摘要:

Histological studies of controlled beetle and artificially infected American elm trees (Ulmus americanaL.) show that the pathogen of the Dutch elm disease,Ceratocyslis ulmi(Buism.) C. Moreau, grows extensively in all tissues of the xylem. The pathogen produces numerous small spores and hyphae, which pass from cell to cell by means of pits and direct penetration of the walls. This explains the rapid spread of the fungus in the host. Disintegration of bordered pits and of cell walls occurs as infection develops. Acute symptoms of the disease are attributed primarily to complete plugging of the vessels of small branches by the fungus and disintegration products. Gradual or partial plugging of vessels of stems and larger branches and disintegration of cell walls per se are postulated as contributing to the chronic symptoms of the disease. Crossing of the fungus from one growth ring to the next in branches is described.Host reactions to the fungus and seasonal changes in nutrients are discussed in relation to resistance. In beetle-inoculated trees, it was found that wounds extending from the crotch down the sides of the branch were the most favorable for the establishment of infection.

ISSN:0008-4026    

DOI:10.1139/b62-153

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Irradiation under either daylight fluorescent lamps or diffuse sunlight stimulated pycnidial development in 40 isolates ofAscochyta pisi. Sporulation varied among these same isolates when grown in darkness, and ranged from none to profuse. Irradiation of selected isolates through filters showed the importance of ultraviolet radiation in stimulating reproduction. The precise relationship of quality, intensity, and length of exposure of radiation to induction of sporulation was studied with monochromatic radiation at 21 °C. Treatment of colonies with monochromatic radiation of wavelengths 2378 Å to 5461 Å (band width 132 Å) at the same intensity of 100 μw/cm2and with exposures ranging from 1/50 to 20,000 seconds proved conclusively that only ultraviolet radiation induced sporulation. Two wavelengths, 2378 Å and 3131 Å, were notably effective in inducing pycnidial formation over a wide range of exposures. The dosage effective in inducing sporulation decreased with decrease in wavelength. Similarly, the minimum dosage which caused inhibition of sporulation was also least at the shorter wavelengths. Onset and abundance of sporulation differed significantly when the intensity of radiation was varied. The higher the intensity, the shorter was the exposure necessary to stimulate sporulation, or cause inhibition of sporulation. Pycnidia were stimulated by near ultraviolet radiation over a wide range of temperatures (10° to 30 °C), over a wide range of pH values (4.5 to 8.3), and on four commonly used media. Growth (dry weight) under continuous exposure to near ultraviolet radiation did not differ from growth in darkness.The region of mycelium most sensitive to effects of radiation on sporulation at 21 °C was a peripheral zone of young mycelium approximately 1.5 to 2 mm in width. In colonies incubated at a constant temperature of 21 °C, the older mycelium was practically insensitive to radiation. A photoactivated sporulation precursor was able to move small distances from the irradiated peripheral mycelium to newly formed non-irradiated mycelium. Movement of the percursor appeared to be by translocation within hyphae rather than by diffusion through the medium.The location of pycnidia relative to the surface of the medium was dependent on length of exposure and quality and intensity of radiation; absorption of radiation by medium; incubation temperature; and age of mycelium.The size of pycnidia, and the size and shape of conidia both in culture and on the epicotyls ofVicia villosa, were significantly influenced by the dosage and quality of radiation.

ISSN:0008-4026    

DOI:10.1139/b62-154

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

One hundred and four nutritional, morphological, and acriflavine-resistant mutants were produced in a strain ofPenicillium expansumisolated from an infected apple. Nutritional mutants were induced more readily with ultraviolet than with gamma radiation. Heterocaryons were established between strains involving up to eight pairs of markers. Heterozygous diploids were recovered with comparative ease following treatment of the heterocaryons with D-camphor but with great difficulty in untreated heterocaryons. Screening of more than 500 million conidia from three untreated heterocaryons failed to yield a diploid. Analysis of 110 independent segregants from the heterozygous diploid M53/M67 has resolved seven genes into two linkage groups, viz. I:w3bi1pyr1br3, and II:nic2ri1acr1.

ISSN:0008-4026    

DOI:10.1139/b62-155

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Experiments were conducted to determine the relationship between clover phyllody and strawberry green petal diseases in Eastern Canada. Clover phyllody virus from naturally infected ladino clover (Trifolium repensL.) in Quebec was transmitted byAphrodes bicinctus(Schrank) to strawberry (var. Redcoat and Sparkle) and ladino clover. Symptoms on infected strawberry were typical of green petal. Strawberry plants, naturally infected with green petal, were obtained from Kentville, N.S., La Pocatière, Que., and Charlottetown, P.E.I. The virus was transmitted to ladino clover, red clover (Trifolium pratenseL.), and strawberry (vars. Redcoat, Guardsman, Senator Dunlap, and Grenadier) byA. bicinctusand to ladino clover and aster (Callistephus chinensisNees) byMacrosteles fascifrons(Stal).On the basis of leafhopper transmission and symptomatology, it is concluded that clover phyllody and strawberry green petal diseases in Eastern Canada are caused by the same virus.

ISSN:0008-4026    

DOI:10.1139/b62-156

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

The effect of light quality on the products of photosynthesis has been studied in two species of green algae,Chlorella pyrenoidosaandScenedesmus acuminatus, the blue-green algaMicrocystis aeruginosa, and the photosynthetic bacteriumChromatiumsp.The test organism was placed in C14-bicarbonate and illuminated at saturation intensities of red, red plus supplementary blue, blue alone, or white light. After 30 minutes, the distribution of C14among the products of photosynthesis was determined using the techniques of paper chromatography and autoradiography.At a high concentration of cells ofChlorella pyrenoidosa, blue light caused an increase in C14in aspartic, glutamic, fumaric, and malic acids and a decrease in sucrose and phosphate esters, although the rate of photosynthesis remained the same. At a low concentration of cells, similar changes were found, and these were accompanied by an increase in the rate of photosynthesis.Similar changes in the distribution of C14due to blue light were found also inScenedesmus. InMicrocystis, a substantial increase in C14due to blue light was found only in glutamic acid. The rate of photosynthesis remained the same in both organisms.The results indicate that the nature of the effect of blue light is the same in all of these organisms and inChlorella vulgariswhich was studied previously.Pretreatment in darkness is a prerequisite for a pronounced effect of blue light on the products as well as the rate of photosynthesis.No effect of light quality was found inChromatium.

ISSN:0008-4026    

DOI:10.1139/b62-157

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Stand-opening disease in Saskatchewan spruce forests is characterized by the occurrence of patches, often of an acre or more, of declining and dead trees.Polyporus tomentosusFr. is a major cause of the disease, which develops slowly, with 20 to 30 years elapsing between initiation of attack and death of the trees. Extensive root decay develops before the above-ground symptoms become apparent. Inoculation experiments have shown thatP. tomentosusgrows about 1.5 in. per year, and that the fungus is parasitic on white spruce.Polyporus tomentosusmay enter healthy roots at a point of contact with infected roots; no evidence was found that it entered through root tips or directly from the soil. The fungus remains viable in infected roots for at least 16 years. The disease is commonly associated with injury caused by root-tunnelling weevils in the genusHylobius. Host vigor did not appear to influence infection or disease development. In culture, the optimum temperature forP. tomentosuswas 20 °C and the optimum pH was 4.5. At lower temperaturesP. tomentosusappeared to have a competitive advantage over fungi isolated from dying rootlets. Small seedlings grown in agar withP. tomentosuswere killed in 8 months. Under these conditionsP. tomentosuswas much less virulent thanRhizoctonia, solaniKühn andPhytophthora cactorumL. and C. Schroet.

ISSN:0008-4026    

DOI:10.1139/b62-158

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Initiation of germination in excised embryos requires an exogenous energy source. Normally this is obtained from the endosperm. In dormant seeds the hydrolysis of starch is blocked despite the fact that dormant and non-dormant seeds contain similar amounts of α- and β-amylases. Alone or in combination the amylases are unable to break down raw endosperm starch granules to simple sugars in vitro. Exogenous maltase in combination with α-amylase hydrolyzes raw starch to glucose. Exogenous maltase eliminates the requirement for exogenous sugar. Examination of the maltase content of imbibed dormant and non-dormant seeds showed a marked increase in non-dormant seeds during the first 40 hours. This does not occur in dormant seeds unless they are treated with gibberellic acid. The results lead to the conclusion that an important effect of gibberellic acid is to induce the synthesis of maltase or in some way activate the preformed enzyme.

ISSN:0008-4026    

DOI:10.1139/b62-159

出版商:NRC Research Press    

年代:1962

数据来源: NRC

摘要:

Cytotaxonomic data are reported for the generaHordeum, Eremopyrum, Secale, Sitanion, andTritícum. New nomenclature is:Hordeum geniculatumAll. f.hirtellum(Degen ex Nevski) Bowden;Hordeum jubatumL. emend, subsp. ×intermediumBowden (subsp.breviaristatumBowden × subsp.jubatum);Hordeum jubatumL. emend, subsp.breviaristatumBowden;Hordeum leporinumLink var.simulansBowden; andEremopyrum bonaepartis(Spreng.) Nevskif. hirsutum(Bertol.) Bowden.Voucher specimens are cited for the following chromosome number determinations:(1) diploid, 2n = 14:Hordeum californicum, H. geniculatum, H. glaucum, H. marinum, H. pusillum, andEremopyrum bonaepartisf.bonaepartis.(2) tetraploid, 2n = 28:Hordeum depressum, H. geniculatum, H. jubatumsubsp.jubatum, H. jubatumsubsp. ×intermedium, H. jubatumsubsp.breviaristatum, H. leporinumvar.leporinum, H. murinum, Eremopyrum bonaepartisf.bonaepartis, E. bonaepartisf.hirsutum, andE. distans.(3) hexaploid, 2n = 42:Hordeum arizonicumandH. leporinumvar.simulans.

ISSN:0008-4026    

DOI:10.1139/b62-160

出版商:NRC Research Press    

年代:1962

数据来源: NRC

ISSN:0008-4026    

DOI:10.1139/b62-161

出版商:NRC Research Press    

年代:1962

数据来源: NRC

ISSN:0008-4026    

DOI:10.1139/b62-162

出版商:NRC Research Press    

年代:1962

数据来源: NRC