摘要:

A study of mycorrhizas of Douglas fir (Pseudotsuga menziesiiMirb.) by light and electron microscopy has allowed us to show the organization of the mantle. A three-dimensional structure of the fungal mantle is proposed. The outer plectenchyma is characterized by free hyphae; these hyphae are devoid of cytoplasmic contents. The inner plectenchyma shows closely interwoven hyphae; the fungal cells have a living aspect and a glycogen-rich cytoplasm.

ISSN:0008-4026    

DOI:10.1139/b79-276

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Various aspects of the growth form of seven species ofAlismaandSagittariawere investigated. Of the four studied in detail, all have a short, upright stem which undergoes apical bifurcation to form the inflorescence and a continuation vegetative axis. Each season, three inflorescences are initiated in a distinct developmental sequence while phyllotaxy of the successive vegetative phases continues uninterrupted. The symmetry and development of both inflorescence and continuation growth are precise and similar in the species studied. There is greater variation in the pattern of development of axillary buds. This includes second-order axes attached directly to the parent plant (Alisma triviale), a new plant formed by each axillary stolon some distance away (Sagittaria latifoliaandS. cuneata), or a whole sympodial system of stolon segments from each axillary bud as inSagittaria subulata. Seed germination and seedling stages are very similar, and all show spiral phyllotaxy from the outset. The pattern of organization of each species remains relatively constant within and between different populations.

ISSN:0008-4026    

DOI:10.1139/b79-277

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A comparative morphological study ofSagittaria lancifoliaandButomus umbellatusover their life cycles was undertaken. The two are very similar in adult form, characterized by apical bifurcation to form inflorescence and continuation growth as in other members of the Alismatidae.and also by rhizomatous growth with a subterminal apex. Embryo and seedling stages inS. lancifoliaare comparable to other members of the Alismataceae previously studied. Rhizomatous form and bilateral symmetry are secondarily acquired during ontogeny. The inflorescence is leaf opposed andS. lancifoliais organizationally similar to other species of Alismataceae with upright vegetative axes. From this, a sympodial interpretation of the rhizome may be made. In contrast, the bilaterally symmetric growth form inButomusis manifested from the start. The leaf-subtended inflorescence and other features of organization suggest that it cannot easily be compared withS. lancifoliaor other members of Alismataceae. Here, a stronger case may be made for a monopodial construction. Axillary bud distributions support these conclusions. In addition, both species branch by a relatively precocious lateral bud associated topographically with the inflorescence.

ISSN:0008-4026    

DOI:10.1139/b79-278

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The major flavonoid complement of theMinuartia rossiicomplex has been determined. Nine flavonoid glycosides have been identified based on the common aglycones quercetin and kaempferol and the rarerC-glycoflavone isovitexin. One compound (apigenin-6-C-arabi-nosylglucosyl 7-O-glucoside) was found to be of limited distribution, being present inM. rossiiandM. elegansand absent inM. austromontana. The flavonoid kaempferol 3-p-coumaroylglucoside found in the complex is relatively uncommon and therefore of chemosystematic interest. With respect to their flavonoid profiles, no differences were noted between the two chromosome races ofM. elegansand no geographical variation was observed in the three taxa of the complex. The genetics of isovitexin glycosylation are discussed and evidence for the probable existence of two additional glycosylation genes is presented.

ISSN:0008-4026    

DOI:10.1139/b79-279

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Alternaria brassicicolaandBotrytis cinereastimulated ethylene production in closed culture with floating leaf discs from cabbage (Brassica oleraceavar.capitata). Production withA. brassicicolahad an observed maximum at 18 °C and was speeded by preculturing the fungus on media containing cabbage components, but which contained little or no methionine.In the absence of cabbage tissue, both organisms demonstrated a latent capacity to generate ethylene from closed shake cultures of Czapek's medium containingL-methionine. WithA. brassicicolain a modified Czapek's medium (minus ferrous sulfate) containing 10−3 ML-methionine, there was a stimulation of ethylene production at 18 °C by the addition of Fe2+, Fe3+, Cu2+, ca. 8% carbon dioxide, or the potassium salt of gibberellic acid (GA3). WithB. cinerea, 4% carbon dioxide was stimulatory, 29% carbon dioxide was inhibitory, whereas less than 4% oxygen arrested the production of ethylene completely for 48 h.Results suggest that the nature of parasitism ofA. brassicicolaandB. cinereaon cabbage is characterized by a latent capability to cause the production of, and to produce, the plant-senescing hormone ethylene.

ISSN:0008-4026    

DOI:10.1139/b79-280

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The effects of short-term temperature fluctuations on net photosynthetic rates (Pn) are described for a single-cross corn (Zea maysL.) hybrid (Harrow 691). The hybrid was grown at 25 °C and subjected to 4 days at either 15 or35 °C, and then maintained at 25 °C. Genotypic differences in tolerance ofPnto low temperature were studied using 12 hybrids of different maturities grown at 25 °C and subjected to 4 days at 15 °C.Following low temperature treatment.Pnwas initially reduced by about 15% for leaves 5. 9. and 13 of hybrid Harrow 691. but completely recovered after 1 day at 25 °C. Following high temperature treatment, leaves 5 and 9 showed similar reductions inPnwhereas leaf 13 was not affected. The photosynthetic activity of the heat-stressed leaf 9 recovered after 1 day, but that of leaf 5 showed no recovery for 14 days at 25 °C.Among 12 hybrids.Pnof the newly matured leaf 7 was reduced after the low temperature treatment, but the reduction was more drastic for two late hybrids than for three early hybrids. Most hybrids showed complete recovery ofPnafter 1 day at 25 °C. but genotypic differences were evident. The results reported indicate that further evaluation of the amount of genetic variation in temperature stability in corn could be carried out usefully.

ISSN:0008-4026    

DOI:10.1139/b79-281

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Merimbla ingelheimense(van Beyma) Pitt is described for the anamorphic state ofTalaromyces avellaneusC.R. Benjamin, a holomorphic fungus. Diagnostic features are discussed, together with a key for distinguishingMerimblafromAspergillus, Geosmithia, Paecilomyces, Penicillium, andRaperia.

ISSN:0008-4026    

DOI:10.1139/b79-282

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Horizontally held flowering stalks ofEchinochloa colonumL. bend upwards as a result of cell elongation in the lower side of the leaf sheath base. Changes in the gravity vector are perceived by statocytes. All cells of the leaf sheath base, including the collenchymatous bundle cap fibres can elongate up to threefold in response to geostimulation. Very little growth takes place in upright nodes and in the upper halves of nodes during bending. The thick walls of the collenchymatous cells are uniformly rich in pectin and remain unlignified. Nonelongating collenchymatous cells accumulate electron-dense wall material in infoldings of the plasmalemma. Elongating cells become thin walled, unincorporated wall material disappears, and a narrow, electron-dense layer of wall forms. The walls thin evenly, although under polarized light the structure of the pits may give an appearance of uneven stretching. When the gravitational stimulus is removed, growth ceases, the walls rethicken, and the electron-dense layer disappears.

ISSN:0008-4026    

DOI:10.1139/b79-283

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A study of the fungal flora of soils, plant leaves, and litter was undertaken on the Truelove Lowland, on the north coast of Devon Island, N.W.T., Canada. A total of 53 taxa from 33 genera were identified, 27 from leaves and litter and 46 from soil, using soil-washing and plating as isolation methods. The predominant fungi on leaves and litter ofCarex stansandDryas integrifoliawere sterile fungi, associated withCladosporiuin, Phoma herbarum. Penicilliumspp., and yeasts. Sterile fungi,Penicilliumspp. andChrysosporium pannorumwere predominant in raised beach soils, whereas a new species ofCylindrocarpon, sterile fungi.Penicillium, andAspergillusspecies predominated in meadow soils. Use of direct observation methods showed that fungal biomass in meadow soils was much higher than in raised beach soils. In raised beach soils fungal biomass was heavily influenced by the distribution of cushion plants. In comparison with other tundra regions, the Truelove Lowland appears to have a moderately rich mycoflora, containing taxa common both in temperate regions and in other tundra soils. Total fungal biomass in Truelove Lowland soils was found to be low in comparison with many tundra regions.

ISSN:0008-4026    

DOI:10.1139/b79-284

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Nine human-pathogenic fungal isolates from Nigeria were cultured on Sabouraud dextrose agar prepared with seawater and solutions containing different concentrations of sodium chloride. Growth was determined by measuring colony diameter after incubation for a maximum of 15 days at 30 °C. The fungi grew and sporulated on seawater, Sabouraud dextrose agar, and Sabouraud dextrose agar containing up to 3.4% NaCl. Growth, however, decreased with increasing concentrations of sodium chloride in the basal medium. Little or no growth occurred in media containing 6.4% NaCl.Aspergillus fumigatusLink,Candida albicans(Robin) Berkh, andGeotrichum candidumLink remained viable for up to 8 weeks in distilled water, 0.85 and 1.7% NaCl solutions, 5 weeks in 3.4% NaCl and sterile seawater, and 4 weeks in 6.8% NaCl.

ISSN:0008-4026    

DOI:10.1139/b79-285

出版商:NRC Research Press    

年代:1979

数据来源: NRC