摘要:

Lotus corniculatus, birdsfoot trefoil, is a Eurasian perennial legume, popular in temperate climates for pasture or hay and silage production. Its ancestry is controversial. While innumerable studies ofL.corniculatusand allied species have been published, comprehensive morphological, geographical, and genetic studies are still needed. Nevertheless, there is sufficient information for a provisional analysis of the origin and relationships of this important economical species. Although sometimes defined to have diploid populations,L.corniculatusessentially appears to be tetraploid. Biochemical and genetic evidence indicates that this species is an allotetraploid. Although about a dozen diploid species have been proposed as ancestral toL.corniculatus, the evidence points strongly to four of these species.Lotus uliginosusuniquely shares a rhizomatous habit, an acyanogenic factor, and a tannin characteristic withL.corniculatus, clearly showing an especially close relationship, and reflecting the possibility that it is one of two direct parental species. Principal candidates for a second parent includeLotus alpinus,Lotus japonicus, andLotus tenuis. A phenetic analysis presented here accords well with the hypothesis favoured in this paper thatL.corniculatusarose as a hybrid ofL.tenuisandL.uliginosus. Cytogenetic evidence indicates thatL.japonicusis especially closely related toL.corniculatus. Flower colour in the hybrids betweenL.uliginosusandL.tenuissuggest maternal inheritance and thatL.tenuiscould have been the female parent. An evolutionary sequence is suggested in whichL.uliginosushybridized withL.tenuisfollowed by introgression fromL.alpinusandL.japonicus. Alternatively, a prototype ofL.alpinus,L.japonicus, andL.tenuiscould have been the female parent ofL.corniculatus, based on evidence from maternal inheritance of flower colour intensity and interactions ofRhizobiumstrains.Keywords: polyploidy, hybridization, evolution,Lotusspecies, Fabaceae, birdsfoot trefoil,Lotus corniculatus.

ISSN:0008-4026    

DOI:10.1139/b96-122

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

After fertilization, the zygote divided unequally, giving rise to a larger basal cell and a smaller terminal cell. Derivatives from the basal cell gave rise to the suspensor and the terminal cell gave rise to the embryo proper. The suspensor usually consisted of a uniseriate file of 10–12 cells. However, additional anticlinal and oblique divisions resulted in some suspensors having more than one cell file. Cuticular substance was not present in the suspensor cell wall. The embryo proper was derived from the terminal four cells of the eight-celled embryo. The protoderm differentiated first, and subsequent to its formation cuticular substance could be detected in the outer tangential walls using the Nile red stain. This staining pattern intensified as the embryo matured. A defined cell lineage was not associated with tissue and meristem differentiation. Meristems began to form at the heart stage and became clearly defined at the late heart – early cotyledon stage.Keywords: cuticular material,Daucus carota, fluorescence, suspensor, zygotic embryogenesis.

ISSN:0008-4026    

DOI:10.1139/b96-123

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Existing descriptions of the sister speciesMazzaella splendensandMazzaella lineariswere insufficient to identify all low intertidalMazzaellathalli along a wave exposure gradient in Barkley Sound, British Columbia. After sampling size classes of sporophytes and gametophytes, uni- and multi-variate analyses indicated that thalli at low and intermediate exposure sites wereM.splendens, whereas thalli at the high exposure site wereM.linearis. The longer and thicker stipe ofM.linearisbest distinguishes it fromM.splendens, whereas the previously emphasized characters of blade width and angle at the blade base were not useful. The latter characters demonstrated gradual clines, and for the longer size class, blade width was not isomorphic between phases. The species alternated with each other along the shoreline depending on how rock topography influenced the arrangement of low, intermediate, and high wave exposure sites. Regressions that used an indicator of water motion (i.e., sucrose candy weight loss) to predict morphological variation were often significant. These regressions suggest that some factors affecting the distribution ofM.splendensandM.linearisalong the gradient are the degree of wave exposure itself as well as light and nutrient availability.Keywords:Mazzaella,Iridaea, cline, wave exposure, gametophyte, sporophyte.

ISSN:0008-4026    

DOI:10.1139/b96-124

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Surface-sediment samples from 23 lakes on the Taimyr Peninsula were collected along a transect from tundra to forest and analyzed for their pollen and coniferous stomate content.Larix sibirica, the dominant tree in forest–tundra and forest vegetation zones, is poorly represented in the pollen spectra, never exceeding 8%. To examine the correspondence between the modern pollen rain and the vegetation zones of tundra, forest–tundra, and forest, a principal components analysis was applied to the pollen percentages.BetulaandAlnusaccount for the greatest variance in the data set, and the set of tundra sites farthest north is distinct from the forest sites farthest south. Stomates ofL.sibiricaare present in all samples from sites whereLarixtrees are present, and some samples contained higher concentrations of stomates than pollen ofLarix.Picea obovatastomates are found less consistently and less abundantly thanLarixstomates.

ISSN:0008-4026    

DOI:10.1139/b96-125

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

TwoStreptomycesspp. and two herbicides were used to control the pathogens of tomato wilt disease in vitro and in vivo. In vitro studies showed inhibitory effects ofStreptomyces corchorusiiagainstFusarium oxysporumf.sp.lycopersici(Sacc.) and inhibitory effects ofStreptomyces mutabilisagainstPseudomonas solanacearum. In cultures amended with pendimethalin or metribuzin, the growths ofP.solanacearumandF.oxysporumwere inhibited. The degree of growth inhibition was proportional to the herbicide concentration, with pendimethalin being more effective than metribuzin, and maximum inhibition was at 2.0 × 10−3 M. The growth ofS.corchorusiiandS.mutabiliswas slightly inhibited or enhanced by the herbicides. Supplementation of the herbicides to culture media of the antagonisticStreptomycesspp. increased their inhibitory effects againstP.solanacearumandF.oxysporumthat were proportional to the herbicide concentrations. Soaking seeds of tomato in the herbicides prior to sowing in sterilized and raw soils and applyingS.corchorusiiand (or)S.mutabilisto the soils artificially infested withP.solanacearumand (or)F.oxysporumf.sp.lycopersici(Sacc.) 40 days after transplanting revealed significant interactions that gave better control of wilt than either applied alone. The combination of antagonisticStreptomycesspp. was more effective with pendimethalin than with metribuzin and in nonsterilized soil than in sterilized soil. The combination of pendimethalin withS.corchorusii,S.mutabilis, orS.corchorusiiplusS.mutabiliswas more effective than the single treatment with microbial antagonists or the herbicide againstF.oxysporum,P.solanacearum, andPseudomonasplusFusarium, respectively. In both soils, the combination of microbial antagonists with pendimethalin was most effective at 2.0 × 10−3 M, disease incidence being reduced to zero and the percent colonization of either pathogen being the lowest. The results also revealed that these combinations minimized the negative effects of the pathogens on tomato growth. This work demonstrates that two compatible control agents, biological and chemical, can be combined to give additional control of a plant pathogen.Keywords:Streptomycesspp., herbicides,Pseudomonas solanacearum,Fusarium oxysporumf.sp.lycopersici(Sacc.), wilt,Lycopersicon esculentumMill.

ISSN:0008-4026    

DOI:10.1139/b96-126

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The authors discuss presuppositions of classical plant morphology and point out the difficulties of classical (classificatory) typology (based on typical forms that are mutually exclusive, categories such as shoot, root, leaf, or trichome), which have been known for a long time. It is shown how these difficulties can be overcome by a more open morphology concept that is continuous and dynamic. Furthermore, it is pointed out that such an approach works through an appropriate methodology based on principal components analysis and a decomposition of the plant into nested morphological articulations.Keywords: plant morphology, continuum morphology, dynamic morphology.

ISSN:0008-4026    

DOI:10.1139/b96-127

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Monitoring cell-wall formation in vivo with Fluorescent Brightener 28, by fluorescence microscopy, revealed that tobacco protoplasts regeneration started within 30 min indicated by cellulose microfibril formation at distinct sites on the protoplast surface. Oriented cellulose microfibril deposition was apparent before elongation and indicated the early polarization of protoplasts. The sequence of cellulose microfibril deposition correlates with an helicoidal-like texture. Within 6 h, a texture was completed. Tobacco suspension cells, stained by decolourized aniline blue, showed radiant granular callose fluorescence in cell plates and transverse walls. During the culture cycle of suspension cells, transverse fibrillar deposits of callose gradually appeared in the lateral walls during the log-phase, and subsequently disappeared in the early stationary phase of the cell culture. Similar callose transitions were observed in regenerated elongating protoplasts. Culture cells ofMorinda citrifoliaL. only showed transient granular depositions in the lateral walls. The callose formations did not result from artificial wounding. The transient appearance of callose might be related to cellulose microfibril deposition.Keywords: aniline blue, Calcofluor White ST, callose, cellulose, Fluorescent Brightener 28,Morinda citrifolia,Nicotiana tabacum.

ISSN:0008-4026    

DOI:10.1139/b96-128

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Spermogonia ofCronartium quercuumf.sp.fusiformedeveloped just beneath the bark on galled regions of infected pine seedlings. Spermogonia consist of flattened, spreading, island-like masses of fungal tissue covered with a thin layer of liquid containing large numbers of spermatia. Spermatia arose in an annellophoric fashion from the tips of long, slender sporogenous cells produced in a distinct layer. Each sporogenous cell contained a large prominent nucleus that underwent mitosis as each spermatium initial developed. One of the resulting nuclei moved into the initial while the other remained in the sporogenous cell. Once a spermatium was delimited, it was pushed away from the tip of the sporogenous cell as another spermatium initial developed below it. Once delimited, a spermatium underwent specific morphological changes as it matured. A mature spermatium was subpyriform in shape and surrounded by a thin wall. In addition to a single large nucleus each spermatium contained ribosomes, mitochondria, lipid bodies, strands of endoplasmic reticulum, vacuole-like inclusions, and many small vesicles that packed its base.Keywords: transmission electron microscopy, pycnidia, pycnidiospores, spermogonia.

ISSN:0008-4026    

DOI:10.1139/b96-129

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Isozyme analysis was used to determine species relationships and diversity among stem rust fungi (CronartiumandPeridermiumspp.) infecting hard pines (subg.Pinus) in the western United States. Electrophoresis was carried out on aeciospore extracts of 270 hard pine stem rust isolates representing nine species and forms. Consistent banding patterns (electromorphs interpreted as phenotypes) were obtained for all isolates at 11 enzyme loci. Within species groups, multilocus phenotypes were diverse at several loci. Nevertheless, each species exhibited a unique set of phenotypes that distinguished it from all others. For diagnostic purposes, banding patterns from just two loci were sufficient to distinguish all species and most forms or races examined. Two taxa that were thought to be forms of existing species may be new, undescribed species. For comparison with western hard pine stem rusts, multilocus phenotypes were determined for 13 additional isolates of four related pine stem rust species. Phenotypes for all rust species were analyzed in all possible combinations using pairwise distance analysis (neighbor-joining). WhenCronartium ribicolais treated as the outgroup, the resulting phenogram groups all 72 multilocus phenotypes into distinct species clades. Origins of autoecious, short-cycledPeridermiumspp. may be inferred from their placements relative to macrocyclic, heteroeciousCronartiumspp.Keywords:Cronartium,Peridermium, species diversity, species relationships.

ISSN:0008-4026    

DOI:10.1139/b96-130

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Resynthesis studies were done to determine the ecological role ofLeptodontidium orchidicola, a dematiaceous hyphomycete commonly associated with roots of plants growing in cool and humus-rich soils. Results were compared with those ofPhialocephala fortinii, another common root endophyte with similar cultural and vegetative characteristics. In axenic culture withSalix glaucaseedlings,L. orchidicolacaused a marked increase in host root length but also invaded the stele, causing extensive cellular lysis.Phialocephala fortiniiformed a Hartig net and a thin, patchy mantle. In pot monocultures withPotentilla fruticosa,Dryas octopetala,S. glauca, andPicea glaucaseedlings, the effects of fourL. orchidicolastrains on host dry weight were strain- and host-specific; the effects ofPhialocephala fortiniiwere also host-specific.Leptodontidium orchidicolaformed a range of symbiotic associations that could be considered mycorrhizal to parasitic, whereas the effects ofPhialocephala fortiniisuggest amensal, parasitic, or neutral association. In pot combination cultures, thePhialocephala fortinii–Potentilla fruticosasymbiosis resulted in a significant increase in shoot weight in contrast with the results of the same symbiosis in monoculture resynthesis. The resynthesis experiments demonstrated that the effects of bothL. orchidicolaandPhialocephala fortiniialso vary according to cultural conditions.Keywords:Leptodontidium orchidicola,Phialocephala fortinii,Mycelium radicis atrovirens, fungus–plant symbiosis, subalpine plants.

ISSN:0008-4026    

DOI:10.1139/b96-131

出版商:NRC Research Press    

年代:1996

数据来源: NRC