摘要:

The phloroglucinol derivatives found in the rhizomes ofDryopteris intermediaGray, diploidD. "dilatata", andD. campylopteraClarkson, all from eastern North America, are compared and contrasted with those found inD. assimilisS. Walker,D. dilatataA. Gray, andD. spinulosaWatt from Europe, as well as diploidD. “dilatata” from Alaska. The presence or absence, and the morphology, of internal secreting hairs in these species was useful for comparing taxa and suggesting evolutionary patterns. Chromatographic analysis gives many more categories or finer divisions ofD. dilatatas.l. than does genome analysis, which has suggested thatD. assimilis, D. intermedia, and westernD. “dilatata” represent the same ancestral genome.

ISSN:0008-4026    

DOI:10.1139/b69-191

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A section of Holocene lake sediment in the Southern Boreal Forest of Manitoba was re-sampled, and the sedimentation rate (0.039 cm per annum) calculated from eight carbon-14 age determinations. Pollen accumulation rates were computed, and an absolute pollen frequency diagram constructed. It suggests modifications of an earlier reconstruction of vegetation, based on relative pollen frequencies. A spruce-dominated assemblage occurred from about 11 500 to 10 000 B.P., when there was a change to a treeless vegetation of a grassland type. This persisted until about 2500 B.P., with the possible interpolation of an aspen parkland phase from 6500 to 2500 B.P. The boreal forest in its present form (dominated by spruce, birch, and aspen, with local occurrences of pine, fir, larch, and oak) returned at 2500 B.P., presumably in response to a deterioration in climate (cooler and (or) wetter).

ISSN:0008-4026    

DOI:10.1139/b69-192

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Soluble uredospore proteins were isolated from physiologic races or isolates ofPuccinia graminisf. sp.avenae, P. graminisf. sp.secalis, P. graminisf. sp.tritici, P. reconditaf. sp.secalis, P. reconditaf. sp.tritici, P. coronataf. sp.avenae, andP. hordei. The protein extracts were subjected to polyacrylamide gel (disc) electrophoresis and the resulting patterns were compared.Patterns were assessed by two methods based onEfvalues and by a third method based on subjective assessment of color intensity of stained proteins. Assessments based onEfvalues differed for each method and were in almost total disagreement with conclusions derived by the third method.No useful inter-subspecific and interspecific comparisons were possible usingEf-based data because the host on which the rust was grown influenced the patterns. Evidence obtained by the third method of assessment contradicted this conclusion, for the host only appeared to influence color intensity and width of individual bands. Thus, using the color intensity method it was found that the differences between species were greater than between formae speciales, and the latter, with one exception, differed more than physiologic races. Differentiation between most physiologic races or isolates was impossible.The taxonomic significance of the protein patterns is discussed.

ISSN:0008-4026    

DOI:10.1139/b69-193

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Certain aspects of the life cycle ofWallrothiella arceuthobiiare detailed from field and microscopical observations. Infected fruits of the host often continue to develop for several weeks after spore dissemination. Sectioned material shows that the fungus tends to avoid the young embryo and endosperm, yet attacks other adjacent mistletoe tissues. Perithecial shape varies considerably between eastern and western North America. Some western specimens show periostiolar locules of unknown function. The genus may be related to Coryneliaceae.

ISSN:0008-4026    

DOI:10.1139/b69-194

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The vegetative shoot apex ofHelianthus annuuscontains a central zone in which the cell nuclei are relatively large and stain faintly in the Feulgen reaction. Excised apices in the vegetative state were supplied with thymidine-H3through their sterile, liquid culture medium. Autoradiography after 24 or 48 hours of feeding revealed no significant incorporation of the labeled precursor into central zone nuclei, but extensive incorporation in peripheral regions of the apex. It is concluded that during vegetative growth deoxyribonucleic acid (DNA) synthesis and mitosis are arrested in the central zone or reduced to an extremely slow rate. Microspectrophotometry, however, indicates that the central zone nuclei are not held at the 2C level. With the onset of flowering, cytological zonation disappears in the apex and the incorporation of thymidine-H3is uniformly heavy throughout the apical region.

ISSN:0008-4026    

DOI:10.1139/b69-195

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The palmCryosophila guagaraAllen bears three types of adventitious roots on the stems of young plants, prop roots, trunk roots, and crown roots. The latter two are modified into thorns; but crown roots are lacking in older plants. Crown roots arise endogenously near the apex of the stem and grow vertically downward in the stem tissues, emerging near the attachment of an enveloping leaf sheath. The root then changes its direction of growth at the site of leaf attachment, grows vertically upward to the top of the sheath, and ultimately gives rise to a pendulous, branched thorn. Trunk roots or spines arise as laterals from the bases of crown roots embedded in the tissues of the stem. The conversion of a root apex to a thorn involved the cessation of meristematic activity, the acropetal extension of tissue differentiation with an associated attenuation of the conical root apex, and the extensive development of cortical and stelar sclerenchyma. The root cap does not contribute to the thorn.

ISSN:0008-4026    

DOI:10.1139/b69-196

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

This study was conducted to determine the nature and extent of variation in cereal leaf rusts. Two different races of oat crown rust,Puccinia coronataf. sp.avenae, were recovered from a mixture of single-spored cultures of races 228 and 393. A further subculturing yielded nine non-parental virulence combinations, which could have resulted from somatic recombination.Single-spore isolates of race 228, avirulent on the oat variety Saia were increased, and screened on Saia. Eighty-seven susceptible infections were obtained from a total of nearly 40 000 infections. This variation could result from a high mutation rate.A unique form of variation was observed when Saia-virulent isolates of race 229 were subcultured. Approximately half the subcultures were virulent and half were avirulent on Saia. Further isolations from the avirulent subcultures were all avirulent. Serial propagation of race 229 continued to give cultures virulent and avirulent on Saia. A stable culture of race 229 virulent on Saia was not obtained. Cytological examination of this race 229 culture showed that most of the spores were dikaryotic. Aneuploidy or cytoplasmic inheritance might account for this variability on Saia.Uredial isolates of wheat leaf rust,Puccinia recondita, differing in virulence and color were also studied for the possible occurrence of recombinants. No recombinants were found in six mixtures, each consisting of two different uredial isolates.

ISSN:0008-4026    

DOI:10.1139/b69-197

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The mycorrhizal fungusCenococcum graniformecan be readily isolated from sclerotia that have been brushed clean and immersed in 30% H2O2for 10 to 40 minutes. Sclerotia are obtained from small soil samples wetted to a slurry that is swirled to remove the lightweight, sclerotia-containing fraction in a gold-panning type of process. Viable sclerotia sink in water whereas nonviable ones float, so the latter are easily eliminated. Sclerotia have been observed to form in agar cultures, especially those that have been allowed to desiccate slowly for 2 to 3 months.

ISSN:0008-4026    

DOI:10.1139/b69-198

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In this second part of a study of the species ofPucciniacompleting their life cycle on Heliantheae ['Ambrosiaceae'], six species are recognized. Two new species are described:Puccinia caborcensisParmelee is a brachy-form andP. sonoraeParmelee is a eu-form. Both occur onAmbrosia(=Franseria) in Mexico.P. franseriaeSyd., previously considered synonymous withP. splendensVize, is morphologically separable. The life cycle ofP. helianthellaeArth., from the first part of this study, is described as an unstable brachy-form. The usefulness of these rusts as an aid in the taxonomy of the hosts is indicated, and a rust species – host table is included. Each rust is illustrated by a photomicrograph from type material.

ISSN:0008-4026    

DOI:10.1139/b69-199

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In shoot apices ofPharbitis nil, cytohistological zonation is not clearly delineated at germination. With increase in age, zonation develops and the granular appearance of the cytoplasm disappears. After induction by a single 16-hour dark period the first recognizable sign of floral transition becomes evident on the second day, with increase in the mitotic activity of the apex. On the third and fourth days, the sepals are initiated and the petals and stamens are initiated simultaneously on the fifth day. On the sixth day the carpel primordia originate. Between the 11th and 12th days after the inductive dark period, the pollen grains develop and the style extends. Between the 19th and 20th days the epidermal cells of the stigma become secretory.

ISSN:0008-4026    

DOI:10.1139/b69-200

出版商:NRC Research Press    

年代:1969

数据来源: NRC