摘要:

Myzocytium intermediumis described as a new endoparasite ofRhabditisnematodes. It produces laterally biflagellate zoospores which track the host and encyst in the vicinity of the body orifices. Infection of mature nematodes is by means of germ tubes from encysted zoospores which penetrate through the body orifices.The thallus is filamentous, much-branched, and nodular in appearance. At maturity it divides to form numerous segments of irregular size and shape. In the vegetative phase the parasite resembles aLagenidium. In the sexual stage, however, the young antheridium cannot be distinguished morphologically from either the oogonial or zoosporangial segments. No fertilization tube is produced and the antheridial protoplast migrates through a pore in the common wall to fertilize the oogonium. After fertilization, a thick-walled, smooth, spherical oospore is produced.

ISSN:0008-4026    

DOI:10.1139/b76-001

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The extensive salt marshes at East Pen Island in Hudson Bay are described in quantitative terms and the well-marked sequence of species is characterized. The lower marsh is dominated byPuccinellia phryganodesandCarex subspathacea, withHippurus vulgarisandSenecio congestusabundant in the salt pans. The midmarsh has well-developed swards ofDupontia fisheriandCelamagrostis neglecta, which give way to stands ofCarex aquatilisin a well-developed freshwater marsh below the first beach ridge. The results are compared with other arctic salt marshes, and the development of a wide freshwater marsh in the upper zone of the salt marsh is described. This feature is perhaps unique to the Hudson Bay marshes and is a function of meltwater runoff from the surface of the permafrost table. This results in the high, standing water table at the top of the marsh, which is maintained by the permafrost table of the salt marsh itself.A transit survey of the marsh relates the quadrat samples to a high-tide datum point and allows interpretation of the vegetation sequence in terms of saltwater inundation. The depth of the active layer of the salt marsh is also described.

ISSN:0008-4026    

DOI:10.1139/b76-002

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The monoterpene hydrocarbons of the cortical blister oleoresin ofAbies grandiswere compared, using gas chromatography, with those obtained from lesions that formed as a response of the tree to inoculation with culturedTrichosporium symbioticum, a fungus which is transmitted by the fir engraver beetleScolytus ventralis. The resins from each source differed both quantitatively and qualitatively. Three terpenic compounds (tricyclene, camphene, and bornyl acetate) that are normally present in primary resin were not found in secondary resin. However, resins that formed in response to the inoculation contained higher concentrations of myrcene in three quarters of the trees and delta3-carene in one quarter of the trees that were sampled than resin from pitch blisters, which contained only trace amounts of these two compounds. These results suggest that conifers respond to fungus infection by producing monoterpenes which are more toxic, repellent, and (or) inhibitory to bark beetles and their associated fungi (e.g. myrcene and delta3-carene) at the expense of attractive or less biologically active compounds (e.g. camphene) which are present in the preformed resin system.

ISSN:0008-4026    

DOI:10.1139/b76-003

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Fifty-six permanent sample plots were established in deciduous swamp communities of south-eastern Michigan whereUlmus americanawas dominant before introduction of the Dutch elm disease. Plots were also established in old fields where elm seedlings were present. The purpose of the study was to determine the composition of the overstory, understory, and seedling layers in deciduous swamp forests and to provide a base line for determining the fate of young seedling and sapling elms, and the rate and nature of succession in the deciduous swamp communities. The major overstory species in the three swamps studied wereFraxinus nigra,Acer rubrum, andBetula alleghaniensis. These species were also dominant in the understory along with smaller numbers ofCarpinus caroliniana,Ulmus americana,Tilia americana, andFraxinus pennsylvanica. In the next generation the communities will be much as they are today. The overstory dominants are also strongly represented in the seedling layer.Ulmus americanawas more abundant in this layer than in the understory. Therefore,Ulmushas not been eliminated from the deciduous swamps but makes up about 10 to 15% of the understory and seedling layers. Old fields and other open upland areas are much more important habitats for regeneration ofUlmusthan swamp communities. Indications are that unlikeCastanea dentata,Ulmus americanawill be perpetuated for generations by seeds from young elm trees; however, the average life span of the species will be drastically reduced.

ISSN:0008-4026    

DOI:10.1139/b76-004

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Datura stramoniumfruit capsules inoculated withMonilinia fructicolaor several other non-pathogenic fungi produced diffusates inhibitory toM. fructicolain spore germination assays. Detailed analysis of diffusates that are induced byM. fructicolaindicated that they were complex and that antifungal activity was widely distributed through a number of column chromatographic fractions. Four compounds were isolated. These were sesquiterpenes, three of which, lubimin, hydroxylubimin, and capsidiol, have been described from otherSolanaceae. The fourth, 2,3-dihydroxygermacrene, is a new compound with moderate antifungal activity but which is of especial interest as a possible precursor of several phytoalexins in theSolanaceae.

ISSN:0008-4026    

DOI:10.1139/b76-005

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Rhizomes of the African emergent aquaticBurnatia enneandraM. Mich. possess a layer of tissue superficially resembling a periderm in the position in which an endodermis might be expected. It is suggested that this layer of tissue represents a multiple endodermis. Distinctive idioblasts occur in the outer region of the multiple endodermis. At the end of the growing season soft tissues exterior to the multiple endodermis collapse with the death of the adjacent leaves, leaving behind a fibrous armor of leaf traces and cortical vascular traces. The multiple endodermis, idioblasts, and armor may be of adaptive significance in relation to dry-season dormancy inBurnatia.

ISSN:0008-4026    

DOI:10.1139/b76-006

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Pea seeds age rapidly and may be infected by storage fungi, e.g.Aspergillus ruber, when stored under conditions of high relative humidity and temperature (92% relative humidity and 30 °C in these experiments). In the absence of microorganisms, pea seeds retain their viability for 6 to 8 weeks, although the speed of germination is reduced. In embryonic axes, aging is associated with a slower increase in O2uptake, a delay in protein synthesis, smaller ATP and amino acid pools, and reduced activity of alkaline phosphatase (EC 3.1.3.1) and 3-phosphoglyceraldelyde dehydrogenase (EC 1.2.1.12). Axes recover from these changes during germination. Infection byA. ruberreduces germination. In axes from infected peas the onset of protein synthesis is delayed even more and the ATP and amino acid pools are smaller than in aged axes. Axes from infected seeds recover slowly, if at all.

ISSN:0008-4026    

DOI:10.1139/b76-007

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The morphology and taxonomic history of the genus is reviewed. In field studies, substrates yielding isolates ofConidioboluswere varied, and success in obtaining isolates appeared to be correlated with high moisture.Conidiobolus coronatuswas very abundant. Isolates of this fungus varied greatly in abundance of villose resting spores and 14 did not produce microconidia. Ranges in diameters of microconidia and primary conidia were greater than previously described. Thick walls developed in conidia from the field isolates projected onto Petri-dish lids. This phenomenon could be a means for surviving unfavorable conditions. Morphological examinations were performed on 17 type specimens ofConidiobolusspecies, and on cultures representing 36 of the named taxa after obtaining single-spore isolates. The ability to produce various spore types was readily lost in culture. The primary conidia of all type cultures were determined to be multinucleate. Optical density at 725 nm and dry weight of known packed cell concentrations were measured and found to have a linear relationship. Utilization of five nitrogen sources and four carbon sources was determined for the type cultures by using optical density. Cluster analysis of the named taxa was done using NTSYS, based on morphological and nutritional characters.

ISSN:0008-4026    

DOI:10.1139/b76-008

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Basidia, basidiospores, and mycelium were examined to determine the nuclear condition during different stages of growth ofMarasmius perniciosus. Young basidia were binucleate and four mononucleate basidiospores developed after meiosis. The primary hypha from a germinating basidiospore was septate with uninucleate cells but persisted only for a short time and gave rise to mycelium resembling 'textura intricata.' Apparent fusion of hyphal branches resulted in dikaryotization, and subsequent formation of normal, binucleate hyphae with clamp connections at most septa suggests that the fungus is homothallic.

ISSN:0008-4026    

DOI:10.1139/b76-009

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Race 370,Melampsora lini, was selfed and the progeny were tested for virulence on flax cultivars each of which contained a single gene pair for rust resistance. All cultures tested were virulent on flax cultivars with resistance genesL9,M,M1,M2,M4,N1, andPand avirulent on flax cultivars possessing theK,L2,L3,L5,L6,L7,L11,M3,M5,M6,N,N2,P1,P2,P3, andP4genes for resistance. Segregation for virulence occurred on flax cultivars with theL,L1,L4, andL10genes. Virulence on cultivars with theL4andL10genes was conditioned by single recessive gene pairs. The segregation ratio for virulence on theL1gene more nearly fit a digenic recessive ratio than a monogenic ratio. Virulence on the cultivar containing theLgene appeared to be conditioned by two recessive gene pairs. Virulence on cultivars with geneL4was apparently linked withL10, but no linkage was detected betweenLandL4orLandL10.

ISSN:0008-4026    

DOI:10.1139/b76-010

出版商:NRC Research Press    

年代:1976

数据来源: NRC