摘要:

Phytoplankton samples from 130 stations in Hudson Bay taken during summer 1975 were examined. Diatoms formed the largest group of phytoplankton comprising 27 genera and 59 species, 24 of which are not previously recorded from Hudson Bay. Twelve genera and 45 species of dinoflagellates were identified of which 33 have not been previously reported from the Bay.Various patterns of distribution were observed; some species were only found inshore, while others were distributed throughout the Bay with the exception of the low salinity waters of the southwest coast. Highest cell counts were found inshore; diatoms reached 200 000 cells per litre around the Belcher Islands. Dinoflagellates reached 125 000 cells per litre south of Mansel Island, and exceeded 60 000 cells per litre in the Chesterfield Plume and along the southwest coast. Thus certain areas of Hudson Bay have much higher phytoplankton standing crops than previously believed, often greatly exceeding counts from Foxe Channel and Hudson Strait. The lowest diversity indices of diatoms, dinoflagellates, and diatoms and dinoflagellates combined, were observed at lower salinities along the southwest coast. The diversity index of diatoms and dinoflagellates combined was otherwise high throughout the Bay (> 3) and was highest in the Coats and Mansel islands area.

ISSN:0008-4026    

DOI:10.1139/b81-240

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

During the development ofPolypodium vulgareL. mitotic indices and duration of cell cycles have been determined for two apical zones of the meristem. In the young state, the mitotic activity of the meristem is high and uniform; the cell cycles of the axial and lateral zones are very similar. At the beginning of the adult state, the axial zone is characterized by a low mitotic index and a cell cycle which is twice that of the lateral zone.

ISSN:0008-4026    

DOI:10.1139/b81-241

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A copper-tolerant isolate ofScenedesmusfrom Sudbury, Ontario, cultured in medium completely lacking copper, lost its ability to grow at high copper concentrations after 10 generations. The change was sudden in onset and relatively rapid. The algae had previously been maintained on medium with micronutrient levels of copper and had retained their tolerance over 7 years of laboratory culture.The tolerance of the copper depleted cells to nickel and cobalt also decreased. Their tolerance to cadmium and silver was unchanged by copper depletion. The situation for zinc tolerance was less clear, but there was no significant decrease over the range tested.When copper-depleted cells were cultured in complete medium with micronutrient levels of copper, copper tolerance increased after four divisions and recovered to the original state after eight divisions. Plate assays indicated that all of the cells in the culture were recovering i.e., this was not a reselection of a few tolerant cells.The results are discussed in terms of possible tolerance mechanisms, and their implications for the occurrence of multiple or cotolerance.

ISSN:0008-4026    

DOI:10.1139/b81-242

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Most of the modern vascular plants form either endo- or ecto-mycorrhizal symbioses with fungi. Few plants are not mycotrophic.Each condition has probably arisen in different groups of plants, at different times during their evolution, and with different consequences: the origin of vascular plants, the evolution of arborescent and herbaceous habits, and the differences in composition of forests are speculatively linked with mycotrophism.

ISSN:0008-4026    

DOI:10.1139/b81-243

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Details of development and the phenology of postdormancy cone-bud development, microsporogenesis, pollen development, and pollination were similar forPinus contortavar.contortaand var.latifoliagrowing near Victoria, B.C., but comparable stages of development for var.latifoliaoccurred about 1 month later near Prince George, B.C. Several developmental aspects were found which affect the reproductive potential of the species. Only 25% of the ovuliferous scales, mostly in the distal part of the cone, bear fertile ovules. Secretions formed on the ovules and micropylar arms which caused pollen to adhere to these surfaces. Pollination is by means of pollination drops which began to be exuded from the ovules about 2 weeks after the conelets began to emerge from their bud scales. Pollination drops were present within each conelet for 2 to 4 days. At that time conelets were most widely open. Pollination drops were then withdrawn as ovuliferous scales enlarged and sealed the conelets. Pollination drop exudation and withdrawal were affected by humidity and water stress within the tree. Cells lining the micropylar canal enlarged and sealed the micropyle after the conelet closed. Pollen settled into a pollen chamber in the nucellus tip where it germinated about 2 months after pollination. Ovules lacking germinating pollen aborted after megasporogenesis and before free nuclear division began. If many ovules aborted within a conelet, the conelet aborted before winter dormancy. Ovules began free nuclear female gametophyte development and pollen tubes extended into the nucellus before conelets stopped developing in mid-August.

ISSN:0008-4026    

DOI:10.1139/b81-244

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A comparison of life history traits in four taxa of theEchinochloa crus-gallicomplex (barnyard grass) which differ in colonizing ability and weediness was made under various environmental conditions. The taxa were the alien var.crus-galli, a cosmopolitan weed; var.oryzicola, a crop-mimic restricted to rice fields; var.frumentacea, a crop domesticate; andE.muricata, a native of wetland habitats. Populations studied were from the Central Valley of California where the four taxa are sympatric but ecologically differentiated. All comparisons were made under uniform glasshouse conditions to isolate the genetic component of life history variation. Measurements of the patterns of dry weight allocation, time to flowering, reproductive effort, and seed production were made on individuals grown during different periods of the year under "stress" and "nonstress" conditions utilizing randomized multi-harvest designs.Developmental plasticity in allocation patterns and reproductive phenology occurred in all taxa in response to seasonality and nutrient stress although there were significant differences among taxa in the form of the response. Individuals germinating in August yielded less total biomass and allocated a smaller proportion to roots and a larger proportion to secondary tillers and seed than individuals germinating in April. In all taxa, exceptE.crus-gallivar.frumentacea, a delay in flowering under long days resulted in larger vegetative biomass, lower reproductive effort, and where nutrients were limiting, inhibition of secondary tillers. Nutrient stress resulted in a delay in flowering, increased senescence rates, and a reduction in total biomass and reproductive effort. Although each taxon displayed a wide range of tactics, certain differences in life history strategy among the taxa were maintained. In all regimesE.crus-gallivar.crus-galliflowered earlier, and exhibited a greater seed production and reproductive effort than var.oryzicola. In general,E.crus-gallivar.frumentaceaandE.muricatawere intermediate in behaviour.Interpopulation variability in the life history traits ofE.crus-gallivar.crus-galliandE.muricatawas measured in a single-harvest, completely randomized design using 10 populations of each taxon. Significant interpopulation variation was recorded within taxa in tiller height and number, aboveground vegetative biomass, time to anthesis, reproductive biomass, harvest index, seed production, and seed weight. Averaged over 10 populations,E.crus-gallivar.crus-galliwas taller during vegetative growth, flowered more rapidly, allocated a greater proportion of aboveground biomass to reproduction, and produced a greater number of seeds thanE.muricata.Variation in life history parameters among barnyard grass taxa may explain differences in colonizing potential. In particular, the failure ofE.muricataandE.crus-gallivar.oryzicolato colonize open, seasonally moist sites in California whereE.crus-gallivar.crus-galliflourishes, may be due to their inability to reach reproductive maturity before the onset of summer drought.

ISSN:0008-4026    

DOI:10.1139/b81-245

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Spirogyromyces vermicolais described as a new genus and species inhabiting the gut of free-living nematodes. The spores are ingested and attach to the gut wall of the host. A stout, helicoid, septate hypha grows down the gut and produces one or several helicoid branches. One or more filiform spores arise from the vicinity of each septum and coil around the main axis or its branches. The mature thallus can fill the gut of the nematode with primary (main axis), secondary (branches), and tertiary (spores) coils of striking symmetry. Spores break away from the thallus and are defecated through the anal orifice to the exterior where they are eventually ingested to initiate infection.

ISSN:0008-4026    

DOI:10.1139/b81-246

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Wood and soil samples from Churchill and Great Whale (Hudson Bay) were surveyed or baited for recovery of marine fungi. A total of 14 ascomycetes, 7 fungi imperfecti, and 13 zoosporic fungi are reported.Amylocarpus encephaloides,Cephalosporiumsp.,Corollospora comata,Dictysporium pelagicum,Haligena amicta,Haligena elaterophora,Halosphaeria maritima,H.mediosetigera,H.quadriremis,H.stellata,Herpotrichiella ciliomaris,Nais inornata,Papulospora halima,Phialophorasp.,Phomasp.,Schizochytrium aggregatum,Thraustochytrium aggregatum,T.multirudimentale,T.pachydermum,T.roseum,Trichocladium achrasporum, andZalerion variumare recorded for the first time from arctic marine sites. Each species is discussed in terms of morphological features, taxonomic deposition, and ecological considerations.

ISSN:0008-4026    

DOI:10.1139/b81-247

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Vessel-length distributions in some trees, shrubs, and a vine have been calculated from measurements of particle penetration and of air-volume flow through the xylem. In shrubs and diffuse-porous species, longest vessels were about 1 m long, but most of them were much shorter, the largest percentage in the 0–10 cm length class. In the two ring-porous species investigated (Quercus rubraandFraxinus americana), the longest vessels often were as long as the tree's stem, but most of them were much shorter. In the grapevine (Vitis labrusca) which has large-diameter vessels (ca. 300 μm) a small percentage of the vessels was 8 m, but most of them were less than 5 m long. In a given species, lengths of the longest vessel were quite variable, but the distribution of the short lengths was more constant. In general, vessel lengths are correlated with vessel diameters: wide vessels are longer. Even in diffuse-porous species, the slightly narrower latewood vessels are somewhat shorter than the wider early wood vessels. The method is a simplified version of that described by Skene and Balodis, but using a programmable desk calculator. It works best with diffuse-porous species in which vessels are randomly distributed in the stem, and less well in species with wide vessels, because as vessels reach the length of the stem itself, they cannot be randomly distributed.

ISSN:0008-4026    

DOI:10.1139/b81-248

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Chenopodium bonus-henricusachenes have poor germination whatever the temperature; this phenomenon is reinforced with increasing elevation of seed harvest. Since the excised embryo is never dormant, germination of intact seeds is prevented by the seed coat. The seed coat thickens and contains more polyphenols with increasing elevation. This process appears to be responsible for the reduced permeability of the seed coat. High germination temperatures reduce the gas solubility in water and, at the same time, increase polyphenol oxidation in the seed coat. The embryos of seeds collected at low elevation thus receive a reduced O2flux. When high temperature is applied to seeds from high elevation, the O2flux is drastically reduced because of the thicker seed coat and increased levels of oxidizable polyphenols.There is a high correlation between germination and the mean of the average daily temperature for the 30 days preceding harvest, high temperature prior to harvest being correlated with high germination.Progenies of plants transferred from high to low elevation (and the inverse) show the direct influence of the new environment on the seed coat inhibition of germination.

ISSN:0008-4026    

DOI:10.1139/b81-249

出版商:NRC Research Press    

年代:1981

数据来源: NRC