bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal growth patterns of ovulate strobili of Pinus resinosa in central Wisconsin
Authors: Dickmann D. I. , Kozlowski T. T.
Published: June 2008

Seasonal growth patterns and water balance of first- and second-year strobili and seeds of Pinus resinosa Ait. were studied. Strobili emerged from the bud in late May or early June and grew slowly during the first season, reaching approximately 1/40 the weight of mature strobili. After a rapid period of hydration which lasted until mid-June, the weight of water in first-year strobili remained stable, but percentage of moisture decreased, primarily because of increasing dry weight. Strobili resumed growth in mid-April of the second year and grew slowly until June. Then, at about the time that fertilization of ovules occurred, dry weight increment of strobili increased greatly until a final weight of 6 to 8 g was reached early in August. However, strobili reached final size in mid-July. After mid-June, both the weight of water and percentage of moisture of second-year strobili decreased greatly, reflecting characteristic dehydration of cones during maturation. Seeds increased rapidly in dry weight after fertilization, but decreased sharply in percentage of moisture and weight of water.Continuous monitoring of strobilus diameters with dendrographs showed that, during the first year, strobili expanded slowly and showed diurnal fluctuations in diameter during periods of water stress. Second-year strobili showed three growth phases: an initial phase characterized by net diameter increment; a second phase in which no large net diameter increment took place although diurnal fluctuations regularly occurred; and a third, dehydration, phase during which time strobilus diameters decreased, accompanied by diurnal contraction and partial reexpansion.
Forest microfungi. II. Additions to Acrodictys
Authors: Sutton B. C.
Published: June 2008

The brief history of Acrodictys M. B. Ellis is reviewed and two new species from rotting bark of Populus are described and illustrated. Acrodictys fuliginosa n. sp. is characterized by non-proliferating conidiophores and obovate, shining-black conidia with three transverse and three to six longitudinal septa. In Acrodictys excentrica n. sp. a succession of variably shaped shining-black conidia is formed from the long, readily proliferating conidiophores. Conidia are typically five-celled, one of the two apparently lateral pale brown inflated cells is the recurved apical conidium cell and the other is separated from the basal conidium cell by a longitudinal septum.
Chromosome numbers of some North American Arctic and Boreal Salix
Authors: Suda Yutaka , Argus G. W.
Published: June 2008

Chromosome numbers are reported for 12 native North American species of Salix and one natural hybrid. The arctic species Salix alaxensis var. alaxensis, S. fuscescens, S. ovalifolia var. ovalifolia, S. phlebophylla, and S. reticulata and the boreal species S. arbusculoides are diploids, 2n = 38. Tetraploid counts, 2n = 76, are reported for the arctic S. planifolia ssp. pulchra. Taxa with more than one chromosome number include S. planifolia ssp. planifolia and S. pedicellaris, each of which has tetraploid and triploid levels; S. arctica s.l., which is tetraploid in the eastern American arctic and hexaploid in the Alaska and Eurasian arctic; and S. athabascensis with triploid, tetraploid, and hexaploid levels. Intra-population variation in chromosome number is reported for S. glauca in which tetraploids, pentaploids, and hexaploids occur in a single Alaskan population.
Intraracial variation in Phytophthora infestans, and its relationship to different host varieties
Authors: Upshall Alan
Published: June 2008

A comparative study of the magnitude of growth rate variation among isolates of Phytophthora infestans (Mont.) de Bary taken from a high and a low field resistant variety of potato has shown it to be greater in the former than in the latter, even though both crops were infected by the same population of the pathogen. Competition between spores, and adaptation to the varieties, are put forward as possible alternative explanations.
Foliar nutrition and growth in red pine: the fate of photoassimilated carbon in a seedling tree
Authors: Rangnekar Pratap V. , Forward Dorothy F.
Published: June 2008

A 2- to 3-year-old red pine seedling was allowed to assimilate 14CO2 for 3 hours at 2000 ft-c and left under the same illumination for 6 days, then divided into segments and analyzed. Ethanol extracts were resolved by chromatography, insoluble residues by chemical methods. The radioactivity in various components was determined for all segments. Autoradiographs were made from stem sections at four levels.Radioactivity was found in all parts of the plant. Per unit mass of tissue, it was more or less uniformly apportioned among root, stem, and leaves, but the expanding terminal bud contained 5 times as much activity per gram of tissue. Overall, about one-third of the radioactivity was in insoluble compounds, mainly in cell wall constituents. In localities where conspicuous growth had occurred the proportion was higher. Autoradiographs of stem sections showed that 14C was concentrated in newly differentiated tracheids, and was still being incorporated after 6 days. About one-third of the activity in the ethanol extract was chloroform soluble, two-thirds water soluble. In the latter fraction, activity was largely in sugars and organic acids, little in amino acids. Activity in sugars, per unit weight of tissue, was more or less uniform throughout the plant, but activity in organic acids varied greatly. It was lowest in the stem, highest in the bud, where organic acids, almost exclusively quinic and shikimic, carried 75% of the label in the ethanol and water-soluble fraction, and 23% of all the activity in the bud.
Towards a mathematical model of limestone pavement vegetation. II. Microclimate, surface pH, and microtopography
Authors: Yarranton G. A. , Beasleigh W. J.
Published: June 2008

Microclimate and surface pH in limestone pavement fissures were investigated, with special attention to their correlation with topography. The diurnal cycles of light intensity at 60 points in the fissures were measured and variations in them explained by the interaction of topography and the position of the sun in the sky. Continuous recording of temperature and humidity in the grikes over a 5-day period suggested the presence of two air layers: an air layer in the lower two-thirds of each grike, characterized by stable temperature and humidity, with humidity decreasing upward; and a second layer continuous with the air above the surface and subject to much greater variation. This phenomenon was most pronounced in the narrowest grikes. Means and variances of light intensity, temperature, and humidity were selected as parameters of microclimate. Analyses of their variance with respect to topographic effects were performed, and all six parameters were shown to be highly correlated with topography. The pH determinations are not so correlated. The suitability of these seven variables for use in projected mathematical models of the determination of the probability of occurrence of species at defined points was investigated.
Studies on Rhizophydium and Phlyctochytrium (Chytridiales). I. Comparative morphology
Authors: Barr D. J. S.
Published: June 2008

Eight isolates of chytrids from soil were compared in culture. On pine pollen they initially appeared similar but in pure culture marked differences in rhizodial morphology were noted. One isolate is proposed as neotype material for Rhizophydium sphaerotheca Zopf. The others are described as four new species: R. capillaceum, Phlyctochytrium californicum, P. plurigibbosum, and P. acuminatum.
Studies on Rhizophydium and Phlyctochytrium (Chytridiales). II Comparative physiology
Authors: Barr D. J. S.
Published: June 2008

A physiological comparison was made of five species of soil chytrids. Phlyctochytrium californicum, P. plurigibbosum, and P. acuminatum could be distinguished from each other and from two species of Rhizophydium by their pH optima, their thiamine requirements, and their differential growth on nitrate, on nitrite, and on the carbohydrates fructose, trehalose, cellobiose, glycerol, and lactose. Temperature optima and ranges were as variable among isolates of species as between species. Rhizophydium sphaerotheca and R. capillaceum were physiologically similar and could only be separated on their ability to use nitrate and fructose.
Effect of relative humidity on production of extracellular pectolytic enzymes by Botrytis cinerea and Sclerotinia sclerotiorum
Authors: Berg L. Van Den , Yang S. M.
Published: June 2008

B. cinerea and S. sclerotiorum growing in a nutrient medium on the surface of carrots at 20 °C produced significantly more extracellular pectolytic enzymes when the carrots were exposed to 94–96% relative humidity than when exposed to 98–100% relative humidity. Tests in which these organisms were grown in a nutrient solution containing pectic substances showed that they produced pectolytic enzymes in significant quantities only when readily metabolizable sources of energy (e.g. ethanol, carbohydrates) were not available. These results suggest that the low relative humidity increased enzyme production by concentrating nutrients on the carrot surface to the point where they inhibited growth of the organisms and stimulated enzyme production. Tests also showed that pectolytic enzyme activity on the surface of unwashed carrots stored 9 months at 0–1 °C was substantially higher at 90–95% relative humidity than at 98–100% relative humidity. The results indicated that reduced decay at 98–100% relative humidity was largely due to lower pectolytic enzyme production.
Helotium resinicolum n. sp. and its Stilbella conidial state
Authors: Baranyay J. A. , Funk A.
Published: June 2008

A new species of Helotium, occurring on resin exudate of western conifers, is described and named Heliotum resinicolum Baranyay and Funk. It has a conidial state in Stilbella and its ascospores and conidia have been cultured on malt agar.
Microsite conditions and spatial pattern in a boreal bryophyte community
Authors: Frego Katherine A. , Carleton Terry J.
Published: June 2008

This study addresses the hypothesis that the spatial pattern of four bryophyte species on the forest floor of boreal woodland represents habitat partitioning, corresponding to microhabitat heterogeneity. Temperature, vapour pressure deficit, photosynthetically active radiation, incident precipitation, and litter fall were monitored at locations of pure colonies of Pleurozium schreberi, Ptilium crista-castrensis, Dicranum polysetum, and Ptilidium ciliare. From May through November 1990, the species received a mean total of 51.20 ± 1.09 cm of rain and 1.034 ± 0.639 g of litter, primarily spruce needles. They experienced temperatures as high as 40 °C, vapour pressure deficits to 7.3 kPa, and photosynthetically active radiation to 3200 μmol∙m−2∙s−1. The results do not support habitat partitioning by the species on the basis of the variables examined: all four species tolerated the full range of conditions and their combinations that occurred in the study season, and experienced the same ranges during > 90% of the sampling period, with equally broad within-species variation. Although large pure colonies of P. ciliare were delimited by microsites receiving greater spruce needle litter fall and lower incident precipitation per rainfall event, smaller colonies and individual shoots were often found in mixture with other species. Overall, the spatial pattern did not correlate with microsite conditions, and we see no evidence of habitat partitioning in terms of currently occupied microsites. Key words: community structure, microclimate, Pleurozium schreberi, Ptilium crista-castrensis, Dicranum polysetum, Ptilidium ciliare.
Effect of verticillium wilt on gas exchange of entire eggplants
Authors: Gent Martin P. , Ferrandino Francis J. , Elmer Wade H.
Published: June 2008

Verticillium dahliae infection may reduce growth and yield of eggplant (Solanum melongena L.) by inhibiting gas exchange per unit leaf area, and (or) by reducing leaf area. To quantify this inhibition, eggplants were grown in a field in fumigated soil or soil naturally infested with V. dahliae. Photosynthesis, dark respiration, transpiration, leaf area, disease symptoms, and yield were measured. Whole plants were enclosed in clear-walled chambers to measure gas exchange for 24-h periods. Before fruit set, there were no symptoms of wilt and no difference in leaf area or in gas exchange of plants grown in infested or fumigated soil. After fruit set, plants grown in the Verticillium-infested soil became symptomatic and had less leaf area, smaller leaves, and less photosynthesis per plant under high irradiance than plants grown in the fumigated soil. When whole plant gas exchange was normalized per unit leaf area there was no significant effect of disease on photosynthesis or transpiration. Although verticillium wilt reduces photosynthesis per unit leaf area in other species, our findings suggest that verticillium wilt reduced gas exchange of the entire eggplant predominantly by reduced leaf area rather than by reduced photosynthetic efficiency. Key words: Verticillium dahliae, Solanum melongena L., photosynthesis, transpiration, leaf area.
Demographics of pollen tube growth inCucurbita pepo
Authors: Winsor James A. , Stephenson Andrew G.
Published: June 2008

Pollen tube growth rates and pollen tube attrition were examined in Cucurbita pepo plants grown in an experimental garden. Two separate studies were performed utilizing controlled hand-pollinations. First, female flowers were hand-pollinated and collected at intervals over a 22-h period. Examination of stained pollen tubes in these pistils under reflected UV light revealed variation in growth rate: after approximately 7 h, the fastest growing pollen tubes grew at nearly twice the rate of the mass of the pollen tubes. The faster growing tubes reached the top of the ovary well ahead of most of the pollen tubes. Second, density of pollen application was varied and counts of germinated pollen and pollen tubes were made at four points from the stigmatic surface to the receptacle. Attrition was high for all pollen densities, but significantly higher rates occurred at high and medium densities just below the stigmatic surface. Pollen tube attrition at other points in the pistil was associated with constrictions in the stylar tissue and possibly with levels of nutrients in the pistil. Key words: Cucurbita pepo, pollen competition, pollen tube attrition.
A watershed level analysis of the lakeshore plant community
Authors: Holt Tanya Dolores , Hill Nicholas Morison , Blum Ilya
Published: June 2008

An investigation was conducted to determine whether the variables, standing crop and sediment organic matter content, related to species richness patterns at the local level, varied at the landscape level in accordance with differences in lake watershed area. Previous study had demonstrated the importance of watershed area as a predictor of species richness of all herbs and of rarities, in particular, on lakeshores. In this study, the reciprocal of watershed area (log units) accounted for over 75% of the variation in biomass at above and below summer waterline positions. Furthermore, watershed area accounted for most of the variation in sediment organic matter content. Above the waterline, shrubs were the predominant growth form at lakes with small watershed areas; the reciprocal of watershed area accounted for 92% of shrub biomass variation. Shoreline plant communities on the lowest watershed area lake were high-biomass, shrub assemblages above waterline and low-biomass, graminoid communities below the waterline. In contrast, above the waterline but below the upper shrub zone on the high watershed area lake, shorelines supported low-biomass assemblages composed of a mixture of shrubs, graminoids, forbs, and ferns. The strong relationships found here between biomass and organic matter and lake watershed area reconcile predictive models made at the within-lake level with those made at the landscape level. Key words: watershed area, landscape models, species richness, community biomass, lakeshores.
Warm plus cold stratification requirement for dormancy break in seeds of the woodland herb Cardamine concatenata (Brassicaceae), and evolutionary implications
Authors: Baskin Carol C. , Baskin Jerry M.
Published: June 2008

At maturity in mid-May, the physiologically dormant seeds of Cardamine concatenata have fully developed embryos; 59.2% of those sown in a nonheated greenhouse in May germinated the following late February to mid-April. Maximum germination occurred from 7 to 14 March, when mean daily maximum and minimum air temperatures were 14.8 and 3.3 °C, respectively. No additional seeds germinated in two subsequent springs, indicating lack of ability of this species to form a persistent seed bank. Seeds receiving only a cold stratification period germinated to 98% after 28 weeks at 5 °C, whereas those given a warm-stratification pretreatment of 4 weeks at 30:15 °C (max–min) germinated to 100% after only 18 weeks at 5 °C. In the field, warm stratification during summer and autumn would reduce the length of the cold-stratification period required to break dormancy, and thus allow dormancy to be broken during winter. This is only the second report of a woodland herb having physiologically dormant seeds with fully developed embryos that require warm plus cold stratification to germinate in spring. We hypothesize that this requirement for dormancy break could have evolved from ancestors whose seeds required only a period of warm stratification to emerge from dormancy. Key words: germination, seed dormancy, warm stratification, cold stratification, woodland herb.
An integrated approach, using biological and chemical control, to prevent blue stain in pine logs
Authors: Behrendt Chad J. , Blanchette Robert A. , Farrell Roberta L.
Published: June 2008

Biological control of detrimental blue stain fungi has been demonstrated in field experiments using a nonpigmented strain of Ophiostoma piliferum, Cartapip-97™, to inoculate logs. In two field trials 78–97% and 95–99% of wood chips sampled from the sapwood yielded the nonpigmented strain of O. piliferum (NPOP) 8 weeks after inoculation. Wood chip isolations yielding blue stain fungi from the sapwood in noninoculated treatments after 8 weeks ranged from 53 to 83% during the first field trial and 6 to 31% during the second, whereas isolations from NPOP-inoculated treatments ranged from 0 to 3% in the first trial and 0% in the second trial. Phanerochaete gigantea had also colonized the sapwood of all treatments by 24 and 52 weeks, with 20–93% of chip samples in field trial one yielding P. gigantea, and 54–99% for field trial two. Effective control of bark beetles was demonstrated with applications of Dursban 4E. Bark beetle colonization in Dursban-treated logs was less than 3%, a 9–47% decrease when compared to other treatments. Successful control of blue stain fungi appears possible by treating the ends of freshly cut timber with the nonpigmented strain of O. piliferum and spraying logs with Dursban 4E to prevent bark beetles from introducing stain fungi into the sides of logs. Key words: biological control, sapstain, Ophiostoma piliferum, Phanerochaete gigantea, Scolytidae.
Pattern and vegetation–environment relationships in a boreal forested wetland in northeastern Ontario
Authors: Jeglum John K. , He Fangliang
Published: June 2008

A forested wetland data set from northeastern Ontario, consisting of species cover and environmental measures in 43 stands, was analyzed with canonical correspondence analysis. Results showed two main vegetational gradients related to factor complexes of peat depth – moisture (mire margin to mire expanse) and pH–calcium. Stands within each of the vegetation types were positioned closely, and gradients of types were similar to those from earlier analyses, suggesting the validity of a previous classification. Axis I of the ordination was highly related to peat depth, several elements (Al, Fe, and Cu), loss on ignition, bulk density, and water content in peat. Axis II was highly related to loss on ignition, depth of fibric layer, pH, and several elements (Ca, Mg, Mn, and N). The number of species in a plot was strongly correlated to the pH–calcium gradient, whereas vegetation cover was strongly correlated to the peat depth – moisture gradient. Analysis with detrended correspondence analysis gave results very similar to canonical correspondence analysis, suggesting that there was a relatively high correspondence between vegetational and environmental gradients. Environmental measures were partitioned into physical and chemical attributes, to detect the relative contribution to vegetational variation. Both physical and chemical variables were important, and 81% of the variation in vegetation was explained by the environmental measures. Key words: boreal forest, multivariate analysis, Ontario, wetlands, vegetation pattern, diversity.
Postglacial development of a Maine bog and paleoenvironmental implications
Authors: Hu Feng Sheng , Davis Ronald B.
Published: June 2008

Stratigraphic data on gross peat components, plant macrofossils, pollen, ash after ignition, and radiocarbon ages are used to reconstruct the developmental history of the north unit of Caribou Bog in central Maine, which presently consists of a sparsely wooded, ombrotrophic (raised), center surrounded by extensive wooded fen. A lake existed from 12 500 to 8500 BP, when terrestrialization led to peatland initiation throughout the basin within ~500 years. Near the center of the present peatland, limnic sedge fen developed to sedge fen at 8000 BP, and to Larix laricina wooded fen at 7000 BP. At 5500 BP the wooded fen became Sphagnum dominated and sparsely wooded, a condition that has persisted at the peatland center. Only two early transitions are clearly related to climate forcing. An abrupt shift from silt–clay to organic lake sediment ~10 400 BP is typical of basins throughout the region. This shift correlates with rapid changes in local and regional vegetation, and likely reflects increased biological productivity caused by a rapid warming of climate. Peatland initiation 8500–8000 BP coincides with a drop of water level, probably associated with a rapid shift to drier climate. We estimate that the water level around the peatland was at least 0.4 m above the present level at and before 8500 BP, dropped at least 1.7 m (min. 1.4 m with correction for peat compaction) in the next 500 years, and rose to the present level around 7000 BP or later. Major hydroseral changes after 8000 BP are asynchronous at several coring sites and are not consistently correlated with regional paleoclimatic events. These changes were probably induced by autogenic hydrological processes associated with peat accumulation. Key words: wetland history, paleoclimate and paleohydrology, pollen, plant macrofossils, peat stratigraphy, Maine.
Functional morphology and homologies of gymnospermous ovules: evidence from a new species of Stephanospermum (Medullosales)
Authors: Serbet Rudolph , Rothwell Gar W.
Published: June 2008

Fifteen specimens of a new species of medullosan ovules, Stephanospermum tridentatum sp.nov., have been discovered in Upper Pennsylvanian coal balls collected near Steubenville, Ohio. These ovules are most similar to S. elongatum, but consistent differences in sarcotestal vascularization, ovule shape, number of buttresses that connect the crown to the micropylar beak, and number of teeth at the apex of the crown demonstrate that they represent a new species, S. tridentatum. Our knowledge of reproductive biology in medullosan seed ferns is enhanced by features of the pollen chamber and micropyle in the new species. The pollen chamber is campanulate and displays a cutinized epidermal layer, a nucellar beak, and a membranous floor. A mass of tissue in the position of a central column is preserved in one specimen. In contrast with ovules of living gymnosperms, the micropyle remains open following pollination. These specimens provide new data for characterizing postpollination closing mechanisms in early seed plant ovules and for interpreting sequences of character originations that were associated with the evolution of modern spermatophyte reproduction. Key words: medullosan, Stephanospermum, ovule, pollination biology.
Le Stigmidium lecidellae sp.nov. et remarques sur le genre Stigmidium (champignons lichénicoles non lichénisés, Ascomycètes)
Authors: Roux Claude , Bricaud Olivier , Coeur Didier Le , Triebel Dagmar
Published: June 2008

Stigmidium lecidellae Triebel, Roux et Le Coeur sp.nov., a mild pathogenic lichenicolous fungus growing on the apothecia of Lecidella elaeochroma (Ach.) M. Choisy is described in detail and compared with other species of Stigmidium that grow on the apothecia of the host. The staining of parts of cell walls with cresyl blue is constant at species level and, therefore, is taxonomically relevant in the genus Stigmidium. The dye also allows to distinguish some ultrastructural details of the vegetative hyphal cells, asci, and ascospores. Among the fungi species growing on the apothecia of lichens, three groups are distinguished on the basis of their hamathecial structure, one of which should be excluded from the genus Stigmidium and included in the genus Sphaerellothecium. A key to the determination of the species is presented. Key words: lichenicolous fungi, Stigmidium, Sphaerellothecium, taxonomy, taxonomic key, cell wall, staining reactions, hamathecium.
Seed germination, seedling demography, and growth of Salix setchelliana on glacial river gravel bars in Alaska
Authors: Douglas D. A.
Published: June 2008

This study examines the recruitment from seed of Salix setchelliana Ball, a prostrate clonal willow, which grows in the gravel-bar habitat of glacial rivers in Denali National Park, Alaska. Seeds of this species did not exhibit any dormancy. Under laboratory conditions, seeds moistened immediately after collection showed 100% germination, and percent germination decreased with an increase in the length of dry storage. Since summer precipitation is generally frequent in this region, this is probably not a factor limiting recruitment. Most seedlings observed in the field were located on gravel bars with greater plant cover, as opposed to those with sparse plant cover. The survivorship of seedlings over their first winter averaged 11%; in comparison, yearly survivorship in years 1–6 averaged 69%. The most likely cause of mortality was insufficient carbohydrate accumulation. Seedling leaf area differed between years and locations. An inverse relationship was found between leaf area and age-class for seedlings of younger age-classes. Key words: alpine, clonal, recruitment.
Rainbow Trout (Salmo gairdneri) Growth Hormone: in vitro Translation of Pituitary RNA and Product Analysis
Authors: Agellon L. B. , Chen T. T. , Beneden R. J. Van , Sonstegard R. A. , Wagner G. F. , McKeown B. A.
Published: June 2008

We have used RNA blot analysis, in vitro translation, and protein immunoblot analysis to characterize mRNA in the pituitary glands of rapidly growing rainbow trout (Salmo gairdneri). Cell-free translation products of total RNA, analyzed by direct immunoprecipitation or western immunoblot analysis with an antiserum to chum salmon (Oncorphynchus keta) growth hormone (GH), indicate that rainbow trout pregrowth hormone (pre-GH) is a polypeptide of 25 000 Da. RNA blot analysis of total pituitary RNA to its cDNA, using total liver RNA as a competitor, revealed the presence of at least four size classes of pituitary mRNA sequences. One class, with a size smaller than 18S rRNA, is the predominant mRNA component. By in vitro translation and western immunoblot analysis, the pre-GH mRNA activity is associated with this class of mRNA sequences. These results suggest that rainbow trout pre-GH mRNA is in the same size range as that of mammalian GH mRNA.
Sediment Diatom and Metal Stratigraphy from Rocky Mountain Lakes with Special Reference to Atmospheric Deposition
Authors: Baron Jill , Norton Stephen A. , Beeson David R. , Herrmann Raymond
Published: June 2008

We addressed the hypothesis that current levels of acidity in precipitation falling on Rocky Mountain National Park, USA, are greater than historical levels. Sediment cores from four subalpine lakes were sectioned and dated with 210Pb. The stratigraphic records of metals were used to detect trends in the deposition of Pb, Cu, Zn, and V because these metals are known to increase in areas receiving air masses polluted with fossil-fuel emissions. Diatom assemblages over time were used as indicators of change in lake water chemistry. Reconstructions of pH from four lakes were prepared using Index B, Index α, and predictive equations derived from an additional 19 lake surface sediments. The metal stratigraphy, diatom stratigraphy, and inferred pH profiles of the four study lakes indicate no historical influence on pH attributable to atmospheric deposition. Common to all four cored lakes, however, is a persistent increase in the deposition rate of Pb starting in the period between 1855 and 1905. The most likely source of the Pb is airborne particules from mining activity in Colorado which began in the mid-1800s. Recent high levels of Pb within the sediments may be due in part to emissions related to automotive leaded gasoline combustion.
Impact of Pulse Exposure to Methoxychlor on Flagfish (Jordanella floridae) Over One Reproductive Cycle
Authors: Holdway D. A. , Dixon D. G.
Published: June 2008

A 7.5- to 15-min pulse [Formula: see text] of the insecticide methoxychlor is currently used to control larval emergence of the blackfly (Diptera: Simuliidae) in several river systems of western Canada. Our chronic life-cycle study with flagfish (jordanella floridae) tested whether pulse exposure to methoxychlor would alter either the survival, wet weight gain, and reproduction of first-generation fish, or the survival and wet weight gain of their offspring. Flagfish were pulse exposed for 2 h to 0, 0.25, 0.70, 1.84, or 4.00 mg methoxychlor∙L−1either once, at 8 d of age, or twice, at 8 and 71 d of age. While mortality and wet weight gain were inconsistent indicators of methoxychlor impact, reproductive characteristics were highly sensitive. Mean daily egg production, total egg production, and time to steady spawning of first-generation fish, as well as hatchability and incidence of abnormalities in their offspring, were all adversely affected by a single 2-h exposure of 8-d-old juveniles to concentrations of methoxychlor ≥ 0.25 mg∙L−1(0.0065 of the 96-h pulse-exposure LC50). Therefore, juvenile fish in methoxychlor-treated rivers are at greater risk than would be indicated by continuous exposure experiments. Estimates of the impacts of short-term high-level pulse exposures extrapolated from continuous exposure studies appear to severely underestimate toxicity.
Effect of Point and Diffuse Source Loadings on Mercury Concentrations in the Wabigoon River: Evidence of a Seasonally Varying Sediment–Water Partition
Authors: Parks J. W. , Sutton J. A. , Lutz A.
Published: June 2008

Ten years after major mercury loadings from a chlor-alkalai plant were sharply reduced, mercury levels in the surface sediments, water, and suspended sediments of the Wabigoon River downstream of Dryden, Ontario, remain markedly elevated. During 1979, a typical water year, average mercury concentrations in water throughout an 80-km reach were nearly five times the mean value at the control site. Elevated mercury levels in the Wabigoon River are primarily due to the chemical and biological remobilization of mercury from sediments. Lesser amounts are due to the erosion of mercury-enriched sediments during high flows and to current releases from the mill site at Dryden. In the absence of resuspended sediment during high flows, mercury levels in contaminated waters can be best described by a sediment – water – suspended solids partition. This condition was established within half a day in the most contaminated portion of the system. Mercury concentrations in water can fluctuate seasonally by an order of magnitude. Highest concentrations were associated with elevated summer temperatures.
Oocyte Maturation and Spawning in Wild American Lobsters (Homarus americanus): Lack of Evidence for Significant Regulation by Photoperiod
Authors: Aiken D. E. , Waddy S. L.
Published: June 2008

The literature indicates that spawning in the American lobster (Homarus americanus) requires exposure to short days followed by long days, but our previous experiments with mature female lobsters showed no such requirement. To reevaluate the reported photoperiod requirement and to determine whether a photoperiod stimulus for ovarian maturation might occur well before the current spawning season, we held wild-caught mature Gulf of St. Lawrence females on either long (LD 16:8) or short (LD 1:23) days starting at the autumnal equinox. Females held on both short and long days spawned at the normal time the following July, indicating no effect of photoperiod even 10 mo before normal spawning time. This study extends previous work by showing that Gulf of St. Lawrence lobsters held on typical East Coast seawater temperatures will spawn at the normal time without being exposed to either short-day or long-day photoperiod between 22 September and the following July.
Opioid-induced regulation of µ-opioid receptor gene expression in the MCF-7 breast cancer cell line
Authors: Gach Katarzyna , Piestrzeniewicz Mariola , Fichna Jakub , Stefanska Barbara , Szemraj Janusz , Janecka Anna
Published: June 2008

The aim of the study was to investigate the presence of opioid receptor types in human breast adenocarcinoma MCF-7 cells and to characterize the changes in MOR expression induced by opioid agonist and antagonist treatment. We have shown that all three types of opioid receptors, but predominantly MOR, are expressed in MCF-7 cells. Selective MOR agonists, morphine, endomorphin-1, and endomorphin-2 downregulated MOR mRNA levels in a concentration- and time-dependent manner, but the effect produced by endomorphins was much stronger. Downregulation was blocked by the opioid antagonist naloxone. Naloxone alone produced a slight increase in MOR gene expression. Immunoblotting with antiserum against MOR-1 confirmed these results at the protein level. The results of our study indicate that, in MCF-7 cells, MOR gene expression is downregulated by opioid agonists and upregulated by opioid antagonists. We propose that the opioid-induced regulation of MOR mRNA expression is mediated by reduced binding of the transcription factors NFκB and AP-1 to the promoter region on the MOR gene.
The role of expansion segment of human ribosomal protein L35 in nuclear entry, translation activity, and endoplasmic reticulum docking
Authors: Chen In-Jay , Wang I-Ann , Tai Lin-Ru , Lin Alan
Published: June 2008

The phylogenic alignment of homologous L35 protein suggests that human large subunit ribosomal protein L35 carries a 54 aa eukaryotic expansion segment (ES) at the C-terminal end. Within this ES, the first 25 amino acid residues were found to be essential for the nuclear import of the protein. The last 29 residues of the ES were shown to be uninvolved in the ribosome’s structural and translational functions, although this region proved to be one of the contact sites for ribosomal docking to endoplasmic reticulum, as evident from the results of an in vivo recombinant ribosome analysis.
Downregulation of integrins by von Hippel-Lindau (VHL) tumor suppressor protein is independent of VHL-directed hypoxia-inducible factor alpha degradation
Authors: Ji Qingzhou , Burk Robert D.
Published: June 2008

Inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene occurs in the majority of clear-cell renal cell carcinomas (RCCs). It was previously shown that VHL decreased the abundance of integrins α2, α5, and β1, which is consistent with VHL-associated changes in cell–cell and cell – extracellular matrix adhesions. We investigated the mechanism by which VHL downregulates integrins. Although VHL can target hypoxia-inducible factor alpha (HIFα) subunits for degradation, VHL-dependent reduction of integrins was independent of O2 concentration and HIFα levels. VHL reduced the half-lives of integrins, and this activity was blocked by proteasomal inhibition. Although ectopically expressed FLAG-VHL retained HIFα degradation activity, it neither downregulated integrins nor promoted adherens and tight intercellular junctions, in contrast to expressed wild-type VHL. Moreover, integrins co-immunoprecipitated with wild-type VHL, but not FLAG-VHL. These data indicate that the downregulation of integrins by VHL is distinct from the regulation of HIFα subunits by VHL, and suggests that the loss of this activity contributes to VHL-associated RCC development through disruption of adherens and tight junctions.
Elevated serum β-glucuronidase reflects hepatic lysosomal fragility following toxic liver injury in rats
Authors: George Joseph
Published: June 2008

The level of serum β-glucuronidase increases in various pathological conditions, including liver disorders. The aim of this investigation was to study the changes in liver lysosomal membrane stability during experimentally induced hepatic fibrosis that may result in the elevation of serum β-glucuronidase. Liver injury was induced by intraperitoneal injections of N-nitrosodimethylamine (NDMA) in adult male albino rats over 3 weeks. The progression of fibrosis was evaluated histopathologically as well as by monitoring liver collagen content. Lipid peroxides and β-glucuronidase levels were measured in the liver homogenate and subcellular fractions on days 0, 7, 14, and 21 after the start of NDMA administration. Serum β-glucuronidase levels were also determined. A significant increase was observed in β-glucuronidase levels in the serum, liver homogenate, and subcellular fractions, but not in the nuclear fraction on days 7, 14, and 21 after the start of NDMA administration. Lipid peroxides also increased in the liver homogenate and the lysosomal fraction. The measurement of lysosomal membrane stability revealed a maximum lysosomal fragility on day 21 during NDMA-induced fibrosis. In vitro studies showed that NDMA has no significant effect on liver lysosomal membrane permeability. The results of this investigation demonstrated that lysosomal fragility increases during NDMA-induced hepatic fibrosis, which could be attributed to increased lipid peroxidation of lysosomal membrane. In this study, we also elucidated the mechanism of increased β-glucuronidase and other lysosomal glycohydrolases in the serum during hepatic fibrosis.
Responses of loblolly pine to ozone and simulated acidic rain
Authors: Reinert R.A. , Shafer S.R. , Eason G. , Horton S.J. , Schoeneberger M.M.
Published: June 2008

Acidic rain and ozone (O3) may have serious consequences on the growth and development of loblolly pine (Pinustaeda L.), a tree species of major economic importance in the southeastern United States. In two independent studies, seedlings of open-pollinated families of loblolly pine were exposed to five concentrations of O3 (0, 80, 160, 240, or 320 nL•L−1) and three simulated rain acidities (pH 5.3, 4.3, or 3.3). Following 23 weeks of growth (12 weeks in charcoal-filtered air and 11 weeks of O3 and simulated acidic rain exposures), stem height, secondary needle dry weight, top and total seedling dry weight, and root/shoot dry weight ratio all were related negatively and linearly with O3 concentration. Stem diameter and root dry weight were also suppressed by O3. Suppression of the growth parameters ranged from 14 to 35% for the greatest O3 concentration. Acidity of simulated rain did not affect seedlings, nor did it affect seedling responses to O3. Results indicate that acid rain probably has little effect on growth of loblolly pine seedlings, but O3 can suppress growth to varying degrees depending on family.
Influence of social status on crown geometry and volume increment in regular and irregular black spruce stands
Authors: Raulier Frédéric , Ung Chhun-Huor , Ouellet Denis
Published: June 2008

A model of bole volume increment based on crown dimensions and tree social status is analyzed for its ability to predict bole volume increment independently of stand structure. Data were collected in two boreal black spruce (Piceamariana (Mill.) BSP) stands in Quebec. One stand is even-aged and of seed origin, and the other stand is uneven-aged and of layer origin. A varying parameter approach is taken to show that the crown profile of black spruce depends on competition. Formal expressions for crown surface area and volume are developed from the crown profile and are used to derive a potential growth function for bole volume. Three social status indices are considered to characterize competition experienced by a subject tree: a distance-dependent competition index relating differences of height between the tree and its neighbors to the distance separating them, and two distance-independent indices, one based on tree height relative to dominant stand height and one based on height growth relative to potential height growth of a competition-free tree. These indices are combined with the potential growth function to successfully model bole volume increment. Both stands have an equal weight in the unexplained residual variance. Furthermore, all three social status indices perform equally well at predicting bole volume increment. The use of a potential growth function with crown parameters is further discussed.
Latitudinal variation in sugar maple fine root respiration
Authors: Burton Andrew J. , Pregitzer Kurt S. , Zogg Gregory P. , Zak Donald R.
Published: June 2008

A changing global climate may impact the respiration of fine roots. While many models adjust fine root respiration as temperature increases, the influence of soil nutrient availability and the possibility that root respiration may be adapted to local climate are often not addressed. Rates of fine root respiration were measured in four sugar maple (Acersaccharum Marsh.) forests located along a latitudinal gradient in Michigan. Root respiration was measured as O2 consumption at temperatures ranging from 6 to 24 °C on excised fine root samples in early September, October, and November of 1994. Root respiration increased exponentially with temperature with an average Q10 of 2.7; there were no differences in Q10 among sites. However, there were differences among sites in mean respiration rate at a given temperature. This site effect did not indicate ecotypic adaptation to local climate, but rather reflected fine root N concentration. Respiration at a given temperature was consistently higher in roots with higher N concentrations, and higher root N concentrations always occurred at sites having greater N mineralization rates. Results suggest increases in soil temperature could significantly alter root respiration C flux at these sites, as could changes in site N availability associated with chronic N deposition or altered N mineralization resulting from global climate change.
Effects of desiccation on temperate recalcitrant seeds: differential scanning calorimetry, gas chromatography, electron microscopy, and moisture studies on Quercusnigra and Quercusalba
Authors: Connor K.F. , Bonner F.T. , Vozzo J.A.
Published: June 2008

Investigations into the nature of desiccation-sensitive, or recalcitant, seed behavior have as yet failed to identify exact causes of this phenomenon. Experiments with Quercusnigra L. and Quercusalba L. were conducted to examine physiological and biochemical changes brought about by seed desiccation and to determine if there were predictable changes in seed moisture content, in enthalpy (heat content) of seed moisture, in the lipid fraction, or in seed ultrastructure as viability declined. Quercusnigra intact acorn moisture contents at 50% and 5% viability were 15% and less than 14%, respectively; those of intact Q. alba at 50% and 0% viability were much higher, 32% and 22%, respectively. Generally, it was found that as the seeds of both species dried, the moisture content of the axes remained high (26–27%), even after 9 days of drying. In Q. nigra acorns, there was little difference in average percent moisture lost per day among axes, proximal cotyledon tissue, and distal cotyledon tissue. Quercusalba acorns, however, lost moisture more rapidly from the axes than from the cotyledons. This was probably caused by the longitudinal splitting of the pericarp during the drying process. Lipids composed 28.4% of the dry weight of Q. nigra and 5.7% of Q. alba dry weight. Neither individual fatty acids nor total fatty acid content exhibited definite patterns of change over the course of the experiment. The most prevalent saturated fatty acid in both species was palmitic acid, and the most common unsaturated fatty acid was generally oleic acid. Electron microscopy studies of Q. nigra showed cell wall trauma after 3 days of drying (moisture content 23%); by day 7, when moisture content had dropped to 15.6%, there was a definite dissolution of cytoplasmic density and a reduction of spherosome concentration. Quercusalba exhibited similar responses to drying, but cell wall integrity was maintained. Differential scanning calorimetry studies revealed strong relationships between onset and enthalpy values of all acorn tissues and percent germination, as did regressions involving moisture content and seed germination.
Genetics of fall and winter cold hardiness of coastal Douglas-fir in Oregon
Authors: Aitken S.N. , Adams W.T.
Published: June 2008

Genetic variation in fall cold hardiness was studied in two western Oregon breeding populations of coastal Douglas-fir (Pseudotsugamenziesii var. menziesii (Mirb.) Franco), one on the west slope of the Cascade Mountains and the other in the Coast Range. On six sampling dates (September, October, and November of 1992 and January, September, and October of 1993), shoot cuttings from 40 open-pollinated families in each of two progeny test sites for each breeding zone were subjected to artificial freezing at two test temperatures. Damage on each shoot was recorded as visible injury to needle, stem, and bud tissues separately. Considerable family variation was found for cold injury scores in all tissues in early fall to midfall, but differences were often smaller or nonsignificant in late fall and midwinter. Individual heritability estimates for needle cold injury were low (<0.40) and generally decreased in late fall and midwinter. Family rankings for fall cold hardiness, however, are expected to be relatively consistent over sites and years, although needles appear to display more family-by-site interaction than stems or buds. Genetic correlations between tissues in cold injury varied considerably and were sometimes weak, indicating that the evaluation of a single tissue is probably not adequate for assessing overall cold hardiness of genotypes. Fall and winter cold hardiness seem to be largely under separate genetic control since genetic correlations between hardiness at these two stages were weak. This study confirms earlier results in Washington breeding populations and shows that coastal Douglas-fir families can be effectively ranked for fall cold hardiness by conducting artificial freeze tests on cut shoots in midfall (October) and scoring damage to stems and at least one other tissue.
The optimal rotation of a flammable forest stand
Authors: Martell D. L.
Published: June 2008

The author describes a stochastic model of forest stand rotation which can be used to determine the optimal planned rotation interval for flammable forest stands. The model can also be used to estimate the value of fire management activities in terms of the potential enhanced value of timber production. The use of the model is illustrated by applying it to a simplified case of jack pine (Pinusbanksiana, Lamb.) management.