摘要:

A key to 13 known species is given, followed by descriptions and illustrations of the perfect and imperfect states of each species. The imperfect states are referred to the form generaChrysosporiumandTrichophyton. The nameTrichophyton flavescensis proposed for the conidial state ofArthroderma flavescens.

ISSN:0008-4026    

DOI:10.1139/b71-216

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Since previous investigations had suggested that kinetin, like auxin, may initiate DNA synthesis in tobacco pith cells, a study was undertaken to learn whether the observed incorporation of tritiated thymidine into nuclear DNA in the presence of kinetin could be explained by different experimental factors.Pith tissues were isolated and allowed to rest a few days after excision and they were then placed on White's basic medium or on that medium supplemented with either one or both of the growth regulators in the presence of tritiated thymidine.The results of those studies, obtained by radioautographic and liquid scintillation counting methods, showed no statistically significant differences between pith tissues kept on the control medium and those on kinetin-containing medium. Similar tissues placed on an auxin or auxin- and kinetin-containing medium showed, as expected, a significant incorporation of tritiated thymidine into the DNA of pith cell nuclei.

ISSN:0008-4026    

DOI:10.1139/b71-217

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Seedlings derived from field-collected seed from the United States, Mexico, and Central America were tested for frost hardiness under laboratory conditions. U.S. seedlings grown under four controlled conditions demonstrated greatest frost hardening under cool temperatures and short day lengths. Seedlings representing northernmost U.S. collection sites developed greater frost tolerance than seedlings representing southern U.S. collection sites. In comparing United States, Mexico, and Central America seedlings, the U.S. material showed greatest frost tolerance with Mexico and Central America demonstrating similar hardiness. The application of plant hormones (natural gibberellic acid and artificial AMO-1618) produced opposite effects on U.S. seedlings derived from Connecticut and Florida seed. The Connecticut seedlings demonstrated greatest frost tolerance in all treatments. Demonstrated frost tolerance differences among United States, Mexico, and Central America populations strongly indicate selection of frost hardy races in habitats with severe frost conditions.

ISSN:0008-4026    

DOI:10.1139/b71-218

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A survey was made of the flavonoid components inDicentra canadensisto investigate its relationship with other species in the genus. This study supports the view thatD. canadensisis most closely allied toD. cucullaria. Flavonoids suggest an even closer alliance between the two than does morphology, while alkaloid data reported in the literature would suggest a more distant one. Thus, the degree of relationship supported by morphological evidence is intermediate to what is supported by two different types of biochemical evidence. A large proportion of the total flavonoids inD. canadensisis detected with considerably less than 100% frequency within the species. This variability may reflect some genetic variability between populations, and is almost certainly due in part to the difficulty in detection of weaker spots.

ISSN:0008-4026    

DOI:10.1139/b71-219

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A hybrid betweenOryzopsis hendersoniiandStipa lemmoniiis reported and formally described. In a population in central Washington where the two parent species are sympatric 12 hybrid plants were found. The hybrids are morphologically and anatomically intermediate;O. hendersonii, which occupies drier sites, has xeromorphic modifications in the leaves not found inS. lemmonii. Both parents and the hybrid have 2n = 34 chromosomes. Meiosis in the hybrid is abnormal with some unpaired chromosomes, clumping of the chromosomes at diakinesis, and lagging univalents at later stages. Univalents tend to divide synchronously at anaphase I, following the division of bivalents. An average of about 11 bivalents is determined. These studies may be interpreted as supporting the transfer of thisOryzopsistoStipawhich is presented here, and it is suggested that several species ofOryzopsishave evolved independently from stipoid stock.

ISSN:0008-4026    

DOI:10.1139/b71-220

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The races of wheat stem rust found in Canada and identified by the "standard" and "formula" methods are described. Seven races or race groups made up 90.8% of the isolates. In 1964 a new system of race identification was introduced. It makes use of virulence formulas consisting of the numbers of effective resistance genes in the numerator and ineffective genes in the denominator. Resistance genesSr6, Sr8, Sr9a, Sr9b, andSr13confer resistance to most isolates obtained since 1964, but no single gene confers resistance to all isolates. Experience shows that 250 isolates per year are sufficient to establish the trends of prevalence of the main races. The detection of rare, new combinations of virulence requires screening varieties carrying combinations of resistance genes. The main races in the past 50 years have been 56 and 15B. Race 56 is uniform with a single subrace but 15B is variable with many subraces. There is no evidence that unnecessary virulence is harmful or that "stabilizing selection" is operative in Canada, nor is there evidence that virulence on resistance genesSr6andSr11is harmful to the rust.

ISSN:0008-4026    

DOI:10.1139/b71-221

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Chromatographic analyses of the phloroglucinol derivatives of 86 collections comprisingDryopteris filix-mas(L.) Schott (4x),D. arguta(Kaulf.) Watt (2x),D. marginalis(L.) A. Gray (2x), and the hybridsD. filix-mas×marginalis(3x),D. cristata×marginalis(3x),D. goldiana×marginalis(2x), andD. intermedia×marginalis(2x) in North America is presented. Material ofD. filix-masfrom the West differed from that collected in the East. The western material was rich in filixic acid, and had a chromatographic spectrum similar to EuropeanD. filix-mass. str.D. marginalisis lacking filixic acid, and is not closely related toD. filix-masbased on chromatographic evidence. Methylene-bisaspidinol, a compound not previously found inDryopteris, was isolated fromD. marginalis. D. argutacontains filixic acid, and has a chromatographic pattern close to that ofD. abbreviata(DC.) Newman, which in turn is one of the ancestors ofD. filix-mass. str. in Europe. The influence ofD. marginalisin the phloroglucinol spectrum of the interspecific hybrids studied was very strong except in the hybridD. filix-mas×marginalis.

ISSN:0008-4026    

DOI:10.1139/b71-222

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The view that periclinal cell divisions cause the initial protrusion of a leaf primordium may be tested by using ionizing radiation to prevent cell divisions without preventing growth. After receiving 800 krad of gamma rays, wheat grains containing embryos with three leaf primordia produce seedlings in which a fourth protrusion of the shoot apex forms unaccompanied by cell divisions. This protrusion without periclinal divisions occurs in the same phyllotactic position as that of the fourth leaf primordium in which periclinal divisions occur. In addition to proper phyllotactic position, the protrusion without cell divisions is formed by the outermost cell layer, as is the initial protrusion of a typical leaf primordium of wheat; moreover, the initial number of cells involved is the same in both kinds of protrusions. Therefore the fourth protrusion in seedlings from irradiated grain is interpreted as the initial protrusion of a leaf primordium that formed without periclinal cell divisions. Measured along the axis of greatest extension, the protrusions without cell divisions represent about a four- to eight-fold increase over the anticlinal dimension of the surface-cell layer in the embryo. These protrusions do not develop further. The absence of cell divisions limits the extent of primordial growth, but does not prevent its inception. Periclinal cell divisions do not cause the initial protrusion of a leaf primordium.

ISSN:0008-4026    

DOI:10.1139/b71-223

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Phlyctidium scenedesmiFott, a parasite ofScenedesmus quadricauda, was observed on this host and onPediastrum boryanumin School Bay of the Delta Marsh during the summers of 1966, 1967, and July 1968. During the summer of 1966 the fungus simultaneously attacked both host populations. Despite the fact that the algae were multiplying rapidly, the fungus was able to attack and kill host cells. At the time of the fungus maximum on July 24, 43% of thePediastrumcoenobia and 46% ofScenedesmuscoenobia supported fungus thalli. Thereafter, the host populations and the chytrid declined. Scattered chytrid thalli were observed on the low algal populations, however, even as late as October 9. During 1967, neither alga was as abundant as the year before and infection byP. scenedesmiwas sparse too. In 1968, bothPediastrumandScenedesmusachieved large maxima, butPhlyctidiumwas observed briefly only at the beginning of July.

ISSN:0008-4026    

DOI:10.1139/b71-224

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Cyathus crassimurussp. nov. from Hawaii is described, illustrated, and compared withC. pallidusandC. intermedius.

ISSN:0008-4026    

DOI:10.1139/b71-225

出版商:NRC Research Press    

年代:1971

数据来源: NRC