bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of basidium and basidiospore development in three species of the fungus Exobasidium
Authors: Mims Charles W. , Richardson Elizabeth A. , Roberson Robert W.
Published: September 2008

The sequence of events occurring within basidia of Exobasidium was shown to be quite different from that previously described in one-celled holobasidia. Karyogamy was found to occur in thin-walled hyphal compartments or probasidia comprising part of a stroma-like system within the intercellular leaf spaces. Meiosis also began in these compartments but was not completed until after the nucleus had migrated into the large, prominent metabasidium that became exposed on the abaxial leaf surface. Following sterigmatal development and a postmeiotic mitotic division, usually four to seven basidiospores developed per basidium. Each spore possessed a hilar appendage on its abaxial side, but neither a hilar appendage body nor a hilar droplet was observed. The thin basidiospore wall was continuous with that of its sterigma. Development of a hilar septum delimited the spore from its sterigma. Detached basidiospores of E. vaccinii and E. japonicum became two celled following mitosis and development of a near-median transverse septum. Basidiospores of E. camelliae var. gracilis usually developed three transverse septa. Based on our observations Exobasidium should be placed in the Teliomycetes.
New species of Cercospora and Cercosporidium from Uttar Pradesh, India
Authors: Gupta Kamal BK , Verma R K
Published: September 2008

This paper deals with the description and illustration of Cercospora madhauliensis sp.nov. and Cercosporidium barringtoniae-acutangulae sp.nov. They cause leaf spot diseases on Tinospora cordifolia Miers and Barringtonia acutangula Gertn. respectively.
An unusual subterranean occurrence of fossil fungal sclerotia
Authors: Malloch D. , Grenville D. , Hubart J.-M.
Published: September 2008

Black deposits occurring as parallel superficial strata in the Ramioul Cave, Belgium, are demonstrated to be composed mainly of fungal sclerotia. The deposits date from 7500 to 2750 years BP and appear to have been formed during several periods of flooding. Although fungal sclerotia are sometimes known to float in lakes and streams, the very heavy deposition of these appears to be unusual and to be the result of special conditions in the cave.
Turing's model and branching tip growth: relation of time and spatial scales in morphogenesis, with application to Micrasterias
Authors: Lacalli Thurston C. , Harrison Lionel G.
Published: September 2008

Morphogenesis following cell division in Micrasterias rotata is by outgrowth and repeated branching of a series of semicell lobes. Though successive branching events are qualitatively similar, they display changes in time and space scales, and these can be quantitated with the aid of autoradiographic patterns of labelled wall precursors that appear late in morphogenesis but which seem to represent its history. This enables us to consider branching as the conversion of a single centre of growth activity into two and to attempt to locate these centres precisely, in terms of both position and time of establishment. Temporal and spatial scales both decrease, by 75%, through a sequence of five branching events, in linear functional relationship to each other. This correlation points toward kinetic control of morphogenesis, i.e., the involvement of something like a reaction–diffusion mechanism. We analyse this possibility in terms of available reaction–diffusion theory to show how, after various simplifying assumptions, and if the time and space scales of branch formation are known, an effective diffusivity, [Formula: see text], for the patterning mechanism can be estimated. For M. rotata we obtain orders of magnitude: [Formula: see text], with an upper limit on the diffusivity of the faster diffusing of the two morphogenetic substances in the mechanism of ca. 1 × 10−7 cm2/s. These values implicate the cell membrane as the most probable site of pattern formation.
Effects of selection by host cultivars on populations of Ustilago hordei
Authors: Christ B. J. , Person C. O.
Published: September 2008

The barley – Ustilago hordei (Pers.) Lagerh. system was examined in selection experiments. Three populations were formed with teliospores originating from 15 different dikaryons (5 dikaryons per population). The teliospores were heterozygous for a gene governing virulence to the barley cultivar Trebi. Each population was subdivided such that one subpopulation was selected on 'Trebi' and the other was simultaneously selected on 'Odessa', partially resistant and susceptible cultivars, respectively. Changes in the virulence allele frequency were monitored during each generation of selection for each population. There were no major changes in percentage of smutted plants that could be attributed to the cultivar on which selection took place. Increases of the virulent phenotype were observed for all populations regardless of cultivar. Whether these changes were the result of changes of allele frequency or other factors is not known.
The Xerulaceae (Basidiomycetes), a family with sarcodimitic tissues
Authors: Redhead S. A.
Published: September 2008

The taxonomic value of the presence of sarcodimitic tissues and derived tissues in the agarics was investigated. Basidiomata of only 15 genera of 153 agaric and bolete genera surveyed had sarcodimitic tissues. The family, the Xerulaceae, is recognized for these 15 lamellate, sarcodimitic genera along with 1 genus exhibiting modified tissues and 2 closely allied genera apparently lacking sarcodimitic tissues. It is hypothesized that they evolved convergently and then in parallel with members of the Tricholomataceae. Taxonomic difficulties arising from the apparent loss of the sarcodimitic tissues in evolutionarily advanced taxa within the Xerulaceae, such as Mycena and Xerula, are discussed. Antibiotics with an (E)-β-methoxyacrylate moiety (strobilurins, oudemansin), which are potentially useful against cancer, with one possible exception are found only in a number of genera with sarcodimitic or derived tissues currently assigned to the Xerulaceae. Two new combinations are proposed: Cystolepiota pusillomyces (Peck) comb.nov. and Floccularia albolanaripes (Atk.) comb.nov.
Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust
Authors: Shain L. , Järlfors U.
Published: September 2008

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.
Modern pollen spectra from lakes in arctic western Canada
Authors: Ritchie J. C. , Hadden K. A. , Gajewski K.
Published: September 2008

Fifty-four samples of modern sediment from Banks Island and the Melville–Horton region of the Northwest Territories illustrate the major features of pollen deposition from the high to low arctic. Modern pollen deposition in the high arctic of Banks Island is characterized by up to 14% windblown tree pollen. Indicator taxa of the high and mid arctic include Oxyria (<5–23%), Saxifragaceae, Saxifraga oppositifolia, and Cruciferae (all up to 8%) and Dryas (up to 3%). Arboreal pollen increases to 60% in low-arctic and subarctic samples. Pollen concentration decreases from between 3 500 and 20 000 in the low arctic to less than 5 000 grains/cm3 in the high and mid arctic. Pollen spectra from the Late Glacial of northwestern Canada differ from those of the modern high and mid arctic not only by the absence of trees and shrubs but also in the relative proportions of Artemisia and of such indicator taxa as Oxyria and Saxifragaceae.
Multivariate variation within and between open-pollinated families of Douglas-fir (Pseudotsuga menziesii)
Authors: Scagel R. K. , El-Kassaby Y. A. , Maze J.
Published: September 2008

The morphological variation of seedlings from a single population of Pseudotsuga menziesii was examined and related to their maternal parentage (41 families) and speed of germination (selection) during the course of a common garden experiment. The largest source of variation among seedlings was attributed to within-family variation. Furthermore, within-family variable intercorrelations differed from family to family, suggesting that intrinsic causal factors are important to the generation and organization of variation. Pooled within-family variation was explored and shown to be related to the between-family variation. These results suggest that developmental and historical factors cannot be ignored in the interpretation and exploitation of sources of variation. Such considerations identify limitations to Neo-Darwinian explanations and suggest reappraisal of progeny trials with respect to these issues. The results also pose limitations to our interpretations of genetic similarity on the basis of multivariate morphological data.
Development of Alnus japonica root nodules after inoculation with Frankia strain HFPArI3
Authors: Burgess D. , Peterson R. L.
Published: September 2008

The ontogeny and structure of nodules on an exotic tree species, Alnus japonica (Thunb.) Steud. were studied for up to 3 months after inoculation of seedlings with a North American Frankia strain, HFPArI3. Nodules developed with Frankia growth first restricted to one side of the developing vascular cylinder. Nodules became multilobed, developed a complex network of vascular cylinders, and infected cortical cells organized in a concentric ring around each vascular cylinder. Each nodule lobe showed a zonation from the meristem basipetally. Cortical cells adjacent to the meristem contained hyphae, while those distal to this zone developed hyphae and endophytic vesicles. Staining for suberin induced fluorescence of root hairs, the endodermal Casparian strip, endophytic vesicle clusters, and periderm. Staining for callose resulted in fluorescence of the encapsulation material at one stage of Frankia development. Infected cells had few, small starch grains, while uninfected cells had several, large starch grains. The adjacent pericycle was multilayered. Its cells, viewed with the transmission electron microscope, had lobed nuclei, small vacuoles, many mitochondria, and dense plastids containing small starch grains.
Effect of nutrient conditions on root nodule development in Alnus japonica
Authors: Burgess D. , Peterson R. L.
Published: September 2008

The morphology and structure of nodules on the exotic tree alder Alnus japonica (Thunb.) Steud. inoculated with the North American Frankia strain HFPArI3 were examined under different nutrient conditions. Seedlings were subjected to a nitrogen, phosphorus, or iron stress treatment using the Ingestad nutrient addition technique which generally produced a decrease in the length of healthy endophytic vesicle cluster zones. External nodule morphology varied according to treatment, with thicker nodules developing under "good" nutrient conditions. Nodule meristems showed apparent apical dominance under conditions of nutrient stress. Increased additions of inorganic nitrogen reduced the levels of nitrogen fixation and increased cortical cell size but reduced the numbers of endopytic vesicles per unit area. High nitrogen fixation levels were accompanied by the formation of numerous large mitochondria in nodule pericycle cells.
Ultrastructure and ontogeny of hair filaments in the subtidal saccate alga Hydroclathrus clathratus (Phaeophyta, Scytosiphonales)
Authors: Oates Brian R. , Cole Kathleen M.
Published: September 2008

Hair filaments found in pits scattered over the surface of the saccate brown alga Hydroclathrus clathratus were examined ultrastructurally. Cells near the base of filaments are short and metabolically very active, containing many mitochondria, ribosomes, rough endoplasmic reticulum, and dictyosomes but no vacuoles. Numerous plasmodesmata connect cells of the filaments. The more distal cells elongate during development of the pits. As elongation begins, dictyosome activity dominates and vacuoles appear. Very elongate cells are filled almost exclusively by a vacuole with a narrow band of cytoplasm at the cell periphery. Chloroplasts are found only in basal cells of short filaments. Other cells near the filament base contain plastosomes, small spherical bodies derived from chloroplasts by a series of divisions. While morphologically distinct, plastosomes have retained many features of brown algal chloroplasts. They are bound by the chloroplast envelope and chloroplast endoplasmic reticulum and contain a ring genophore. The thylakoid system varies in that more than three thylakoids are usually loosely associated in the peripheral band and the interior bands are absent in more mature plastosomes.
Occurrence of a microconidial state in Cylindrocladium heptaseptatum
Authors: El-Gholl N. E. , Chase A. R. , Alfieri Jr. S. A. , Schoulties C. L.
Published: September 2008

A microconidial state of Cylindrocladium heptaseptatum is described from Rumohra adiantiformis in Florida. Microconidia are shown to be a propagative form of C. heptaseptatum.
Adaptation au NaCl de Lycopersicon esculentum : étude comparative des cultures de cals ou de parties terminales de tiges
Authors: Bourgeais P. , Guerrier G. , Strullu D. G.
Published: September 2008

In tomato (Lycopersicon esculentum Mill. cv. St-Pierre), an adaptation to 75 or 100 mM NaCl, which results in an increase in growth, is obtained after transferring on media gradually enriched in NaCl, during four generations, either terminal parts of stems (including terminal bud and last internode) or calli initiated from roots or stems. Conversely, no growth increase is obtained at the fourth generation, when the culture medium has a NaCl concentration similar to that of the preadaptation medium of calli or young plants of the three previous generations. A comparison between the growth of calli and that of young plants originating from transfer of terminal parts of the stem reveals that the latter have the best NaCl adaptative abilities. Among the factors linked to the adaptative process at the level of cell masses of calli or at the level of differentiated cells of young plants are Na and Cl content, a decrease of Cl/Na ratio, an increase of K, Ca, or soluble sugar contents, the proline synthesis, a repartition of ions or metabolites proportional to accumulated masses, and an increase of peroxidase activity in plant roots.
A rapid phytochrome-mediated growth response in etiolated Sinapis alba hypocotyls
Authors: Kristie David N. , Jolliffe Peter A.
Published: September 2008

Photocontrol of hypocotyl elongation in etiolated Sinapis alba L. seedlings was investigated using a high-resolution growth-measurement system. Different photoresponses were characterized by the dynamics of plant response to monochromatic irradiations at wavelengths ranging from 380 to 780 nm. Brief puises of 660- or 670-nm red light caused a large, rapid inhibition of growth rate after a lag of ca. 5 min. Growth rate remained depressed for several hours following a single red light pulse. If given 120 min or less after the red light, a 740-nm far-red pulse reversed the inhibitory effects of prior red light treatment after a lag of ca. 6 min. Most seedlings did not respond to single far-red irradiations in the 720- to 780-nm wave band, although some underwent small depressions in growth 5 to 10 min after the end or irradiation. Irradiation with 450-nm blue light caused a deeper inhibition than red light after a lag of only 1 min. Recovery from inhibition by blue light was rapid, unless the irradiation was prolonged. Removal of the plumule and cotyledons did not affect the dynamics of the rapid blue and red – far-red growth responses. The rapid response to red light occurred at wavelengths from 550 to 710 nm. The rapid blue response occurred only from 380 to 500 nm. Within each of these wave bands, the depth of photoinhibition was nearly constant. However, the duration of photoinhibition by red light declined from about 3 h after a 660-nm pulse to about 45 min after a 710-nm pulse. Elongation in etiolated Sinapis hypocotyls is thus controlled by a classical phytochrome-mediated induction-response system and by the blue light photoreceptor. Photoinhibition of hypocotyl elongation by red light required a minimum of about 5% of total phytochrome to be in the far-red absorbing form.
The reproductive biology of boreal forest herbs. I. Breeding systems and pollination
Authors: Barrett Spencer C. H. , Helenurm Kaius
Published: September 2008

Detailed observations and experimental studies of the reproductive biology of 12 boreal forest herbs were conducted over a 3-year period (1978–1980) in spruce–fir forests of central New Brunswick. The species examined were Aralia nudicaulis, Chimaphila umbellata, Clintonia borealis, Cornus canadensis, Cypripedium acaule, Linnaea borealis, Maianthemum canadense, Medeola virginiana, Oxalis montana, Pyrola secunda, Trientalis borealis, and Trillium undulatum. All taxa are insectpollinated perennials and most exhibit clonal growth. Floral syndromes of the understory community are relatively unspecialized with many species possessing small white or green flowers. A total of 103 taxa of insects were collected from flowers during the 1979 season. Bombus spp. are the major pollinators of 5 of the 12 species. Syrphid flies, bee flies, and halictid and andrenid bees were also commonly observed. Controlled pollinations were undertaken to determine the breeding systems of herbs. Bagged, self-, cross- and open-pollinated treatments were used to investigate the capacity for self-pollination, compatibility status, and factors influencing fecundity in each species. A diversity of reproductive systems was revealed. Six species are completely dependent on insects for pollination, four species are weakly autogamous, one is strongly autogamous, and one appears to be apomictic. Comparisons of fruit-set and seed set from controlled self- and cross-pollinations indicate that four species are strongly self-compatible, one is dioecious, and the remainder display varying degrees of self-incompatibility. Despite this variation, outbreeding appears to be the most common reproductive mode. In several species there is evidence that low pollinator service limits fruit-set.
Influence of soil matric potential on 14C exudation from fungal propagules
Authors: Filonow A. B. , Arora D. K.
Published: September 2008

The influence of soil matric potential (ψm) on 14C exudation from labeled fungal propagules incubated in two soils over 5 days was determined, using tensiometers set at 0, −50, −100, and −200 mbar ψm (1 bar = 100 kPa). In general, 14C exudation to soil (as a percent of initial label) tended to be greatest at 0 mbar and decreasing ψm. In a sandy loam soil, the range of 14C exudation from conidia of Bipolaris victoriae or sclerotia of Macrophomina phaseolina was 18.4–20.9 or 4.4–5.5% at 0 mbar. At −200 mbar, it was 5.5–6.0 or 1.2–1.7%, respectively. In a clay loam soil at 0 mbar, conidia of B. victoriae or B. sorokiniana lost 17.6–19.9 or 7.3–9.2%, respectively, of total 14C label as exudate. At −200 mbar 14.6 or 5.9–7.2% was lost, respectively. Sclerotia of M. phaseolina lost 5.1–5.7% 14C-labeled exudate to the clay loam soil at 0 mbar and 4.3–4.6% at −200 mbar. 14C exudation at ψm less than saturation was about 2–3 times greater in the clay loam soil than in the sandy loam soil. Calculated ratios of evolved 14CO2/total 14C-labeled exudate were lowest at 0 mbar and increased as ψm decreased, suggesting that oxygen availability and soil water content as regulated by ψm were related to soil respiratory utilization of exudate.
Response of loblolly pine to different inoculum doses of Ceratocystis minor, a blue-stain fungus associated with Dendroctonus frontalis
Authors: Paine T. D. , Stephen F. M.
Published: September 2008

Infection and invasion by the southern pine beetle, Dendroctonus frontalis Zimm., and its associated fungi stimulate the inducible defense system of loblolly pine and result in production of a hypersensitive-like lesion around the affected tissue. The length of the lesion stimulated by inoculation is not related to the amount of inoculum introduced into the tree, even with an eightfold difference. The extent of the response is greater with large inoculum doses, but that is likely to be a function of initial inoculation wound size.
Leptosphaeria hispanica, a new species of the Dothideales, Ascomycotina
Authors: Checa J. , Moreno G.
Published: September 2008

The authors propose a new species, Leptosphaeria hispanica, characterized by its spore morphology. The most interesting microscopical characters are illustrated photographically.
Internal hyphae in young, symptomless needles of Picea abies: electron microscopic and cultural investigation
Authors: Suske Jürgen , Acker Georg
Published: September 2008

Results from cultural investigations were correlated with scanning electron microscope observations and give an introduction to the interaction of endophytic hyphae of Lophodermium piceae (Fckl.) Höhn. and other fungi with living tissues of green, symptomless needles of Norway spruce (Picea abies Karst.). The frequency of endophytic needle fungi was determined by the culture of surface-sterilized needles harvested from two trees. Lophodermium piceae was found to be the most important colonizer of symptomless needles; the infection rates ranged from about 3 to 7%. The presence of fungal hyphae in living needle tissues of symptomless, current year and older Norway spruce needles was demonstrated by scanning electron microscopy. The observed mycelia were both intercellular and intracellular. The hyphal diameters varied significantly and striking swellings of unknown function were observed along internal hyphae. The observed needle colonization is discussed in connection with the spreading of fungal endophytes in the host tissues during the endophytic phase of L. piceae in Norway spruce needles.
Structure of Armillaria rhizomorphs from Wisconsin aspen stands
Authors: Stanosz G. R. , Patton R. F. , Spear R. N.
Published: September 2008

Examination of Armillaria rhizomorphs collected from the soil of aspen (Populus tremuloides Michx. and P. grandidentata Michx.) sprout stands in northern Wisconsin revealed a complex structure consisting of four distinct zones. The innermost area (zone 4) consisted of interspersed fiber hyphae and broader, tubelike hyphae and was surrounded by a region composed of fiber hyphae only (zone 3). In thick (usually > 2 mm in diameter) rhizomorphs, zone 4 appeared as a distinct, dense central core that was darker than zone 3. In all rhizomorphs zones 2 and 1 were continuous to the exterior. Several layers of broad, thin-walled cells comprised zone 2. Toward the outside of zone 2 these cells gradually became thicker walled and merged with a zone of fused, thick-walled cells with very small lumens (zone 1). Zone 2 was less distinct in thicker rhizomorphs, probably as a result of gradual thickening of cell walls and addition of these to zone 1. The types of hyphae observed and their organization are discussed in relation to previous descriptions of rhizomorphs attributed to Armillaria mellea.
Photosystem II activity and triazine resistance in weeds
Authors: Sinclair John , Macdonald Philip
Published: September 2008

The oxygen-evolving properties of broken chloroplasts isolated from biotypes of Chemopodium album and Amaranthus retroflexus that were either sensitive or resistant to s-triazine herbicides were compared. The pattern of oxygen flash yields produced by herbicide-sensitive, dark-adapted chloroplasts of either species was reminiscent of that found with spinach chloroplasts. In contrast, dark-adapted chloroplasts isolated from the herbicide-resistant biotypes exhibited a highly damped oxygen flash pattern in which there was significant oxygen released after the first light flash. Analysis of these results with the Kok model of photosystem II (Kok, B., Forbush, B., and McGloin, M. 1970. Photochem. Photobiol. 11: 457–475) suggested that the unusual properties of the resistant organelles were due to the survival of significant amounts of S3 and S2 states during dark adaptation and to a higher proportion of inactive photosystem II reaction centres during each light flash. Deactivation experiments verified the suggestion that the S3 and S2 states more readily survive a 10-min dark period in resistant organelles. Information about electron transport on the oxidizing side of photosystem II was obtained with a modulated oxygen electrode and suggested that there was no difference between the two biotypes in the value of the rate constant of the reaction that limits the rate of electron transport between the water-splitting step and photosystem II.
Classification of cultivated barley (Hordeum vulgare). 2. Elaboration of cultivar groups
Authors: Baum Bernard R.
Published: September 2008

Two barley (Hordeum vulgare L.) cultivar groups were established from 329 world-representative accessions of named cultivars scored for 37 morphometric characters. The two groups are similar to the popular division of two rowed and six rowed, one group containing mostly two-rowed barleys but also a few of the other kind and the second group mostly six rowed barleys together with some two-rowed. Both groups include naked and covered types, "iregular," "deficiens," and other types. The implications of the two groups for barley cultivar nomenclature are discussed. The two cultivar groups were discerned by the application of various hierarchical cluster analyses in combination with three different stopping rules as indicators to cluster numbers, supported by classificatory discriminant analysis with cross validation, and their relationships illustrated by canonical discriminant analyses.
The ultrastructure and cytochemistry of the egg apparatus of Brassica campestris
Authors: Sumner M. J. , Caeseele L. Van
Published: September 2008

The egg apparatus of Brassica campestris L. cv. Candle (canola-rapeseed) is composed of an egg and two synergids juxtaposed at the extreme micropylar end of the megagametophyte with the egg cell displaced in a chalazal direction. The cell walls of the synergids and egg are uniformly PAS and PA–TCH–SP-positive, but contained β-linked glucans only in the micropylar region. The number and development of the cytoplasmic organelles suggested that the egg cell is relatively inactive metabolically while the synergid cells are active. The synergids contain large numbers of dictyosomes with PA–TCH–SP-positive vesicles at the maturing face. These vesicles appear to fuse with the plasma membrane in the region of the filiform apparatus. The filiform apparatuses of the synergids are micropylar finger-like projections that extend into the cytoplasm of the synergid. These are PAS and PA–TCH–SP-positive, fluoresce in uv light when stained with Calcofluor, and show a positive response for acidic polysaccharides when stained with alcian blue. After treatment with cellulase, fluorescence was not observed. The incipient degenerate synergid was intensely stained by cationic dyes 24–36 h after anthesis.
Ontogeny of Alnus rubra – Alpova diplophloeus ectomycorrhizae. II. Transmission electron microscopy
Authors: Massicotte H. B. , Ackerley C. A. , Peterson R. L.
Published: September 2008

Ultrastructural features of the two symbionts in ectomycorrhizae formed between Alnus rubra and Alpova diplophloeus change with developmental stage. In the root cap – meristem zone, hyphae penetrate between vacuolated root cap cells and become appressed to epidermal cells containing small vacuoles, plastids with starch, numerous Golgi bodies, mitochondria, and endoplasmic reticulum cisternae. In the young Hartig net zone, hyphae with few vacuoles penetrate between vacuolated epidermal cells that still contain numerous Golgi bodies but now have plastids with small starch grains. Hartig net hyphae begin to branch and eventually form a complex branching system in the mature Hartig net zone. Hartig net hyphae in the basal portion of the ectomycorrhizae synthesize lipid and finally become vacuolated.
Flower substances in the extremely disjunct species Oxytropis deflexa and their phytogeographical implications
Authors: Høiland Klaus , Laane Morten M.
Published: September 2008

Oxytropis deflexa (Pall.) DC. is found on a global scale mainly in three extremely disjunct areas. This interesting pattern arose probably 10 000 years ago as a result of the termination of the Weichselian glaciation. In Europe the only known growing sites are in Finnmark, north Norway, where fewer than 500 specimens occur on two ecologically characteristic areas comprising only a few hectares. The species is known from localities in Asia 5000 km apart and also from North America. Plants from the main distribution areas differ in a number of characteristics. By examining the flower substances by thin-layer chromatography and by constructing dendrograms by the UGPMA procedure and using principal-coordinate analysis we found the Norwegian specimens to be chemotaxonomically isolated from American and Asian populations. The special floral chemistry found in the Norwegian population probably evolved during postglacial times. Because the Norwegian specimens seem thermophilous, it appears unlikely that the species survived the last glaciation on eventual coastal refuges in north Norway, as has been proposed by others. Our findings do not contradict a view that the plant migrated westward from ice-free areas in north Asia in early postglacial time. The Oxytropis deflexa group thus allows studies of evolutionary processes that have occurred within a time scale of approximately 10 000 years.
Induction and growth of callus derived from rachilla explants of young inflorescences of coconut palm
Authors: Sugimura Yukio , Salvaña Myrna J.
Published: September 2008

When suitable stages of rachilla tissues derived from coconut palm were selected as an explant source, a higher frequency of callus induction was observed in medium containing activated carbon and 20–30 ppm 2,4-dichlorophenoxyacetic acid (2,4-D).
Shoot ontogeny in Fraxinus pennsylvanica (green ash). I. Seasonal cycle of terminal meristem activity
Authors: Remphrey W. R.
Published: September 2008

Terminal meristem ontogeny of mature Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern, (green ash) was investigated by bud dissection, histological analysis, and scanning electron microscopy. The shoots were completely preformed and bud-scale initiation for the next bud began in the spring shortly before any visible sign of swell. Foliage-leaf initiation began in May and ceased in late June or early July, but there were certain differences in primordium production patterns between the two trees investigated and between the years of the study. Although temperature, as measured by heat-unit accumulation, played a significant role in the onset of shoot expansion and primordium initiation, its importance in controlling these processes diminished as the season progressed. Buds formed in the axil of every leaf primordium, but those in the axils of scales remained small. There was evidence of axillary bud initiation as early as the P1, stage. By P2 or P3 there was a clearly discernable shell zone of elongated cells. Such cells had relatively large vacuoles concentrated at each end, in contrast with the essentially nonvacuolate cells of the incipient bud meristem. In the terminal resting bud, there were well-developed scale-axil buds and protruding axillary meristems associated with foliage-leaf primordia.
Floristic boundaries in the Gulf of St. Lawrence region: a numerical approach based on the moss flora
Authors: Belland René J.
Published: September 2008

Possible phytogeographic boundaries within the Gulf of St. Lawrence region are examined using the moss floras of 29 smaller geographic units. Principal coordinates analysis (PCoA) shows floristic change in the Gulf to be gradual and to follow two major gradients, a north–south gradient and an east–west gradient. These are positively correlated to the distributions of temperate and arctic species, respectively. PCoA ordinations also show no evidence of distinct boundaries between adjacent units, but indicate that Cape Breton Island and Gaspé Peninsula have floras of intermediate composition to those of the Maritimes and Newfoundland. Randomly generating floras for adjacent units using Monte Carlo simulation supports the results obtained from PCoA. The real Jaccard similarities between adjacent units are found to be greater than those expected from simulation. The lack of distinct boundaries in the Gulf of St. Lawrence region is attributed to the high diversity of species distributions possible in a region with complex environmental gradients.
Host range studies for Haptoglossa and a new species, Haptoglossa intermedia
Authors: Barron G. L.
Published: September 2008

Haptoglossa intermedia sp.nov., recovered from woodland soil, is described as a new endoparasite of rotifers. The species is distinguished from others by the shape and size of the gun cell, the fusiform infection sporidia, and the shape of the thalli. This species, along with H. zoospora, H. mirabilis, and H. humicola, can attack and complete its life cycle on both rotifers and nematodes. Tardigrades (water bears) may be alternative hosts for Haptoglossa species.
Development of epidermal crystals in leaflets of Stylosanthes guianensis (Leguminosae; Papilionoideae)
Authors: Brubaker Curt L. , Horner Harry T.
Published: September 2008

In developing leaflets of Stylosanthes guianensis (Aubl.) Sw., twin prismatic calcium oxalate crystals form in adaxial and abaxial epidermal crystal idioblasts. These cells eventually die and collapse, leaving the crystals embedded in a matrix of cutin and cell-wall materials. Adaxial crystal idioblasts develop above large conical cells that, in turn, are interspersed among smaller, multiple-layered palisade parenchyma. Abaxial crystal idioblasts develop beneath a uniseriate layer of large horizontally branched cells abutting the abaxial epidermis. Spongy parenchyma occupies the middle mesophyll above the layer of branched cells. The abaxial crystals and the branched cells of the lowermost mesophyll develop simultaneously. Adaxial crystals and the conical cells develop later and in conjunction with each other. In mature leaflets, the adaxial and abaxial crystals and their associated collapsed crystal idioblasts form networks, the interstices of which are occupied by either single stomates and accompanying epidermal cells (adaxial) or clusters of stomates and accompanying epidermal cells (abaxial). Epidermal crystals are known from other Leguminosae; however, to our knowledge this is the first report where epidermal crystal development involving cell death and collapse is correlated with two types of specialized mesophyll cells.
Differences in the colonization of Pinus banksiana roots by sib-monokaryotic and dikaryotic strains of ectomycorrhizal Laccaria bicolor
Authors: Wong Ken K. Y. , Piché Yves , Montpetit Diane , Kropp Bradley R.
Published: September 2008

First-order laterals of Pinus banksiana seedlings were inoculated with variant strains of ectomycorrhizal Laccaria bicolor in an aseptic culture system. Macroscopic observations of 10 fungal strains indicated that 6 are mycorrhizal and 4 are apparently nonmycorrhizal. Furthermore, light microscopic examinations revealed significant intraspecific variation in mycorrhizal structures. The mean mantle thickness, mean mantle density, and mean Hartig net penetration of the six mycorrhizal strains ranged from 2.5 to 13.4 hyphae, 278 to 411 hyphae/mm and 2 to 2.8 root cell layers, respectively. Three of these strains formed fewer macroscopically observable mycorrhizae and developed significantly thinner mantles but their Hartig nets usually separated cortical cells more extensively. Three of the four apparently nonmycorrhizal strains showed infrequent and poor Hartig net development (mean penetration of 0.3 to 0.8 root cell layer), poor surface colonization, and no mantle development. These three strains were better able to colonize long roots. Only one strain could be considered truly nonmycorrhizal because it only colonized root surfaces poorly and never showed mantle or Hartig net formation. The observed intraspecific variability raises questions concerning the determinants of mycorrhiza development and structure.
Entoloma (Basidiomycetes, Agaricales) of alpine habitats on the Hardangervidda near Finse, Norway, with a key including species from Northern Europe and Greenland
Authors: Noordeloos Machiel E. , Gulden Gro
Published: September 2008

Twenty-three species of Entoloma are described from the surroundings of Finse on the mountain plateau Hardangervidda, in southern Norway. Many of them belong to the group of arctic and alpine taxa having a circumpolar distribution. A key to the species in alpine and (sub)arctic habitats is given. Twelve species are recorded for the first time from Norway.
Additions to the technique of epi-illumination light microscopy for the study of floral and vegetative apices
Authors: Charlton W. A. , Macdonald A. D. , Posluszny U. , Wilkins C. P.
Published: September 2008

Various staining techniques for apices destined for epi-illumination light microscopy are described and discussed. Appropriate modifications to photographic procedures are described. A technique is described for the subsequent observation of specimens in a scanning electron microscope fitted with a cryo-stage.
An electrophoretic study of representatives of subgenus Diploxylon of Pinus
Authors: Karalamangala Roopa R. , Nickrent Daniel L.
Published: September 2008

Relationships among 14 taxa in subgenus Diploxylon of Pinus from Mexico and the United States were analyzed using 15 isozyme loci obtained from both frozen and fresh needle tissue. The phenogram obtained from cluster analysis of genetic distance values and phylogenetic trees implementing the distance Wagner procedure were in general agreement with classifications based on morphological features. Pinus leiophylla is genetically distinct from other species. Two groupings, one comprising P. oocarpa and P. pringlei and another comprising P. lawsonii and P. teocote, correspond to sections Serotinus and Teocote (sensu Martínez), respectively. Classification of the remaining eight taxa has varied, ranging from their placement in three, two, or only one section. Isozyme analysis resulted in a group that included P. cooperi, P. douglasiana, P. durangensis, P. michoacana, and P. montezumae, which suggests genetic affinity between Sections Pseudostrobus and Montezumae (sensu Martínez). This result corresponds more closely to the placement of these species in subsection Pseudostrobi. The distant relationship between P. engelmannii and the ponderosa pines may be anomalous (an artifact of small sample size) or may indicate greater genetic divergence than previously recognized.
Specific attraction to and infection of cotton root cap cells by zoospores of Pythium dissotocum
Authors: Goldberg N. P. , HAwes M. C. , Stanghellini M. E.
Published: September 2008

Root cap cells of two cotton species (Gossypium barbadense L. and G. hirsutum L.) elicited a specific chemotactic response in zoospores of Pythium dissotocum. When roots of cotton seedlings were placed into a suspension of Pythium dissotocum zoospores, there was immediate attraction, accumulation, and encystment exclusively in the root cap region. Seedlings which attracted zoospores were killed within 24 h. Furthermore, root cap cells remained attractive when isolated nondestructively from the root and placed into a zoospore suspension; attraction, accumulation, and encystment on individual root cap cells occurred within seconds after contact. Penetration and death of isolated cells occurred within 15–30 min. After 30 min, approximately 25% of living cells were directly colonized by zoospores. Root cap cells killed by freezing or drying remained attractive but at a reduced level; approximately half as many killed cells as living cells were directly colonized by zoospores. The number of root cap cells directly colonized by zoospores did not increase with time. In contrast, zoospores of Pythium catenulatum that exhibited a chemotactic response to Agrostis palustris (Bentgrass) were not attracted to and did not infect cotton seedlings or isolated root cap cells.
Effect of light intensity on the development of pine wilt disease
Authors: Kaneko Shigeru
Published: September 2008

Two-year-old seedlings of Japanese red pine were inoculated with Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle, the nematode causal agent of pine wilt disease, in three experimental plots. The plots were maintained under continuous radiation of 2, 9, and 35 klx (27, 155, and 660 μE∙m−2∙s−1) light intensity at 25 °C. The number of nematodes inoculated was 5000 per seedling. Development of the disease was faster at 2 and 9 klx than at 35 klx light intensities, total mortality rates 63 days after inoculation being 97, 90, and 13%, respectively. No differences were found among the three experimental plots in the number of nematodes extracted from killed seedlings. During the early days after inoculation, the photosynthetic rate of inoculated as well as control seedlings was distinctly accelerated with these increasing light intensities. The photosynthetic ability of the inoculated seedling under the 2-klx regime became abnormal 7 days after inoculation, whereas under the 9- and 35-klx regimes, it became abnormal 12 days later. The first external symptom on the seedlings used for the measurement of photosynthetic rate appeared from 27 to 31 days after inoculation. These results demonstrate that the development of the pine wilt disease is strongly correlated with the photosynthetic rate of pines, and that this photosynthetic ability is reduced considerably before the first symptoms appear.
Isozyme variation in the fungus Atkinsonella hypoxylon within and among populations of its host grasses
Authors: Leuchtmann Adrian , Clay Keith
Published: September 2008

Isozyme variation of 291 isolates of Atkinsonella hypoxylon (Clavicipitaceae, tribe Balansieae) from 24 populations of its four known host grasses (Danthonia compressa, Danthonia sericea, Danthonia spicata, and Stipa leucotricha) was examined using starch gel electrophoresis. In total, there were 20 distinct multilocus genotypes. Eleven out of 13 enzyme loci (84.6%) exhibited more than one allele (mean 2.8) per locus. Nei's total gene diversity (HT) within all isolates was 0.229. Between isolate samples from S. leucotricha and the three Danthonia hosts, Nei's genetic identity (I) ranged from 0.21 to 0.31 and among isolate samples from the three Danthonia species I ranged from 0.65 to 0.88, with isolates from D. spicata and D. compressa being most similar. Variation of A. hypoxylon occurred both within and among populations of D. spicata and D. compressa, where up to 53 isolates were sampled per host population. In contrast, all 20 isolates from S. leucotricha were identical, as were all 6 from D. sericea. A few isolates from D. spicata exhibited the same, unusual multilocus genotype with unique alleles at six different loci. The occurrence of several multilocus genotypes in isolates from the same ascostroma and the 1:1 segregation of genotypes among ascospores from a single ascus indicated gene exchange among sexually reproducing individuals, consistent with a heterothallic mating system for A. hypoxylon.
Frequency and diversity of ectomycorrhizal and saprophytic macrofungi in the Laurentide Mountains of Quebec
Authors: Villeneuve Normand , Grandtner Miroslav M. , Fortin J. André
Published: September 2008

Total macro fungus frequency in closed forest associations of the Laurentide Mountains varied little (147 – 185 %) from one to another. The macrofungal flora of the deciduous forest was composed mainly of many infrequent species, whereas coniferous forests had few, but very frequent, macrofungi. Total frequency was significantly lower (15%) in open stands of the spruce–cladina association. Species richness decreased gradually (from 125 to 34 species) towards the north and with increasing altitude. Both the Simpson and the Shannon–Wiener diversity indices were significantly lower in the coniferous forest when compared with the deciduous forest. This decrease in diversity was due to the scarcity of saprophytic fungi in mor humus, whereas the number of ectomycorrhizal species remained constant. The diversity of saprophytic fungi was related significantly to that of vascular plants, whereas the diversity of ectomycorrhizal macrofungi was related mainly to the percent cover of ectomycorrhizal hosts. A total of 195 species of macrofungi were recorded for the study sites. In the maple – yellow birch forest, most of the macrofungi were saprophytic members of the Tricholomataceae, Hygrophoraceae, Strophariaceae, and Clavariaceae, many being exclusive in this association. However, each biological group had approximately equal frequency (44–54%) and richness (37–45 taxa). Species composition of the coniferous forest differed from the former in the clear dominance of ectomycorrhizal macrofungi from the Cortinariaceae, Russulaceae, and the Boletaceae. In the black spruce – cladina association, saprophytic fungi were scarce and ectomycorrhizal species were also relatively infrequent. In all the sites, the equitability of macrofungal frequency was high, as seen by the high proportion of rare species. The decline in species richness observed in this study, when moving from deciduous to coniferous forests, corresponds well with the increase in environmental rigor and instability, as well as the decrease in the diversity of organic substrate and species of vascular plants.
Postfire lichen–spruce woodland recovery at the limit of the boreal forest in northern Quebec
Authors: Morneau Claude , Payette Serge
Published: September 2008

A 250-year postfire plant chronosequence in well-drained sites at the northern limit of the Boreal Forest in the Grande rivière de la Baleine area, northern Quebec, was reconstructed from nine sites associated with the development of the lichen–spruce woodland. Most species recorded along the chronosequence reinvaded burned sites within 15 years after fire, whereas important vegetational changes occurred during the first 100 years of postfire recovery, corresponding to full development of the Cladina stellaris – spruce woodland. No vascular plant species replacement was observed during succession, whereas by contrast a well-defined lichen–bryophyte sequence occurred along five successional stages. Species diversity (Shannon index) was low 4 years after fire, but it has reached a maximum about 25 years after fire and then dropped and stabilized at a low value in old-growth woodlands dominated by black spruce (Picea mariana (Mill.) BSP) and C. stellaris. The active period of black spruce sexual regeneration spans about 20–25 years, with maximum regeneration occurring between 5 and 14 years after fire. After this period, seed regeneration is mostly sporadic and sustained layering becomes fairly common at all sites. From 100 to 250 years after fire, no significant changes were observed in vegetation structure, floristic composition, species diversity, and spruce regeneration, suggesting that lichen woodlands are selfperpetuating in absence of fire. In limiting spruce regeneration at the ground surface, the lichen cover seems to be the most important factor controlling the open structure of the lichen–spruce woodland.