摘要:

In studies of the inorganic carbon (Ci) concentrating mechanism of cyanobacteria glycolaldehyde is often used to inhibit photosynthetic CO2fixation. As a partial inhibition of active CO2transport by glycolaldehyde under steady-state Ciflux conditions has been recently suggested, in this paper, using mass spectrometry, we investigate in detail the relationship between glycolaldehyde concentration ([GLY]) and CO2transport both during the initial period following illumination of a cyanobacterial cell suspension and during the so-called steady state when an internal Cipool has been allowed to develop. Carbon dioxide uptake following illumination of a cyanobacterial cell suspension was progressively reduced by increasing [GLY] in the medium, both in the absence or in the presence of carbonic anhydrase. The same features were found when either Ciin the form of bicarbonate was injected to a pre-illuminated cell suspension in the presence of carbonic anhydrase in the medium or a pulse of CO2was provided to the cells in the light without carbonic anhydrase in the extracellular medium. Although photosynthesis was completely abolished with 10 mM glycolaldehyde, CO2uptake was only inhibited 20% but was decreased further by higher [GLY]. Double reciprocal plots of CO2uptake versus initial [CO2] determined with a range of [GLY] showed the inhibition to be noncompetitive. To simultaneously study CO2uptake and CO2efflux, H13C18O3was used with cells in which CO2transport alone, or both CO2and HCO3-transport system were allowed to proceed. Cells were inhibited with either iodoacetamide or glycolaldehyde and the time course of the various CO2species in the medium demonstrated that CO2uptake was inhibited partially with glycolaldehyde resulting in a greater CO2efflux from the cells. When the cell suspension was again illuminated, in the presence of glycolaldehyde, initial CO2uptake was greatly reduced, and the extracellular [CO2] eventually rose to a level higher than that which would be expected to be in equilibrium with the amount of Cipresent in the medium. Results are discussed in terms of glycolaldehyde use in Citransport mechanism studies in cyanobacteria.Key words:SynechococcusUTEX 625, blue-green algae, cyanobacteria, CO2transport, HCO3-transport, CO2efflux, inhibitor, Ciconcentrating mechanism.

ISSN:0008-4026    

DOI:10.1139/b97-154

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In Verzy forest (near Reims, France), seeds were sampled from some tortillard beeches (Fagus sylvaticaL. var.tortuosaPépin) after free pollination. After a dormancy breaking treatment performed in laboratory, seeds were sown in nursery and seedlings were cultivated for 4 years. The purpose of this study is to examine the fertility of tortillard beech and the occurrence of its phenotype during the first years of development. According to our experimental conditions, full and empty seed ratios, germination rate, and seedling annual survival rate were not significantly different from those reported for the European beech in literature. Among 486 tortillard maternal descendants, after 4 years, 25% of the individuals showed a special shape, characterized by reiterations, and could be considered as "tortillards". This phenotype appeared progressively during the second year of seedling development. The number of tortillards increased from one year to the next and their typical shape became more pronounced until they were 4 years old. These results show that the tortillard variety is no less fertile and vigorous than the European beech.Key words:Fagus sylvaticavar.tortuosa, morphology, growth, fertility, strength.

ISSN:0008-4026    

DOI:10.1139/b97-126

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

PetasitesMill. (Asteraceae: Senecioneae) is a taxonomically difficult genus of polygamodioecious, perennial clonal herbs distributed across Canada, Alaska, and the northern contiguous United States. The taxonomic confusion surrounding the genus is reflected in the ambiguity of the various classification systems currently used. As many as ten species and as few as two species have been recognized (Petasites sagittatus(Banks ex Pursh) Gray andPetasites frigidus(L.) Fries with three varieties), in addition to one hybrid taxon. To determine if discrete groups could be recognized according to a combination of vegetative and (or) reproductive characters and thereby clarify the phenetic relationships among the taxa ofPetasites, morphological data were subjected to principal components and discriminant analyses. Particular emphasis was placed onP. frigidusvar.frigidus,P. frigidusvar.nivalissensu Bogle, and the purported hybrid between these taxa, which exhibits an intermediate morphology (thefrigiduscomplex). Additionally, the specific status ofP. sagittatuswas investigated. Evidence obtained from multivariate morphometric analyses indicates that North AmericanPetasitesis comprised of four closely related polymorphic entities. While morphological variation among different taxa ofPetasitesis continuous for most reproductive characters, leaf characters were determined to be the most taxonomically discriminating. The entities of thefrigiduscomplex form a cohesive group somewhat distinct from the other taxa. The morphological differentiation betweenP. sagittatusand other taxa ofPetasitesis not considered sufficient to warrant recognition of specific status. Therefore, we recommend that only one polymorphic species ofPetasitesin North America be recognized (P. frigiduswith three varieties) in addition to one hybrid taxon originating from a cross between two of the varieties.Key words:Petasites, Asteraceae, North America, systematics, principal components analysis, discriminant analysis.

ISSN:0008-4026    

DOI:10.1139/b97-152

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The evolutionary significance of a mixed mating system is currently under debate.Calluna vulgaris(L). Hull, a widespread European shrub, is likely to undergo mixed mating because of geitonogamy. Mating system was investigated in three populations ofC. vulgarisby means of greenhouse controlled crosses, pollen tube observations, and outcrossing rate estimations from allozyme markers. The species is highly self-sterile, most probably as a result of early inbreeding depression. Mean fruit set and mean seed number per fruit following hand self-pollination were 48 and 13%, respectively, of those following cross-pollination. Pollen tubes produced by self pollen penetrated the ovary with the same success as those from cross-pollination. Multilocus estimates of the outcrossing rates ranged from 0.71 to 0.90, and two estimates were significantly different from 1.00.Calluna vulgariscould thus be classified as being mixed mating with predominant allogamy. Single-locus estimates did not differ significantly from multilocus estimates suggesting that biparental inbreeding did not contribute to the apparent selfing rate. The maintenance of high early inbreeding depression despite an intermediate level of selfing is discussed with respect to recent theories on mating system evolution.Key words:Calluna vulgaris, mating system, self-sterility, pollen tubes, outcrossing rate, inbreeding depression.

ISSN:0008-4026    

DOI:10.1139/b97-148

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

This study examined whether variation in reproductive allocation with size could be explained by differences in the trade-off between reproduction and growth. Seeds from 42 half-sibling families were collected from sites differing in mowing frequency and availability of light, nutrients, and water. Six seedlings from each family were grown in controlled environments and photoperiod manipulations were used to control reproduction. Mass of vegetative and reproductive plants of the same family were compared to assess the trade-off between reproduction and growth. Families collected from habitats with a tall canopy were larger and experienced a greater decrease in growth with reproduction than families from habitats where mowing maintained a short canopy. Reproductive output showed no relationship with size, while reproductive allocation (capsule mass to vegetative mass) decreased with size. This decrease may be a direct consequence of the increase in reproductive cost with size. The increase in cost can be partially explained by increased allocation to reproductive support structures; large individuals produce capsules on more elongate scapes and have a lower capsule to scape ratio. Differences in size and morphology among habitats are presumably the result of selection to avoid damage in mown sites and to avoid shade and ensure pollination in sites with a tall canopy and reduced wind movement.Key words: allometry, life-history theory, size constraints, reproductive effort, reproductive cost.

ISSN:0008-4026    

DOI:10.1139/b97-160

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Alkaline cupric oxide oxidation and proximate analysis were used to investigate the sources and diagenetic state of organic matter in sixSphagnum-dominated peatlands located between Alberta, Canada, and Ohio, U.S.A. Cupric oxide oxidation was also used to characterize vascular and nonvascular wetland plant species to provide a specific biological fingerprint of these plant tissues. Oxidation of 15 species ofSphagnummoss released large quantities of unsubstitutedp-hydroxyl phenolic compounds as well as the species specific sphagnum acid (p-hydroxy-&bgr;-[carboxymethyl]-cinnamic acid). By contrast, vascular plant tissues released large amounts of lignin oxidation products. Cupric oxide oxidation ofSphagnumpeat from more northerly sites produced mainlyp-hydroxyl phenolic monomers with lesser amounts of vascular lignin derived phenols. In contrast, southern sites and those dominated by woody vegetation produced oxidation products characteristic of vascular plant lignin. A distinct relationship exists between the amount of acid-insoluble Klason lignin and both the diagenetically sensitive phenolic acid to aldehyde ratios as well as the total yield of vanillyl phenolic oxidation products. We found evidence of selective decay of phenolic lignin precursors. These relationships indicate the lignin component in surficial layers ofSphagnum-dominated peat is influenced by bothSphagnumand vascular plant lignin, and the structure of lignin appears to undergo diagenetic changes in these layers. Application of an end-member mixing model revealed that lignin oxidation products poorly predicted vegetational composition of the lignin in more decomposed peat, probably as a result of selective decay of lignin structural phenols.Key words: lignin, organic soil, proximate analysis,Sphagnummoss, wetland.

ISSN:0008-4026    

DOI:10.1139/b97-150

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The role of branching on the development of size hierarchies was studied on experimental populations of the annual herbGalium aparineL. (Rubiaceae). All branches of plants growing at high and low density were severed as plants developed, and the growth of individual plants, the development of growth and size inequalities, and the mean change in the size ranking of plants over time were compared with those of populations of naturally branched plants. Size allometries were analysed for all treatments. The effect of the branch-severing treatment on growth and size inequalities was not significant for crowded populations. The position of individual plants in the ranking of weights in crowded conditions was less variable for populations of unbranched plants than for those of branched plants. Size and growth inequalities among branched plants were not significantly affected by population density. The hypothesis that branching increases the development of competitive hierarchies inG. aparinepopulations is not supported by the results. The role of height growth limitation in crowded conditions as a constraint to competitive hierarchy development is discussed.Key words: allometry, branching pattern, competitive hierarchy,Galium aparine, intraspecific competition.

ISSN:0008-4026    

DOI:10.1139/b97-159

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

To study virulence and aggressiveness in root-knot nematodes on cultivars of potato (Solanum tuberosumL., four isolates ofMeloidogyne haplaChitwood race A, one ofM. haplarace B, three ofMeloidogyne chitwoodiGolden et al., and two ofMeloidogyne fallaxKarssen were evaluated on 10 commercial potato cultivars under semisterile conditions in Petri dishes. Virulence and aggressiveness were assessed in terms of nematode reproduction by egg-mass index and reproduction factor, estimated by the number of egg masses and juveniles produced, respectively, divided by the number of juveniles inoculated. Significant interaction for both parameters was revealed between species ofMeloidogyneand potato cultivars. OnlyM. haplashowed significant isolate-by-cultivar interaction, which was predominantly caused by theM. haplarace B isolate Hh. This indicates variation in virulence and suggests the occurrence of different genetic factors for virulence and resistance inM. haplaisolates and potato cultivars, respectively. Despite large differences, the observed levels of resistance were too low to be of practical meaning for breeding, with the exception of resistance to isolate Hh. No significant differences were obtained between isolates ofM. chitwoodiandM. fallaxor isolate-by-cultivar interaction, indicating neither variation in aggressiveness nor in virulence in the isolates used. A comparative greenhouse experiment gave comparable results for egg-mass index but contradicting results for reproduction factor, most likely because of differences in life cycle, which appeared to be shorter inM. fallaxthan inM. haplaandM. chitwoodi. The Petri-dish method proved to be accurate for virulence studies of root-knot nematodes on potato culitvars.Meloidogyne fallaxwas most aggressive on potato, followed byM. chitwoodi,M. haplarace A, and finally byM. haplarace B.Key words: aggressiveness, biadditive model, biplot, plant breeding, resistance, virulence.

ISSN:0008-4026    

DOI:10.1139/b97-161

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Whitebark pine (Pinus albicaulis) is the sole North American representative ofPinussubgenusStrobussectionStrobisubsectionCembrae, a group of five species characterized by bird-dispersed seeds. Whereas population genetic structure has been described for several EurasianCembraepines, the purpose of the present research was to quantify genetic diversity in whitebark pine and assess the distribution of genetic variation within and among populations interpreted within the context of this species' unique life history. Allozyme analyses were conducted on nine populations from the Greater Yellowstone Area. Genetic diversity, as measured by population means for percentage of loci polymorphic, number of alleles per locus, and expected heterozygosity was relatively low (i.e., 38.57, 1.66, 0.152) when compared with means reported for pines with wind-dispersed seeds. Genetic differentiation was also low (i.e., 0.025) relative to means reported for other gymnosperms including wind-dispersed pines. These populations are poorly differentiated, with the majority of all observed variation due to differences among individuals within populations. The data reported herein for whitebark pine populations are similar to those reported for otherCembraepines and may reflect their recent evolutionary history, as well as life history, including documented bird dispersal of seeds.Key words: population genetic structure, plant evolutionary biology, bird dispersal,Pinusalbicaulis, Pinaceae.

ISSN:0008-4026    

DOI:10.1139/b97-162

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Population genetic parameters were estimated for six populations ofCronartium ribicolain western North America from British Columbia to the southern Sierra Nevada, and two outgroups from eastern North America, using isozyme, random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers on cultured haploid clones. Diversity was low, with only 8% polymorphism in the 212 markers identified. Each polymorphic locus had only two alleles, except for an RFLP marker in the ribosomal DNA complex with multiple alleles, that resulted from variable numbers of tandem repeats. Expected heterozygosity within populations, estimated from diploid teliospores, was only 0.025. The three types of markers were highly consistent with each other for these parameters. Yet, populations were highly differentiated; the proportion of the total variation attributable to differences among populations was 0.205. Multivariate statistical analysis as well as different clustering algorithms based on contrasting evolutionary assumptions (drift, mutation) all showed similar relationships and differences among populations. Genetic distances were not associated with geographic distances; western populations within a few kilometres of each other were often more distant from each other genetically than they were from eastern populations across the continent. The lack of pattern over the landscape of this metapopulation is consistent with aspects of the life cycle and epidemiological behavior of the pathogen, in which genetic drift appears to play a major role.Key words: white pine blister rust, isozymes, RAPDs, RFLPs, multivariate analysis, genetic drift.

ISSN:0008-4026    

DOI:10.1139/b97-167

出版商:NRC Research Press    

年代:1998

数据来源: NRC