摘要:

The effects of shoot moisture content, region of shoot, age of shoot, temperature, relative humidity, and soil moisture content on the development of cankers caused byCytospora chrysosperma(Pers.) Fr. were studied inPopulus trichocarpaTorr. and Gray,P. ×canadensisMoench 'Regenerata', andP. ×canadensis'Robusta Bachelieri'. Within the range studied, canker growth varied proportionally with temperature, and inversely with shoot moisture content, relative humidity, and soil moisture content. Canker growth was greater inP. trichocarpathan in the two hybrids, which did not differ significantly from each other. Canker growth was less in 8-month-old than in 10- and 12-month-old shoots of the hybrids, but cankers onP. trichocarpashowed no differences in this respect. The critical bark moisture deficit for infection was least inP. trichocarpa, intermediate inP. 'Regenerata', and greatest inP. 'Robusta'. The critical bark moisture deficit was greater, and the incubation period was shorter, in the upper part than in the lower part of the shoot.

ISSN:0008-4026    

DOI:10.1139/b62-120

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

A comparison was made betweenPopulus trichocarpaTorr. and Gray,P. ×canadensisMoench 'Regenerata', andP. ×canadensis'Robusta Bachelieri' with respect to shoot moisture relations and anatomy. The two hybrid varieties had slower rates of moisture loss and had higher wood moisture contents throughout most of the year thanP. trichocarpa. The bark and wood moisture content of the three varieties was lower during dormancy than in the growing season. The upper region of the shoots had lower bark and wood moisture contents than the basal region during dormancy, but the reverse was true in summer. In all varieties, there was a significant positive correlation between wood and bark moisture content. Compared withP. trichocarpa, the two hybrids had larger piths, wider vessels, longer phloem rays, wider sieve tube zones, and thicker periderms;P. 'Robusta' had fewer lenticels. The upper region of the shoots had a wider pith, thicker bark, thinner periderm, and more lenticels than the basal region. The differences in moisture relations and anatomy of the three varieties suggest an explanation for the observed greater resistance to canker disease caused byCytospora chrysosperma(Pers.) Fr. in the hybrids than inP. trichocarpa.

ISSN:0008-4026    

DOI:10.1139/b62-121

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Nutritionally exacting mutants ofCochliobolus sativus, a fungus with multinucleate, multicellular spores, were readily isolated by a filtration enrichment method. The method is similar to one described by Fries and is based upon the differential growth of auxotrophs and prototrophs in minimal medium. Most of the prototrophic propagules were removed by filtration. Propagules in the filtrate were concentrated by centrifugation, plated on complete medium, and subsequently tested for nutritional requirements.In comparative studies on four methods of isolation, namely, total isolation, mass transfer; total isolation, hyphal-tip transfer; filtration enrichment, mass transfer; and filtration enrichment, hyphal-tip transfer, the yield of auxotrophic mutants was 0, 0.04, 1.16, and 1.83%, respectively.

ISSN:0008-4026    

DOI:10.1139/b62-122

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

The area of a fully-grown leaf lamina varied according to its position on the stem, and the temperature, light intensity, and photoperiod under which the plant was grown.In continuous illumination, raising the temperature by 5° intervals between 10 and 25 °C, resulted in progressively higher rates of leaf initiation, emergence, and expansion. The length of the lamina increased with each increase in temperature, but the breadth and thickness decreased. The greatest area of individual leaves was formed at 20 °C. Each increase in light intensity over the range 200, 500, 1000, 1750, and 2500 ft-c resulted in higher rates of leaf initiation, emergence, and expansion, and increases in breadth and thickness, but a decrease in length. The greatest area was formed at 1000–1750 ft-c.An increase in daylength from 8 to 24 hours increased leaf length, breadth, and area. This was a photoperiodic effect, unlike the increase in thickness with increased daylength, which was related to the total light energy received.Changes in leaf shape under different environmental conditions were not directly related to changes in leaf dry weight. A control of leaf growth by hormonal mechanisms sensitive to photoperiod seems more probable than does control by internal competition for assimilates among developing leaves.

ISSN:0008-4026    

DOI:10.1139/b62-123

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Phlebopus lignicola(Kallenbach) Moser is the second species of Boletaceae to fruit in culture. The developmental stages and the histology of the fruit bodies are described and compared with those ofPhlebopus sulphureus(Fr.) Singer.

ISSN:0008-4026    

DOI:10.1139/b62-124

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

A simplified procedure for demonstrating the parasexual cycle is presented. The sequence of laboratory experiments, using a conidial strain rather than an ascosporic strain ofAspergillus nidulans, requires a minimum of time and materials, and can be completed successfully within a 14-week period.

ISSN:0008-4026    

DOI:10.1139/b62-125

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

The method describes an inexpensive modification of the Beckman DU spectrophotometer which permits rapid recording of the spectral energy distribution reflected from a magnesium carbonate surface. Comparison with a standard tungsten source corrects the effects of selective reflectivity and phototube response to different wavelengths. The method should be useful to biologists interested in the effects of light on organisms.

ISSN:0008-4026    

DOI:10.1139/b62-126

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

The occurrence and distribution of wetwood in balsam fir (Abies balsamea(L.) Mill. was investigated from the standpoint of determining the factors affecting its formation. Young, rapidly growing trees, namely those with wide annual rings, were found to be most subject to wetwood. This has been attributed to an incomplete branch healing, which promotes the direct entry of rainwater to the stem. Branch healing associated with narrow annual rings was such that it prevented water penetration. Wetwood in balsam fir was concentrated in the mid-stem region, becoming progressively less prevalent in the branchless lower bole and towards the living crown. The internal distribution of wetwood is explained by the prevalence of branch stubs in the region of the mid-stem and the capacity of such branches to trap and conduct water to the interior.

ISSN:0008-4026    

DOI:10.1139/b62-127

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

The vitamin requirements of an unidentified basidiomycete, the cause of severe snow mold of grasses and legumes in Western Canada, have been determined in shake culture. In a medium composed ofD-glucose,L-asparagine, and mineral salts, a mixture of several vitamins supported optimum growth, but an absolute requirement was demonstrated only for thiamine. Pyridoxine stimulated growth in the presence of thiamine. The optimum concentration of thiamine was 50 μg per liter and below this level growth was proportional to concentration. Pyridoxine was effective in the range 50–100 μg per liter in the presence of 50 μg per liter of thiamine. The requirement for thiamine could be satisfied by a mixture of equivalent amounts of thiazole and pyrimidine but not by either alone.

ISSN:0008-4026    

DOI:10.1139/b62-128

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Guard cell measurements indicative of stomatal size were made on a number of herbarium specimens of cockscomb (C. cristataL.,C. argenteavar.cristata(L.) Ktze.,et alii) and quail grass (C. argenteaL.) in order to clarify further their taxonomic relationships. Cockscomb is considered by some authors to be synonymous withC. argenteaL.; however, guard cell measurements averaged 9.59 and 11.70 units respectively, furnishing evidence for the distinctness of these two taxa. Consequently, cockscomb has been reinstated asC.CRISTATAL. In addition, five specimens were observed which possessed morphological characteristics of bothC. cristataandC. argenteabut were separable from both of these taxa by their guard cell measurements, which averaged 16.10 units. These plants collected in the Philippines and Central America are considered to have originated through hemialloploidy since the range of their guard cell measurements overlapped those of a known panalloploid between these species, namely,C. whiteiiGrant. The geographic distribution of these plants indicates that hemialloploidy has occurred with a high frequency in the genus. A spontaneous fasciated plant has also been described which arose from seed ofC. whiteii. Normal bivalent pairing of the chromosomes was observed in meiosis (n = 54) and progeny from this plant for three generations have all been fasciated.

ISSN:0008-4026    

DOI:10.1139/b62-129

出版商:NRC Research Press    

年代:1962

数据来源: NRC