摘要:

After the action of capsidiol on the hyphae ofPhytophthora capsici in vitro, observations with electron microscopy revealed alterations in the cell wall, in the plasmalemma, in the mitochondria, and in the Golgi system. Among other effects, phytoalexin stimulated the separation of the external cell wall layers, liberating a three-component filament. Such cytomorphological events were also recordedin situon sections, when the fungus parasitized the leaves ofCapsicum annuum. [Translated by the Journal]

ISSN:0008-4026    

DOI:10.1139/b86-089

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Germinated and attached seedlings of the phanerogamic parasiteConopholis americana(L.) Wallroth are described for the first time. The morphogenetic changes which characterize the transition from seedling to preflowering tubercle, as well as the anatomy of the mature tubercle, including endogenous floral buds, are also described.Conopholisseedlings were found attached only to mycorrhizal oak roots. The primary haustorium attached to and penetrated the fungal sheath, pushing aside epidermal and cortical cells of the host as it grew toward the host stele. Cells of the endophyte contacted host xylem and differentiated directly into reticulately thickened tracheary elements. Concomitantly a cambial are of parasite origin was established within the young tubercle, aligned with the vascular cambium of the host root. The cambium of the tubercle gave rise to xylem centripetally, which differentiated into tracheary elements juxtaposed to host secondary vessels, and cortical parenchyma centrifugally. Sieve elements could not be unequivocally demonstrated in seedlings or tubercles. Tissues and cell types of the parasite could be distinguished from those of the host by both morphological and histochemical criteria. The parasite to host transition zone was characterized by direct tracheary element connections and delimited by densely cytoplasmic parasite parenchyma cells that had greatly enlarged centrally located nuclei.

ISSN:0008-4026    

DOI:10.1139/b86-090

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Antisera were prepared from fruiting structures of aClavariasp. found growing in the vicinity ofRhododendronplants and from mycelium ofPezizella ericaegrown in culture. The antisera were used for the detection and differentiation of fungi in thin sections of roots ofRhododendronby an indirect immunocytochemical procedure using colloidal gold-labelled goat antirabbit immunoglobin G. Three distinct fungal types could be detected in roots: hyphae that reacted only with theClavariaantiserum; hyphae that reacted only with thePezizellaantiserum; and hyphae that did not react with either antiserum.

ISSN:0008-4026    

DOI:10.1139/b86-091

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

To document the aquatic flora of acid lakes in Kejimkujik National Park, N.S., the presence and abundance of aquatic macrophytes growing in water deeper than 3 dm were recorded in 20 lakes. Of the 45 species found, the most important wereSphagnum macrophyllum,Eriocaulon septangulare,Utricularia purpurea,Scirpus subterminalis,Pontederia cordata,Nuphar variegatum,Nymphaea odorata,Eleocharis acicularis,Sparganium angustifolium,Potamogeton confervoides,Lobelia dortmanna,Potamogeton epihydrus, andUtricularia vulgaris. To explore the relationship between floristic composition and water chemistry, information on 12 chemical variables and colour was related to species presence–absence using a nonparametric test based on relative neighbourhood graphs. Analyses of variance (ANOVAs) using chemical data and six groups suggested by a conditional clustering of the species presence–absence data demonstrated significant heterogeneity in Ca, pH, and HCO3. Furthermore, these three proved to be highly correlated. A canonical variate analysis of the six groups revealed one significant axis and separated the lakes into two major groups, characterized by relative acidity. An ANOVA of these two groups established that colour was also significant. There were fewer species in the more acidic (range 8–20, average 15) than in the less acidic lakes (range 15–32, average 22).

ISSN:0008-4026    

DOI:10.1139/b86-092

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Polymorphism for vernalization requirement has been observed within a population of wild oats,Avena fatuaL., grown under greenhouse conditions. One group of plants was early flowering ("spring type,"), whereas another was late flowering ("winter type,"). Vernalization of the winter type was obtained by germinating seeds for 2 weeks at 4 °C and resulted in shortening the time to heading by 50 days. However, this polymorphism was not observed in the field when plants germinated before mid-May. Hence, vernalization requirements did not appear to have any adverse or beneficial effects on time to heading and may be a neutral character in this population. Nevertheless, the frequency of the winter type in the population increased significantly over 6 years. Mechanisms are suggested to account for this phenomenon.

ISSN:0008-4026    

DOI:10.1139/b86-093

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Secondary forest succession involves large changes in the environment of the forest floor. Populations ofDanthonia spicataoccur in sites representing a 70-year span of succession following fire in the aspen–pine forests of northern lower Michigan. Five populations were studied from sites of ages 0, 26, 32, 44, and 69 years after fire. Four populations were in sites that were clear-cut and burned; one population occurred on the site of a natural burn. Environmental measurements in the sites revealed large differences with respect to light, soil water, and soil nutrients. We investigated the extent to which microhabitat selection was responsible for the persistence ofD.spicataacross the 70-year successional gradient. On three sites theD.spicatapopulations were in locations with a higher mean light level than the mean value for the site. During a 3-week period of no rain the plants in the four experimental burn sites were observed to occur in locations with a lower mean soil water potential than the mean for the site. It appears that microhabitat selection significantly altered the successional gradient as experienced by these populations ofD.spicata.

ISSN:0008-4026    

DOI:10.1139/b86-094

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Populations ofDanthonia spicatawere studied from sites of ages 0, 26, 32, 44, and 69 years after fire in the aspen–pine forests of northern lower Michigan. Along this gradient the environment changes from unshaded and dry to a shaded, moist pine and hardwood forest. Greenhouse treatments and transplant gardens were used to investigate the extent to which phenotypic flexibility and genetic adaptation were responsible for the persistence ofD.spicataacross this light and soil moisture gradient. With regard to phenotypic flexibility, we found that individual plants ofD.spicatacan grow and reproduce in light levels lower than those found at any site in the field. The populations were genetically distinct from each other but the differences were small relative to the range of phenotypic flexibility. Some populations and individuals performed better under high light conditions and all individuals performed equally poorly under low light conditions. A multivariate analysis suggests that genetic drift may have been more important than selection in differentiating the populations. Phenotypic flexibility was shown to be more important than genetic adaptation in explaining the persistence ofD.spicataalong the successional gradient.

ISSN:0008-4026    

DOI:10.1139/b86-095

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Seedlings of Scots pine (Pinus sylvestrisL.), with only primary needles, were frost hardened under a photoperiod of 8 h and a temperature of 4 °C for 6–9 weeks. The effects of frost hardening were studied on (i) the photosynthetic efficiency as defined by the quantum yield of CO2uptake under light-limiting conditions, (ii) the energy partitioning between the two photosystems as analyzed by 77 K fluorescence spectroscopy, and (iii) the distribution of solubilized chlorophyll–protein complexes after electrophoretic separation. It was found that frost hardening had no significant effects either on the photosynthetic quantum yield measured at 23–25 °C or on the energy distribution between the two photosystems. Despite these findings, frost hardening affected the chlorophyll organization so that the proportion of aggregated complexes such as chlorophyll–protein 1aand the dimeric form of light-harvesting chlorophyll–protein decreased. Frost hardening also decreased the amount of chlorophyll–proteinaand increased the amount of free, solubilized chlorophyll in the gel scan profile. From these results it is concluded that frost hardening affects the chemical interactions within the antennae organization of the photosynthetic apparatus but that these changes have no significant effects on the energy distribution between the two photosystems or on the photosynthetic efficiency as defined by the quantum yield for CO2uptake.

ISSN:0008-4026    

DOI:10.1139/b86-096

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Two cytotypes, one diploid (2n = 18) and one hexaploid (2n = 54), ofChenopodium albumL. were found in West Bengal. Morphological differences exist in the two cytotypes. Diploid plants were taller and had different flowering time, larger leaves, and lower saponin content in the seed as compared with the polyploid plants. Polyploidy is not associated with reduction of pollen fertility. A general uniformity in chromosome size, normal meiosis, bivalent formation, and regular seed setting in the polyploid suggest that homozygosity is a result of a continuous process of selection and evolution. Low saponin content and high protein content in the seed of the diploid may prove to be useful in breeding this variety as an alternative source of protein.

ISSN:0008-4026    

DOI:10.1139/b86-097

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Sporocarps of Basidiomycetes belonging to families containing some species known to form ectomycorrhizae were enumerated in 12 plots (16 × 16 m) subdivided into contiguous 2 × 2 m quadrats during the growing seasons of 1981 – 1983. Plots were distributed equally between homogeneous second-growth red spruce stands and heterogeneous northern hardwood stands in southeastern West Virginia. A few major species accounted for most of the abundance, while most species fruited rarely, but abundance and phenology varied broadly from year to year, apparently in response to rainfall and temperature. Fungal species composition, spatial frequency, and sporocarp density in the two forest types differed as would be expected in light of the symbiotic nature of the fungi and trees considered. Of 54 fungal species encountered over 3 years, 19 occurred exclusively in spruce plots, 27 occurred exclusively in hardwood plots, and 8 occurred in both forest types. In both forest types, approximately 40% of the species were Russulaceae. Species frequency and sporocarp abundance were greater in spruce plots than in hardwood plots. The Shannon–Wiener index, the dominance–diversity curve, the species–area curve, and ordination confirmed that fungal species richness, equitability, and diversity were greater in the mixed-hardwood plots, which hosted many rare fungal species, than in the single-species coniferous plots, which were dominated by a few ubiquitous fungal species.

ISSN:0008-4026    

DOI:10.1139/b86-098

出版商:NRC Research Press    

年代:1986

数据来源: NRC