摘要:

The range of photoperiodic adaptation among populations ofXanthium strumariumL. in Europe, Asia Minor, and northern Africa is nearly as broad as among populations in North America. Photoperiodic diversity within the indigenous morphological complex,strumarium, is relatively restricted, including night requirements primarily less than 8 h. American introductions include plants with reproductive requirements ranging from 7.5-h nights in northern populations to 10.5–11-h nights in southern populations. Populations in northern Europe in indigenousstrumariumand introduced complexes,echinatumanditalicum, show a photoperiodic response thinly separated from day neutrality. Southern European populations show reproductive diversity among introduced plants and include sympatric occurrences of three morphological complexes,cavanillesiiof South America,chinenseof North America, andorientalepossibly of North America. Thechinenseintroductions to northern Africa (Morocco, Egypt) are similar to those of Spain with a night requirement of 10.25–10.5 h. Those of Asia Minor include theitalicumcomplex in Turkey and Israel, 9.0–9.25 h, and thechinensecomplex in southern U.S.S.R., 9.75 h, and in Israel and Iraq, 10.5–11.0 h. Although some of the photoperiodic diversity of the cockleburs of the Old World probably resulted from hybridization between indigenous and introduced plants, the broad adaptive potential was imported from America.

ISSN:0008-4026    

DOI:10.1139/b74-231

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The cytotaxonomy of seven closely related species ofDrabais discussed and a key is given. The species are as follows:D. fladnizensisWulfen (n = 8);D. lacteaAdams (n = 24);D. lonchocarpaRydberg (n = 8);D. nivalisLiljebl (n = 8);D. palanderianaKjellman (n = ?);D. porsildiiG. A. Mulligan, sp. nov. (n = 16); andD. subcapitataSimmons (n = 8). Characteristics of sterile artificial and of natural hybrids, between some of these species and between them and other species ofDraba, are discussed.Draba fladnizensis, D. lonchocarpa, andD. nivalisare diploids, each with two homologous sets of eight chromosomes that are partly homologous with sets of the other two species.Draba porsildiicontains two sets of 16 chromosomes, each with two completely homologous genomes, and each genome from both sets of 16 is partly homologous with either of the genomes in the other set. All four genomes ofD. porsildiiare partly homologous with each genome ofD. fladnizensis, D. lonchocarpa, andD. nivalis.

ISSN:0008-4026    

DOI:10.1139/b74-232

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The soil microfungi associated with 26 communities of aspen (Populus tremuloides) in Saskatchewan were investigated using a dilution plate technique. Frequency values for the taxonomic entities isolated were calculated, based on occurrence at six sampling sites in each community. Most of the entities were quantitatively rare. The frequency values of the 51 commonest entities were used for quantitative analysis of microfungal community relationships by principal components analysis and by agglomerative classification. These analyses demonstrated only limited correlations of microfungal community structure and species performance with the edaphic and vegetational factors studied. The microfungal communities of aspen stands in the boreal forest region of Saskatchewan appeared to be a distinctive group characterized by the abundance ofMortierellaspp. The remaining communities, from all other parts of the province, were distinct from the boreal communities but did not form other discrete groups. Many of them contained a substantial number of species which are common grassland soil microfungi, such asFusariumspp. Almost all the common species found in aspen soils in this study have been reported previously from soil.

ISSN:0008-4026    

DOI:10.1139/b74-233

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A study of angiosperm reproductive biology was made in four plant communities in southwestern British Columbia. Species of all four communities have staggered, peak flowering times, resulting in phenological spectra. Anemophily is the major mode of pollination in a salt marsh, while entomophily predominates in a subalpine meadow. Two sphagnum bogs have more of a balance between wind and insect pollination. There are corresponding differences in the proportions of showy-flowered species in the communities. It is proposed that interspecific competition has greatly influenced the evolution of both species and community flowering strategies.Biotic seed dispersal prevails in the salt marsh and bogs, while most of the subalpine meadow species are wind-dispersed. Species and community modes of dispersal depend on the nature of the vegetation and the relative availability of dispersal vectors, as well as on diaspore morphology.Although vegetative reproduction and self-compatibility are fairly common, the bulk of the flora and vegetation at all four sites has breeding systems promoting outcrossing. There is little evidence that the physical environments of these communities, all harsh in at least some respects, have selectively favored autogamous or agamospermous species.

ISSN:0008-4026    

DOI:10.1139/b74-234

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The surface structure of three types of myxomycete Plasmodia, namely, protoplasmodium (Echinostelium minutum), aphanoplasmodium (Stemonitis flavogenita), and phaneroplasmodium (Physarum polycephalum), was studied with light, scanning, and transmission electron microscopy.E. minutumandP. polycephalumpossess robust slime sheaths composed of filaments 50–100 Å in diameter. The hyaline aphanoplasmodium ofS. flavogenitalacks a slime sheath; its plasmodial surface is covered with slender filopodia. The potential role of the plasmodial surface is discussed in relation to phagocytosis, cell movement, coalescence, and cell wall formation.

ISSN:0008-4026    

DOI:10.1139/b74-235

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Leaves of 35 species of temperate and tropical plants absorbed CO in light from air containing 6 ppm CO at an average rate of 0.19 μl/h g fresh weight. CO absorption was measured by the uptake of14CO from a closed flowing gas system. CO uptake by bean leaves varied considerably with age. Uptake by nine species having widely different rates of absorption was exactly proportional to CO concentration in the range 0 to 100 ppm CO. Absorbed CO was metabolized either by oxidation to CO2and fixation as such or by reduction and incorporation into serine. Corn, a C4plant, emphasized the former pathway and bean, a C3plant, emphasized the latter pathway. CO had various effects on the photosynthesis of leaves of different species; ranging from being inhibitory at concentrations as low as 65 ppm to exerting no influence, or even permitting an increase in net CO2fixation at 99% CO because of the absence of O2.Plants do not contribute significantly to the global CO balance because their uptake rate is low at the CO concentration normally encountered in interurban areas. However, their contribution may become very important in or near urban and polluted areas, where elevated CO concentrations are frequently found.

ISSN:0008-4026    

DOI:10.1139/b74-236

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

By an ethanol treatment isolation method,Echinopodospora spinosa(Cailleux) Malloch & Cain has been found in subsurface soil from eight different localities in Nigeria. The fungus is characterized by its wide, club-shaped asci and spiny, appendaged ascospores. This is the first report of the occurrence ofE. spinosafrom soil.

ISSN:0008-4026    

DOI:10.1139/b74-237

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Tremella globosporaReid is described from 32 collections made in British Columbia. The fungus grows directly from within perithecia of species ofValsaandDiaporthefound, in this study, on hosts belonging to seven Angiosperm genera and three of Gymnosperm. Single-spore isolates were made from basidiocarps selected to represent as many variables as possible; both colors (yellow and white) of the basidiocarp, proximity of position on a single twig versus considerable distance between sites, both genera of pyrenomycete host, four genera of seed plants, and collection dates from January to September. Compatibility tests indicated a single species with a modified tetrapolar mating system typical of the genusTremella. Selected dikaryotic isolates were grown in laboratory culture on simple media, and fertile basidiocarps were produced. Variation in size, color, and consistency of basidiocarps in culture was compared with those in field collections. Clamp connections, branching from the clamp cell, and other microstructures produced in culture are also described. No reaction ofT. globosporatoValsacultures or sterilizedValsaperithecia and extracts was observed.

ISSN:0008-4026    

DOI:10.1139/b74-238

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The mineral element content of plant tissues and substrate ofBuxbaumia aphyllawas analyzed and represents the first data for bryophyte sporophytes. There is no apparent 'barrier' preventing the normal movement of elements from the gametophyte into the sporophyte. Silver, previously found only inPolytrichumandAtrichum, was found inBuxbaumia.

ISSN:0008-4026    

DOI:10.1139/b74-239

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

not available

ISSN:0008-4026    

DOI:10.1139/b74-240

出版商:NRC Research Press    

年代:1974

数据来源: NRC