摘要:

Ionic amounts of S, P, K+, Ca2+, and Mg2+have been determined by chemical measures in different parts ofIsoetes setacea(shoot apical meristem, cortical zone, and central stele) for plants in normal growth, in drought resistance, and during rehydration. Study of modifications in the ionic amounts during experimental rehydration showed that the significant increase of K+, Ca2+, and Mg2+by the 24th h of experimentation was one of the earliest signals observed for the cells of the apical meristem (which are at that time blocked in G1presynthesis phase) as well as for the differentiated cells. By the 7th day of rehydration, just before their entrance into the synthesis phase, meristematic cells have recovered ionic rates equivalent to those measured for active plants. The same thing happens in the nonmeristematic tissues. This increase of ionic amounts in the whole plant can be explained by a differential entrance of ions with water. This new balance of the ionic amounts according to the pattern found in the active plants can be considered as a prerequisite event for the recovery of an active metabolism for a meristematic or differentiated cell in water stress.

ISSN:0008-4026    

DOI:10.1139/b86-288

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Using two barley cultivars, 'Hanna' and 'Russian No. 12', resistance toErysiphe graminisDC. f.sp.hordeiEm. Marchal induced by preliminary inoculation with a compatible or an incompatible race of the powdery mildew fungus was examined with respect to cellular responses. When the primary leaves of barley seedlings were preliminarily inoculated with a compatible or an incompatible race on the abaxial leaf surface, they became resistant to the disease caused by challenge inoculation with the same pathogen on the adaxial surface. The resistance induced was expressed as decrease of fungal penetration and restriction of hyphal growth. These phenomena seemed to be attributable to the increase of papillae or papillalike structures which do not seem to be responsible for the race-specific resistance. On the basis of these results, it is suggested that the resistance induced may be different from race-specific resistance.

ISSN:0008-4026    

DOI:10.1139/b86-289

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Suillus pictuswas consistently associated with tuberculate ectomycorrhizae (tubercles) onPinus strobusin North Carolina. Histological, cultural, and chemical reaction studies were used to examine this association. Tubercles were examined by light and scanning electron microscopy. Clamp connections, a reduced to absent tannin layer, and appressed mantle hyphae were observed. Naturally occurring rhizomorphs ofSuillus pictusand tubercles have a similar morphology consisting of an outer pseudoparenchymatous sheath, large vessel-like cells, and a prosenchymatous layer between the sheath and the vessel-like cells. Similar macroscopic chemical color reactions to 10% FeSO4, 15% KOH, concentrated NH4OH, concentrated H2SO4, and Melzer's reagents were observed on rhizomorphs ofS.pictusand tubercles, surface of tubercles, and stipes ofS.pictus. Chemical color reactions and growth characteristics ofS.pictusand the tubercle mycobiont were similar on different agar media.

ISSN:0008-4026    

DOI:10.1139/b86-290

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Life histories of two ligulate forms ofDesmarestiawith different phylloid width from one site on the Canadian Pacific coast were studied in culture. Meiospores from a form with narrow phylloids germinated into monoecious gametophytes. Meiospores from a form with broad phylloids developed into dioecious gametophytes, showing sexual dimorphism characteristic for dioecious species ofDesmarestia. The two growth forms also differed in culture conditions required for gametogenesis. We conclude that at least two different species of ligulateDesmarestiaoccur on the Pacific coast of North America.

ISSN:0008-4026    

DOI:10.1139/b86-291

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Twenty-nine vegetative compatibility groups (vcgs) were identified among 297 isolates of the fungus causing soybean stem canker in the southeastern United States (southernDiaporthe phaseolorum). Of the isolates characterized, 79% were from one of the vcgs described (group 1). Barrage zones formed between isolates from different vcgs when grown on potato dextrose agar, and also formed, but not always distinctly, on cornmeal agar, Czapek-Dox agar, lima bean agar, and malt agar; barrages did not form on Sach's agar or water agar. Two types of evidence suggested that southernD.phaseolorumis homothallic. Perithecia and viable ascospores were produced by single ascospore isolates, and ascospores produced by mass isolates were always of the same compatibility group as the parental mass isolate.

ISSN:0008-4026    

DOI:10.1139/b86-292

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Based on cell wall texture of root hairs, two groups can be distinguished within the 10 species ofEquisetumlisted inFlora Europaea. This distinction coincides with the division of the genusEquisetuminto two subgenera:Equisetum(horsetails) andHippochaete(scouring rushes). All species of the subgenusEquisetumhave a helicoidal cell wall texture in young growing root hairs as well as in full-grown hairs. All species of the subgenusHippochaetedeposit an additional inner cell wall layer against this helicoidal layer when elongation has stopped. The microfibrils in this additional layer do not form a helicoidal texture, but are helically arranged, forming a Z-helix. The presence of a helical layer in full-grown hairs is not a prerequisite for growth in soil, but an exclusively helicoidal root hair wall texture might be favourable for life in water. The wall texture is not influenced by the consistency of the substratum.

ISSN:0008-4026    

DOI:10.1139/b86-293

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Anixiopsis biplanatasp.nov. is described as a new ascomycete isolated from soil at an altitude of 3100 m in Nepal. It is heterothallic and characterized by small, reddish brown ascospores (4 × 3 μm), which under the light microscope seem subrectangular to hexagonal in side view and appear smooth walled. Under the scanning electron microscope, however, they are tire shaped, ornamented with an equatorial reticulum and with two smooth, flat, lateral discs. Its anamorph is aChrysosporium.Anixiopsis biplanatais briefly compared with the three other species already included in the genusAnixiopsisHansen.

ISSN:0008-4026    

DOI:10.1139/b86-294

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Spartina alternifloratissue, either in the absence or presence of a nitrogen supplement, was inoculated with a single-species or a mixed-species inoculum of salt-marsh fungi. After 42 days of incubation at 25 °C, lignocellulose decomposition was determined by measuring the amount of residual total lignocellulose, cellulose, hemicellulose, and lignin. A two-way analysis of variance of these results indicated an interaction between fungal treatments and nitrogen treatments. Pairwise comparisons of mean residual weights showed that all individual and mixed fungal inocula resulted in significant degradation of the total lingo-cellulosic, cellulosic, and hemicellulosic fractions ofSpartinatissue with levels of decomposition ranging from approximately 16 to 40%, depending on the fungal – nitrogen treatment and the cell wall fraction examined. Lignin degradation was not detected for any of the treatments. Cultures with a mixture of fungi showed less decomposition than was observed for the most efficient decomposer when it occurred alone.

ISSN:0008-4026    

DOI:10.1139/b86-295

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The aim of the present study was to investigate theAlnusroot surface using seedlings grown axenically. This study has focused on root zones where infection by the symbiotic actinomyceteFrankiatakes place. The zones examined extend from the root cap to the emerging root hair zone. The root cap ensheaths theAlnusroot apex and extends over the root surface as a layer of highly flattened cells closely appressed to the root epidermal cell wall. These cells contain phenolic compounds as demonstrated by various histochemical tests. They are externally bordered by a thin cell wall coated by a thin mucilage layer. The root cap is ruptured when underlying epidermal cells elongate, and cell remnants are still found in the emerging root hair zone. Young emerging root hairs are bordered externally by a cell wall covered by a thin mucilage layer which reacts positively to the tests used for the detection of polysaccharides, glycoproteins, and anionic sites. The characteristics of theAlnusroot surface and the biological function of mucilage and phenols present at the root surface are discussed in relation to the infection process.

ISSN:0008-4026    

DOI:10.1139/b86-296

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A culture method is described which allows the continuous supply of fresh liquid medium and which prevents the accumulation of toxic metabolites. Development of maize embryos and endosperm after various periods ofin vitroovary culture was studied by light and electron microscopy. Using this method the ultrastructural features of embryo developmentin vitrowere similar to those ofin vivoembryos. In contrast, the formation of endosperm was irregular with the absence of cellularization of the inner endosperm being frequent. In some cases, only the endosperm developed without any indication of embryo formation. In a calcium-depleted medium, embryo development was normal but again, endosperm formation was aberrant. No cells were formed in the central part of the endosperm and near the placental region degeneration took place, resulting in vacuoles with dark inclusions, clumps of rough endoplasmic reticulum membranes, and cellular breakdown. The events occurring afterin vitroculture strongly resemble those taking place after intergeneric crosses or crosses between diploid and tetraploid strains. It is concluded that defective endosperm development is probably the main factor for the failure of embryo development.

ISSN:0008-4026    

DOI:10.1139/b86-297

出版商:NRC Research Press    

年代:1986

数据来源: NRC