摘要:

Vigna benuensissp. nov. from north Cameroon is described. It is closely related toVigna ambacensisvar.pubigera, but is amphicarpic and shows slight differences in floral morphology and size. Some important morphological features are compared with those of its allied species.

ISSN:0008-4026    

DOI:10.1139/b89-126

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Wetland vegetation on lowlands of northern Yukon was related to gradients of pH, peat depth, and active-layer depth using detrended correspondence analysis. Seven vegetation types were distinguished by two-way indicator species analysis:Arctophilashoreline marsh,Carex aquatilis–Sphagnum–Chamaedaphnewet meadow,Scorpidium–sedge carpet,Carex rotundata–Andromeda–Sphagnum orientalelawn,Sphagnum–heath on firm peat, thickets and tussock tundra, andCalamagrostis canadensismeadow. TheArctophilamarshes and tussocky shrublands resemble other sites in the subarctic and low arctic wetland regions of North America, whileSphagnum–heath on firm peat is typical of high boreal and subarctic wetlands. The wet meadow, carpet, and lawn types of sedge–moss vegetation cannot be characterized as arctic or boreal because the geographic patterns of sedge–moss wetlands in northwestern North America remain unclear.

ISSN:0008-4026    

DOI:10.1139/b89-127

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Species–area relations of vascular plants and the effect of nesting colonies of gulls on plant species composition were investigated for 77 islands in Georgian Bay and Lake Huron in the Great Lakes region of Canada. The percentage of plant species classed as alien, annual, or biennial was significantly greater on islands with gull colonies. The slope of the species–area curve was significantly steeper on islands supporting gull colonies compared with islands lacking gull colonies. The expected decline in species richness with increased island remoteness was not detected statistically using multiple regression analysis. The difference in species–area slopes does not appear to reflect a lower propagule immigration rate to islands with gull colonies, because gulls are important in the dispersal of alien plant species to these islands. Larger islands with gull colonies tended to have richer floras than islands of similar size without gull colonies. It is suggested that on these larger islands the presence of gull colonies produces a gradient of soil nutrient and disturbance regimes, thus increasing habitat heterogeneity and species richness.

ISSN:0008-4026    

DOI:10.1139/b89-128

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Somatic embryoids and diploid plants have been obtained directly from anther cultures of an hybridCichorium intybusL. ×Cichorium endiviaL. maintained by micropropagation. Anthers at tetrad and microspore stages were the most reactive. Darkness and high temperature (35 °C) were necessary to obtain somatic embryo development on a medium with naphthylacetic acid (0.02 mg ∙ L−1) and 6-(dimethylallylamino)-purine (0.5 mg ∙ L−1). A combination of glutamine and ammonium nitrate was the most suitable nitrogen source. A short induction time (10 days) allowed the embryoids to grow into adult plants. Most plants from the somaclonal population derived from these embryoids showed a good phenotypic conformity, and some variants showed a large anthocyanic vein or narrow and incised leaves.Key words: somatic embryos, anthers,Cichorium,in vitrocult

ISSN:0008-4026    

DOI:10.1139/b89-129

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The technique of demography of parts was used to study the phenotypic plasticity ofChrysanthemum leucanthemum(ox-eye daisy). Plants were cloned and submitted to two separate experiments: three treatments of light intensity and three treatments of nutrient levels. Plant parts (leaves, branches, capitula, stems) were marked at regular intervals during the growing season. Leaves present at the time of transplant generally died earlier when light and nutrient treatments were reduced. However, the number and survivorship of the main stem leaves did not show any significant difference among treatments. In general the number of first-order branches, stems, capitula, and rosette leaves decreased with low light intensity and low nutrient levels. Demography of parts is a dynamic approach, allowing the study of cumulative production of leaves, branches, and capitula. Other techniques, such as traditional growth analysis and study of resource allocation, are more static and descriptive.

ISSN:0008-4026    

DOI:10.1139/b89-130

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

In an isolate of tobacco mosaic virus strain U1 there exists a small subpopulation containing a variant strain of the virus that induces the hypersensitive response onNicotiana sylvestrisSpegazzini & Comes. This type of variant is strongly selected for during the regeneration of plantlets from mature leaf tissue of plants infected with tobacco mosaic virus U1. When whole plants derived from disks were transferred into a glasshouse, those containing this type of variant were severely stunted, showed mosaic symptoms, and most of them died. Some that had originally contained lower titers of variant-type virus survived to flower but produced only a few seeds. Plants that initially contained only wild-type virus had high titers of tobacco mosaic virus, survived and grew well, exhibited mosaic symtoms, and flowered and set seed normally. Repeated assays of virus in these plants revealed no detectable variant-type virus. Apparently, during callus development and organogenesis in culture, partial segregation of the mixed U1 population occurred, and variants preferentially infected the developing tissues. This represents a situation in which dramatic change in the genetic structure of an RNA virus population occurs during development of the host plant.

ISSN:0008-4026    

DOI:10.1139/b89-131

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

DNA content was measured cytophotometrically in Feulgen-stained nuclei of fusiform cambial initials from 1- (twig) and 19-year-old (stem base) cambia of balsam fir (Abies balsamea) trees throughout the season. Telophase (2C) and prophase (4C) DNA contents varied with both cambial age and time of year. Maximum DNA contents were observed at the beginning of cambial activity in April. They were lower in the 1-year-old cambium (42.3 (2C) and 84.3 (4C) pg DNA) than in the 19-year-old cambium (59.4 (2C) and 111.1 (4C) pg DNA). The DNA levels decreased during the cambial growing season, attaining minimal values in September of 28.3 (2C) and 53.5 (4C) pg and 37.9 (2C) and 74.5 (4C) pg in the 1- and 19-year-old cambia, respectively. In the autumn, cells accumulated in the G1phase of the cell cycle. DNA synthesis then took place increasing the 2C levels from the minimum values to the maximum values. This DNA synthesis in 1-year-old cambia started before the beginning of the transition from the resting to the quiescent stage of dormancy.

ISSN:0008-4026    

DOI:10.1139/b89-132

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Inside the distal part of a leaf primordium approximately 12 cells thick and differentiated into distinct abaxial and adaxial areas, the following events occur simultaneously, at an early critical stage, in the middle of the second plastochron of leaf development: (i) determination of the differentiation of the two layers of cells bordering the abaxial–adaxial contact area into palisade and spongy parenchyma; (ii) determination of the ability of these two tissues to react to a triggering of mitotic activity, which enables them to initiate the lamina formation; (iii) determination of the formation, between the two tissues, of a system that inhibits dorsiventral mitosis and constitutes the foundation for lamina development. From the fifth plastochron, this threefold control system will lead to the organogenesis of the lamina. Depending on the stage of development, two kinds of anomalies occur on the lamina when the abaxial–adaxial contact area is disturbed. Disturbance during the early critical stage results in organoid enations and later disturbance in light and dark spots. These anomalies are comparable to those resulting from severe virus infections. The above process of development is not compatible with the classical model of lamina development.

ISSN:0008-4026    

DOI:10.1139/b89-133

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Esterase activity, obtained from the surface of tuber slices, increases significantly when the slices are treated with water and aged in air. This rise in esterase activity was prevented if the tuber surface was treated with unsaturated fatty acids which are toxic to tuber cells. The fatty acids did not inhibit the activity of purified esterase. Also, application of inhibitors of active oxygen to the tuber surface did not prevent the reduction of esterase obtained following fatty acid treatments. It is suggested that fatty acids inhibit the release of esterase from the cells. This is supported by the detection of patatin (the glycoprotein responsible for the esterase activity) on the cell membrane as judged by the agglutination of isolated protoplasts with low levels of patatin antiserum.

ISSN:0008-4026    

DOI:10.1139/b89-134

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The symptomatology and histopathology of chrysanthemum phloem necrosis, a new disease of florists' chrysanthemum was investigated. The disease results in flecking, yellowing, and premature deterioration of lower leaves and flower distortion in theDendranthema grandifloraTzveler. (syns.D.morifoliaRamat.,Chrysanthemum morifoliumRamat.) Marble cultivar group. Cleared leaves of 'Pink Marble' revealed vascular browning in midveins and secondary veins that was enhanced at 32 °C. The sieve elements and associated cells in affected leaves were often necrotic and collapsed, a condition that was aggravated by elevated temperature. Spherical-to-elongate mycoplasmalike organisms, 0.2–1.0 μm diameter, were observed only in infected plants within collapsed sieve elements. Mycoplasmalike organisms were not detected in uninfected plants; sieve-plate elements contained merely fibrillarp-protein, a normal cell component. In comparison to uninfected plants abnormal callose accumulation and lignin formation were observed in the phloem of infected plants, and elevated levels of phenolic materials were found in vascular and nonvascular tissues.

ISSN:0008-4026    

DOI:10.1139/b89-135

出版商:NRC Research Press    

年代:1989

数据来源: NRC