摘要:

Paleomyrtinaea princetonensisgen. et sp.nov. Pigg, Stockey & Maxwell is described from the Middle Eocene Princeton Chert of British Columbia, Canada. Anatomically preserved fruits are berries up to 1.6 × 0.78 cm with a fleshy fruit wall that consists of a three-layered pericarp. The exocarp is composed of a uniseriate epidermis of tabular cells and an outer hypodermis of small cells and the mesocarp is aerenchymatous. Some seeds are invested in a pulpy endocarp. The seeds are campylotropous, 1.8 mm long and 1.6 mm wide, and contain a curved embryo cavity about 1.5 mm long and 0.64 mm wide. Four distinct integumentary zones can be recognized, an outermost zone two to three cells thick of tangentially elongate cells, a second zone, constituting the bulk of the integument, of small, isodiametric cells, a third zone of uniseriate, columnar cells that extends into the germination valve, and an innermost zone of five to six layers of tangentially elongate cells. The genus is also represented by fruits and seeds from the Upper Paleocene Sentinel Butte Formation, Almont, North Dakota. Affinities of these fruits are with the berrylike guavas of the Myrtaceae, tribe Myrteae, subtribe Myrtinae, and in particular, with the closely related generaMosieraSmall andPsidiumL. A brief review of the fossil record of the Myrtaceae is also presented.Key words: Myrtales, Myrtaceae, Tertiary, permineralization, fruit, seed.

ISSN:0008-4026    

DOI:10.1139/b93-001

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Peat cores from fiveSphagnum-dominated peatlands in boreal continental Canada were analyzed for plant macro fossils. Results indicate that peatland development was influenced both by local autogenic and regional climatic factors. The general direction in peatland development from rich fen to poor fen to bog can primarily be ascribed to internal processes, especially peat accumulation. Quantitative paleoenvironmental reconstructions based on fossil moss assemblages indicate that all five peatlands were initially dominated by brown mosses with inferred pHs of approximately 6.0, and a water table at 5–15 cm below the surface of the peatland. Subsequently,Sphagnum-dominated peatlands developed with pHs of 4.0–4.5 and a water table at 15–30 cm of depth. Chemical factors triggered a rapid transition from rich fen (pH > 6) to poor fen and bog (Ph < 5). The two most southerly peatlands are youngest, with basal dates of 4670 BP and 4230 BP.Sphagnumpeat accumulation at these sites started at 2620 BP and 1790 BP, respectively. Two sites located at intermediate latitudes have basal dates of > 5140 BP and 5020 BP, while the development ofSphagnum-dominated ecosystems dates back to ≈ 3100 BP and 3710 BP, respectively. The most northerly site has the oldest basal date (> 7870 BP), and the oldest date for the initiation ofSphagnumpeat accumulation (≈ 7000 BP). The younger age of the peat deposits in the four southern sites is due to warm and dry climatic conditions during the middle Holocene that prevented peatland development until after 6000 BP when the climate gradually became cooler and moister. Farther north the climate was cool and moist enough to allow peatland development during the early to middle Holocene. In three southern peatlands, the development into aSphagnum-dominated ecosystem took > 2000 years, while at the more northerly sitesSphagnumbecame dominant after < 1500 years.Key words:Sphagnum, peatlands, boreal, Holocene, clim

ISSN:0008-4026    

DOI:10.1139/b93-002

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Isolates ofAspergillus flavusbelonging to at least 12 vegetative compatibility groups were characterized by aflatoxin productionin vitro, morphology, and random amplified polymorphic DNAs. Aflatoxin B1production differed significantly among vegetative compatibility groups; closely related isolates were similar intoxigenicity regardless of geographic origin. Cladistic analysis of DNA polymorphisms was consistent with vegetative compatibility data. A previously described dichotomy between S and L isolates ofA.flavusbased on morphology and physiology was strongly associated with both vegetative compatibility groups and DNA polymorphisms. All S isolates formed a single clade, apparently derived from the L group. Southern hybridizations of eight DNA amplification products showed that comigrating bands amplified by the same primer were always homologous withinA.flavusbut were not always homologous betweenA.flavusand closely related species. Results suggest thatA.flavusis a species aggregate, that genotypes are dispersed over wide areas, and that aflatoxin production is more stable in nature than in culture.Key words: vegetative compatibility groups, random amplified polymorphic DNA, sclerotia, aflatoxin.

ISSN:0008-4026    

DOI:10.1139/b93-003

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Ultrastructural examination of cotton plants infected withVerticillium dahliaeshowed responses in the vascular tissue similar to those reported earlier in cotton infected withFusarium oxysporumf.sp.vasinfectum. Contact cells reacted vigorously to infection, but the nature of the response depended on the location of the cells. The majority of the contact cells adjacent to initially infected vessels showed a reorganization of the cytoplasm with the formation of an apposition layer, a partitioning of the central vacuole into smaller vacuoles, and the appearance of osmiophilic material that was secreted through the plasmalemma and deposited in the apposition layer and in the pit regions of the vessels. The remainder of the contact cells adjacent to initially infected vessels contained a degenerated cytoplasm but no fungal hyphae. Contact cells adjacent to secondarily infected vessels responded with increased cytoplasmic activity and the direct secretion of osmiophilic material into the vessel lumens where it accumulated to form aggregates of various sizes and shapes that occluded the vessels. The fungus in these vessels was coated and embedded in this secreted material.Key words: contact cells,Gossypium hirsutum,Gossypium barbadense, vascular wilt, vessel occlusion.

ISSN:0008-4026    

DOI:10.1139/b93-004

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Shoot cuttings were collected from 56 native poplars along 11 rivers and creeks in southwestern Alberta, a region wherePopulus angustifolia,Populus balsamifera(sspp.balsamiferaandtrichocarpa), andPopulus deltoïdesform a disectional, trispecific hybrid swarm. Cuttings were rooted and established in an irrigated nursery plot. After 3 years, stem diameters and heights were measured from 381 trees and whole shoots were harvested from 74 trees to establish a regression equation relating basal diameter and shoot wet weight. Shoot wet weight varied by more than an order of magnitude across the clones, andP.angustifoliaclones tended to grow more slowly than clones of the other two species. There was no significant correlation between shoot growth rate and the degree of hybridization, as determined by a prior multivariate analysis of leaf form that has been substantiated by chemotaxonomic data. Thus, the interspecific hybrids were not generally more vigorous than clones with leaf forms typical of the parental speciesP.deltoidesorP.balsamifera. Conversely, in the same environment, artificial hybrids ofP.deltoidesfrom Illinois andP.balsamifera(ssp.trichocarpa) from Washington expressed heterosis. It is theorized that introgressive genetic exchange accompanying the natural interbreeding of these three poplar species in southern Alberta minimizes their genetic distance, preventing heterosis.Key words: heterosis, hybridization, poplars,Populus, biomass.

ISSN:0008-4026    

DOI:10.1139/b93-005

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

To investigate the pattern of natural variation of jack pine (Pinus banksianaLamb.), 64 natural stands from northwestern Ontario were compared based on phenotypic variation of cone and needle morphology. Cone and needle traits were determined for 10 trees from each stand. Vegetation and soil data for the stands were determined following the procedures established by the Ontario Ministry of Natural Resources Forest Ecosystem Classification program. Climatic data for each stand were interpolated using a geographic information system based on 1951 to 1980 data for Ontario and Minnesota weather stations. Nested analyses of variance indicated that most of the variation was expressed between trees and within trees, with relatively little (1.6 – 18.9% depending on the trait) expressed between sampled populations. Discriminant analysis of cone and needle data indicated that the 64 populations generally varied longitudinally with a steep cline in the Nipigon area (ca. 88°15′W) apparent for cone data. A corresponding irregularity in the pattern of needle variation suggested that the modern pattern may be the result of separate lineages, i.e., descendents from two migration routes along eastern and western shores of Lake Superior or from two refugia. However, temperature data follows a similar pattern in this area of Ontario, and multiple regression of the discriminant analysis score means for the 64 sampled populations against elevation, climatic, and soil data indicated that much of the cone and needle variation expressed between populations could be accounted for by the regressions. Thus, the observed patterns of phenotypic variation may simply be the result of local adaptations to a variable environment.Key words: jack pine,Pinus banksiana, phenotypic variation, cone traits, needle traits, northwestern Ontario.

ISSN:0008-4026    

DOI:10.1139/b93-006

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Analyses of partial rDNA sequences from both the small and large subunit genes of species ofCeratocystiss.l. support the contention that species that lackChalaraanamorphs, are resistant to cycloheximide, and have rhamnose in their cell walls should be assigned toOphiostoma, whereas only species withChalaraanamorphs should be accommodated inCeratocystiss.s. The data also show thatCeratocystiopsisis polyphyletic, andSphaeronaemella fimicolaappears to have little relation to eitherCeratocystisorOphiostoma.Key words:Ceratocystis,Ophiostoma, phylogeny, partial rDNA sequences.

ISSN:0008-4026    

DOI:10.1139/b93-007

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The effect of environmental factors on the germination of exhumed seeds ofSpergula arvensisL. after variable periods of burial in soil was investigated. Seeds were buried in the field and exhumed at regular intervals after which germination was tested over a range of conditions. These tests showed clear seasonal changes in dormancy during 3 successive years. Dormancy was broken in spring and reinduced in autumn at rising and falling temperatures, respectively. In experiments in incubators, greater loss of dormancy occurred at 10 and 15 °C than at 2 and 6 °C. As in the field, induction of dormancy occurred when the preincubation temperature was lowered. The expression of the dormancy pattern was strongly influenced by the germination tests conditions. At 15 °C, seeds germinated during a longer period of the year than at 2 or 30 °C. Irradiation with red light, addition of nitrate, and desiccation of the seeds prior to the germination test strongly stimulated germination. All three factors enabled germination of exhumed seeds during a longer period of the year. When light, nitrate, and desiccation were combined, exhumed seeds could germinate in all seasons. The seasonal germination pattern was modelled with a descriptive model based on the dual effect of temperature, which regulates dormancy and also affects germination. This model closely simulated germination at field temperatures. Germination of exhumed seeds in the field was restricted to the period of overlap between the germination temperature range computed with the model and field temperature. The features of the model supported the hypothesis that dormancy ofS.arvensisis regulated by the actual changes in temperature rather than the combined effects of a cold and heat sum.Key words:Spergula arvensis, dormancy pattern, germination, regression model, weed seeds.

ISSN:0008-4026    

DOI:10.1139/b93-008

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The development of the flower ofRosa setigerafrom initiation to the onset of anthesis is described.Rosa setigerais the only known member of the genusRosato exhibit dioecy. Flowers of functionally staminate (male) and functionally carpellate (female) plants appear identical, a condition referred to as cryptic dioecy. Discrete sepals and petals are formed on the floral meristem. As the hypanthium forms, stamens are initiated in alternating whorls on the wall of the hypanthium and continue to develop as the hypanthium extends. Carpel primordia arise individually on the remainder of the floral meristem and show neither adnation to the hypanthial wall nor coalescence to one another as they give rise to the styles and stigmas that are exserted above the hypanthium lip. The only observable fusion in this species appears to be the postgenital fusion of the margins of the carpel primordia to form the enclosed locule. Although historically the hypanthium has been variously interpreted as either axial and (or) appendicular in nature, resulting from congenital fusion of sepals, petals, and stamens, this paper uses a more realistic, testable and functional approach to the development of the hypanthium that is in keeping with current concepts such as process morphology.Key words:Rosa setigera, dioecy, floral development, fusion, hypanthium.

ISSN:0008-4026    

DOI:10.1139/b93-009

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The potential of utilizing induction and quenching kinetics of chlorophyllafluorescence as consistent and reliable markers forin vivosalt (sodium sulphate) tolerance screening studies was investigated by comparing two wheat (Triticum aestivumL.) varieties with varying responses to salinity, viz. Kharchia-65 (salt-tolerant) and Fielder (salt-susceptible). Three-week-old seedlings were treated with a range of salt concentrations (0 to 2%) over a 1- to 2-week period. Both the maximum rates of fluorescence induction and quenching measured from leaf sections decreased significantly in Fielder compared with Kharchia-65 as the salt concentration increased. Alterations in other fluorescence parameters, such as the maximum yield of fluorescence signal in the absence and presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea by the variety Fielder indicated a minimal reduction in the size of the primary electron acceptor pool associated with photosystem II following salt stress. In contrast, these parameters were altered to a lesser extent by salt treatments in Kharchia-65. The effect of salinity stress on leaf morphology of both varieties indicated no major anatomical alterations apart from a negligible increase in leaf thickness. Total chlorophyll content of Kharchia-65 increased significantly as a result of salt stress, owing to an increase in both chlorophyllaand chlorophyllb, whereas Fielder showed no significant variations. The results indicate that total fluorescence quenching and maximum rates of both induction and quenching appear to be reliable indicators forin vivoscreening of salt-tolerant wheat genotypes.Key words:Triticum aestivumL., wheat, chlorophyllafluorescence, salt stress,in vivoscreening.

ISSN:0008-4026    

DOI:10.1139/b93-010

出版商:NRC Research Press    

年代:1993

数据来源: NRC