摘要:

Fossil cuticles were extracted from leaves attributed toCordaites principalis(Germar) Geinitz (Cordaitales) that were collected from Upper Carboniferous strata in Nova Scotia (Sydney and Stellarton sub-basins) and in Newfoundland (Bay St. George sub-basin). The quality of the cuticular preservation is directly related to the thermal maturity and the grain size and angularity of sediments entombing the fossil leaves. Detailed transmitted light and scanning electron microscopy of the cuticles revealed that five distinct cuticular morphotypes could be recognized, demonstrating the variability in epidermal morphology of leaves belonging to one taxon. Two morphotypes show dissimilar and discrete epidermal characteristics, whereas three morphotypes form, more or less, a morphological continuum. Comparison with cuticles from Euramerican and Angaran floral provinces suggests that only one morphotype is in common with cuticles described from Europe, while four morphotypes are new for the Carboniferous.Key words: cuticle,Cordaites, Carboniferous, Canada.

ISSN:0008-4026    

DOI:10.1139/b00-010

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Effects of clear-cutting on the ectomycorrhizal (EM) fungus community in aPinus contortaDougl. ex Loud. forest near Yellowstone National Park, Wyoming, U.S.A., were assessed using molecular techniques. Samples were taken by soil core in both undisturbed and clear-cut sites by randomized block design. Species overlap was compared between clear-cut and undisturbed sites and ascomycete-basidiomycete ratio was determined, using PCR-RFLP methods. Fifty species of EM fungi were detected in the clear-cut sites, the most common beingCenococcum geophilumFr.,Suillussp., a member of the suilloid group, a Russulaceae species, and a Thelephoraceae species. Sixty-six species were detected in the undisturbed sites, which were dominated by a Suilloid species, a Tricholomataceae species,Cortinariussp., andCenococcum geophilum. Species composition in the clear-cut sites differed significantly from that in the undisturbed sites (P= 0.0001). However, 9 of the 14 species most commonly found in the clear-cut sites were also found in the undisturbed sites, but in much lower abundance, while species rank curves of both stand types mirrored each other. There were no significant differences in species richness, root-tip abundance, or ascomycete-basidiomycete ratio between the clear-cut and undisturbed sites. However, species richness was lower in the clear-cut sites than in the undisturbed sites. An overall loss of species richness after clear-cutting and significant changes in species composition indicate that clear-cutting can negatively alter the EM fungal community, and this may have profound effects on ecosystem function.Key words: ectomycorrhizae, community structure, clear-cutting, molecular techniques.

ISSN:0008-4026    

DOI:10.1139/b99-171

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Over a period of 5 years, monthly samples of water-borne conidia were collected at two sites, bridge and mouth, in Catamaran Brook, a third-order salmon stream in New Brunswick, Canada. Conidial concentrations and number of aquatic hyphomycete species peaked in October; a smaller peak was generally observed in June. Evenness was lowest in October. The number of species in the five 12-month periods varied between 46 and 56 (bridge) and 41 and 47 (mouth); over the entire period, 75 (bridge) and 70 (mouth) species were identified. Of these, 30 and 26, respectively, occurred in every period. The average ranks of the 12 dominant species (based on yearly conidium production) could be divided into two groups of no significant differences: ranks 1-7 (bridge) and 1-10 (mouth), respectively, and 2-12 (both sites). Monthly abundances of the 12 top-ranked species were examined for correlations. Significant correlations found in periods measuring between 1 and 4 years were rarely validated in subsequent periods.Key words: aquatic hyphomycetes, stream spora, annual and seasonal periodicity.

ISSN:0008-4026    

DOI:10.1139/b99-172

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Apoplastic &bgr;-1,3 glucanases (G1, G2) ofArachis hypogaeaL. (peanut) leaves treated with glucan have been partially purified by ammonium sulphate precipitation, sephadex G-100, CM-Sephadex, DEAE-Sephadex chromatography, and preparative native PAGE electrophoretic techniques. The pI values of purified enzymes G1 and G2 were near 8 and 4, respectively. The apparent molecular masses of purified glucanases G1 and G2 from glucan-treated peanut leaves were 36 and 34 kDa, respectively. Both isoforms (G1 and G2) showed their pH optimum of 5.0 and temperature optimum of 40°C. The partially purified enzymes hydrolysed laminarin better than other substrates and inhibited uredospore germination ofPuccinia arachidis. Both isoforms (G1 and G2) inhibited spore germination of some biocontrol agents such asAcremonium obclavatumW. Gams,Myrothecium verrucaria(Alb. Schw.) Ditmer,Fusarium solani(Mart.) Sacc., andTrichoderma harzianumRifai.Key words:Acremonium obclavatum,Arachis hypogaea, &bgr;-1,3 glucanase, glucan, inhibition,Puccinia arachidis

ISSN:0008-4026    

DOI:10.1139/b99-174

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Because of the enzymatic make-up ofStropharia, a cultivated and edible mushroom, it is capable of using agricultural wastes as substrates for growth. Different substrates and methods of preparation are compared in order to improve the resistance of the mushroom to fungal contamination by reducing soluble carbon and nitrogen content. The substrates (wheat straw, corn stalk, or wastes from pea plants) were soaked at various temperatures and durations in order to eliminate soluble nutrients. High temperatures are more efficient for a rapid depletion of free nitrogen compounds. The best substrate used for the first time in mushroom cultivation was the agricultural waste fromPisum. Because of its naturally high content of soluble nutrients, this substrate needs to be soaked in hot water to reduce contaminations. Yields ofStropharia(220 g/kg) are higher and more regular than those obtained on conventional substrate (straw). On corn stalk, a high contamination rate was found, as well as relatively poor yields.Key words: mushroom,Stropharia, substrate, waste, yield, fungal contamination.

ISSN:0008-4026    

DOI:10.1139/b99-175

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We assessed the size and composition of the seed bank in 31 plots representing a range of habitats within an old-growth, temperate deciduous forest at Mont St. Hilaire, Québec, Canada. We identified 49 taxa in the seed bank, with an average of 40 species·m-2and a median density of 1218 seeds·m-2. The most frequent seeds were species ofCarexandRubus,Diervilla lonicera, andEupatorium rugosum, while seeds ofCarexwere the most numerous overall. Of the 12 species in the seed bank not found in the forest, 11 were found growing on the developed landscape surrounding this 10-km2forest fragment. These nonforest species were numerically only a minor component of the forest seed bank. Vernal herbs were not in the seed bank, and there were only a few tree species. Variation in seed bank richness among habitats was correlated positively with canopy cover, soil moisture, and soil nutrients, but not with the seed bank density or total number of species in the aboveground vegetation. Seed bank density increased with plot soil moisture. Woody species predominated in the seed bank of plots with richer soils, deeper litter, and more closed canopies. Herbaceous species predominated in the seed bank of plots with more open canopies, more mesic water regimes, and greater species richness in the aboveground vegetation. Contrary to earlier results suggesting forest seed banks primarily include shade-intolerant species associated with canopy disturbance or secondary succession, the seed bank in this old-growth, primary forest contains many shade-tolerant forest species.Key words: seed bank, old-growth forest, primary forest, temperate deciduous forest, habitat diversity, seed dispersal

ISSN:0008-4026    

DOI:10.1139/b99-176

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Approximately 86 specimens ofBathurstia denticulataHueber were collected from upper Bathurst Island and lower Stuart Bay beds of Bathurst Island, Canadian Arctic Archipelago.Bathurstiawas a component of a zosterophyll-dominated flora of Pragian age (Lower Devonian) that existed at low paleolatitudes in northern Canada. The large collection of well-preserved materials permits reconstruction of the plant as a robust scrambler of about 30 cm in height. Stems bear short, shelf-like emergences in two rows, and branch isotomously, although sparsely. Rooting organs, representing some of the oldest known for land plants, arise from the main aerial axes, although they are also associated with small, subordinate shoots interpreted as plantlets. Numerous specimens are fertile, with sporangia borne in dense terminal spikes. Spikes include two rows of overlapping, discoid sporangia. Isospores are round and featureless, and assignable to the genusCalamospora. WhileBathurstiaapparently originated from among the isotomously branching bilaterally symmetrical zosterophylls, the phylogenetic relationships ofBathurstiato known taxa is unclear, although some resemblance toSerrulacaulis,Barinophytaceae,and the Gosslingiaceae can be documented.Bathurstia denticulatais now one of the best known of early land plants, and contributes significantly to our understanding of zosterophylls and their role in Early Devonian vegetation.Key words:Bathurstia, zosterophyll, Devonian, Canada, Arctic, evolution.

ISSN:0008-4026    

DOI:10.1139/b99-179

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The pollen of all six species ofLyperia(Scrophulariaceae, tribe Manuleae) was investigated by light microscopy and scanning electron microscopy of whole and fractured grains. Pollen grains inLyperia antirrhinoides(L.f.) Hilliard,LyperiaformosaHilliard,Lyperia tenuifloraBenth., andLyperia violacea(Jarosz) Benth. differed from those inLyperiatristis(L.f.) Benth. andLyperia lychnidea(L.) Druce in number and length of colpi, sculpturing of the colpus margin, reduction of apocolpial lumina size, reduction of exine thickness toward the colpi, ornamentation of the outer nexine surface, arrangement of columellae beneath the muri, direction of cross-sectional compression in elliptical muri, and relative dimensions of the muri and columellae. Pollen grains from 50 representative species of the putatively related generaSuteraandJamesbritteniawere also examined. Correlations among quantitative pollen characters of tribe Manuleae and theSuteracomplex were investigated by principal components analysis. Morphological similarities in the pollen ofLyperia,genera of theSuteracomplex, and other Manuleae were summarized by ordination of the principal components data and (or) cluster analysis. The pollen grains ofL. lychnideaandL. tristisdiffered from those of otherLyperiaand stood apart from those ofJamesbrittenia,Sutera, and all other Manuleae. Pollen morphology inSuteraandJamesbritteniaintergrades with that in tricolporate species ofLyperia.Key words: pollen morphology, Scrophulariaceae,Lyperia,Jamesbrittenia,Sutera.

ISSN:0008-4026    

DOI:10.1139/b99-180

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Six rhododendron species grow wild in Hong Kong:Rhododendron farreraeTate andRhododendron simsiiPlanch. are common and widespread,Rhododendron moulmainenseHook. f. is restricted, andRhododendron championiaeHook. f.,Rhododendron hongkongenseHutch., andRhododendron simiarumHance are rare. The length and timing of the flowering period varied between species, but peak flowering for all was between late February and early May, when weather is variable and unpredictable. All species were more or less self-sterile, had sucrose-dominated nectar, and were visited by diverse insects, of whichApis cerana,Bombus eximius, andXylocopaspp. are the major pollinators. Seeds of all species, exceptR. simiarum, had a light requirement for germination. There were large differences between species in the pollen/ovule ratio (176-1343), daily nectar production (0.9-38.7 µL per flower), large bee visits (0.35-4.28 per flower per 100 h) and total visits (0.92-14.53), mean seed production per flower (2-135) and per plant (100 - 14 800), and mean seed weight (0.11-0.45 mg). The large-bee visitation rate was significantly correlated across species with mean daily nectar production and mean seed set. The two common species had the smallest flowers, lowest nectar production, lowest pollen/ovule ratios, fewest large bee visitors, and produced fewest seeds.Key words: breeding system, China, pollination, rarity,Rhododendron, seeds.

ISSN:0008-4026    

DOI:10.1139/b99-181

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Researchers have often assumed that the reproductive success of a plant increases with flower production. However, if predispersal seed predation also increases with flower production, this may counteract the increase in reproductive success expected with such increased flower production. To investigate this, we examined the effect of flower number and predispersal seed predation on seed production in two field populations ofCirsium purpuratum(Maxim.) Matsum. At both sites, the proportion of seeds or heads preyed upon per plant increased with the number of flowers (florets or heads) on each plant, while the proportion of mature seeds per plant was independent of flower number per plant. Based on these results, we predicted that an increased level of seed predation at the population level would reduce the annual flower production of each plant. The observed pattern of flower production supported this prediction. Our results suggest that increased flower production may not always improve plant reproductive success under the influence of predispersal seed predation.Key words: plant reprodutive success, predispersal seed predation,Cirsium purpuratum, flower production, plant-animal interaction.

ISSN:0008-4026    

DOI:10.1139/b99-182

出版商:NRC Research Press    

年代:2000

数据来源: NRC