摘要:

Cone and seed development in Douglas-fir were studied from pollination until seed release in 1986. Cone abortion at, and shortly after, pollination was high, resulting from a combination of low temperatures and possibly high moisture and populations of microorganisms on cones. Seed potential averaged about 75 seeds per cone with 31 filled seed per cone, giving an average seed efficiency of 39%. The major loss of seed resulted from insufficient pollen in the ovules. Other causes were ovule and embryo abortion at various stages of development. The effects of prezygotic and postzygotic events on seed set are discussed with respect to the reproductive success of Douglas-fir.Key words: Douglas-fir, seed set, cone, ovule, development, abortion.

ISSN:0008-4026    

DOI:10.1139/b91-033

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Callus cultures of strawberry cv. Redcoat (2n = 8x = 56) initiated from greenhouse andin vitroleaf explants were examined at various culture periods for morphogenic response, changes in nuclear DNA content, and isozyme banding patterns of four enzymes. The flow cytometric analysis of nuclear DNA content revealed the occurrence of polyploid and aneuploid changes as a function of ageing of callus cultures. The calli initiated fromin vitroleaf explants were more prone to such changes than those initiated from greenhouse leaf explants. Thein vitromorphogenic ability of callus cultures was affected by the ploidy changes, but the latter were not the only cause for loss in regeneration potential of long-term callus cultures. The isozyme phenotypes of esterase, phosphoglucomutase, phosphoglucoisomerase, and leucine aminopeptidase did not change with the chromosomal variation in callus cultures.Key words: strawberry,Fragaria×ananassa, callus culture, flow cytometry, nuclear DNA content, isozyme.

ISSN:0008-4026    

DOI:10.1139/b91-034

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

An electron microscopic study was made of meiosis and the meiotic spindle pole body (SPB) cycle in germinating teliospores of the smut fungusSphacelotheca polygoni-serrulati. SPB development in prophase I and duplication in interphase I were studied in detail. During prophase, the globular elements of the biglobular SPB enlarged, became oblate in form, developed internal layering, and became associated with astral microtubules. The middle piece decreased in size and finally disappeared. Prior to metaphase I, the two oblate elements moved apart along the intact surface of the nuclear envelope, and the nuclear membrane bulged into the space between the two SPBs. Metaphase I – early telophase I and metaphase II – early telophase II SPBs were intranuclear, oblate spheroidal in shape, and traversed by an electron-dense disc. In interphase I, an electron-dense bar appeared in association with the nuclear side of the original SPB. The bar initially overlapped one edge of the electron-dense disc and later appeared at the side of the disc. The bar became one of the metaphase II SPBs. Similarities and differences between meiosis and SPBs inSphacelotheca polygoni-serrulati,Ustilago maydis,Ustilago esculenta,Tilletia foetida, and other heterobasidiomycetes are discussed.Key words: heterobasidiomycetes, Ustilaginales,Sphacelotheca, meiosis, spindle pole body, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b91-035

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A multivariate morphometric study ofAstersubg.Doellingeriasect.Triplopappus(Compositae: Astereae) was undertaken to assess the numbers and ranks of taxa that usefully could be recognized. The results of cluster, discriminant, and principal components analyses on a matrix of 362 plants by 11 characters indicated that four species level groups can be recognized:Aster inflrmus,A.reticulatus,A.sericocarpoides, andA.umbellatus. WithinA.umbellatus, analyses of a 12-character data matrix on an additional 140 plants and analysis of a second matrix consisting of the data on the 198 plants of the species included in the species-level study supported recognition of two varieties:pubensandumbellatus. The qualitative and quantitative differences between the two varieties were smaller than those among the four species. Using a key to the taxa produced from all results, the distributions of the four species and two varieties were determined from a large sample of herbarium specimens and a nomenclatural synonymy was developed. Some lectotypes and a neotype are designated. All taxa in the section are diploid 2n = 18; chromosome numbers for 42 individuals ofA.umbellatusare reported for the first time.Key words:Aster,Doellingeria,Triplopappus, multivariate morphometric study, Asterumbellatus, key.

ISSN:0008-4026    

DOI:10.1139/b91-036

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A new species ofIsoetes,I. prototypusfrom eastern Canada, is described. The morphology of the megaspores shows some similarity to those ofacadiensisandI.hieroglyphica, but the microspores have a spinulose network on their surface. The plants have straight and rigid leaves that resemble some forms ofI.macrospora. The species is diploid (2n = 22) and is found deep (± 2 m) in cool lakes in New Brunswick and Nova Scotia.Key words:Isoetes, new species, diploid, Canada, SEM.

ISSN:0008-4026    

DOI:10.1139/b91-037

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

We document diagnostic characteristics ofRoegneriaby which it differs from genera with which it has often been confused. Characteristics ofRoegneriaare the absence of underground runners; slightly curved and elongated rachis with long internodes, each rachis node bearing one spikelet only and often adhering to the internode, and inflorescence appearing more or less one sided because of the disposition of the spikelets; spikelet functionally disarticulating below the glumes; glume symmetric with nerves tapering in the apex; lemma with nerves tapering in the apex; and palea generally shorter than the lemma, and if equal to the lemma then the tip obtuse, truncate, or retuse. Genera difficult to separate fromRoegneriaareAgropyron,Elymus, andElytrigia; these share one or more characteristics but none have them in the same combination. We also stress the merit of recognizingRoegneriafor germ-plasm utilization.Key words:Roegneria, Triticeae, generic limits,Elymus,Agropyron,Elytrigia.

ISSN:0008-4026    

DOI:10.1139/b91-038

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Trees of apple (Malus domesticaBorkh.) with 'Starkspur Supreme Delicious' as the scion grafted on nine different rootstocks (Ottawa 3, M.7 EMLA, M.9 EMLA, M.26 EMLA, M.27 EMLA, M.9, MAC-9, MAC-24, OAR 1) were studied in their 8th and 9th years. Canopy seasonal development and its light interception followed by fisheye (hemispherical) photography showed that rootstock affected the amount of structural wood, the rate of canopy development, and final leaf area. However, rootstock did not affect the sigmoidal pattern of canopy development. Light interception was linearly correlated with tree dimensions and yield. Leaf net photosynthesis (Pn) of trees on dwarfing rootstocks tended to be lower thanPnrates of trees on more vigorous rootstocks. Rootstock did not affect the scionPnresponse to different illumination levels. Shoot leaves, spur leaves on spurs without fruit (S − F), and spur leaves on spurs with fruit (S + F) from trees on M.26 EMLA and OAR 1 showed no differences inPnrates. However, for both rootstocks, shoot leaves had the highestPnrate, S + F the lowest, and S − F leaves had intermediate values.Key words: light interception, fisheye photography, leaf type.

ISSN:0008-4026    

DOI:10.1139/b91-039

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A study of lodgepole pine (Pinus contortaDougl.) seeds following imbibition at 28 °C has shown that in the megagametophyte, RNA and DNA levels remained constant until 5 days after imbibition when a decrease occurred. In the embryo, increases in RNA and DNA occurred 2 and 5 days after imbibition, respectively. Incorporation of [3H]uridine into total RNA was maximum by 2 days after imbibition in both the megagametophyte and the embryo. Incorporation of [3H]leucine into buffer-soluble protein showed a similar trend for both organs except that maximum incorporation occurred by 3 days after imbibition. An electrophoretic analysis of buffer-soluble proteins synthesized following the incorporation of [35S]methionine showed similar patterns for both the megagametophyte and the embryo. In both organs, the synthesis of three subsets of proteins was recognized. One subset was synthesized in the mature seed. Synthesis continued through germination but was terminated prior to radicle emergence. Synthesis of a second subset coincided with radicle emergence and continued during early seedling growth. A third subset was synthesized constitutively throughout germination and early seedling growth.Keywords: nucleic acid synthesis, protein synthesis, seed germination, lodgepole pine.

ISSN:0008-4026    

DOI:10.1139/b91-040

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Fulvia fulva, the agent of leaf mould, is known to be a major parasite of tomato leaves in greenhouses. Its development is characterized by a biotrophic phase followed by a necrotrophic phase.Hansfordia pulvinatais a hyperparasite of this pathogen, but its destructive action is restricted by its inability to colonizeF.fulvaduring the biotrophic phase, before lesion formation. An integrated system to optimize the mycoparasitic activity ofH.pulvinatawas studied. The hyperparasite was tolerant to fosetyl-Alin situ. At a minimal concentration of 500 mg/L, the fungicide inhibitedF.fulvaspore germination after spraying on tomato leaves but did not have any effect during the necrotrophic phase. Thus, fosetyl-Al, which prevented reinfection, and the destructive hyperparasiteH.pulvinatahad complementary effects.Key words:Hansfordia pulvinata, fosetyl-Al,Fulvia fulva, integrated control, leaf mould, tomato.

ISSN:0008-4026    

DOI:10.1139/b91-041

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The study of the sorption curve representing the development of water content versus relative humidity, in barley seeds (cv. Thibaut), shows that water is present in three different states: constitutive water at less than 8.1%, absorption water between 8.1 and 10.9%, and free water at more than 10.9%. Along with these water states, radiosensitivity is respectively high, low, and high. The seeds detached from the rachis have less radioresistance than the attached ones. However this difference in behaviour is reduced when the water content is high (presence of free water). We also observed that growth was stimulated by weak doses of irradiation (20 Gy), whatever the water content.Key words: barley,Hordeum vulgare, radiosensitivity, water content, seeds, rachis.

ISSN:0008-4026    

DOI:10.1139/b91-042

出版商:NRC Research Press    

年代:1991

数据来源: NRC