bluuebunny/crossref_metadata_2025 huggingface dataset:
Ectromelia Virus Encodes a Novel Family of F-Box Proteins That Interact with the SCF Complex
Authors: van Buuren Nick , Couturier Brianne , Xiong Yue , Barry Michele
Published: August 2008

Poxviruses are notorious for encoding multiple proteins that regulate cellular signaling pathways, including the ubiquitin-proteasome system. Bioinformatics indicated that ectromelia virus, the causative agent of lethal mousepox, encoded four proteins, EVM002, EVM005, EVM154, and EVM165, containing putative F-box domains. In contrast to cellular F-box proteins, the ectromelia virus proteins contain C-terminal F-box domains in conjunction with N-terminal ankyrin repeats, a combination that has not been previously reported for cellular proteins. These observations suggested that the ectromelia virus F-box proteins interact with SCF (
S
kp1,
c
ullin-1, and
F
-box) ubiquitin ligases. We focused our studies on EVM005, since this protein had only one ortholog in cowpox virus. Using mass spectrometry, we identified cullin-1 as a binding partner for EVM005, and this interaction was confirmed by overexpression of hemagglutinin (HA)-cullin-1. During infection, Flag-EVM005 and HA-cullin-1 colocalized to distinct cellular bodies. Significantly, EVM005 coprecipitated with endogenous Skp1, cullin-1, and Roc1 and associated with conjugated ubiquitin, suggesting that EVM005 interacted with the components of a functional ubiquitin ligase. Interaction of EVM005 with cullin-1 and Skp1 was abolished upon deletion of the F-box, indicating that the F-box played a crucial role in interaction with the SCF complex. Additionally, EVM002 and EVM154 interacted with Skp1 and conjugated ubiquitin, suggesting that ectromelia virus encodes multiple F-box-containing proteins that regulate the SCF complex. Our results indicate that ectromelia virus has evolved multiple proteins that interact with the SCF complex.
Human Endogenous Retrovirus Family HERV-K(HML-2) RNA Transcripts Are Selectively Packaged into Retroviral Particles Produced by the Human Germ Cell Tumor Line Tera-1 and Originate Mainly from a Provirus on Chromosome 22q11.21
Authors: Ruprecht Klemens , Ferreira Humberto , Flockerzi Aline , Wahl Silke , Sauter Marlies , Mayer Jens , Mueller-Lantzsch Nikolaus
Published: August 2008

The human germ cell tumor line Tera-1 produces retroviral particles which are encoded by the human endogenous retrovirus family HERV-K(HML-2). We show here, by quantitative reverse transcriptase PCR, that HML-2
gag
and
env
RNA transcripts are selectively packaged into Tera-1 retroviral particles, whereas RNAs from cellular housekeeping genes and from other HERV families (HERV-H and HERV-W) are nonselectively copackaged. Assignment of cloned HML-2
gag
and
env
cDNAs from Tera-1 retroviral particles to individual HML-2 loci in the human genome demonstrated that HML-2 RNA transcripts packaged into Tera-1 retroviral particles originate almost exclusively from an HML-2 provirus on chromosome 22q11.21. Based on relative cloning frequencies, this provirus was the most active among a total of eight transcribed HML-2 loci identified in Tera-1 cells. These data suggest that at least one HML-2 element, that is, the HML-2 provirus on 22q11.21, has retained the capacity for packaging RNA into HML-2-encoded retroviral particles. Given its elevated transcriptional activity and the presence of a full-length Gag open reading frame, the 22q11.21 HML-2 provirus may also significantly contribute to Gag protein and thus particle production in Tera-1 cells. Our findings provide important clues to the generation and biological properties of HML-2-encoded particles. In addition, copackaging of non-HML-2 HERV transcripts in HML-2-encoded particles should inform the debate about endogenous retroviral particles putatively encoded by non-HML-2 HERV families that have previously been described for other human diseases, such as multiple sclerosis.
Evolutionarily Conserved Function of a Viral MicroRNA
Authors: Seo G. J. , Fink L. H. L. , O'Hara B. , Atwood W. J. , Sullivan C. S.
Published: August 2008

MicroRNAs (miRNAs) are potent RNA regulators of gene expression. Some viruses encode miRNAs, most of unknown function. The majority of viral miRNAs are not conserved, and whether any have conserved functions remains unclear. Here, we report that two human polyomaviruses associated with serious disease in immunocompromised individuals, JC virus and BK virus, encode miRNAs with the same function as that of the monkey polyomavirus simian virus 40 miRNAs. These miRNAs are expressed late during infection to autoregulate early gene expression. We show that the miRNAs generated from both arms of the pre-miRNA hairpin are active at directing the cleavage of the early mRNAs. This finding suggests that despite multiple differences in the miRNA seed regions, the primary target (the early mRNAs) and function (the downregulation of early gene expression) are evolutionarily conserved among the primate polyomavirus-encoded miRNAs. Furthermore, we show that these miRNAs are expressed in individuals diagnosed with polyomavirus-associated disease, suggesting their potential as targets for therapeutic intervention.
Fusion of Enhanced Green Fluorescent Protein to the Pseudorabies Virus Axonal Sorting Protein Us9 Blocks Anterograde Spread of Infection in Mammalian Neurons
Authors: Lyman M. G. , Curanovic D. , Brideau A. D. , Enquist L. W.
Published: August 2008

Pseudorabies virus encodes a membrane protein (Us9) that is essential for the axonal sorting of virus particles within neurons and anterograde spread in the mammalian nervous system. Enhanced green fluorescent protein (GFP)-tagged Us9 mimicked the trafficking properties of the wild-type protein in nonneuronal cells. We constructed a pseudorabies virus strain that expressed Us9-GFP and tested its spread capabilities in the rat visual system and in primary neuronal cultures. We report that Us9-EGFP does not promote anterograde spread of infection and may disrupt packing of viral membrane proteins in lipid rafts, an essential step for Us9-mediated axonal sorting.
Oseltamivir-Resistant Influenza A Viruses Are Transmitted Efficiently among Guinea Pigs by Direct Contact but Not by Aerosol
Authors: Bouvier Nicole M. , Lowen Anice C. , Palese Peter
Published: August 2008

Influenza viruses resistant to the neuraminidase (NA) inhibitor oseltamivir arise under drug selection pressure both in vitro and in vivo. Several mutations in the active site of the viral NA are known to confer relative resistance to oseltamivir, and influenza viruses with certain oseltamivir resistance mutations have been shown to transmit efficiently among cocaged ferrets. However, it is not known whether NA mutations alter aerosol transmission of drug-resistant influenza virus. Here, we demonstrate that recombinant human influenza A/H3N2 viruses without and with oseltamivir resistance mutations (in which NA carries the mutation E119V or the double mutations E119V I222V) have similar in ovo growth kinetics and infectivity in guinea pigs. These viruses also transmit efficiently by the contact route among cocaged guinea pigs, as in the ferret model. However, in an aerosol transmission model, in which guinea pigs are caged separately, the oseltamivir-resistant viruses transmit poorly or not at all; in contrast, the oseltamivir-sensitive virus transmits efficiently even in the absence of direct contact. The present results suggest that oseltamivir resistance mutations reduce aerosol transmission of influenza virus, which could have implications for public health measures taken in the event of an influenza pandemic.
MICROBIAL GROWTH FACTORS IN RELATION TO RESISTANCE OF FLAX VARIETIES TO FUSARIUM WILT
Authors: Lochhead A. G. , Cook F. D.
Published: August 2008

A comparison was made of growth factor requirements and growth factor synthesizing capacity of bacteria from the root surface and from the seeds of flax varieties resistant and susceptible, respectively, to wilt caused by Fusarium oxysporum f. lini. The percentage of bacteria from both root and seed which required growth-promoting substances was greater with the resistant ('Bison') than with the susceptible ('Novelty') variety. On the other hand bacteria capable of synthesizing growth factors were proportionately more abundant with the susceptible variety. The findings indicate a more pronounced rhizosphere effect exerted by the susceptible than by the resistant variety, and point to circumstances that favor a greater accumulation (or 'turnover') of vitamins and related substances at the root surface of susceptible plants.Two strains of Fusarium oxysporum f. lini capable of inducing wilt required no vitamins for growth; thiamine had a depressing effect. Both strains were able to synthesize various growth factors, though in different degree. Culture filtrates of bacteria from roots of the two varieties of flax showed no difference in their effect on growth of Fusarium; however, bacteria from the resistant variety showed somewhat greater ability to depress Fusarium than those from the susceptible. Though the findings do not constitute evidence of any relationship between differences in growth factor relationships to pathogenic potential of Fusarium, they suggest the value of considering growth-promoting substances in studies of the effect of nutrition on the activity of soil-borne pathogens.
SPECIATION AND BASIC CHROMOSOME NUMBER IN THE GENUS CELOSIA
Authors: Grant William F.
Published: August 2008

A new allopolyploid species of Celosia, namely, C. whiteii, collected in Malaya and originating from a natural cross between C. argentea L. (2n = 72) and C. cristata L. (2n = 36), has been described and the somatic chromosome number determined as 2n = 108. A somatic chromosome number of 2n = 18 has been determined for another species of Celosia, namely, C. trigyna L. The basic chromosome number for the genus has been determined as nine. Of the four species of Celosia so far studied cytologically, each represents a different level of ploidy, from diploid (2x) to dodecaploid (12x).
CONTROL OF CHLOROPHYLL CONTENT BY DAYLENGTH IN LEAVES OF MARQUIS WHEAT
Authors: Friend D. J. C.
Published: August 2008

The maximal chlorophyll contents reached during the growth of each of the first three leaves of Marquis wheat increased linearly with daylength, when the plants were grown from germination under illumination of 1750 ft-c intensity for daily periods of 8, 16, or 24 hours. This effect of daylength was also seen when chlorophyll concentration was expressed on a unit leaf area or fresh weight basis, and was related to increased leaf thickness at the longer daylengths. The increased chlorophyll content and concentration under long daylengths could not be duplicated by extending short daylengths with low-intensity supplementary light. Previous experiments suggest that the control of chlorophyll content by daylength is through the control of leaf thickness by the total amount of daily energy.The ratio of chlorophyll a to b in mature leaves did not vary with daylength. There was also no change in the maximal chlorophyll concentration of leaves mature at the time of floral initiation compared with those mature in the vegetative stage of development.
COMPARATIVE RESPONSE OF TWO SAPROPHYTIC AND TWO PLANT PARASITIC SOIL FUNGI TO TEMPERATURE, HYDROGEN-ION CONCENTRATION, AND NUTRITIONAL FACTORS
Authors: Ward E. W. B. , Henry A. W.
Published: August 2008

The behavior of two soil saprophytes, Trichoderma viride and Trichocladium asperum, and two root-infecting fungi, Ophiobolus graminis and Fomes annosus, was compared under various conditions in laboratory culture.On an agar-solidified organic medium optimum temperatures for growth were approximately: T. viride 25–30 °C, T. asperum 20–25 °C, O. graminis 20–25 °C, F. annosus 25 °C. T. viride rapidly outgrew the other fungi in the optimum range but this relationship changed at lower temperatures, its growth rate being equalled by that of O. graminis at 10 °C. T. viride was the only fungus to grow at 35 °C. In a synthetic liquid medium adjusted to pH values from 3.0–7.0 with a citrate–phosphate buffer, growth of O. graminis and F. annosus was sharply reduced at pH values below 5.0. T. viride made good growth at pH 3.1 and reduction in growth of T. asperum occurred only below pH 4.0. Both parasites required thiamine for growth in a synthetic medium and O. graminis also required biotin; in addition they showed a preference for organic as opposed to inorganic nitrogen sources. T. viride and T. asperum grew well with KNO3 as nitrogen source and neither required vitamins. D-Glucose, D-fructose, and D-mannose were readily utilized, and D-arabinose poorly utilized, by all four fungi. Utilization of other hexoses, pentoses, disaccharides, and polysaccharides varied considerably between the fungi.The relationship of the results obtained to the observations of others on the ecology of soil fungi is discussed and the possibility that combinations of physical and nutritional factors may favor specific fungi in the soil is considered.
INFECTION OF SCOTS PINE ROOTS BY FOMES ANNOSUS
Authors: Wallis G. W.
Published: August 2008

A method for in situ inoculation of Scots pine roots with Fomes annosus is described. Replacement of the fungus within the inoculum and rate of movement of the fungus on to the root surface were two important considerations in the development of a successful inoculation technique. Preliminary observations on host vigor, food-base size, and resin production as factors influencing growth of F. annosus are noted.In laboratory and field trials, spores of Fomes annosus caused infection of Scots pine roots only when sown on woody tissues exposed by cutting. A method is described whereby it was possible to observe development of spores on the surface of pine roots. The influence of microbiological and nutritional factors on infection of roots by F. annosus spores is discussed.
THE RELATION OF BARK MOISTURE TO THE DEVELOPMENT OF CANKER DISEASES CAUSED BY NATIVE, FACULTATIVE PARASITES: IV. PATHOGENICITY STUDIES OF CRYPTODIAPORTHE SALICELLA (FR.) PETRAK, AND FUSARIUM LATERITIUM NEES., ON POPULUS TRICHOCARPA TORREY AND GRAY, P. 'ROBUSTA', P. TREMULOIDES MICHX., AND SALIX SP.
Authors: Bier John E.
Published: August 2008

In the field, Cryptodiaporthe salicella has been found only on Salix sp., and Fusarium lateritium on nursery-grown Populus trichocarpa Torrey and Gray. However, the pathogens for these diseases attacked P. trichocarpa, P. 'robusta', P. tremuloides Michx., and Salix sp. when inoculations were made on cuttings which were allowed to dry gradually in a dormant condition. The development of the diseases in the field and in the laboratory was related to the moisture content of the host bark. Canker growth occurred only when the relative turgidity of the bark was below 80%. The possibility of employing similar methods of investigation for the discovery and evaluation of canker diseases of importance in disease-testing programs is discussed.
THE RELATION OF BARK MOISTURE TO THE DEVELOPMENT OF CANKER DISEASES CAUSED BY NATIVE, FACULTATIVE PARASITES: V. ROOTING BEHAVIOR AND DISEASE VULNERABILITY IN CUTTINGS OF POPULUS TRICHOCARPA TORREY AND GRAY, AND P. 'ROBUSTA'
Authors: Bier John E.
Published: August 2008

In cuttings from 1-year-old shoots of Populus trichocarpa Torrey and Gray and P. 'robusta', correlations were found to exist between the degree of vigor as expressed by the production of basal callus and the associated wound roots, and the relative turgidity of the bark at the time of harvest or planting. The ability to produce basal callus and wound roots decreased in cuttings with relative turgidities below the 80% level, and many were killed by the development of basal cankers caused by Fusarium lateritium Nees and Cytospora chrysosperma. (Pers.) Fr. Therefore, the bark moisture level in cuttings was indicative of their ability to produce basal callus and wound roots in addition to their vulnerability to these canker diseases caused by facultative parasites.In uniform-sized cuttings of P. 'robusta' no relation was found between the production of morphological roots developing from root primordia, and the bark moisture level, or the percentage of plants which survived. Larger numbers of morphological roots developed on cuttings from the basal and, consequently, older parts of stems.The production of basal callus and wound roots in P. 'robusta' was found to be related to the total weight of cuttings of uniform size, which suggested that weight determinations in the field may provide useful guides into the general level of vigor of dormant nursery stock and stored material.
VERTICILLIUM DISEASE OF STRAWBERRIES
Authors: Basu P. K.
Published: August 2008

An intensive study was made of the morphology, cultural characters, and infection capabilities of 18 isolates of Verticillium. These were in part isolated from different Verticillium hosts occurring in the Niagara Peninsula and the balance were obtained as named stock cultures from different herbaria. In terms of their pathogenicity to strawberries, resistant and susceptible tomatoes, and eggplants, the isolates comprised a number of races whose virulence ranged from lethal to very mildly pathogenic. Under the experimental conditions, current-year runner plants of strawberries proved to be virtually immune from infection, in contrast to normal overwintered plants. The symptoms on the strawberry are variable and diagnosis should be confirmed by isolation of the pathogen, for which a technique was evolved. Morphologically the isolates varied considerably and in culture the color ranged from white through gradually deepening gray to black. At the extremes the differences were conspicuous but were so intergrading in the group as a whole that the isolates are regarded as belonging to one variable species which, because of priority, must be called Verticillium albo-atrum R. and B.
SELF-FERTILITY IN THE SCLEROTINIACEAE
Authors: Groves J. Walton , Elliott Mary E.
Published: August 2008

Nine species representing five genera of the Sclerotiniaceae were found to be self-fertile. These are as follows: Ciboria acericola sp. nov., C. acerina Whetz. & Buchw., C. amentacea (Balb. ex Fr.) Fckl., C. betulicola sp. nov., C. caucus (Rebent. ex Fr.) Fckl., Ciborinia erythronii (Whetz.) Whetz., Rutstroemia paludosa (Cash & Davidson) comb. nov., Septotinia podophyllina Whetz., and Verpatinia calthicola Whetz. Two new species and one new combination are proposed and validating Latin diagnoses are provided for Ciboria acerina, the genus Septotinia, and S. podophyllina.
Observations on anthocyanin pigmentation in seedlings and mature plants of Impatiens capensis and its possible role as a determinant of floral form
Authors: Nozzolillo Constance
Published: August 2008

Plants of Impatiens capensis Meerb. were observed in the field for the presence or absence of anthocyanin pigmentation. Seeds were collected at a site where cross-pollination between plants with orange spotted flowers (forma capensis) and plants with orange unspotted flowers (forma immaculata) was highly likely to have occurred. Spotted and unspotted flowers were found to possess a similar array of carotenoids in similar concentrations, but cyanidin glycosides were found only in extracts of spotted flowers. Progeny of spotted flowers were 98% anthocyanin-producing in root tips, roots, hypocotyl, and cotyledons of seedlings (photographs of the unusual development of seedlings are presented). Only a minority of progeny of unspotted flowers were cyanic. One of these cyanic offspring of unspotted flowers was grown to maturity and produced 75% cyanic seedlings when selfed. Under cultural conditions where crossing had been prevented, spotted-flowered plants produced only cyanic seedlings and unspotted-flowered plants produced only acyanic seedlings. All these observations suggest that the presence of anthocyanin pigmentation is a dominant, heritable characteristic of I. capensis forma capensis and its absence a recessive, heritable characteristic of I. capensis forma immaculata and that it is this feature only that distinguishes these two formae.
Diurnal gross photosynthetic patterns and potential seasonal CO2 assimilation in Cladonia stellaris and Cladonia rangiferina
Authors: Moser Thomas J. , Nash III Thomas H. , Link Steven O.
Published: August 2008

The daily, in situ gross photosynthetic patterns of Cladonia stellaris (Opiz.) Pouz. & Vězda. and Cladonia rangiferina (L.) Wigg. were monitored during portions of the 1977, 1978, and 1979 growing seasons at Anaktuvuk Pass, Alaska. Photosynthetic activity in both species closely paralleled atmospheric moisture status, where peak photosynthetic rates were attained during or following sporadic summer rain. In addition, thallus absorption of moisture during extended periods of high atmospheric water vapor content gave rise to short periods of minimal photosynthetic activity. During late evening and early morning hours moistened thalli exhibited minimal or no photosynthetic activity, coinciding with consistent attenuation in solar radiation during these periods. Photosynthetic activity was not homogeneous throughout the thallus. The greatest activity occurred in the apical regions and decreased progressively into the basal regions. The apical 10-mm regions of C. stellaris and C. rangiferina thalli accounted for approximately 50% of their photosynthetic capabilities. The potential gross CO2 assimilation of the apical 10-mm regions over 72 days of the 1978 growing season was estimated at approximately 35 g CO2∙m−2 and 16 g CO2∙m−2 for C. stellaris and C. rangiferina, respectively.
Somatic embryogenesis and plant regeneration from leaf explants and cell suspensions of Solanum melongena (eggplant)
Authors: Gleddie S. , Keller W. , Setterfield G.
Published: August 2008

High frequencies of somatic embryogenesis evaluated on the basis of average embryo yield per explant were observed on leaf explants of Solanum melongena (L.) (eggplant) after 21 days of culture on a modified Murashige and Skoog medium. Callus proliferation and embryogenesis occurred in the presence of 1-naphthaleneacetic acid (NAA), whereas only callus induction occurred in the presence of the other auxins. Maximal embryo yields were obtained at 10 mg/L NAA. Although cytokinins inhibited the NAA-induced embryogenic response, they acted synergistically to promote callus growth. The frequency of embryogenesis on leaf explants was shown to be under the control of the nitrogen content of the medium. Both NH4+ and NO3− were essential for embryogenesis and an optimal ratio of 2:1 (NO3−:NH4+) was established. The optimal sucrose concentration of the medium was 0.06 M and both elevated and reduced sucrose levels inhibited embryogenesis. Seven cultivars showed significant quantitative differences in their capacities to form embryos, although all were embryogenic. Cell suspension cultures were also embryogenic, when grown under conditions which stimulated embryogenesis in leaf explants. Somatic embryos taken from leaf callus or cell suspensions and cultured on hormone-free medium gave rise to plants which set seed when transferred to the greenhouse. Shoot organogenesis was observed on leaf explants which were cultured in the presence of either of four cytokinins. Shoots were rooted on hormone-free medium and mature plants were subsequently obtained.
Studies of the growth and mineral nutrition of barley varieties. I. Effect of potassium supply on the uptake of potassium and growth
Authors: Siddiqi M. Yaeesh , Glass Anthony D. M.
Published: August 2008

The effects of [K+] (in 1 to 100 μM range) upon uptake, accumulation, and utilization of K+ and upon absolute and relative growth rates were studied in 27 barley varieties. An external concentration of 1 μM was inadequate for growth and severe deficiency symptoms were observed. Above 5 μM no deficiency symptoms were apparent; however, there were substantial intervarietal differences in their responses to varying [K+]. Four varieties were studied in greater detail. At low [K+], the varieties with higher absolute and relative growth rates also had higher K+ uptake rates, higher root weight ratios, and higher efficiencies of K+ utilization.
Dosage de la chitine sur des ectomycorhizes de pin maritime (Pinus pinaster) à Pisolithus tinctorius : évaluation de la masse mycélienne et de la mycorhization
Authors: Plassard Claude , Mousain Daniel , Salsac Louis
Published: August 2008

To estimate the intensity of mycorrhizal development of maritime pine (Pinus pinaster Soland. in Ait.) associated with Pisolithus tinctorius (Pers.) Coker et Couch., two methods were used: the assay of fungal chitin after acid or alkaline hydrolysis; the measure of absorption of fungus pigments extracted by means of acetone. The products of the hydrolysis of the chitin are assayed by a colorimetric method. The alkaline hydrolysis enables us to directly assay the fungal chitosan; after acid hydrolysis the tissues of pine produce some substances reacting colorimetrically and the absorption due to chitin is estimated from the total absorption of the hydrolysate. There are good correlations between these different types of determination themselves and between the determination and the counting of the mycorrhizae.
The relationship between some Eurasian and American species of Bromus section Pnigma as determined by the karyotypes of some F1 hybrids
Authors: Armstrong K. C.
Published: August 2008

Interspecific hybrids were successfully produced, using embryo culture, between Eurasian and American species of Bromus section Pnigma. Cytological observations on satellite type and chromosome size suggest that the two Eurasian species B. benekenii (Lange) Trimen and B. ramosus Huds. are more closely related to the American species (B. ciliatus L., B. latiglumis Hitchc., B. pacificus Shear, and B. richardsonii Link) than to other Eurasian species. It is suggested that the section Pnigma may contain two distinct groups of species that can be separated on the basis of chromosome size.
Effects of light intensity and CO2 concentration on the kinetics of 1st month growth and nitrogen fixation of alfalfa
Authors: Macdowall F. D. H.
Published: August 2008

Medicago sativa L. cv. Algonquin seedlings were grown for 28 days in growth rooms at several intensities of light and concentrations of CO2. Optimal or deficient NO3− concentrations were provided, the latter with or without inoculation and nodulation by Rhizobium meliloti str. 102F70 (Burton). All growth coefficients (k1′) were hyperbolically dependent on the intensity of light. Light saturation of plant k1′ was achieved, but the k1′ for nitrogenase development the highest in value, was not light saturated at high CO2 by the highest light intensity (555 μE∙m−2∙s−1). That intensity also did not saturate the photosynthesis of plants grown at that intensity nor the amount (yield) and absolute rate of plant growth. The latter were very much reduced at intensities below the compensation point (100 μE∙m−2∙s−1) of net photosynthesis. The data for k1′ at low light intensity indicated that photosynthate was utilized with equal efficiency for N2 and NO3− reduction. Fourfold enrichment of CO2 concentration did not influence the k1′ of plant growth in optimum NO3− and high light intensity but increased the yield by 78%. In the absence of high NO3− concentration, however, it nearly doubled the nitrogenase growth k1′, to a doubling time of 1.4 days, increased the nodule yield fourfold, the plant (symbiotic) yield threefold, and N content twofold. Sevenfold enrichment of CO2 was inhibitory to yields of N-deficient plants and nodules. The previous conclusion that added (combined) N chiefly limited seedling growth was supported by the lack of effect on plant k1′ of the stimulation of photosynthesis by high light intensity and CO2 concentration. A limitation on the value of the k1′ for shoot elongation in deficient combined N raised CO2 and high light was relieved symbiotically.
Effects of two photoperiod treatments on leaf photosynthesis throughout ontogeny in 'Fergus' barley
Authors: Ma P. C. , Hunt L. A.
Published: August 2008

Leaf photosynthesis was measured throughout ontogeny for barley plants (Hordeum distichum L. emend. Lam. cv. Fergus) grown under 12- and 24-h photoperiods. Plants were grown in silica and irrigated with one-half strength of a modified Hoagland solution at 700 μE m−2 s−1. The 12-h photoperiod was extended to 24 h with low-intensity incandescent lamps (10 μE m−2 s−1). The ontogenetic pattern of change in the leaf carbon dioxide exchange rate (CER) differed between photoperiodic treatments. Under the 12-h photoperiod CER increased from leaf 1 to leaf 5 and declined to a minimum for leaf 9; whereas CER under the 24-h photoperiod continued to increase with ascending leaf position. Both stomatal and residual, which was six times larger, resistance components were responsible for the changes in CER. The pattern of change in CER with individual leaf age differed between stages of plant development but was similar at a given stage of development between photoperiodic treatments. During the vegetative phase, CER decreased slowly for 5 days from full expansion and rapidly thereafter, while during the stem elongation phase CER decreased rapidly soon after full expansion. During the grain development phase in the 24-h treatment, two plateaus were observed in CER of the flag leaf. It is clear that photoperiodic treatments affect leaf photosynthesis not only directly but also indirectly through changes in the developmental pattern.
Évolution anatomique des tissus foliaires de canne à sucre (Saccharum sp.) cultivés in vitro
Authors: Bonnel E. , Demarly Y. , Essad S.
Published: August 2008

Young rolled leaves of sugarcane (Saccharum sp., variety Co 1007) are cultivated in vitro on a synthetic medium. The first anatomical modifications appear in nonlignified, subepidermal fibers, on the external side of the leaves, by the 3rd day. Cellular growth precedes proliferation. Thereafter the process of dedifferentiation affects all of the tissues of the leaves. Proliferations of epidermal tissue, subepidermal fibers, bundle sheath cells, and vascular tissue give rise, respectively, to the epidermal tissue, peripheral cambial zone, parenchyma, and vascular tissues of the calluses. Thus, organogenic specificity of each foliar tissue is preserved.
Light and electron microscopy of embryo development in perennial and annual Medicago species
Authors: Sangduen N. , Kreitner G. L. , Sorensen E. L.
Published: August 2008

The embryo of perennial Medicago sativa L. and annual M. scutellata (L.) Mill. have similar growth stages, but the perennial embryo is smaller and its rate of growth is slower than that of the annual by about 3 days. Transfer cells in the suspensor and embryo sac of late heart stages suggest different major pathways of nutrient flow in the two species. Transfusion tissue at the base of the embryo sac in the ovule of M. scutellata may facilitate solute transport and promote rapid embryo growth. Plastids in the suspensor cells of heart and late heart stages of the two species contain a dense matrix, membrane-bounded plastid vacuoles, starch, and a dense core. The plastid core in M. sativa has stacked tiers of straight tubules about 24 nm in diameter, suggesting that these specialized plastids are like tubular chromoplasts. Plastid vacuoles arise from the periphery of dense cores and apparently discharge electron-translucent contents into the suspensor cytoplasm. Plastid vacuoles may play a role in suspensor metabolism and thus influence embryo development.
Structure and dynamics of conifer–lichen stands on rock outcrops south of Lake Abitibi, Quebec
Authors: Clayden Stephen , Bouchard André
Published: August 2008

The plant communities of shallow soil and bare rock on outcrops of rhyolite and basalt are described for the area south of Lake Abitibi, Quebec. Analysis of data from 34 sample plots by means of reciprocal averaging ordination indicates that most of the intersite variation in composition and structure is due to succession. The two rock types have distinctive assemblages of epilithic lichens and bryophytes but their thin soil communities do not differ significantly. Soil coverage and depth are controlled in part by bedrock slope and microtopography and increase uniformly in relation to the postfire age of the outcrop tree stands. The ground layer macrolichens and bryophytes undergo a succession of dominant species and growth forms, but the open-crown coniferous stands show little evidence of self-regeneration through tree seedling establishment or vegetative propagation. Stands of different age dominated by Pinus banksiana and by Picea mariana do not form a clear successional sequence. Fire recurrence prevents complete closure of the outcrop tree canopy.
An electron microscope study of initiation of infection by conidia of Harposporium oxycoracum, an endozoic nematophagous Hyphomycete
Authors: Saikawa Masatoshi , Totsuka Junko , Morikawa Chiharu
Published: August 2008

Infective conidia of an endozoic nematophagous hyphomycete, Harposporium oxycoracum Drechsler, were examined by means of electron microscopy. Each of the conidia is very narrow and has a sharply pointed distal and slightly swollen basal end. The swollen basal end was shown, in ultrathin sections stained with ruthenium red en bloc, to be an electron-dense mass of fibrils (ca. 2–3 μm in diameter). The fibrils, thought to be derived from the conidial cell wall, were densely aggregated and were surrounded by a network of more sparsely aggregated fibrils spreading from the fibrous mass of the conidial base. The spreading fibrils seemed to correspond to the mucous droplet observed under the light microscope. It was also found in the present study that the conidia of the fungus were swallowed by nematodes into their lower gut. On germination in the lower gut, a narrow germ tube 5–6 μm wide developed from the convex side of the conidium and produced a simple pore septum at the site of penetration to delimit the empty conidium.
Ectomycorrhizae in the Agaricales and Gasteromycetes
Authors: Miller Jr. Orson K.
Published: August 2008

Over the past decade much progress has been made in an effort to determine which fungi are mycorrhizal symbionts. It is now apparent that one ectomycorrhizal or ectendomycorrhizal host is often able to form mycorrhizae with a wide variety of higher fungi. Evidence is presented which supports the hypothesis that fungal succession occurs as the host matures. In addition, fungi which are normally ectomycorrhizal may sometimes form endomycorrhizae on different hosts or under altered ecological conditions. There has also been much evolution in fruiting-body form and mode of spore discharge especially under severe montane or desert conditions. As a result patterns are emerging in the Homobasidiomycetes at the order, family, and generic level in the evolution of the mycorrhizal habit. Spore morphology, habitat, and distribution are listed and discussed in relation to the biological role of the fungi.
Utilization of vesicular–arbuscular mycorrhizal fungi in agriculture
Authors: Menge J. A.
Published: August 2008

Commercial use of vesicular–arbuscular mycorrhizae (VAM) may be an alternative to rising agricultural energy and fertilizer costs. Vesicular–arbuscular mycorrhizae may be able to increase crop yields while reducing fertilizer and energy inputs. Since mycorrhizal fungi are naturally present in most soils, their unique fertilizer abilities are already being utilized by most crop plants. Commercial uses of VA mycorrhizal fungi are therefore currently restricted to situations where the natural populations of VAM fungi have been destroyed or damaged such as in fumigated or chemically treated areas, greenhouses, and disturbed areas such as coal spoils, strip mines, waste areas, or road beds. Commercial production of VAM inoculum is presently being attempted at several locations in the U.S. Vesicular–arbuscular mycorrhizal inoculum is produced by growing VAM fungi on the roots of suitable host plants under aseptic greenhouse conditions The inoculum consists of the host-plant growth medium and host roots associated with VAM hyphae and spores which have been ground and dried. Most large-scale uses of VAM involve the establishment of the mycorrhizae on seedlings which will be transplanted to the field. Large-scale methods for direct inoculation with VAM have not yet been devised, but in small trials, layering, banding, broadcasting, and pelleting seed with VAM inoculum have proved effective. Methods for determining what soils are most likely to benefit from applications of VAM fungi are available. The potential for employing VAM fungi on a wide scale in agriculture is dependent on the development of crop growth-promoting strains of VAM which are superior to native soil populations of VAM fungi.
Phylogenetic interrelationships in the order Primulales, with special emphasis on the family circumscriptions
Authors: Anderberg Arne A. , Ståhl Bertil
Published: August 2008

Cladistic parsimony analyses, based on morphological data, have been undertaken with the purpose of identifying major monophyletic groups and phylogenetic interrelationships within the Primulales. Actinidia (Actinidiaceae, Ericales) and three genera from two families of the Ebenales (Diospyros of the Ebenaceae and Manilkara and Monotheca of the Sapotaceae) were used as outgroups in the analyses. The results indicate that the Primulaceae, Theophrastaceae, and Myrsinaceae (excluding Maesa) represent three major monophyletic groups. The Myrsinaceae were found to be paraphyletic, with the majority of taxa forming a monophyletic group but with the genus Maesa constituting the sister group of the Primulaceae. It is proposed that Maesa should be raised to the rank of family to obtain strictly monophyletic groups in the Primulales. The genera Aegiceras and Coris, for which family affinities have been controversial, are well nested within the families Myrsinaceae and Primulaceae, respectively. Key words: Primulales, Theophrastaceae, Myrsinaceae, Primulaceae, morphology, taxonomy, phylogeny, cladistics, classification.
Effets des contraintes (vents et embruns) sur la composition et la structure de la végétation des pentes drainées de l'île de la Possession (archipel Crozet, subantarctique)
Authors: Carcaillet Christopher
Published: August 2008

A study of the vegetation communities along two transects on the well drained slope of the Possession Island (subantarctic island, Indian Ocean) was carried out. The aim of this study was to investigate the structure of the vegetation under permanent pressure from gales and salt sprays and where there was no major perturbation. In the areas protected from gales, a Blechnum pennamarina community dominates. This fern hinders the vegetation dynamics in two ways : (i) by forming a very dense canopy that prevents sunlight from reaching shorter plants (passive competition) and (ii) by the accumulation of thick litter resulting from dead fronds. This community thus acts as the "inhibition" model of Connell and Slatyer. In areas exposed to gales and salt spray, B. pennamarina partly or completley disappears. The soil surface is consequently covered with several bryophytes and Azorella selago that form a mosaic on the soil surface. The vegetation dynamics end at this stage, despite the ability of B. pennamarina to colonize moss litter. The bryophyte community probably represent a stational climax stage acting as a "facilitation" model to B. pennamarina in an area protected from gales. It has therefore been concluded that the fernbrake community constitutes the optimal vegetation development on the well drained slopes of the Possession Island. Key words: climatic pressure, community ecology, bryophytes, Blechnum pennamarina, transect.
Arbuscular mycorrhizae of Acer saccharum in different soil types
Authors: Klironomos John N.
Published: August 2008

Differences in propagule levels and in the colonization of Acer saccharum feeder roots by arbuscular mycorrhizal fungi in maple forests distributed across three different soil types (brunisols, luvisols, podzols) were investigated. All forest stands were located in southern Ontario. Acer saccharum was the dominant tree species, making up at least 75% of all trees. Results show that arbuscular mycorrhizae can dominate in different soil types, even in podzolic soils with moder-type humus, which typically support ectomycorrhizal associations. In fact, total hyphal colonization of A. saccharum roots and the capacity of the soil to initiate infection units were highest in the podzolic soils compared with those in brunisolic and luvisolic soils. In brunisolic soils, the roots exhibited high arbuscular colonization, low coil colonization, low vesicular colonization, and relatively moderate sporulation levels. In luvisolic soils, colonization was similar to that of brunisols; however, spore densities were lower. Roots in podzolic soils showed very different trends, with a low occurrence of arbuscules, high levels of hyphal coils and vesicles, and much higher spore densities. Soil type can account for much of the variability in arbuscular mycorrhizal structure and functioning that occurs among different locations. Key words: arbuscular mycorrhizae, Acer saccharum, brunisol, luvisol, podzol.
Size dependency of sexual reproduction and of clonal growth in two perennial plants
Authors: Schmid Bernhard , Bazzaz Fakhri A. , Weiner Jacob
Published: August 2008

We compared the size dependency of sexual reproduction and clonal growth in two clonal perennials that inhabit old fields, Aster lanceolatus and Solidago canadensis. In both species there was a threshold size required for sexual reproduction to occur, and above that threshold reproductive output increased linearly with vegetative mass. Biomass allocated to clonal growth was also highly correlated with vegetative mass in both species, but there was no evidence of a threshold size for clonal growth. The absence of a clear size threshold for clonal growth emphasizes the similarity between clonal growth (vegetative reproduction) by rhizomes and growth of other vegetative parts, as opposed to sexual reproductive allocation. In both species there were differences in the allocation patterns of plants derived from seeds and those derived from rhizomes. Although seed- and rhizome-derived plants did not differ in phenology and size, the latter allocated more biomass to sexual reproduction and clonal growth in both species. Key words: clonal growth, size dependency, reproduction, Aster lanceolatus, Solidago canadensis, size threshold.
Glutathione status of the bilberry (Vaccinium myrtillus) as a function of plant phenology and artificial herbivory
Authors: Taulavuori Erja , Tolvanen Anne
Published: August 2008

The glutathione status of the deciduous dwarf shrub bilberry (Vaccinium myrtillus L.) was investigated as a function of plant phenology and artificial herbivory. The concentration of the total, reduced, and oxidized glutathione in buds or leaves was determined in control and damaged plants at the time of bud break, flowering, and berry production. Short- and long-term response of the treatment was observed by harvesting the ramets either on the day following or several weeks after the herbivory treatment. There were marked differences in the glutathione status between ramets of different phenological states. More than 90% of glutathione was in the reduced form at bud break and during the flowering period, when the total concentration also peaked. The proportion of the oxidized form increased, up to 80%, in autumn, when the level of total and reduced glutathione had decreased. Reduced glutathione was possibly needed in reactions of protein synthesis during the active growth period, whereas it may have been translocated to storage tissues before winter. Herbivory treatment had no significant effect on glutathione status, either on the short or the long time scale. Possible reasons for this unexpected result are discussed. The observed pattern in the glutathione status is compared with other studies that investigated the phenology of the bilberry. Key words: glutathione, herbivory, phenology, Vaccinium.
New techniques and applications for epi-illumination light microscopy
Authors: Lacroix Christian R. , MacIntyre Judith
Published: August 2008

This modification to the technique of epi-illumination light microscopy makes use of a new system of lenses that replaces expensive and not readily available dipping cone objectives. The newer objectives offer at least comparable resolution and depth of field, along with simple preparation procedures. An epi-illumination system is a good intermediate between the stereo microscope and a scanning electron microscope, offering magnification at high power that can aid in evaluation of potential scanning electron microscope specimens, as well as the time- and material-saving feature of being able to eliminate unsuitable scanning electron microscope specimens. Key words: technique, epi-illumination, morphogenesis, vegetative apex, primordium, staining.
Stock Structure of Scotian Shelf Flatfish as Inferred from Ichthyoplankton Survey Data and the Geographic Distribution of Mature Females
Authors: Neilson J. D. , DeBlois E. M. , Hurley P. C. F.
Published: August 2008

Data on egg distributions and timing of appearance of maximum egg densities were examined to determine the stock structure of three commercially important flatfish occurring on the Scotian Shelf: American plaice (Hippoglossoides platessoides), yellowtail flounder (Limanda ferruginea), and witch flounder (Glyptocephalus cynoglossus). Distributions of sexually mature females obtained from research vessel surveys were used to further support inferences concerning spawning location. Using such information, more than one stock of both American plaice and yellowtail flounder appear to occur on the Scotian Shelf, but no conclusions could be drawn concerning witch flounder. In the case of American plaice and yellowtail flounder, the existing means of geographic aggregation of data for stock assessment purposes do not appear to adequately represent stock structure. Little or no advection of eggs and larvae appears to occur on the Scotian Shelf, supporting the hypothesis that current-driven retention areas promote stock discreteness in that region. It was concluded that ichthyoplankton surveys can be a valuable adjunct to more traditional means of stock identification.
Within-River Spawning Migration of Atlantic Salmon (Salmo salar)
Authors: Heggberget Tor G. , Hansen Lars P. , Næsje Tor F.
Published: August 2008

The migration pattern of adult spawners of Atlantic salmon (Salmo salar) in two Norwegian streams was analysed by ultrasonic and mechanical tagging to investigate within-river migration. Salmon were tagged in the estuary as they approached the river before spawning. They displayed a systematic and directional upstream pattern of movement in the river. Seventy-one percent of the fish transplanted 6 km downstream from the capture site about 2 mo before spawning returned to the donor area. Fish transported 7 km upstream from the capture site exhibited a low degree of backtracking to the donor site (one of seven fish). Mechanical tagging of salmon on spawning grounds showed that both male and female spawners released 150 and 600 m upstream from the spawning area were able to return to the original site of spawning with a mean precision of 87%. In both streams, the migration pattern and the return to original site of capture support the hypothesis of local homing of Atlantic salmon, although some fish stray to other areas of the stream.