bluuebunny/crossref_metadata_2025 huggingface dataset:
A general method for determining translocation velocity in Laminariales
Authors: Buggeln Richard G.
Published: April 2011

The nondestructive pulse method for studying 14C-labelled photoassimilate translocation in Alaria esculenta has been adapted for species of Laminariales with flat, thick blades, in this case, Laminaria digitata. A 1-h pulse of [14C]bicarbonate(25 μCi) was applied to one side of the blade surface via a 12 mm diameter by 22 mm high, closed cylindrical incubation chamber. The upper 20-mm closed portion of the chamber was removed after the incubation period, the lower 2-mm open portion remained glued to the blade surface during the subsequent translocation period. A Geiger-Müller (G-M) detector probe with a 50 mm diameter end-window was used to measure the disappearance of radioactive organic matter from the pulsed region over the next 11–12 days. Accurate monitoring of the movement of 14C-labelled solutes through the cortex and into the medulla was confounded by changing absorption of radioactivity by the cortex. Uniform absorption was achieved once the translocatable radioactivity reached the medullary conducting cells (sieve filaments). Thus arrival and accumulation of 14C-labelled assimilate in the blade sink (meristem) was reliably measured with the G-M probe. For Laminaria digitata, the translocation velocity of the moving solute front was 1.7 cm∙h−1. The specific mass transfer of carbon was estimated at 0.4 mg C∙week−1∙mm−2 cross-sectioned medulla. Fifty-seven percent of assimilated carbon was exported in 10 days; 97% of the 14C remaining in the source was in insoluble matter and 3% was in soluble matter. Cutting sieve filaments on the sink side of the incubation chamber did not stop short distance transport through the cortex, but significant 14C-labelled photoassimilate was apparently unable to be re-routed around the cut as no radioactivity was detected in the sink area, the meristematic region at the base of the blade.
Somatic hybridization between Nicotiana rustica and N. tabacum. I. Isolation and culture of protoplasts and regeneration of plants from cell cultures of wild-type and chlorophyll-deficient strains
Authors: Douglas G. C. , Keller W. A. , Setterfield G.
Published: April 2011

Preliminary to somatic hybridization between chlorophyll-deficient mutants of Nicotiana rustica and N. tabacum conditions for cell culture, protoplast production and culture and induction of morphogenesis were established. Callus and suspension cultures from wild-type and chlorophyll-deficient strains of both species were established and maintained on Murashige and Skoog medium containing either 2,4-dichlorophenoxyacetic acid (2,4-D) or naphthaleneacetic acid (NAA). The chlorophyll-deficient phenotype was evident in cultures derived from mutants of both species. Protoplasts were readily obtained from cell cultures with N. rustica outyielding N. tabacum and mutant cells of the latter substantially outyielding the wild-type cells. In Nagata and Takebe medium protoplasts regenerated cells walls and 60–80% divided and formed cell colonies. Protoplasts from cultures on 2,4-D medium were healthier but slower to divide than those from cultures grown on an NAA-supplemented medium. Protoplasts derived from 2,4-D-grown cells also gave rise to proembryo-like structures. Shoot and root organogenesis could be induced in cell colonies obtained from both suspension cultures and protoplasts of mutant and wild-type N. rustica. With albino N. tabacum only cell colonies from cell suspension showed morphogenic potential. Maximum frequencies of colonies forming shoots were 77% for N. rustica cv. chlorotica and 100% for albino N. tabacum. The morphogenic capacity of colonies from 2,4-D-grown cells was greater than from cells grown on NAA. Morphogenic capacity of both species declined with increasing age of the suspension cultures. Roots were induced on shoots of the wild type in both species as well as in the chlorophyll-deficient N. rustica mutant.
A numerical analysis of morpho-geographic groups of cultivars of Humulus lupulus based on samples of cones
Authors: Small Ernest
Published: April 2011

Numerical analyses of hop (strobilus) samples showed that the geographical origin of cultivars of Humulus lupulus L. from North America, Britain, continental Europe, and Japan can be identified with considerable reliability on the basis of morphological examination. Samples of hybrid origin between North American and European plants tended to be similar to American cultivars, but often showed combinations of Old and New World characteristics, making their identification problematical.
Development of hyphal sheaths in Bipolaris maydis race T
Authors: Evans Robert C. , Stempen Henry , Stewart Sandy J.
Published: April 2011

Light microscopic studies of Bipolaris maydis race T demonstrated that a fibrillar sheath, often several times the hyphal diameter, can be observed when the hyphae are negatively stained with India ink or treated with fluorescent antibodies or diaminobenzidine. Sheaths were observed on hyphae incubated under a variety of cultural conditions and on race O of B. maydis as well as on other species of Bipolaris. Sheaths were found only on rapidly growing hyphae such as tips and germ tubes; conidia and hyphal segments older than approximately 72 h lacked a sheath. Examination of the hyphae using electron microscopy confirmed the age-dependent nature of the sheath and suggested that the lack of this structure on old hyphae is due to the deposition of a pellicle on the hyphal surface.
Sclerocarps: undescribed propagules in a sand-inhabiting marine fungus
Authors: Kohlmeyer Jan , Charles Thomas M.
Published: April 2011

Varicosporina ramulosa Meyers et Kohlm., a Fungus Imperfectus living on detritus of the intertidal zone in the tropics and subtropics, forms sclerotia-like propagules attached to grains of sand. These hitherto undescribed reproductive structures are shown to survive extreme conditions in beaches and to be homologues of Ascomycete fruiting bodies (ascocarps). Based on laboratory experiments and microscopical observations, we postulate here that V. ramulosa is an Ascomycete (probably in Halosphaeriaceae) that in the course of evolution has lost its ability to reproduce sexually. Accordingly, we propose the new term sclerocarp (from the Greek skleros = hard, karpos = fruit) to describe modified ascocarps that have permanently lost their sexual capacity and function now as sclerotia, i.e., resting structures. Cell walls in the center of sclerocarps contain pit connections that have been reported only from ascocarps of Halosphaeriaceae.
Interactions between fungi and plants through the ages
Authors: Pirozynski K. A.
Published: April 2011

Most of the modern vascular plants form either endo- or ecto-mycorrhizal symbioses with fungi. Few plants are not mycotrophic.Each condition has probably arisen in different groups of plants, at different times during their evolution, and with different consequences: the origin of vascular plants, the evolution of arborescent and herbaceous habits, and the differences in composition of forests are speculatively linked with mycotrophism.
The role of neutral lipids in the physiology and ecology of subarctic Dicranum elongatum
Authors: Karunen Pirjo
Published: April 2011

Temperature (1–23 °C) had little effect on the percentage composition of fatty acids in the common and acetylenic triglycerides of Dicranum elongatum Schleich., though the triglyceride contents in both green and senescent parts were highly dependent on temperature. Field material collected in October from low temperature and dim light plus dark conditions, when exposed to light (140 μE m−2 s−1) in growth chambers, showed increased amounts of acetylenic triglycerides most prominently at low temperature, and decreased amounts of the common triglycerides most prominently at the highest temperature. An overall increase of triglycerides (common plus acetylenic) was found only at low temperature (1 and 6 °C).In contrast to the triglycerides, the fatty acid content of the combined steryl plus wax esters increased only slightly (9%) at low temperature (1 °C). At elevated temperature (17 and 23 °C) the content in both green and senescent parts decreased in conjunction with growth. Temperature (1–17 °C) had no great effect on the proportions of the alkyl or acyl moieties of the esters. At 23 °C, however, a clear decrease was found in the proportions of 20:4 ω6 and 18:3 ω3, along with an increase in the proportion of saturated fatty acids. This was most pronounced in the green segment, where the proportion of the steryl esters was lowest.
The vegetative body of Metasequoia milleri from the Middle Eocene of southern British Columbia
Authors: Basinger James F.
Published: April 2011

Anatomically preserved vegetative remains of Metasequoia milleri Rothwell and Basinger are common in the Princeton chert of the Allenby Formation in southern British Columbia. Deposition of the Allenby Formation and associated volcanics occurred during Middle Eocene time. The Princeton chert locality is in the upper strata of the Allenby Formation and is of late Middle Eocene age. The Princeton chert was formed by siliceous permineralization of marsh soil. Dissolved silicates were probably introduced by periodic influx of water from mineral springs or geysers.Anatomical features of stems, wood, and leaves are well preserved. Mature wood of the fossil resembles that of Metasequoia glyptostroboides in having traumatic resin cysts; opposite pitting on radial walls of tracheids; taxodioid cross-field pitting; tall, uniseriate rays; smooth-walled ray parenchyma; and diffuse, resinous, smooth-walled wood parenchyma. Leaves are linear, hypostomatic, and borne decussately, and have one or three resin ducts and slightly undulate to smooth epidermal cell walls. Leaves of living M. glyptostroboides differ in consistently having three resin ducts and much more pronounced undulations of epidermal cell walls. Metasequoia milleri has leaves of a generalized structure from which leaf types of many taxodiaceous genera could be derived. Roots associated with M. milleri are dimorphic. Primary tissues and secondary phloem are exceedingly well preserved. Cortex of both long and short roots contains mycorrhizal fungi.Compression remains of M. occidentalis are not distinguishable from M. glyptostroboides. Anatomical features of M. milleri, however, do reveal differences between Eocene and living Metasequoia. Wood rays of M. milleri are much higher than those of M. glyptostroboides. Other features of stem anatomy are similar in both species. Pollen cones differ in developmental and minor anatomical features. The close similarity of most organs of M. milleri to M. glyptostroboides and the dissimilarity of leaf structure indicate mosaic evolution within the genus.
Ultrastructural cell wall modifications in secondary xylem of American elm surviving the acute stage of Dutch elm disease: fibres
Authors: Ouellette G. B.
Published: April 2011

Various ultrastructural cell wall modifications of fibres have been observed in artificially or naturally infected American elm (Ulmus americana L.) trees surviving the acute stage of the Dutch elm disease caused by Ceratocystis ulmi (Buism.) C. Moreau. Bands of fibres with gelatinous (SG) layers characteristic of tension wood are frequent in or near invaded tissues; similar layers are also present sometimes in cells identifiable as parenchyma. The SG layer is often different from that observed in healthy trees. Masses or bands of dense material are present which often extend perpendicular as tubular structures to the plasmalemma location. Also, orientation of fibrils in such layers may be disordinate. One or more additional lignified-like layers alternating with additional SG-like or other opaque layers may occur inside the first SG layer. The innermost layer in these cases is often lamellate.Small intracellular locules delimited by one or two wall layers also occur in other cells.The possible significance of these observations in host–parasite relationships of the disease is briefly discussed.
Dispersal and floating ability of dimorphic fruit segments of Cakile edentula var. lacustris
Authors: Payne Anita M. , Maun M. A.
Published: April 2011

Cakile edentula (Bigel) Hook var. lacustris occurs abundantly along sandy beaches of Lakes Huron, Erie and Ontario. Until now the species had not been reported to occur along Georgian Bay but we located one population at Deanlea Beach. The deciduous upper fruit segments disperse long distances by water waves and currents and short distances by rolling caused by strong winds. The lower fruit segments usually remain attached to the parents which may be uprooted by high waves and then transported as tumble weeds to new locations. The floatation experiment showed that the agitation of jars containing the fruits improved their floating ability. Agitated upper fruit segments showed a significantly lower sinking index than agitated lower fruit segments and upper and lower fruit segments in the still treatment. The overwintering of fruits improved their floating ability.
La végétation de l'escarpement d'Eardley, parc de la Gatineau, Québec
Authors: Gagnon Daniel , Bouchard André
Published: April 2011

The vegetation of the Eardley Escarpment, in Gatineau Park, was sampled in 69 stands using Whittaker's methodology. The plant communities, most of which are xeric and dominated by Quercus rubra or Pinus spp. or mesic and dominated by Acer saccharum, are analysed with indirect and direct ordinations. The analysis is based on the structure and floristic composition of the vegetation, as well as on environmental factors, disturbances, and successional status. The soils are described. The data for four meteorological stations were used to interpret microclimate. The spatial distribution of the communities seems influenced mostly by topography and fire disturbances. Two types of oak communities studied, rare or absent elsewhere in Quebec, have affinities with the Midwest.
Responses of the moss Tortula ruralis to desiccation treatments. I. Effects of minimum water content and rates of dehydration and rehydration
Authors: Schonbeck Mark W. , Bewley J. Derek
Published: April 2011

Samples of the moss Tortula ruralis were desiccated either rapidly or slowly to different tissue water contents to determine the limits of desiccation tolerance. Experimental samples were rehydrated rapidly by contact with wet filter paper, and gas exchange, chlorophyll content, electrolyte efflux, and linear growth rate were compared with those of control samples. Drying to 0.30–0.089 g H2O∙g dry weight−1 did not significantly affect the moss. Slow drying to 0.058–0.008 g H2O∙g dry weight−1 caused temporary increases in dark respiration and electrolyte leakage, and a slight inhibition of growth. Rapid drying of the same water contents caused visible injury, reduced total chlorophyll and the ratio of chlorophyll a:b, greatly enhanced electrolyte efflux, and severely inhibited gross photosynthesis and linear growth. The damaging effects of rapid drying could be eliminated either by partial desiccation for 1–3 h before rapid drying, or by placing the dry moss in a 100% relative humidity (RH) atmosphere for 1–5 h before rehydration.Tortula ruralis demonstrated greater drought tolerance than many other bryophytes, algae, seeds, and desert angiosperms, and is clearly capable of surviving any drought which might occur in its natural habitat.
Early events in the infection of soybean by Rhizobium japonicum. Time course and cytology of the initial infection process
Authors: Turgeon B. Gillian , Bauer Wolfgang D.
Published: April 2011

The time course of early infection events in Glycine max following inoculation with Rhizobium japonicum is described. Bacteria became attached to epidermal cells and root hairs within minutes of inoculation. Marked root hair curling occurred within 12 h. Infection thread formation was visible at the light microscope level of resolution about 24 h after inoculation. Infections were observed in short, tightly curled root hairs. These root hairs had not yet emerged at the time of inoculation. Infection threads appeared to originate in pockets formed by contact of the cell wall of the curled root hair with itself. Infection threads in the hairs were multiple and (or) branched. By 48 h, the infection thread(s) had progressed to the base of the root hair but had not yet penetrated into the cortex. Increases in cortical cell cytoplasm and in mitotic division occurred in advance of the penetrating infection thread. A nodule meristem developed in the outer cortex next to the infected root hair by 4 days and was accompanied by cell division across the cortex.
Distribution and abundance of periphyton and phytoplankton species in two subarctic Canadian rivers
Authors: Ennis G. L. , Albright L. J.
Published: April 2011

Periphytic and planktonic algal populations were sampled over a yearly cycle in the Ogilvie and Swift rivers located in the northern and southern Yukon, respectively. Diatoms and green algae dominated periphytic assemblages during spring, summer, and fall, whereas the bulk of the overwintering cells was diatoms. The 96 species of periphytic diatoms were dominated by Achnanthes minutissima Kütz., an unidentified species of Achnanthes, Cocconeis placentula Ehr., Diatoma hiemale var. mesodon (Ehr.) Grun., Diatoma tenue var. elongatum Lyngb., Anomoeoneis vitrea (Grun.) Ross, and Fragilaria crotonensis Kitton. Most diatoms encountered are also generally abundant in more temperate locations. Periphytic green algae were dominated by Mougeotia sp., Oedogonium sp., Ulothrix sp., and Stigeoclonium sp. In high flow regions of the Ogilvie River the red alga Lemanea fucina Bory was extremely abundant. Phytoplankton was sparse and generally represented by the same species as found in periphytic habitats. Results indicate that the phytoplankton cells were probably derived from sloughed periphytic cells. Achnanthes minutissima, Diatoma tenue var. elongatum, Fragilaria construens var. binodis (Ehr.) Grun., Fragilaria vaucheriae (Kütz.) Peters, and Synedra ulna (Nitz.) Ehr. were the most abundant species in the plankton.
Tremorgenic indole metabolites and aflatoxins in sclerotia of Aspergillus flavus: an evolutionary perspective
Authors: Wicklow Donald T. , Cole Richard J.
Published: April 2011

Isolates of Aspergillus flavus Link from both cool and warm latitudes were cultured on potato dextrose agar containing yeast extract to identify sclerotia-producing strains. Chloroform–MeOH extracts of sclerotia were analyzed for the presence of aflatoxins and major indole metabolites (e.g., cyclopiazonic acid, aflatrem, and dihydroxyaflavinine). Aflatoxin is reported from sclerotia of A. flavus for the first time. Cyclopiazonic acid was detected primarily in sclerotia of isolates from warmer latitudes. Aflatrem and dihydroxyaflavinine were detected in sclerotia from 85% of the strains examined. These metabolites are associated with the sclerotial stage of the life cycle, because neither were detected in extracts of the culture medium and mycelium of Petri dish cultures from which all the sclerotia were removed. Geographic variation and intrafungal allocation of these toxic compounds in A. flavus are examined from the evolutionary ecologist's perspective of selective forces shaping the chemical defense systems of fungi.
Penetration of Sitka spruce seeds by the pathogenic fungus Caloscypha fulgens
Authors: Woods T. A. D. , Farris S. H. , Sutherland Jack R.
Published: April 2011

Penetration of Sitka spruce, Picea sitchensis (Bong.) Carr., seeds by the pathogenic fungus Caloscypha fulgens (Pers.) Boudier was examined in intact and sectioned naturally infected and inoculated seeds with light and scanning electron microscopes. One to seven circular to slightly elongate, white to whitish blue infection cushions occurred on a typical naturally infected seed. Within 1–3 days following inoculation, the fungus formed dome-shaped infection cushions on the seed surface and within the next 10 days several straight-line penetration holes were observed in the seed coat directly under each cushion. During penetration, pathogen growth was confined to the penetration holes and intertissue spaces until it reached the endosperm and embryo tissues throughout which it ramified. Caloscypha fulgens occasionally entered seeds through seed coat cracks, but never through the micropyle. Pathogen emergence from diseased seeds occurred through intact or cracked seed coats and the micropyle.
Effects of CO2 enrichment on growth and photosynthesis in Desmodium paniculatum
Authors: Wulff Renata D. , Strain Boyd R.
Published: April 2011

Plants of Desmodium paniculatum (Leguminosae) were grown from seeds in normal air (0.035% CO2) and in air containing 0.1% CO2. CO2 enrichment produced an almost twofold increase in dry matter production. Leaf areas were 1.2 times higher at high CO2. Relative growth rates under high CO2 were significantly higher during the early stages of development and then declined. The increase in dry matter production was not associated with an increase in photosynthetic capacity per unit leaf area. Gas exchange measurements indicated that plants from the high CO2 regime had lower light saturation values and lower photosynthetic rates at high quantum flux densities than the controls. An opposite trend was observed if gas exchange rates were expressed on a chlorophyll basis. The depression in photosynthetic rates on a leaf area basis of plants exposed to CO2 enrichment was correlated with increased starch accumulation and reduced grana formation in chloroplasts of leaves continuously exposed to high CO2 concentrations.
Changes in organic chemical components of needle litter during decomposition. Long-term decomposition in a Scots pine forest. I
Authors: Berg Björn , Hannus Kai , Popoff Thomas , Theander Olof
Published: April 2011

The decomposition and organic chemical changes in Scots pine (Pinus silvestris) needle litter were studied for a period of 5 years and until 75% weight loss was reached in field incubation. The changes in components such as various groups of lipophilic extractives, low-molecular carbohydrates, cyclitols, phenolic glycosides, polysaccarides, and lignin were followed. There was a great drop of sugars, steryl esters, and triglycerides during the 1st year of decomposition. Some isoprenoid alcohols, sterols, and some acids belonged to the most stable of the soluble components. Of the solid residue the arabinans decomposed rapidly, the cellulose decomposed somewhat faster than the hemicelluloses as a group, and the lignin decomposed rather slowly (about 48% in 5 years).
Shoot formation in callus from the stalks of young female strobili of Larix decidua
Authors: Bonga J. M.
Published: April 2011

Small sections of immature female strobili of Larix decidua Mill, were cultured in vitro. Several adventitious buds and shoots developed from callus of stalk sections of strobili collected in early May from one of the trees sampled.
New species and new records of Tricholomataceae (Agaricales) from China
Authors: Redhead S. A. , Bo Liu
Published: April 2011

Descriptions and illustrations of microscopic features are provided for collections of Chaetocalathus galeatus (Berk. & Curt.) Singer, Crinipellis iopus Singer, C. subtomentosus (Peck) Singer, Marasmiellus mesosporus Singer, M. pusillimus sp. nov., M. sinensis sp. nov., M. filocystis sp. nov., and Macrocystidia lutea sp. nov. from China.
On the ecological significance of fruit color in Prunus serotina and Rubus occidentalis: field experiments
Authors: Morden-Moore Andrea L. , Willson Mary F.
Published: April 2011

The hypothesis that a bicolored fruit display increases fruit consumption by birds was supported by results of experimental displays of Prunus serotina fruits in solitary infructescences. However, at the level of a whole-tree fruiting display, the hypothesis was not supported: there was no significant difference in removal rates from bicolored and all-black displays on isolated trees; an all-black display was more attractive to avian dispersers on trees in a clumped distribution. For Rubus occidentalis, there was no significant difference in removal rates in different colored displays. There may be more reward per unit searching time in all-black trees because of more ripe fruits and perhaps more available insects; these possibilities are testable but leave unattended the problem of the evolution of bicolored displays.
Floral anatomy of Pittosporaceae: five species of Pittosporum
Authors: Narayana L. L. , Radhakrishnaiah M.
Published: April 2011

The flowers are tetracyclic, pentamerous, and hypogynous. The ovary of the bicarpellary syncarpous gynoecium is bilocular at the base and unilocular towards the apex or bilocular towards the base and apex and unilocular in the middle. The sepals are three traced and the origin of the sepal traces is peculiar in Pittosporum heterophyllum and P. rhombifolium. The petals and stamens are one traced. The heteromerous flowers of P. revolutum stand apart in perianth and androecial characters. The carpels are three traced except in P. phyllarioides, where they are five traced. There is adnation of traces between petals, stamens, and gynoecium and this precedes the external fusion. Judging from the position of the ventral bundles, the placentations can be described as parietal, anatomically parietal, or both in different parts of the ovary. A true nectariferous disc is lacking. The basal peripheral portion of the ovary resembles the disc, showing deep-staining cells, and it is devoid of any vasculature.
Leaf initiation in Cyclamen persicum (Primulaceae)
Authors: Sundberg Marshall D.
Published: April 2011

Leaf initiation in Cyclamen persicum Mill. 'F-1 Rosemunde' was examined. The sigmoid pattern of initiation which was observed may be described by a modified logistic equation which is not significantly different from that used previously to describe the pattern of leaf emergence. The relationship between initiation and emergence changes during the growing season so that initially there is an increase in the number of leaves in the bud, while later there is a decrease. It is suggested that (i) leaf emergence is not necessarily an accurate indicator of leaf initiation for application of the plastochron index and (ii) the sigmoid pattern of leaf initiation is more widespread than the literature would indicate.
Spore wall development in Sphagnum lescurii
Authors: Brown Roy Curtiss , Lemmon Betty E. , Carothers Zane B.
Published: April 2011

The spore wall of Sphagnum is unique in the Bryophyta. The Sphagnum spore exine consists of two layers: an inner, lamellate layer (A layer) and a thick, homogenous, outer layer (B layer). The exine of other mosses consists of only the outermost homogenous layer and, at most, a thin ill-defined opaque layer. During development of the A-layer exine and the intine, a cortical system of evenly spaced microtubules underlies the plasma membrane. The ontogeny of the wall layers is not strictly centripetal. The A-layer exine develops evenly around the young spore immediately after cytokinesis. As the intine is deposited centripetally inside it, the homogenous B-layer exine is deposited outside the first-formed A layer. The B layer is responsible for the primary sculpturing of the spore surface. The mature spore is covered by an outermost perine, which is responsible for secondary surface ornamentation. A trilaesurate aperture develops on the proximal surface of each spore after deposition of the A layer. Ridges of the laesurae develop as a result of deposition of thick areas of intine. The ridges are eventually covered by the outer wall layers, whereas the fissure is covered only by the A layer and a very thin B-layer exine. The complex development of the trilaesurate aperture is evidence that the structure is not merely a mechanically induced "trilete mark" or "scar" resulting from compression of tetrahedrally arranged spores within a sporocyte wall.
The effects of altered hydrologic regime on tree growth along the Missouri River in North Dakota
Authors: Reily Peggy W. , Johnson W. Carter
Published: April 2011

Increment cores were collected to examine effects of changed hydrologic regime on radial growth of floodplain trees downstream of Garrison Dam. Alterations in seasonal streamflow patterns, near elimination of over-bank flooding, and apparent lowering of the water table during the early growing season following completion of the dam in 1953 were implicated in the significant decline in postdam growth of Ulmus americana, Fraxinus pennsylvanica, Acer negundo, and Quercus macrocarpa. The measured decline in Populus deltoides growth was not statistically significant. Trees on terraces at the edge of the floodplain that received concentrated runoff from upland ravines (e.g., Quercus macrocarpa) and those with deep root systems (e.g., P. deltoides) on low terraces close to the water table were least affected. The most pronounced change in tree growth occurred on high terraces that received little upland runoff (e.g., U. americana, A. negundo). Multiple regression analysis for P. deltoides growth showed a distinct change from correlation with spring streamflow in the predam period to correlation with rainfall parameters in the postdam period. Growth of P. deltoides and Q. macrocarpa on reference sites unaffected by damming of the Missouri River increased significantly in the postdam period.
Detection of a necrosis-inducing factor of nonhost plant leaves produced by Pseudomonas syringae pv. tomato
Authors: Bashan Yoav , Okon Yaacov , Henis Yigal
Published: April 2011

A necrosis-inducing factor (NIF) was extracted from two virulent strains of Pseudomonas syringae pv. tomato sonicated cells. The factor had an approximate molecular weight of 108 000, contained 90% protein and 10% polysaccharide, and was partially purified by affinity chromatography, gel chromatography, gel electrophoresis, and electrophoresis on cellulose acetate strips. The factor caused loss of electrolytes within 48 h and necrosis on bean, pepper, and cucumber leaves but not on tomato leaves of different cultivars. Similar fractions extracted from cells of P. fluroescens did not show any activity. Activity was destroyed by pronase or by hydrolysis with HCl indicating that the activity is due to the protein component. The factor did not show any pectolytic or cellulolytic activity. The factor was produced at a maximum after 24 h of growth of P. syringae pv. tomato and was more abundant when extracted from cells grown in rich medium.
The mycorrhizal dependency of four hardwood tree species
Authors: Pope P. E. , Chaney W. R. , Rhodes J. D. , Woodhead S. H.
Published: April 2011

Seedlings of four hardwood tree species were inoculated with six species of vesicular–arbuscular mycorrhizal fungi (Glomus mosseae, G. fasciculatum, G. etunicatum, G. macrocarpum, G. epigaeum, and Gigaspora margarita) and grown for 16 weeks in a soil low in available phosphorus. Mycorrhizal dependency values were greatest for Fraxinus pennsylvanica Marsh. followed by Liquidambar styraciflua L., Liriodendron tulipifera L., and Platanus occidentalis L. and were significantly influenced by the fungal species. For all tree species, inoculation with G. macrocarpum resulted in the highest mycorrhizal dependency values. An inverse correlation was observed between root fibrosity of noninoculated control plants and the mycorrhizal dependency values of each tree species.
Genetic load and long-distance dispersal in Asplenium platyneuron
Authors: Crist Kathryn Carvey , Farrar Donald R.
Published: April 2011

Solitary plants of Asplenium platyneuron occur disjunctively on recently produced coal spoils in southern Iowa. They are assumed to have been produced by self-fertilization of isolated gametophytes and therefore highly homozygous. Cultures of isolated and paired gametophytes originating from these solitary sporophytes produced second-generation sporophytes with 89 and 93% success, respectively, indicating a low genetic load as expected. The failure of gametophytes from coal-spoil plants to produce sporophytes with even greater success may result from homoeologous chromosome pairing and recombination at meiosis which allows production of variable spores and expression of genetic load from plants produced by self-fertilization of single gametophytes. Cultures of isolated and paired gametophytes originating from sporophytes in populations central to the species' range produced second-generation sporophytes with 83 and 90% success, respectively, indicating a significantly greater genetic load in populations but still a relatively low genetic load for the species. Through low genetic load, regularity of sporophyte production from isolated gametophytes, and ability of such plants to release variability through homoeologous chromosome pairing, Asplenium platyneuron is remarkably adapted for, and successful in, colonizing distant habitats through long-range spore dispersal.
Paleophycology of a high arctic lake near Cape Herschel, Ellesmere Island
Authors: Smol John P.
Published: April 2011

Fifty-five diatom taxa, representing mostly acidophilous and benthic species (e.g., Pinnularia biceps, Nitzschia bryophila, Navicula variostriata), were identified in a 56 cm long core from a small, deep lake (78°29.5′ N, 76°44.3′ W) in innermost Baird Inlet, Ellesmere Island, Arctic Canada. The size and composition of past algal populations appears to have been controlled by fluctuations in the extent of icefree conditions in the littoral zone. The development of planktonic diatoms may have been precluded by extended ice cover in the pelagic region, although planktonic chrysophytes (exclusive of the Synuraceae) were abundant throughout the lake's 9000 year history. Crysophycean success in this harsh environment is attributed to their versatile nutritional strategies, their motility, and their ability to form a good resting stage. Four fossil zones were delineated. Following the onset of organic sedimentation (~ 9000 years before present (BP)), the diatom flora was dominated by small Fragilaria species (zone 1), comparable to early postglacial communities from temperate lakes. A contemporary analog to this early assemblage was recorded in the surficial sediments of Proteus Lake (78°41.7′ N, 74°23.0′ W), on Pim Island, suggesting that these diatoms reflect slightly alkaline conditions and extended ice cover. As the climate warmed, the assemblage shifted to one dominated by Nitzschia bryophila and Pinnularia biceps (zone 2), followed by an increase in Navicula variostriata (zone 3), indicating that ice cover was at a minimum and that bryophytes were abundant. Climatic deterioration (~ 4000 years BP) coincided with a shift to a diverse assemblage of shallow water diatoms and a marked decline in chrysophyte and diatom populations (zone 4). These data suggest that, in arctic regions, diatoms may provide indirect information of past climates, since temperature is closely associated with habitat availability.
The avian seed dispersal system of eastern red cedar (Juniperus virginiana)
Authors: Holthuijzen Anthonie M. A. , Sharik Terry L.
Published: April 2011

The avian dispersal system of red cedar, a low-quality, fleshy, cone-producing, woody plant, was investigated in southwest Virginia over a 2-year period. The red cedar cones ripened from late August through early October and persisted on the trees through May of the next year. Predispersal cone predation amounted to 0.9 and 3.1% of the total cone crop in 1980–1981 and 1981–1982, respectively. The proportion of the cone crop removed by avian dispersers was constant from year to year despite large differences in crop size. Active dispersal took place between November and March. Eight species of avian dispersers were identified. Single consistent feeders, such as the yellow-rumped warbler, accounted for slow, sustained removal of red cedar cones, whereas flock feeders, such as the cedar waxwing, European starling, and American robin, were responsible for rapid removal of entire cone crops. Bird-passed seeds showed 1.5–3.5 times greater total germination than manually depulped seeds. Average dispersal efficiency, defined as the proportion of the cone crop dispersed away (≥ 12 m) from the parent tree, was 68%. The high dispersal efficiency of red cedar may be explained in part by the short duration of visits paid by avian dispersers to cone-producing trees, the high mobility of these dispersers, and the relatively long transit times for ingested seeds. High efficiency combined with enhanced germination of ingested seeds may promote the rapid invasion of abandoned pastures by red cedar in the southeastern United States.
Evidence for genetic control of oospore abortion in Phytophthora megasperma f. sp. glycinea
Authors: Rutherford F. S. , Ward E. W. B.
Published: April 2011

Levels of oospore abortion were determined in nine physiologic races of the soybean pathogen Phytophthora megasperma f. sp. glycinea. In five of the races, ratios of aborted to nonaborted oospores conformed to classical Mendelian ratios, consistent with diploidy in this species. Levels of abortion differed among races, providing a basis for selection of lines with low levels of oospore abortion.
Macrophomina phaseolina from guar in Arizona
Authors: Mihail J. D. , Alcorn S. M.
Published: April 2011

Macrophomina phaseolina (Tassi) Goid. is reported as a pathogen of guar in North America for the first time. Although M. phaseolina is seed borne in other crops, the fungus was not recovered from seeds of naturally infected guar plants. Since the pathogen is found in desert and cultivated soils throughout southern Arizona where concurrent heat and water stress favor disease development, charcoal rot should be considered a potential constraint to guar production in arid regions.
Canadian grass genera: keys and descriptions in English and French from an automated data bank
Authors: Watson L. , Aiken S. G. , Dallwitz M. J. , Lefkovitch L. P. , Dubé M.
Published: April 2011

An automated data bank for Canadian grass genera has been established in Ottawa under the DELTA system, capable of generating detailed taxonomic descriptions and identification keys in English and French. The descriptive information available comprises 274 characters, mainly concerned with morphology, anatomy, physiology, and geographic distribution. The present capabilities of the system are described and illustrated by automatically typeset sample keys to the 109 genera known to occur in Canada (in English) and to the taxa of the Yukon (in English) and to those of Québec (in French); by automatically typeset sample descriptions of the genus Festuca in computer-coded form (in English and in French); and by two microfiches carrying descriptions and keys for all the Canadian genera (in English and in French).
Genetics of Gibberella fujikuroi. VIII. Vegetative compatibility groups
Authors: Sidhu Gurmel S.
Published: April 2011

Gibberella fujikuroi (anamorph Fusarium moniliforme) mating group A isolates from corn and sorghum were categorized into different vegetative compatibility groups, using nit mutants (mutants unable to reduce nitrate or chlorate) to observe heterokaryosis among the compatible isolates. Vegetative incompatibility seems to be widespread in nature in this fungus and is controlled by nuclear genes called het or vic genes. A total of nine het genes were estimated for G. fujikuroi mating group A. Based on the independent segregation of nine het genes, 512 vegetative compatibility groups may be present in nature. However, only 13 vegetative compatibility groups were identified among conidial isolates recovered from Nebraska. The frequency of individual vegetative compatibility groups in a disease complex may be useful for monitoring pathogenicity genes in this fungus.
Mitosis and septum formation in the basidiomycete Helicobasidium mompa
Authors: Bourett Timothy M. , McLaughlin David J.
Published: April 2011

Mitosis in clampless, dikaryotic hyphae of Helicobasidium mompa (Basidiomycota, Auriculariales sensu lato) was studied in apical and penultimate cells by correlating light microscopic and ultrastructural observations. Mitosis lasts about 10.5 min. In penultimate cells, mitosis occurs in the base of a branch whose initiation involves rupture of the wall. The extranuclear interphase spindle pole body contains two three-layered discs. Prophase is discerned by the polarization of the nucleus into a karyokinetic and a nucleolar region. During prometaphase, the spindle pole body discs move into the plane of the nuclear envelope where they occupy gaps. The spindle pole is enclosed by a cap of endoplasmic reticulum. At metaphase, nuclei lie side by side, the nucleolus resides in a nuclear evagination, and the spindle pole body discs are five layered. At anaphase, both chromatin to pole movement and extensive spindle elongation occur, astral microtubule populations reach a maximum, and multivesicular bodies aggregate at the spindle poles. Septa contain simple pores and form at the site previously occupied by the dividing nuclei. The results are compared with mitotic cycles in higher fungi and their evolutionary, phylogenetic, and functional significance is discussed.
Nuclear behaviour and cell wall composition in relation to budding in mutants of the yeast Saccharomyces cerevisiae
Authors: Lachapelle Mario , Boothroyd E. Roger
Published: April 2011

A temperature-sensitive, cell division cycle mutant (cdc24–1) and karyogamy-deficient (kar1) mutant of Saccharomyces cerevisiae, both of which can produce binucleate or multinucleate cells, were used to study certain aspects of budding, after fluorescent staining for mannan, chitin, and nuclei (DNA). In most binucleate cells the two nuclei lay close together and divided into the same bud. In a few, however, the nuclei were far apart and one or two buds were formed, each proximal to a nucleus. The proximity of daughter nuclei in most blocked cdc24–1 cells suggests a role for the CDC24 gene product in spindle elongation. The relationship between the nuclei and the number and location of buds supports the theory of a preponderant role for the nucleus in budding. Although buds develop preferentially in regions of low chitin content in kar1 heterokaryons, the ability of cdc24–1 cells to bud even with a uniformly high content of chitin and mannan suggests a minor role for these cell wall constituents in determining the sites of bud emergence. The chitin ring is not needed for bud emergence but seems to play a role in normal bud development and in septum formation. Electron microscopy of cdc24–1 cells blocked (37 °C) for 8 h and released (23 °C) for 30 min showed morphologically normal spindle pole bodies, cytoplasmic microtubules, and intranuclear spindles. Although the chitin ring was absent, the ring of 10-nm filaments was present, consistent with its proposed role in bud emergence.
Vegetation patterns in James Bay coastal marshes. I. Environmental factors on the south coast
Authors: Ewing Kern , Kershaw K. A.
Published: April 2011

Coastal wetlands of the Hudson Bay Lowlands along southern James Bay are generated by a positive water balance, low relief, and a rising land surface. Marshes, dominated by sedges and grasses, and separated by beach ridges, occur between unvegetated intertidal flats and the inland boreal forest. Bay waters, affected by currents, shallow depths, and large freshwater inputs from major rivers in the Hudson Bay drainage, are brackish. Off the coast at the Harricanaw River, surface salinity in the bay is <4 ppt while soil water salinities in the adjacent marsh are higher. Standing water and tidal water in contact with vegetation often measure 0 ppt salinity. Plant communities adapted to brackish water have developed. Using two-way indicator species analysis classification, twelve widespread community types were recognized. Ordination using detrended correspondence analysis revealed gradients of salinity, elevation, drainage, vegetation development, complexity, and peat formation, and separated coastal from estuarine communities. An inverse salinity gradient, which has been reported elsewhere in James Bay, was not found; explanations are proposed for isolated areas of high salinity.
Phosphoglyceromutase activity and concentration in the endosperm of developing and germinating Ricinus communis seeds
Authors: Botha Frederik C. , Dennis David T.
Published: April 2011

Monospecific antiserum was raised in rabbits to phosphoglyceromutase isolated from the developing endosperm of Ricinus communis. The antiserum binds to both the plastid and cytosolic isozymes of this enzyme. Both isozymes have a relative molecular mass of 64 500 and are monomers. The large increase in phosphoglyceromutase activity that occurs during seed development and early seedling growth coincides with an increase in the phosphoglyceromutase concentration. Contradictory results were obtained with the enzyme-linked immunosorbent and Western blot assays during the later stages of seed maturation and early stages of seed germination. This is probably a result of a heterogeneous mixture of phosphoglyceromutase fragments, resulting from partial proteolysis of the enzyme during the drying of the seeds.
Conidial production of Verticillium dahliae as influenced by a negative pressure potential
Authors: Duncan D. R. , Himelick E. B.
Published: April 2011

When Verticillium dahliae Kleb. was grown under a negative pressure potential of −0.039 MPa, conidial production increased 800% over that of untreated control fungus. The increased production occurred when the fungus was grown on Czapek Dox broth, on sugar-maple sap, or on sugar-maple sap amended with asparagine. Fungal survival within a host is discussed in light of the data.
Physical properties and monoterpene composition of xylem oleoresin along the bole of Pinus taeda in relation to southern pine beetle attack distribution
Authors: Schmitt J. J. , Nebeker T. E. , Blanche C. A. , Hodges J. D.
Published: April 2011

Eight trees from each of four different age-classes (5–15, 16–25, 26–35, and 36–45 years) were sampled at 10 equally spaced heights along the bole for xylem oleoresin physical properties (initial flow rate, total flow, and viscosity) and monoterpene composition. Trees in the 36- to 45-year-old age-class had a significantly faster initial resin flow rate and greater total flow than trees from the other age-classes. No significant differences in initial flow rate, total flow, and relative viscosity were observed between sample heights. Unexpected differences in monoterpene composition occurred between age-classes. α-Pinene decreased and β-pinene increased with increasing height for all trees in all age-classes. Camphene decreased with increasing height in the 5- to 15-year-old age-class and β-phellandrene increased with increasing height in the age-classes of 16–25 and 26–35 years. No obvious xylem oleoresin properties at the different heights were observed that might suggest a favorable condition for southern pine beetle attack.