摘要:

The prevalence of conidia ofDendryphion nanumwas determined by the flotation count method in soil samples obtained from four groups of fields. The first three groups consisted of 25 rape, 25 cereal, and 23 fallow fields. History of prior crops grown was unknown. The fourth group consisted of 10 wheat fields that had never been cropped to rape. Conidial populations ranged from 22 to 3473 conidia per gram soil for rape, 0 to 1680 for cereal, 0 to 547 for fallow, and 0 to 34 for wheat fields. The mean numbers for these groups of fields were 948, 354, 86, and 6 respectively.Prevalence ofD. nanumconidia apparently was promoted by cropping to rape and, to a lesser extent, the presence of wild mustard in fields. The populations of conidia were much higher in the first three groups of fields in an intensive rape-growing area around Melfort, Saskatchewan, than in fields in less intensive areas. Evidence is presented to support the reliability of the flotation count method. This method and that used for the isolation ofD. nanumdirectly from soil are described.

ISSN:0008-4026    

DOI:10.1139/b73-292

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Part three of a biosystematic study of theCaltha leptosepalacomplex in the Rocky Mountains involves analyses of embryology and gross morphology. Data obtained from both the natural populations investigated and from dried herbarium material support the premise that only one species,Caltha leptosepala, can be taxonomically justified for the Rocky Mountains.

ISSN:0008-4026    

DOI:10.1139/b73-293

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Cytochalasin B (CB) applied at 30 μg/ml to seeds of onion,Allium cepa, from the start of imbibition, produced a reversible inhibition of mitosis and axis elongation. Inhibition appeared only after the 4th day and increased progressively thereafter. Mitotic inhibition by a 24-h pulse of CB applied to 6-day-old seedlings increased with root length. These results suggest that CB affects plant mitosis indirectly, possibly via inhibition of transport. CB did not produce polyploid or multinucleate cells.Cytochalasin B (30 μg/ml) supplied for 3 days to roots of onion bulbs, growing in water, produced morphological changes which are expressed here as percentages of the controls. Root length decreased (44%) while diameter increased (148%). Cortical cell lengths decreased (53%) and diameters increased (128%) when measured at 9 mm from the root tip. These compensatory changes resulted in comparatively minor decreases in root (97%) and cell (90%) volume, indicating that CB, even at the high concentration used, was not acting primarily as a general metabolic inhibitor. Cell counts along diameters at comparable distances, 130 cortical cells from the apical initial region, showed no change in the number of cells representing cortex and stele.

ISSN:0008-4026    

DOI:10.1139/b73-294

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The fungus flora from four pine forest soils was investigated. Qualitative studies used a soil-washing method, whereas quantitative investigations were performed using a direct observation technique. Results indicate that the fungus populations on litter and humus from all four forest soils are fairly similar, withCladosporium herbarum, Aureobasidium pullulans, Alternariasp., and various members of the order Sphaeropsidales being common in the litter, andTrichodermaandPenicilliumspecies increasing in frequency in the F and H layers. The fungi isolated from the mineral soil horizons were more varied in nature, but certain genera seemed to be found frequently; these includedMortierella, Chrysosporium, Oidiodendron, Paecilomyces, Cylindrocarpon, Torulomyces, and sterile dark fungi.A detailed investigation of aPinus strobusforest at St. Williams, Ontario, revealed no distinct seasonal patterns in the relative frequencies of the species of fungi.Quantitative studies showed that, in all soils, mycelial content decreased with depth from the humus. A comparison of the four sites showed a wide variation in fungal mycelium, varying from 30 m/g dry soil underPinus strobus(in the A1horizon) to 1540 m/g underP. contortaduring May. Seasonal data from theP. strobusforest indicate a peak in mycelial content during August.

ISSN:0008-4026    

DOI:10.1139/b73-295

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The development of the embryo, endosperm, and antipodals was studied in five hexaploid triticale lines. The egg cell was fertilized 10–15 h after pollination. The first division of the zygote occurred 15–20 h later. Ninety-six hours after pollination there was a twofold difference among the lines in the number of embryo cells, which ranged from 17 to 31. The polar nuclei were fertilized 4–5 h after pollination and the first division of the primary endosperm nucleus took place 2–3 h later. At 60 h the lines examined fell into two groups with respect to endosperm development: one group included 6A190 and 6A250, both raw amphiploids, which had 1032 and 486 endosperm nuclei, respectively; and another which included Rosner, Armadillo 458, and 6517, all products of artificial selection, with 209, 201, and 98 endosperm nuclei, respectively. The first five or six endosperm divisions were highly synchronized while later a gradient was established. Cellularization of endosperm was first observed 96 h after pollination. No appreciable amount of mitotic abnormalities was observed in the endosperm nuclei. In all lines examined endosperm nuclei were found with DNA amount exceeding 6C.The number of antipodals, some of which were highly endopolyploid (up to 256C), ranged from 10 to 30 within and among lines. Disintegration of the antipodals began about 3 days after pollination in 6A190, at 4 days in Rosner, and at 5 days in the other lines. The rate of endosperm development and especially the disintegration of the antipodal complement seemed to be positively related with the amount of seed shrivelling observed in the lines studied.

ISSN:0008-4026    

DOI:10.1139/b73-296

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Colonies of the rust fungusCronartium ribicolaJ. C. Fischer were grown axenically and then transferred so that they lay immediately next to callus cultures of the pine host (Pinus monticolaDougl.). Twelve days after the establishment of this association samples of the fungal mycelium taken 2 mm away from the pine callus and at the host–parasite interface were fixed for electron microscopy. Differences were found in the appearance and thickness of the lateral walls and extracellular coatings depending on the proximity of the fungus to the host–parasite interface. Septa were intermediate in structure between the Ascomycete and dolipore types. The origin of the extracellular sheath is discussed.

ISSN:0008-4026    

DOI:10.1139/b73-297

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Termitaria snyderiThaxter forms small discoid lesions on the exoskeleton of different species of termites. Its conidiogenesis has been studied by light and electron microscopy. The phialides are oriented parallel in a closely packed sporodochium. The conidia are produced endogenously in basipetal succession from a fixed conidiogenous locus and are liberated when the tip is broken off the phialide as a result of the force applied by the formation of new conidia. The area of the phialide beyond the locus forms a tubular collarette. The conidium initial buds out at the locus and after it has received its organelles and reached a certain size it is delimited by a centripetally growing transverse septum. The region of the growing septum has many vesicles which may be involved in cross wall synthesis. Conidia are cylindrical, uninucleate, and double-walled. They have mitochondria, endoplasmic reticulum (ER), conspicuous lipid droplets, and vacuoles. Each conidiophore has long mitochondria, elongate nuclei, and much endoplasmic reticulum. The plasmalemma of the conidiophore is highly convoluted.

ISSN:0008-4026    

DOI:10.1139/b73-298

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Changes in the degree of dormancy, rate of growth, respiratory capacity, and in the amounts of several major cell constituents (sugars, protein, amino acids, cell wall materials, starch, and chlorophyll) were examined in vegetative buds ofPopulus balsamiferaL. as they developed from midwinter dormancy to the spring flush of growth in 1972. A significant decrease in the dormancy status of buds occurred during the period March 17 to April 3, and this was accompanied by an increased level of catabolic metabolism of carbohydrates and protein. A further change to anabolic metabolism at the end of April, nearly 2 weeks before bud burst, resulted in a net synthesis of cellular constituents in preparation for bud burst.

ISSN:0008-4026    

DOI:10.1139/b73-299

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Alternaria alternataandFusarium oxysporumwere isolated from field-grown peppers (Capsicum frutescensL.) and the antifungal sesquiterpene, capsidiol, was demonstrated inA. alternatalesions. In laboratory experiments, both fungi induced strongly antifungal diffusates and the activity was shown to be due to their content of capsidiol, or in the case ofF. oxysporumto a combination of capsidiol and capsenone. Growth of the non-pathogenMonilinia fructicolawas completely inhibited by theA. alternatediffusate at one-eighth and by theF. oxysporumdiffusate at one-quarter of the original concentration. The inducing fungi were also inhibited by their own diffusates 80% and 50% respectively but, in spite of this, effectively parasitized fruit tissue.

ISSN:0008-4026    

DOI:10.1139/b73-300

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

An investigation of several conifer species was conducted to evaluate the influence of atmospheric, edaphic, topographic, and vegetation variables of the environment on water potential. Correlation coefficients averaged close to 1.0 for the relationship of plant density to water potential when other environmental influences were static. This was interpreted as quantitative evidence of the intraspecific competition for available moisture by plants. Water potential values of 21 stands of coniferous trees, 3 each of seven species, were quite highly correlated (R = 0.84) to elevation, percentage sand, temperature, relative humidity, and vapor pressure deficit, even though the stands were found in widely divergent habitats.

ISSN:0008-4026    

DOI:10.1139/b73-301

出版商:NRC Research Press    

年代:1973

数据来源: NRC