bluuebunny/crossref_metadata_2025 huggingface dataset:
Photosynthesis in stem rust-infected, resistant and susceptible near-isogenic wheat leaves
Authors: Moerschbacher B. M. , Vander P. , Springer C. , Noll U. , Schmittmann G.
Published: December 2007

Secondary leaves of three near-isogenic lines of the wheat (Triticum aestivum) cultivar Prelude, differing in their degree of resistance to the wheat stem rust fungus (Puccinia graminis f.sp. tritici) race 32, were inoculated with uredospores of the fungus 12 days after germination. Photosynthetic O2 evolution, chlorophyll content, 3-phosphoglycerate content, and the gel electrophoretic pattern of thylakoid membrane proteins were investigated in rust-infected and healthy plants of the fully susceptible isoline Prelude, the moderately resistant isoline Prelude-Sr24, and the highly resistant isoline Prelude-Sr5. The rate of net photosynthesis, expressed per unit leaf area, was not significantly changed in any of the three near-isogenic lines during the early stages of infection, then increased slightly in the highly resistant line, while decreasing in the moderately resistant and fully susceptible lines. In the moderately resistant plants, this decrease continued linearly until 8 days after inoculation when no photosynthetic activity was detectable. In the susceptible line, the decrease gradually slowed down around 4–6 days after inoculation and photosynthetic activity remained constant thereafter. The chlorophyll content decreased only slightly during infection in highly resistant plants, but chlorophyll eventually disappeared completely from the infected, moderately resistant plants. The initially similarly strong decrease in chlorophyll content in the susceptible plants gradually came to a halt during the later stages of infection. Expressed per unit chlorophyll, photosynthetic O2 evolution increased slightly in highly resistant plants, remained unchanged in moderately resistant plants, and decreased to a stable level in the susceptible plants. The infection-induced changes in the 3-phosphoglycerate content closely resembled the changes in O2 evolution. No infection-induced changes were observed in the thylakoid membrane proteins from leaves of all three isolines. The results are discussed in relation to previously described changes in the primary metabolism of the three near-isogenic wheat lines after inoculation with the stem rust fungus, namely polyamine content, fructose-2,6-bisphosphate content, respiratory activity, invertase activity, and assimilate contents. Key words: Triticum aestivum, Puccinia graminis f.sp. tritici, O2 evolution, chlorophyll, 3-phosphoglycerate, thylakoid membrane proteins.
Small-subunit rRNA gene sequences from representatives of selected families of the Gigartinales and Rhodymeniales (Rhodophyta). 1. Evidence for the Plocamiales ord.nov.
Authors: Saunders G. W. , Kraft G. T.
Published: December 2007

Nucleotide sequences of the nuclear, small-subunit (SSU) ribosomal RNAs, as inferred from polymerase chain reaction (PCR)-amplified products, are presented for Areschougia congesta (Turner) J. Agardh (Solieriaceae), Dasyphloea insignis Montagne (Dumontiaceae), Sarcothalia crassifolia (C. Agardh) Edyvane & Womersley (Gigartinaceae), Nizymenia australis Sonder (Nizymeniaceae), Phacelocarpus peperocarpos (Poiret) Wynne, Ardré & Silva (Phacelocarpaceae), Plocamiocolax pulvinata Setchell, Plocamium angustum (J. Agardh) J.D. Hooker, Plocamium cartilagineum (Linnaeus) Dixon (Plocamiaceae), Rhodymenia linearis J. Agardh (Rhodymeniaceae), and Sphaerococcus coronopifolius Stackhouse (Sphaerococcaceae). Phylogenetic analyses of the SSU sequences between the Plocamiaceae and members of the Sphaerococcaceae, Phacelocarpaceae, and Nizymeniaceae, with which the Plocamiaceae has been associated historically, show SSU differences of between 87 and 105 nucleotides and do not indicate a close relationship. A review of anatomical knowledge of the Plocamiaceae and Pseudoanemoniaceae and new information on vegetative and tetrasporangial development in Plocamium and Plocamiocolax are presented to buttress a case for the Plocamiales ord.nov. Representatives of the Nizymeniaceae and Phacelocarpaceae differ from one another by only nine nucleotides, suggesting that these two taxa are very closely related and perhaps not distinct at the family rank. Key words: Gigartinales, PCR, phylogeny, Plocamiales ord.nov., Pseudoanemoniaceae, Rhodophyta, small-subunit rRNA, systematics.
An experimental study of the role of seedling density and neighbor relatedness in the persistence of Rumex acetosella in an old-field succession
Authors: Escarré Josep , Houssard Claudie , Thompson John D.
Published: December 2007

Patterns in flowering and biomass allocation in seedlings of Rumex acetosella L. collected from five successional old fields, from 1 year old to 15 years old, have been examined in experimental pots varying in density (1, 2, and 4 plants/pot) and neighbor relatedness (sib, nonsib, other population) to determine the effects of successional habitat variation on patterns of resource allocation. The flowering of seedlings from the successionally young populations was not affected by density, whereas for seedlings from the older populations, increased density was correlated with increased variation in flower and seed production both within and between populations. At high density, seedlings from the successionally youngest population showed the greatest allocation of resources to flowering. As a result, differentiation along the successional gradient was such that the younger populations invested a greater proportion of resources to aerial biomass, while the older populations allocated relatively more resources to vegetative propagation. These trends were maintained at high density. The results of the sibling competition treatment showed no consistent trend related to the age of the populations but were density dependent. At high density, sexual biomass was higher between nonsibs than between sibs of the same population, suggesting greater competition among related plants. Finally, the sexual biomass of individual plants was less in competition with seedlings from a different population than with seedlings from the same population. Sprout biomass showed the reverse trend. The observed differentiation between successionally different populations in resource allocation irrespective of density may account for these results. Overall, our results provide evidence for biotic specialization of R. acetosella in relation to successional habitat change. Key words: density, sibling competition, succession, trade-off, Rumex acetosella, resource allocation.
Somatic polymorphism in the achenes of Tragopogon dubius
Authors: Maxwell Christine D. , Zobel Alicja , Woodfine David
Published: December 2007

Achenes of Tragopogon dubius have previously been described as dimorphic with respect to size and colour. In this investigation we found that there is a continuum of weight change from lighter central achenes to the heavier peripheral achenes. The main component of change is the pericarp. Outer achenes may also contain larger quantities of phenolic compounds than inner achenes. The differences in mass, morphology, and chemical characteristics may be significant enough to result in differences in germination behaviour. No such differences were seen in standard laboratory germination tests, though in a greenhouse experiment, seedlings from peripheral achenes emerged later and were larger and taller than seedlings from central achenes. The presence of phenolic compounds in the fruits of T. dubius suggests that the peripheral morphs may retain viability longer in the seed bank. Key words: somatic polymorphism, heteromorphism, germination, emergence, Tragopogon.
Low levels of outcrossing in Pinus leucodermis: further evidence in artificial stands
Authors: Morgante M. , Rossi P. , Vendramin G. G. , Boscherini G.
Published: December 2007

Outcrossing rates were estimated in two artificial stands of Pinus leucodermis, a wind pollinated conifer characterized by a relatively high level of selfing. Multilocus outcrossing rates, estimated by assaying five enzyme loci, were lower than 86% in the two stands, using both dormant and germinating seeds, and not different from those observed in two natural populations located in the same area. The lack of relevant differences between single-locus minimum variance means and the multilocus outcrossing rate estimates observed in both the artificial stands indicates that most of the apparent selfing is probably caused by actual self-fertilization. The presence of a high level of self-fertilization in this species seems confirmed also in artificial stands, where the density is higher and neighbourhood structure should be less pronounced. The high level of self-fertilization found in P. leucodermis, which is probably due to the presence of a reduced number of recessive embryonic lethals as a consequence of genetic drift, could represent a selective advantage for this pioneering and precocius species. Key words: mating system, outcrossing rates, artificial stands, Pinus leucodermis.
Initial size and the competitive responses of two grasses at two levels of soil nitrogen: a field experiment
Authors: Wilson Scott D.
Published: December 2007

I tested whether initial size influenced the ability of grasses to compete against established perennial vegetation in an old field, both in plots with little competition for light and in plots with intense light competition. Seedlings of Schizachyrium scoparium (a perennial) and Setaria viridis (an annual) were assigned to three classes of initial size; small seedlings had about half the initial mass of medium seedlings, which had about half the mass of large seedlings. Seedlings were transplanted into subplots with neighbours either present or absent, within 10 plots that received either NH4NO3 or no additional nitrogen. Transplant final mass (roots and shoots) was significantly lower in the presence of neighbours and increased significantly with initial size. There was no significant interaction between competition and initial size, however, indicating that competition suppressed seedlings of all sizes to about the same extent. Further, there was no significant three-way interaction, suggesting that size did not influence competitive response more in environments where light was limiting. These results differ from pot experiments and monocultures by suggesting that initial size does not influence the ability of a plant to compete against neighbours on either nutrient-rich or nutrient-poor soils. Key words: competition, competitive response, competitive ability, size, removal experiments, nitrogen.
Lack of association between tolerance to the elm phytoalexin mansonone E and virulence in Ophiostoma novo-ulmi
Authors: Proctor Robert H. , Guries Raymond P. , Smalley Eugene B.
Published: December 2007

The effect of the elm phytoalexin, mansonone E, on linear growth of 17 fungal species was examined to determine whether the Dutch elm disease fungus Ophiostoma novo-ulmi is more tolerant of mansonone E than other fungi. Linear growth of O. novo-ulmi was less inhibited by mansonone E than that of most, but not all, other fungi examined, suggesting that O. novo-ulmi is relatively tolerant of mansonone E. To determine whether this tolerance is required for pathogenicity, we generated mutants of O. novo-ulmi with reduced tolerance to mansonone E by N-methyl-N′-nitro-N-nitrosoguanidine mutagenesis followed by a screen for reduced tolerance to 1,2-naphthoquinone, a compound similar in structure to mansonones. Reduced tolerance to 1,2-naphthoquinone and mansonone E was accompanied by reduced tolerance to another elm phytoalexin, mansonone F. Two mutants exhibited wild-type levels of virulence on three elms, while three other mutants exhibited markedly reduced virulence compared with the wild-type field isolate from which they were derived. When the weakly virulent mutants were crossed with wild-type isolates, progeny that had wild-type levels of virulence but low tolerance to mansonone E were recovered. These results suggest that although O. novo-ulmi is relatively tolerant of mansonone E, this tolerance may not be required for high levels of virulence on elm. Key words: Ophiostoma novo-ulmi, mansonone, phytoalexin, Dutch elm disease.
An ecological study about assemblages of endophytic fungi in Acer macrophyllum in British Columbia: in search of candidate mycoherbicides
Authors: Sieber Thomas N. , Dorworth Charles E.
Published: December 2007

Healthy 2- to 3-year-old twig pieces with adherent foliage were collected from 3- to 10-year-old Acer macrophyllum at seven sites in coastal British Columbia and examined for the presence of endophytic fungi. Eighty-three percent of the leaves and 52% of the twigs were colonized by endophytic fungi. Fungal assemblages of leaves were dominated by Phomopsis spp., whereas Diplodina acerina was most frequently isolated from twigs. Cryptosporiopsis abietina, Glomerella cingulata (with Colletotrichum gloeosporioides anamorph), and Phomopsis spp. also occurred quite frequently in twigs at some sites. No correlations between weather conditions and any of the endophyte species were detected. Diplodina acerina and G. cingulata were the only two species with a certain potential to be employed as mycoherbicides: D. acerina is distributed over most of its hosts' range, and frequency and density of colonization are high among and within trees and some degree of virulence is present; some formae speciales of G. cingulata are already used as mycoherbicides. Key words: endophytic fungi, mycoherbicides, Diplodina acerina, Colletotrichum, fungal ecology.
A reevaluation of the mitotic spindle pole body cycle in Tilletia caries based on freeze-substitution techniques
Authors: O'donnell Kerry
Published: December 2007

Mitosis in the wheat pathogen Tilletia caries (Basidiomycota, Tilletiales) was investigated by electron microscopy of serially sectioned, fast-frozen, freeze-substituted mitotic cells called ballistospores. A duplicated spindle pole body consisting of two identical, three-layered globular elements connected by a middle piece was attached to the extranuclear face of each nucleus at interphase. During mitosis, astral and spindle microtubules radiated from the globular elements that form the poles of an intranuclear spindle. At metaphase, chromosomes were interspersed with the nonkinetochore microtubules, and they were spread along the central two-thirds of the spindle. Each chromatid was attached to a spindle pole by a single, continuous, kinetochore microtubule. Postmitotic replication of the spindle pole body occurred during late telophase to interphase. Results from this study are presented in the form of a model of the mitotic spindle pole body cycle in Tilletia, and this model is compared with the one previously reported for Tilletia and other basidiomycetes. Key words: electron microscopy, freeze substitution, mitosis, spindle pole body, Tilletia.
A heteromorphic life cycle in two coastal coccolithophorids, Hymenomonas lacuna and Hymenomonas coronata (Prymnesiophyceae)
Authors: Fresnel Jacqueline
Published: December 2007

Species of the genus Hymenomonas, with the exception of the freshwater species Hymenomonas roseola, are marine littoral coccolithophorids, characterized by coccoliths of the tremalith type. A heteromorphic life cycle involving an alternation between coccolith-bearing cells and scale-bearing cells has been established for Hymenomonas lacuna in culture. The scaly cells are covered by two types of scales, morphologically distinct from those of the coccolith-bearing stage. Both scale- and coccolith-bearing stages may be motile or nonmotile. The number of chromosomes in coccolith-bearing cells is, however, about twice that in scaly cells as indicated by nuclear staining. Both life-cycle generations were also observed in Hymenomonas coronata, and this type of heteromorphic life cycle could be general for all heterococcolithophorids with tremaliths. Key words: coccolithophorids, Hymenomonas, life cycle, Prymnesiophyceae.
Hypersensitive death, autofluorescence, and ultrastructural changes in cells of leaf sheaths of susceptible and resistant near-isogenic lines of rice (Pi-zt) in relation to penetration and growth of Pyricularia oryzae
Authors: Koga Hlronori
Published: December 2007

Leaf sheaths of susceptible and resistant (Pi-zt) near-isogenic lines of rice were inoculated with Pyricularia oryzae (Magnaporthe grisea) and the host – parasite interactions in living tissues were continuously observed using fluorescence and bright field microscopy. Growth of invading hyphae in the resistant line was restricted within cells that underwent hypersensitive death during fungal penetration. Experiments using heat shock and NaAsO2 treatments suggested that cell death alone is not responsible for restriction of hyphal growth within the penetrated cell. Fungal hyphae grew unimpeded in dead cells of treated tissue unless the dead cells had also developed the capacity to autofluoresce under blue light. Electron microscopic studies showed that hypersensitive cell death occurred specifically in the resistant line after penetration of the cuticle, and in some cases it occurred before cell walls were completely penetrated. In the susceptible line, wall appositions were induced in the epidermal cells at a similar stage of fungal penetration (i.e., before infection hyphae had reached the cell lumen). Inward indentation of the cuticle and cell wall and inward folding of the cuticle at the penetration site suggested that the cuticle was breached mechanically. Wall penetration appeared to be facilitated by enzyme action because the microfibrils of host cell walls around infection pegs were disorganized and nonhomogeneous in electron density. Key words: resistance, penetration, ultrastructure, autofluorescence, rice blast, Pyricularia oryzae (Magnaporthe grisea).
La pléiomérie de la fleur de lilas : déformation accidentelle ou significative?
Authors: Vieth Joachim , Morisset Christiane
Published: December 2007

A morphological and anatomical study was undertaken on pleiomerous flowers that are produced regularly on several shrubs of a collection of lilac cultivars (Syringa vulgaris, S. villosa, S. prestoniae, and S. amurensis). Because of its frequency and regularity, the anomaly appears to be morphologically significant. Our evaluation of accumulated data leads to the conclusion that this pleiomery must be the result of a process of synanthy in the true sense. These floral concrescences are likely an evolutionary expression of a simplification of the inflorescence in the generally very ramified panicles seen in Syringa. Key words: Syringa, lilacs, floral pleiomery, synanthy.
Étude caryologique de trois espèces d’Hypochoeris originaires d'Argentine : H. chillensis, H. microcephala var. albiflora et H. megapotamica
Authors: Siljak-Yakovlev S. , Bartoli A. , Roitman G. , Barghi N. , Mugnier C.
Published: December 2007

Three Hypochoeris species from Argentina with the same chromosome number (x = 4) and similar karyotypes (typically bimodal) show significant ecological and morphological differences. Comparative cytogenetic analysis was done for these taxa, producing karyotypes with correlated idiograms. The number of secondary constrictions and nucleolar organizers varied. The results from this study are discussed in terms of the mechanisms of microevolution within this group of closely related species, and in terms of the evolutionary trend in the genus and in the tribe Cichorieae. Key words: Hypochoeris, Cichorieae, bimodal karyotype, secondary constriction, nucleolar organizer, asymmetry index.
Development of a medium and culture system for in vitro propagation of the seagrass Halophila engelmannii
Authors: Bird K. T. , Jewett-Smith J.
Published: December 2007

An in vitro culture system was developed for axenic culture of the seagrass Halophila engelmannii Aschers. The culture system had a rhizome layer solidified with agar (0.8% w/v) and a liquid overlay layer. The rhizome layer contained artificial seawater (20%0, inorganic nutrients, plant growth regulators, sucrose (1% w/v), and activated charcoal (1% w/v). The overlay layer contained artificial seawater and inorganic nutrients. The medium f/4 provided the best source of inorganic nutrients of the five media compared. Axenic cultures of H. engelmannii died if NO3 was the only N source. They grew best when supplied with glutamic acid at a concentration of 3.4 mM as the N source. A combination of α-naphthaleneacetic acid at a concentration of 0.25 mg ∙ L−1 and 6-benzylaminopurine at a concentration of 10 mg ∙ L−1 provided the most rapid rates of propagation as measured by the numbers of pseudowhorls and branches produced. Key words: tissue culture, marine plants, media, plant growth regulators.
Symptomless infections in alternaria leaf blight of cotton
Authors: Bashan Yoav
Published: December 2007

A symptomless phase of Alternaria macrospora leaf blight that occurs in commercial cultivation of cotton between visible disease outbreaks was studied to determine its cause and effect. Most plants between the two outbreaks of leaf blight epidemics in the field were infected but symptomless; yet during the outbreaks the number of infected symptomless plants was minimal. Drought, high temperature, low humidity, and high salinity increased plant resistance to leaf blight by decreasing visible symptoms and causing symptomless infections. Symptomless plants provided inoculum to infect and produce a visible disease in healthy plants when favorable conditions for disease development resumed. Plant age had minimal influence on symptom-lessness, and sunlight exposure had none. Defoliation was related to the density of spots on leaves and to the virulence of the strain. Polyphenoloxidase activity and phenol accumulation were similar in both disease phases. Plants having visible symptoms produced more spores, but spores from symptomless plants were detached more easily by air currents. Symptom-lessness apparently is a common manifestation of alternaria leaf blight of cotton. It is probably influenced by agroenvironmental parameters that induce the two phases of disease expression. Key words: Alternaria macrospora, cotton leaf blight, leaf spot of cotton, symptomless infections.
Sudden death syndrome of soybean: etiology, symptomatology, and effects of irrigation and Heterodera glycines on incidence and severity under field conditions
Authors: Melgar J. , Roy K. W. , Abney T. S.
Published: December 2007

Soybeans were grown in field microplots in sterile, noninfested soil versus soil infested with either Fusarium solani (form A), Heterodera glycines (the soybean cyst nematode), or both. Symptoms of sudden death syndrome occurred on plants in soil containing F. solani or F. solani plus H. glycines. Signs (macroconidia) sometimes occurred on symptomatic roots. Fusarium solani was reisolated from symptomatic plants but not from asymptomatic ones. Histological data further confirmed F. solani as the causal agent and documented the presence of F. solani chlamydospores in infected roots and cysts. Fusarium solani was not isolated from surface-disinfested seeds of infected plants. Irrigation increased disease incidence and severity. Heterodera glycines was not necessary for infection of plants by F. solani; however, when combined with F. solani, leaf symptoms occurred earlier and were more severe. Inoculation with F. solani plus H. glycines increased the incidence of tip dieback of pods, a disorder of uncertain cause. Fusarium solani was isolated in high frequency from roots of symptomatic plants sampled in the South and Midwest. However, F. solani form B was the most common isolate from roots. A significant positive correlation occurred between incidence of the two F. solani forms in roots of symptomatic plants. Key words: Glycine max, Fusarium solani, Heterodera glycines, etiology.
Growth of Thuja plicata seedlings along a light gradient
Authors: Wang G. G. , Qian H. , Klinka K.
Published: December 2007

To improve understanding of light – growth response relationships in western red cedar, seedlings were grown on three environmentally comparable sites representing nearly optimum growth conditions for the species in coastal British Columbia. On each site, the seedlings were planted on transects extending from a clearcut to the interior of an adjacent old-growth stand. After three growing seasons, seedling mortality, vigour, growth characters, and foliar nutrients were compared across five light classes and between study sites using analysis of variance and related to the percentage of above-canopy light available to each seedling using regression analysis. Three-year mortality was ≤ 27%, and most mortality (≥ 85%) occurred at ≤ 20% of above-canopy light. Seedling growth improved consistently with increasing light; however, the actual growth response at > 40% of above-canopy light varied with study site. The pattern of variation in the growth characters suggested that planted seedlings were able to acclimate morphologically to varying light conditions in three structural traits typically associated with shade adaptation: specific leaf area, height to caliper ratio, and aboveground to root biomass ratio. Specific leaf area and height to caliper ratio decreased and aboveground to root biomass ratio increased with increasing light. This study does not support the contention that under optimal moisture and nutrient conditions carbohydrate deficiency increases the allocation of net biomass production to aboveground structures. We consider western red cedar in the study area to be a. very shade-and exposure-tolerant species but not one that is specifically adapted to an understory environment. Key words: Thuja plicata seedlings, light – growth response relationships, specific leaf area, height to caliper ratio, aboveground to root biomass ratio, shade tolerance.
Patterns and prediction of α and β diversity of aquatic plants in Adirondack (New York) lakes
Authors: Weiher Evan , Boylen Charles W.
Published: December 2007

Patterns in α diversity (species richness) of submersed and floating-leafed aquatic plants were investigated for 45 lakes in the Adirondack region of northern New York State. Multiple linear regressions were used to build predictive models of species richness; the independent variables included lake surface area, approximate littoral zone area, pH, and measures of isolation and connectedness. The regression models that explained the most variance in species richness incorporated pH, a connectedness predictor, and either lake surface area or littoral zone area (r2 = 0.74). The two area measures accounted for a majority of the variance in species richness (about 57%), but neither was a superior predictor to the other. When acidic lakes were systematically removed from the multiple regression model, r2 tended to increase. The coefficient of determination was maximized (at r2 = 0.822) when we limited the data set to lakes with pH > 5.6. As there was no significant correlation between pH and any of the isolation or connectedness measures we used (maximum r = 0.18), acidic lakes are not more isolated than circumneutral lakes. Point β diversity (the heterogeneity of species composition among sites) was measured for each pair of lakes. It was not strongly correlated to either the difference in surface area or the difference in pH between pairs of lakes. Standardized nestedness was calculated following Wright and Reeves (1992, Oecologia 92 : 416 – 428). Adirondack lakes are moderately nested. An implication of this is that species that are found in less diverse lakes have a 44% probability of being found in more diverse lakes. Key words: Adirondacks, aquatic plant, β diversity, biogeography, lake, nestedness, pH, species richness.
Direct absorption of water by hairy leaves of Phlomis fruticosa and its contribution to drought avoidance
Authors: Grammatikopoulos George , Manetas Yiannis
Published: December 2007

Water was sprayed on the adaxial surfaces of hairy and nonhairy leaves to study the possible significance of trichomes in dew or rainwater absorption. Plant species adapted to Mediterranean climate, experiencing periodic water shortage, were used. Water retention was higher and its duration significantly longer on hairy leaves, confirming visual observations in the field. Gravimetric measurements and fluorescence microscopy with the apoplasmic indicator Calcofluor showed that surface water quickly penetrated into the mesophyll of hairy but not nonhairy leaves. The trichome did not participate in the entrance pathway. Direct absorption of water increased the water potential of water-stressed cut leaves, improving their photosynthetic performance through decreased abaxial stomatal resistance. No such effects were found in nonhairy leaves. In a long-term experiment with whole seedlings of the hairy Phlomis fruticosa L., growth rate and photosynthetic pigment content in plants receiving water only through the leaves were intermediate between those of well-watered and water-stressed plants. We conclude that leaf hairs, besides other functions, may also improve leaf water status by entrapping and retaining surface water, thus assisting in its final absorption into the mesophyll. Their contribution to drought avoidance may be critical under some circumstances. Key words: dew, drought, Phlomis fruticosa L., trichome.
Squamanita contortipes, the Rosetta Stone of a mycoparasitic agaric genus
Authors: Redhead S. A. , Ammirati J. F. , Walker G. R. , Norvell L. L. , Puccio M. B.
Published: December 2007

Fungal biodiversity studies on the Olympic peninsula, Washington, have uncovered the key to understanding one of the most enigmatic mushroom genera worldwide. Discovery of a mushroom (Squamanita contortipes) on another grossly distorted but identifiable agaric (Galerina sp.), which retained partial fertility and morphology, provides documentation of parasitism and gall formation by the genus Squamanita. This revelation leads to a reinterpretation of all Squamanitas as commingled hosts and parasites and supplies a simple explanation for anatomical mixtures of tissues erroneously cited as evidence linking the Agaricaceae, Tricholomataceae, and Amanitaceae. It also resolves six decades of controversy over the identity or function of enlarged bases that often bear chlamydospores. Parasitism of mushroom fruit bodies by other mushrooms is a rare phenomenon (< 20 reported species globally). With the addition of accepted Squamanita species, the number of known sporophorous parasitic agarics worldwide is increased by one-third and the number of obligate mycoparasitic mushroom genera is doubled. Key words: biodiversity, gall, taxonomy, biology, terminology, chlamydospores, Pacific Northwest, Asterophora.
Modifications observées dans l'appareil reproducteur du cultivar Fanette de pomme de terre présentant une faible fertilité mâle
Authors: Dobigny A. , Haicour R. , Rossignol L.
Published: December 2007

Flowering has been studied, in greenhouses, in two cultivars of potato (Solanum tuberosum L.) from France, BF15 and Fanette, with a very different flower structure. The former has a regular structure, while the latter presents some variations in the number and structure of floral pieces, especially for the stamens. Stamen feminization, observed for the first time in potato and associated with low pollinic viability, could be related to the poor yield of the cultivar Fanette as a male parent in potato breeding programs. Key words: potato, flowering anomalies, sterility, feminization.
THE OPTIMAL FORM OF DISTRIBUTION NETWORKS APPLIED TO THE KIDNEY AND LUNG
Authors: GUTIERREZ WALTON R.
Published: December 2007

A model is proposed to minimize the total volume of the main distribution networks of fluids in relation to the organ form. The minimization analysis shows that the overall exterior form of distribution networks is a modified ellipsoid, a geometric form that is a good approximation to the external anatomy of the kidney and lung. The variational procedure implementing this minimization is similar to the traditional isoperimetric theorems of geometry.
MODELING OF THE PREVENTION AND CONTROL OF FOREST PEST
Authors: XU WEIJIAN , CHEN SHIDONG , CHEN LANSUN
Published: December 2007

In most models of pest control, the time of prevention and control is always assumed to be unrestricted. In practice, however, it is usually required in agriculture and forestry that we control the pest density to be lower than the economic injury level in a given time. By constructing the dynamics of logistic differential equation with impulsive effect, this paper describes the process of pest control through impulsive spraying pesticide in a given time, and then the existence condition of the solution to the boundary value problem of the dynamics is obtained, with which we solve the problem of pest control on a finite period of time and discuss the governing strategies.
FRACTAL DIMENSION FOR TORTUOUS STREAMTUBES IN POROUS MEDIA
Authors: FENG YONGJIN , YU BOMING
Published: December 2007

An analytical expression for the fractal dimension for tortuous streamtubes in porous media is derived and found to be a function of porosity and microstructures of porous media. There is no empirical constant in the proposed fractal dimension. The present model for the fractal dimension is verified by a comparison with the available analogy model.
Can Experiment Distinguish Tetraquark Scalars, Molecules and \overlineqq Mesons?
Authors: Pennington Michael
Published: December 2007

Scalar mesons are a key expression of the strong coupling regime of QCD. How those with I3 = 0 couple to two photons supplies important information about which is transiently \overlineqq or \overlineqq qq or multi-meson molecule or largely glue, provided (i) we know the location of the corresponding poles in the complex energy plane, and (ii) we have reliable predictions from strong coupling QCD of the radiative widths for these compositions. Number (i) is being supplied by careful analyses of high statistics data particularly that coming from B, D, J/ψ and φ decays. Number (ii) is still required, before we can answer the question in the title.
A Biophysical Consideration on Radiation Mutagenesis
Authors: Kondo Sohei
Published: December 2007

A perspective picture of radiation mutagenesis, the sequence of events which leads from the absorption of radiation to the eventual recovery of mutants, is presented. A model of the mechanism of mutational events in microorganisms modifiable by postirradiation treatments is proposed and applied to the interpretation of the differences in mutation rate at various stages of germ cells of a higher organism, the silkworm.
Indefinite-Metric Quantum Field Theory
Authors: Nakanishi Noboru
Published: December 2007

Some recent progress in the quantum field theory based on the indefinite-metric Hilbert space is reviewed in a systematic way. Various problems (as shown in the table of contents below) are discussed extensively. The selection of topics is, however, dependent on the present author's interest; undescribed topics do not necessarily mean to be unimportant. An almost complete exposition is given concerning the finite-dimensional indefinite-metric space. On the indefinite-metric quantum field theory, the problem of interpretation and the unitarity of the physical S-matrix are discussed in detail. Also included are a number of new results and remarks on various existing theories. Some of them are construction of a field theory having only one Feynman integral, critical remarks on the quantization of a purely-imaginary-mass field and a criticism of the renormalization procedure of the Gupta-Bleuler quantum electrodynamics.
Excitonic Polarization and Polarization Scattering in a Highly Excited Semiconductor
Authors: Otsuka Eizo
Published: December 2007

Interaction between free carriers and excitons in a highly excited semiconductor is considered in terms of the polarization on the part of excitons caused by the electric field due to the free carriers. When the distribution of excitons is uniform, one may have the chance of getting an orderly coupling between carriers and excitons which we call “excitonic polaron”. On the other hand, if the interaction is just a transient one, that can be regarded as the carrier-exciton “collision”. The interaction is treated, as the first approximation, by a simple perturbation approach.
Ciliated protozoans from the Precambrian Doushantuo Formation, Wengan, South China
Authors: Li C.-W. , Chen J.-Y. , Lipps J. H. , Gao F. , Chi H.-M. , Wu H.-J.
Published: December 2007

Ciliates, a major eukaryotic crown-group lineage with thousands of living species, are poorly represented in the fossil record. Ciliate biomarkers are known from the Precambrian, but only one group, the tintinnids, have an extensive fossil record dating back to the Ordovician. Thus, the occurrence of probable ciliate body fossils in Neoproterozoic rocks confirms their earlier appearance, so far inferred only from molecular sequence data and biomarkers. In this paper, we describe those fossils from the 580 million year old Precambrian Doushantuo phosphates, Guizhou, South China. Three new monospecific genera (100 µm to 200 µm in size) are represented by three-dimensional specimens with exceptionally well-preserved cell bodies including cilia, cytostome and tentacles. Two possess loricas and are referred to the tintinnids. The third has numerous tentacles, an apical cytostome and somatic cilia; it is interpreted as an ancestral early suctorian ciliate. These fossils indicate that the origin and evolutionary differentiation and specialization of ciliates took place before or along with the radiation of other crown-group eukaryotes, including metazoans.
A brief review of the fossil record of the Ediacaran–Cambrian transition in the area of Montes de Toledo–Guadalupe, Spain
Authors: Jensen S. , Palacios T. , Martí Mus M.
Published: December 2007

The area of western Montes de Toledo to Guadalupe boasts a thick succession of mainly siliciclastic sediment spanning terminal Ediacaran to lower Cambrian strata as indicated by a relatively sparse but diverse palaeontological record. A terminal Ediacaran age is based on the occurrence of
Cloudina
in platform carbonates of the lower part of the Ibor group and in correlative levels of olistostromes at the base of the Río Huso group. Higher in the Río Huso group are found trace fossils which indicate a Cambrian age, notably
Treptichnus bifurcus
, which overlaps the local stratigraphic range of macroscopic carbonaceous disc-shaped fossils identified as
Beltanelliformis
. Strata underlying the Río Huso group contain treptichnids. The fossil record of the terminal Ediacaran–Lower Cambrian of this area is in part comparable to
Cloudina
-bearing sediments from other regions, in particular Namibia, where treptichnid trace fossils also overlap the range of
Cloudina
. The possibility of a wider biostratigraphic significance of this should be further tested, including its relation to the base of the Cambrian.
Discoidal fossils of the Ediacaran biota: a review of current understanding
Authors: MacGabhann B. A.
Published: December 2007

Discoidal fossils, despite being the oldest, youngest, and most common elements of the Ediacaran biota, have not received their fair share of attention. Taxonomy of discoidal fossils is currently dubious, and some forms have not been properly re-examined since the initial incorrect descriptions as medusae. Attachment discs of benthic stalked forms, which adhere to microbial mats at the sediment–water interface, are unequivocally present without stalks or other upper parts in most discoidal Ediacaran assemblages. However, many discoidal assemblages are likely to have represented a heterogeneous mixture of benthic discoidal organisms, including bacterial colonies, fungi, actinian-grade cnidarians, and perhaps poriferans. Such organisms probably account for the vast majority of fossils in the Fermeuse Formation of Newfoundland and similar assemblages from Norway, England, and Wales. Discs in the underlying complex Mistaken Point assemblages, however, likely mostly represent holdfasts. Other complex assemblages, such as those of South Australia and the White Sea of Russia, unequivocally contain more than one biological construction responsible for the discoidal structures, but holdfasts likely represent a significant proportion. The disc-dominated Fermeuse assemblages and the nearby rangeomorph-dominated Mistaken Point assemblages are unlikely to merely represent different taphonomic windows on identical communities, as previously suggested, but rather reflect environmental control on both biotic composition and taphonomy.
Biota in the terminal Proterozoic successions on the Indian subcontinent: a review
Authors: Maithy P. K. , Kumar G.
Published: December 2007

On the Indian subcontinent, Late Proterozoic rocks form part of a continuous sequence grading into Cambrian, postdating the Sturtian glaciation (Cryogenian) and terminated by the Xingkaian/Pan African Orogeny (Late Cambrian). These sequences are restricted to the northwestern part of the Indian Shield, are overlain by Cenozoic sediments of the Indo-Gangetic Plain, and rest unconformably on the oldest platform sequences (Meso—Cryogenian) in many parts of the Lesser and Tethys/Higher Himalaya. Of these, the succession in the Krol Belt, Lesser Himalaya, divided into Baliana, Krol and Tal Groups, is fossiliferous. Changes in faunal composition of acritarchs and cyanobacteria are recorded in the upper part of the Baliana Group, as is the appearance and extinction of forms assigned to the Ediacara fauna in the overlying Krol. Such biotic change is accompanied by a significant depletion in δ13C values in the ‘cap carbonates’. Another δ13C depletion is recorded in the upper part of the Krol Group along with appearance of spiny acanthomorphic acritarchs, scaphomorphs and hercomorphs, small shelly fossils, a variety of Early Cambrian trace fossils and trilobites in the overlying Tal Group. A review of biota reported from the oldest platform sediments (Vindhyan Supergroup, Karnool, Bhima Groups) suggests a Meso-Cryogenian (pre-Sturtian glaciation) age.
Siliceous microfossils and biosiliceous sedimentation in the lowermost Cambrian of China
Authors: Braun A. , Chen J.-Y. , Waloszek D. , Maas A.
Published: December 2007

Clay-rich and siliceous sedimentary rocks of earliest Cambrian age on the Yangtze Platform, China, contain abundant siliceous microfossils. The black cherts and black shales in this sequence, of earliest Cambrian age, contain sponge spicules (both macroscleres and microscleres), derived from lithistid demosponges and hexactinellids. These spicule associations are useful for biostratigraphic correlation, and indicate that Porifera played an important role in the geochemical cycling of silica at the beginning of the Phanerozoic. Phosphatic microfossils also contributed to the deep-sea ecology of this region during the earliest Cambrian.
Groundwater Age and Groundwater Age Dating
Authors: Bethke Craig M. , Johnson Thomas M.
Published: December 2007

A new way of thinking about groundwater age is changing the field of groundwater age dating. Following a rigorous definition of age, a groundwater sample is seen not as water that recharged the flow regime at a point in the past, but as a mixture of waters that have resided in the subsurface for varying lengths of time. This recognition resolves longstanding inconsistencies encountered in age dating and suggests new ways to carry out age dating studies. Tomorrow's studies will likely employ sets of marker isotopes and molecules spanning a broad spectrum of age and incorporate a wide range of chemical and physical data collected from differing stratigraphic levels. The observations will be inverted using reactive transport modeling, allowing flow to be characterized not in one direction along a single aquifer, but in two or three dimensions over an entire flow regime.
Ischemic defects in the electron transport chain increase the production of reactive oxygen species from isolated rat heart mitochondria
Authors: Chen Qun , Moghaddas Shadi , Hoppel Charles L. , Lesnefsky Edward J.
Published: December 2007

Cardiac ischemia decreases complex III activity, cytochrome c content, and respiration through cytochrome oxidase in subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM). The reversible blockade of electron transport with amobarbital during ischemia protects mitochondrial respiration and decreases myocardial injury during reperfusion. These findings support that mitochondrial damage occurs during ischemia and contributes to myocardial injury during reperfusion. The current study addressed whether ischemic damage to the electron transport chain (ETC) increased the net production of reactive oxygen species (ROS) from mitochondria. SSM and IFM were isolated from 6-mo-old Fisher 344 rat hearts following 25 min global ischemia or following 40 min of perfusion alone as controls. H2O2 release from SSM and IFM was measured using the amplex red assay. With glutamate as a complex I substrate, the net production of H2O2 was increased by 178 ± 14% and 179 ± 17% in SSM and IFM ( n = 9), respectively, following ischemia compared with controls ( n = 8). With succinate as substrate in the presence of rotenone, H2O2 increased by 272 ± 22% and 171 ± 21% in SSM and IFM, respectively, after ischemia. Inhibitors of electron transport were used to assess maximal ROS production. Inhibition of complex I with rotenone increased H2O2 production by 179 ± 24% and 155 ± 14% in SSM and IFM, respectively, following ischemia. Ischemia also increased the antimycin A-stimulated production of H2O2 from complex III. Thus ischemic damage to the ETC increased both the capacity and the net production of H2O2 from complex I and complex III and sets the stage for an increase in ROS production during reperfusion as a mechanism of cardiac injury.
Inhibition of shortening velocity of skinned skeletal muscle fibers in conditions that mimic fatigue
Authors: Karatzaferi Christina , Franks-Skiba Kathleen , Cooke Roger
Published: December 2007

The mechanisms responsible for the inhibition of shortening velocity that occurs during muscle fatigue have not been completely elucidated. Phosphorylation of the myosin regulatory light chain (RLC) occurs during heavy use; however, previous reports on its role in affecting velocity have been equivocal. To further understand the process of fatigue, we varied the levels of myosin RLC phosphorylation (from 10 to >50%) and the concentrations of protons (from pH 7 to 6.2) and phosphate (from 5 to 30 mM), all of which change during fatigue. We measured the mechanics of permeable rabbit psoas fibers at a temperature closer to physiological (30°C), using a temperature jump protocol to briefly activate the fibers at the higher temperature to preserve sarcomere homogeneity. Although lowered pH alone had an effect on velocity, it was the three factors together, i.e., high phosphorylation, low pH, and high phosphate, that acted synergistically to inhibit fiber velocity by ∼40%. Our data demonstrate that in conditions that simulate physiological muscle fatigue, myosin phosphorylation does contribute to the inhibition of contraction velocity of fully activated fast muscle fibers.