摘要:

Atypical cones were found in 1983 and 1984 on many trees in three young plantations ofLarix laricina(Du Roi) K. Koch. On-shoot and within-crown locations of cones of each type were noted as the cones were collected, at the stage of anthesis or receptivity, for analysis by dissection or sectioning. Development of other cones of each type was monitored. Proliferated seed cones had more bracts than typical seed cones and were commonly located where more vigorous vegetative development (neoformation) was likely. Most bisporangiate cones had proximal microsporophylls and distal bracts; a few also had microsporophylls at their apices. The bisporangiate cones were subdivided according to proportions of different appendages. Those with more female appendages tended to occur on short-shoot axes more distally located along the parent long shoot and thus where more vigorous development was likely. Bisporangiate cones with mainly female appendages developed to seed-cone maturity. Those with mainly male appendages died soon after anthesis. Pollen cones usually have no basal foliage leaves, but some pollen cones with such leaves occurred. The leaves died with the cone tissues after anthesis. Occurrence, composition, and development of these atypical cones were discussed in relation to their position, shoot vigour, and preformation.

ISSN:0008-4026    

DOI:10.1139/b86-061

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Several cytochemical methods demonstrated that urediospore walls ofPuccinia graminisf. sp.triticiwere probably composed of five layers, including the pellicle as the outermost layer. Two previously undescribed layers were located around the inner periphery of the spore walls. Staining for periodate-sensitive glycosubstances occurred uniformly and heavily throughout the wall except that the pellicle was unstained, and the innermost layer (3c) was more lightly stained by periodic acid – thiocarbohydrazide – silver proteinate. There was little wheat germ lectin or concanavalin A binding to the urediospore wall except in the hilar region, where wheat germ lectin bound heavily, and in the germ pore region, where binding of concanavalin A occurred. The walls of about one-half of the urediospores that were examined contained silicon deposits. Germ tube walls were composed of two layers: a broad outer layer and a narrower inner layer. The inner layer stained more heavily for periodate-sensitive glycosubstances than did the outer layer. Germ tube walls bound wheat germ lectin, but not concanavalin A. Appressorial walls were also composed of two layers, but the inner layer was much broader than that of germ tube walls, and the outer layer stained more heavily for periodate-sensitive glycosubstances. There was strong wheat germ lectin binding to the appressorial walls, but concanavalin A binding was sparse. Both germ tubes and appressoria were coated with a mucilagenouslike substance.

ISSN:0008-4026    

DOI:10.1139/b86-062

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Multivariate techniques were utilized to examine even-aged jack pine stands on upland sandy sites at the southern edge of the boreal forest near Elk Lake, Ontario. Cluster analysis of 180 stands led to the recognition of 10 vegetation types, each showing a unique combination of floristics, physiognomy, and environmental components. Classification of common species led to the recognition of five ecological groupings, which show varying degrees of association with the vegetation types. Nonmetric multidimensional scaling of the stands suggested a vegetational continuum in response to overall moisture availability. A corresponding ordination of common species indicated the development of interspecific associations related to soil moisture conditions. It is suggested that the vegetational composition of upland jack pine forests is determined by both probabilistic and deterministic effects, and this is discussed in the context of vegetation structure and dynamics.

ISSN:0008-4026    

DOI:10.1139/b86-063

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The present-day distributions ofCeratophyllum demersumandC.echinatumare useful in interpreting the Quaternary distributional history of aquatic plants. East–west North American disjunct distributions of submersed hydrophytes are probably due to incomplete interglacial migrations. Widespread species such asC.demersumhave successfully bridged gaps formed when populations migrated into isolated southern réfugia to escape glaciation. Species with narrower ranges, such asC.echinatum, are still in the process of doing so. Northern disjunct distributions ofC.demersumindicate that the species also survived glaciation in northwest refugia. It is apparent that many submersed aquatic plants have endured the migrational pressures imposed during glacial periods. Their ability to do so is attributable to four factors: (i) long species durations, (ii) formerly continuous distributional ranges, (iii) high vagility, and (iv) adaptation to cold, oligotrophic conditions. Extant hydrophyte communities in glaciated North America may resemble those in existence during former interglacial periods.

ISSN:0008-4026    

DOI:10.1139/b86-064

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

In two plants from one population ofStipa lemmonii, variable intercorrelations in ovules changed and variation within ovules increased with development. These changes are a quantitative expression of the increasing complexity that occurs with ontogeny. The results occur whether original data or those adjusted with respect to size (residuals from regression analysis using size as an independent variable) are analyzed, implying that the quantitative changes that occur with development are not dependent on size increase alone. Ovules of the two plants tended to become more different from each other with development, especially when adjusted data were analyzed.

ISSN:0008-4026    

DOI:10.1139/b86-065

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Cell division was examined with the electron microscope in the unicellular red algaFlintiella sanguinaria.Flintiellamorphologically resemblesPorphyridium purpureum, the only other red algal unicell that has been examined for ultra-structural details of cell division. Both genera are in the order Porphyridiales (Bangiophyceae), an unnatural assemblage of reduced forms in great need of taxonomic revision. Before mitosis, the nucleus migrates to the cell periphery. As in all red algae examined, exceptPorphyridium, the nucleus-associated organelle is a polar ring. At prometaphase, one or two microtubule-containing cytoplasmic invaginations penetrate the nucleus at each pole. By metaphase an intranuclear spindle is found in association with a typical metaphase chromosomal plate. The nuclear envelope is intact except for a single, large gap at each pole. Perinuclear endoplasmic reticulum is absent. An elongated anaphase interzonal midpiece is formed which breaks down at telophase. The daughter nuclei are widely separated by the chloroplast, which is constricted at the same time as daughter cell formation occurs by a cleavage furrow associated with a finely filamentous region similar to the contractile ring found in many animal cells. Because of pronounced differences in several mitotic features, it is concluded thatFlintiellais not closely related toPorphyridiumand instead shows closer phylogenetic ties with other macroscopic genera.

ISSN:0008-4026    

DOI:10.1139/b86-066

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Flavonoid profiles have been determined for 16 species ofMitellaand for the two monotypic genera,BensoniellaandConimitella. With a single exception the profiles are based upon the flavonols kaempferol, quercetin, and myricetin. The flavanone eriodictyol was seen in two Japanese species ofMitella. The flavonols exist as a series of 7-O-mono-, 3-O-mono-, 3-O-di-, and 3-O-triglycosides, although not all levels of glycosylation occur in each taxon. 7-O-Methylkaempferol and 7-O-methylquercetin were found inM.nudaandM.diphylla;M.nudaalso has isorhamnetin. The flavonoids ofM.nudaare unique in the genus, but otherwise the distribution of the pigments does not offer support for Rydberg's view of the species being assigned to four genera or Rosendahl's view thatMitellacomprises two sections. The flavonoid profile ofBensoniella oregonaclearly distinguishes it fromMitella. Flavonoid data forConimitella williamsiiagree in general with those of a moderately advanced species ofHeucherain agreement with Savile's views on the origin ofConimitella. Our results are discussed in terms of the recent finding thatConimitellaandMitellaform natural hybrids.

ISSN:0008-4026    

DOI:10.1139/b86-067

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The vegetation of Voyageurs National Park, Minnesota, U.S.A., was investigated, in part to establish a plant community classification system that would be useful to park managers and naturalists, and to evaluate short-term changes within plant communities. Samples from 120 stands were ordinated and classified on the basis of synecological coordinates, a system of ecological coordinates relating floristics to physical site conditions. Along indirect gradients of moisture and nutrient conditions, 12 ecological types were distinguished. Within each ecological type, it is expected that stands of diverse cover types will tend to converge, over a period of 150–200 years, on an edaphically constrained “climax” community characteristic of that ecological type, given present management practices and disturbance regimes. Permanent plots were established in 46 stands to permit future testing of these projections. Ecological types, named for expected dominants and for a typical undergrowth species or genus, include (1) jack pine – oak –Arctostaphylos; (2) red pine – white pine –Linnaea; (3) fir–spruce–birch–Lycopodium; (4) fir–birch–Mitella; (5) oak–maple–Uvularia; (6) ash–elm–Trillium; (7) black ash –Caltha; (8) white cedar –Coptis; (9) black spruce –Alnus; (10) black spruce –Kalmia; (11) leatherleaf (Chamaedaphne) bog; and (12) marsh.

ISSN:0008-4026    

DOI:10.1139/b86-068

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A study of morphological variation in theSalix lucidacomplex revealed three geographical races: one in northeastern North America, a second in western North America extending from Alaska to California, and a third in the southern Rocky Mountains,S.lucidassp.lucida,Salix lucidassp.lasiandracomb, nov., andSalix lucidassp.caudatacomb, nov., respectively. TheSalix reticulatacomplex in the Rocky Mountain region is represented by two geographical races, ssp.reticulatain the north and ssp.nivalisin the south. Variation in ssp.nivalissuggests that hybridization and introgression occur where the two races overlap, and that the results of past hybridization are still evident in the southern Rocky Mountains.

ISSN:0008-4026    

DOI:10.1139/b86-069

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The interaction betweenGlomus intraradicesSchenck & Smith, a vesicular–arbuscular mycorrhizal fungus, andFusarium oxysporumSchlecht f.sp.radicis-lycopersiciJarvis & Shoemaker and its effect on tomato plants were investigated over a 12-week period. The root colonization byGlomuswas not affected by the presence ofFusarium. The number ofFusariumpropagules was consistently lower when the plants were inoculated withGlomus. The presence ofGlomusdecreased root necrosis caused byFusariumin weeks 5, 11, and 12, but no significant effect was observed for the other 9 weeks. The results obtained at any observation time for the endomycorrhizal colonization and theFusariumpopulation, but not for the percent of root necrosis evaluation, were consistent throughout the 12-week experiment. It is concluded that the parameters used to study the interaction between a vesicular–arbuscular mycorrhizal fungus, a fungal root pathogen, and a host plant must be measured at different times after inoculation with the pathogen to make sure that observations are representative of the interaction under study.

ISSN:0008-4026    

DOI:10.1139/b86-070

出版商:NRC Research Press    

年代:1986

数据来源: NRC