摘要:

The levels of ammonia-assimilating enzymes ofIpomoeaspp. (morning glory) grown in suspension culture on a chemically defined medium are affected by various nitrogen sources. An increase in nitrate or ammonium concentrations in the growth medium elevated the levels of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. The levels of the enzymes varied in a manner similar to the growth pattern of the cells. When the growth rate ofIpomoeawas maximal, high levels of enzymes were obtained; when cell growth was poor, a low yield of enzymes was obtained. Glutamine, whether used as the sole nitrogen source or as a supplement in media containing ammonium plus nitrate, increased the level of glutamate dehydrogenase and decreased the level of the other two enzymes. The developmental pattern of glutamine synthetase activity with culture age inIpomoeadiffered with different nitrogen sources in the growth medium.

ISSN:0008-4026    

DOI:10.1139/b89-392

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Fifteen species ofTricholoma, subgenusTricholoma, sectionAlbidogrisea, are described and illustrated. All species occur in the Great Lakes region and many are distributed elsewhere in eastern North America. Four species are new:Tricholoma argenteum,Tricholoma atrodiscum,Tricholoma insigne, andTricholoma pullum. Keys are provided to the sections of subg.Tricholomaand to the species and stirpes of sect.Albidogrisea.

ISSN:0008-4026    

DOI:10.1139/b89-393

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Electron-opaque (EO) structures were studied, using light and electron microscopy, in the xylem parenchyma cells and vessels of both incompatible and compatibleApium graveolensL. var.rapaceum(celeriac) and compatibleApium graveolensL. var.dulce(celery) roots 24 h after inoculation withFusarium oxysporumf.sp.apiirace 2. Few small EO bodies were observed in the noninoculated hosts. Histological, cytochemical, and chemical tests indicated the presence of phenolic substances and polysaccharides in the EO materials. These EO structures increased both in number and size as infection progressed. The incompatible host produced three and five times more of the EO materials than the compatible celeriac and celery, respectively. The amount of the EO materials and host compatibility were related to the absence and presence of fungal hyphae in the vascular system. Hyphae either associated with or enveloped by the EO structures were vacuolated; their cytoplasm was restricted to the cell periphery. Occlusion of the xylem vessel pores of the incompatible host with the EO structures likely prevented upward spread of the pathogen throughout the entire plant.

ISSN:0008-4026    

DOI:10.1139/b89-394

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Rhizobiumstrain N31, isolated from the arctic legumeAstragalus alpinus, nodulates sainfoin (Onobrychis viciifolia) as efficiently as strain SM-2, isolated from sainfoin. Nodule shape and tissue arrangement of 70-day-old plants infected by these two strains were examined. Sainfoin nodules formed by either strain N31or SM-2 were cylindrical, with indeterminate growth, and similar to those found on arctic legumes. However, in the active symbiotic zone of sainfoin nodules, bacteroids of strain N31were pleiomorphic or spherical and found individually or in groups of three, surrounded by the membrane envelope, whereas the bacteroids of strain SM-2 were elongated and enclosed in clusters of 3 to 12 by each membrane envelope. Thus, arctic strain N31affects the internal structure of sainfoin nodules. Nodules of arctic legumesA.alpinus,Oxytropis maydelliana, andOxytropis arctobia, infected with either strain N31or SM-2, contained lipid droplets, while sainfoin nodules did not show such characteristics. This phenomenon seems specific to arctic legumes and it is not influenced by the origin of the nodulating strain.

ISSN:0008-4026    

DOI:10.1139/b89-395

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Type studies have demonstrated that despite some recent assertions in the literature, certain anamorph-genera are in need of further reassessment.Hyalothyridium viburnicolaTassi, typifying the anamorph genusHyalothyridiumTassi, is treated as anomen dubium. As a result of reassessment ofScolecosporiella typhae,Urohendersoniella, recently considered a synonym ofScolecosporiella, is reinstated. A new anamorph-genus,Orphanocoela, is proposed to accommodate three species, two of them transfers fromHyalothrydiumand one fromScolecosporiella.AmarenographiumandCallistosporaare redescribed and compared withUrohendersoniella. Conidia of members of the the last three genera have mucoid appendages that originate in a unique manner.

ISSN:0008-4026    

DOI:10.1139/b89-396

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Flax rust,Melampsora lini(Ehrenb.) Lév., occurs onLinum marginaleCunn., the onlyLinumspecies indigenous to Australia. Evidence suggests that the rust is native toL.marginaleand is not a recent introduction. Forty-five isolates from this rust population, collected from 21 locations, were tested for reaction type on the standard set of 28 flax (L.usitatissimum) differential lines. All isolates were avirulent on the majority of differentials and only three clearly different virulence phenotypes were distinguished. This finding contrasts with the results of a companion study in which the same isolates displayed many different virulence phenotypes when tested on a set ofL.marginalelines. Two factors apparently contribute to the failure of theL.usitatissimumdifferentials to detect most of the variation for virulence present in this rust population. First, 10 of the differentials have been reported to possess resistance geneL9in addition to their designated gene. Since all isolates recognize theL9gene, these differentials could make no contribution to differentiating between the isolates. Second, many of theL.usitatissimumresistance genes apparently do not occur inL.marginaleand with no selection on the rust to conserve or evolve the corresponding virulence genes, the corresponding avirulence genes appear to have become, or remained, fixed in the rust population.

ISSN:0008-4026    

DOI:10.1139/b89-397

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Melampsora lini, the causal agent of rust disease on flax and linseed (Linum usitatissimum), also occurs on the indigenous Australian speciesLinum marginale. Forty-five isolates ofM.linicollected fromL.marginaleplants at 21 locations were tested for pathogenicity on 46 lines ofL.marginalethat originated from 22 sites spanning the same range (approximately 2000 km) covered by the rust isolate collection sites. The results reveal the existence of extensive variation in both host and pathogen. Rust isolates originating from different sites possessed unique virulence patterns in all cases. Among the host lines, 21 different phenotypes were identified. Lines from six sites were susceptible to all isolates, but no line was resistant to all isolates. The results, together with those of a companion study, provide evidence of virulence-gene adaptation ofM.linito different host species and of adaptation on a broad geographic scale within a host species. The rust reaction data suggest that theNgene for resistance inL.usitatissimumalso occurs inL.marginale, but otherwise there is no evidence for commonality between the (presumptive) resistance genes inL.marginaleand those inL.usitatissimum.

ISSN:0008-4026    

DOI:10.1139/b89-398

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The studied area concerns the inflorescence of the yoke elm,Carpinus betulus, and especially the lobes of the involucre surrounding the fruit for groups of two flowers, which form these inflorescences. Data come from three natural populations, geographically distinct. Two fluctuating asymmetries and two directional asymmetries are noted in the system. Their characteristics and the relations between them are examined. The interpretation takes into account the ontogenesis of the flower structure and leads to a discrimination between populations.

ISSN:0008-4026    

DOI:10.1139/b89-399

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The Eurasian grass,Calamagrostis epigejos(L.) Roth, has been both deliberately and accidentally introduced to North America. Deliberate introductions have usually been destroyed because the plants were weedy and difficult to confine. Introductions at approximately 50 sites, most of them accidental, are documented. While the grass sometimes is the dominant species over several square metres and can out-compete some other weedy species, only at two sites is it known to have spread more than 10 km in a 30-year period. One site is Ontario, Canada, along the road between Espanola and Whitefish Falls, and the other is Liberty State Park in New Jersey, U.S.A. There have been major earth moving projects at both sites so that spread of rhizomes as well as seed dispersal may have been involved. Data analyses of 16 characters used, or possibly useful, in recognizing intraspecific taxa are presented. Taxonomic recognition ofC.epigejosas an amphimictic, polyploid complex is discussed. Application of the treatment given by Tzvelev to our data suggests that (i) ssp.extremiorentalisTzvelev and ssp.macrolepis(Litv.) Tzvelev have each been introduced once into North America; (ii) most specimens in North America belong to ssp.epigejos, ssp.glomerata(Boiss. and Buhse) Tzvelev, or ssp.meinshauseniiTzvelev, but it is not always possible to distinguish among these subspecies with confidence; and (iii)C.epigejosvar.georgica(C. Koch) Ledeb., as recognized by Fernald, is probably synonymous with ssp.glomerata. Plants collected from five sites in Ontario had chromosome counts of 2n = 28 + 4B. Plants ofC.epigejosssp.macrolepisfrom New York were 2n = 42.

ISSN:0008-4026    

DOI:10.1139/b89-400

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

This study was based on 148 accessions representing 39 species ofHordeum. SEM ultrastructural morphology of waxes was based on individual spikelets, whereas waxes' chemical composition was assessed from whole plants. When all the data, in the form of individual accessions, were subjected to various cluster analyses methods, no groupings were revealed. But when the data were first summarized by species and then subjected to clustering, two polythetic groups of species were detected. Group 1 is characterized by species with 40–60% average alcohol content and by the common presence of diketones, whereas group 2 is characterized by species with 61 – 80% average alcohol content, by the total absence of hydroxy-β-diketone, and almost all species without β-diketone. The chemical data were then subjected to classificatory discriminant analysis to assess if a single previously unclassified accession could be identified into one of the two groupings. The nature of the differences between the two groupings was described by means of a canonical discriminant analysis. Mostly only plates and filaments were detected, and in many accessions the filaments were widened, appeared platelike, and were characteristic for one group. Presence of β-diketone varied within species.Hordeum violaceumwas found to be unique in chemical composition.

ISSN:0008-4026    

DOI:10.1139/b89-401

出版商:NRC Research Press    

年代:1989

数据来源: NRC