摘要:

Ten culture media were tested for their effect on growth and sporulation ofCercospora cruentaandC. canescensisolated from field-infected cowpea (Vigna unguiculata). There was very little mycelial growth and little or no conidia production on most media. Oxoid agar supplemented with V-8juice supported best growth and conidial production. Flooding V-8 juice agar with a conidial suspension resulted in multiplicity of tiny colonies with resultant increased sporulation. Conidia produced in culture were slightly longer than those produced in lesions on field-infected leaves and the degree of septation varied with the type of culture media. The width of conidia showed no apparent variation regardless of the culture media. More active mycelial growth but less conidial production was observed at agar concentration of 3% than at lower concentrations. Optimum temperature for mycelial growth and conidial production was 24–25 °C. Growth and conidial production were inhibited in complete darkness but stimulated by light.

ISSN:0008-4026    

DOI:10.1139/b78-030

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Additional fieldwork in Nahanni National Park and vicinity has added 91 species of bryophytes to the flora of that region. Twenty of these are new to the District of Mackenzie, and 37 are new to the Northwest Territories of Canada. Three species,Barbula coreensis(Card.) Saito,B. maximaSyed & Crundw., andB. perobtusa(Broth.) Chen are new to North America.

ISSN:0008-4026    

DOI:10.1139/b78-031

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A new discomycete (Helotiales) is described from grand fir (Abies grandis(Dougl.) Lindl.) in British Columbia, Canada;Grovesiella grantiin.sp. occurs on dead branches and as a secondary invader of cankers and dieback produced by other fungus pathogens.

ISSN:0008-4026    

DOI:10.1139/b78-032

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A variety of numerical taxonomic procedures was employed to assess variation of 437 diverse populations ofDaucus carota sensu lato, grown under controlled conditions, and of 100 herbarium sheets. The domesticated plants proved to be sharply discontinuous from the wild plants. In contrast with wild plants, domesticated plants possess relatively brittle, palatable, pigmented, larger, unbranched storage organs, fewer but larger relatively erect leaves, strict biennialness, larger fruits, comparatively rapid growth, relatively foliose involucral bracts, fewer central purple flowers in the umbels, smaller petals, fewer fruit spines, brittle mericarp spine hooks, and basally branched primary mericarp bristles. The first 11 differences are interpreted as the direct or indirect results of directional selection by man. The last six differences are hypothesized to be changes resulting from lack of stabilizing selection for characters of value in the wild. Domesticated carrots range from primitive Asian ('eastern') variants with yellow and purple storage organs and poorly dissected gray–green pubescent foliage to the familiar advanced type of ('western') cultivar with orange roots and highly dissected, relatively unpubescent yellow–green foliage. Numerical analysis indicated that an uninterrupted spectrum of variants connect these two kinds, and whereas two comprehensive groups of cultigens are distinguishable, any line of demarcation is arbitrary. The two kinds of cultigens are recognized asD. carotasubsp.sativusvar.sativus('western carrot') andD. carotasubsp.sativusvar.atrorubens('eastern carrot'). Wild carrots proved to be separable into two overlapping comprehensive groups, which were informally labelled subspecies aggregategingidiumand subspecies aggregatecarota(the latter assemblage also encompassing the cultigens). Subsp. agg.carotaprimarily includes cosmopolitan weedy variants, some of which may have contributed germplasm to the cultivars. More importantly, this group contains an inconspicuously differentiated Asian subgroup which was found likely to represent the primary ancestor of the domesticated carrot, as evidenced by similarity with the primitive cultigens studied.

ISSN:0008-4026    

DOI:10.1139/b78-033

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This study examines the previously reported inhibitory effects of Cd on root growth. In hydroponic experiments, 100 μg Cd/ℓ effected a 33% inhibition of lateral root initiation of corn. The growth of corn and soybean primary roots was not reduced at Cd concentrations of 1 mg/ℓ, and the number of lateral root initials in soybeans was not reduced at 2 mg Cd/ℓ. The toxic effects of Cd were ameliorated by additions of Zn or by additions of Fe citrate to nutrient growth solutions. While both Zn and Fe additions did result in increased lateral root initiation, the number of initials was significantly lower than the controls. Lead had no effect on the initiation of soybean lateral roots at a concentration of 100 μg Pb/ℓ. However, 5 mg Pb/ℓ did effect a 21% decrease in corn lateral root initials, but this decrease could not be demonstrated with higher Pb conce

ISSN:0008-4026    

DOI:10.1139/b78-034

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A sensitive and quantitative bioassay, based on the ability of the exotoxin ofPseudomonas glycineato inhibit ornithine carbamoyltransferase of bean, was employed in a comparative study of theP. glycineaandP. phaseolicolatoxins using high-voltage electrophoresis, thin-layer chromatography, ultrafiltration, and Sephadex-gel chromatography. TheP. glycineatoxin (glytoxin) has an elution volume/void volume (Ve/V0) ratio different from that of phaseotoxin when chromatographed on Sephadex G-25. Glytoxin passes through a membrane filter with an exclusion limit of 500 daltons whereas phaseotoxin does not. High voltage electrophoresis in buffers of different pH values showed that glytoxin, like phaseotoxin, migrates as an anion but shows greater mobility than phaseotoxin. Both toxins degrade on thin layers of silica gel. Glytoxin induces chlorosis in bean and soybean leaf tissues, and like phaseotoxin, is an inhibitor of ornithine carbamoyltransferase but not of aspartate carbamoyltransferase. Glytoxin is presumably responsible for the accumulation of ornithine which was observed in soybean leaves infected withP. glycinea. Our studies show that glytoxin and phaseotoxin are similar but not identical.

ISSN:0008-4026    

DOI:10.1139/b78-035

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Developmental anatomy of fruitbodies and mycelium in a clavarioid fungus,Pterulasp. (Aphyllophorales), was studied in the light microscope using plastic-embedded material and in the scanning electron microscope. Differentiation of skeletal and generative hyphae and of the hymenium and sclerotioid patches were similar in the fruitbody and mycelium. Experimental results indicated that the hymenium is ageotropic and that fertile fruitbodies form in both upright and inverted cultures. The nature of the skeletal hyphae, and generic delimitations in the Pterulaceae are discussed.

ISSN:0008-4026    

DOI:10.1139/b78-036

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Evidence is presented from numerical studies of herbarium and cultivated specimens and from observations on time of flowering that North American weed populations of white cockle are referable to the EuropeanSilene alba(≡Lychnis alba≡Melandrium album) and are not, as has been suggested, the products of hybridization between that species andS. dioica. The present status and distribution in North America ofS. alba, S. dioica, and the hybrids between them are described. Evidence for different generic circumscriptions ofSilene, Lychnis, andMelandriumis analysed and the limited applicability of the capsule dehiscence character is demonstrated. Recent treatments that acceptLychnisin a narrow sense and assign most of the North American species of the group to a large genusSileneare accepted pending further study. Two new subspecific combinations (S. uralensissubsp.attenuata(Farr) McNeill andS. uralensissubsp.montana(S. Watson) McNeill) are proposed.

ISSN:0008-4026    

DOI:10.1139/b78-037

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Signal Mountain forms the NW terminus of the Maligne Range in the Main Ranges E of the Continental Divide in the Canadian Rocky Mountains. The summer climate of the alpine zone on Signal is cooler and moister, with narrower temperature ranges, than that of Jasper townsite in the montane zone. Parent materials are Precambrian sandstones and conglomerates, with some siltstones and slates. Soils are Regosols, Brunisols, and Gleysols of pH 4.5 to 6.5. The alpine flora includes 157 vascular, 57 bryophyte, and 53 lichen species. Quantitative sampling of the major alpine community types (ct's) of Signal was followed by a 780-m transect study from the tree line on the dry, exposed SW slope to the tree line on the moist, protected NE slope. Dwarf shrubs predominate in most but not all ct's.Dryas octopetalais dominant in eight relatively xerophytic, lichen-rich, and chionophobous ct's where snow cover is shallow.Salix arctica, S. nivalis, Antennaria lanata. Carex nigricans, Cassiope tetragona, C. mertensiana, Phyllodoce glanduliflora, andArctagrostis arundinaceaare dominant or codominant in five relatively mesophytic and chionophilous ct's where snow cover is deeper and more persistent. The ct's and their habitats are described, compared on a community ordination, and their distribution and abundance are plotted on the alpine transect.

ISSN:0008-4026    

DOI:10.1139/b78-038

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

We measured water flow in simple xylem vessels ofSechium eduleat various pressures. We found a disagreement with Poiseuille's law, which changes from vessel to vessel and becomes abruptly pronounced in some cases. We discuss our data in terms of an 'impediment coefficient,'K. It can be shown that the total flux in a stem, calculated as the sum of the flux in single vessels, agrees quite well with the data reported in literature.

ISSN:0008-4026    

DOI:10.1139/b78-039

出版商:NRC Research Press    

年代:1978

数据来源: NRC