摘要:

Abies grandis,Taxus brevifolia,Thuja plicata, or any combination of these may dominate old-growth mesic forests of the Bitterroot Canyons, western Montana. Similar sites need not develop similar, relatively stable forests. This is shown by (i) anomalous distributional patterns of tree species, (ii) broad overlap of tree species abundance in environmental space (shown by ordination and discriminant analysis of stands in environmental space), and (iii) weak or undetectable correspondence of species × stand and site factor × stand matrices (multiple regressions of compositional dissimilarity against environmental differences; also, canonical correlation and Mantel tests). Since a one-to-one mapping from site factors to species composition in old-growth vegetation is a fundamental tenet for applications of the climax concept, caution is warranted where the concept is to be applied within a narrow range of site factors or to insular communities.

ISSN:0008-4026    

DOI:10.1139/b85-043

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Both shade-tolerant and shade-intolerant tree species may dominate young stands in canyon-bottom forests of the Bitterroot Range. Subsequent dynamics depend on growth characteristics of the colonizing species. Thus, much of the compositional variation arises at stand establishment (initial floristic composition) rather than through a replacement process (relay floristics).Taxus brevifolia, however, may require shelter from other species for establishment. Vertical similarity increases with stand age towards a maximum value of about 75%. Although the importance ofTaxus brevifoliaandThuja plicatatends to increase with stand age, convergence on a common climax composition is thwarted by insularity of the canyon bottoms and an average fire cycle (60 years) that is shorter than the normal longevity (120-140 years) of the shortest lived major tree species (Pinus conforta).

ISSN:0008-4026    

DOI:10.1139/b85-044

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Evidence from published work is first reviewed to show that cationic, neutral, and anionic complexes of the uranyl ion are available to plants growing in uranium-enriched environments. The results of a study on the uptake of uranyl ions by the lichenCladonia rangiferinaL. Wigg. are then presented. Uptake was examined from three different uranyl solutions each predominantly containing a single species: namely, the cation(in distilled water), the neutral 1:1 complex with phthalate (UO2L), and the anionic complex of oxalate. Uptake decreased along the chemical speciation series: cationneutral speciesanion. Maximum observable capacities for this series were, respectively, 49, 17, and 1.6 μmol/g for 1-g samples in 100 mL containing 840 μmol of total uranium. Theuptake curve was observed to be monophasic, while biphasic patterns appeared to apply for the phthalate and oxalate buffers. Heat-killed tissues showed marginally higher uptake capacities than live material.

ISSN:0008-4026    

DOI:10.1139/b85-045

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The toxicity of the uranyl ion to the lichenCladonia rangiferina(L.) Wigg. was shown to be strongly dependent on chemical speciation. Photosynthetic measurements indicated that the anionic complex of oxalatewas more toxic than the uncomplexed cation. No detrimental response could be assigned to the neutral phthalate complex (UO2L). Toxicity was also affected by the physiological condition of the lichen material. Samples exhibiting low photosynthetic levels typical for winter-collected material were damaged to a greater degree. Neither the cationic nor anionic species induced K+loss from the lichen and the small release induced by the neutral species of the uranyl ion in phthalate buffer reflects a reduction in membrane integrity resulting from Ca2+depletion. The effects of the uranyl ion and of the buffers used on Ca2+displacement from lichen samples are discussed. Uranium uptake induced a reduction in total14C fixation rates, a decrease in the proportion of radioactivity in the ethanol-soluble fraction, and an increase in the ethanol-insoluble fraction. These effects are ascribed to interference with bicarbonate transfer into the algal cell and the blocking of carbohydrate transport from the algal partner.

ISSN:0008-4026    

DOI:10.1139/b85-046

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Attempts were made to hybridizePalmaria palmata(L.) O. Kuntze from the North Atlantic Ocean withPalmaria palmataf.mollis(Setchell and Gardner) Guiry from the eastern North Pacific Ocean. No hybrids were obtained in reciprocal crosses, although fertilization was readily achieved for control crosses within each taxon. The number and placement of carpogonia on well-developed female gametophytes (disc diameter, 100–150 μm) was different for the two taxa. The Atlantic plants had comparatively few carpogonia (1–10), which were always found at the center of the holdfast disc or on young upright fronds, whereas the Pacific plants had many carpogonia (15–60), which were most commonly located away from the centermost portion of the disc and were never observed on developing fronds. The two taxa also differed in their susceptibility to a small parasitic Oomycete of the genusPeterseniaSparrow, which is pathogenic for f.mollisbut did not infect the Atlantic plants. Cytological examination revealed that f.mollishasn = 21 chromosomes, the same asP.palmatafrom the north Atlantic Ocean. In view of the genetic isolation between the two forms,P.palmataf.mollisis raised to specific status asPalmaria mollis(Setchell & Gardner) van der Meer & Bird.

ISSN:0008-4026    

DOI:10.1139/b85-047

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Specimens ofPalmaria mollis(Setchell and Gardner) van der Meer and Bird collected from Vancouver Island, Canada, were found to harbour a pathogenic fungal parasite. When infected fronds were put into culture, the algal thallus became completely covered with small white lesions. These were most concentrated in young tissue and soon killed the apices of the fronds. The parasite completed approximately one infection cycle per week at 10 °C. It died at temperatures near 15 °C, even though the host remained healthy at 20 °C. The parasite was identified as a species ofPetersenia(Oomycetes). It most resembledP.lobata(H. E. Petersen) Sparrow but differed sufficiently in detail to consider it a new species,Petersenia palmariae. The new species does not infectCeramium rubrum(Hudson) C. Agardh which serves as host for bothP.lobataandP.pollagaster, the only other members of the genus known to parasitize marine algae. Nor does it infectPalmaria palmata(L.) O. Kuntze, a species related to the host on which it was discovered, which suggestsPetersenia palmariaemay be host specific.

ISSN:0008-4026    

DOI:10.1139/b85-048

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Invasion ofPalmaria mollisby the marine oomycetePetersenia palmariaebegins with penetration of the cell wall and then the lumen of an outer cortex cell. The fungus in its vegetative phase lacks a wall but is separated from the host cytoplasm by the invaginated plasmalemmaof the host cell. By promoting fusion of host cells or by the dissolution of the host cells' pit plugs, the fungus is able to use a symplastic route to invade cells deep in the cortex and medulla of the host. In the process, a compound confluent host cell lumen is created. The deposition of a thick wall around the lobed fungal cell marks the beginning of holocarpic sporangium formation and is followed by great proliferation of the parasite's nuclei and concomitant diminution of nuclear and nucleolar size. The cytoplasm becomes parietal when a large central vacuole develops. Mastigonemes are formed in dilated endoplasmic reticulum, mitochondria become associated with nuclei, and cleavage begins. Flagella begin to form on paired basal bodies before cleavage is complete. Following a period of motility, zoospores retract and then resorb their flagella. The naked spores develop walls and the basal bodies persist as centrioles.

ISSN:0008-4026    

DOI:10.1139/b85-049

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

An apparently new dark synnematous hyphomycete with apically appendaged phragmoconidia is described as a second species of the genusConicomyces. Facets of its ontogeny and biology are discussed.

ISSN:0008-4026    

DOI:10.1139/b85-050

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Five species congeneric withMorrisographium persicae(Schw.) Illman & G. P. White (=M.pilosum(Earle) Morelet) are transferred; viz.,Arthrobotryum fusisporiumA.L. Sm.,Sphaeronaema boudieriCh. Richon,Sphaeronaema hispidulumEll. non Cda.,Cornularia ulmicolaEll. & Ev., andPhragmographium ulmiMorris. Comparative studies of the accepted species are presented and a key to them is provided. Certain excluded taxa are discussed.

ISSN:0008-4026    

DOI:10.1139/b85-051

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

An undescribed species ofPapulaspora,P. asperasp. nov., has been isolated from decaying leaves and hibernacula of the pondweedsPotamogeton crispusandP.nodosuscollected in northern California. It is characterized by production of abundant numbers of small, black bulbils in which the cells are relatively uniform with respect to size, shape, and pigmentation. The bulbil primordium is a chain of swollen cells which are usually intercalary but which are sometimes terminal.

ISSN:0008-4026    

DOI:10.1139/b85-052

出版商:NRC Research Press    

年代:1985

数据来源: NRC