bluuebunny/crossref_metadata_2025 huggingface dataset:
The paradox of berry production in temperate species of Vaccinium
Authors: Kloet S. P. Vander , Hill N. M.
Published: December 2007

Vegetative cover, fruiting phenology, and seed production was estimated from six Vaccinia heathlands on the Avalon Peninsula of Newfoundland so that the efficacy of the Vaccinium seed bank could be ascertained. Out of the six species of Vaccinium present in this vegetation, only V. angustifolium and V. boreale were recovered from 120 soil cores taken; V. uliginosum and V. vitis-idaea, two of the most common species on these heaths, were not represented in the seed bank at all, yet experimentally buried seeds from both these taxa will successfully germinate when exhumed after 6 years of burial. Indeed, 81% of the germinants were from taxa with dry fruits such as Kalmia, Luzula, Juncus, and Agrostis. Paucity of Vaccinium seed in the soil column may be due in part to fungal rot and avian predation. Key words: Vaccinium, seed production, seed banks, heaths.
Arnaudiella eucalyptorum sp.nov. (Dothideales, Ascomycetes), and its hyphomycetous anamorph Xenogliocladiopsis gen.nov., from Eucalyptus leaf litter in South Africa
Authors: Crous P. W. , Kendrick W. B.
Published: December 2007

Arnaudiella eucalyptorum is described as a new saprobic Ascomycete from Eucalyptus leaf litter. Its anamorph, which developed in pure culture, is placed in a new hyphomycetous genus, Xenogliocladiopsis. Xenogliocladiopsis eucalyptorum sp.nov. is known from collections of Eucalyptus leaf litter in the Transvaal and Cape provinces of South Africa, where it appears to be specific to this substrate. Key words: Arnaudiella eucalyptorum, Ascomycetes, Dothideales, Eucalyptus leaves, hyphomycetes, Xenogliocladiopsis eucalyptorum.
Occurrence and phylogenetic significance of monoplastidic meiosis in liverworts
Authors: Renzaglia Karen Sue , Brown Roy C. , Lemmon Betty E. , Duckett Jeffrey G. , Ligrone Roberto
Published: December 2007

Monoplastidic meiosis is reported for the first time in three seemingly unrelated liverworts, namely Blasia pusilla (Metzgeriales), Monoclea gottschei (Monocleales), and Haplomitrium blumei (Haplomitriales). A second species of Haplomitrium, H. hookeri, is polyplastidic as previously reported. All three taxa represent isolated relicts of ancient liverwort lineages. Monoplastidy in these hepatics is evident in archesporial tissue and is maintained through successive sporogenous cell generations. In archesporial mitosis, the single plastid divides and the two resultant plastids are precisely positioned so that one is inherited by each daughter cell. In the nascent spore mother cell, the solitary plastid undergoes two successive divisions and the resulting four plastids become positioned in a tetrahedral arrangement. Concomitantly, the sporocyte assumes a quadrilobed shape, which is less exaggerated in Monoclea, and a single large plastid is situated in each lobe. Details of plastid ultrastructure and morphology vary slightly among the three taxa. Evidence is presented that Blasia and Monoclea share a common ancestry and represent pivotal taxa in the evolution of the two main lines of liverworts. Haplomitrium is suggested to occupy a more basal position in bryophyte phylogeny. Monoplastidy in meiosis of liverworts links the charophytes, the three bryophyte clades, and the lycopsid pteridophytes and supports a monophyletic interpretation of land plant phylogeny. Key words: chloroplast, liverwort, meiosis, monoplastidy, phylogeny, sporogenesis.
Alteration of element contents in guard cells of Norway spruce (Picea abies) subjected to ozone fumigation and (or) water stress: X-ray microanalysis study
Authors: Thiec D. Le , Rose C. , Garrec J. P. , Laffray D. , Louguet P. , Galaup S. , Loosveldt P.
Published: December 2007

Two clones of Norway spruce Picea abies (L.) Karst. (Gerardmer clone and Istebna clone) were subjected to an ozone-enriched atmosphere. The X-ray microanalysis of elements present in the guard cells showed a decrease in potassium for the Gerardmer clone along with a larger closing of guard cells and an increase in calcium contents; for the Istebna clone, ozone did not affect these contents. When a drought stress was applied, an increase in calcium content of guard cells of the Istebna clone was also found. However, the potassium content was smaller in this case for the two clones and could well be due to stomatal closure. When ozone and drought stress were applied together, the potassium content in the Istebna clone was not affected, but for the Gerardmer clone, ozone reduced the decrease in potassium content that occurred as drought stress developed. However, calcium (and manganese) content increased significantly when the Gerardmer clone was exposed to ozone. It seems likely that the Gerardmer clone is sensitive to ozone and when subjected to a drought stress this sensitivity is increased. For the Istebna clone, the resistance to ozone is unaffected by the drought stress treatment. The Istebna clone, however, seems sensitive to drought. These characteristic responses in the two different Norway spruce clones are probably due to genetic differences and may explain the contradictory observations in the response of the stomata during the simultaneous implementation of the complex stresses. Key words: Picea abies, guard cells, ozone, drought stress, X-ray microanalysis, elements.
Generation and utilization of chemical-resistant mutants in Pyrenophora tritici-repentis, the causal agent of tan spot of wheat
Authors: McCallum B. D. , Bernier C. C. , Lamari L.
Published: December 2007

Tan spot, caused by the fungal pathogen Pyrenophora tritici-repentis, is a major leaf spot disease of wheat worldwide. To facilitate genetic analysis of this homothallic fungus, mutants resistant to the fungicide iprodione or hygromycin B were created through ultraviolet light mutagenesis and used in sexual crosses. Conidia from two isolates of P. tritici-repentis, sensitive to both chemicals (iprodione-S hygromycin-S), were exposed to ultraviolet light to obtain four mutants resistant to iprodione but sensitive to hygromycin B (iprodione-R hygromycin-S) and three mutants resistant to hygromycin B but sensitive to iprodione (iprodione-S hygromycin-R). The mutants were paired in all combinations, and the markers allowed crossed progeny to be distinguished from selfed progeny. Crossed ascospore progeny from pairings between iprodione-R hygromycin-S isolates and iprodione-S hygromycin-R isolates and between iprodione-R hygromycin-R isolates and iprodione-S hygromycin-S segregated 1:1 for resistance–sensitivity to both iprodione and hygromycin B. These results indicate that one locus controls iprodione resistance and a second independent locus controls hygromycin B resistance. This study should facilitate further genetic research on the tan spot fungus by providing a simple marker system. Key words: genetics, inheritance, Drechslera, yellow spot, leaf spot.
Effect of propagule source on competitive ability of pasture grasses: spatial dynamics of six grasses in simulated swards
Authors: Turkington Roy
Published: December 2007

Simulated swards were constructed to investigate the potential effect of propagule source on competitive ability of pasture grasses, to monitor the spatial dynamics of pasture communities, and to assess the importance of species interactions and disturbances in community structure. The design used six species of grasses, Agrostis alba, Dactylis glomerata, Holcus lanatus, Lolium perenne, Phleum pratense, and Poa compressa, arranged in a mosaic of hexagonal patches with each hexagon being sown with one species of grass or left as bare ground and being surrounded by each of the other species. Three swards were constructed, one using plant material collected from an 11-year-old pasture, one with material from an adjacent 49-year-old pasture, and the third from material grown from seed. After 20 months of interaction across the interfaces between the patches, the swards were destructively harvested above ground and the contents of each hexagon separated into species. Grasses from four different-aged origins, including the three above, were also grown in plots without any neighbours for 16 months. Each species had its own individual behavior: Agrostis and Phleum from the older pastures were the better invaders, Holcus and Poa were the poorest, and Phleum from the oldest community was the most resistant to lateral expansion of the other species. In a number of cases the grasses from the older pastures, but never from the seeded bed, invaded other patches of grass as readily as they expanded into bare ground. The total aboveground community biomass showed a nonsignificant decline with age, and the community as a whole became more open to lateral expansion by individual species. No results were obtained to support the cyclic regeneration hypothesis of Watt; the functional equivalence arguments of Aarssen may be more appropriate in this fine-grained pasture environment. Key words: community dynamics, invasion, pasture, competitive effect and response, disturbance, patches.
Ontogenetic comparisons of arbuscular mycorrhizal fungi Scutellospora heterogama and Scutellospora pellucida: revision of taxonomic character concepts, species descriptions, and phylogenetic hypotheses
Authors: Franke Marlise , Morton Joseph
Published: December 2007

The taxonomic significance of morphological characters in fungi of Glomales (Zygomycetes) has been based solely on superficial resemblance. Ontogenetic comparisons among isolates of Scutellospora pellucida and Scutellospora heterogama were used to resolve discrete stages of differentiation in which characters were delimited and ordered hierarchically according to temporal and spatial origin in development. Character concepts were revised, and both species were redescribed. A spore wall, two inner walls, and a germination shield were designated primary characters because they appeared separately and in linear succession. Secondary characters included distinct layers differentiated within each wall. Tertiary characters were qualitative and quantitative properties of each layer. All characters in each developmental stage did not vary in two hosts, in separate experiments, and among five isolates of each species. Stability was attributed to causal epigenetic linkages between stages of differentiation, wherein each new stage depended on differentiation of all characters in the preceding stage. Characters at successively lower hierarchical levels are predicted to specify progressively less inclusive taxa in cladistic analysis. Developmental patterns will improve reinterpretations of phylogenetic relationships and provide a more empirical basis for grouping and ranking of organisms into species and higher taxa at the morphological level. Key words: evolution, morphology, mycorrhizae, taxonomy, VAM fungi.
High temperature, darkness, and drought predispose black spruce seedlings to gray mold
Authors: Zhang P. G. , Sutton J. C.
Published: December 2007

Gray mold caused by Botrytis cinerea Pers.:Fr. developed in seedlings of black spruce (Picea mariana BSP) that were subjected to high temperatures (30–45 °C) in darkness or to drought conditions immediately before inoculation with the pathogen (106 conidia/mL). Incidence and density of spore production of B. cinerea in needles of the treated seedlings increased, and chlorophyll content decreased, with duration of the preinoculation treatments. Gray mold did not develop in seedlings subjected to preinoculation high temperature in the light, and also failed to develop in seedlings that were kept at 1–20 °C in light or darkness with adequate water, inoculated with 103–107 conidia of B. cinerea/mL, then subjected to a range of postinoculation humid periods (0–48 h) at various constant temperatures (12, 20, and 28 °C) in light or darkness. Regression models were developed to describe the incidence and density of sporulation of B. cinerea and chlorophyll content in seedling needles as functions of the level and period of preinoculation high temperature plus darkness, preinoculation drought period, and seedling age (R2 = 0.45–0.95; p ≤ 0.01). It was concluded that high temperature in combination with darkness, and drought stress, predisposed the seedlings to gray mold. Key words: Picea mariana, Botrytis cinerea, predisposition, disease models.
Cyanide-resistant, alternative pathway respiration in guard cell protoplasts of Vicia faba
Authors: Mawson B. T.
Published: December 2007

The activity and capacity of cyanide-resistant or alternative pathway respiration was examined in Vicia faba L. guard and mesophyll cell protoplasts maintained either in darkness (dark adapted) or illuminated with blue light. Respiration rates by dark-adapted guard cell protoplasts were unaffected by titrating with salicylhydroxamic acid (0.1–2.0 mM), an inhibitor of alternative pathway respiration, suggesting the lack of activity of this pathway. In combination with 0.1 mM KCN, an inhibitor of cytochrome pathway respiration, salicylhydroxamic acid was effective in inhibiting total respiration rates. In contrast with guard cell protoplasts, salicylhydroxamic acid reduced rates of O2 consumption in dark-adapted mesophyll cell protoplasts by 25–30% of total respiration. Titrating the cytochrome pathway of guard cell protoplasts with KCN (10–140 μM) alone failed to reduce respiratory activity but was effective in combination with salicylhydroxamic acid. Addition of a proton ionophore, carbonyl cyanide m-chlorophenylhydraxone, to dark-adapted guard cell protoplast suspensions increased respiration by approximately 30 and 84% in the presence and absence of salicylhydroxamic acid, suggesting restriction of electron flow by adenylates. Illumination of guard cell protoplasts with blue light for 30 min increased the sensitivity of respiration to salicylhydroxamic acid and increased the activity of the alternative pathway over this time period to ~55% of total respiration. Blue light also increased the rate of uncoupled respiration by guard cell protoplasts treated with salicylhydroxamic acid compared with dark-adapted protoplasts. The results suggest that electron movement through either cytochrome or alternative pathways in guard cell mitochondria may be regulated during signal transduction of blue light. Key words: Vicia faba, guard cell protoplasts, alternative pathway, respiration, blue light.
Extrafloral nectaries in the tropical tree Guarea macrophylla (Meliaceae)
Authors: Morellato L. P. C. , Oliveira P. S.
Published: December 2007

This paper describes the anatomy and morphology of the complex nectary systems of the tropical tree Guarea macrophylla Vahl (Meliaceae) and presents the first record of extrafloral nectaries occurring on reproductive organs (fruits) of a member of the order Sapindales. The extrafloral nectaries of G. macrophylla occur on petioles, petiolules, the abaxial surface of all leaflets, leaf buds, and over the surface of fruits. All extrafloral nectaries are distinctly raised above the surface. Foraging ants collect extrafloral nectar on Guarea trees both day and night. We suggest that the presence of extrafloral nectaries might be a useful taxonomic character for the identification of Guarea species. Key words: Guarea, Meliaceae, extrafloral nectaries, ants.
Mycotoxin production and pathogenicity of Fusarium species and wheat resistance to Fusarium head blight
Authors: Atanassov Zhivko , Nakamura Chiharu , Mori Naoki , Kaneda Chukichi , Kato Hajime , Jin Yin-Zhe , Yoshizawa Takumi , Murai Koji
Published: December 2007

In vitro production of trichothecene mycotoxins, deoxynivalenol, nivalenol, T-2 toxins, and their derivatives was studied in rice culture using 30 strains from seven Fusarium species. Six strains of three Fusarium species were selected for the evaluation of mycotoxin production and pathogenicity after artificial inoculation to seven wheat lines with different levels of resistance or susceptibility and their eight F1's. Three criteria were used for the evaluation: the reduction of seed set, the reduction of grain weight, and the concentration of mycotoxins in infected grain. Significant variability was observed among Fusarium strains, wheat genotypes, and in the interaction between them. The contribution of Fusarium strains, however, was far greater than that of the other two factors. The kinds and relative amounts of mycotoxins produced in rice culture were consistent with those present in infected grain with some exceptions. Significant correlations were found between the grain weight reduction and the mycotoxin concentration and between the level of resistance of the wheat genotypes under the artificial and natural conditions of infection. The biological role of Fusarium mycotoxins in pathogenicity and wheat resistance to Fusarium head blight is discussed. Key words: Fusarium head blight (scab), Fusarium mycotoxins, Fusarium pathogenicity, wheat resistance to Fusarium head blight.
Inhibition of oxygen evolution by ivalin
Authors: Bernal-Morales Ernesto , Vivar Alfonso Romo De , Sanchez Bertha , Aguilar Martha , Lotina-Hennsen Blas
Published: December 2007

The inhibition of ATP synthesis, proton uptake, and electron transport (basal, phosphorylating, and uncoupled) from water to methylviologen by ivalin (a naturally occurring sesquiterpene lactone in Zaluzania triloba and Iva microcephala) indicates that it acts as electron transport inhibitor. Since photosystem I and electron transport from DPC to QA were not affected, while the electron flow of uncoupled photosystem II from H2O to DAD and from water to silicomolybdate was inhibited, we concluded that the site of inhibition of ivalin is located at the oxygen evolution level. Key words: oxygen evolution, ivalin, photosynthesis, sesquiterpene lactone.
Nitrate uptake in maritime pine (Pinus pinaster) and the ectomycorrhizal fungus Hebeloma cylindrosporum: effect of ectomycorrhizal symbiosis
Authors: Plassard C. , Barry D. , Eltrop L. , Mousain D.
Published: December 2007

Nitrate uptake rates were determined for nonmycorrhizal and mycorrhizal maritime pine (Pinus pinaster) associated with the ectomycorrhizal basidiomycete Hebeloma cylindrosporum and for this fungal species grown in vitro. Different [NO3−] (0–1.3 and 10 mM) were supplied to nonmycorrhizal or mycorrhizal P. pinaster plants grown axenically in test tubes for 21 weeks. Uptake of NO3− by the plants was determined by measuring NO3− depletion from the medium that was added to the culture tubes without root pertubation. For all applied [NO3−] the uptake rates for NO3− in mycorrhizal plants were increased about twofold compared with nonmycorrhizal plants. The same range of [NO3−] was supplied to the fungus in pure culture, and uptake rates were calculated either from the measurement of NO3− depletion from the medium or by 15N accumulation in the mycelium. For the same external nitrate concentrations the results obtained with these two methods were not significantly different. The amount of fungal biomass in mycorrhizal root systems was determined with the chitin assay. The contribution of each partner to nitrate uptake in the mycorrhizal plant was calculated from the kinetic parameters of nitrate uptake by the fungus and host plant alone given by the Lineweaver–Burk plots. For external [NO3−] higher than 0.1 mM the measured uptake rates for NO3− in mycorrhizal plants were greater than the calculated sum of the individual symbiotic partners. The significance of this excess nitrate uptake is discussed in relation to the role of ectomycorrhizae in nitrogen accumulation. Key words: NO3− uptake rates, Km, Vmax, ectomycorrhizal symbiosis, Hebeloma cylindrosporum, Pinus pinaster.
Production of tumours and roots by Ephedra following Agrobacterium rhizogenes infection
Authors: O'Dowd Niamh A. , Richardson David H. S.
Published: December 2007

This paper contains the first report that stems of the Gnetophyte Ephedra respond to infection by Agrobacterium rhizogenes by producing roots and tumours in vivo and in vitro. Of the bacterial strains employed, the wild-type Ar2629 gave the maximum response, and strain LBA9402 was also effective. In no case did heat-treated A. rhizogenes produce tumours or roots. Excised tumour tissues were cultured for more than 2 years in the absence of exogenous plant-growth regulators without any deterioration in growth rate. In vivo tumours of Ephedra fragilis and Ephedra minima contained up to 0.3% dry weight l-ephedrine, and slow-growing in vitro cultured tumours of E. fragilis contained up to 0.01% l-ephedrine, but alkaloid was not detected in faster growing isolates. Key words: Agrobacterium rhizogenes, alkaloid, Ephedra, l-ephedrine, Gnetophytes, gymnosperm, tumours.
Siliceous microfossils in a Holocene, High Arctic peat deposit (Nordvestø, northwestern Greenland)
Authors: Brown Kimberley M. , Douglas Marianne S. V. , Smol John P.
Published: December 2007

Siliceous microfossils (diatom valves, chrysophyte stomatocysts, and testate amoebae plates) were examined from a 2.6-m thick peat deposit from Nordvestø, northwestern Greenland (76°44′N, 73° 13′W). The moss, predominantly Aplodon wormskioldii (Hornem.) R.Br., began to accumulate approximately 6500 years ago and persisted for about 2000 years. Siliceous microfossils were generally well preserved in the peat, although taxon richness was low (i.e., only 19 diatom taxa, 16 chrysophyte cyst morphotypes, and 4 testate amoebae genera). Despite the paucity of taxa, marked shifts in species composition were recorded. Geochemical analyses and biogenic silica determination on the peat did not show any significant trends. To our knowledge, this study represents the first such combined analysis of a High Arctic peat, so our interpretations should be considered tentative. Environmental variables were not stable during the 2000 years of peat accumulation, as suggested by microfossil assemblage changes. For example, about 5000 years BP, diatoms reached their maximum relative abundance with taxa indicative of wetter habitats. We hypothesize that an influx of meltwater to the peat may have occurred at this time, perhaps because of wetter conditions or larger accumulations of snow during winter. These preliminary data indicate that siliceous microfossil analyses from arctic peat cores may eventually fine-tune paleoecological inferences for this climatically important region, once the environmental variables determining species distributions in peat deposits are determined. Key words: peat deposits, Greenland, diatoms, chrysophyte cysts, protozoan plates, paleoecology.
Three new Leptographium species associated with conifer roots in the United States
Authors: Wingfield Michael J. , Harrington Thomas C. , Crous Pedro W.
Published: December 2007

Leptographium species are most commonly known as anamorphs of Ophiostoma and are usually associated with insects that infest trees. Three new species of Leptographium were isolated from conifer roots in various parts of the United States. These three species differ from described species both morphologically and on the basis of their allozyme banding patterns. Leptographium albopini occurs both in the eastern and western United States on white pine hosts, while Leptographium douglasii occurs commonly in the western United Sates and has been found only on Pseudotsuga menziesii. Leptrographium neomexicanus occurs in the southwestern United States and has thus far only been collected from Pinus ponderosa. Key words : Leptographium albopini, Leptographium douglasii, Leptographium neomexicanus, Pinus, Pseudotsuga, systematics, root infesting insects.
Pollen load, capsule weight, and seed production in three orchid species
Authors: Proctor H. C. , Harder L. D.
Published: December 2007

Relationships between pollen load, seed production, and capsule weight in orchids are important both theoretically and pragmatically. It has been hypothesized that pollen packets (pollinia) evolved in orchids because of selection to produce packages capable of fertilizing all ovules in an ovary; testing this hypothesis requires information about the relationship between pollen load and seed production. As well, because capsules contain thousands to millions of seeds, an easily measured correlate of seed number, such as capsule weight, would be valuable for studies of reproductive success. We hand-pollinated Cypripedium calceolus, Amerorchis rotundifolia, and Calypso bulbosa with different pollen loads, weighed capsules, and estimated seed number by subsampling from liquid suspension. Pollen load affected seed number in Calypso but had no significant effect in Cypripedium or Amerorchis. Capsule weight was positively associated with seed number in all species, but there was considerable variation in R2 across species (from 0.40 to 0.85), indicating that it is unwise to assume that capsule weight is a good measure of relative reproductive success. As well, our data suggest that size of the typical unit of pollen deposition rather than that of the entire pollinarium evolved to match ovule number in orchids. Key words: Orchidaceae, pollen load, capsule weight, seed set.
Period of harvest, sprouting ability of cuttings, and in vitro plant regeneration in Fraxinus excelsior
Authors: Silveira Conceição Eneida , Cottignies Alain
Published: December 2007

Propagation by stem cuttings and in vitro culture of apical bud explants were studied on Fraxinus excelsior L. Stem cuttings from 4- to 7-year-old trees growing under natural conditions sprouted only when cuttings were taken from dormant material. Only 6% of those that had sprouted developed roots by the 7th month of culture. Similarly, only apical bud explants harvested during the dormant period sprouted in vitro. Up to 87% of these sprouts developed two to four branching adventitious roots after 5 months of culture. During the initial phase of in vitro culture, the Quoirin and Lepoivre medium and the woody plant medium favoured sprout lengthening. During the phase of multiplication, up to three sprouts per explant developed with the woody plant medium in the presence of a combination of high 6-benzylaminopurine (3.0–4.0 mg∙L−1) and low indole-3-butyric acid (0.01–0.03 mg∙L−1) concentrations. Rooting was obtained in a medium without any growth regulators. Microscopic analysis showed a direct connection between the vascular elements of adventitious roots and stem of plantlet. Chromosome number in root apices of ash plantlets and ash trees grown under natural conditions was 2n = 46. Key words: chromosome number, Fraxinus excelsior L., in vitro plants, micropropagation, stem cuttings.
Spatial and temporal variation in pollen tube numbers in Lindera benzoin (spicebush)
Authors: Niesenbaum Richard A.
Published: December 2007

The numbers of pollen tubes per stigma and style were examined in naturally pollinated plants in two populations of the dioecious shrub Lindera benzoin to reveal variation between populations, among plants within populations, among flowers within plants, and among early and late blooming flowers. Most of the variation in pollen tube numbers is within individual plants. Differences between populations are likely due to observed differences in pollinator activity. Flowers that opened later in the flowering season were more likely to be pollinated and had larger numbers of pollen tubes per stigma than those that opened earlier. The level of variation observed among stigmas diminished as pollen tubes entered the style indicating that pollen–stigma interactions may be important in the fertilization process. Even under conditions of low pollen deposition and pollinator activity, pollen tube competition may still occur. Key words: Lindera benzoin, pollen tube, pollen–stigma interactions.
Morphology and relationships of Mesocyparis umbonata sp.nov.: fossil Cupressaceae from the Late Cretaceous of Alberta, Canada
Authors: McIver E. E. , Aulenback K. R.
Published: December 2007

Late Cretaceous silicified Cupressaceae remains, recently recovered from the Horseshoe Canyon Formation of Alberta, Canada, include three-dimensional leafy twigs of the Cupressinocladus interruptus type with attached seed cones, seeds, pollen cones, pollen, and woody stems. The abundance and excellent preservation of the remains allows detailed description of most aspects of the plant, including foliage, reproductive organs, epidermal features, and wood. Foliage of the fossil is frondlike and flattened, with an opposite, less commonly alternate, branching pattern. Seed cones, borne in decussate pairs, are globose, woody, about 4.0 mm in diameter, and bear four approximately equal-sized cone scales with small umbos near the scale center. Each seed has two broad, semicircular wings. Pollen cones are typical for the Cupressaceae; pollen grains are structurally comparable, but small, for the family. Fertile branches and seed cones are not identical to any extant member of the Cupressaceae, but they are sufficiently similar to those of the Paleocene cedar Mesocyparis borealis from Western Canada to be referred to that genus. Dissimilarities justify assignment to Mesocyparis umbonata sp.nov. Seed cone structure of Mesocyparis umbonata resembles most closely that of the northern hemispheric taxon Chamaecyparis nootkatensis; the leaves resemble those of Thuja and Chamaecyparis. Other features, including the number of seed cone scales, branching pattern, and wood anatomy, are more comparable to those of taxa of the southern hemispheric Libocedreae. New information, based on these remains, indicates that the relationship between some northern and southern hemispheric taxa is closer than previously proposed, supporting the premise that present systems of classification separating these taxa do not reflect phylogeny. Key words: Cupressaceae, Mesocyparis, Late Cretaceous, fossil, seed cones, evolution, phylogeny.
Sporophytes, megaspores, and massulae of Azolla stanleyi from the Paleocene Joffre Bridge locality, Alberta
Authors: Hoffman Georgia L. , Stockey Ruth A.
Published: December 2007

Several hundred vegetative and fertile specimens of Azolla Lam. have been recovered from the Paleocene Paskapoo Formation at the Joffre Bridge locality (Middle Tiffanian (Ti3) age) near Red Deer, Alberta. The spore complexes closely resemble those of the Paleocene A. stanleyi Jain & Hall, and the vegetative material is referred to that species. The specimens are unusually complete in that the remains of the fragile sporophyte are preserved, commonly with reproductive structures in place. Plants reaching up to 2.25 cm in length consist of alternately branched rhizomes bearing alternate, imbricate, sessile leaves. Leaves are ovate with entire margins, papillate surfaces, and a single midvein. Reproductive structures have been examined using light, scanning, and transmission electron microscopy. This new material is compared with the other Paleocene species for which sporophytes are known and discussed in terms of evolutionary trends for the genus. The specimens suggest that most of the vegetative characteristics of modern Azolla species were established by the middle Paleocene. Key words: Azolla, Salviniaceae, megaspore, massula, ultrastructure, Paleocene.
Seasonal patterns and environmental regulation of frost hardiness in shoots of seedlings of Thuja plicata, Chamaecyparis nootkatensis, and Picea glauca
Authors: Silim Salim N. , Lavender Denis P.
Published: December 2007

Seasonal patterns of frost hardiness and the effects of photoperiod, water stress, and low temperature on hardiness development were examined in shoots of 1st-year seedlings of western red cedar (Thuja plicata Donn), yellow cedar (Chamaecyparis nootkatensis (D. Don) Spach), and white spruce (Picea glauca (Moench) Voss). Under natural conditions, spruce hardened in two stages starting in early August, first at a slow rate in response to shortening photoperiod, then at a faster rate in response to decreasing temperatures. Western red cedar and yellow cedar started hardening in late October to early November when the photoperiod was already less than 11 h and daily maximum temperatures less than 15 °C. Seedlings of these two species attained a greater degree of frost hardiness when exposed to persistent subfreezing temperatures. Under controlled conditions, 4 weeks of short photoperiod at warm temperatures (9 h light:15 h dark, 20:15 °C) had little effect on hardiness of the two cedars but increased hardiness in spruce to about −15 °C. Water stress increased hardiness in spruce under long photoperiod (18 h light: 6 h dark, 20:15 °C) but only marginally in western red and yellow cedar. Low temperatures (7:3 °C, light:dark, 9-h photoperiod) increased hardiness in all species. Exposure to 2 and −3 °C (light:dark, 9-h photoperiod) increased the rate of hardening in western red and yellow cedar but not in white spruce. The ability to deharden in white spruce was related to chilling requirements and not necessarily exposure to warm temperatures. The induction and maintenance of hardiness in the three species appear to be controlled by different environmental signals. Key words: photoperiod, low temperature, water stress, dormancy, dehardening.
Mode of the absorption of water and nutrients by ascocarps of Tuber melanosporum and Tuber aestivum: a radioactive tracer technique
Authors: Barry D. , Staunton S. , Callot G.
Published: December 2007

A simple technique has been developed to study the absorption capacity of the tufts of mycelial filaments, or hyphae, observed on both black and white truffles Tuber melanosporum and Tuber aestivum. These hyphae sprout from the tops of certain scales on the peridium of Tuber. They colonize the surrounding soil and could therefore exploit the nutrients from a large volume of soil. The ability to absorb organic and inorganic nutrients from a source other than the host is a necessary condition for the hypothesis we wished to test, namely that at some stage in its development the truffle ascocarp becomes autonomous. The absorption was demonstrated using autoradiography and liquid scintillation counting. We found that the tufts of hyphae are water permeable (3H2O). In addition, they absorb a sugar ([14C]mannose) and an anion ([32P]phosphate). An analysis of our results shows that the spatial distribution of [32P]phosphate is independent of that of tritiated water; the transport of phosphate is therefore not determined by water flux. The quantity and redistribution of the tracer depended on the application site, directly onto the peridium or on a mycelial tuft. The tufts increase the absorption of the tracer and influence its internal redistribution towards accumulation zones. Key words: ascocarp, Tuber melanosporum, Tuber aestivum, absorption, truffle nutrition.
Foliar sclereids of Olea europaea may function as optical fibres
Authors: Karabourniotis George , Papastergiou Nikos , Kabanopoulou Eleni , Fasseas Costas
Published: December 2007

Adaxial epidermises that contained an intact "subepidermal" "T"-shaped sclereid network, were isolated from olive tree leaves using a new method of enzymatic maceration. In the leaf, the sclereid network was anchored on the adaxial epidermis. The basal parts of the T-shaped sclereids penetrate the palisade cell layers into the underlying spongy parenchyma cells. In paradermal sections, the basal parts of the sclereids appeared as light-emitting sources or spots among the dark-green background of the palisade layers. The light spots almost disappeared when the intercellular air spaces were filled with immersion oil that had a similar refractive index to that of cell walls. It is plausible that light is propagated through multiple reflections between the thick cell wall of sclereids and the air filling the intercellular spaces, the former having a significantly higher refractive index. Sclereids act like synthetic optical fibres and, besides other functions, they may contribute to the improvement of the light microenvironment within the mesophyll of the thick and compact sclerophyllous leaves of Olea. Key words: foliar sclereids, optical fibres, light guiding, Olea europaea.
Crossability of naturalized and cultivated Lythrum taxa
Authors: Ottenbreit Kimberly A. , Staniforth Richard J.
Published: December 2007

Lythrum cultivars Morden Pink, Morden Gleam, and Dropmore Purple, and a wild population of Lythrum salicaria from Lockport, Manitoba were artificially self- and cross-pollinated. Success of pollination and fertilization was measured in terms of the percentage of resulting capsules and the average numbers of viable seeds per capsule. Germination tests were used to measure the viability of seeds produced as a result of successful crosses. Cultivars rarely produced seeds as a result of selfing but many crosses with wild plants or with other cultivars were fertile. As expected, legitimate (i.e., different style morphs) wild crosses were highly fertile, but other crosses gave high fertility, especially those in which 'Morden Gleam' was the provider of pollen or ovules. Although some sterility was indicated in 'Dropmore Purple' and perhaps 'Morden Pink', neither are sufficiently sterile to be considered safe for ornamental flower gardens. Most illegitimate crosses yielded greatly reduced seed outputs in comparison to legitimate crosses, but there were some exceptions. Germinability of ripe seeds from any cross was high and averaged 98%. Cultivars of Lythrum are capable of contributing viable seed and (or) pollen to the spread of purple loosestrife. The sale of cultivars, regardless of parentage, should be prohibited. Key words: purple loosestrife, Lythrum spp., interfertility, hybridization.
Detection of Leptosphaeria korrae with the polymerase chain reaction and primers from the ribosomal internal transcribed spacers
Authors: O'Gorman D. , Xue B. , Hsiang T. , Goodwin P. H.
Published: December 2007

Leptosphaeria korrae, the causal agent of necrotic ring spot, is a destructive patch disease of Kentucky bluegrass. To develop a rapid molecular test for the detection of this pathogen, an assay based on the polymerase chain reaction (PCR) was developed utilizing the internal transcribed spacer region 1 (ITS 1) of L. korrae ribosomal DNA. DNA sequence comparison showed 94.8% similarity of the ITS 1 region among L. korrae isolates and only 45–50% similarity between L. korrae and other fungal species. Based on ITS 1 sequence differences, a pair of oligonucleotide primers, LK17S and 5.8SC, were selected. With PCR, the primers specifically amplified L. korrae DNA and did not amplify DNA isolated from 15 other fungal species or healthy Kentucky bluegrass. The assay could also specifically detect L. korrae in diseased turfgrass samples. Key words: detection, ITS 1, Leptosphaeria korrae, necrotic ring spot, polymerase chain reaction, ribosomal DNA.
Pollen development in Liriodendron tulipifera: some unusual features
Authors: Guzzo Flavia , Baldan Barbara , Bracco Francesco , Mariani Paola
Published: December 2007

Pollen development in Liriodendron tulipifera has some unusual features. Two arrangements in tetrads could be detected: isobilateral and decussate types. The occurrence of one or the other pattern seems to be random. The sulcus position is marked early by an exine fold forming at the beginning of wall deposition at the distal pole of tetrad cells. During increasing microspore volume, the exine outgrowth is unfolded, then stretched and finally broken up, thus exposing the intine below. Plastids are usually excluded from the generative cell, indicating that their inheritance is predominantly maternal. Nevertheless our cytological results give evidence of a trace paternal transmission of plastids. Some evolutionary considerations are made. Key words: microsporogenesis, Liriodendron tulipifera, postmeiotic cytokinesis, sulcus determination, ultrastructure.
The influence of experimentally induced changes in the (Mg + Ca):K balance on protein bodies formed in developing Cucurbita seeds
Authors: Lott John N. A. , Ockenden Irene , Kerr Patrice , West Marcia , Leech Thelma , Skilnyk Hilary
Published: December 2007

Phytate, the main mineral nutrient storage compound in seeds, is stored inside protein bodies. Phytate is usually concentrated in dense bodies called globoid crystals. In 1985, Lott and co-workers proposed that the balance of (Mg + Ca):K may be important in controlling globoid crystal formation and provided some experimental evidence to support this proposal. To test this hypothesis further, developing Cucurbita fruits were injected with sterile K salt solutions. Squash cotyledons generally have large globoid crystals and a relatively high (Mg + Ca):K ratio. We hypothesized that experimental reduction of the ratio by the addition of K would result in the alteration of the size and number of globoid crystals. Developing seeds were remarkably resistant to attempts to alter the elements taken up for storage. The elemental content of embryo tissues was measured quantitatively with neutron activation analysis. Controls plus those few samples showing a distinct shift in the ratio owing to elevated K content were analyzed further. Energy dispersive X-ray analysis of cryogenically prepared samples was used to study the elemental content of globoid crystals and transmission electron microscopy was used to study the ultrastructure of the protein bodies. The results provide additional support for the hypothesis being tested. Key words: phytate, globoid crystals, Cucurbita, seeds, mineral nutrients, protein bodies.
Infection of adventitious roots of Agrostis palustris by Pythium species at different temperature regimes
Authors: Hodges Clinton F. , Campbell Douglas A.
Published: December 2007

Pathogenicity of several isolates of Pythium species to the adventitious roots of Agrostis palustris was evaluated at high (35:24, light:dark) and low (24:13 °C, light:dark) temperature regimes. Isolates of P. graminicola–arrhenomanes, P. rostratum, P. torulosum, P. vanterpoolii, and one unclassified species were evaluated. All isolates of all species infected roots. Some isolates of P. graminicola–arrhenomanes (PGA-5), P. torulosum (PT-1, PT-2, PT-3, PT-5), P. vanterpoolii (PV-1), and an unclassified species (UP-1) infected roots and decreased dry weight at both the high and low temperature regimes. Other isolates of P. graminicola–arrhenomanes (PGA-1, PGA-2, PGA-4, PGA-6, PGA-7) and P. torulosum (PT-4) infected roots and decreased dry weight only at the high temperatures. Isolate PGA-7 of P. graminicola–arrhenomanes also stimulated plant growth at low temperatures. The remaining isolates of P. graminicola–arrhenomanes (PGA-3), P. rostratum (PR-1), and P. vanterpoolii (PV-2) infected roots and decreased dry weight only at the low temperatures. Infection of roots was limited to root hairs, root tips, and epidermal and cortical tissues. The observations are discussed relative to the function of Pythium species as minor root pathogens and their potential function in disease complexes. Key words: disease complexes, infection, minor pathogens, pathogenesis, pathogenicity, Pythium arrhenomanes, P. graminicola, P. graminicola–arrhenomanes, P. rostratum, P. torulosum, P. vanterpoolii.
The desert epiphyte Tillandsia recurvata harbours the nitrogen-fixing bacterium Pseudomonas stutzeri
Authors: Puente Maria-Esther , Bashan Yoav
Published: December 2007

Pseudomonas stutzeri, a nitrogen-fixing bacterium, was isolated from the interior of the desert epiphyte Tillandsia recurvata, which grows on electrical cables and giant columnar cacti in the semiarid zone of Baja California, Mexico. This study is the first to indicate the possible close association between bromeliad plants and nitrogen-fixing bacteria. Key words: beneficial bacteria, bromeliads, Bromeliaceae, nitrogen fixation, Pseudomonas stutzeri, Tillandsia recurvata.
Intrathalline variability of some structural and physical parameters in the lichen genus Lasallia
Authors: Valladares F. , Ascaso C. , Sancho L. G.
Published: December 2007

The intrathalline variability of several physical and anatomical parameters of two lichens, Lasallia hispanica and Lasallia pustulata within the family Umbilicariaceae, was studied. In each thallus three zones or concentric rings were considered: the central zone, which includes the umbilicus, the intermediate zone, and the marginal zone. The study focussed on the thickness of the thallus and its layers, the increase of surface area and volume with hydration, the sample densities in dry and wet states, several stereological parameters (especially the volume and surface density of both symbionts related to each layer and to the thallus as a whole), and the chlorophyll content. Only slight differences were revealed between the two species, but significant intrathalline variation was observed. A marked decrease in the total chlorophyll content coincided with the thickening of the thallus from the periphery to the centre. The chlorophyll content of individual algal cells, however, presented an inverse gradient. The results suggest that the main role of the dense central zone would be as a water-holding zone while the active growth in the intermediate zone could counteract the continuous erosion of the marginal zone of these umbilicate lichens. Key words: Lasallia, intrathalline variability, mycobiont, photobiont, stereology, thallus density.
Trace metals in submerged plants of the St. Lawrence River
Authors: St-Cyr Louise , Campbell Peter G. C.
Published: December 2007

Vallisneria americana Michx. (wild celery), a submerged plant ubiquitous in the fluvial lakes St. Louis and St. Pierre of the St. Lawrence River, Quebec, shows potential as a bioindicator species for trace metals in its environment. The Cd, Cr, Cu, Ni, Pb, and Zn concentrations in V. americana leaves reflect spatial variations in environmental contamination and represent bioavailable trace metals potentially transferable through the food chain to higher organisms. With the exception of Pb, V. americana concentrates trace metals to higher levels in its aboveground tissues than does Potamogeton richardsonii (A. Bennett) Rydb., another abundant species in the studied lakes, although the two species show the same trend to higher trace metal concentrations at the more contaminated stations. Vallisneria americana from Lake St. Pierre shows higher concentrations for all trace metals studied than does the same species from Lake St. Louis (mean concentrations in μg/g dry wt. for Lake St. Pierre versus Lake St. Louis: Cd, 1.62 vs. 0.89; Cr, 3.9 vs. 2.5; Cu, 20.0 vs. 16.5; Ni, 13.1 vs. 5.6; Pb, 3.3 vs. 2.0; Zn, 130 vs. 91). Mean concentrations of Cd, Cr, Ni, and Zn exceed median values of these concentrations for aquatic plants from contaminated sites, as reported in the literature. Key words: Vallisneria americana, Potamogeton richardsonii, bioindicator, trace metals, St. Lawrence River.
Restriction fragment length polymorphisms demonstrate single origin of infection centers in Phellinus weirii
Authors: Bae Hanhong , Hansen Everett M. , Strauss Steven H.
Published: December 2007

Restriction fragment length polymorphism (RFLP) markers were used to study genetic variation in the basidiomycete fungus Phellinus weirii (Murr.) Gilbertson, the cause of laminated root rot of conifers. In an initial study, three isolates each from the Douglas-fir type and the cedar-type biological species were surveyed with 12 restriction enzymes and 20 random, mitochondrial, and nuclear-ribosomal gene probes. The two biological species were distinct with most probe–enzyme combinations (91%). Variation within biological species was detected for the random and ribosomal DNA probes but not for the mitochondrial DNA probes. In a subsequent study 65 probe–enzyme combinations (13 × 5) that had detected variation within the Douglas-fir type biological species were used to analyze 27 isolates derived from six infection centers, two host species, and two geographic areas in western Oregon. Infection centers differed from one another in numerous probe–enzyme combinations but were nearly genetically uniform within. Isolates from the two host species, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and mountain hemlock (Tsuga mertensiana (Bong.) Carr.), showed few RFLP differences. Initiation of infection centers, and subsequent vegetative or basdiospore initiated immigration, appear to be rare events. Key words: ribosomal DNA, mitochondrial DNA, RFLP, root rot, conifer.