摘要:

Spiniferomonas andersoniisp.nov. (Chrysophyceae) is described from Marjorie Lake, Alberta, Canada. The cell is distinguished by the number, position, and basal characteristics of the spines. The present distribution ofSpiniferomonasbased on electron microscope observations is also given.

ISSN:0008-4026    

DOI:10.1139/b79-073

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Ochracine was isolated from culture filtrates ofSeptoria nodorumBerk. (Berk.), a pathogenic fungus of wheat. At concentrations ranging from 25 μg/mL it inhibited the growth of wheat and rice seedlings and the 'de novo' synthesis of α-amylases by the aleurone layers of wheat. These effects were not reversed by increased concentrations of gibberellic acid.Between 2.5 and 10 μg/mL, ochracine exhibited a synergistic effect with exogenous gibberellic acid on the same physiological phenomena. For these last concentrations, the results suggest an increased sensitivity of rice seedlings and wheat aleurone layers to exogenous gibberellic acid as a result of changes in tissue permeability.

ISSN:0008-4026    

DOI:10.1139/b79-074

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Collections of epilithic, epipelic, epiphytic, and epipsammic algae were made from the littoral zone of 21 lakes and streams in the Northwest Territories during 1975 and 1976.Tabellaria flocculosawas the predominant species in the epilithon and epipelon, reaching maximum densities of 0.5–2.5 × 109 μm3/cm2depending on watercourse. It was followed in importance byAchnanthes minutissima, Naviculaspp., andNitzschia frustulum, all of which occurred at densities of 0.1–0.3 × 109 μm3/cm2. While the only two common taxa in the epiphyton,A. minutissimaandT. flocculosa, maintained populations of 1.0–1.3 × 109 μm3/cm2, the most frequently encountered epipsammic species,Amphora ovalisvar.pediculus, Fragilaria construensvar.venter, Achnanthes minutissima, andAchnanthes pinnata, reached maximum levels of 4 × 107 μm3/cm2. The growing season for the attached flora extended from June to October throughout the study area. All four communities displayed a unimodal growth curve during this period, reaching maximum abundance in either July or August. The end of the growing season came during the middle of October when the collection sites were frozen to the bottom.

ISSN:0008-4026    

DOI:10.1139/b79-075

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Anther ontogeny of a genic male-sterile mutant (ms10/ms10) and a related fertile cultivar ofZeawas studied from the primordial stage through to tassel maturity. From material glutaraldehyde–formalin fixed, OsO4postfixed, and plastic embedded, light microscopy of 0.7-μm sections revealed no developmental differences between the two until the young microspore stage. Vacuolation or cytoplasmic disintegration of tapetal cells was detected in male-sterile anthers at this stage. Disintegration of microspores was not detected until the intermediate microspore stage. By the young pollen stage, tapetal cells were highly disorganized and degeneration of the middle layer and endothecium was apparent. No endothecial wall thickenings developed in male-sterile anthers.In normal anther development inZea, endothecial thickenings are found only at the anterior and posterior ends of the anther. A highly ridged anther cuticle, which is essentially absent in male-sterile anthers, is a common feature of fertile flowers. Anther dehiscence involves a separation of the epidermis from the underlying parenchyma of the connective to form a large pollen cavity from the two microsporangial locules. This process does not involve endothecial fibrous wall thickenings as they are not present over the bulk of the anther. Formation of the anterior pore is a separate process which involves changes in the endothecium wall thickenings.During normal anther development starch accumulates in the endothecium and epidermis at the precallose stage and disappears during the young microspore stage. No differences were noted in the male-sterile anthers. During the formation of normal pollen, considerable starch accumulation is evident. However, none is deposited at this late stage in the male-sterile anther.

ISSN:0008-4026    

DOI:10.1139/b79-076

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Lupinus albusL. inoculated at 6 weeks andL. luteusL. at 11 weeks by stem injection with a spore–mycelium suspension ofVerticillium albo-atrumReinke and Berth. produced 2.5 and 6.8% infected seeds, respectively. Other methods of inoculation failed to produce seed infection. The pathogen was present internally in infected seeds ofL. luteus, but inL. albusit was superficial. Histological observations indicated that plugs of amorphous material in infected vessels, and branching of the vessels, may serve as barriers to seed infection. Even the low levels of seed infection observed may have economically significant epidemiological implications.

ISSN:0008-4026    

DOI:10.1139/b79-077

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Several different expressions of male sterility were observed in the plants sampled for the study of pollen and anther development in the third substitution backcross generation to intermediate wheatgrass. These included (1) pollen abortion following engorgement with starch, (2) abortion of microspores with exine abnormalities (found most often in plants with a high degree of meiotic irregularities), (3) abortion of microspores with normal exines, (4) release at anther dehiscence of normal-appearing late vacuolate microspores, (5) enlargement of one of the parietal layers of the anther, and (6) tapetal abnormalities, including orbicular wall malformations. Anthers from plants which were male sterile or partially male sterile and meiotically irregular were shorter than anthers from fertile or partially male-sterile, meiotically regular plants.Definite statements about specific causes of the male sterility could not be made. Meiotic irregularities may be involved in some of the male sterility, and exine malformations appeared to be directly related to sterile microspores. Tapetal disturbances were observed infrequently. Probably the consequences of several factors were observed in the backcross material.

ISSN:0008-4026    

DOI:10.1139/b79-078

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Studies have been initiated on the occurrence of vesicular–arbuscular mycorrhiza (VAM) in plant communities of revegetated mine spoils and undisturbed areas of the Red Desert of Wyoming. It was found that the majority of plants in undisturbed environments in this area are mycorrhizal. On disturbed sites, no mycorrhiza were encountered. Of interest for both the undisturbed and disturbed communities was the predominance of plants belonging to the family Chenopodiaceae. The major difference between the plant species encountered in each community is associated with their reproductive strategy, as well as whether the plants possessed VAM. The major species encountered on undisturbed sites areAtriplex gardneri, At. confertifolia, Ceratoides lanata, Grayia spinosa, Kochia americana, andSarcobatus vermiculatus, all possessing mycorrhiza.Halogeton glomeratuspredominated in disturbed sites and did not possess VAM. The role of VAM in both succession and reproductive strategies of plants is also discussed.

ISSN:0008-4026    

DOI:10.1139/b79-079

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Ascospore germination ofEutypella parasiticaDav. and Lor. occurred over a temperature range of 12 to 38 °C. Over 90% of the spores which failed to germinate at lower temperatures germinated within 24 h when placed at 24 °C. Percent germination of ascospores varied in the presence of sugar maple and red maple tissue extracts. Germination was best in the presence of outer bark, sapwood, and leaf tissue of sugar maple and red maple and was poorest in the presence of fresh inner bark tissue excised from red maple. Germ-tube development also varied with type of tissue and treatment of tissue. Long, slender, branching germ tubes developed from spores in the presence of nonsterile leaf, bark, and sapwood, whereas short, thick germ tubes developed in the presence of sterilized leaf tissue and sterilized red maple bark. Age of wounded tissue also influenced percent germination of ascospores. Generally germination was higher when pH of these tissues was greater than 5.6. Mycelial growth was best at 29 °C. Growth rate was influenced by type of medium. Both sugar maple and red maple bark incorporated into agar media had a significant inhibitory effect on diameter growth of the fungus when compared with growth on nonamended media.

ISSN:0008-4026    

DOI:10.1139/b79-080

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Urediospore infection byMelampsore linion stems or leaves ofLinum usitatissimumproduced uredia which quickly converted from urediospore to teliospore production. The telium was composed of a palisade of laterally united, sessile, prismatic teliospores (ca. 50 × 6 μm) positioned between the epidermis and the stem cortex. Teliospores were induced to germinate by subjecting telia to a series of freeze–thaw and wet–dry cycles. Germination began after 6–10 such cycles and continued until 20–24 cycles had been performed. Teliospores germinated apically to form basidia and smooth, ovate to elliptical basidiospores (ca. 6 × 5 μm). Basidiospore germlings penetrated directly through the host epidermis and formed intercellular and intracellular hyphae. The haploid intracellular structures formed were irregular and hypha like, often septate, and occasionally grew into adjacent host cells. Several morphological variants of intracellular hyphae were observed; all such structures were distinct from the more specialized dikaryotic haustoria derived from either dikaryotic aeciospore or urediospore infections. Development of pycnia occurred primarily in the substomatal cavities of leaves. Flexuous hyphae extended through stomata; concomitantly, pycniospores produced in chains from a palisade of pycniosporophores exuded through the stomata onto the leaf surface in droplets of honeydew. Pycniospores were smooth, ellipsoidal, and ca. 3 × 1.5 μm. Caeomoid aecia developed on both sides of flax leaves and on stems. Short irregular chains of aeciospores alternating with smaller wedge-shaped intercalary cells were produced from sporogenous hyphae at the base of aecia. Mature aeciospores were globose to ovate (ca. 16 × 13 μm) and were densely ornamented with smooth, cog-like verrucae.

ISSN:0008-4026    

DOI:10.1139/b79-081

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Light microscopy and transmission and scanning electron microscopy were used to study the development of uredia ofMelampsora lini. Uredia were produced 6–10 days after inoculation with urediospores ofM. lini. Uredium ontogeny began with the formation of a uredium initial from a hyphal plexus in a substomatal cavity. The hyphae oriented vertically and expanded; the enlarged ends divided to form a palisade of uredial initial cells. These cells divided into basal and terminal cells. Each terminal cell divided transversely to form a peridial and an intercalary cell; the basal cell became the sporogenous cell. The intercalary cells disintegrated early in the expansion of the uredium and released their contents into the intercellular matrix. The sporogenous cell, usually swollen at one end, gave rise by budding to successive sympodially produced spore buds which elongated and divided transversely to form pedicels and immature spore cells. As the spores matured the pedicels shriveled and became separated from the urediospores. Elongated, often capitate, paraphyses formed throughout the uredium and functioned to rupture the peridium and epidermis which covered the immature uredium. The peridium and the intercalary cells formed only once during ontogeny of the uredium, this being associated with only the first generation of urediospores. The intercalary cells were disrupted during uredium ontogeny, and most of the peridial cell layer was sloughed off, along with the overlying epidermis, upon rupture of the latter. The paraphyses were permanent and remained in the uredium throughout its functional life. Successive generations of urediospores arose within the same uredium from spore buds produced sympodially from the original sporogenous cell but without forming additional peridial or intercalary cells.

ISSN:0008-4026    

DOI:10.1139/b79-082

出版商:NRC Research Press    

年代:1979

数据来源: NRC