摘要:

Fifty-four strains of the entomopathogenic fungusPaecilomyces farinosus, half of which had been isolated from balsam fir litter and half of which had been isolated from naturally infected spruce budworm larvae, were evaluated for their use of a number of complex carbohydrates and other carbon sources, to determine their potential saprophytic ability. The fungi were also tested for (i) their ability to grow on and to decompose balsam fir litter, and (ii) their ability to survive desiccation, which is likely to occur in the tree canopy. The fungi produced a wide range of enzymes, including cellulases, chitinases, and proteases. They also grew on and decomposed balsam fir litter. A discriminant analysis showed a tendency for the strains isolated from spruce budworm to grow better on gelatin, whereas those from the litter grew better on cellulose. We conclude thatP.farinosusis a versatile saprophyte, capable of opportunistically parasitizing spruce budworm larvae. These characteristics could be important when consideringP.farinosusas a possible agent of biological control.Key words:Paecilomyces farinosus, entomopathogen, spruce budworm, saprophytic ability, hydrolases.

ISSN:0008-4026    

DOI:10.1139/b91-001

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The anamorphic generaAntromycopsis,Sclerostilbum, andTilachlidiopsisare revised. Three anamorph species with basidiomycetous affinities are accepted inAntromycopsis:A. macrocarpa(Ellis & Everh.) comb.nov. (basionymStilbum macrocarpum), previously known asA.broussonetiae(teleomorph:Pleurotus cystidiosus),A. angustatasp.nov. for the presumed anamorph ofPleurotus angustatus, andA. guzmaniisp.nov. (teleomorphPleurotus smithii). A description and illustration are presented of the type species ofTilachlidiopsis,T.racemosa, the anamorph ofCollybia racemosa.Sclerostilbumis considered a taxonomic synonym ofTilachlidiopsis.Nothoclavulina ditopa, the anamorph ofArthrosporella ditopa, is illustrated and briefly discussed.Key words: anamorph–teleomorph connections,Antromycopsis, Sclerostilbum,Pleurotus,Collybia, nematophagous fungi.

ISSN:0008-4026    

DOI:10.1139/b91-002

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The effect of ochratoxin A on growth and aflatoxin production byAspergillus parasiticuswas investigated. High concentrations had a significant effect, causing stimulation of aflatoxin production.Key words:Aspergillus parasiticus, aflatoxin production, ochratoxin A.

ISSN:0008-4026    

DOI:10.1139/b91-003

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Lanthanum was used as an electron-dense marker of apoplastic transport in the brown algaCystoseira nodicaulis. A lanthanum salt, La(NO3)3, was given in seawater at the base of excised branches for 2–8 days. Lanthanum transport into two regions distant from the point of application, the base and apex of the branches, was followed over time by electron microscopy. Restricted localisation of the deposits confirmed that an apoplastic pathway exists in this alga. The kinetics of transport are slow. Dense deposits were located exclusively in the cell walls of meristoderm and cortex cells. The significance of apoplastic transport in algae is discussed in the context of long-distance transport. The existence of an apoplastic route does not exclude the occurrence of symplasmic transport, which is suggested by the numerous plasmodesmata present in the medulla.Key words: algae, apoplast,Cystoseira, lanthanum, long-distance transport.

ISSN:0008-4026    

DOI:10.1139/b91-004

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Immature embryos ofZea maysL. were cultured on N6 medium to obtain embryogenie callus. Cultured tissue fragments with various developmental stages of friable callus were sampled and prepared for light microscopy and transmission electron microscopy. Pieces of compact callus were also prepared for light microscopy to compare the structural organization of both callus types. Friable callus develops from a thin layer of abaxial scutellum cells, including the epidermis. During further development the callus cells dissociate, owing to the breakdown of the middle lamellae, while older vacuolated cells degenerate. This results into long cell aggregates separated by large intercellular spaces, giving the callus its friable appearance. The microscopical sections showed a striking difference between friable and compact callus. Vascular elements were not found in the friable callus. On the contrary, vascular bundles were prominent in compact callus. Friable callus is therefore correlated with a less differentiated state than compact callus. The embryogenic potential of friable callus is situated in embryogenic units. These are aggregates of small isodiametric cells containing a central nucleus, an electron-dense cytoplasm, and many organelles. Proliferation was only observed in these cells, which are therefore presumed to generate new embryogenic units, somatic embryos, and vacuolated callus cells. The results further indicate that discrete masses of embryogenic cells, possibly early embryoids, have a unicellular origin.Key words:in vitroculture, callus, somatic embryogenesis, ultrastructure,Zea mays.

ISSN:0008-4026    

DOI:10.1139/b91-005

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Implications of phenotypic plasticity in a subspecific numerical taxonomic study ofOrnithogalum montanumCyr. (Liliaceae) are discussed. Clones belonging to six natural populations were grown in a glasshouse, and their morphological response to three water dosages was analyzed by means of principal component analysis. PC-1 ranks the three groups of replicated populations, suggesting a high degree of phenotypic plasticity; on the other hand, PC-3 is almost environmentally independent. Proximities in the phenetic space are shown to be at least partially environmentally dependent, suggesting a reaction norm for the character correlation matrix. The results do not corroborate a previous recognition of six subspecies ofO.montanum.Key words: phenotypic plasticity, numerical taxonomy,Ornithogalum, reaction norm, principal component analysis.

ISSN:0008-4026    

DOI:10.1139/b91-006

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Mycofloral communities colonizing winter wheat roots were quantified in five crop sequences involving winter wheat preceded by either spring wheat, spring oats, spring barley, spring canola, or flax. Fungi were categorized into groups (major pathogenic, minor pathogenic, and nonpathogenic) based on their ability to cause root disease. Forty-six species of fungi were identified, of which the principal species wereAlternaria alternata,Fusarium acuminatum, andMicrodochium bolleyi. Isolates from the genusFusariumformed the largest proportion of the mycofloral community. Fungal species that comprised root-colonizing communities were generally the same, and there were no significant differences in the total numbers of fungal species and isolates recovered in any of the crop sequences examined. However, the ratio of major pathogenic isolates to other isolates (minor pathogenic and nonpathogenic) was significantly different (in 1985) and a trend towards lower levels of root disease with decreasing ratios was seen. The most destructive of the root rot pathogens identified wasGaeumannomyces graminisvar.tritici. Generally, the lowest ratio of major pathogenic to all other isolates and the lowest levels of root disease and root colonization (expressed as numbers of fungal isolates and species recovered) occurred in sequences involving flax and canola.

ISSN:0008-4026    

DOI:10.1139/b91-007

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The growth and development of the syncytium induced by the beet cyst nematode (Heterodera schachtiiSchmidt) in rape (Brassica napusvar.oleifera) and its relationships to adjacent root tissues were studied by serial sectioning and electron microscopy. In a 5-day-old syncytium, xylem parenchyma cells formed the largest part of the syncytium volume, while pericycle cells constituted the smallest fraction. Xylem parenchyma cells outside the confluent part of the syncytium were the first cells to differentiate into syncytium-component cells at the leading edges of syncytia. Early stages of differentiation were characterized by an increase in ribosomes and rough endoplasmic reticulum. Later stages involved formation of tubular structures and cell wall ingrowths. In lateral roots, into which main root syncytia extended, xylem differentiation was disturbed by strong hypertrophy of xylem parenchyma cells. Here, xylem tracheary elements similar to graniferous tracheary elements occurred. The parasitism ofH.schachtiiin rape induced dramatic changes in root morphogenesis, and the response of xylem parenchyma cells was of fundamental importance in this host–parasite system.Key words:Brassica napus,Heterodera schachtii, syncytium, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b91-008

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The anatomy and ultrastructure of syncytia induced in white mustard (Sinapis albaL.) by the beet cyst nematode (Heterodera schachtiiSchmidt) were studied in the nematode-susceptible cultivar Trico and the nematode-resistant cultivar Maxi. Although syncytia in both cultivars could reach similar volumes, they differed considerably in their ultrastructure. In the susceptible cultivar, xylem parenchyma cells responded with extensive hypertrophy, an increase in plastids and tubular smooth endoplasmic reticulum, and formation of elaborate ingrowths of the cell walls abutting the xylem tracheary elements. In the resistant cultivar, xylem parenchyma cells, occasionally incorporated into the syncytium, necrotized. Normally, however, these cells resisted incorporation and stopped the syncytia from reaching the xylem tracheary elements. This resulted in the differentiation of cell wall ingrowths on the inner tangential walls of neighbouring stelar parenchyma cells. The improper coordination of syncytium differentiation with xylem morphogenesis, the malfunction in the symplast–apoplast interaction with an abnormal deposition of protoplasmic constituents into the apoplast, the small number of plastids, the lack of tubular smooth ER and degradation processes, further demonstrated the incompatible nature of the host–parasite interaction in the resistant cultivar Maxi.Key words:Sinapis alba,Heterodera schachtii, ultrastructure, resistance.

ISSN:0008-4026    

DOI:10.1139/b91-009

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Blueberry species are important for assessment of pollutant impacts in boreal settings because they are effective colonizers of disturbed sites, are tolerant of high levels of certain heavy metals, and are an attractive food for humans. To investigate patterns in its accumulation of elements and to provide background data, the concentrations of Al, B, Ba, Br, Ca, Ce, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Si, Sr, Ti, Zn, and Zr were measured in leaves ofVaccinium angustifoliumAit. collected at 64 sites across much of the species range in Canada. These included both cultivated and natural populations. Ranges for 24 other elements inVacciniumspecies have been compiled from the literature. Measurements of site and soil characteristics were made for the 64 sites to investigate their effects on concentrations in leaves. The concentration data were right-skewed, and this has implications for both data analysis and environmental impact assessment. The concentrations of most elements were positively correlated, and this was related to soil organic matter content and other soil properties. Plant concentrations were only weakly related to soil concentrations. Plant height was positively correlated to soil pH and leaf Ca, opposite to the expected trend. Overall, about half of the variation in plant concentrations was related to site-to-site variation; with the exception of Ni and Mg levels around Sudbury, Ontario, there was little indication of spatial grouping. The data indicate a relatively homogeneous elemental composition ofV.angustifoliumacross the range sampled and between cultivated and natural populations.Key words: metals, nutrient, background, impact, pollutant.

ISSN:0008-4026    

DOI:10.1139/b91-010

出版商:NRC Research Press    

年代:1991

数据来源: NRC