bluuebunny/crossref_metadata_2025 huggingface dataset:
Mouse Mammary Tumor Virus Integration Site Selection in Human and Mouse Genomes
Authors: Faschinger Alexander , Rouault Francoise , Sollner Johannes , Lukas Arno , Salmons Brian , Günzburg Walter H. , Indik Stanislav
Published: November 2007

Based on integration site preferences, retroviruses can be placed into three groups. Viruses that comprise the first group, murine leukemia virus and foamy virus, integrate preferentially near transcription start sites. The second group, notably human immunodeficiency virus and simian immunodeficiency virus, preferentially targets transcription units. Avian sarcoma-leukosis virus (ASLV) and human T-cell leukemia virus (HTLV), forming the third group, show little preference for any genomic feature. We have previously shown that some human cells sustain mouse mammary tumor virus (MMTV) infection; therefore, we infected a susceptible human breast cell line, Hs578T, and, without introducing a species-specific bias, compared the MMTV integration profile to those of other retroviruses. Additionally, we infected a mouse cell line, NMuMG, and thus we could compare MMTV integration site selection in human and mouse cells. In total, we examined 468 unique MMTV integration sites. Irrespective of whether human or mouse cells were infected, no integration bias favoring transcription start sites was detected, a profile that is reminiscent of that of ASLV and HTLV. However, in contrast to ASLV and HTLV, not even a modest tendency in favor of integration within genes was observed. Similarly, repetitive sequences and genes that are frequently tagged by MMTV in mammary tumors were not preferentially targeted in cell culture either in mouse or in human cells; hence, we conclude that MMTV displays the most random dispersion of integration sites among retroviruses determined so far.
Maternal exposure to water disinfection by-products during gestation and risk of hypospadias
Authors: Luben T J , Nuckols J R , Mosley B S , Hobbs C , Reif J S
Published: November 2007

Background:

The use of chlorine for water disinfection results in the formation of numerous contaminants called disinfection by-products (DBPs), which may be associated with birth defects, including urinary tract defects.

Methods:

We used Arkansas birth records (1998–2002) to conduct a population-based case-control study investigating the relationship between hypospadias and two classes of DBPs, trihalomethanes (THM) and haloacetic acids (HAA). We utilised monitoring data, spline regression and geographical information systems (GIS) to link daily concentrations of these DBPs from 263 water utilities to 320 cases and 614 controls. We calculated ORs for hypospadias and exposure to DBPs between 6 and 16 weeks’ gestation, and conducted subset analyses for exposure from ingestion, and metrics incorporating consumption, showering and bathing.

Results:

We found no increase in risk when women in the highest tertiles of exposure were compared to those in the lowest for any DBP. When ingestion alone was used to assess exposure among a subset of 40 cases and 243 controls, the intermediate tertiles of exposure to total THM and the five most common HAA had ORs of 2.11 (95 CI 0.89 to 5.00) and 2.45 (95 CI 1.06 to 5.67), respectively, compared to women with no exposure. When exposure to total THM from consumption, showering and bathing exposures was evaluated, we found an OR of 1.96 (95 CI 0.65 to 6.42) for the highest tertile of exposure and weak evidence of a dose–response relationship.

Conclusions:

Our results provide little evidence for a positive relationship between DBP exposure during gestation and an increased risk of hypospadias but emphasise the necessity of including individual-level data when assessing exposure to DBPs.
Nitrogen fixation in forests of central Massachusetts
Authors: Tjepkema John
Published: November 2007

The acetylene reduction method was used to measure nitrogen fixation in soil cores of 16 cm diameter and 16 cm depth that included A and B horizon soil, roots, and decaying litter. Forty-three combinations of location and associated tree species were sampled. The rate of nitrogen fixation for most soil cores was 1 g N ha−1 day−1 or less, which extrapolates to less than 0.2 kg N ha−1 year−1. The highest rates, with values of up to 23 g N ha−1 day−1, were observed in old fields being invaded by trees. The time course of acetylene reduction was usually linear for a 24-h period, most of the activity was in the upper 15 cm of soil, and the maximum rates were observed in midsummer. No significant nitrogen fixation was observed in preliminary measurements of decaying woody litter or of aerial surfaces of trees and rocks. It is suggested that nitrogen fixation is not a significant input of nitrogen for the forests studied. If so, there may be significant unrecognized nitrogen inputs to forests, such as dry absorption of ammonia from the atmosphere.
Association of an irreversible reduction in urea permeability with osmotic factors during the ageing of excised squash hypocotyls
Authors: Hancock J. G.
Published: November 2007

After ageing in water for 4 to 5 h, the permeability of excised squash hypocotyl sections to urea, as measured in hypotonic solutions, had declined to about 50% of freshly excised tissues. This degree of change was common to several members of the cucurbit family. The permeability change was relatively temperature insensitive and was not closely linked to segment length. It was unaffected by puromycin, cycloheximide, and actinomycin D. Adenosine phosphate compounds, indole-3-acetic acid, sulfhydryl reagents, and 0.5 mM CaSO4 were also ineffective in altering the course of permeability change. However, the exposure of sections to osmotica (mannitol, glycerol, KCl) during ageing, at concentrations close to those of solutes found in the apparent free space of squash hypocotyls, significantly inhibited the decline of urea permeability. Once the decline in hypotonic solutions was expressed, it was not reversed by incubation in isotonic solutions in contrast with the short-term effects of osmotica on permeability in freshly excised sections. Apparently, the ageing-dependent decline in urea permeability by squash hypocotyl cells is the expression of a long-term osmotic regulatory process (irreversible) which complements the functioning of a short-term osmotic control system (reversible).
Genetics of Gracilaria tikvahiae (Rhodophyceae). VI. Complementation and linkage analysis of pigmentation mutants
Authors: Meer John P. van der
Published: November 2007

Pigmentation mutants of Gracilaria tikvahiae that differed in several ways from the brownish colour of wild type were characterized genetically by complementation and recombination. Thirty cistrons with multiple alleles at several loci were identified. Many of the cistrons were genetically linked with one or more other loci, and the beginnings of a linkage map is presented. Examples of intragenic recombination between noncomplementing mutants were also encountered.
β-Glucosidases potentially involved in cyanogenesis during infection of white clover by Stemphylium sarciniforme
Authors: Wilkinson H. T. , Millar R. L.
Published: November 2007

White clover (Trifolium repens L.) and Stemphylium sarciniforme (Cav.) Wilt. each produced a β-glucosidase which hydrolyzed linamarin and cyanogenic glucosides in crude extracts of white clover. The relative activities of these β-glucosidases were determined at 0, 48, and 96 h after inoculation of three white clover selections that differed in the presence or absence of cyanogenic β-glucosides (G) and β-glucosidase (E), i.e., G+E+, G+E−, and G−E−. The β-glucosidase from white clover precipitated from aqueous solution at 50% saturation with ammonium sulfate was cationic at pH 5.0 and had equal activity on linamarin and amygdalin. The β-glucosidase from S. sarciniforme precipitated from solution at 75% saturation with ammonium sulfate was anionic at pH 7.1 and was three times more active on amygdalin than on linamarin. The amount of host β-glucosidase activity in the G+E+ white clover inoculated with S. sarciniforme decreased 39% in the interval 48 to 96 h. β-Glucosidase with activity on white clover substrates was not extracted from either the G+E− or G−E− selections before or after inoculation. Pathogen β-glucosidase was detected first in all selections at 48 h and had increased by 96 h to 160, 290, and 260%, respectively, in the G+E+, G+E−, and G−E− selections.
Suppression of germ-tube abnormalities in Helminthosporium turcicum by blue light
Authors: Benedict W. G. , Palmerley R. A.
Published: November 2007

Conidia of Helminthosporium turcicum Pass, trapped on water agar below diseased sweet corn seedlings were germinated under different conditions of illumination and their development was studied after 10 h of incubation. Variations in light intensity and quality affected neither the ability of conidia to germinate nor total germ-tube length. However, blue light of low intensity protected the fungus against germ-tube abnormalities as did daylight of higher light intensity.
Ascospore sculpturing and generic concepts in the Testudinaceae (syn. Zopfiaceae)
Authors: Hawksworth D. L.
Published: November 2007

Generic concepts in the Testudinaceae (Ascomycotina, Loculoascomycetes) are reviewed with particular emphasis on the sculpturing of the ascospores which has been examined by scanning electron microscopy (SEM) for the first time. A key to the nine genera accepted in the family is provided of which two are described as new: Ulospora for U. bilgramii comb.nov. (= Zopfia bilgramii D. Hawksw. et al.), the ascospores of which have three to six deep fissures in each cell, and Zopfiofoveola for Z. punctata comb.nov. (= Zopfia punctata D. Hawksw. & C. Booth), with distinctly and regularly foveolate ascospores. One further new combination is made: Rechingeriella boudieri comb.nov. (= Zopfia boudieri Arnaud). The positions of three additional genera referred to the family by earlier authors but which are excluded from it here are also briefly discussed.
A new psammophilic Leccinum
Authors: Redhead Scott A. , Watling Roy
Published: November 2007

Leccinum arenicola Redhead & Watling sp.nov. is described from coastal sand dunes in Kouchibouguac National Park, New Brunswick, Canada. Its probable mycorrhizal partner is Hudsonia tomentosa Nutt.
A tissue culture procedure for propagation and maintenance of Lotus corniculatus genotypes
Authors: Tomes Dwight T.
Published: November 2007

A tissue culture procedure for the establishment, multiplication, and maintenance of genotypes of birdsfoot trefoil, Lotus corniculatus L., is described. Surface sterilization followed by tissue culture of the apical shoot-tip or node sections of the stem produces small shoots within 1 month. Tissue cultures are established faster from node sections than shoot-tip explants, although shoot-tip explants are favoured where surface sterilization is difficult.The addition of the cytokinin benzyladenine in the culture medium enhanced shoot formation from shoot tips and increased the number of shoots produced from shoot-tip and node cultures. Incubation of tissue cultures at reduced temperatures (2–4 °C) for 1 month resulted in very little change in number or height of shoots in the cultures during the incubation period. Plantlets transferred from cultures incubated at low temperature to the growth room had a high survival rate. The tissue culture once established can be subcultured for propagation or storage or returned to the growth room or field as plants.
Effects of sulfur dioxide and ozone on Ulmus americana seedlings. I. Visible injury and growth
Authors: Constantinidou H. A. , Kozlowski T. T.
Published: November 2007

The effects of SO2 (2 ppm for 6 h), O3 (0.9 ppm for 5 h), and SO2–O3 mixtures (2 ppm SO2 and 0.9 ppm O3 for 5 h followed by SO2 for 1 h) were studied on injury and growth of 4-month-old, actively growing and quiescent Ulmus americana L. seedlings. In actively growing seedlings visible injury to leaves from SO2–O3 mixtures was evident within 24 h; from O3 within 36 to 48 h; and from SO2 within 48 h after fumigation ceased. Sulfur dioxide and SO2–O3 treatments reduced expansion of new leaves (< 1 cm long at time of fumigation) within 1 week, but normal rates of leaf expansion were restored by the end of the 2nd week. Ozone had no significant effect on expansion of new leaves. Expansion of young leaves (> 1 cm long at time of fumigation) was markedly inhibited by all treatments; it was inhibited most by SO2–O3, an intermediate amount by SO2, and least by O3. Numbers of emerging leaves were significantly reduced by SO2, and by SO2–O3, but only at the end of the 1st week. After 5 weeks, stem dry weights were reduced by O3 and SO2–O3, and root dry weights were reduced by SO2 and SO2–O3. In quiescent plants pollution injury to leaves was similar to that in actively growing plants. However, all fumigation treatments induced severe defoliation in quiescent plants.
Observations on predatory fungi
Authors: Barron G. L.
Published: November 2007

In Arthrobotrys flagrans the chlamydospores are formed, following rupture of the primary hyphal wall, by expansion of the inner wall which then produces warty encrustations over its surface. Evidence is presented to show that in Arthrobotrys anchonia none of the water necessary for expansion of the constricting ring cells comes through the stalk cells. Expansion of constricting rings in Dactylaria brochopaga often appears biphasic with little or no constriction of the host cuticle taking place during the first phase of expansion. Microconidia have been found in three species of predatory fungi with constricting rings. In the presence of nematodes, microconidia germinate directly to produce small, functional, constricting rings.
Some aspects of carbon relations in the barley – Helminthosporium teres complex. II. The effects of infection upon net accumulation of carbon in the tissues
Authors: Rowe Janet , Reid J.
Published: November 2007

First leaves of seedlings of the barley varieties Parkland (susceptible) and C.I. 5791 (resistant) were inoculated with Helminthosporium teres and the net accumulation of carbon (NA) in such leaves and in the uninoculated second leaves of these plants was examined in long-term experiments. In infected leaves of Parkland, NA in the light period of the diurnal cycle was maintained near the levels of controls even when photosynthetic capacity had decreased by ca. 50%, though NA in the dark period had increased 300–400%. However, neither this carbon nor that entering metabolism via β-carboxylation in the light was sufficient to compensate for the loss of photosynthetic capacity over 24 h. Translocation experiments showed that while infection did not increase the movement of carbon from the uninoculated second to infected first leaves, export of carbon by the first leaves (normally high) was greatly reduced, and this retained photosynthate appeared largely responsible for the maintenance of NA in the infected leaves. NA in the uninoculated second leaves of infected plants was reduced only while these leaves were heavily dependent on the first leaves for photosynthate. In infected leaves of C.I. 5791, though photosynthetic capacity dropped and β-carboxylation increased while the pathogen was developing, there was little effect on NA over 24 h. The implications of the effects of infection on NA are discussed.
Studies on lichen-dominated systems. XXII. The environmental control of nitrogenase activity in Stereocaulon paschale in spruce–lichen woodland
Authors: Crittenden P. D. , Kershaw K. A.
Published: November 2007

Stereocaulon paschale (L.) Hoffm. collected from spruce–lichen woodland (Northwest Territories) at different times of the year was assayed for nitrogenase activity (acetylene reduction) under factorial combinations of photosynthetically active radiation (PAR), thallus temperature, and moisture. Marked seasonal changes in C2H2-reducing capacity were recorded, potential activity being minimal in samples from beneath snow beds in March and maximal in summer collections. Physiological–environmental relationships established in the laboratory were largely consistent with diurnal and seasonal variations in nitrogenase activity in S. paschale mats recorded in situ. When thallus water content was not limiting (i.e., values > 120% of thallus dry weight), diurnal variation in nitrogenase activity was correlated with changes in PAR and thallus temperature or, under isothermal conditions, with changes in PAR alone when C2H2 reduction continued throughout dark periods at ca. 40% of daylight rates. However, while nitrogenase activity in S. paschale at any point in time was dependent upon concurrent environmental conditions, it also was strongly influenced by pretreatment: both winter frost and thermal stress during summer droughts impeded recovery of nitrogenase activity following the onset of ameliorative conditions. It is suggested that a large fraction of the total annual N assimilation by S. paschale in drier, continental subarctic habitats may be achieved in summer during a few comparatively short episodes of suitable moisture conditions.
Mosses of the Nahanni and Liard ranges area, southwestern Northwest Territories
Authors: Vitt Dale H. , Horton Diana G.
Published: November 2007

The Nahanni and Liard mountain ranges are located at about 61° N latitude and 122° W longitude. They form the easternmost slopes of the Rocky Mountains and lie just east of Nahanni National Park in the southwestern corner of the District of Mackenzie, Northwest Territories. The moss flora of the area is rich in the number of taxa; 207 species and two varieties are reported from this relatively small area. Of these, 53 species are new records for the South Nahanni region. A number of rare or disjunct bryophyte species are found in the area. Moss species which are either disjunct or occur at the edge of their range include Arctoa fulvella (Dicks.) B.S.G., Aulacomnium acuminatum (Lindb. & Arn.) Kindb., Andreaeobryum macrosporum Steere & B. Murray, Geheebia gigantea (Funck) Boul., Isopterygiopsis muelleriana (Schimp.) Iwats., Mnium spinosum (Voit) Schwaegr., Psilopilum cavifolium (Wils.) Hagen, Rhabdoweisia crispata (With.) Lindb., Seligeria calcarea (Hedw.) B.S.G., S. polaris Berggr., Trematodon brevicollis Hornsch., and Trichostomum arcticum Kaal. The North American distribution of these species is mapped. Herbertus stramineus (Dum.) Trev., Metacalypogeia schusterana Hatt. & Mizut., Scapania crassiretis Bryhn, and S. simmonsii Bryhn & Kaal. are four hepatic species of phytogeographic interest.
Enzyme expression in soybean cotyledon, callus, and cell suspension culture
Authors: Matthews Benjamin F. , Widholm Jack M.
Published: November 2007

Feedback control of enzymes in the pathway for the biosynthesis of aspartate-family amino acids was examined using Glycine max callus, suspension cultures, and seedlings to determine if the controls are different in the three systems. Aspartate kinase activity (EC 2.7.2.4) derived from soybean cell suspension cultures is 50% inhibited by 1.0 mML-threonine and 50% inhibited by 1.0 mML-lysine. In contrast, aspartate kinase activities from 3-day-old seedling cotyledons and from callus cultures grown from cell suspension cultures are inhibited approximately 70% by 1.0 mM threonine and 30% by 1.0 mM lysine. These data and chromatographic data indicate that different ratios of a lysine-sensitive and a threonine-sensitive aspartate kinase enzyme can occur in soybean cotyledons and callus as compared with cell suspension cultures. Threonine (1 mM) inhibited homoserine dehydrogenase activities (EC 1.1.1.3) from cotyledon and cell suspension cultures approximately 67 ± 2% while the activity from callus was inhibited slightly more (77 ± 1%). Four forms of homoserine dehydrogenase activity were detected on electrophoretic gels containing cotyledon extracts, while only three of these forms of homoserine dehydrogenase activity were detected in extracts of callus and cell suspension cultures. The threonine-insensitive form disappeared, while the three threonine-sensitive forms were still present. Dihydrodipicolinate synthase activities (EC 4.2.1.52) from all three sources were at least 95% inhibited by 1.0 mM lysine. Only one form of this enzyme was detected on electrophoretic gels.
A histological study of interactions between avirulent races of stem rust and wheat containing resistance genes Sr5, Sr6, Sr8, or Sr22
Authors: Rohringer R. , Kim W. K. , Samborski D. J.
Published: November 2007

Primary leaves of wheat (Triticum aestivum L.) with and without resistance genes Sr5, Sr6, Sr8, or Sr22 were inoculated with avirulent races of stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn.) and examined by fluorescence microscopy. In leaves containing the Sr5 gene for resistance, both epidermal and mesophyll cells fluoresced when interacting with the fungus, indicating incompatibility. In leaves containing the Sr6 gene, interacting epidermal cells did not fluoresce and incompatibility was expressed only in mesophyll cells.When the effect of the Sr5 gene was studied in leaves with different genetic backgrounds, it was found that most colonies developed only one or two haustorial mother cells in leaves containing this gene in Prelude, Marquis, or Reliance backgrounds, when examined up to 72 h after incubation. Conversely, in leaves with the Chinese Spring background, one-third of the colonies continued to grow and they produced macroscopically visible lesions. Our observations indicated that the Chinese Spring genotype partially altered the expression of the Sr5 gene in mesophyll but not in epidermal cells. In contrast, the Sr6 gene was more effective in the Chinese Spring background than in the Prelude background.Rust development in leaves with or without the Sr8 gene was the same up to 60 h after incubation, when incompatibility in resistant plants was first detected by the appearance of fluorescing host cells. By 72 h, mean colony size in resistant leaves was smaller than that in susceptible leaves, evidently because growth of runner hyphae was inhibited. Apparently, the P8 gene for avirulence was not expressed until colonies had reached considerable size. In leaves containing the Sr22 gene for resistance, the sequence of histological events was similar to that in leaves containing Sr8, but fluorescing host cells appeared later (72 h) and colony growth was inhibited only at 96 h after incubation. In both of these interactions, fluorescing host cells developed at the periphery of colonies when incompatibility was expressed. The host-parasite interaction in cells invaded before that time remained compatible even at later stages of colony development. In leaves containing the Sr5 or the Sr8 gene, but not in those with the Sr6 gene, the growth of some colonies was inhibited although they were not associated with fluorescing host cells. Evidently, host-cell necrosis was closely associated with reduced fungal growth in interactions involving Sr6, but not in interactions involving the resistance genes Sr5 and Sr8.
Seasonal development of Dutch elm disease on white elms in central Ontario, Canada. II. Following feeding by the North American native elm bark beetle
Authors: Takai S. , Kondo E. S. , Thomas J. B.
Published: November 2007

Adults of the North American native elm bark beetle, Hylurgopinus rufipes, naturally infested with Dutch elm disease fungus, Ceratocystis ulmi, were caged on trunks of white elms (Ulmus americana) so that infection could be studied. In surveys made in 1971, expression of external symptoms of Dutch elm disease was observed on elms which had been caged with beetles during the period May 26 to July 9, 1971. Vascular discoloration (internal symptom expression), fungus spread, fungus contamination of beetles, and transmission of fungus to the host by beetles were pronounced on elms caged with beetles from June 3 to July 2. Ceratocystis ulmi was recovered from leaves of trees caged during the period May 26 to July 2. Until May 31, 1972, dieback and death resulting from infection were restricted to trees caged with beetles during June. Corresponding development of vascular discoloration and fungus spread in the host also occurred, mostly during the caging period in June. There was no appreciable change in beetle activity in xylem tissue during the period of experiment. These results suggest that the period of highest susceptibility of white elm to Dutch elm disease in 1971 in central Ontario was June 3 to July 2.Inoculation through feeding by caged beetles carrying C. ulmi is probably the method that most closely approximates natural infection.
Alterations in chloroplast and cell membranes associated with cAMP-induced dissociation of starch grains in clover yellow mosaic virus infected clover
Authors: Tu J. C.
Published: November 2007

The ultrastructure of healthy and clover yellow mosaic virus (CYMV) infected leaves of White Dutch clover has been examined in an electron microscope using both thin-section and freeze-fracture techniques. A striking difference between leaves from healthy and diseased plants was that more starch grains were present in infected leaves compared with healthy ones. Feeding 3′,5′-cyclic adenosine monophosphate (cAMP) or dibutyryl-cAMP (bt-cAMP) to both healthy and diseased plants induced rapid dissociation of accumulated starch grains. Examination of freeze-fracture replicas indicated that this dissociation is associated with alterations in the ultrastructure of chloroplast and cell membranes. These alterations include aggregation of intramembranous particles and blebbing and wrinkling of the membranes. The significance of these alterations in relation to the dissociation of starch grains in CYMV-diseased leaves is discussed.
Histological relationship of Phytobia setosa to Acer saccharum
Authors: Gregory Robert , Wallner William
Published: November 2007

The maple cambium miner, Phytobia setosa (Loew), attacks Acer spp., producing ray flecks which result in degrade in face veneer and furniture wood. Samples from infested sugar maple, Acer saccharum Marsh, trees demonstrated that while mines passed close to the vascular cambium the initial cells were not affected. Thus, although it is called a cambium miner it does not mine the cambium. Mines filled with parenchyma cells which proliferated from severed vascular rays. These cells, when mature, stored starch. In heavily infested trees the starch storage area in the xylem may thus be measurably increased. The zone of newly differentiating xylem provides the insect with the path of least resistance; variation in the condition of secondary xylem may account for the variability in host susceptibility.
Cytological studies of early stages of powdery mildew in barley and wheat. VI. Antagonistic effects of calcium and lithium on the infection of coleoptiles of barley by Erysiphe graminis hordei
Authors: Takamatsu S. , Ishizaki H. , Kunoh H.
Published: November 2007

Earlier researchers have shown that the susceptibility of barley to infection by Erysiphe graminis hordei is enhanced by calcium ions but inhibited by lithium. Some effects of these ions on the infection process of E. graminis hordei in coleoptiles of barley were investigated in this study. Whereas 1 mM lithium chloride inhibited appressorial formation considerably and haustorial formation completely, these effects were totally offset by 10 mM calcium chloride. Moreover, whereas 5 and 10 mM lithium chloride inhibited both appressorial and haustorial formation completely, the former was offset considerably by 10 mM calcium chloride, but the latter was not.Sequential calcium chloride − lithium chloride or lithium chloride − calcium chloride treatments carried out at different times and for various durations showed that events occurring in coleoptiles 11 to 13 h after inoculation were most vulnerable to the treatments. These events correspond to infection stages involving the development of cytoplasmic aggregates, papillae, and haustoria. The data suggest that the two ions in question might compete for a common binding site in a reaction(s) associated with certain stages of appressorial and haustorial development.
Changes in the proportions of two forms of invertase associated with the cold acclimation of wheat
Authors: Roberts D. W. A.
Published: November 2007

The proportion of two of the forms of invertase in wheat leaves is different when the plants are grown under cold-hardening conditions compared with under nonhardening conditions. Twelve varieties of bread wheat (Triticum aestivum L. emend. Thell. ssp. vulgare) of diverse levels of cold hardiness showed a high rank-order correlation between their level of cold hardiness and the ratio of peak I to peak II invertase in the leaves grown for 7–8 weeks at 6–4 °C. Similar trends were evident among four of these varieties grown for 11–13 or 20–24 weeks at 3 °C. No such correlations were observed in plants grown at 21 °C, i.e., under conditions that induce little or no cold hardening. The single durum wheat (Triticum durum Desf.) tested behaved somewhat differently.When plants of a single variety were grown under different hardening conditions, the cold resistance of the plants and the ratio of peak I to peak II invertase in their leaves were not closely related. However, cold-hardened common winter wheat varieties had much higher ratios of peak I to peak II invertase in their leaves than did similar varieties in the unhardy condition or cold-sensitive varieties.In the bread wheats, the amount of peak I invertase increases in plants grown under conditions causing cold hardening relative to that in plants grown at 21 °C while the amount of peak II invertase decreases. This suggests that one form of invertase replaces another during cold hardening.
Gradient analysis of the vegetation in a brackish marsh in Bellingham Bay, Washington
Authors: Disraeli D. J. , Fonda R. W.
Published: November 2007

The islands in the delta of the Nooksack River support a brackish marsh with maximum salinity of 5.18 parts per thousand (ppt). On high tides, the marsh is flooded with water from the river rather than from Bellingham Bay. Marsh species were distributed according to combinations of elevation, length of tidal submergence, sand and silt content of the soil, and soil moisture. Two broad marsh zones were recognized. The Scirpus americanns marsh occurs below 274 cm above mean lower low water (MLLW), where it is submerged on nearly all high tides. It has over 70 submergence days per year. Soils are sandy but poorly drained, and aerial biomass is low. The Carex lyngbyei marsh occupies sites above 274 cm. This zone has fewer than 50 submergence days per year. These sites have siltier soils, better soil-moisture values, and greater biomass.
Magnesium uptake in Neocosmospora vasinfecta
Authors: Budd K.
Published: November 2007

Mycelium of Neocosmospora vasinfecta E. F. Smith grown in media of restricted Mg2+ supply was used for experiments on Mg2+ uptake. The mycelium carried out adsorption and influx of Mg2+. Two binding species at the mycelial surface were responsible for Mg2+ adsorption, with association constants of 2.1 × 106 and 1.6 × 104 L/mol, respectively. Influx of Mg2+ within the range of 5 to 500 μM Mg2+ took place via a single kinetically distinct transport system with an apparent Km for Mg2+ of 30 to 40 μM. Influx of Mg2+ varied markedly with mycelial Mg2+ status, whereas efflux appeared much less variable in rate. The results indicated that internal mycelial Mg2+ content is regulated by modulation of Mg2+ influx.
Isolation and cultivation of protoplasts from morphogenetic callus cultures of Lilium
Authors: Simmonds John A. , Simmonds Daina H. , Cumming Bruce G.
Published: November 2007

Protoplasts isolated from Lilium callus which was maintained on media containing 2% sucrose contained large deposits of starch granules and lysed during isolation and washing procedures. Stable protoplast preparations could be obtained from callus which had been subcultured on sucrose-free medium for 3 weeks. Maximum protoplast yield (1.5 × 106 per gram fresh weight) was obtained when KCl (0.3 M) was the osmotic stabilizer. Inclusion of CaCl2 (25 mM) and MgSO4 (25 mM) in the isolation and wash media decreased protoplast lysis. Viability of protoplasts isolated in the high salts medium was determined by their ability to accumulate sodium fluorescein in the cytoplasm. No cell-wall formation occurred when salts were used as the osmoticum in various culture media. Continuous light (5000 lx) was inhibitory to protoplast survival. When protoplasts were transferred, via a series of wash solutions, to culture media using sugars as the osmoticum and cultured in darkness, cell-wall formation was detected after 3 days and cell divisions after 21 days. Zeatin (10−6 M), was needed for cell-wall formation. Cell division was stimulated by a combination of zeatin (10−6 M), naphthaleneacetic acid (10−5 M), and 2,4-dichlorophenoxyacetic acid (10−7 M) in the basic nutrient medium.
Les critères cytophysiologiques de la phase intermédiaire chez l’Aster sinensis (Composées)
Authors: Nougarède A. , Rembur J.
Published: November 2007

Aster sinensis flowering normally occurs under 12-h- or 8-h-long days. However, in this species, the transition to the prefloral stage is accelerated by long days, while the floral morphogenesis is favoured by a 12- or 8-h day length. Under short or 12-h photoperiods, the plants go through a long intermediate phase during which the plastochrone has a duration equal to that observed in the preceding vegetative phase. During the intermediate phase, the sizes of all apical zones noticeably increase, particularly for the axial zone, at the corpus level. Moreover, mitotic indices and DNA contents in all zones are significantly higher than those of vegetative meristems. In the shoot apex of Aster sinensis, the intermediate phase, which involves structural and nuclear changes, appears as a preparatory stage to flowering.
The growth of sugarcane downy mildew fungus in tissue culture
Authors: Chen Wen-Huei , Liu Ming-Chin , Chao Chia-Yu
Published: November 2007

Dual culture of sugarcane downy mildew fungus (Sclerospora sacchari Miyake) was established by placing a diseased sugarcane explant (shoot apex or spindle leaf) on a modified Murashige and Skoog medium containing 3 ppm 2,4-dichlorophenoxyacetic acid. After 3 weeks incubation, dense mycelia grew both on and in the callus which had developed. The use of different varieties or illumination periods did not affect the growth of the fungus. The hyphae ceased to grow when the infected callus was subcultured. A workable procedure was devised which enabled the hyphae to proliferate on a healthy tissue when diseased tissue was placed near it. Explants excised from either resistant or susceptible varieties could nurse the growth of the fungus, indicating that resistant genes may not be expressed in tissue culture. Histological studies revealed that the callus originated from mesophyll cells in leaf and parenchymatous cells of shoot apical tissue. Intercellular and intracellular hyphae were more concentrated in the peripheral layer of parenchymatous cells than in the meristemoid region. Carbohydrate callose accumulated on the hyphal walls and cell walls of the callus wherever hyphae were growing.
Distribution and abundance of attached, littoral algae in 21 lakes and streams in the Northwest Territories
Authors: Moore James W.
Published: November 2007

Collections of epilithic, epipelic, epiphytic, and epipsammic algae were made from the littoral zone of 21 lakes and streams in the Northwest Territories during 1975 and 1976. Tabellaria flocculosa was the predominant species in the epilithon and epipelon, reaching maximum densities of 0.5–2.5 × 109 μm3/cm2 depending on watercourse. It was followed in importance by Achnanthes minutissima, Navicula spp., and Nitzschia frustulum, all of which occurred at densities of 0.1–0.3 × 109 μm3/cm2. While the only two common taxa in the epiphyton, A. minutissima and T. flocculosa, maintained populations of 1.0–1.3 × 109 μm3/cm2, the most frequently encountered epipsammic species, Amphora ovalis var. pediculus, Fragilaria construens var. venter, Achnanthes minutissima, and Achnanthes pinnata, reached maximum levels of 4 × 107 μm3/cm2. The growing season for the attached flora extended from June to October throughout the study area. All four communities displayed a unimodal growth curve during this period, reaching maximum abundance in either July or August. The end of the growing season came during the middle of October when the collection sites were frozen to the bottom.
Invasion of lupin seed by Verticillium albo-atrum
Authors: Parnis E. M. , Sackston W. E.
Published: November 2007

Lupinus albus L. inoculated at 6 weeks and L. luteus L. at 11 weeks by stem injection with a spore–mycelium suspension of Verticillium albo-atrum Reinke and Berth. produced 2.5 and 6.8% infected seeds, respectively. Other methods of inoculation failed to produce seed infection. The pathogen was present internally in infected seeds of L. luteus, but in L. albus it was superficial. Histological observations indicated that plugs of amorphous material in infected vessels, and branching of the vessels, may serve as barriers to seed infection. Even the low levels of seed infection observed may have economically significant epidemiological implications.
Anther and pollen development in male-sterile intermediate wheatgrass plants derived from wheat × wheatgrass hybrids
Authors: Young B. A. , Schulz-Schaeffer J. , Carroll T. W.
Published: November 2007

Several different expressions of male sterility were observed in the plants sampled for the study of pollen and anther development in the third substitution backcross generation to intermediate wheatgrass. These included (1) pollen abortion following engorgement with starch, (2) abortion of microspores with exine abnormalities (found most often in plants with a high degree of meiotic irregularities), (3) abortion of microspores with normal exines, (4) release at anther dehiscence of normal-appearing late vacuolate microspores, (5) enlargement of one of the parietal layers of the anther, and (6) tapetal abnormalities, including orbicular wall malformations. Anthers from plants which were male sterile or partially male sterile and meiotically irregular were shorter than anthers from fertile or partially male-sterile, meiotically regular plants.Definite statements about specific causes of the male sterility could not be made. Meiotic irregularities may be involved in some of the male sterility, and exine malformations appeared to be directly related to sterile microspores. Tapetal disturbances were observed infrequently. Probably the consequences of several factors were observed in the backcross material.
Some occurrences of vesicular–arbuscular mycorrhiza in natural and disturbed ecosystems of the Red Desert
Authors: Miller R. Michael
Published: November 2007

Studies have been initiated on the occurrence of vesicular–arbuscular mycorrhiza (VAM) in plant communities of revegetated mine spoils and undisturbed areas of the Red Desert of Wyoming. It was found that the majority of plants in undisturbed environments in this area are mycorrhizal. On disturbed sites, no mycorrhiza were encountered. Of interest for both the undisturbed and disturbed communities was the predominance of plants belonging to the family Chenopodiaceae. The major difference between the plant species encountered in each community is associated with their reproductive strategy, as well as whether the plants possessed VAM. The major species encountered on undisturbed sites are Atriplex gardneri, At. confertifolia, Ceratoides lanata, Grayia spinosa, Kochia americana, and Sarcobatus vermiculatus, all possessing mycorrhiza. Halogeton glomeratus predominated in disturbed sites and did not possess VAM. The role of VAM in both succession and reproductive strategies of plants is also discussed.
Ontogeny of the uredium of Melampsora lini
Authors: Hassan Z. M. , Littlefield L. J.
Published: November 2007

Light microscopy and transmission and scanning electron microscopy were used to study the development of uredia of Melampsora lini. Uredia were produced 6–10 days after inoculation with urediospores of M. lini. Uredium ontogeny began with the formation of a uredium initial from a hyphal plexus in a substomatal cavity. The hyphae oriented vertically and expanded; the enlarged ends divided to form a palisade of uredial initial cells. These cells divided into basal and terminal cells. Each terminal cell divided transversely to form a peridial and an intercalary cell; the basal cell became the sporogenous cell. The intercalary cells disintegrated early in the expansion of the uredium and released their contents into the intercellular matrix. The sporogenous cell, usually swollen at one end, gave rise by budding to successive sympodially produced spore buds which elongated and divided transversely to form pedicels and immature spore cells. As the spores matured the pedicels shriveled and became separated from the urediospores. Elongated, often capitate, paraphyses formed throughout the uredium and functioned to rupture the peridium and epidermis which covered the immature uredium. The peridium and the intercalary cells formed only once during ontogeny of the uredium, this being associated with only the first generation of urediospores. The intercalary cells were disrupted during uredium ontogeny, and most of the peridial cell layer was sloughed off, along with the overlying epidermis, upon rupture of the latter. The paraphyses were permanent and remained in the uredium throughout its functional life. Successive generations of urediospores arose within the same uredium from spore buds produced sympodially from the original sporogenous cell but without forming additional peridial or intercalary cells.
Effects of fertilizer salt concentration on viability of seed and Rhizobium used for hydroseeding
Authors: Carr W. W. , Ballard T. M.
Published: November 2007

For testing salt effects on seed and Rhizobium, 10–30–10 fertilizer and KCl solutions were used; the solutions had an osmotic potential of − 2.5 MPa, equivalent to 90 kg of the fertilizer per cubic metre of water. Solution contact for 1 h slightly affected the viability of Rhizobium trifolii Dangeard but the effects were not of practical significance. Reduced viability was exhibited by Festuca arundinacea Schreb., F. rubra L. var. commutata Gaud., and Trifolium repens L. seed which had been rinsed after 1 h of fertilizer solution contact. Agrostis alba L., Dactylis glomerata L., F. rubra L., Lolium perenne L., L. multiflorum L., Phleum pratense L., T. hybridum L., and T. pratense L. were not significantly affected. In tests of seed unrinsed after solution contact for 1 h, viability of F. rubra, F. arundinacea, and T. repens was significantly reduced; that of L. multiflorum was not. Trifolium repens was more affected than in the test of rinsed seed.As T. repens viability was reduced as much as 30%, seed of this species might be applied separately from hydroseeder slurries having high fertilizer concentrations. Significant effects on other species tested are too small to influence hydroseeding methods, but amount and proportion of the seed mix may be altered where high fertilizer concentrations are used.
The effect of sulfur dioxide upon the metabolic level of adenosine triphosphate
Authors: Harvey Geoffrey W. , Legge Allan H.
Published: November 2007

The ATP content of lodgepole – jack pine (Pinus contorta × banksiana) hybrids in the cordillerean–boreal transition zone was monitored during sulfur dioxide fumigations. Foliage was stabilized for analysis during the course of sulfur dioxide fumigations originating from a sour gas processing plant located in west-central Alberta. Controlled sulfur dioxide fumigations of seedlings were conducted in the laboratory to measure their effect upon ATP content. Field studies demonstrated that ATP concentrations of needle cells declined as sulfur dioxide concentration increased in the ambient air. An inverse linear relationship was found between ATP content and the measured sulfur dioxide concentration. The effect could be repeated in the laboratory with growth chamber cultured seedlings only in exceptional cases. It was repeated with detached branches from the field site exposed to sulfur dioxide under laboratory conditions. The results illustrate the fundamental differences between foliage preadapted to low-level sulfur dioxide fumigations and foliage grown under optimal conditions in a growth chamber.
New species of Gelatinosporium on western conifers
Authors: Funk A.
Published: November 2007

The following new taxa in the genus Gelatinosporium Peck (Coelomycetes) are proposed: G. griseo-lanatum n.sp., G. sinuatum n.sp., and G. stillwelli n.sp.; new combinations for three species in Gelatinosporium, and a new name for Micropera uncinala. Foveoslroma boycei comb.nov. is proposed for Micropera boycei.
Ultrastructure of wilt syndrome caused by Verticillium dahliae. VII. Correlated light and transmission electron microscope identification of vessel coatings and tyloses
Authors: Robb Jane , Brisson J. D. , Busch Lloyd , Lu B. C.
Published: November 2007

Thin cross sections of petioles from wilted leaves of chrysanthemums infected with Verticillium dahliae were fixed in glutaraldehyde + FeCl3 and embedded for electron microscopy. Alternate thick (LM) and thin (TEM) sections were cut. The thick sections were stained with (1) the Prussian blue reaction, (2) Sudan black B, (3) toluidine blue O, or (4) Schiff s reagent. Correlated LM and TEM of exactly the same vessels showed that tylosis walls, smooth coating, fibrillar coating, and bubbly coating stained differentially. The tyloses are more abundant than formerly anticipated but are restricted to the primary vessels; fungal cells and coating on vessel walls are confined to smaller secondary vessels.
Field and laboratory germination responses of achenes of Polygonum lapathifolium, P. pensylvanicum, and P. persicaria
Authors: Staniforth R. J. , Cavers P. B.
Published: November 2007

The annual smartweeds Polygonum lapathifolium L., P. pensylvanicum L., and P. persicaria L. are weeds of cereal crops, waste places, and wet ground in Canada. Their ‘weediness’ is attributed, in part, to the production of large numbers of achenes which are capable of lying dormant in the soil for several years or until suitable conditions arise for germination.Dormancy–germination characteristics of achenes from Ontario plants were examined in the laboratory and in the field. Three types of dormancy have been identified, each of which prevents germination under a different set of unfavourable conditions. An innate dormancy prevents germination in fresh achenes immediately prior to winter. An enforced dormancy prevents germination during the winter and in achenes which are deep in the soil. An induced dormancy is caused by hot or dry periods (at least in P. persicaria). Germination occurs as a series of flushes whenever achenes are brought to the soil surface and (or) whenever rainy spells occur.
Photosynthetic and light-independent carbon fixation in Macrocystis, Nereocystis, and some selected Pacific Laminariales
Authors: Willenbrink J. , Kremer B. P. , Schmitz K. , Srivastava L. M.
Published: November 2007

The large kelp Macrocystis integrifolia and Nereocystis luetkeana off the coast of British Columbia have light saturation points at about 200 foot candles (1 foot candle = 10.76391 lx); however, photosynthetic rates remain unimpeded through mugh higher light intensities, up to 7000 foot candles. Short-term labelling experiments indicate that the Calvin cycle is operational in these plants, but, in addition, and particularly in the young growing parts, relatively high activities of phosphoenolpyruvate carboxykinase (PEP-CK)and correspondingly high rates of 14C fixation in the dark are observed. In older, mature parts, the activity of PEP-CK as well as the ability for light-independent 14C assimilation are lower. These observations are supported by data from a variety of other Pacific Laminariales. Pulse–chase experiments in the light and in the dark reveal characteristic differences between young and mature parts of the fronds: apart from qualitative difference in the soluble fraction of assimilates, the young parts show a significantly large proportion of radiocarbon confined to the ethanol-insoluble fraction.