摘要:

To investigate the influence of insularity on plant reproductive biology at a local geographic scale, we examined aspects of reproduction in distylousPrimula mistassinicaMichx. (Primulaceae) on Lake Huron shorelines of the Bruce Peninsula and adjacent Tobermory Islands in Ontario, Canada. A total of 7 mainland and 13 nearshore island populations were compared. Controlled pollinations demonstrated thatP. mistassinicapossesses a dimorphic incompatibility system with intermorph crosses setting significantly more seeds than self or intramorph crosses. Floral morphology, population style-morph ratios, and seed fertility were compared in mainland and nearshore island populations to determine whether there was evidence for differences in reproductive traits between these areas. Style-morph ratios did not differ significantly from equilibrium expectations, and there were no consistent differences between island and mainland populations in floral morphology or fertility. Rather, the generalized pollination system ofP. mistassinicaand extensive historical opportunities for colonization appear to have mitigated insular effects so that proximate ecological factors are more relevant to the current reproductive biology of populations.Key words: distyly, insularity, pollination, reproductive biology.

ISSN:0008-4026    

DOI:10.1139/b98-150

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The cytokinin,N6-benzylaminopurine (BAP), when applied to young inflorescences of wild-typeAntirrhinum majusL., resulted in the formation of chimeric "filamentous structures" in the dorsal region of the third whorl, the position where a stamen primordium is suppressed in wild-type flowers. In addition, BAP induced similar filamentous structures in between the first and second whorls, and this response was concentration dependent. The basal region of the filamentous structures was similar to the filament of a stamen, while the distal portion resembled a petal. These observations suggest that cytokinins may be site-specific factors involved in the regulation of floral organ identity genes or genes that control floral symmetry, i.e., theCYCLOIDEAgene.Key words:Antirrhinum, benzylaminopurine, cytokinin, filament, floral genes, staminode.

ISSN:0008-4026    

DOI:10.1139/b98-152

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In the present work it is found that protoplasts of the radish tuber with a disorganized cytoskeleton, thus dead, subjected to a hypotonic shock, obey the law of osmosis, while healthy ones absorb 6% more water. This means that some events related to metabolism are responsible for this difference. Furthermore, stimulating metabolism, by action on the Krebs cycle, results in absorption of water, while slowing it with an inhibitor of oxydative phosphorylation results in loss of water by the cells. It is concluded that a hydraulic control of turgor, modulated by the intensity of respiration, exists in these cells. This is probably due to a mechanism similar to that of osmoregulation. We call it hydroregulation.Key words: osmoregulation, water intake, water excretion, turgor, hydroregulation.

ISSN:0008-4026    

DOI:10.1139/b98-140

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Although specialist pollination systems are often thought to be the outcome of selection, wide evidence exists for generalization within plant-pollinator interactions. We studied the pollination system and reproductive success ofCalluna vulgaris(L.) Hull over 3 years in an Upper Ardennes site in Belgium.A wide variety of insect visitors was recorded including Hymenoptera, Diptera, and Lepidoptera. Relative abundance of families and species of visitors varied markedly among years except for bees. Bumblebees and honeybees were the most efficient pollinators at the study site. Syrphid flies, mainly large ones, acted as important co-pollinators because of their high relative frequency.Callunapollen was also dispersed by wind, and insect-exclusion experiments demonstrated that wind pollination contributed to reproductive success. Following open pollination, fruit set was high, ranging from 82.0 to 97.2% and independent of sampling location. Mean seed number per fruit was less than maximum potential seed number and varied strongly among sampling locations. We discuss this pollination system (generalist insect and wind) in terms of the ecological and geographical success of the species.Key words:Calluna vulgaris, pollinator visitation, insects, wind pollination, reproductive success.

ISSN:0008-4026    

DOI:10.1139/b98-133

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The results of three studies at different stages of branch development demonstrated the importance of apical control of diameter growth in both stem formation and branch angle. Diameter growth is controlled by competition between branches and the stem for branch-produced photosynthate. Apical control of branch angle occurs only in species that can produce differential growth stresses. In those species, upward bending is largely regulated by the amount of branch diameter growth. The first study followed stem formation from current shoots inKalmia latifoliaL., a shrub without terminal buds or apical control of branch angle. When several current or older shoots were competing, the longest, most distal lateral shoot usually became the stem. Shoot angle was poorly correlated with eventual dominance. A more proximal lateral shoot on the underside of a leaning parent became the longest, dominant lateral in 24% of the parent shoots. The second study used stem girdles to test the hypothesis that the subjacent stem competes with the branch for branch-produced photosynthate. Results fromPinus strobusL. supported the hypothesis, but results fromBetula lentaL. andAcer rubrumL. did not. The third study removed apical control from branches of six forest-shrub species by cutting off the stem above the branch. Branches of all species increased diameter growth after cutting the stem, but only branches ofIlex verticillata(L.) Gray,Hamamelis virginianaL., andCornus amomumMill. developed differential growth stress and bent upward. Treated branches ofGaylusaccia baccata(Wang.) K. Koch,Viburnum cassinoidesL., andK. latifoliasagged as much as controls.Key words: apical control, diameter growth, branch angle, growth stress, reaction wood.

ISSN:0008-4026    

DOI:10.1139/b98-156

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A new species ofHalosarpheia,H. heteroguttulata, is described from wood submerged in streams and lakes in Australia, Brunei, Hong Kong, Mauritius, the Philippines, and South Africa. It differs from other species in the genus in ascospore dimensions, and consistently large guttule(s) in the apical cell, but many smaller guttules in the basal cell. The species is illustrated with light and scanning and transmission electron micrographs and compared with otherHalosarpheiaspecies.Key words: appendage ontogeny, freshwater Ascomycete,Halosarpheia, taxonomy, ascospore ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b98-163

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Howell's failure in 1898 to typifyCrataegus columbianaHowell (the species is based on noncited discordant paratype elements) and the readiness of later authors to make new varieties in this species without resolving the type problem has been the cause of much confusion in the nomenclature of the western red-fruited hawthorns. This has been increased by the failure to recognizeCrataegus williamsiiEggl. and compounded by almost a century of no revisionary study on westernCrataeguswith the further result that boundaries between taxa have been routinely misunderstood outside Colorado. In pursuit of a solution doing least violence to conventional usage I have lectotypifiedC. columbianaand resuscitatedCrataegus piperiBritton (in a recent paper), realignedC. piperiasCrataegus chrysocarpavar.piperi(Britton) Eggl. and resurrectedC. williamsii. There are thus five established native western species of red-fruited hawthorns, the above two, andCrataegus wootonianaEggl.,Crataegus macracanthaLodd. ex Loud. andCrataegus erythropodaAshe in addition to the introducedCrataegus monogynaJacq., all of which have been recognized as occurring at least somewhere in this region for many decades. This paper also adds the first authenticated record for wildCrataegus laevigata(Poir.) DC. in North America. Separation of the two varieties ofC. chrysocarpais validated by numerical taxonomy. The taxa concerned are illustrated with line drawings and provided with detailed range maps. Colour photographs illustrate typical habitat types and show the development of fruit colour.Key words: systematics,Crataegus, Rosaceae, red-fruited, western North America.

ISSN:0008-4026    

DOI:10.1139/b98-148

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Oak wilt is a fungal tree disease that has killed millions of live oaks (Quercus fusiformisSmall) in the oak woodlands of central Texas. Allozymes were used to characterize the genetic structure of live oak populations prior to infection (pre-epidemic) and following passage of an epidemic wave (post-epidemic). Pre-epidemic trees (N= 112) were sampled along transects in front of an expanding disease front. Post-epidemic trees (N= 109) were survivors of an epidemic that swept through an area of approximately 28 ha over a period of 20 years. Significant differences in allele and genotype frequencies existed between pre- and post-epidemic populations. Gene diversity was lower for two of the four allozyme loci in the post-epidemic population. Departures from Hardy-Weinberg equilibria occurred for two loci and multilocus associations developed in the post-epidemic population. These results demonstrate that disease can have a significant impact on the genetic structure of a natural host population. We hypothesize that selection for increasing disease resistance was the dominant evolutionary force leading to genetic change in this plant pathosystem.Key words: host-pathogen interactions, population genetics,Ceratocystis fagacearum, coevolution.

ISSN:0008-4026    

DOI:10.1139/b98-142

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In plants of the perennial, deciduous herbTalinum triangulare, crassulacean acid metabolism (CAM) is induced by drought; therefore, CAM may be an adaptation to water deficit in this species. The present study was undertaken to determine the effects of water deficit on fecundity and CAM in plants ofT. triangulare. Plants were grown from seed in the greenhouse and the life table was constructed with dynamic cohorts. CAM was induced by drought in plants as young as 45 days old, and its induction was associated with a significant rise in fecundity; values of survival beta mean fecundity by age-class were 30-50% higher in plants subjected to drought than in control plants due to a rise in fecundity. Plants subjected to drought produced more and lighter seeds, which germinated faster than their watered controls. These characteristics could be advantageous for a colonizing species such asT. triangulare.Plants obtained from the germination of seeds of plants subjected to drought did not show higher values of nocturnal acid accumulation when subjected to drought than the droughted offspring of watered plants but they showed higher survival and an earlier and higher reproductive effort than plants obtained from the germination of seeds of watered plants. The fact that values of survival beta mean fecundity were higher in plants subjected to drought than in watered plants suggests, within the context of the life history, that characters associated with the CAM syndrome may be adaptive.Key words: fitness, inducible CAM, life table.

ISSN:0008-4026    

DOI:10.1139/b98-136

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

To evaluate the classification ofPhoma lingam(Tode:Fr.) Desm. andPhoma wasabiaeYokogi in the genusPhoma, a phylogenetic study ofPhomaspp. was conducted using ribosomal DNA internal transcribed spacer 1 sequences. The majority of thePhomaspecies included in the study clustered in aPhoma-Didymellaclade (Venturiaceae).Phoma lingamandP. wasabiaeconsistently clustered outside of thePhoma-Didymellaclade, instead forming thePlenodomusclade (Leptosphaeriaceae). This result supports classification ofP. lingamandP. wasabiaeinPlenodomusas has been proposed by earlier investigators. Features of the morphology and development of pycnidia ofPhoma americanaMorgan-Jones & White andP. lingamsuggest thatPhomaandPlenodomusmay also be distinguishable morphologically. Our results suggest that difficulties of identification and classification inPhomamay be resolved by using a phylogenetic approach to classification.Key words: Coelomycetes, molecular systematics, pathogens, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b98-154

出版商:NRC Research Press    

年代:1998

数据来源: NRC