摘要:

Meiosis, spindle pole body cycle and septal pores inHerpobasidium filicinumwere examined using light and electron microscopy and compared with findings in the Uredinales and other simple-pored heterobasidiomycetes. The septal pore apparatus inHerpobasidium filicinumis rustlike, and the nuclear characteristics are also similar but not identical to those found in the Uredinales. Some details, such as the spindle pole body behaviour at prophase, the presence of a complete wrapping of endoplasmic reticulum surrounding the nucleus during division, the extension of the spindle pole body into the cytoplasm during division, and the nucleolus behaviour, distinguishHerpobasidium filicinumfrom the rusts. On the other hand, nuclear division and spindle pole body characteristics inHerpobasidium filicinumshow some features common withCryptomycocolax abnorme. However,Herpobasidium filicinumshares more important nuclear features withPachnocybe ferruginea,Eocronartium muscicola,Helicobasidium mompa, andHelicobasidium brebissoniithan with the Uredinales or Cryptomycocolacales. Apart from the phylogenetic implications of the ultrastructural data, the most interesting observation in the present work is the unusual type of meiosis. No evidence for meiosis II was found in basidia ofHerpobasidium filicinum. Instead, the genesis of the interphase I spindle pole body inHerpobasidium filicinumis essentially identical to the basidiomycetous postmeiotic and intermitotic spindle pole body duplication.Key words:Herpobasidium filicinum, heterobasidiomycetes, meiosis, septal pore, spindle pole body, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b94-151

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Three maize inbreds (MBR 6796-15, B86, and CI31A) resistant to leaf feeding by the European corn borerOstrinia nubilalis, and one susceptible inbred (MS72), were evaluated for insect resistance and phytochemical composition to gain a better understanding of maize-resistance mechanisms. Insect resistance was evaluated using laboratory bioassays that demonstrated that immature leaf tissue is the preferred feeding substrate. Phytochemical analyses were conducted for leaf protein, hydroxamic acid content, and hydroxycinnamic acids bound to the cell wall for both immature and mature leaf tissue. Hydroxycinnamic acid distribution in cell walls was examined using five stains, autofluorescence, and microspectrophotometry. Phloroglucinol, azure B, diazotized salts ofp-nitroaniline and sulfanilic acid, and chlorine sulfite allowed visualization of phenolic localization but were not quantitative. Microspectrophotometer readings of epidermal, phloem, and xylem cell walls confirmed staining results, showing extremely low cell wall hydroxycinnamic acid levels in epidermal cell walls of immature leaf tissue. Foliar nitrogen content was not related to insect feeding preference. Hydroxycinnamic acid fortification of epidermal cell walls appears to correlate best with corn borer feeding preference, accounting for differential resistance between inbred lines and between tissue maturities. Microspectrophotometry may be useful as a technique for monitoring phytochemical resistance mechanisms in breeding programs.Key words: maize,Ostrinia nubilalis, phenolic, hydroxycinnamic acids, cell wall, microspectrophotometry, resistance.

ISSN:0008-4026    

DOI:10.1139/b94-152

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Nucleotide sequences of the nuclear, small-subunit (SSU) ribosomal RNAs, as inferred from polymerase chain reaction (PCR)-amplified products, are presented forAreschougia congesta(Turner) J. Agardh (Solieriaceae),Dasyphloea insignisMontagne (Dumontiaceae),Sarcothalia crassifolia(C. Agardh) Edyvane & Womersley (Gigartinaceae),Nizymenia australisSonder (Nizymeniaceae),Phacelocarpus peperocarpos(Poiret) Wynne, Ardré & Silva (Phacelocarpaceae),Plocamiocolax pulvinataSetchell,Plocamium angustum(J. Agardh) J.D. Hooker,Plocamium cartilagineum(Linnaeus) Dixon (Plocamiaceae),Rhodymenia linearisJ. Agardh (Rhodymeniaceae), andSphaerococcus coronopifoliusStackhouse (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 inPlocamiumandPlocamiocolaxare presented to buttress a case for thePlocamialesord.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.

ISSN:0008-4026    

DOI:10.1139/b94-153

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

We used multivariate methods to investigate the composition and spatial organisation of tundra plant communities in the Wellington Bay region of southeastern Victoria Island (69°N, 106°W). Ordination and classification of sites at an intermediate scale (≈ 1 ha) were conducted using principal components analysis and sums of squares agglomerative clustering on a matrix of standardized chord distances. The findings suggested eight vegetation classes. These communities are described floristically. At this spatial scale, the vegetation showed correspondence to elevation, slope, and thickness of soil, but not to aspect. The spatial patterns of multiple plant species and physical variables (i.e., slope of terrain and thickness of soil) were examined using multiscale ordination and double logarithmic regressions of variance on distance, respectively. Multiscale ordination revealed ever-increasing plant heterogeneity with distance (0.25 – 1600 m) and suggested only weak general patterns at scales ≤ 200 m. Similarly, variance in the physical factors tended to increase continually with distance. Both the vegetation and physical environment thus appeared to be organised on gradients.Key words: Arctic, classification, ordination, spatial scale, tundr

ISSN:0008-4026    

DOI:10.1139/b94-154

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Patterns in flowering and biomass allocation in seedlings ofRumex acetosellaL. 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 ofR.acetosellain relation to successional habitat change.Key words: density, sibling competition, succession, trade-off,Rumex acetosella, resource allocation.

ISSN:0008-4026    

DOI:10.1139/b94-155

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Achenes ofTragopogon dubiushave 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 ofT.dubiussuggests that the peripheral morphs may retain viability longer in the seed bank.Key words: somatic polymorphism, heteromorphism, germination, emergence,Tragopogon.

ISSN:0008-4026    

DOI:10.1139/b94-156

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Outcrossing rates were estimated in two artificial stands ofPinus 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 inP.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.

ISSN:0008-4026    

DOI:10.1139/b94-157

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Plant communities are described from an area on the Yukon – Kuskokwim (Y-K) delta of Alaska that is used extensively for brood rearing by three species of geese. Earlier studies identified plant species important as food for young geese, but few studies describe or quantify plant communities. We classified species presence or absence information from over 700 quadrats using a two-way indicator species analysis (TWINSPAN) and then tested for agreement of signatures on colour infrared air photos with the identified communities. Sedges were found to dominate all but the wettest and driest communities. Most of the brood-rearing area was covered byCarex ramenskiiandCarex rariflorameadows, ponds,Carex mackenziei-dominated pond margins, andC.ramenskiiand grass levee meadows. Our interpretation of airphotos accurately predicted vegetation community classes, which will facilitate future studies of habitat selection by geese during the time they are rearing young. TheTWINSPANclassification was comparable to classifications of studies conducted elsewhere on the Y-K delta. The interpretation of air photos will enable the identification and evaluation of wetland vegetation complexes and potential goose brood-rearing areas away from our study site.Key words: air-photo interpretation, Alaska, plant communities, salt marsh, Yukon – Kuskokwim delta.

ISSN:0008-4026    

DOI:10.1139/b94-158

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The taxonomy and ecology of the fungal genusBombardioidea(Ascomycotina, Lasiosphaeriaceae) are discussed. Descriptions and illustrations are provided for the four accepted species:Bombardioidea anartian.sp.,Bombardioidea bombardioides,Bombardioidea serignanensis, andBombardioidea stercoris. Observations from axenic culture are provided forB.bombardioides, and anAngulimaya(Phialophora-like) anamorph is reported. The coriaceous and gelatinous aspects of the peridium are considered to be adaptations to xerophytic environments.Key words:Bombardioidea,Angulimaya,Phialophora, coprophilous, ecology, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b94-159

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Genetic data were collected for glucose-6-phosphate isomerase locus 2 from a sample of theAcer saccharumMarsh. (sugar maple) embryo subpopulations of four forested patches in southwest Ohio and compared with the juvenile (1st-year seedlings to individuals ≤ 1.0 cm in basal area) and canopy (≥ 30 cm in diameter at breast height) subpopulations. Apparent gene flow into each patch was observed as certain alleles found in the embryo subpopulation were not observed in the canopy subpopulation. Genotype frequency data indicated that at least some of the gene flow could be attributed to seed dispersal. Although in some patches, the embryo subpopulation had lower genetic diversity than other subpopulations and was genetically differentiated, it is unlikely that these observed differences represent a change in the genetic diversity of future juvenile subpopulations.Key words: sugar maple, gene flow, genetic diversity, allozyme, forest fragmentation, seed dispersal.

ISSN:0008-4026    

DOI:10.1139/b94-160

出版商:NRC Research Press    

年代:1994

数据来源: NRC