluated.The morphogenesis of clones obtained from isolated microconidia showed however wide variations in percentage of regeneration and in growth and phenotype of the thallus formed from the microconidia. These variations seem to depend in part on the age of the culture from which the microconidia are taken and generally involve modifications in the regeneration potentiality of microconidia and also the appearance of stable morphological variants of which the most frequent is the hyaline type forming no microsclerotia and covered with an abundant white cotton-like aerial mycelium. The consequences of these variations are considered from a phytopathological point of view and especially in relation to experimental inoculation techniques using microconidia.
The effects of water level on the growth and reproduction of Scirpus maritimus var. paludosus
Authors: Lieffers V. J. , Shay J. M.
Published: April 2011

A greenhouse experiment was conducted to examine the effects of water depth on the growth and reproduction of Scirpus maritimus L. Plants grown at or above the water surface had higher shoot survivorship, greater numbers of vegetative tillers, and higher underground biomass, while seed production was small. With increasing water depth plants had taller shoots and greater seed production but total biomass, numbers of vegetative tillers, and underground biomass were reduced. This shift from clonal growth to seed production with increasing water depth is interpreted as a strategy that permits survival of S. maritimus populations through the wet and dry climatic periods of the Canadian prairies.
Light and scanning electron microscopic studies of spore formation in Ustilago pustulata and U. scabiosae
Authors: Deml G. , Nebel M. , Oberwinkler F.
Published: April 2011

The development of sori, sporogenesis, and characteristics of the hyphae in Ustilago pustulata and U. scabiosae have been investigated by light and scanning electron microscopy. The septa of both species form clamp connections. In U. scabiosae the sporogenous cells are comparable with budding mycelia. The teliospores of Ustilago pustulata and U. scabiosae are formed endogenously in chains.
Studies on respiration in Fusarium-infected beans
Authors: Thomas C. A. , Wood R. K. S.
Published: April 2011

Bean plants, when inoculated with Fusarium oxysporum developed disease symptoms 7–9 days later and died within the next 3 weeks. The most common visible symptoms of the disease were wilting, yellowing, vein clearing, and necrosis of the leaves. Just before expression of these symptoms, from 5 days onwards, the leaves of the infected plant respired at a higher rate than those of the healthy plant. With the appearance of the foliar symptoms on the 7th or 8th day, however, the respiration rate began to fall steadily until the plant wilted completely. The tracheal sap of the inoculated plant was found to be toxic and increased the rate of respiration of leaf tissues.
Zoospore ultrastructure of Nowakowskiella elegans and Cladochytrium replicatum (Chytridiales)
Authors: Lucarotti Christopher J.
Published: April 2011

The ultrastructural cytology of the zoospores of the polycentric chytrids, Nowakowskiella elegans (Nowak.) Schroeter and Cladochytrium replicatum Karling is very similar. In both there is a single lipid globule. A microbody lies between the lipid globule and a central, disc-shaped nucleus. On the other side of the nucleus there is a cluster of ribosomes. The ribosome cluster and nucleus are enveloped by a common double membrane. A number of mitochondria are appressed to the outside of the double membrane. A nonkinetosomal centriole is adjacent and parallel to the kinetosome, and there is an electron-opaque area at the base of the flagellum. Linked microtubules, numbering approximately 25 in N. elegans and 19 in C. replicatum, emerge from an area lateral to the kinetosome and run to the rumposome which lies on the surface of the lipid globule and faces the exterior of the zoospore. A number of the kinetosome-associated microtubules lie over the surface of the rumposome and appear connected to it. The significance of these results on taxonomic and phylogenetic concepts of the Chytridiales is discussed.
Somatic hybridization between Nicotiana rustica and N. tabacum. II. Protoplast fusion and selection and regeneration of hybrid plants
Authors: Douglas G. C. , Keller W. A. , Setterfield G.
Published: April 2011

Protoplasts derived from cell suspensions of chlorophyll-deficient Nicotiana rustica L. cv. chlorotica and albino N. tabacum L. were fused by a polyethylene glycol (PEG) treatment. As early as 17 days after fusion bright green cell colonies appeared as a result of genetic complementation for chlorophyll synthesis in the hybrid cells only. For optimal hybrid production a low calcium level (1.05 mM) was essential in the PEG solution. Dimethyl sulfoxide (DMSO) at optimal concentration (2% v/v) when used with PEG increased the frequency of hybrid production over PEG alone. Temperature was not a critical factor in PEG-induced fusion except that where DMSO was used in conjunction with PEG, temperatures of 25 °C or greater were optimal. Over 65% of the hybrid cell colonies could be induced to undergo shoot morphogenesis on osmoticum-free (Nagata and Takebe) medium with 1.0 mg/Lbenzyladenine + 0.05 mg/L naphthaleneacetic acid and 1% sucrose. Under these conditions glucose (0.175–0.35 M) depressed morphogenesis. A number of physiological and environmental conditions were tested to elicit root formation in hybrid shoots but these failed to enhance the frequency of rooting obtained with hormone-free medium. Somatic hybrid plants of N. rustica + N. tabacum were produced thus by-passing sexual incompatibility mechanisms which partially isolate these species.
A reassessment of three widespread resinicolous discomycetes
Authors: Hawksworth D. L. , Sherwood Martha A.
Published: April 2011

The taxonomy and nomenclature of three resinicolous discomycetes previously called Biatorella resinae (Tromera resinae), Retinocyclus abietis (Tromera difformis), and R. olivaceus are reassessed. The first two taxa are congeneric members of the Lecanorales; the earliest available generic name, Sarea Fr., must be adopted for them and the species known as S. resinae and S. difformis, respectively. Retinocyclus olivaceus belongs to the Helotiales and is placed in Claussenomyces as Claussenomyces olivaceus (Fuckel) Sherw., comb.nov. (≡ Retinocyclus olivaceus Fuckel). The typification and nomenclature of generic and specific names are discussed and descriptions and illustrations of the accepted species (including their coelomycete anamorphs) are provided. The identities of four other taxa referred to Tromera were investigated. Tromera ligniaria is a synonym of Claussenomyces atrovirens. The new genus Tromeropsis Sherw., gen.nov. is introduced for Tromera microtheca, and the new combination Tromeropsis microtheca (P. Karsten) Sherw., comb.nov. made. Tromera perfidiosa is almost certainly a synonym of Toninia cumulata, and Tromera aurellae Werner is of uncertain application.
The structure and composition of epilithic diatom communities of the St. Lawrence and Ottawa rivers in the Montreal area
Authors: Seve Michèle A. de , Goldstein Melvin E.
Published: April 2011

The structure and composition of epilithic diatom communities were studied at five stations in the St. Lawrence River and one station in the Ottawa River, adjacent to the south shore of the island of Montreal. The diatom flora was composed of 139 species and varieties of Bacillariophyceae. The species composition generally reflected a eutrophic and organically polluted environment. The structure of the diatom communities of the Ottawa River (station I) and of the St. Lawrence River upstream (station II) and downstream along the south shore of the island of Montreal (stations III and IV) was similar with respect to total number of species (41–44 species), diversity (species richness (d): 3.01–3.88 and Shannon-Weiner information measure of diversity [Formula: see text]: 2.01–3.34), and biomass (463.9–1656.0 μm3/mm2). Further downstream station V had fewer species (12 species) and a significantly (P < 0.05) lower diversity (species richness d: 1.87 and Shannon-Weiner information measure of diversity [Formula: see text]: 0.35). The station below it (station VI) had a significantly (P < 0.05) lower biomass (51.2 μm3/mm2) and a lower density (68 cells/mm2). The structure and composition of the diatom communities at the different stations are discussed in relation to environmental factors.
Effects of some oxidants and antioxidants on senescence of isolated leaves of sunflower with special reference to glycolate content, glycolate oxidase, and catalase activities
Authors: Sarkar Udayan , Choudhuri M. A.
Published: April 2011

Incubation of leaf discs of sunflower (Helianthus annuus L. cv. EC.68414) for 6 days in the dark caused a general decline in the contents of chlorophyll, protein, and glycolate in these tissues as well as in the activities of catalase and glycolate oxidase. Treatments with either glycolate or hydrogen peroxide decreased the contents of chlorophyll and protein and the activity of catalase but increased glycolate oxidase activity, hastening senescence. Treatments with ascorbate or 2-mercaptoethanol significantly arrested the decline in chlorophyll and protein levels, deferring senescence. Glycolate content was reduced in leaves treated with glycolate, hydrogen peroxide, ascorbate, or 2-mercaptoethanol. But the extent of reduction in the latter case was less pronounced than that following treatments with glycolate or hydrogen peroxide. Only the highest concentrations of either ascorbate or 2-mercaptoethanol increased the activity of catalase, whereas glycolate oxidase activity was increased by these chemicals in all concentrations.
Cortical diversity in the Ramalinaceae
Authors: Bowler P. A.
Published: April 2011

In Ramalina, Trichoramalina, and Fistularielia the cortex is two layered, composed of an external layer of variable thickness and an inner layer of periclinally arranged mechanical tissue. The outer layer is a reticulate network of branching cells in a gelatinous matrix which is very thin or absent in patches in some species. The inner layer may be a uniform chondroid sheath or a series of internal ribs, often extending into the medullary region, and is composed of more or less periclinal, longitudinally aligned hyphae. Dievernia and Ramalinopsis have a single tissued cortex which is derived from the external cortex of a Ramalina cortex with the mechanical tissue lacking. The lower cortex in Ramalinopsis is melanized and has occasional fascicles of mechanical tissue. Niebla species exhibit three intergrading cortical arrangements. The N. homalea group and other species with a bladelike morphology have a thick outer cortex with palisade cell lines and a subtending layer of supportive tissue. Most species have conspicuous chondroid strands in the medulla which are not attached to the cortex and may form from medullary hyphae. The N. ceruchis group, composed of terete plants, have a thin cortex of branching hyphae in a matrix with mechanical tissue either absent or sparsely present. Chondroid strands are usually poorly developed, and are only a few cells thick in the medulla. The saxicolous N. combeoides group, derived from the N. ceruchis line, have a thick mechanical layer and a variable palisade layer. Chondroid strands are very sparse or absent. Cenozosia, a monotypic genus endemic to South America, is anatomically similar to South American N. ceruchis. This hollow species has frequent chondroid strands which crisscross the lumen of the branches in some morphs.
Seed germination and seedling establishment of Calamovilfa longifolia on Lake Huron sand dunes
Authors: Maun M. A.
Published: April 2011

Caryopses ("seeds") of Calamovilfa longifolia (Hook.) Scribn. are dimorphic (brown and white) and are each enclosed in a lemma and palea. The most complete germination was obtained in lighted (fluorescent light of 1600 lx) growth chambers set at alternating temperatures of 25 °C day (14 h) and 10 °C night. Seed stratification did not increase total germination but the rate of germination was increased. The seeds imbibed about 50% by weight of water before germination was initiated.Under field conditions seeds accumulated in depressions. Seedlings failed to emerge from depths greater than 6 cm. The survival rate of seedlings was very low (0.5%) during 1978 because of a dry summer but was considerably higher in 1979 on south slopes (33%), under willow clumps (44%), and on north slopes (56%). Seedling mortality was due to high soil temperatures, desiccation, burial or exposure of seedlings, and biotic agents. Seedlings emerged from the soil mainly by elongation of the first internode. The coleoptile seemed to act as a protective sheath against high soil temperatures for the growing point enclosed within it. A significantly linear increase in height of seedlings, root length, and number of leaves occurred with an increase in the age of seedlings during both years.
Infundibura, a new hyphomycete with unique appendages
Authors: Raj T. R. Nag , Kendrick B.
Published: April 2011

A new hyphomycete is described with gelatinous, sporodochioid conidiomata; holoblastic-solitary conidia with a characteristic basal footlike process, a funnel-shaped, mucoid, apical appendage, and a terete, mucoid basal appendage. The novel mode of appendage development by gelatinization of predetermined areas of conidium wall and significance in conidium secession and dispersal are examined.
Potebniamyces gallicola n.sp., from dwarf mistletoe infections in western hemlock
Authors: Funk A. , Smith R. B.
Published: April 2011

Potebniamyces gallicola n.sp. is described from dwarf mistletoe galls (Arceuthobium tsugense (Rosendahl) G. N. Jones) on western hemlock (Tsuga heterophylla (Raf.) Sarg.), growing in British Columbia, Canada. It has a typical Phacidiopycnis anamorph which is produced both in the host and in culture, as well as hyphal "bud" conidia produced in fresh agar cultures.
Patterns of vegetation in the vicinity of an industrially disturbed ecosystem, Sudbury, Ontario
Authors: Amiro Brian D. , Courtin Gerard M.
Published: April 2011

During the past century, forests in the vicinity of Sudbury, Ont., have been either destroyed or disturbed by logging, fires, and industrial pollution. These factors have produced an atypical mosaic of vegetation communities. This study investigates the patterns of plant communities that characterize this disturbed ecosystem.Nine major plant communities were found to predominate. These were determined by classification of the tree stratum with the aid of a hierarchical cluster analysis that was applied to data gathered from 142 quantitatively sampled field sites.These communities tend to be regulated by topography, soils, and distance from pollution sources. They can be grouped into two main types. The barren, birch transition and maple transition communities form a grouping that is attributed to pollution whereas the remaining six types are typical of the hemlock – white pine – northern hardwoods forest. The first three communities are restricted to the industrially disturbed region near Sudbury. Since they are peculiar, their dynamics are unknown and require further autecological research. Such an investigation could provide valuable insights into the pattern of succession in an ecosystem that is regulated by human activities.
Plant regeneration from meristems of grain legumes: soybean, cowpea, peanut, chickpea, and bean
Authors: Kartha K. K. , Pahl K. , Leung N. L. , Mroginski L. A.
Published: April 2011

The regeneration potential of shoot apical meristems of soybean, cowpea, peanut, chickpea, and bean was studied on agar-solidified MS nutrient medium supplemented with various concentrations of benzyladenine (BA) and napthaleneacetic acid (NAA) alone or in combination. Soybean plantlets could be regenerated only when 0.05–0.1 μM BA was applied in conjunction with 1 μM NAA. Cowpea meristems did not require exogenously supplied hormones for maximum (100%) plant regeneration to occur. Extremely low levels of BA (0.1–0.005 μM) in association with low levels of NAA (0.05 μM) also induced plant regeneration at very high frequency. Similarly, bean meristems differentiated into plantlets on hormone-free medium or on medium containing only the auxin, NAA. Multiple bud regeneration (15–30 buds per meristem) was induced from bean meristems at high cytokinin levels (10 μM BA). Elongated bean shoots differentiated roots on half-strength MS medium containing 1 μM indoleacetic acid (IAA). Although most combinations of BA or BA and NAA induced shoot regeneration from peanut and chickpea meristems, whole plant regeneration occurred more frequently (75%) from the former only when 0.1 μM BA was applied in combination with 10 μM NAA. Multiple axillary branching occurred from the main shoots regenerated from chickpea meristems; however, rooting occurred only when these shoots were recultured on medium containing 1 μM indolebutyric acid (IBA). Plantlets regenerated from the meristems of all these grain legumes were successfully transferred to pots and grown to maturity.
A new and unusual fungus living in the gut of free-living nematodes
Authors: Tzean S. S. , Barron G. L.
Published: April 2011

Spirogyromyces vermicola is described as a new genus and species inhabiting the gut of free-living nematodes. The spores are ingested and attach to the gut wall of the host. A stout, helicoid, septate hypha grows down the gut and produces one or several helicoid branches. One or more filiform spores arise from the vicinity of each septum and coil around the main axis or its branches. The mature thallus can fill the gut of the nematode with primary (main axis), secondary (branches), and tertiary (spores) coils of striking symmetry. Spores break away from the thallus and are defecated through the anal orifice to the exterior where they are eventually ingested to initiate infection.
Lignicolous and zoosporic fungi in marine environments of Hudson Bay
Authors: Booth Tom
Published: April 2011

Wood and soil samples from Churchill and Great Whale (Hudson Bay) were surveyed or baited for recovery of marine fungi. A total of 14 ascomycetes, 7 fungi imperfecti, and 13 zoosporic fungi are reported. Amylocarpus encephaloides, Cephalosporium sp., Corollospora comata, Dictysporium pelagicum, Haligena amicta, Haligena elaterophora, Halosphaeria maritima, H. mediosetigera, H. quadriremis, H. stellata, Herpotrichiella ciliomaris, Nais inornata, Papulospora halima, Phialophora sp., Phoma sp., Schizochytrium aggregatum, Thraustochytrium aggregatum, T. multirudimentale, T. pachydermum, T. roseum, Trichocladium achrasporum, and Zalerion varium are recorded for the first time from arctic marine sites. Each species is discussed in terms of morphological features, taxonomic deposition, and ecological considerations.
Some comments on the origin and evolution of conifers
Authors: Stockey Ruth A.
Published: April 2011

During the last several years there has been an increased emphasis on the study of conifer evolution including various aspects of their reproductive biology. The occurrence of similar stelar features as well as trends in the evolution of reproductive structures still point to cordaitalean affinities for the Coniferales. The evolutionary history of such families as the Pinaceae, Araucariaceae, and Taxodiaceae is beginning to be elucidated as well as that of certain extinct families including the Cheirolepidaceae and the Voltziaceae. Systematic investigations of fossil cone vasculature and resin canal distribution, leaf cuticles, seed integuments, and embryo structure not only have increased our knowledge of conifer evolution but also have led to changes in our views on the systematics of extant conifer groups.
Response of hawkweed (Hieracium floribundum) patches to NPK fertilizer in an abandoned pasture
Authors: Reader R. J. , Watt W. H.
Published: April 2011

Fertilizer (336 kg ha−1 year−1 NPK) was applied to an abandoned pasture in southern Ontario to investigate the impact of changing soil fertility on the process of patch formation by hawkweeds (mainly Hieracium floribundum Wimm. and Grab.: Compositae). A single application of fertilizer was sufficient to increase the grass standing crop, reduce the hawkweed standing crop, and thereby temporarily halt the process of patch formation in areas initially dominated by grasses (mainly Poa compressa L.). Repeated (i.e., annually for 4 years) fertilization simply increased further the predominance of grasses in these areas. In dense, well-established hawkweed patches annual fertilizer treatment was essential to maintain the increased standing crop of grasses. In these dense patches even repeated fertilizer application had no effect on the standing crop of hawkweed. The experimental results clearly showed that soil fertility could influence the outcome of grass–hawkweed interactions in this pasture. Presumably soil fertility is an important determinant of the rate of patch formation by hawkweeds.
Export of 14C- and 11C-labelled assimilate from wheat and maize leaves: effects of parachloromercurobenzylsulphonic acid and fusicoccin and of potassium deficiency
Authors: Thompson R. G. , Dale J. E.
Published: April 2011

Tracer exported from wheat and maize leaves after photosynthetic fixation was resolved into theoretical pools by mathematical analysis of the rate of loss of either 14C or 11C from the leaf. Fusicoccin, known to stimulate the proton–sucrose symport, had no effect on the rate constants of exchange between pools or loading into the translocation stream of normal plants. K+-deficient plants showed an increased transfer of C into the storage pool when treated with fusicoccin. Parachloromercurobenzylsulphonic acid known to inhibit export not only reduced the rate constant for export but also increased the exchange from the export pool to the storage pool.
Ectomycorrhizal fungi of Salix rotundifolia III. Resynthesized mycorrhizal complexes and their surface phosphatase activities
Authors: Antibus R. K. , Croxdale J. G. , Miller O. K. , Linkins A. E.
Published: April 2011

Pure culture isolates were obtained from fungi fruiting in the vicinity of dwarf willows at Barrow and Cape Simpson, Alaska. Four of these isolates and one isolate from Maryland were tested for their ability to form ectomycorrhizae with cuttings of Salix rotundifolia under controlled environmental conditions. Isolates of Entoloma sericeum, Hebelomapusillum, and Cenococcum geophilum from Barrow and Cape Simpson, Alaska all formed typical ectomycorrhizae with S. rotundifolia, while an isolate of C. geophilum from a temperate ecosystem (Maryland) did not.All of the ectomycorrhizae synthesized with S. rotundifolia, plus uncolonized roots, demonstrated an ability to hydrolyze p-nitrophenyl phosphate at a pH of 4.7. The acid phosphatase activity of E. sericeum ectomycorrhizae was from 10 to 40 times as great as that demonstrated by other mycorrhizal and nonmycorrhizal roots on a surface area basis.
Development of root nodules of mung bean (Vigna radiata): a reinvestigation of endocytosis
Authors: Newcomb William , McIntyre Laurel
Published: April 2011

The release of rhizobia from infection threads of mung bean (Vigna radiata) root nodules is an endocytotic process. The peribacteroid membrane surrounding the released bacteria is initially derived from the host plasma membrane which surrounds the infection thread and not from the nuclear envelope as previously reported by Prasad and De. Endoplasmic reticulum (ER) profiles and Golgi vesicles fuse with the infection thread cell wall and adjacent host plasma membrane. Although some ER profiles were continuous with the outer membrane of the nuclear envelope, no continuities of the nuclear envelope with the infection thread, the host plasma membrane, or the peribacteroid membrane were observed. Furthermore, no blebbing of the nuclear envelope was observed.
Responses of the moss Tortula ruralis to desiccation treatments. II. Variations in desiccation tolerance
Authors: Schonbeck Mark W. , Bewley J. Derek
Published: April 2011

Variations in the apparent desiccation tolerance of the moss Tortula ruralis were traced to several causes. When the moss was kept continuously hydrated for several days, desiccation tolerance tended to decrease ("dehardening"). Conversely, daily episodes of drying and rehydration induced hardening so that the moss could tolerate rapid drying to a tissue water content of 0.008 g∙g dry weight−1.Different clumps of moss showed very different degrees of desiccation tolerance. The least tolerant samples suffered severe damage after rapid drying, whereas the most tolerant suffered little damage, and did not deharden during 3 days continuous hydration.
Enzymes of nitrogen assimilation during seed development in normal and high lysine mutants in maize (Zea mays, W64A)
Authors: Misra Santosh , Oaks Ann
Published: April 2011

Enzymes involved in nitrogen metabolism in endosperms of a normal variety of maize (W64A) and isogenic high lysine mutants (opaque-2 and floury-2) were examined. Glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), asparaginase, asparagine synthetase, and glutamine synthetase were present in the immature endosperm in all three genotypes; increased in activity just prior to the onset of zein biosynthesis; and remained at maximal levels during the period of rapid accumulation of nitrogen. With the exception of GOGAT trends and levels of activities were similar in all cases. Opaque-2 mutants had higher levels of GOGAT (29 ± 0.5 nmol∙min−1 endosperm−1 at day 20 postpollination) than floury-2 (19 ± 0.07) or W64A (13 ± 0.6). Levels of aspartate, asparagine, glutamate, and glutamine were also higher in the high lysine mutants throughout the developmental sequence. NH4+ in the endosperm rose from low levels at day 5 (0.1 μmol∙endosperm−1) to significant levels (1.3, 1.7, and 1.98 μmol∙endosperm−1 in normal, floury-2, and opaque-2, respectively) between 20 and 25 days and then declined. The decline was less apparent in the mutants. Levels of an endopeptidase increased initially in the control and then declined. In the mutants the decline in activity was less apparent and this resulted in higher levels of protease activities at later stages of development. RNAase activities were higher in the mutants throughout the developmental sequence. Where differences were observed, they were more apparent in the opaque-2 than in the floury-2 mutants.
Seasonal growth and standing crop of Scirpus maritimus var. paludosus in Saskatchewan
Authors: Lieffers V. J. , Shay Jennifer M.
Published: April 2011

Shoots of Scirpus maritimus var. paludosus sprout from overwintered tubers in May. Stem growth is rapid and within 2–3 weeks lateral rhizomes extend outwards and produce tillers with new tubers at their bases. By August up to four new shoots are produced in a rhizome–shoot series. All aboveground biomass is dead by late October but tubers overwinter to develop the following growing season. The ratio of below- to above-ground biomass of the rhizome–shoot series increased from 0.20 to 0.76 from early to late summer. The ratio of below- to above-ground biomass of individual stems was highest at the youngest end of the rhizome–shoot series.Stem density and inflorescence and total biomass were monitored at three sites over three growing seasons. The sites had large fluctuations in salinity in response to changes in water depth. Among all sites, maximum stem density reached 380 stems/m2 by late July, slightly before the maximum standing crop of 625 g/m2 was attained. At one site, changes in water levels and salinity increased the peak aboveground standing crop 22-fold (from 27 to 600 g/m2) from 1978 to 1979. A mathematical equation predicting the seasonal aboveground standing crop of S. maritimus was developed using water depth and conductivity as predictor variables.