摘要:

Substantial progress has been made towards the development of systems forin vitroembryogenesis in conifers. Since the first report of somatic embryogenesis from zygotic embryos ofPicea abiesin 1985, cultured explants of at least 18 different coniferous species have been induced to produce somatic embryos. Somatic embryos have been cryopreserved, grown in liquid suspensions, and matured into plants. In addition, plantlets have been regenerated from protoplasts isolated from embryogenic suspensions ofPicea glaucaandLarix×eurolepis, permitting studies into direct gene transfer and somatic hybridization. Currently however, it is only possible to obtain somatic embryogenesis from embryonic and juvenile explants. Furthermore, for most species the efficiency of plantlet production from somatic embryos is poor and remains a problem for the commercial utilization of this technology. Biochemical, cytological, and physiological studies of conifer somatic embryogenesis have resulted in improved knowledge concerning the origin of somatic embryos, storage product accumulation during embryo development, and similarities with zygotic embryos. Furthermore, the technique of indirect immunofluorescence microscopy has permitted investigations of the cytoskeleton in conifer cells and protoplasts, providing insights into cell division and morphogenesis. In this review, emphasis is placed on the more fundamental aspects of conifer somatic embryogenesis. Where possible, comparisons between zygotic and somatic embryogenesis are made.Key words: somatic embryogenesis, zygotic embryogenesis, conifers, review.

ISSN:0008-4026    

DOI:10.1139/b91-237

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Wheat and several nongramineous plant species, commonly used in rotation with wheat in southern and central Brazil, were examined for the presence of the wheat pathogensCochliobolus sativusandFusarium graminearum. Both fungi were isolated from residues of all the plant species, artificially inoculated and grown in a growth chamber, or grown outdoors exposed to inoculum in the form of infested sorghum grains. After harvest of outdoor plants, recovery was lower in 4-month-old residues than in 5-week-old residues. These fungi were also recovered from healthy and lesioned parts of many of these plant species collected in the field. Artificially inoculated nongramineous plants did not show any symptoms of infection and microscopic examination of inoculated leaves showed a resistant reaction toC.sativus.

ISSN:0008-4026    

DOI:10.1139/b91-238

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The putative speciesMedicago polyceratia(L.) Trautv. occurs in northwestern Africa, Iberia, and southern France. The putative speciesMedicago orthoceras(Kar. & Kir.) Trautv. occurs in southwestern USSR and Asia. Although separable by geography, morphological distinction has been problematical. On the basis of studies of herbarium specimens, seven characters were found to differ significantly between the two species. The most useful of these, a previously unappreciated character, substantially discriminated the species: fruits ofM.polyceratiararely have less than 35 veins intersecting the longitudinal axis of the fruit valve, whereas those ofM.orthocerasrarely have more than 35. This character also differed significantly between African and EuropeanM.polyceratia.Key words: taxonomy, Leguminosae,Medicago polyceratia,Medicago orthoceras,Trigonella.

ISSN:0008-4026    

DOI:10.1139/b91-239

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Somatic embryos were induced directly on immature embryos ofCarica papaya×Carica cauliflorahybrids cultured on modified Murashige and Skoog's medium. When transferred to medium supplemented with abscisic acid, individual somatic embryos proliferated numerous daughter embryos through repeated embryogenesis. Light microscopic study of the repeatedly embryogenic cultures showed that daughter embryos arose from single superficial cells of parent embryos. Plant regeneration occurred following transfer of somatic embryos to medium devoid of plant growth regulators. Regenerated plants were intermediate betweenC.papayaandC.cauliflorain several morphological respects and showed isozyme patterns specific to both species as well as some new bands, indicating that they are indeed interspecific hybrids.Key words:Carica, interspecific hybrid, embryo culture, somatic embryogenesis.

ISSN:0008-4026    

DOI:10.1139/b91-240

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Fixation of atmospheric N2may provide an advantage to woody plants in N-limited environments, but may also alter their resistance to herbivory. Studies in adjacent plantings of three North American shrub alders (Alnusspp.) and three Eurasian tree alders showed significant species differences in susceptibility to a leaf-mining sawfly (Fenusa dohrnii) and in response to inoculation with a N2-fixing actinomycete (Frankia). During the first 5 years, woody biomass production ranged from 0.3 t∙ha−1∙year−1inAlnus viridisssp.sinuata(Sitka alder) to 8.3 t∙ha−1∙year−1inAlnus incanassp.incana(grey alder). Grey alder and another tree species (Alnus japonica) were attacked infrequently and suffered little sawfly damage except in plots with poor growth. The tree speciesAlnus glutinosa(black alder) was attacked frequently, and sawfly damage was greatest in plots with the best growth. The shrub speciesAlnus viridisssp.crispa(green alder) was also attacked frequently but was highly resistant to larval feeding. Frequently attacked species showed greater damage in the lower portion of the crown.Frankiainoculation increased green alder biomass by 87% but had no significant effect on grey alder or black alder. The concept of a growth-defense trade-off does not fully explain the interactions betweenAlnusspp. andF.dohrnii.Key words:Alnus,Fenusa dohrnii,Frankia, biomass production, plant–herbivore interactions, lea

ISSN:0008-4026    

DOI:10.1139/b91-241

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The ability of 28 monokaryons and 78 reconstituted dikaryons ofPisolithussp. from South Africa to form mycelial strands in association withPinus pinasterwas tested under aseptic and non-aseptic conditions. All monokaryotic and some dikaryotic cultures failed to form mycelial strands either on agar medium or in growth pouches. The remaining dikaryotic cultures showed wide genetic variation in the development of mycelial strands and in the extension of their extramatrical phase. The exploration of the surrounding environment by the extramatrical phase from synthesizedPinus pinaster– dikaryotic cultures of thePisolithussp. depended largely upon the type of medium used, being more extensive in soil than on nutrient agar medium. Microscopic observation showed that mycelial strands were formed by aggregations of hyphae. Large central hyphae with disorganized cytoplasm were observed in some strands. The results are discussed in relation to nutrient and water absorption.Key words:Pisolithussp.,Pinus pinaster, genetic, extramatrical phase, mycelial strands.

ISSN:0008-4026    

DOI:10.1139/b91-242

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Features of foliar and stem anatomy of 26 annual and 1 perennial species of North AmericanAgaliniswere examined from over 200 population samples. Several species includingA.aphylla,A.densiflora,A.filicaulis,A.heterophylla,A.linifolia,A.maritima, andA.oligophyllahave distinctive anatomy. Evidence from anatomy supports a reclassification of North AmericanAgalinisat the sectional and subsectional ranks.Agalinis aphyllaandA.oligophyllaare allied with species of sectionErectae, not sectionPurpureaesubsectionSetaceae.Agalinis edwardsiana(from sectionTenuifoliae) andA.aspera(sectionAsperae) are most similar to members of sectionPurpureaesubsectionPedunculares.Agalinis tenuifolia(sectionTenuifoliae) is similar to species of sectionPurpureaesubsectionPurpureae. Anatomical characters range from those usually regarded as xeromorphic to those typical of hydromorphic species. However, different xeromorphic characters are present in species of sectionsPurpureae,Erectae, andTenuifoliae. Species of sectionPurpureaesubsectionSetaceaehave filiform, adaxially grooved leaves; species of sectionErectaehave narrow, short sclerenchyma-reinforced leaves and very slender stems usually having fiber bundles in their ridges. Species that we retain in sectionTenuifoliaehave a cylinder of sclerenchyma between the vascular tissues and the fiber-laden cortex.Key words:Agalinis, Scrophulariaceae, anatomy, systematics, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b91-243

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Individual twigs of eastern hophornbeam were experimentally defoliated at the time of spring peak herbivore abundance for this plant species. When all three leaves directly subtending developing fruits and all leaves (three to five total) from the nearest twig were removed to simulate natural folivory, there was a 25% decrease in mass of individual fruits (but not in fruit number) compared with control twigs. Lower damage of up to 50% area removal for subtending and nonsubtending leaves combined produced no significant decrease in reproductive output. Experimental defoliation had no effect on growth, reproduction, or survivorship of treatment twigs in the subsequent year. At no time during the study was natural herbivore damage high enough on individual twigs to decrease their reproductive output. These results add to the evidence that resource movement among adjacent twigs and branches of woody plants is not sufficient to compensate for localized damage. Thus, we must consider both the pattern of folivory as well as total leaf area removed to understand the effects of folivorous insects on plant growth and reproduction.Key words: folivory,Ostrya virginiana, physiological integration, plant reproduction.

ISSN:0008-4026    

DOI:10.1139/b91-244

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Cauliflory, flowering on older branches or trunks of woody plants, inCercis canadensiswas studied using light and scanning electron microscopy and macroscopic bud counts. A linear series of up to 10 floral buds are initiated in the axil of the foliage leaf before stem elongation is completed. These buds sequentially mature into first-order inflorescences over a 5-year period. Although an individual inflorescence flowers only once, second-order reproductive buds are formed in the axils of the basal bud scales of the inflorescence and can produce third-order reproductive buds. Buds and the bases of abscised inflorescences form wens, which are macroscopic swollen areas along the stem, corresponding to the original orthodistichous phyllotaxy. Branching of primary vascular tissue in a wen indicates a continuum of vascular connections between reproductive buds and the vascular traces to the inflorescences can be followed to the pith. The wens often produce epicormic shoots that are themselves cauliflorous with first-order reproductive buds formed in their leaf axils. The shoots usually abscise above the first-order reproductive buds at their base. These buds, along with the higher order reproductive buds, perpetuate the cauiflorous condition throughout the life of the plant.Key words: axillary buds, cauliflory,Cercis canadensis, epicormic shoots, wens.

ISSN:0008-4026    

DOI:10.1139/b91-245

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The 18S-like rRNA sequences of four recently isolated strains of rumen anaerobic phycomycetes (Neocallimastix frontalisMCH3,Piromonas communisFL,Sphaeromonas communisFG, andNeocallimastix joyoniiNJ1) were analyzed and compared to examine the phylogenetic relatedness of the four isolates to each other and to other eukaryotes. The rumen chytrids characterized demonstrated very high 18S-like rRNA sequence similarities (97–99%). They are more closely related to the true fungi than to any other eukaryotes.Key words: phylogeny, anaerobic fungi, rumen, chytrids, Chytridiomycetes,Neocallimastix.

ISSN:0008-4026    

DOI:10.1139/b91-246

出版商:NRC Research Press    

年代:1991

数据来源: NRC