摘要:

Five radiation sources were used to induce mutations in barley. All treatments were given at a dosage of 10,000 r. equivalent. The radiation sources with their respective dose-rates in the region of the irradiated seeds were: a betatron (181.8 r./min.), an X-ray machine (201 r./min.), radium-beryllium (5.3 r./min.), and two Co60sources (4.5 r./min. and 75.75 r./min.). None of the radiation sources used was more effective than the X-ray treatment in producing mutations. The betatron and the high dose-rate treatments from Co60appear to be somewhat less effective than X-rays. Over 30 different mutant types were produced, including a number of vital mutants, such as stiff-strawed and early-maturing types. These appear promising as new varieties, but require further agronomic evaluation. It is concluded that mutation induction will become a useful new approach for plant breeders.

ISSN:0008-4026    

DOI:10.1139/b55-041

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

A previously unreported foot rot disease of wallflower,Cheiranthus cheiri, caused by the fungusPhytophthora megasperma, was found in Saanichton, B.C., in 1953. The optimum temperature for growth of the fungus is 20° to 25 °C, the maximum approximately 31 °C, and the minimum below 5 °C. Sporangia develop at all temperatures between 5° and 20 °C, but the optimum temperature for their development is approximately 14 °C, whereas the optimum temperature for the development of organs of fusion is approximately 20 °C. The fungus proved to be pathogenic to wallflower plants only under wet soil conditions, hence it is considered that good soil drainage is an important factor in the control of the disease.

ISSN:0008-4026    

DOI:10.1139/b55-042

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Thirty-one strains of crested wheatgrass from European and North American sources were assigned to six morphological forms. These forms showed affinities to the speciesAgropyron cristatum(L.) Gaertn.,A.desertorum(Fisch.) Roem. & Schult.,A.sibiricum(Willd.) P.B.,A.fragils(Roth.) Nevski,A.michnoiRoshev., andA.imbricatum(M.B.) Roem. & Schult. Typical plants, spikes, glumes, and seeds of the six forms were illustrated. Eight strains ofA.cristatumwere diploid (2n = 14) and two strains were tetraploid (2n = 28). Strains of all other forms were tetraploid. Chromosome counts of root tips indicated no aneuploids in 71 diploid plants and one aneuploid (2n = 29) in 96 tetraploid plants. Meiotic observations, however, indicated accessory chromosomes in 14 of 43 tetraploid plants. Diploid forms ofA.cristatumcrossed sparingly with tetraploid species to form sterile hybrids. All tetraploid species were interfertile and formed fertile hybrids. Most desirable strains agronomically were of the speciesA.cristatum,A.desertorum, andA.imbricatum. Most vigorous hybrids were sterile plants from crosses ofA.desertorumandA.cristatum.

ISSN:0008-4026    

DOI:10.1139/b55-043

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

The winter resting stages of 17 species of Ericaceae are described, figured, and analyzed. From this analysis, the following deductions were made: (1) Each species has a fairly definite winter resting stage. (2) As rates of development vary from species to species, the winter resting stage is not in all cases related to the time of full bloom. (3) The embryo sac and anther do not develop at similar rates; hence, for any stage in the development of one, there is not a definite accompanying stage in the development of the other. (4) The Ericaceae were not evolved in a climate which had the marked periodicity and extreme cold characteristic of our present north temperate zone.

ISSN:0008-4026    

DOI:10.1139/b55-044

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Cochliobolus sativus(Ito&Kurib. ex Kurib.) Drechs. ex Dast. produced mature ascocarps on seeds ofZea maysL., previously disinfested with mercuric chloride, boiled one minute to kill the embryo and partly immersed in Sach's agar. Isolates of the conidial state,Helminthosporium sorokinianumSacc. ex Sorokin (=H.sativumPamm., King & Bakke), and monoascosporic isolates were hermaphroditic and heterothallic. Uninucleate, spherical spermatia 1.7 μ wide, the sole male agents in plasmogamy, were produced in phialids in slimefilled spermogonia measuring 2.5 × 2.5 mm. Hyphal fusions and conidiation did not initiate the heterokaryon in the ascogonium. Homokaryotic isolates and incompatible crosses produced partially mature ascocarps by differentiation of maternal stroma. Pseudoparaphyses extended downwards from subapical stromatic cells and produced locules. Subsequently in compatible crosses the heterokaryotic ascogenous hyphae grew from the sub-basal pseudoparenchyma and produced a fascicle of asci in the locule. Eight scolecospores, uninucleate at inception, formed after meiosis. The asci had two walls (bitunicate) but the inner wall was not evident in asci filled with spores nor functional in spore discharge. Whole asci extruded from the ascocarp in slime and dehisced in water by a terminal circumscissile rupture.CochliobolusDrechs. was placed in the Pseudosphaeriaceae Höhn. sensu Luttrell in the Pseudosphaeriales Thiessen & Sydow.

ISSN:0008-4026    

DOI:10.1139/b55-045

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

The controversial nomenclatural problem concerning the fungi causing the ink spot disease of poplar is discussed in detail. It is concluded that the correct name of the eastern species isCiborinia whetzelii(Seaver) Seaver and that the western species does not possess a legitimate name.Ciborinia seaverinom. nov. is proposed for this fungus. Two other species ofCiboriniaonPopulusare described from specimens and manuscript notes of the late Professor H. H. Whetzel,C.pseudobifronsWhet. sp. nov. andC.davidsonianaWhet. sp. nov.

ISSN:0008-4026    

DOI:10.1139/b55-046

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Sclerotinia borealisBubak & Vleugel, previously known only from Sweden, Norway, Finland, and the U.S.S.R., has been found causing injury to cultivated grasses at Prince George, B.C. Apothecia have been developed in culture and compared with authentic material from Sweden. The fungus is homothallic and self-fertile.

ISSN:0008-4026    

DOI:10.1139/b55-047

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Cylindrosporiumsp., isolated from dead yellow birch roots, inhibited the growth of another fungus isolated from mycorrhiza and dead roots. Growth rate of the former increased while that of the latter decreased with increased temperature above the optimum for rootlet, development. Twenty-four species of fungi were isolated from mycorrhiza. Seedlings grown aseptically in soil and in agar were inoculated with fungi isolated from dead and dying rootlets and from mycorrhiza, but none of the organisms displayed sufficient virulence to cause birch dieback. The optimum temperature for development of potted seedlings was about 18.5 °C. Increases or decreases of 2 °C. or more from the optimum for yellow birch development resulted in increased rootlet mortality, decreased frequency of mycorrhiza, and a thinner mantle of hyphae in mycorrhiza, followed by reduction in foliage vigor. Normal rootlet mortality of 6% in a 55-year-old yellow birch stand was increased to 19 and 60% by raising soil temperature 1° and 2 °C, respectively, above the normal during one summer. Soil moisture was not lowered a statistically significant amount by a 5 °C. increase until the sixth day following rain. Mycorrhiza existed on residual living roots in about the same proportion as on undisturbed root systems. The possibility that birch dieback may be the result of soil temperature increases is discussed. It is suggested that cutting practices in hardwood stands should remove all yellow birch trees or prevent increased temperatures in soil occupied by residual birch.

ISSN:0008-4026    

DOI:10.1139/b55-048

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Treatment with the growth substance indoleacetic acid was used to stimulate mitosis in differentiated tissues ofAllium ceparoots in order to establish whether nuclear differences, specifically in chromosome number, exist normally and are merely revealed by treatments, or whether these nuclear differences are produced by the treatment. With the concentrations of indoleacetic acid and durations of treatment used, evidence was obtained that: chromosome number differences exist in the differentiated tissues of onion root prior to any treatment and that the appearance of these differences after treatment is a matter of revelation and not of causation. The evidence obtained in these investigations comes indirectly from observations of nuclear size and structure and directly from rare spontaneous mitoses in untreated roots, and in the treated roots (i) from the absence of nuclear abnormalities which might explain otherwise the origin of polyploid cells, (ii) from the uniform occurrence of certain chromosome numbers in specific root tissues, (iii) from proportions of diploid and polyploid divisions during mitotic induction, and (iv) from the lack of relationship between total mitotic activity and number of polyploid mitoses. A gradient of endomitotic polyploidization exits in certain tissues along the longitudinal axis of the onion root.

ISSN:0008-4026    

DOI:10.1139/b55-049

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Data collected in this very uniform bog community lend themselves particularly well to an assessment of phytosociological criteria. Expressions of frequency, constancy, fidelity, homogeneity as proposed by various writers are tested and evaluated. At the same time, it is believed that the present paper provides an accurate description and definition of the phytosociological unit with which it is concerned.

ISSN:0008-4026    

DOI:10.1139/b55-050

出版商:NRC Research Press    

年代:1955

数据来源: NRC