摘要:

The floral development ofCoriswas investigated to clarify its controversial relationship with either Primulaceae (Primulales) or Lythraceae (Myrtales). We demonstrate thatCorisis strongly related to the Primulaceae but differs in a few important features, such as the presence of an epicalyx and partial zygomorphy. The saccate calyx and epicalyx with unilateral development encloses an actinomorphic flower. The stamen–petal tube has two sections that arise through three growth processes: a lower common part for stamens and petals and an upper section representing a fused corolla. The central ovule-bearing part of the ovary arises separated from the carpel wall. The formation of ridges with teethlike appendages between the ovules suggests a derivation of the free-central placentation from an axile arrangement. Several characters support the monotypic family Coridaceae near the Primulaceae.Key words: Coridaceae, Primulaceae, Lythraceae, floral development, floral vasculature, epicalyx, free-central placentation, common primordium, zygomorphy.

ISSN:0008-4026    

DOI:10.1139/b95-183

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Cladistic parsimony analyses, based on morphological data, have been undertaken with the purpose of identifying major monophyletic groups and phylogenetic interrelationships within the Primulales.Actinidia(Actinidiaceae, Ericales) and three genera from two families of the Ebenales (Diospyrosof the Ebenaceae andManilkaraandMonothecaof the Sapotaceae) were used as outgroups in the analyses. The results indicate that the Primulaceae, Theophrastaceae, and Myrsinaceae (excludingMaesa) represent three major monophyletic groups. The Myrsinaceae were found to be paraphyletic, with the majority of taxa forming a monophyletic group but with the genusMaesaconstituting the sister group of the Primulaceae. It is proposed thatMaesashould be raised to the rank of family to obtain strictly monophyletic groups in the Primulales. The generaAegicerasandCoris, for which family affinities have been controversial, are well nested within the families Myrsinaceae and Primulaceae, respectively.Key words: Primulales, Theophrastaceae, Myrsinaceae, Primulaceae, morphology, taxonomy, phylogeny, cladistics, classification.

ISSN:0008-4026    

DOI:10.1139/b95-184

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Electron microscopy and stereological analysis of cowpea (Vigna unguiculata) leaf tissue infected with the cowpea rust fungus (Uromyces vignae) revealed an increase in surface of plant endomembranes that was associated with callose synthesis or the presence of fungal haustoria. In the resistant cultivar in which the haustorium commonly becomes encased, an increase in surface of smooth membranes was observed in cytoplasmic regions adjacent to developing encasements compared with the regions away from the fungus or with any region in infected or uninfected callose nonsynthesizing cells. Cytoplasmic regions adjacent to the haustorium in callose nonsynthesizing cells had an increase in rough endoplasmic reticulum (ER). This increase was greater in a susceptible cultivar than in the resistant cultivar that was treated with tunicamycin to inhibit callose synthesis. In the latter situation, the lack of callose encasement allowed the haustorial neckband to form, but other ultrastructural signs of incompatibility remained, such as the presence of electron-opaque material associated with the extrahaustorial membrane. No differences between cultivars or treatments were observed in Golgi membranes. Our observations suggest that both callose synthesis and fungal presence are associated with de novo synthesis of membranes; callose deposition may require an increase in smooth membranes of uncertain origin, whereas the establishment of a haustorium may be dependent on increased synthesis of rough ER.Key words: callose, endoplasmic reticulum, resistance, stereology, tunicamycin.

ISSN:0008-4026    

DOI:10.1139/b95-185

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A study of the vegetation communities along two transects on the well drained slope of the Possession Island (subantarctic island, Indian Ocean) was carried out. The aim of this study was to investigate the structure of the vegetation under permanent pressure from gales and salt sprays and where there was no major perturbation. In the areas protected from gales, aBlechnum pennamarinacommunity dominates. This fern hinders the vegetation dynamics in two ways : (i) by forming a very dense canopy that prevents sunlight from reaching shorter plants (passive competition) and (ii) by the accumulation of thick litter resulting from dead fronds. This community thus acts as the "inhibition" model of Connell and Slatyer. In areas exposed to gales and salt spray,B.pennamarinapartly or completley disappears. The soil surface is consequently covered with several bryophytes andAzorella selagothat form a mosaic on the soil surface. The vegetation dynamics end at this stage, despite the ability ofB.pennamarinato colonize moss litter. The bryophyte community probably represent a stational climax stage acting as a "facilitation" model toB.pennamarinain an area protected from gales. It has therefore been concluded that the fernbrake community constitutes the optimal vegetation development on the well drained slopes of the Possession Island.Key words: climatic pressure, community ecology, bryophytes,Blechnum pennamarina, transect.

ISSN:0008-4026    

DOI:10.1139/b95-186

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Phosphinothricin is a microbial toxin currently under development as a selective weed killer in the cultivation of transgenic plants engineered to resist its presence. Here it is shown that phosphinothricin is inhibitory to antagonistic soil microorganisms includingBacillus subtilis,Pseudomonas flourescens, and many species ofTrichoderma. Phosphinothricin was also inhibitory to the phytopathogenic fungiRhizoctonia solaniandSclerotinia sclerotiorum. In contrast, phytopathogensFusarium oxysporumandPythium aphanidermatumwere highly resistant to phosphinothricin. In pathogen–antagonist challenges, species ofTrichodermathat parasitizeF.oxysporumandP.aphanidermatumwere eliminated when phosphinothricin was added to the growth media. Similarly, the ability ofPseudomonas fluorescensto excludePythium aphanidermatumwas markedly affected by the presence of phosphinothricin in the media. The dominance equilibrium betweenTrichodermaspecies and the bacteriumBacillus subtiliswas influenced in favor of the former at 0 and 5 mM concentrations of the herbicide and in favor of the latter at 1 mM concentrations.Pseudomonas fluorescenswas unable to excludeTrichodermaspecies regardless of the phosphinothricin concentration in the media.Key words: phosphinothricin, pathogens, fungi, bacteria, antagonists, biocontrol.

ISSN:0008-4026    

DOI:10.1139/b95-187

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

PseudoplectaniaandPlectaniacurrently belong to the Sarcosomataceae, tribe Sarcosomateae, a group with members lacking cyanophilic spore markings (absorbing a blue stain). The two genera are morphologically similar in having blackish discoid-shaped apothecia but differ in having globose and ellipsoid spores, respectively. Ultrastructural studies show that ascospores ofPseudoplectania nigrella(Pers. ex Fr.) Fuckel lack a secondary wall layer. On the contrary,Plectania nannfeldtiiKorf has secondary spore wall ornamentation that is cyanophilic under a light microscope. The data suggest retention ofPseudoplectania nigrellain the Sarcosomateae; however, the position of certain species ofPlectanianeeds to be reevaluated.Key words: Pezizales,Plectania,Pseudoplectania, Sarcosomataceae, spore ontogeny, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b95-188

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Mycelial interactions ofLaccaria bicolorstrains were studied in pure culture and after inoculation onto mycorrhizal hosts. Monokaryon–monokaryon and dikaryon–monokaryon crosses were performed on an agar medium that enhanced nuclear migration to study mating events. The first observance of clamped hyphae, their location, evidence of nuclear migration, and the occurrence of dikaryon–monokaryon matings varied among crosses. One monokaryon–monokaryon and two dikaryon–monokaryon combinations were selected for seedling inoculation to compare their mycorrhizosphere interactions with those observed on agar medium. Seedlings ofPinus banksianawere grown for 20 weeks in a mycelium inoculated soil medium. Three seedlings from each treatment were selected at harvest and ectomycorrhizae reisolates were subject to randomly amplified polymorphic DNA analysis to identify genotypes. This analysis was also done for mycelial samples of the same crosses on agar medium. Variation in the mycobiont genotype was observed for different root isolates from the same seedling, which had been initially inoculated with a compatible monokaryon–monokaryon or a dikaryon–monokaryon strain combination. Root isolates from seedlings receiving the latter treatment included a new dikaryotic genotype produced by a dikaryon–monokaryon mating. Seedling growth was reduced with ectomycorrhizal colonization, most likely because of the photosynthate requirements of the mycobiont during this study. The nature of mycelial interactions and the potential value of a genetically variable mycobiont are discussed.Key words: Buller phenomenon, ectomycorrhizae, intraspecific variability, mycelial interactions, RAPD analysis.

ISSN:0008-4026    

DOI:10.1139/b95-189

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In the dioecious perennialAsparagus officinalis, female function, estimated by the number of berries per plant and seeds per berry, was positively correlated with stem diameter and height and negatively correlated with stem number. In contrast, male function, estimated by the mean production of pollen per flower and by the number of male flowers per ramet, was positively correlated with stem number and negatively correlated with stem diameter and height. These correlations, which are calculated between mean values per genotype, are in accordance with sexual dimorphism in this species: male plants produce more but thinner stems than female plants. We propose that morphological constraints at the plant level could have favoured the evolution of dioecy in this species.Key words:Asparagus officinalis, dioecy, sexual dimorphism, pollen production, seed set.

ISSN:0008-4026    

DOI:10.1139/b95-190

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Basic chromosome numbers inLotusarex = 5, 6, and 7. It is considered that evolution has proceeded in the genus by means of a descending aneuploid series from an eight-chromosomed ancestor. Chromosome numbers for species ofTetragonolobusare based onx = 7. Somatic chromosome numbers are reported for 108 species and 38 varieties. The chromosome numbers for five species (L.hamatusGreene, 2n = 14,L.haydonii(Orcutt) Greene, 2n = 14,L.hintoniorumB.L. Turner, 2n = 14,L.mearnsiiBritton, 2n = 14,L.utahensisOttley, 2n = 14) and seven varieties (L.argophyllus(Gray) Green var.argenteusDunkle, 2n = 14,L.dendroideusvar.traskiae(Eastwood ex Noddin) Isely, 2n = 14,L.heermanii(Durand et Hilgard) Greene var.orbicularis(Gray) Isely, 2n = 14,L.junceus(Benth.) Greene var.biolettii(Greene) Ottley, 2n = 14,L.strigosusvar.hirtellus(Greene) Ottley, 2n = 14,L.strigosusvar.tomentellus(Greene) Isely, 2n = 14,L.uliginosusssp.vestitus(Lange) A. Pedersen, 2n = 12) are reported for the first time. Natural diploid, tetraploid, and hexaploid plants are reported forL.alpinus. Several species are reported as possessing B chromosomes. Mixoploidy is reported to occur in three species (L.alpinus,L.glacialis,L.glareosus). In addition, chromosome numbers are given for plants regenerated from calluses grown in tissue culture having both heteroploidy, euploidy, and mixoploidy. Root nodules are reported with tetraploid and octoploid cells in addition to the normal number of chromosomes. Trisomie series have been partially developed inL.tenuisandL.uliginosus. Polytene chromosomes were observed in suspensor cells of three species ofLotus. Feulgen cytophotometric measurements, to determine the DNA nuclear content, were made for 16 species ofLotusand one species ofTetragonolobus. The majority of the studies inLotusconcern the economic speciesL.corniculatus,L.tenuis, andL.uliginosus. Interspecific hybridization was carried out in different combinations between diploids, autoploids, and amphidiploids. Intergeneric hybrids were attempted by somatic hybridization, protoplast fusion, and asymmetric hybridization betweenLotusand other species (Glycine max,Medicago sativa,Oryza sativa).Key words: chromosome numbers, DNA values, Fabaceae,Lotusspecies, interspecific hybrids, intergeneric hybrids,Tetragonolobus.

ISSN:0008-4026    

DOI:10.1139/b95-191

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Leaf phenotypic plasticity of 12 morphological, anatomical, and growth traits was investigated using four species of arcticFestuca(F.baffinensis,F.brachyphylla,F.edlundiae, andF.hyperborea). Plants collected around 78°N in the Canadian Arctic Archipelago were grown for 10 weeks at the University of Toronto in growth chambers in continuous light, under four regimes of temperature and moisture. Significant differences were found between leaves at the time of field collection and leaves of the same plant at the end of the experiment in (i) leaf blade length, (ii) surface vestiture, both in trichome density and angle of the trichomes to the blade surface, and (iii) characters seen in leaf cross sections: blade width, rib thickness, and inter-rib thickness. The four species responded similarly to the experimental conditions, indicating that most of these changes represent part of the developmentally inevitable component of plasticity rather than species-specific adaptations. Trichome density was the only characteristic for which species showed different patterns of response, with a unique pattern of response inF.edlundiae. This and certain growth traits support the taxonomic status of this newly recognized species. The significant effects of temperature and to a lesser degree, water treatments on these leaf anatomical traits indicate that they should be used with caution for the purposes of taxonomy and identification.Key words:Festuca, leaf blade anatomy, phenotypic plasticity.

ISSN:0008-4026    

DOI:10.1139/b95-192

出版商:NRC Research Press    

年代:1995

数据来源: NRC