摘要:

Isolates of the wood-decaying basidiomycetePhellinus tremulaewere obtained from four different stands of aspenPopulus tremulain the south of Sweden. Studies were made of somatic incompatibility among all isolated within each site. No genet could be found in more than one tree. From one stand, two trees were felled and samples were taken from stem discs every half metre up to 13 m. Eight genets were isolated from the two trees, four in each tree. Fungal DNA was amplified from five isolates representing three different genets in one tree. The core sequence of M13 was used as primer. The results agreed with those of the somatic incompatibility test. Forty-five samples were taken from small twigs from healthy-looking branches and trees, and isolates ofPhellinus tremulaewere obtained from three of them. The likely route of infection ofPhellinus tremulaein aspen is discussed.Key words: somatic incompatibility,Phellinus tremulae,Populus tremula.

ISSN:0008-4026    

DOI:10.1139/b94-171

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Healthy 2- to 3-year-old twig pieces with adherent foliage were collected from 3- to 10-year-oldAcer macrophyllumat seven sites in coastal British Columbia and examined for the presence of endophytic fungi. Eighty-three percent of the leaves and 52% of the twigs were colonized by endophytic fungi. Fungal assemblages of leaves were dominated byPhomopsisspp., whereasDiplodina acerinawas most frequently isolated from twigs.Cryptosporiopsis abietina,Glomerella cingulata(withColletotrichum gloeosporioidesanamorph), andPhomopsisspp. also occurred quite frequently in twigs at some sites. No correlations between weather conditions and any of the endophyte species were detected.Diplodina acerinaandG.cingulatawere the only two species with a certain potential to be employed as mycoherbicides:D.acerinais distributed over most of its hosts' range, and frequency and density of colonization are high among and within trees and some degree of virulence is present; some formae speciales ofG.cingulataare already used as mycoherbicides.Key words: endophytic fungi, mycoherbicides,Diplodina acerina,Colletotrichum, fungal ecology.

ISSN:0008-4026    

DOI:10.1139/b94-172

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Three common bean cultivars (climbing ‘Negro Mecentral’, bushlike ‘Negro Mecentral’, and ‘Tendergreen’) were studied during seed maturity. A single dark period of a chilling treatment (4 °C, 12 h) resulted in a sizeable reduction of the photochemical and photosynthetic activities of the leaves during the seed maturity stage. Leaf net photosynthesis, transpiration rate, and stomatal conductance for water vapor were drastically reduced in ‘Tendergreen’ at 28 days after anthesis, but in bushlike ‘Negro Mecentral’ these values decreased until 30 days after anthesis. Chilling drastically reduced electron transport of freshly lysed chloroplasts isolated from bushlike ‘Negro Mecentral’ and ‘Tendergreen’ at 32 days after anthesis. This contrasts with climbing ‘Negro Mecentral’ plants, in which electron transport decreased progressively between 28 and 32 days after anthesis. Photophosphorylation rates at 32 days after anthesis were reduced by 31, 58, and 45% in climbing ‘Negro Mecentral’, bushlike ‘Negro Mecentral’, and ‘Tendergreen’ plants, respectively. Light-dependent proton uptake was more damaged in ‘Tendergreen’ (88%) at 32 days after anthesis than in bushlike ‘Negro Mecentral’ (31%) and climbing ‘Negro Mecentral’ (38%). Seed yield per plant tended to decrease with treatment in climbing ‘Negro Mecentral’ (45% at 32 days after anthesis) and in bushlike ‘Negro Mecentral’ (34% at 32 days after anthesis), whereas in ‘Tendergreen’ the yield apparently was not affected. However, seed weight and size of climbing ‘Negro Mecentral’ decreased following the treatment, while they increased in bushlike ‘Negro Mecentral’ and ‘Tendergreen’. Seed protein content increased dramatically at 28, 30, and 32 days after anthesis in treated bushlike ‘Negro Mecentral’ (52, 78, and 42%, respectively), but it did not change in climbing ‘Negro Mecentral’ and ‘Tendergreen’. In conclusion, the chilling effects on photochemical activities, seed yield, and seed composition of common bean plants at seed maturity vary according to cultivar and plant developmental stage.Key words:Phaseolus vulgaris, photosynthesis, chilling effect.

ISSN:0008-4026    

DOI:10.1139/b94-173

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Mitosis in the wheat pathogenTilletia caries(Basidiomycota, Tilletiales) was investigated by electron microscopy of serially sectioned, fast-frozen, freeze-substituted mitotic cells called ballistospores. A duplicated spindle pole body consisting of two identical, three-layered globular elements connected by a middle piece was attached to the extranuclear face of each nucleus at interphase. During mitosis, astral and spindle microtubules radiated from the globular elements that form the poles of an intranuclear spindle. At metaphase, chromosomes were interspersed with the nonkinetochore microtubules, and they were spread along the central two-thirds of the spindle. Each chromatid was attached to a spindle pole by a single, continuous, kinetochore microtubule. Postmitotic replication of the spindle pole body occurred during late telophase to interphase. Results from this study are presented in the form of a model of the mitotic spindle pole body cycle inTilletia, and this model is compared with the one previously reported forTilletiaand other basidiomycetes.Key words: electron microscopy, freeze substitution, mitosis, spindle pole body,Tilletia.

ISSN:0008-4026    

DOI:10.1139/b94-174

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Phoma etheridgeiis described and illustrated from isolates obtained from the bark of black galls and cankers of trembling aspen in Alberta. Comparisons are made withPhoma enteroleucaand several other mostly wood-inhabitingPhomaspp. using morphological, physiological, and molecular characteristics. A key is provided for the differentiation ofPhomaspp. that could potentially be isolated fromPopuluswood.Phoma etheridgeiproduced antifungal compounds that were strongly inhibitory in vitro to the aspen decay pathogenPhellinus tremulaeon agar, in liquid media and on aspen wood chips, and may play a role in the natural ecosystem as an antagonist toPhellinus tremulae.Key words:Phoma etheridgei, taxonomy, black gall, antifungal metabolites, biological control,Phellinus tremulae,Populus tremuloides.

ISSN:0008-4026    

DOI:10.1139/b94-175

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Purification of peanut (Arachis hypogaeaL.) peroxidase in milligram amounts is feasible through its isolation from spent medium of cultured cells. Using the same and modified approaches for another cultured dicot and a monocot yielded only low amounts of peroxidase for bean (Phaseolus vulgaris)and millet (Setaria italicaBeav.). We showed that the procedures used for millet rendered a purer fraction than the commercial crude fraction available for horseradish. The data suggest that cultured peanut cells in suspension culture are an ideal system for isolation of peroxidase in terms of the ease of purification and yield.Key words: peanut, bean, millet, peroxidase, purification, tissue.

ISSN:0008-4026    

DOI:10.1139/b94-176

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

UnlikeLycopodium laterale, which is polyplastidic during spermatogenesis,Lycopodium obscurumexhibits monoplastidy beginning in the early proliferative stages of antheridial development. Previous cell generations are polyplastidic and plastid fusion involving connective cylinders establishes the monoplastidic condition. Plastid and nuclear divisions are coordinated inL.obscurumwith the plastids positioned at opposite poles prior to spindle development. Unlike monoplastidic cell divisions with morphogenetic plastid migration and polarity in other lycophytes, mosses, and hornworts, however, the spindles inL.obscurumdo not originate from the plastid envelopes but from endoplasmic reticulum positioned against the plastid. In the final divisions, spindle microtubules emanate from structurally defined microtubule organizing centers that develop between the plastids and nucleus. Preceding the appearance of centrioles in the spermatid mother cell, the centrosomes comprise electron-dense granular matrices with associated vesicles and endoplasmic reticulum. Among archegoniate microtubule organizing centers, the discrete acentriolar centrosomes ofLycopodiummost closely resemble the microtubule organizing centers in moss spore development and the polar organizer of liverwort mitosis.Key words: annulate lamellae, centrosome,Lycopodium, microtubule organizing center, monoplastidy, plastid dividing ring.

ISSN:0008-4026    

DOI:10.1139/b94-177

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

As part of an extensive research programme that attempts to explain and quantify the known difference in drought tolerance of fourNicotiana tabacumL. cultivars, some aspects that may contribute towards the avoidance and tolerance of drought stress were investigated to evaluate overall resistance. The results presented emphasize the adaptive significance of effective leaf movements in determining drought tolerance, by reducing or preventing damage to the photosynthetic system caused by photoinhibition and direct heat damage. Leaf movement seemed to be achieved with greater efficiency by the drought-tolerant cultivars GS46 and Elsoma. Drought stress specifically influenced the carotenoid composition. A strong quantitative correlation existed between the formation of zeaxanthin in the xanthophyll cycle and the type of fluorescence quenching, which is indicative of nonradiative energy dissipation. The latter occurred to a lesser extent in the drought-tolerant cultivars GS46 and Elsoma. This phenomenon also indicated that the rate constant for nonradiative energy dissipation in tobacco remains relatively small in relation to the rate constant for fluorescence during drought stress. Furthermore, irrespective of their drought tolerance, it would seem that tobacco plants have a capability towards starch overproduction, though this was less pronounced in the drought-sensitive cultivars TL33 and CDL28. Owing to anatomical differences, resistance to water flow varied between the respective cultivars, as did the percentage intercellular spaces, both of which correlated positively with the slower decrease in water use efficiency and faster recovery upon rehydration of the drought-tolerant cultivars.Key words: carotenoid composition, chlorophyllafluorescence,Nicotiana tabacumL., mesophyll surface area, leaf movements.

ISSN:0008-4026    

DOI:10.1139/b94-178

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Species of the genusHymenomonas, with the exception of the freshwater speciesHymenomonas roseola, are marine littoral coccolithophorids, characterized by coccoliths of the tremalith type. A heteromorphic life cycle involving an alternation between coccolith-bearing cells and scale-bearing cells has been established forHymenomonas lacunain culture. The scaly cells are covered by two types of scales, morphologically distinct from those of the coccolith-bearing stage. Both scale- and coccolith-bearing stages may be motile or nonmotile. The number of chromosomes in coccolith-bearing cells is, however, about twice that in scaly cells as indicated by nuclear staining. Both life-cycle generations were also observed inHymenomonas coronata, and this type of heteromorphic life cycle could be general for all heterococcolithophorids with tremaliths.Key words: coccolithophorids,Hymenomonas, life cycle, Prymnesiophyceae.

ISSN:0008-4026    

DOI:10.1139/b94-179

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Leaf sheaths of susceptible and resistant (Pi-zt) near-isogenic lines of rice were inoculated withPyricularia oryzae(Magnaporthe grisea) and the host – parasite interactions in living tissues were continuously observed using fluorescence and bright field microscopy. Growth of invading hyphae in the resistant line was restricted within cells that underwent hypersensitive death during fungal penetration. Experiments using heat shock and NaAsO2treatments suggested that cell death alone is not responsible for restriction of hyphal growth within the penetrated cell. Fungal hyphae grew unimpeded in dead cells of treated tissue unless the dead cells had also developed the capacity to autofluoresce under blue light. Electron microscopic studies showed that hypersensitive cell death occurred specifically in the resistant line after penetration of the cuticle, and in some cases it occurred before cell walls were completely penetrated. In the susceptible line, wall appositions were induced in the epidermal cells at a similar stage of fungal penetration (i.e., before infection hyphae had reached the cell lumen). Inward indentation of the cuticle and cell wall and inward folding of the cuticle at the penetration site suggested that the cuticle was breached mechanically. Wall penetration appeared to be facilitated by enzyme action because the microfibrils of host cell walls around infection pegs were disorganized and nonhomogeneous in electron density.Key words: resistance, penetration, ultrastructure, autofluorescence, rice blast,Pyricularia oryzae(Magnaporthe grisea).

ISSN:0008-4026    

DOI:10.1139/b94-180

出版商:NRC Research Press    

年代:1994

数据来源: NRC