摘要:

This laboratory study was designed to examine the response of a postfire ascomycete community to elevated temperatures and treatment intervals corresponding to those recorded during the burning of a tallgrass prairie. Aerated steam treatment of prairie soil samples (35, 40, 55, 70, 85, or 100 °C) for intervals of 60, 100, 140, or 180 s enabled us to examine the response of individual species comprising the carbonicolous ascomycete community.Simulation of a grassland fire by aerated steam treatment of prairie soils promoted the development of 20 species of ascomycetes. Generalists such asSporomiella subtilisAhmed and Cain occurred at high frequencies over most of the temperature range while specialistsPodospora curvispora(Cain) Cain,Sordaria macrosporaAwd., andLeptosphaeriasp. were important at only one temperature. Species diversity, richness, and number of species per sample were significantly affected by the temperature of the steam treatment. The temperature–treatment interval combination allowing for the greatest expression of diversity in the carbonicolous ascomycete community was 55 °C for 60 s. Since a grassland fire does not uniformly heat the soil surface, the environmental patchiness created by this physical perturbation may be an important factor in determining the composition of the carbonicolous ascomycete community in prairies.

ISSN:0008-4026    

DOI:10.1139/b78-279

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

In the natural environment and in culture the vegetative mycelium ofFomitopsis cajanderiforms a primordial mat, a basidiocarp primordium, and a sporulating basidiocarp. The fundamental structural unit is the clamped, generative hypha which functions initially in nutrient absorption, then produces unbranched or branched skeletal cells and basidia. and later develops irregularly thickened walls and swollen clamp connections. These structural elements, the brownish-rose color produced by massed skeletal cells, the hymenium of basidia only, and the narrow, slightly curved basidiospores are characters readily observed in the natural basidiocarp and in culture.

ISSN:0008-4026    

DOI:10.1139/b78-280

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Germination tests at a wide range of constant temperatures show that the upper and lower thresholds forE. aphidisresting spores are about 3.5 and29.5 °C, respectively. Good germination was obtained over the range 10–22 °C with an optimum at about 16.5 °C. It is not known if spores exposed to temperatures above the optimum and failing to germinate are inactivated or killed. An empirical model is presented that describes the time–temperature–germination relationships of one test population. A similar modeling approach may be also applied to other spore populations.

ISSN:0008-4026    

DOI:10.1139/b78-281

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Tomato plants grown in soil infested withPythium myriotylumor in soil containing nonviable mycelium were severely stunted. Mycelium ofP. myriotylumwas produced on a glucose–glutamate–cholesterol medium, separated from the medium, lyophilized, and ground into a fine powder in a Waring blendor. Tomato plants transplanted into steam-pasteurized soil with the addition of 200 mg of the nonviable mycelium developed foliar necrosis and were severely stunted. Seedlings with roots immersed in an autoclaved aqueous suspension of the mycelium (100 μg/ml) developed laminar collapse and dehydration within 12 h and were killed within 24 h. Detached tomato leaves behaved similarly. On autoclaving, the toxin associated with the mycelium ofP. myriotylumwas relatively stable below pH 6 but labile at pH values above 6. Treated leaves lost more fresh weight at 35 °C than at 27 or 22 °C. Evidence for variability in toxin production withinP. myriotylumwas obtained. Toxin(s) in the mycelium ofP. myriotylummay be involved in reduced growth and death of tomato plants. This is the first known report of toxin production byP. myriotylum.

ISSN:0008-4026    

DOI:10.1139/b78-282

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A rapid and accurate method for the determination of cell mass of soybean (Glycine max) and Paul's Scarlet rose (Rosasp.) cells is reported using sonication and optical density. Results may be obtained within 20 min and would be of particular use in providing cell mass (i.e., dry weight) information quickly.

ISSN:0008-4026    

DOI:10.1139/b78-283

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A new genus and species of ascomycetes,Catulus aquilonius, is described, illustrated, and tentatively assigned to the Mycosphaerellaceae. It grows as a parasite on stromata ofSeuratia millardetii(Raciborski) Meeker and is characterized by two-celled, setulose ascospores.

ISSN:0008-4026    

DOI:10.1139/b78-284

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A palmelloid-forming mutant of the unicellular green algaChlamydomonas eugametoshas been studied ultrastructurally. The repetition, within the palmelloid envelope, of four-celled groups surrounded by wall layers suggests that normal asexual cytokinesis occurs but successive cell generations are unable to separate. Individual palmelloid cells are smaller than wild-type cells and possess flagella which are short (1–2 μm) and occasionally bulbous at the tip but appear normal with regard to internal microtubular, transitional region, and basal body structure. The association of granules with the outer surface of the palmelloid envelope and the tendency of palmelloids to form large aggregates in culture indicate a change in the adhesive properties of the cell walls of this mutant. A comparison of the ultrastructure of mutant palmelloids with previously described chloroplatinic-acid-induced palmelloids shows that the two types differ in both flagellar development and in the extent of cell wall formation.

ISSN:0008-4026    

DOI:10.1139/b78-285

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Basidiocarps of 39 epigeous species of proven or potential mycorrhizal fungi were found in three fertilizedPinus taedaplantation s during 1972 and 1973. The largest numbers of basidiocarps on all three plantations were found on nonfertilized plots or plots fertilized with P only. Fewest basidiocarps were found on plots fertilized with N. Numbers of basidiocarps ofSuillus hirtelluswere decreased by N fertilization. Numbers of basidiocarps of some other potential mycorrhizal fungi were not altered substantially by fertilization treatments. The average numbers of total living mycorrhizal tips were correlated well with average numbers of epigeous basidiocarps of proven or potential mycorrhizal fungi on fertilized plots. However, if mycorrhizal tips formed byCenococcum geophilum, which do not form visible basidiocarps, were ignored, the remaining mycorrhizal tips were not well correlated with numbers of basidiocarps of proven or potential mycorrhizal fungi.

ISSN:0008-4026    

DOI:10.1139/b78-286

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Roots ofZea mayscv. Golden Bantam were treated with a 0.1% solution of caffeine for 1–4 h and allowed to recover for up to 17 h. Binucleate cells were present in the root cap and in the meristem; nuclear volumes were determined for the pairs of sister nuclei in the binucleate cells. In row I cells of the root cap, 41%of pairs of sister nuclei had different volumes in roots treated with caffeine for 1–4 h or for 2 h and then allowed to recover for 5 h. In the period 2 + 6 to 2 + 17 h, however, 70% of the pairs differed in volume. Volumes of sister nuclei present in the same cell differ soon after they enter G1; they also differ in the period 2 + 6 to 2 + 17 h when mean nuclear volume increases from 145 to 243 μm3. Both aspects suggest that sister nuclei differ in their ability to grow. In most binucleate cells, the larger nucleus was in the position it would have occupied if it lay in a row I cell. It is suggested, therefore, that a gradient exists, in a row I cell, of some factor that regulates nuclear growth. The consequence of this gradient is that sister nuclei grow differentially even though they share a common cytoplasm. Mitosis in a row I cell appears to be asymmetrical. Cells induced to become binucleate were inhibited by the caffeine treatment. Only 9% of the binucleate cells completed a cell cycle and divided and, for some of them, cycle time was increased.

ISSN:0008-4026    

DOI:10.1139/b78-287

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Explants taken from superficial epidermic and subepidermic tissues from flowering stocks ofNicotiana tabacumcan be induced to flower, produce buds, callus, or roots from a single type of cell, of subepidermic origin. Explants from neoformed roots, when cultivated on media inducing the formation of flowers (IAA 10−6 M, kinetin 10−6 M), buds (IAA 10−6 M, BA 10−5 M), callus (2,4-D 5∙10−6 M, kinetin 10−7 M), and roots (IBA 10−5 M, kinetin 10−7 M) can form buds or callus. New roots are formed when either IAA or kinetin is omitted from the flowering medium. None of the above media induced the formation of flowers from root explants.Temperatures of 22 or 24 °C and the addition of 10−6 MBA were optimal for thede novoformation of buds from root explants. [Traduit par le journa

ISSN:0008-4026    

DOI:10.1139/b78-288

出版商:NRC Research Press    

年代:1978

数据来源: NRC