摘要:

The response of black and white spruce and jack pine to slow and rapid induction of moisture stress was evaluated during soil drying and exposure to liquid cultures containing polyethylene glycol 8000. Marked changes in water, osmotic, and pressure potentials were observed in all three species, but water potentials were the most sensitive indicators of moisture stress. Osmotic potentials were sensitive to mild stress in polyethylene glycol (−400 kPa), but they held relatively steady at higher stress intensities (−800 to −1600 kPa). Large decreases in osmotic potential were recorded in white spruce and jack pine during severe drying stress late in the drought period and these changes were accompanied by large decrements in water and pressure potentials. Significant changes in osmotic potential were not observed in black spruce prior to seedling death. Losses in pressure potential were only observed at −1600 kPa of polyethylene glycol stress, although wilting in young tissue was apparent at lower stress intensities. Pressure potentials of plants in the soil-drying test fell well below those recorded in the polyethylene glycol study. The highest resistance to loss of turgor and the maximum adjustment to moisture stress were observed in white spruce. Shoot growth and transpiration declined in the three conifers at relatively low stress intensities. Total chlorophyll and the chlorophyll stability index decreased during drought, but the differences recorded among species were not clearly related to observed differences in drought tolerance. Cation concentrations did not change during stress.

ISSN:0008-4026    

DOI:10.1139/b85-162

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Two hybridomas that secrete antibodies specific for a phytotoxic glycopeptide fromOphiostoma ulmi(Buism.) Nannf. were produced by fusing spleen cells of mice immunized with the purified toxin and the Sp2-0/Ag14 mouse myeloma cell line. Specificity of these antibodies was first demonstrated by an enzyme-linked immunosorbent assay (ELISA), then by immunoblotting on nitrocellulose membrane after sodium dodecyl sulfate – polyacrylamide gel electrophoresis of the glycopeptide. Both clones produced antibodies of IgM class as determined by immunodiffusion. These monoclonal antibodies were utilized to detect and localize the toxic glycopeptide in pathogen cells and infected host tissues by immunohistochemical and immunocytochemical techniques.

ISSN:0008-4026    

DOI:10.1139/b85-163

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Monoclonal antibodies against a phytotoxic glycopeptide fromOphiostoma ulmi(Buism.) Nannf., the Dutch elm disease pathogen, were used in a postembedding protein A – gold labeling technique to localize this toxin in experimentally infected tissues of young elm seedlings. Significant labeling was observed over pit membranes, over the innermost wall layer (protective layer) of paratracheal parenchyma cells, and over the intercellular spaces and, adjacently, the middle lamella. Host secondary walls, cytoplasm, and various organelles, except regions of amyloplastids, were free of labeling. From day 1 to day 4 after inoculation an intensification of the labeling reaction was noted that corresponded to an increase in the disease symptoms. This specific and sensitive technique has thus proved to be highly suitable for thein situidentification of antigenic macromolecules in diseased elm tissues. The classification of the toxic glycopeptide among the group of vivotoxins is discussed.

ISSN:0008-4026    

DOI:10.1139/b85-164

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Seven different species from three genera of common vesicular–arbuscular mycorrhizal (VAM) fungi differed in the extent of their root colonization and in their effect on growth of winter wheat when applied in combination with different forms of nitrogen (vs.) and fertilizer anions (Cl−,,), treatments that influence other soil fungi such as the take-all disease organism,Gaeumannomyces graminis tritici. Banded fertilizer salts, singly and in combinations, were more inhibitory to root colonization by most VAM species than were incorporated salts.salts were more inhibitory to both wheat growth and VAM development than weresalts. TwoGlomusspecies,G.clarumandG.fasciculatum, appeared to be salt tolerant, developing abundant vesicles, hyphae, and colonizations to near 50% in the presence of incorporated (NH4)2SO4or NH4Cl. However, colonizations often were not indicative of growth responses; e.g., colonizations of 10% byGigaspora gilmoreior 20 to 40% byGlomusspecies often depressed growth, whereas 5 to 10% colonization byAcaulospora spinosain the presence of NH4Cl + KCl stimulated growth significantly. The effect of Cl−(with) in suppressing the pathogenic take-all fungus did not occur with symbiotic VAM fungi. The results indicate the relative effectiveness of certain species in tolerating liberal fertilization as well as their potential for stimulating or depressing plant growth.

ISSN:0008-4026    

DOI:10.1139/b85-165

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Annual production ofSphagnumon three perched and three raised forested bogs was determined and compared. Perched bogs occupy small depressions in glacial moraines and raised bogs occur on broad, flat plains. Data from both cranked rods and threads were used with regression techniques to determine rates of growth on hummocks and hollows of bog microrelief. Hummocks and hollows were operationally defined by the characteristic moss species that dominated each position. Over a 3-year sampling period, average rate of moss growth in perched bogs was 3.9 (± 4%) on hummocks and 13.1 cm year−1(± 13%) in hollows. In raised bogs, the growth was 3.6 (± 4%) and 9.1 cm year−1(± 14%), respectively. About half the lineal growth occurred early in the growing season, and slightly more of the remaining growth occurred in midseason compared with late season. Conversion to ovendry mass per unit surface area of bog indicates production of 320 on hummocks and 520 in hollows on perched bogs; 300 on hummocks and 370 g m−2 year−1in hollows on raised bogs. Because of the hummock–hollow microrelief, total surface area occupied by moss is about 35% greater than the vertically projected area of the bog. Final estimates ofSphagnumproduction per unit vertically projected bog area, taking this information into account, were 380 (± 19%) on perched bogs and 320 g m−1 year−1(± 19%) on raised bogs.

ISSN:0008-4026    

DOI:10.1139/b85-166

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Five species ofParaphysomonas(P.diademifera(Takahashi) Preisig & Hibberd,P.poteriophoraMoestrup & Kristiansen,P.stelligeraPreisig & Hibberd,P.subquadrangularisPreisig & Hibberd, andP.subrotaceaThomsen) have been found in Ontario, Canada; they have not been reported previously from North America. The taxonomic status offP.elegantissimaKling & Kristiansen is not clearly defined and scale morphology of this species could possibly be included within the range of form now known forP.takahashiiCronberg & Kristiansen; nevertheless it is proposed to recognize the two separate taxa at least until more specimens from other localities, including those possessing unperforated plate scales, have been examined.

ISSN:0008-4026    

DOI:10.1139/b85-167

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The occurrence of tamarack (Larix laricina(Du Roi) K. Koch) and black spruce (Picea mariana(Mill.) B.S.P.) macrofossils or subfossils on the tundroid patches at the forest limit indicates that those patches were colonized by trees in the past. The aim of this study is to reconstruct the fluctuations of the coniferous formations by macrofossil analysis. More than 465 macrofossils and 30 charcoals were collected, 31 and 23 of which, respectively, were14C dated. The results of charcoal analysis indicated that fires were more frequent in the southern part of the forest limits than in the northern part. During the last millenium three periods of fire (modern, 400, and 900 years) were noted in the southern part, two periods (modern and 600 years) at the forest limit, and none north of the forest limit. The majority of collected macrofossils are from the modern period; their death is related to the action of fire. The mosaic landscape of the forest tundra is related to a deterioration of the climatic conditions coupled with the history of fires.

ISSN:0008-4026    

DOI:10.1139/b85-168

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The distribution of a shoreline macrophyte,Xyris difformis, was measured along a gradient of exposure to wave action in several central Ontario lakes. Its abundance changed significantly along the exposure gradient (p < 0.001).Xyris difformisoccurred most frequently on shores of intermediate exposure. This distribution pattern could result from (i) maximum growth rates on intermediate-exposed shores or (ii) competitive displacement from less exposed, sheltered shores that have little disturbance, high nutrient concentrations, and dense vegetation. We attempted to distinguish between these two mechanisms by growing ramets ofX.difformisin the absence of neighbours (potential competitors) along the exposure gradient on a lakeshore and measuring the accumulated biomass after one growing season. Biomass varied with position on the exposure gradient (p < 0.01). Maximum biomass was accumulated on shores of intermediate and high exposure. In another experiment, seeds ofX.difformisgerminated on substrates from both ends of the exposure gradient at several water depths. The proportion of seeds germinating below the waterline on substrates from sheltered shores was significantly lower than the proportion germinating on substrates from exposed shores, suggesting that seeds ofX.difformismay have low germination ability on sheltered shores. The shoreline distribution ofX.difformisalong the exposure gradient is consistent with its physiological response curve along the gradient.

ISSN:0008-4026    

DOI:10.1139/b85-169

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The endophytic system ofPilostyles thurberiGray consists of initially uniseriate filaments which develop into an anastomosing complex of larger cortical strands and radial sinkers. In the cortical strands three cell types are recognized, two of which differ largely in the density of the cytoplasm, the shape of the nucleus, and the degree to which the cytoplasm becomes plasmolyzed during fixation. The nuclei of both cell types contain two nucleoli which are physically connected by a nucleolar bridge. The third cell type demonstrates sieve plates, including a calloselike substance in the sieve pores and is consequently considered to be a sieve element. The sieve elements appear to form a discontinuous system and are regarded as a vestigial cell type. Plasmodesmal connections across the host–parasite interface have not been observed.

ISSN:0008-4026    

DOI:10.1139/b85-170

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Total aboveground plant production in four mires near Schefferville, northern Québec, was estimated at 114 to 335 g m−2 year−1, with sedges (Carexspp.) making the greatest contribution. The litter-bag technique was used to determine the mass loss from decomposing tissue over 1 year and losses ranged from 6.4 to 26.6%, of which approximately 65% occurred during the winter months. Nutrient releases from decomposing litter are slow, generally proceeding in the sequence K > Mg > Ca > N, P. Tissue quality (nutrient, cellulose, and lignin content) appears to exercise a greater influence on decay rates than do environmental parameters (pH and temperature).

ISSN:0008-4026    

DOI:10.1139/b85-171

出版商:NRC Research Press    

年代:1985

数据来源: NRC