摘要:

Isolates ofAspergillus flavusLink from both cool and warm latitudes were cultured on potato dextrose agar containing yeast extract to identify sclerotia-producing strains. Chloroform–MeOH extracts of sclerotia were analyzed for the presence of aflatoxins and major indole metabolites (e.g., cyclopiazonic acid, aflatrem, and dihydroxyaflavinine). Aflatoxin is reported from sclerotia ofA. flavusfor the first time. Cyclopiazonic acid was detected primarily in sclerotia of isolates from warmer latitudes. Aflatrem and dihydroxyaflavinine were detected in sclerotia from 85% of the strains examined. These metabolites are associated with the sclerotial stage of the life cycle, because neither were detected in extracts of the culture medium and mycelium of Petri dish cultures from which all the sclerotia were removed. Geographic variation and intrafungal allocation of these toxic compounds inA. flavusare examined from the evolutionary ecologist's perspective of selective forces shaping the chemical defense systems of fungi.

ISSN:0008-4026    

DOI:10.1139/b82-070

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Three pink species of Corticiaceae (Basidiomycetes) growing on living grasses are described:Laetisaria fuciformis, the causal organism of the red thread disease and two species classified in the new genusLimonomyces: Limonomyces roseipellissp. nov. andLimonomyces culmigenuscomb. nov. The morphology and disease symptoms of these species are described and their taxonomy discussed.

ISSN:0008-4026    

DOI:10.1139/b82-071

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Annual dinitrogen fixation at the surface of ombrotrophic Thoreau's Bog in eastern Massachusetts, U.S.A., is estimated at 1.0 g N∙m2. The rates of acetylene reduction are lower but still significant in the dark, suggesting that fixation is carried out both photosynthetically and heterotrophically. The ratio15N2fixed: C2H2reduced was 1 mol: 3.5 mol inin vitrocalibration experiments. Dinitrogen fixation is ecologically important in this bog as it exceeds the only other known input of nitrogen, namely deposition of NO3−and NH4+in bulk precipitatio

ISSN:0008-4026    

DOI:10.1139/b82-072

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Penetration of Sitka spruce,Picea sitchensis(Bong.) Carr., seeds by the pathogenic fungusCaloscypha fulgens(Pers.) Boudier was examined in intact and sectioned naturally infected and inoculated seeds with light and scanning electron microscopes. One to seven circular to slightly elongate, white to whitish blue infection cushions occurred on a typical naturally infected seed. Within 1–3 days following inoculation, the fungus formed dome-shaped infection cushions on the seed surface and within the next 10 days several straight-line penetration holes were observed in the seed coat directly under each cushion. During penetration, pathogen growth was confined to the penetration holes and intertissue spaces until it reached the endosperm and embryo tissues throughout which it ramified.Caloscypha fulgensoccasionally entered seeds through seed coat cracks, but never through the micropyle. Pathogen emergence from diseased seeds occurred through intact or cracked seed coats and the micropyle.

ISSN:0008-4026    

DOI:10.1139/b82-073

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Among single-spore isolates ofMyrothecium roridumobtained from leaf spots onCroton sparsiflorus, some required light for sporulation on natural media while others sporulated in the dark. A dark-sporulating (DSP) isolate and a light-requiring one (LSP) were studied. Sporulation of the DSP isolate was also better in light. Amino acids were, generally, the best sources of N for this isolate. The LSP isolate failed to sporulate on a medium containing nitrate. This isolate, however, showed moderate sporulation, even in the dark, on a medium with cellulose as the C source and around the inoculum plug on a medium lacking C. Appreciable sporulation was seen in the LSP isolate when nitrate was replaced by casaminoacids or tyrosine. While tyrosine did not enable sporulation in the presence of nitrate, a few other aromatic compounds did. The aromatic nature of tyrosine, rather than its role as an N source, has been suggested as being responsible for its effect on the LSP isolate.

ISSN:0008-4026    

DOI:10.1139/b82-074

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Leaf infection byVerticillium albo-atrumin both a susceptible cultivar and a resistant cultivar of potatoes was investigated. In both cultivars penetration occurred directly through the cuticle, leaf hairs, and stomata. In the resistant variety, hyphae were restricted to cells in the epidermis and palisade mesophyll resulting within 5 days in pinpoint necrotic spots, whereas in the susceptible cultivar hyphae penetrated freely from cell to cell in the entire leaf and killed the leaf within 5 days. It is suggested that the resistance is manifested as a hypersensitive reaction and that the method herein described offers a possible alternative to the root-dip method of testing for resistance.

ISSN:0008-4026    

DOI:10.1139/b82-075

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The fruits ofLindera benzoin(L.) Blume are dispersed by several species of birds, mainly thrushes (Turdidae) and mimids (Mimidae). In a study in Trelease Woods, Illinios, removal rates (as percentages) did not keep pace with fruit availability and exhibited a low point in midseason. Relative removal rates in tree-fall gaps initially exceeded those in forest interior, though total fruit abundance there was less. Isolated bushes had slightly higher relative removal rates initially than clumped bushes, again despite a lower availability. Percentage removal rates on bushes with small displays often exceeded those on large displays, although the absolute numbers removed from large displays were greater. Most of these trends held up when factors were considered in combination.

ISSN:0008-4026    

DOI:10.1139/b82-076

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Laticifers in seedlings ofGlaucium flavumCrantz were examined by electron microscopy. Laticifer initials first apeared in procambium of the radicle adjacent to the phloem about 48–72 h after germination. Differentiation of laticifer initials was characterized by the proliferation of numerous vesicles from dilation of endoplasmic reticulum. The usual complement of organelles was present in laticifer elements including a nucleus, mitochondria, dictyosomes, and plastids. Plastids were devoid of organized lamellae and starch grains but contained electron-dense, membrane-bound inclusions. Large crystalline bodies of unknown composition were also seen in the cytoplasm of some laticifer elements. Perforations were not observed in the longitudinal walls shared by adjacent laticifer elements; thus the laticifer system in this species can be classified as nonanastomosing. Transverse walls between laticifer elements remained intact until late in cell differentiation; however, large perforations did form in these walls as a result of the gradual removal of wall material at the perforation site.

ISSN:0008-4026    

DOI:10.1139/b82-077

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Cultural, cytological, and developmental aspects of the patellariaceous ascomyceteRhytidhysterium rufulumare investigated. A comparison of the ultrastructural features of theR. rufulumascus with those of other loculoascomycetes is made. Meiosis and mitosis in the ascus and ascospores are not significantly different from those considered typical for most Ascomycetes. Ascospore delimitation begins after the ascus reaches its 16-nucleate stage. Differences in centrum development and hymenial configuration indicate that the Patellariaceae and Hysteriaceae may have to be placed in different orders. The centrum ofR. rufulumappears unique and characteristic, not of thePleosporatype.

ISSN:0008-4026    

DOI:10.1139/b82-078

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Ring traps detached from axenic cultures ofDactylella doedycoidescould be caused to inflate with chlorobutanol vapour, when placed upon cornmeal agar. Isolated uninflated rings produced a single, slowly growing hypha from the stalk scar; it later produced branches. Isolated inflated rings produced several rapidly growing hyphae from the inner curvatures of their three cells, mimicking the response elicited by trapped prey. Even after several hours of hyphal proliferation, isolated uninflated rings could be caused to inflate, and inflation increased the growth rate of the primary hypha.

ISSN:0008-4026    

DOI:10.1139/b82-079

出版商:NRC Research Press    

年代:1982

数据来源: NRC