bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and ultrastructure of the marine, parasitic oomycete, Lagenisma coscinodisci (Lagenidiales): sexual reproduction
Authors: Schnepf E. , Deichgräber G. , Drebes G.
Published: May 2008

Fine structural details of antheridia and oogonia, of cytogamy, plasmogamy, and karyogamy, and finally of the development of the oospore are described. Sexually determined zoospores (most probably zoomeiospores) resemble vegetative primary zoospores (zoomitospores). They form gametangia (antheridia or oogonia) which are similar to vegetative primary cysts. An antheridium germinates with a fertilization tube which penetrates the oogonium. As seen in abnormal cell fusions, the tip of the fertilization tube opens only within an oogonium; presumably, its wall is disintegrated by the latter. Before plasmogamy, both plasmalemmata are closely appressed. The fused protoplasts move into a short zygotial hypha which protudes from the oogonium. The thick-walled oospore is formed herein. It includes nearly all of the cytoplasm of the gametangia. Karyogamy takes place within the developing oospore. It is initiated by an interdigitation of microtubules radiating from the centrioles and by a close association of the latter. The observations are compared with those on other developmental stages of Lagenisma and with those on gametangia and oospores of other Oomycetes.
Determinate development of nodule roots in actinomycete-induced root nodules of Myrica gale
Authors: Torrey John G. , Callaham Dale
Published: May 2008

Young seedlings of Myrica gale L. grown in water culture were inoculated with a nodule suspension containing the effective actinomycete which induced root nodule formation. Nodule development was followed from initiation to nodule lobe formation and nodule root development using living materials and fixed nodules sectioned for light microscopy. After root hair infection and prenodule formation, three stages were observed: nodule lobe formation, a transition or arrested state, and nodule root development. The primary nodule lobe meristem originates endogenously and its formation involves pericycle, endodermis, and cortical cell derivatives. The lobe develops slowly to about 2 mm in length while the cortical cells are invaded by the actinomycete endophyte. After a period of arrest of variable duration, from a few days to several weeks, the nodule lobe meristem begins altered development, forming the elongate nodule root which undergoes slow but continuous growth to about 3- to 4-cm final length. New nodule lobe primordia are initiated endogenously at the base of existing nodules lobes, ultimately forming a cluster of nodule roots. Each nodule root, which elongates at about 0.1–1.0 mm per day, has a terminal apical meristem with reduced root cap formation and produces a modified root structure possessing an elaborate cortical intercellular space system and a reduced central cylinder. Nodule root growth is distinctive in that it shows strong negative geotropism. The endophyte is restricted to cortical cells of the nodule lobe and is totally absent from tissues of the nodule root. A probable role for nodule roots is to facilitate gas diffusion to the nitrogen-fixing endophyte site in the nodule lobe when nodules occur under conditions of low oxygen tension.
A caution against the use of polyvinylpyrrolidone in the extraction of plant glutamine synthetase
Authors: Sadler Ross , Shaw Michael
Published: May 2008

The successful extraction of glutamine synthetase from most plant tissues requires the removal of plant phenolics. Extraction in the presence of polyvinylpyrrolidone (PVP) was found to be unsatisfactory with all but one of the species tested. The effect varied in magnitude from a small loss of activity to complete inactivation of the enzyme. With flax cotyledons, no activity could be recovered using PVP. This failure resulted from (1) failure of polyvinylpyrrolidone to remove certain phenolics quantitatively during extraction and (2) inhibition of glutamine synthetase per se. Homogenization with small quantities of anion exchange resin usually gave satisfactory recovery, although this procedure removed less total phenolics than did PVP: it was necessary, however, to use the resin in much lower quantities than those previously prescribed to avoid adsorption of the enzyme itself.
The tip cells of antheridia of Polytrichum juniperinum
Authors: Hausmann M. K. , Paolillo Jr. D. J.
Published: May 2008

As in other mosses, the opening of an antheridium for sperm release in Polytrichum occurs with the swelling of thickened walls in the cells at the tip of the antheridium. Although the tip cells are distinguishable by their shape and slightly thicker walls at early stages of development, the addition of the wall layer that swells seems to occur only during the last few 10ths of a millimetre of antheridial elongation. Changes in the vacuome and the accumulation of cytoplasmic vesicles differentiate the cytoplasm of tip cells from that in other jacket cells, but dictyosomes are few or absent in tip cells. Autophagic activity occurs in the protoplasts of tip cells as they near maturity.
Experimental studies on leafy spurge (Euphorbia esula). IV. Cytohistological changes in the cotyledonary shoots following decapitation
Authors: Raju M. V. S. , Polowick Patricia L. , Marchuk W. N.
Published: May 2008

Cytological and histological studies were conducted on cotyledonary shoots of leafy spurge (Euphorbia esula L.) after the removal of the epicotyl. Growth owing to cell elongation was observed as early as 4 h in the proximal part of the shoot. Nuclear divisions were present in the distal part of the shoot and were not affected significantly by decapitation. They did not contribute to the early increase in length of the shoot. An increase of mitotic activity after 40 h and of shoot length after 72 h was observed; the latter was interpreted to be due to shoot xylem connections with the hypocotylary stele.
Nature des liaisons de l'ion calcium dans la paroi de Nitella flexilis
Authors: Wuytack R. , Gillet C.
Published: May 2008

Spectrophotometric titrations and conductivity measurements show that Nitella cell walls contain nonexchangeable Ca2+ cations which are probably chelated by COO− anions and donor groups such as OH (from polysaccharides) or NH (from proteins).A large part of these calcium ions are removed by acidification of the external medium. Subsequent augmentation of COO− groups increases the number of exchange sites available for H+ and K+ ions. The variation of the carboxylic groups concentration (α) is thus not fully accounted for by the pK of polygalacturonic acids but is also related to changes within the constitutive calcium of the cell wall.
Genera coelomycetum. XVI. Fibulocoela form-gen. nov., a coelomycete with basidiomycetous affinities
Authors: Raj T. R. Nag
Published: May 2008

Fibulocoela form-gen. nov., with F. indica form-sp. nov., is proposed to accommodate a coelomycetous anamorph of an unknown Basidiomycete from India. It is compared with Dacrymyces conglobatus Peck which is congeneric with Ditangium Karst. and a known anamorph of Craterocolla Bref.
Permeability studies on epidermal–hypodermal sleeves isolated from roots of Allium cepa (onion)
Authors: Clarkson D. T. , Robards A. W. , Sanderson J. , Peterson C. A.
Published: May 2008

Suberized sleeves of epidermal–hypodermal cells have been isolated by enzymic digestion from roots of onion. The average permeability coefficients of the sleeves to calcium and phosphate ions were 1.8 × 10−3 mm s−1 and 1 × 10−3 mm s−1. respectively, while the diffusive permeability coefficient for tritiated water was 2.6 × 10−3 mm s−1. If the cell walls in vivo have properties similar to those in the isolated sleeves, then it is concluded that diffusion of small molecules in the apoplast is subject to less resistance than diffusion across plasma membranes. Using a range of compounds differing in lipid solubility and molecular weight (MW), it was found that permeability was inversely related to MW. It is concluded that the suberized walls of the sleeves are microporous, having hydrophilic channels traversing them. The results accord with some published information on onion roots in vivo but contrast with the very low permeability of the hypodermis found in some other situations.
The relationship between steady-state transpiration rates and leaf water potential in cassava (Manihot esculenta cv. Llanera)
Authors: Ike I. F. , Thurtell G. W. , Stevenson K. R.
Published: May 2008

The relationship between leaf water potential (ψL) and transpiration rate (T) was investigated using indoor-grown cassava plants (Manihot esculenta Crantz cv. Llanera). Leaf water potentials were measured with in situ dew-point hygrometer and transpiration rates by gas exchange analysis technique.Regression analyses of the data showed that T was consistently linearly related to ψL (r2 = 0.94). This implies that the plant resistance to flow was constant and hence that an Ohm's Law analog is valid for the transpiration range studied. Extrapolated values of leaf water potential at zero transpiration were close to the osmotic potential of the nutrient solution. Calculated resistance values (slope of regression line for individual plants) varied between 2.90 and 3.05 bars dm2 h g−1 (1 bar = 100 kPa).
Differential effects of ozone on in vivo nitrate reduction in soybean cultivars. I. Response to exogenous sugars
Authors: Purvis Albert C.
Published: May 2008

Two cultivars of soybeans (Glycine max (L.) Merr.) differing widely in their resistance to ozone were exposed to 0.5 μl/ℓ ozone for 2 h in growth chambers. In vivo nitrate reduction was depressed by more than 50% in the primary leaves of Dare, the ozone-sensitive cultivar, but was not significantly altered in Hood, the ozone-resistant cultivar. Sucrose, up to 1.5% (w/v), added to excised seedlings of the Dare cultivar during exposure to ozone eliminated the ozone depression of in vivo nitrate reductase activity and also reduced foliar injury. Addition of two glycolytic intermediates, glyceraldehyde-3-phosphate and fructose-1,6-diphosphate, to the infiltration medium recovered some in vivo nitrate reduction in treated Dare leaves. The levels of extractable nitrate reductase and glyceraldehyde-3-phosphate dehydrogenase in the primary leaves of both cultivars were unaltered by ozone fumigations. These observations led to the conclusion that ozone depression of in vivo nitrate reduction is not due to ozone inactivation of nitrate reductase or of the enzymes coupling nitrate reduction to glycolysis, but may be caused by an inadequate supply of photosynthetic sugars. It was also noted that ozone depression of in vivo nitrate reduction only occurred with treatments which subsequently caused the development of visible foliar injury.
Water potential, water content, and net assimilation of some boreal forest mosses
Authors: Busby J. R. , Whitfield D. W. A.
Published: May 2008

Relationships between water content and water potential for Hylocomium splendens (Hedw.) B.S.G., Pleurozium schreberi (Brid.) Mitt., Ptilium crista-castrensis (Hedw.) De Not., and Tomenthypnnm nitens (Hedw.) Loeske, the last occurring in a distinctly different habitat from the first three, showed no hysteresis effect between wetting and drying curves and no appreciable differences among the species.Water contents near equilibrium over distilled water (water potential near zero) were 10–20% of saturation water contents, which suggested that after saturation by rainfall, considerable water loss can take place before water stress is experienced.The capacity for net assimilation decreased with depth in the moss canopy in all species, and the species showed similar decreases in net assimilation rates with decreasing water contents, from maximum rates at 3 to 6 g H2O g−1 dry weight to near or below zero rates around 0.4 g H2O g−1 dry weight.
Influence of various inorganic oxidants and organic compounds on mycelial growth and pycnidial production of Plenodomus meliloti in light and darkness
Authors: Zafar Saeed I. , Colotelo Nicholas
Published: May 2008

Numerous pycnidia of Plenodomus meliloti occur naturally on roots of legumes and cultures incubated in continuous light. Cultures incubated in darkness produced pycnidia only when various inorganic oxidants and phenolic compounds were incorporated into the culture medium, and even then they produced considerably fewer pycnidia than cultures incubated in continuous light did. The relationship between oxidizing compounds and pycnidia initiation is discussed briefly.
Vegetation recovery following pollution control at Trail, British Columbia
Authors: Archibold O. W.
Published: May 2008

Sulphur dioxide emissions from the heavy metal smelter at Trail, British Columbia, reached a peak in the late 1920's. By this date serious destruction of the natural vegetation had occurred. The recommendations of a tribunal set up to investigate the problem of air pollution were implemented in 1941. Hence air qualities suitable for the reestablishment of the vegetation have prevailed for some 30 years. Apart from a decrease in precipitation as one moves south through the study area, environmental conditions appear to be of minor importance in controlling recovery patterns with regrowth being limited principally by a shortage of viable propagules. The degree of destruction of the former vegetation cover is considered to be the major factor underlying the patterns of vegetation recovery. Much of the birch and aspen cover appears to have developed initially from remnant rootstocks, with coniferous regrowth restricted to areas where seed is available from mature trees which survived the fumigations.
Effects of Trichoderma on sexual reproduction of some species of Pythium and Phytophthora
Authors: Haskins R. H. , Gardner N. R.
Published: May 2008

Pythium and Phytophthora cultures were subjected to volatile products from cultures of several Trichoderma spp., as well as to killed mycelium and extracts therefrom. Oospores were produced by Pythium acanthicum and P. arrhenomanes and by one strain of each of the compatible heterothallic pairs of P. sylvaticum and P. catenulatum tested, only in the presence of a suitable sterol. The volatile products of the Trichoderma spp. tested had no apparent effect on oospore production. Direct contact with Trichoderma mycelium, or fat-solvent extracts of such mycelium, resulted in oospore production by P. acanthicum. Such oospore production was likely due to the presence of sterols in the Trichoderma. Similarly, with the compatible pairs of Phytophthora cinnamomi tested, oospores were produced by paired cultures or, in some cases, by the 'A2' strains alone, only in the presence of a suitable sterol, whether or not volatile products from Trichoderma cultures were provided to the growing organisms.
Patterns of photoassimilatory products in Pacific Rhodophyceae
Authors: Kremer Bruno P.
Published: May 2008

The typical patterns of 14C-labelled photoassimilatory products of 54 species of Pacific Rhodophyceae (representing 43 genera and six orders) have been compared. Certain heterosides, 2-O-D-glycerol-α-D-galactopyranoside (= floridoside) and 2-D-glycerate-α-D-mannopyranoside (= digeneaside) are the most strongly 14C-labelled accumulated low-molecular-weight carbohydrates of the species investigated. The occurrences of [14C]floridoside and [14C]digeneaside are mutually exclusive; while digeneaside has been found in representatives of the Ceramiales only, floridoside is recorded from species of all other rhodophycean orders. The results are discussed with emphasis on the chemotaxonomy of the Rhodophyceae.
Observations on hypnospores in Ulothrix zonata (Chlorophyceae)
Authors: Bullock Kenneth W.
Published: May 2008

The formation, structure, and development of hypnospores in Ulothrix zonata are described. Hypnospores are formed by cleavages similar to those in zoosporogenesis, but not all of the parent cell cytoplasm is included in the hypnospores. The hypnospores lack flagella or an eyespot and possess a thick, dense cell wall. This cell wall, the pyrenoid, and the nuclear morphology of hypnospores closely resemble those of vegetative cells. The number and size of the hypnospores produced varies within a filament from 2 to 4 large ones per cell to as many as 32 smaller ones per cell. The hypnospores are retained within the parent cell where they germinate into multicellular filaments whose subsequent growth causes a rupture in the parent cell wall. The new filaments are released and settle on the substrate to continue growth. The presence of hypnospores in U. zonata represents a unique form of asexual reproduction among members of the genus Ulothrix.
A revision of Corniculariella
Authors: DiCosmo Frank
Published: May 2008

A history of the names Corniculariella and Cornularia is presented. Cornularia is rejected as superfluous. Emended descriptions of Corniculariella, and C. abietis, its type species, are provided. A key is given for seven form-species: C. abietis, C. harpographoidea sp. nov., C. hystricina comb. nov., C. populi sp. nov., C. pseudotsugae comb. nov., C. spina comb. nov., and C. urceola comb. nov.Cornularia viburni is considered a nomen dubium, C. sphaeroidea is considered to belong in Heteropatella, and C. macrospora is considered to belong in Subulariella. A brief history of C. microscopica is presented. Some names in Cornularia led to revisions of other genera. Micropera was found to be a later homonym, and Foveostroma, nomen novum, is proposed to accommodate M. drupacearum, the type species, and also M. abietina. Emended descriptions for Gelatinosporium and G. betulinum, its type species, are presented.In the table, the transfers of form-species of Corniculariella can be followed by tracing the symbol representing each form-species. All illustrations are of type material.
Structure and localization of silica in the leaf and internodal epidermal system of the marsh grass Phragmites australis
Authors: Lau Elizabeth , Goldoftas Marcia , Baldwin Van D. , Dayanandan P. , Srinivasan Jyotsna , Kaufman Peter B.
Published: May 2008

Silica deposition sites in the epidermal system of shoots of Phragmites australis were analyzed by scanning electron microscopy and nondispersive X-ray microanalysis, as well as by acid digestion of leaf and stem tissue. In the lamina adaxial and abaxial epidermal layers, silica is concentrated in the stomatal guard cells, silica cells, and outer tangential walls of long epidermal cells, but little silica occurs in the trichomes. In the sheath, both epidermal surfaces are highly silicified, in effect, providing a 'silicified jacket' around the internode. Pulvini of both the sheath and internode possess less silica than nonpulvinar regions above them. The silica in Phragmites is viewed as providing support for the shoot system (particularly in the sheaths), protecting the plant against predators and water loss and, possibly, allowing more light to pass through the epidermal system via the silica cells to the photosynthetic mesophyll tissue that lies below the epidermal system in both lamina and sheath.
Nomenclatural changes in the Asteraceae of British Columbia. I. Senecioneae
Authors: Douglas George W. , Ruyle-Douglas Gloria
Published: May 2008

New combinations or changes in status are given for 12 taxa in the genera Arnica, Luina, and Senecio of the Senecioneae (Asteraceae) of British Columbia, Canada.
Stalk length as a taxonomic criterion for Phytophthora palmivora isolates from cacao
Authors: Kaosiri Thawee , Zentmyer G. A. , Erwin D. C.
Published: May 2008

Eighty cacao isolates of Phytophthora from Africa, the Americas, the Pacific, and Southeast Asia, originally designated as Phytophthora palmivora, were studied. The sporangial stalk or pedicel length of various isolates was significantly different. These isolates were separated into four groups on the basis of the stalk or pedicel length. The differences in characteristics among the four groups and their relationships to the morphological forms (MF) of P. palmivora are described.One group of isolates, designated as MF 1, had short and thick sporangial stalks averaging less than 5 μm in length. Isolates in a second group corresponded to MF 3, with rather thin sporangial stalks, intermediate in length, averaging 5–15 μm. Sporangial stalks of a third group of isolates, designated as MF 4, had unusual and characteristically long stalks with an average length of more than 15 μm. A fourth group of isolates had noncaducous sporangia. Similarities between MF 4 isolates and the type culture of P. capsici are noted.The stability of sporangial stalk length under several different environmental conditions makes this character very useful as a taxonomic criterion for identifying isolates in the P. palmivora complex.
Early effects of phytotoxic burdens of cadmium, cobalt, nickel, and zinc in white beans
Authors: Rauser Wilfried E.
Published: May 2008

The effectiveness of excess cadmium, cobalt, nickel, and zinc in eliciting similar early responses was studied in white beans. Each metal caused the appearance of a red–brown discoloration first in the veins of unifoliate leaves and later in petioles and stems. Cadmium, nickel, and zinc did so within 1 day, cobalt within 4 days. The effectiveness of the metals in inducing visual symptoms and in decreasing dry matter production were in the order [Formula: see text]. Within 1 day of adding excess metal, each caused the unifoliate leaves to orient themselves towards the vertical from the normal horizontal. Each metal caused premature leaf closure within the normal nyctinastic cycle.Excess cobalt, nickel, and zinc all caused abnormal starch accumulations in unifoliate leaves within 2–3 days. These metals also caused a major shift towards relatively apolar soluble phenolic components in leaves but not in roots. Cadmium, besides being most toxic, did not cause starch accumulation or a shift in the complement of soluble phenolics.
Distribution and abundance of phytoplankton in 153 lakes, rivers, and pools in the Northwest Territories
Authors: Moore James W.
Published: May 2008

A survey of phytoplankton in lakes, rivers, and temporary pools in the Northwest Territories was conducted during 1975, 1976, and 1977. Dinobryon bavaricum was the most abundant and widespread species, occurring in almost all collections. It was followed in order of decreasing importance by D. cylindricum, D. sociale, and D. divergens. The predominant diatoms were Cyclotella glomerata and C. ocellata. Both species reached greatest abundance in lakes and rivers in the high arctic and were completely absent from temporary pools. Although Asterionella formosa, Diatoma tenue var. elongatum, and Melosira islandica were common in Great Slave Lake and other southern lakes, they were either rare or absent north of latitude 65°. The Chlorophyta, particularly Ankistrodesmus falcatus and Scenedesmus spp., occurred in almost all collections but always in low numbers. Planktonic Cyanophyta (primarily Oscillatoria limnetica) were normally rare.
Morphology, growth in culture, and conidium formation in Poronia pileiformis
Authors: Paden J. W.
Published: May 2008

Poronia pileiformis is described and illustrated. Cultures were obtained from germinated ascospores. On SME agar, stromatal stipes developed but did not produce heads or perithecia. Conidia were produced at the apices of the young stipes only. The conidia were holoblastic, borne on sympodial conidiogenous cells.
Influence of the carbon/nitrogen relationship on the degree of autolysis of Aspergillus niger
Authors: Lahoz R. , Reyes Fuensanta , Gómez Pilar , Jimeno Luis
Published: May 2008

The effect of the initial exogenous carbon/nitrogen ratio on the degree of autolysis in cultures of Aspergillus niger has been studied. For C/N ratios between 0.75:1 and 100:1 (grams per gram), the degree of autolysis (α) continuously decreased from an average value of 72.5 to 16.0%, respectively. There was a linear correlation between the [Formula: see text] ratio and the percentage degree of autolysis (α%) represented by the regression line [Formula: see text]. It can be concluded that the degree of autolysis is profoundly influenced by the C/N ratio initially present in the culture medium.
Polymorphisms for lesion type, fungicide tolerance, and mating capacity in Cochliobolus carbonum isolates pathogenic to corn
Authors: Leonard K. J.
Published: May 2008

Of 189 isolates of Cochliobolus carbonum from the southeastern and midwestern United States, 3 were race 1, 133 were race 2, and 53 were race 3. The rarity of race 1 which produces a host-specific toxin suggests that, in the absence of host plants sensitive to the toxin, stabilizing selection favors genotypes lacking the gene for toxin production. Race 3 which causes long, linear lesions on corn leaves was predominant among isolates from the Mountains of North Carolina and adjacent states, but was rare in the Piedmont and Coastal Plain where race 2 predominated. Race 2 which causes small round or oval lesions was the only race found in the midwestern United States.Polymorphisms for tolerance of cycloheximide, carboxin, and cadmium were found in race 2 but not in race 3. Only 17% of race 3 isolates had the ability to form perithecia, whereas 67% of race 2 isolates formed perithecia in compatible matings. These differences in polymorphism in addition to the quantitatively inherited difference in lesion type between race 2 and race 3 indicate that there has been little or no gene exchange between races 2 and 3 in nature even though fertile crosses can be obtained readily in the laboratory.
Effect of either 2,4-dichlorophenoxyacetic acid or kinetin on production and composition of various fractions from extracellular polysaccharides produced by cotyledon cell suspension cultures of bush bean (Phaseolus vulgaris cv. Contender)
Authors: Mante S. , Boll W. G.
Published: May 2008

Cotyledon cell suspension cultures of bush bean required 2, 4-dichlorophenoxyacetic acid (2,4-D) for growth. Kinetin was not essential but was required for optimum growth. Both of the regulators were required for optimum production of extracellular polysaccharide (EP).The two regulators had different effects upon the production of three polysaccharide fractions (two pectins and a neutral polysaccharide) isolated from the EP at various stages of the culture cycle.The neutral sugar composition of the pectin fractions from all treatments, including regulator treatments, showed considerable fluctuation during the culture cycle and could be changed markedly by regulator treatments. Changes in composition of the neutral polysaccharide were slight. As a consequence of these results it is now possible to obtain cells differing in the nature of the systems synthesizing, or controlling the synthesis of, the polysaccharides.
An extensive subfossil deposit of the arctic moss Aplodon wormskioldii
Authors: Brassard Guy R. , Blake Jr. Weston
Published: May 2008

A 2.6-m-thick subfossil peat deposit, composed entirely of the arctic moss Aplodon wormskioldii, is described from the Carey Islands, northwestern Greenland (76°44′ N, 73°13′ W). Radiocarbon dates indicate that the peat began forming approximately 6500 years ago and stopped forming some 4500 to 4000 years ago; thus, its growth coincided with the postglacial warm period (Hypsithermal interval). The present-day habitat of A. wormskioldii, on dung or otherwise enriched substrates, is difficult to reconcile with its persistence and abundance at a specific site in the high arctic for over two millenia.
Asci of the Pezizales. II. The apical apparatus of representatives in the Otidea–Aleuria complex
Authors: Samuelson Don A.
Published: May 2008

Morphological, developmental, and cytochemical studies were made on the apical apparatus of nine members of the families Otideaceae and Aleuriaceae, referred to as the Otidea–Aleuria complex, and Ascozonus woolhopensis. Special attention was paid to peculiar structures and the time of their appearance during ascosporogenesis. Subopercular rings were found in seven species. First appearance of the ring occurs at different stages of ascal development for different species. Formation of the ring generally marks the initiation of the development of the apical apparatus. For the most part, those species which have thick, 700–1000 nm, lateral walls possess less conspicuous subopercular rings than those species which have thin, 300–400 nm, lateral walls. Distinct zones or lines of dehiscence were not detected in any species. The apical apparatus of A. woolhopensis resembles that of Anthracobia melaloma. The apical apparatus of individual species is variable and can be useful in helping to determine taxonomic affinities.
Morphology and morphogenesis of synnemata of Ceratocystis ulmi
Authors: Hiratsuka Yasuyuki , Takai Shozo
Published: May 2008

Morphology and morphogenesis of synnemata of Ceratocystis ulmi were observed under a scanning electron microscope and a transmission electron microscope. Synnematal development in C. ulmi can be divided into four stages: (1) synnema initial formation, (2) stalk development, (3) conidiophore formation, and (4) conidium production. Observations on each stage of development are described and illustrated.
Chromosomal proteins of conifers. 2. Tissue specificity of the chromosomal proteins of jack pine (Pinus banksiana)
Authors: Pitel J. A. , Durzan D. J.
Published: May 2008

Histones and nonhistone chromosomal proteins (NHCP) were extracted from the dry diploid embryo (sporophyte) and the haploid female gametophyte (n = 12) of the same seeds. Electrophoretic properties of proteins were compared on polyacrylamide gels. In dry seeds, ploidyspecific differences in chromosomal proteins were not detected with respect to number of proteins or their electrophoretic properties. By contrast, in germinating seeds, root and shoot tissues of 14-day-old jack pine seedlings revealed tissue-specific NHCP. Changes in histone composition, except for the F1 fractions, were insignificant.
Seasonal changes in mesophyll ultrastructure of needles of Norway spruce (Picea abies)
Authors: Soikkeli Sirkka
Published: May 2008

Seasonal changes in the ultrastructure of the mesophyll of needles of Norway spruce are described. During the growing season, the tannin is in the form of a ribbon along the margin of the vacuole or in the form of small, more or less scattered particles. The cytoplasm is dark and its organelles are along the cell wall; only the chloroplasts with large starch grains and the nucleus can be clearly resolved. During and after September, the cytoplasm is very netlike, all of the cytoplasmic organelles clump together, the amount of lipid droplets increases, and ribosomes are clearly visible. The tannin is in the form of rather large granules and it increases over its growing-season amount. The shape of chloroplasts changes. Chloroplasts lose their starch and the stroma becomes sparsely granular and rich in ribosomes. This structure is maintained throughout the winter. During spring activation, the cell structure is reorganized and reassumes the condition typical of the growing season. At this time, the needles have some collapsed cells and cells in which some chloroplasts are not quite intact. The injuries were probably caused by weather conditions (a warm period in March followed by a frost).
Influence de l'aluminium sur la sélectivité racinaire de plantes calcicole et calcifuge
Authors: Guerrier Gilles
Published: May 2008

The study of the influence of an increasing quantity of aluminium on adsorption and uptake of mineral nutrients in the horsebean (Vicia faba minor L., calcicole) and the yellow lupine (Lupinus luteus L., calcifuge) shows that selectivity in adsorption occurs only for the calcicole species.The decrease of cation exchange capacity of roots with increments in the quantity of aluminium would represent the toxicity of this cation; aluminium would transform its own exchange sites into an inactivated form: This structure on the root surface would allow a diffuse absorption process of this element in roots.
Cellulase activity during the growth of Achlya bisexualis on glucose, cellulose, and selected polysaccharides
Authors: Miele W. H. , Linkins A. E.
Published: May 2008

The antheridial strain of the dioecious water mold Achlya bisexualis was grown in chemically defined media using glucose, cellobiose, and selected polysaccharides as carbon sources. Growth and cellulase levels were measured with media containing glucose, cellobiose, and cellulose. Evaluation of cellulase activity in the medium by viscometric and reducing sugar generation assays suggests that cellulase plays a significant role in degrading cellulose for uptake and catabolism by A. bisexualis. Cellulase in glucose-grown cultures exists as a soluble extracellular enzyme complex, while in cellulose-grown cultures much of the enzyme is absorbed to the cellulose. Elution of the cellulose substrate after 96 h growth with NaCl-fortified buffer releases absorbed cellulase in a soluble form. The absorption of cellulase to the substrate and possibly the cell walls of A. bisexualis could account for the rapid loss in dry weight of A. bisexualis during culture on cellulose in a closed system. Scanning electron microscopic (SEM) examination of the walls of A. bisexualis shows disruption in cellulose cultures, which is not evident for glucose-or cellobiose-grown hyphae. Transmission electron microscopic (TEM) photomicrographs show a significant reduction in the wall thickness of cellulose-grown hyphae as compared with glucose-grown samples. This evidence suggests that the enzyme(s) produced during growth on cellulose is (are) capable of binding as an active hydrolase to walls of A. bisexualis or to the cellulosic substrate.
Isolation and staining of wheat transfer cells
Authors: Zee S.-Y.
Published: May 2008

Xylem and phloem transfer cells in the vegetative nodes of wheat, fixed in a mixture of 3% ammonium dichromate + 3% potassium dichromate and 20% formalin (1:1), could be easily separated from the nodal tissue using a mixture of 2% chromium trioxide + 8% H2SO4 + 3% HNO3 solution. After maceration and staining (with either acidic or basic dyes), the well organized protoplast and the weakly birefringent walls of the transfer cells could be seen clearly.
Ultrastructural studies on Orbilia luteorubella (Discomycetes)
Authors: Benny Gerald L. , Samuelson Don A. , Kimbrough James W.
Published: May 2008

Transmission electron microscopic observations made on the ascus tip of Orbilia luteorubella showed that it is truncate and that the outer ascus wall is relatively thicker at the shoulders than on the top or sides. There is no demonstrable discharge mechanism in the ascal apex of this fungus comparable with that found in the ascus tip of other supposedly related inoperculate Discomycetes, including Mollisia cinerea.Ascospores of O. luteorubella contain a single, electron-opaque spore body that appears to evolve from a mitochondrion that is attached, at one end, to the inner wall of the spore apiculus. The function of the spore body is unknown.A blue-green alga, probably of the genus Anacystis, is associated with this and at least one other Orbilia species. Since these Orbilia species are here shown to be lichenized and they do not have an ascal pore discharge mechanism, the transfer of these fungi from the Helotiales is proposed. They can probably best be treated as lichens of uncertain affinities, perhaps related to those members of Lecanorales with iodine-negative asci.
Numerical taxonomy of certain genera of Fungi Imperfecti and Ascomycotina
Authors: Dabinett Patrick E. , Wellman Angela M.
Published: May 2008

Various clustering and ordination techniques are used on data collected from 88 cultures of Fungi Imperfecti and imperfect states of Ascomycotina to produce classifications. The data consist of 98 characters representing the morphology, conidium ontogeny, and physiology of the cultures. Although 23 genera are represented, emphasis is placed on Graphium sensu lato and Ceratocystis to which half the cultures belong. Seven groups which cluster consistently in all the techniques used are recognized, groups A to G. Group A contains species which have the annellidic type of conidiation, namely Trichurus. Scopulariopsis, Doratomyces, and Microascus. Group B contains the phialidic Chalara-type Ceratocystis species. Group C is characterized by the sympodial type of conidiation of the Sporothrix type and contains species from Petriella and Sporocybe. Group D contains an assortment of species which display the typical phialidic conidiogeny. Group E contains species from Ceratocystis and Graphium sensu lato which have holoblastic conidia with conidiogenous cells of the ramoconidium type. Group F is a loose cluster of species characterized by sympodial conidiation and contains species from Graphium sensu lato, Ceratocystis, and Verticicladiella. Group G contains species of Periconia which produce large conidia polyblastically. This numerical classification provides new evidence to support the classifications based on conidium ontogeny.
Location of reserves of mineral elements in seed protein bodies: macadamia nut, walnut, and hazel nut
Authors: Lott John N. A. , Buttrose Mark S.
Published: May 2008

This paper presents the results of thin-section, freeze-fracture, energy dispersive x-ray (EDX) analysis, and chemical analysis studies of cotyledon tissue from dry seeds of macadamia nut (Macadamia integrifolia), walnut (Juglans regia), and hazel nut (Corylus avellana). Studies concentrated on mineral elements in the storage protein bodies. Protein bodies of macadamia nut contained no protein crystalloids but did contain some globoid crystals. Aqueous fixation of macadamia tissue appeared to result in a rapid solubilization of proteinaceous matrix material. EDX analysis of macadamia nut globoid crystals revealed the presence of P, K, and Mg in most cases but the occasional crystal was very high in calcium. Walnut protein bodies often contained many large protein crystalloids. Globoid crystals were present between the protein crystalloids and in the proteinaceous matrix. EDX analysis indicated the presence of P, K, and Mg as the main elements in walnut globoid crystals. Hazel nut protein bodies contained one or more small protein crystalloids, globoid crystals of various sizes, and proteinaceous matrix. Some protein bodies contained druse crystals. EDX analysis showed that the druse crystals were rich in calcium and thus are presumably calcium oxalate. EDX analysis of globoid crystals revealed the presence of elements consistent with the phytin-rich nature of globoid crystals. Variations in globoid crystal composition are discussed.
Patterns of lichen photosynthesis and respiration following prolonged frozen storage
Authors: Larson Douglas W.
Published: May 2008

The effect of prolonged frozen storage on patterns of photosynthesis and respiration in the lichen Alectoria ochroleuca (Hoffm.) Massal. has been examined. The results indicate that this plant not only survives long-term exposure to low temperatures but also that its basic photosynthetic and respiratory responses to temperature, light intensity, and thallus moisture content are altered very little by long-term storage at −60 °C. This maintenance not only of absolute viability but also of the more subtle patterns of physiological activity suggests that such storage may be used to hold lichen material for use in multivariate experimental systems which require replicates having identical field pretreatment.
Stimulation of fungal spore germination by volatiles from aged seeds
Authors: Harman G. E. , Nedrow B. , Nash G.
Published: May 2008

Alaska pea seeds were stored asceptically or with inoculum of Aspergillus ruber, a pathogenic storage fungus, under conditions which induce rapid seed deterioration and permit infection of seeds by A. ruber (30 °C and 92% relative humidity). Volatiles from germinating aged seeds stimulated germination of conidiospores of Fusarium solani f. sp. pisi and Alternaria alternata and chlamydospores of F. solani f. sp. pisi, all in soil-induced stasis, much more than volatiles from unaged seeds. Volatiles from A. ruber - infected seeds were more stimulatory than from comparably aged noninfected seeds when planted in sand, but this effect was not seen when the seeds were planted in soil. Oospores of Pythium ultimum were not stimulated to germinate by volatiles from any seeds. Aged and infected seeds produced up to 24 times more carbonyl compounds than unaged seeds, presumably as a consequence of lipid peroxidation.
Chromosome numbers of some tropical African grasses from western Zaïre
Authors: Dujardin Michel
Published: May 2008

Chromosome numbers are reported for 135 collections of grasses from western Zaïre representing 53 genera and 93 species. First chromosome counts are reported for the genera Puelia, Heteranthoecia, and Vossia and for the following 29 species: Puelia ciliata, Puelia olyriformis, Aristida dewildemanii, Eragrostis barteri, Eragrostis squamata, Eragrostis thollonii, Sporobolus subtilis, Perotis vaginata, Loudetia demeusei, Loudetia vanderystii, Trichopteryx fruticulosa, Heteranthoecia guineensis, Isachne kiyalaensis, Antephora cristata, Digitaria acuminutissima, Panicum baumannii, Panicum dregeanum, Panicum nervatum, Pennisetum nodiflorum, Sacciolepis rigens, Setaria restioides, Andropogon festuciformis, Elionurus brazzae, Elionunis hensii, Eriochrysis brachypogon, Hyparrhenia familiaris, Jardinea gabonensis, Schizachyrium pulchellum, and Vossia cuspidata. Counts differing from previous records were obtained for these nine species: Eragrostis superba, Ctenium newtonii, Brachiaria mutica, Echinochloa stagnina, Ottochloa nodosa, Setaria anceps, Andropogon huillensis, Jardinea congoensis, and Trachypogon spicatus.
A comparison of systematic errors between the Richards and Hammel methods of measuring tissue – water relations parameters
Authors: Tyree M. T. , MacGregor M. E. , Petrov A. , Upenieks M. I.
Published: May 2008

The pressure bomb is being used to a much greater extent to measure some tissue – water relations parameters such as osmotic pressure, turgor pressure, and cell wall elasticity. Recently, Richards has developed a faster pressure-bomb method of obtaining these and other parameters than the method used by Hammel and modified by us. In this paper, we compare the two methods and conclude that Richards’ method should not be used when accuracy is deemed important. The Richards method usually overestimates osmotic pressure by 0.2 MPa (= 2 bars) and sometimes by 0.8 MPa (= 8 bars).
Relation of weather variables and host factors to incidence of airborne spores of Bipolaris sorokiniana
Authors: Couture L. , Sutton J. C.
Published: May 2008

Seasonal and daily incidence of airborne spores of Bipolaris sorokiniana were studied in barley field plots in relation to crop development, disease severity, and weather variables. Sporulation was observed only on dead or senescent barley. The incidence of airborne spores before 8–11 July was low because spore-bearing barley foliage was scarce and weather factors were often unfavourable for sporulation. Large numbers of spores encountered after 8–11 July coincided with rapid disease progress and repeated occurrence of persistent leaf wetness and high temperatures. Cumulative spore counts showed that few spores were dispersed sufficiently early in the growing season to serve as inoculum in the epidemics. Numbers of airborne spores were low at night, but increased abruptly after dawn to peak concentrations during 0900 to 1700 hours. Circumstantial evidence indicated that spore production was promoted by persistent leaf-surface wetness, high relative humidity (RH), and high temperatures (> 15 °C), but restricted by cool temperatures. Correlative studies showed that spore release was caused by rapidly declining RH and wind. Spores were dispersed mostly when the leaves were dry and the numbers dispersed correlated very strongly with wind speed. Few spores were dispersed when leaves were wet and RH high.
The effects of wetting and drying on the subsequent germination of Rumex crispus
Authors: Vincent Elizabeth M. , Cavers Paul B.
Published: May 2008

A period of 1 to 3 days imbibition followed by drying altered the subsequent germination responses of seeds of Rumex crispus L. When the imbibition took place under alternating light and temperature conditions subsequent germination was faster and more complete. In contrast, when the seeds imbibed at a constant temperature and in nearly continuous darkness subsequent germination was delayed and less complete. Subsidiary tests demonstrated that (a) within a 24-h drying period, the seeds lost virtually all water imbibed over 1 to 3 days; (b) a 3-day imbibition pretreatment was followed by faster, more complete germination in a 0.25 M mannitol solution; (c) the duration of the drying period (up to 29 days) had little effect on the outcome; and (d) seeds pretreated for 1 to 3 days under an alternating light and tempèrature regime germinated more rapidly than untreated seeds when sown in soil in a greenhouse. These results help to explain why seedlings of R. crispas appear rapidly each summer following a drought-ending downpour, whereas seeds of the same species buried deep in the soil acquire a secondary dormancy and may remain viable for up to 80 years.
A survey of angiosperms in Nova Scotia for rhizosphere nitrogenase (acetylene-reduction) activity
Authors: Smith D. , Patriquin D. G.
Published: May 2008

Excised root samples from 901 plants, representing 130 species of nonnodulated angiosperms largely in upland, pioneering habitats, were assayed for nitrogenase activity by the acetylene-reduction technique after overnight preincubation of the samples under low pO2. Most samples and most species exhibited very low excised root acetylene-reducing activities, but for 19 species, maximum values were greater than 50 nmol C2H4∙g−1∙h−1. In situ C2H2 assays, conducted on 10 species which had exhibited maximum excised root activities greater than 10 nmol C2H4∙g−1∙h−1, indicated average belowground N2-fixation rates of 3 to 92 g N∙ha−1∙day−1 and maxima greater than 100 g N∙ha−1∙day−1 for 3 of the 10 species. The highest values were for grasses characteristic of poorly drained soils and for some dicotyledonous weeds. It is concluded that the potential of temperate-zone angiosperms for nitrogenase activity by 'associative symbioses' approaches that of tropical forage grasses.