摘要:

In clonal plants likeButomus umbellatus, pollination between ramets commonly leads to geitonogamy since even distant ramets may belong to a common genet. A prior knowledge as to which ramets are genotypically different is essential to establish a cross-pollination treatment. Ramets from three introduced populations ofB.umbellatusin western Canada (Hatzic Lake, British Columbia; Sturgeon River, Alberta; St. Andrews, Manitoba) were analyzed using isozyme and random amplified polymorphic DNA (RAPD) markers. Protein electrophoresis failed to reveal any difference in the banding patterns of 150 ramets using 16 enzyme systems. However, 5 of the 16 RAPD primers used were helpful in revealing polymorphism in terms of fragment amplifications. Three genets were differentiated, i.e., two from Hatzic Lake and one from both Sturgeon River and St. Andrews. SinceB.umbellatusis largely unexamined, our data also represent a preliminary contribution on the genetic organization of this colonizing clonal aquatic species.Keywords:Butomus umbellatus, isozyme, RAPD, clone, genet, ramet.

ISSN:0008-4026    

DOI:10.1139/b96-082

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The acid phosphatase activity in the soluble, membrane, and cell wall fractions fromHordeum vulgarein dry seeds and during seedling development was investigated. The acid phosphatase activities were also assayed in barley roots and coleoptiles at different developmental stages. Electrophoretic patterns of multiple acid phosphatases in seeds, endosperms and embryos, and growing roots and coleoptiles are shown. The enzyme activity shows a rapid decrease in both roots and coleoptiles during growth. Using nondenaturing polyacrylamide gel electrophoresis, multiple acid phosphatase forms were found in all the organs examined. However, no qualitative differences in the location of bands were observed between root and coleoptile extract at various stages of development. The coleoptile cell wall fraction showed an acid phosphatase form characterized by a very low electrophoretic mobility that was not found in the soluble fraction.Keywords: barley,Hordeum vulgareL., acid phosphatase, isoforms, seedlings growth.

ISSN:0008-4026    

DOI:10.1139/b96-083

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

We used long-term litter decomposition data to estimate final decomposition levels using an asymptotic function. The estimated final limit values for decomposition were compared with available chemical data for the different litter types. A total of 41 limit values were estimated from as many different decomposition studies, and 20 different litter types were incubated in eight different forest systems. The limit values estimated varied with litter type. They ranged from about 35 to about 100% decomposition and were linearly related to the initial litter concentrations of N, Mn, and Ca in the newly shed litter. For these three nutrients, there are causal relationships to lignin degradation and to the lignin-degrading microbial community. Using all available data, we made simple and multiple linear regressions and obtained a negative linear relationship between limit value and initial N concentration (;n = 41;p < 0.001). For needle litter alone, we obtained a better relationship (;n = 23;p < 0.001). Manganese concentrations in litter gave a positive relationship (;n = 25;p < 0.001), with a clear improvement when needle litter was tested for alone (;n = 16;p < 0.001). Calcium alone gave a barely significant relationship. When combining nutrients in multiple linear relationships we obtained highR2values, indicating that the models were good. Thus for all sites and litter types, N, Mn, and Ca combined gave anvalue of 0.640 withn = 25 (p < 0.001). All needle litters combined gave anof 0.745 (n = 16;p < 0.001). The significance of this finding is discussed.Keywords: litter decomposition, limit values, maximum decomposition, nitrogen, manganese, calcium.

ISSN:0008-4026    

DOI:10.1139/b96-084

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A variety of endophytic fungi were isolated from the branches of Norway spruce (Picea abies). We found that as internodes age, the composition of endophytic species gradually changes, both qualitatively and quantitatively. One of the dominating species,Tryblidiopsis pinastri, was most common in young internodes. In contrast, three other common species,Phialocephala scopiformis,Geniculosporium serpens, andTapesia livido-fusca, were most frequently isolated from old internodes.Mollisiaspp. were also common components of the endophytic flora of the Norway spruce in Sweden.Keywords:Picea abies,Tryblidiopsis pinastri,Phialocephala scopiformis,Geniculosporiumspp.,Tapesiaspp.,Mollisiaspp.

ISSN:0008-4026    

DOI:10.1139/b96-085

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

During a survey of the vesicular–arbuscular mycorrhizal (VAM) associations of forest herbs in a deciduous forest in the southern Laurentian mountains in Quebec, two liliaceous species,Clintonia borealisandMedeola virginiana, revealed very distinctive morphology. In both species, once the epidermis was penetrated, the fungus spread towards the centre of the root via intracellular hyphae until the innermost layer of the cortex was reached, at which point the fungus spread laterally and tangentially through the cortical cells adjacent to the endodermis via a series of banana-shaped projections (bobbits). These eventually differentiated into the arbuscules and the VAM might spread from this inner cortical layer back into the outer cortical layers. InC.borealis, the hyphae coiled in the cortex, and vesicles were formed in the upper cortical cells. InM.virginiana, no coiling took place, but extensive diverticulae were produced by the intracellular hyphae in the cortical cells, close to their point of exit, and vesicles were produced in the inner cortex as swellings from the bobbits. These two mycorrhizae have some similarities to one inColchicum autumnaledescribed by I. Gallaud (1905. Rev. Gen. Bot. 17).Keywords: vesicular–arbuscular mycorrhizae,Clintonia borealis,Medeola virginiana, Liliaceae, morphology.

ISSN:0008-4026    

DOI:10.1139/b96-086

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Low soil temperatures and water availability are thought to be major factors determining the distribution of tree species at the arctic tree line. A comparative study examined the response ofBetula papyrifera,Populus balsamifera, andPicea marianaseedlings to different soil temperatures and drought regimes in a growth chamber experiment. Morphological and ecophysiological responses (net assimilation rate, stomatal conductance to water vapour, and residual conductance) of these tree line tree species were measured and compared. Mean biomass accumulation of the deciduous species was greater than that ofPicea marianawith increasing soil temperatures. Root biomass showed an increase of 30% in the three species between the soil temperatures of 3 and 15 °C. Response of ecophysiological variables to increased soil temperature was greater inB.papyriferaandPopulus balsamiferathan inPicea mariana. In a second experiment, drought-preconditionedB.papyriferaandPopulus balsamiferaseedlings were subjected to a 6-day water-withholding treatment. Drought decreased shoot mass and increased the root to shoot ratio equally inB.papyriferaandPopulus balsamifera. Drought-preconditionedB.papyriferaandPopulus balsamiferaseedlings responded differently to the 6-day water-withholding treatment.Betula papyriferaused a water-conserving strategy and maintained low net assimilation rates and low water use after drought preconditioning, whereas inPopulus balsamiferagreater net assimilation rates were associated with drought preconditioning. These results are consistent with the distribution of these three tree species at the arctic tree line.Keywords:Picea mariana,Populus balsamifera,Betula papyrifera, drought preconditioning, soil temperature, arctic tree line.

ISSN:0008-4026    

DOI:10.1139/b96-087

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Nucleotide sequences of the nuclear, small-subunit ribosomal RNAs, as inferred from polymerase chain reaction amplified products, are introduced for representatives of the Dumontiaceae, Endocladiaceae, Halymeniaceae, and Kallymeniaceae of the order Cryptonemiales sensu Kylin, the Mychodeaceae, Phyllophoraceae, Schizymeniaceae, and Sebdeniaceae of the order Gigartinales sensu Kylin, and the Lomentariaceae and Rhodymeniaceae of the order Rhodymeniales. The new sequences are included in phylogenetic analyses incorporating previously published sequences from additional families of the orders Ahnfeltiales, Ceramiales, Gigartinales, Gracilariales, Palmariales, Plocamiales, and Rhodymeniales. We used the molecular data to test the validity of the taxonomic merger of the orders Gigartinales and Cryptonemiales that was proposed by G.T. Kraft and P.A. Robins in 1985. With only two exceptions (the families Halymeniaceae and Sebdeniaceae), phylogenetic analyses of the SSU data support a monophyletic origin for a combined Gigartinales–Cryptonemiales. We therefore propose the resurrection of a redefined Cryptonemiales to consist, at this time, of only the Halymeniaceae and Sebdeniaceae. Because virtually no elements of the original or recent definitions of the Cryptonemiales survive in the characterization of this taxon, we followed procedures allowed by the International Code of Botanical Nomenclature to designate it theHalymenialesord.nov. Analysis of molecular data further indicates that the Rhodymeniales is a monophyletic assemblage distinct from both the Gigartinales and Halymeniales; it should not be merged with the Gigartinales as is occasionally suggested.Keywords: Cryptonemiales, Gigartinales, Halymeniaceae, Halymeniales, phylogeny, Rhodophyta, Sebdeniaceae, small-subunit rRNA, systematics.

ISSN:0008-4026    

DOI:10.1139/b96-088

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

We investigated the association of environmental factors (temperature, photoperiod, host molting status) and fungal factors (isolate, dose, strain attenuation) with the production of conidia versus resting spores by the entomopathogenic fungusEntomophaga maimaigainfecting the larvae of the gypsy mothLymantria dispar. Fungal spores produced from individual cadavers of larvae killed byE.maimaigacan include conidia discharged from the cadaver surface, resting spores (azygospores) within the cadaver, or both spore types. The single factor having the greatest impact on the type of spore produced was host age; second instars virtually never contained resting spores, independent of temperature, while fifth instar cadavers contained resting spores more frequently at higher temperatures. However, there was increased conidiation at lower temperatures. Photoperiod was the only factor studied that did not significantly influence the type of spore produced. Resting spore production was negatively associated with the molting cycle; cadavers of those larvae that molted or exhibited premolt characteristics during the period between infection and death contained fewer resting spores. Increased fungal dose yielded more resting spores, as did extensive serial passage, which simultaneously caused a decrease in conidiation. Fungal isolates varied in the types of spores produced, with fewer cadavers of larvae killed by the least virulent isolate discharging conidia. Results from this study support the hypothesis that both the condition of the fungal pathogen as well as the environment surrounding it contribute to the types of spores produced.Keywords: fungal sporulation, resting spores, azygospores, Entomophthorales,Entomophaga maimaiga, biological control.

ISSN:0008-4026    

DOI:10.1139/b96-089

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Ninety-two isolates belonging toAspergillussect,flaviwere analyzed for double-stranded (ds) RNA via standard cellulose chromatography. Double-stranded RNA infection was detected in fungal isolates that had been in culture for long periods (5 of 26 were infected) and in those recently isolated (5 of 66 were infected). The number of dsRNA genetic elements differed among infected isolates and no two isolates contained identical dsRNAs on the basis of electrophoretic migration in agarose gels. Addition of micronutrients to culture media affected both the amount of dsRNA produced and the number of dsRNA genetic elements detected. Attempts to cure six fungal isolates of dsRNA by serial single conidial transfer, chlorate selection for nitrogen-metabolism mutants, and cycloheximide treatment, met with variable results. The frequency at which serial single conidial transfer and nitrogen-metabolism mutant (nit) selection successfully cured sixAspergillussect,flaviisolates varied from 11 to 100% and 0 to 100%, respectively. The cycloheximide treatment was effective at curing 40% of the dsRNA-infected isolates. Comparison of aflatoxin production prior to and after dsRNA curing indicated that infection by dsRNA did not influence aflatoxin production. However, aflatoxin production by two isolates (91-031B and 91-184G) was reduced by both single conidial transfer and induction ofnitmutants.Keywords: aflatoxin, cycloheximide, mycovirus, nitrogen-metabolism mutant.

ISSN:0008-4026    

DOI:10.1139/b96-090

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Sphagnummosses of three different species (S.capillifolium,S.magellanicum, andS.fallax) were allowed to dry in a controlled environment. The three species lost water at different rates, but after 11 days of exposure to drying atmosphere all were dry and unable to photosynthesize. The chlorophyllose cells of all three species showed signs of alteration, mainly membrane shrinkage. Upon rehydration, concentrations of photosynthetic pigments (chlorophyllato a greater extent than chlorophyllb) declined in tissues ofS.magellanicumand especially inS.fallax.Sphagnum capillifoliumandS.magellanicumresumed photosynthesis, although slowly, whereasS.fallaxdid not achieve a net carbon gain (most of its chlorophyllose cells were irreversibly damaged) after 7 days of rewetting. In the field, prolonged drought may alter the interspecific equilibria among coexistingSphagnumspecies possessing different degrees of desiccation-tolerance and especially different water-holding abilities.Keywords:Sphagnum, photosynthesis, ultrastructure, photosynthetic pigments, dehydration, rehydration.

ISSN:0008-4026    

DOI:10.1139/b96-091

出版商:NRC Research Press    

年代:1996

数据来源: NRC