摘要:

Thirty-five bryophyte species representing the major habitats of a high arctic tundra lowland (Devon Island, Canada, 75° N) have been analyzed for contents of nitrogen, carbon, ash, and ether- and alcohol-soluble fractions. Mean contents (%) for the green portion of these species are total nitrogen, 1.00 (1.08 ash-free); total carbon, 45.9 (48.7 ash-free); ether-soluble fraction, 2.8 (3.0 ash-free); alcohol-soluble fraction, 11.8 (12.5 ash-free); and ash, 5.7. In the hydric species group, the total nitrogen content and the alcohol-soluble fraction are significantly greater than in mesic or xeric groups. When the green and brown segments are compared, the nitrogen content and the alcohol-soluble fraction are greater in the green portion, while the ash content is higher in the brown portion. The ash-free caloric values of hydric species range from 4.57 to 4.97 kcal/g, while the mesic and xeric species have a range from 4.50 to 4.69 kcal/g. The relations between habitats and between the green and brown portions are discussed in relation to general metabolic activity and productivity.

ISSN:0008-4026    

DOI:10.1139/b74-149

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The patterns of variation in vegetation and the more apparent environmental parameters within and between the ridges of a recently formed Hudson Bay coastal raised-beach system 1.5 km wide are presented and analyzed using principle-component analysis and correlation coefficients. Previous research in the area did not detect such patterns within the general lichen–heath.There is a marked developmental sequence from the coast inland, involving increases in the soil moisture content and the peat-layer thickness, but variations independent of any age sequence occur on an intraridge basis. Relationships are drawn between these variations and the biomass or cover of nine important species.

ISSN:0008-4026    

DOI:10.1139/b74-150

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A virus isolated from white clover (Trifolium repensL.), dahlia, and tomato from Ontario, dahlia from Manitoba, and tomato and dahlia from British Columbia was identified as tomato spotted wilt virus (TSWV). Seven isolates of the virus examined had similar host reactions; four of them, investigated in detail, were similar in their localization in tomato leaf cells and physical properties also. The virus particles, 78–97 nm in diameter, were abundant in tomato leaf mesophyll cells and occurred in clusters or arrays surrounded by a membrane.The virus was purified by a method modified from a previously reported one and a specific antiserum was prepared. TSWV appears to be weakly immunogenic, as a high titer antiserum could not be obtained.At least three species of thrips, i.e.Thrips tabaciLind.,Frankliniella fuscaHinds, andF. occidentalisPerg., known as vectors of TSWV elsewhere, occur in Canada.F. fusca, which occurs in eastern Canada, efficiently transmitted all isolates of the virus.T. tabaci, a vector in several countries and widespread in Canada, failed to transmit the virus.

ISSN:0008-4026    

DOI:10.1139/b74-151

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Growth from uredospores seeded in axenic culture is described for several races ofPuccinia graminisPers. f. sp.tritici(Erikss. and Henn.) and race 3 ofMelampsora lini(Ehrenb.) Lév. on complex media containing peptone, yeast extract, and bovine serum albumin (BSA); and for an Australian isolate ofPuccinia graminis, race 126-ANZ 6,7, andMelampsora lini, race 3, on chemically defined, liquid media.Of six North American isolates ofPuccinia graminisonly race 38 formed colonies approaching those of race 126-ANZ 6,7 in final size and general morphology on complex media. 5′AMP had no effect on the growth of 126-ANZ 6,7, but cyclic AMP inhibited growth after uredospore germination. Good growth and sporulation were obtained with 126-ANZ 6,7, but not with the other isolates tested, using a new, chemically defined liquid medium, sterilized by millipore filtration, and containing glucose, Czapek's minerals plus micronutrients, Ca2+, glucose and aspartic acid, glutathione, and cysteine. Uredospores produced in culture reinfected exposed mesophyll tissue, but not intact seedling leaves of wheat.Highly reproducible growth and sporulation ofMelampsora lini, race 3, were obtained routinely on a solid medium containing Difco-Bacto agar, sucrose, Knop's minerals, micronutrients, yeast extract, peptone, and BSA. Vegetative cultures, capable of reinfecting the cut ends of surface-sterilized flax cotyledons, could be maintained indefinitely by subdivision before sporulation and transfer to the same medium minus BSA. Evidence is presented that BSA stimulated the development of colonies and the formation of uredospores. The mode of action of BSA is unknown, but it could not be replaced by putrescine.A new chemically defined, liquid medium containing sucrose, Knop's mineral salts, micronutrients, aspartic (or glutamic) acid, and cysteine supported the growth of colonies ofMelampsora liniin a highly reproducible manner. The formation of uredospores and teliospores by these colonies was controlled by (a) the level of Ca2+(as Ca(NO3)2∙4H2O), (b) the concentration of aspartic acid, and (c) the number of colonies per flask. At inoculum levels giving 40 to 60 colonies per flask, in media containing 8.5 mM Ca+and 45 mM aspartic acid, uredospore formation occurred in 60 to 70% of the colonies. A decrease in the Ca2+level to 4.25 mM, or a decrease in aspartic acid to 22.5 mM, or adjustment of the inoculum level to give about 10 colonies per flask each resulted in only infrequent sporulation. The uredospores produced in vitro infected intact, 1-week-old flax cotyledons in a normal manne

ISSN:0008-4026    

DOI:10.1139/b74-152

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The fine structure of zoospores ofEntophlyctis confervae-glomeratae, Rhizophydium patellarium, andCatenaria anguillulaehas been described and compared. The zoospores ofE. confervae-glomerataecontain many posteriorly located mitochondria in a petal-like arrangement. On the inner (proximal) side of a kinetosome are two electron-dense, slightly curved bands with the convex side directed inward towards the eccentrically located nucleus. Microtubules radiate from the convex side of the bands. Two or three lipid bodies are seen usually in the anterior region of the zoospore with microbodies often associated with them. Ribosomes are scattered throughout the cytoplasm. The zoospores ofR. patellariumcontain a single, bowl-shaped mitochondrion in the posterior region and a centrally located nucleus. Ribosomes are mainly clustered between the mitochondrion and the nucleus and are partially enclosed by a double-membrane envelope. No microtubules are seen associating with the kinetosome and the non-functional centriole lies parallel to the kinetosome. In the anterior region there is a single lipid body as well as two types of microbodies: very electron-dense microbodies un-associated with any other organelle, and a finely granular microbody associated closely with the lipid body. The zoospores ofC. anguillulaecontain a single basal mitochondrion with the associated side-body complex. From the proximal region of the kinetosome, a set of 27 microtubules radiate anteriorly and surround the base of the cone-shaped nucleus. Ribosomes are enclosed within a distinct nuclear cap. Gamma bodies are present in the cytoplasm. Taxonomic implications resulting from this study are discussed.

ISSN:0008-4026    

DOI:10.1139/b74-153

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Pythium polymastumhas been found in the roots of oilseed rape (Brassica campestrisandB. napus),Capsella bursa-pastoris, andLunaria annua, grown in field soil from widely separated localities in Saskatchewan. It is virulent on rape and 18 other crucifers, and avirulent or only slightly virulent on numerous cultivated plants belonging to other families. This is the first report of the fungus as a pathogen on crucifers. It is suggested that it may play a part in a root-rot complex, that it is indigenous, and that cruciferous weeds act as alternative hosts.

ISSN:0008-4026    

DOI:10.1139/b74-154

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

We present a quantitative ultrastructural study of the size and frequency (density distribution) of plasmodesmata in the cell wall in common between the internodal cell and peripheral cell (and central cell) ofChara corallina. In the wall in common between the central cell and internodal cell the relative area occupied by plasmodesmata is 15.3%; the pore diameter (less the plasmalemma) is 118 nm; the length is 1.54 μm, and the frequency is 1.4 × 109 pores/cm2. In the wall in common between the peripheral cell and internodal cell the relative area occupied by the plasmodesmata is 9.6%; the pore diameter is 100 nm; the length is 1.07 μm; and the frequency is 1.2 × 109 pores/cm2. The plasmodesmata have an anastomosing structure likeNitella translucensbut the pore diameter and frequency are much greater.

ISSN:0008-4026    

DOI:10.1139/b74-155

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Scanning electron microscope studies of anthers of the dicotyledonsHelianthus annuus, Solanum tuberosum, andLupinus polyphyllus, and the monocotyledonsIris pseudo-acorisand aLiliumhybrid revealed discontinuities or holes in the meiocyte callose wall and continuity of the plasma membranes of adjacent meiocytes. The holes in the callose wall generally were confined to areas where neighboring meiocytes were in contact. The holes varied in size within locations and between taxa. The largest holes, about 2.4 μm diameter, were found inLupinus. Fixation in standard acid–alcohol fixatives resulted in marked plasmolysis and loss of cytoplasmic detail, but the nucleolus and bivalents were readily apparent. Fixation in buffered glutaraldehyde, with or without postfixation in OSU4, preserved the cytoplasmic organelles and plasmolysis was minimal, but bivalents could not be distinguished. All fixatives preserved the nuclear membrane so that the nuclear region was clearly delimited from the cytoplasm.

ISSN:0008-4026    

DOI:10.1139/b74-156

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Discontinuities, considered to be holes, were observed in the meiocyte callose wall of 25 dicotyledon and 5 monocotyledon taxa investigated by phase-contrast and Nomarski interference-contrast optics. With the exception of theHelianthusspp., where regular distribution was observed, the holes were confined to two to four discrete areas of the callose wall. Hole size was highly variable; the largest, of about 2 μm diameter, occurred in lupin (Lupinus polyphyllusLdl.). Cytoplasmic connections between neighboring meiocytes and (or) cytomictic phenomena were observed in 13 of the 30 taxa investigated.

ISSN:0008-4026    

DOI:10.1139/b74-157

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Pollen size, type and number of apertures, and exine thickness are reported for 25 species representative of all four subgenera ofMinuartia(Caryophyllaceae) and of the related generaHonkenyaandWilhelmsia. The pollen of the species ofMinuartiasubgenusRhodalsineis trizonocolpate with a relatively thin exine and it differs from that of all other species of the subfamily Alsinoideae. Species of this subfamily apparently all have pollen grains that are pantoporate with a thick exine. The relationship of the species of subgenusRhodalsinewith those ofSpergularia(subfamily Paronychioideae), a genus which has pollen grains similar to those of subgenusRhodalsine, is discussed. A new name,Minuartia webbiiMcNeill and Bramwell, is proposed.

ISSN:0008-4026    

DOI:10.1139/b74-158

出版商:NRC Research Press    

年代:1974

数据来源: NRC