摘要:

Gametophores from mixtures of the closely relatedSphagnum fallax(H. Klinggr.) H. Klinggr. andSphagnum isoviitaeFlatberg, from two localities were clonally propagated in axenic culture and back transplanted from laboratory to field conditions, as well as reciprocally transplanted between the same localities. Genetic and environmental effects on leaf morphology were estimated to assess the taxonomic merit of these characters. Differences between populations exceeded between-taxon differences and could not be taken as evidence of two separate species. Plastic responses were apparent in the reciprocal transplant experiment, and a species-specific norm of reaction could be discerned in one character. Compared with the field experiments the species- and population-level genetic variances increased in the laboratory. This indicates that increased differences between species and populations were an artefact of experimental conditions, rather than caused by environmental effects opposing genetic effects on morphology in the field. Among-clone variances remained relatively stable across all experiments, as did residual variances indicating that the clonal propagation process did not elevate developmental noise. Contrasting responses between clonally propagated and field collected gametophores provide indirect evidence of changing levels of genetic and plastic variation throughout ontogeny.Key words: cultivation experiment, phenotypic plasticity, phenetics,Sphagnum, morphology.

ISSN:0008-4026    

DOI:10.1139/b98-189

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Among the mycorrhizal types of spruce,Tylospora-type mycorrhizae are the most constant and abundant. Two species of the genusTylosporaoccur in Europe,Tylospora fibrillosaandTylospora asterophora. Mycorrhizae ofT. asterophoraare described in detail for the first time. Sequences of the internal transcribed spacer (ITS) of the ribosomal genes were obtained fromT. fibrillosaandT. asterophoramycorrhizae, sporocarps, and cultured mycelium. Discrimination and identification of the two species by ITS polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) are discussed in the light of inter- and intra-specific variability. Species-specific PCR primers were designed to distinguish both species. Molecular screening ofTylospora-type mycorrhizae from field material led to unambiguous results, whereas morphological identification is likely to fail because of great similarity even at the microscopic level.Key words:Tylospora asterophora,Tylospora fibrillosa, ectomycorrhizae, taxon specific primers (TSOPs), ITS sequences.

ISSN:0008-4026    

DOI:10.1139/b98-182

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Naturally regenerating hybrid spruce seedlings (Picea glauca(Moench) Voss betaPiceaengelmanniiParry) were collected from sites near Mackenzie, Salmon Arm, and Williams Lake, British Columbia, Canada. Bacteria were isolated from roots and screened in greenhouse trials for their ability to enhance spruce growth. Three strains belonging to the genusPseudomonaswere selected for study based on their disparate geographic origins and their capacity to consistently stimulate spruce seedling growth in screening trials. Factorial experiments were performed in the greenhouse to evaluate the effectiveness of thesePseudomonasstrains with different spruce ecotypes. Factors tested were spruce seed sources,Pseudomonasisolates, and forest floor soils originating from different sites. Three levels of each factor were studied: one spruce seedlot, onePseudomonasisolate, and one forest floor type each originated from a site at Mackenzie, Salmon Arm, and Williams Lake, British Columbia. Fourteen weeks after treatments were established, spruce biomass accumulation was greatest when spruce ecotypes were inoculated with bacteria originating from the same geographical area as spruce seed. However,Pseudomonasstrains originating from sites other than the seed collection area also stimulated seedling growth significantly, rendering the difference in growth promotion between bacterial treatments small and insignificant. In addition, spruce growth promotion was not enhanced when seed was treated with combinations ofPseudomonasstrains and forest floor soils originating from the same forest ecosystem. We conclude that specificity between spruce ecotypes and plant growth-promoting rhizobacteria strains can be detected under carefully controlled conditions, thereby supporting the hypothesis that growth-promoting bacteria may adapt to their plant hosts. However, the growth advantage accruing to seedlings treated with bacteria originating from the same ecosystem is small and suggests that it is not necessary to matchPseudomonasstrains with spruce ecotypes and soil types for effective seedling growth promotion.Key words:Pseudomonas, spruce, specificity, growth promotion.

ISSN:0008-4026    

DOI:10.1139/b98-197

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The structure of tracheid cell walls in mild compression wood ofPinus radiataD. Don was examined by confocal laser scanning fluorescence microscopy (CLSM) and transmission electron microscopy (TEM). Fluorescence microscopy using lignin autofluorescence revealed cell to cell variations in lignification of the cell corner middle lamella (CCML) and outer S2 (S2L) regions supporting observations made at higher resolution with TEM. The mild compression wood sample examined lacked the characteristic intercellular spaces of most grades of compression wood and thus represents the least severe grade of compression wood. TEM observations revealed evidence for radial striations in the S2 region probably representing regions of alternating high and low lignin concentration, which may be the precursor to the helical cavities found in severe compression wood. These radial striations typically showed a sinuous and branched structure, extending partly into the S2Lregion, where the orientation of lignin lamellae was predominantly tangential following the arrangement of the cellulose microfibrils. At high magnification lignin occurred in a patchy distribution overlaying the typical lamellate arrangement associated with normal wood. Significant variability in the lignification of the CCML region was also observed sometimes giving a patchy or granular appearance. The lignification of the CCML and the S2Lregions was generally comparable, while S1 and S2 layers were less lignified. A residual S3 layer was sometimes present in the form of a very thin layer slightly more lignified than the adjacent S2 layer.Key words: compression wood,Pinus radiataD. Don, ultrastructure, confocal laser scanning microscopy, transmission electron microscopy, lignin distribution.

ISSN:0008-4026    

DOI:10.1139/b98-184

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Lignin distribution in the tracheid cell wall of mild compression wood inPinus radiataD. Don was examined by interference microscopy, confocal fluorescence microscopy, and ultraviolet (UV) microscopy. Two anatomically different samples of mild compression wood were compared with a sample of normal wood using quantitative interference microscopy and microdensitometry combined with confocal fluorescence microscopy to estimate the quantitative or semiquantitative lignin distribution in the S2 and S2Lregions of the secondary cell wall and of the cell corner middle lamella (CCML). One of these samples was briefly examined by UV microscopy for comparison. Quantitative interference microscopy provided information on lignin concentration in different regions of the cell wall with values of 26, 46, and 57%, respectively, for the S2, S2L, and CCML regions of sample 1 and 20, 29, and 46%, respectively, for the same regions of sample 2. Microdensitometry of confocal fluorescence images provided semiquantitative information on the relative lignin distribution based on lignin autofluorescence. Comparison between the two compression wood samples using autofluorescence gave results that were in partial agreement with interference microscopy with respect to the relative lignification levels in the S2, S2L, and CCML regions. Some improvement was achieved by using calibration values for hemicellulose rather than holocellulose for interference data in the S2Lregion. Results for UV microscopy performed on sample 1 indicated that the lignification of the CCML region was comparable with that of the S2Lregion in this sample but with some variation among cells. All three techniques indicated significant variation in lignification levels of the S2Land CCML regions among adjacent cells and a significant reduction in the lignification of the CCML region compared to normal wood.Key words: lignin distribution, interference microscopy; confocal fluorescence microscopy, UV microscopy, mild compression wood,Pinus radiataD. Don.

ISSN:0008-4026    

DOI:10.1139/b98-190

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

We carried out a cytogenetic and isozymic study ofArtemisia molinieriQuézel, Barbero, & R. Loisel (Asteraceae, Anthemideae), a narrow endemic species limited to two populations in southeastern France. Fine karyotype analysis, including fluorochrome banding, enabled us to discuss the systematic affinities of this taxon, which is closely related toArtemisia abrotanumL. andArtemisia chamaemelifoliaVill. Isozyme electrophoresis showed higher genetic variability than expected for a plant with a very restricted geographic distribution. These data, along with the results of a study of pollen viability and some ecological factors, led us to propose some ideas concerning the conservation strategy for this rare plant species.Key words:Artemisia molinieri, Asteraceae, cytogenetics, isozyme variability, systematics, conservation, narrow endemic species

ISSN:0008-4026    

DOI:10.1139/b98-193

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The development of female gametophytes and embryos in relation to cumulative growing degree-days was followed to see if the postulated cooling influence of the Robert-Bourassa reservoir (LG2, northern Quebec) slowed the reproductive process of black spruce (Picea mariana(Mill.) B.S.P.). During the 1996 growing season, three to five developing seed cones were harvested 11 times on nine trees distributed along a shore-hinterland gradient of the northern shore of the reservoir. The daily thermal sum (degree-days > 5°C) in the seed cone zone of the same trees was also monitored to describe the female gametophyte and embryo development of this species as a function of heat sum. The 23 developmental stages identified in this study confirm that the female gametophyte and embryo ofP. marianadevelop according to the same pattern exhibited by otherPiceaspp. These stages, although unequal in duration, succeeded each other according to a sigmoid function of the temperature sum. Direct temperature measurements taken 0, 25, and 100 m from the shore of the Robert-Bourassa reservoir suggest the interior trees experienced 107 more degree-days > 5°C than the shoreline trees during seed maturation. Although gametophyte development of the shoreline trees was delayed early in the growing season (Kruskall-Wallis,p= 0.05), this delay does not persist afterward. Despite the net cooling effect of the Robert-Bourassa reservoir, all studied trees achieved embryo maturation in 1996. During this growing season, the warmest since 1977, it took embryos 800-940 degree-days to mature. The shoreline trees reached this temperature threshold later than interior trees. It is suggested that the cooling effect of the Robert-Bourassa reservoir could contribute to the inhibition of embryo maturation in shoreline trees during growing seasons with less than 800 degree-days.Key words: black spruce, climate change, cone development, northern boreal forests,Piceamariana, seed maturatio

ISSN:0008-4026    

DOI:10.1139/b98-198

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The influence of UV-B radiation on superoxide dismutase (SOD, EC 1.15.1.1) with reference to the activity and types of isoenzymes was studied in leaves of C3plants (potato,Solanum tuberosumL. cv. Désirée, and wheat,Triticum aestivumL. var. Almansor) and C4plants (maize,Zea maysL. var. LG12, and sorghum,SorghumPr 8515 Pioneer). Plants were grown under controlled conditions in growth chambers with and without UV-B radiation. After 10 days of irradiation it was found that UV-B affected both the total activity of SOD and the number and amount of isoforms in all plants. The total specific activity of SOD increased significantly in wheat, maize, and potato, whereas a decline was induced in sorghum. Native gels revealed that UV-B caused preferential changes of the SOD isoforms in all plants used. Inhibition studies with cyanide and hydrogen peroxide showed that, in maize, UV-B radiation caused a large accumulation of one Mn-SOD and in contrast the level of the Cu,Zn-SOD isoforms decreased. In potato leaves, UV-B changed the pattern of SOD isoenzymes causing the appearance of one isoform and the disappearance of another. In wheat and sorghum the pattern of the isoenzymes was not altered, only their relative amounts. The rise in SOD activity in maize, potato, and wheat is possibly correlated with the tolerance of UV-B ascribed to these crops by different researchers and the sensitivity of sorghum to UV-B is possibly associated with the decrease in SOD activity.Key words: superoxide dismutase, UV-B, maize, potato, sorghum, whea

ISSN:0008-4026    

DOI:10.1139/b98-195

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Genotypic variability of the symbiotic nitrogen fixation ability onAcacia cyanophyllaLindl. The phenotypic and functional characteristics of four rhizobium strains isolated from nodules ofAcacia cyanophyllaLindl., syn.Acacia saligna(Labill.) H. Wendl., and the inoculated host-plant genetic variability were evaluated. The evaluation used permitted the ranking of the tested rhizobium strains and seedlots according to their performance. The growth pattern of these strains indicated thatA. cyanophyllawas able to nodulate and fix N2with slow- and fast-growing rhizobium strains. The acetylene reduction activity test reflected a variable effectiveness of the strains depending on their site of isolation. Strains RFH383 and RFH483 were more effective than RFH183 and RFH283. The high antibiotic resistance acquisition by RFH183 and RFH283 strains seemed to be inversely related to their effectiveness.Acacia cyanophyllaseedlings from five seedlots displayed a high variability regarding their growth, nodulation, and ability to fix nitrogen. The ability to fix nitrogen was greater in the seedlings from KL seedlot than those from EN, KR, and TZ seedlots. The qualitative assessment of the seedlots using correspondence factorial analysis showed that the seedlings from KL seedlot preformed better than those from KR and TZ. The seedlings from TN and EN seedlots displayed an intermediate behaviour pattern. Seed origin seemed to affect the growth, nodulation, and nitrogen fixation of inoculatedA. cyanophylla. The behaviour of this species and that of its associated rhizobium strains appeared to be very sensitive to variations in site characteristics. Results suggested that the association between plants derived from KL seedlot and RFH383 strain may represent the best partnership allowing the improvement of symbiotic nitrogen fixation.Key words:Acacia cyanophylla, rhizobium, nodulation, N2fixation, genotypic variability, correspondence factorial analysis.

ISSN:0008-4026    

DOI:10.1139/b98-200

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Two new species ofAscotaiwania,A. persooniiandA. hughesii, collected from submerged decorticated wood in lotic and lentic habitats, are described and illustrated. The anamorph forA. hughesii,Helicoon farinosum, is confirmed by cultural studies.Ascotaiwania hsiliois reported for the first time from North America.Key words: Amphisphaeriaceae, aquatic, lignicolous, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b98-202

出版商:NRC Research Press    

年代:1999

数据来源: NRC