摘要:

In an analysis of a 50-year time series of seed production in bilberry (Vaccinium myrtillusL.) from Aust-Agder, southern Norway, both previous reproduction and weather contributed to explain annual berry production. There was a relatively regular fluctuation in bilberry production, with intervals between peaks of 2-5 years. The bilberry-production index was negatively correlated with the average bilberry production index of the preceding 3 years. Regularity in the bilberry production was commonly interrupted by unfavourable weather conditions. Depressed bilberry reproduction was associated with high temperatures during flower-bud formation in autumn, high temperatures in winters with thin snow cover, low temperatures during flowering in spring, and low or high amounts of precipitation during berry ripening in summer. It was concluded that, in Fennoscandia, climatic conditions may be responsible for the temporal and spatial synchrony in seed production in bilberry.Key words: bilberry, climate, mast, reproduction, synchrony, weather.

ISSN:0008-4026    

DOI:10.1139/b00-017

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Four pollen diagrams from Banks Island, Northwest Territories, provide the first records of the postglacial vegetation of the region. Chronologies are estimated from radiocarbon dates and by correlation of the exotic-pollen curves to data from the mainland. The pollen stratigraphies from all sites can be divided into three zones, where the middle zone, dating from 7000 to 2000 BP, corresponds to the warmest time. Although both the first and third zones correspond to cooler periods, the vegetation of the earliest zone was not identical to that of the latest, indicated by lower frequencies of key pollen types such as those ofDryasandSaxifraga.Key words: Banks Island, Holocene, pollen diagram, Arctic, paleoecology, Quaternary.

ISSN:0008-4026    

DOI:10.1139/b00-018

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Butomus umbellatusL. is an invasive emergent aquatic plant that exhibits wide variation in seed production. Native European populations are fertile and diploid or sterile and triploid. However, adventive North American populations are widely reported to be sexually sterile. We quantified sexual fertility and self-compatibility under greenhouse conditions for nine introduced populations from eastern Ontario, Canada. All populations were highly fertile and self-compatible. Each flower produced an average of 127 ± 7 (mean ± SE) filled seeds and 31.4 ± 0.4% of seeds germinated. This level of fertility is much higher than previously reported, even for fertile native populations. We also quantified the production of seeds, flowers, and inflorescence-borne asexual bulbils in 19 natural populations from eastern Ontario; 17 populations were highly fertile (200 ± 9 seeds/fruit) and 2 produced almost no seeds (0.0-0.3 seeds/fruit), because ovules were either not fertilized or were aborted soon after fertilization. We found no evidence of a trade-off between sexual reproduction and clonal reproduction via bulbils. The wide variation in reproductive strategy observed in these populations raises questions concerning the evolutionary loss of sex in clonal populations, and may have significant implications for the spread and management of this exotic species.Key words: aquatic plants, clonal reproduction, breeding systems, invasive plants, reproductive ecology, sexual sterility.

ISSN:0008-4026    

DOI:10.1139/b00-019

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Several definitions of leaf area index (LAI) presently exist in the literature but the relationships among them are not clear. To compare the results of various studies, there is a need to convert from one definition to another. Factors for converting among four definitions of LAI are presented for six conifer species:Abies grandis(Dougl. ex D. Don) Lindl.,Thuja plicataDonn ex D. Don.,Tsuga heterophylla(Raf.) Sarg.,Picea sitchensis(Bong.) Carr.),Pinus contortaDougl., andPseudotsuga menziesii(Mirb) Franco). Among the four definitions of LAI, the two extremes involve (i) the total area of the leaf and (ii) the projected area of nonhorizontal leaves, as they occur on the tree. If leaves are randomly oriented in space, then the conversion factor between definitionsiandiishould be 0.25. Four of the six species have conversion factors very close to this value, and three of these four are relatively shade-intolerant,. The remaining two species,A. grandisandThuja plicata, have conversion factors of approximately 0.35, owing to the approximately horizontal orientation of their leaves. These two species are both relatively shade-tolerant, and the trend toward horizontal leaves might be an adaptation to assist in shade tolerance. A sensitivity analysis indicated that the foliage of most of the species maximized the amount of light gathered when the light was coming from almost straight overhead, as is the case with many shaded forest trees.Key words: leaf area index, conifers, leaf area index conversion.

ISSN:0008-4026    

DOI:10.1139/b00-020

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The toxicities of four candidate peptides, which have potential for engineering disease resistance into poplars and conifers, were tested and compared in vitro. Cecropin B, (Ala8,13,18)-magainin II amide, and the two synthetic membrane interactive molecules (Peptidyl MIMs(tm)) D2A21 and D4E1 inhibited germination of spores of the fungal pathogensCronartium ribicolaJ.C. Fisch.,Gremmeniella abietina(Lagerberg) Morelet,Melampsora medusaeThuem.,Nectria galligenaBres. in Strass.,Ophiostoma ulmi(Buisman) Nannf., andSeptoria musivaPeck. Minimal inhibitory concentrations (MICs) of peptides required to achieve >95% inhibition of germination of conidia and urediniospores ranged from 0.3 to >5 µM. Permutation analyses on MICs confirmed that peptides significantly reduced germination of fungus spores (P= 0.0038) and that MICs of the two synthetic peptides were, on average, lower than those of the two natural peptides (P= 0.0012). In contrast, peptides had much less of an effect on the pollen ofPicea,Pinus, andPopulusspecies and seeds of white pine; MICs from 10 µM to >50 µM of peptide were needed to arrest germination. Peptidyl MIM(tm) D2A21 combined high antifungal activity with low pollen toxicity. Similar to some antimicrobial peptides from plants, Peptidyl MIM(tm) D2A21 could not prevent germination of fungal spores in the presence of potato dextrose broth or chloride salts with divalent cations. This may explain why the peptide had only a limited effect on fungal mycelium grown in potato dextrose broth medium.Key words: antimicrobial peptides (AMP), white pine blister rust, scleroderris canker, poplar leaf rust, Dutch elm disease, septoria canker.

ISSN:0008-4026    

DOI:10.1139/b00-025

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

In vitro effects of the antimicrobial synthetic D2A21 peptide on the structure of spores of four fungal pathogens causing important tree diseases were examined by microscopy in parallel with tests to measure inhibition of spore germination. With light microscopy, the use of SYTOX®green stain indicated that the peptide rapidly altered the plasma membrane of conidia of three Ascomycetes:Gremmeniella abietina(Lagerberg) Morelet var.abietinaPetrini et al.,Ophiostoma ulmi(Buism.) Nannf., andNectria galligenaBres. With basidiospores ofCronartium ribicolaJ.C. Fisch., a difference between control and treated spores was also found, but it was less pronounced than with conidia of the Ascomycetes. In transmission electron microscopy, untreated conidia showed typical cytoplasmic contents with the regular presence of mitochondria, ribosomes, and nuclei, at times accompanied by vacuoles of various sizes. At concentrations of the peptide inhibitory to spore germination, plasma membranes, as well as nuclear and mitochondrial envelopes, were either generally difficult to discern or were distorted and swollen. At more advanced stages, the cytoplasm of treated spores contained numerous vesicles and was in places more electron-dense than in controls. Cytoplasm leakage was also regularly observed. Present observations strongly suggest that the primary site of action of this peptide is located at the plasma membrane level.Key words:Cronartium ribicola,Gremmeniella abietina,Nectria galligena,Ophiostoma ulmi, D2A21, peptide

ISSN:0008-4026    

DOI:10.1139/b00-007

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Vegetative and reproductive tissues of maize,Zea maysL., were inoculated in vitro withFusarium moniliformeJ. Sheld. to determine inherent differences among plant tissue types to support mycelia proliferation. TheF. moniliformeisolate used for inoculations was tagged withgusA, a reporter gene, providing evidence that developing mycelia were from the inoculum source and excluding possibilities of an external contaminant or an internal endophyticF. moniliforme. Vegetative tissues were dissected from roots, stems, and leaves; reproductive tissues were dissected from developing male and female inflorescences and fruits. In addition, mycelial development was analyzed on nonwounded and wounded mature kernels.Fusarium moniliformemycelial accumulation was more rapid and extensive on reproductive than on vegetative plant tissue.Fusarium moniliformeconidia inoculated on immature kernels formed a dense mycelial mat, whereasF. moniliformeconidia inoculated on mature kernels developed sparse hyphae, unless the kernels had been wounded. Thus, the type, maturity, and physical condition of maize plant tissues are factors responsible for in vitro differences in mycelial proliferation.Key words: conidia, mycotoxins, plant pathogen, reproductive tissue, vegetative tissue,Zea mays.

ISSN:0008-4026    

DOI:10.1139/b00-022

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

An identification database for seeds in coastal habitats at La Pérouse Bay, Manitoba, Canada, was developed using the DELTA (DEscriptive Language for Taxonomy) format and the program INTKEY. The database should be applicable throughout the coastal lowlands of the Hudson Bay and James Bay regions as similar plant assemblages are present. The database, based upon morphological characteristics and also incorporating ecological information, was used to identify seed specimens found in soil cores and seed traps. The most useful characters for identifying seeds were seed length, seed width, and seed shape. The database is available on the World Wide Web at http://prod.library.utoronto.ca/polyclave/. The seed flora is also documented in the form of a checklist, the first one published for the La Pérouse Bay region; this checklist is also applicable to other coastal areas in the Hudson Bay lowlands.Key words: Arctic, DELTA, floristics, identification, seed morpholog

ISSN:0008-4026    

DOI:10.1139/b00-021

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Spores were sampled during 2 years over wheat plots at Ottawa, Ontario. Plots were treated with corn colonized withGibberella zeae(Schwein.) Petch (anamorphFusarium graminearumSchwabe). In 1994, viable spores were sampled with four Burkard high-throughput jet samplers.Gibberella zeaeascospores were recovered mostly at night and showed four main release events during the 20-day sampling period, 1-3 days after rain events. Highest density ofG. zeaespores (1500 spores/m3) were sampled 1.5 m away from the inoculum source, with fewer spores 5 m away. Recovery of otherFusariumspecies was sporadic. For all species, there were no statistical differences among the daily sampling times, although for most species, morning counts were the lowest. OtherFusariumspecies detected, in decreasing order of spore density, wereF. crookwellense,F. sporotrichioides,F. moniliforme,F. equiseti,F. subglutinans, andF. culmorum.Most spore release events did not correlate with rainfall events. In 1995, a Burkard continuous 7-day spore sampler was used to investigate the release of ascospores and macroconidia ofG. zeae. Ascospores, but not macroconidia, showed a daily periodicity. Daily average densities of macroconidia were an order of magnitude less than ascospores. Ascospore release was correlated with rainfall events and the time of day.Key words: spore sampling,Gibberella zeae,Fusarium graminearum,Fusariumsp. ascospores, macroconidia.

ISSN:0008-4026    

DOI:10.1139/b00-027

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Comparative sequencing of the two internal transcribed spacer regions of nuclear ribosomal DNA was carried out to examine evolutionary relationships among representatives of Old World Apiaceae (Umbelliferae) subfamily Apioideae. Emphasis was placed on delimiting groups within the previously designated apioid superclade and clarifying relationships within and among the peucedanoid generaAngelica,Ferula,Heracleum, andPeucedanum. These spacer data, and those obtained from the chloroplastrps16 intron for a subset of the taxa, also enabled hypotheses on the phylogenetic placement of several narrowly distributed endemic species. The monophyly of Drude's tribe Echinophoreae is confirmed and it is sister to the Socotran endemic generaNirarathamnosandRughidia; the Balearic Islands endemic genusNaufragaallies withApium graveolens; tribes Careae and Pyramidoptereae are recognized formally to be the previously designated clades "Aegopodium" and "Crithmum"; and tribes Oenantheae and Scandiceae are each expanded to include two species ofApium, previously attributable toHelosciadium, and four species ofFerula, respectively. Within the apioid superclade, five major lineages are recognized that are consistent with all available molecular evidence: tribe Echinophoreae, the clades "Pimpinella" and "Heracleum," and the more narrowly circumscribed clades "Angelica" and "Apium."AngelicaandFerulaeach comprise at least two lineages;Heracleumis polyphyletic ifHeracleum candicansis retained in the genus; andPeucedanumis distributed in three well-separated clades with some species allied with those species ofAngelicareferred toXanthogalum.Key words: Apiaceae subfamily Apioideae, nuclear rDNA ITS, chloroplastrps16 intron, Umbelliferae.

ISSN:0008-4026    

DOI:10.1139/b00-029

出版商:NRC Research Press    

年代:2000

数据来源: NRC