摘要:

In general, the virulence ofRhizoctonia SolaniKühn, shown on potato stems, decreased as the proportion of inoculum, which was grown in steam sterilized soil, increased. Isolates highly pathogenic in a 1:15 soil inoculum—natural soil mixture were relatively weak in pure soil inoculum protected from outside contamination.Sclerotia developed and mycelia massed much more frequently and abundantly in the higher concentrations of soil inoculum than in the 1:15 soil-inoculum–natural-soil mixture. Thus, the evidence indicates that conditions favourable to marked vegetative growth of the pathogen tend to depress its virulence. The evidence available suggests that the new and vigorous hyphal growth necessary to sclerotia formation is initiated primarily by high relative humidity of the soil air.Further evidence was obtained that isolates ofR.Solanipathogenic to potato may differ greatly in virulence and also in ability to form sclerotia, and also that theCorticiumstage is an important source of pathogenic and sclerotia-bearing strains of this fungus. Finally, soil-grown inoculum 180 days old was as virulent as that freshly grown.

ISSN:1923-4287    

DOI:10.1139/cjr41c-001

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

Deplasmolysis injury, ductility of cytoplasmic strands, and the shape assumed by injected oil drops on deplasmolysis were investigated. The surface membrane of the protoplast of non-hardy cells stiffened when dehydrated osmotically. As a result, it ruptured readily when subjected to tension. The stiffening either failed to occur in hardy cells, or it arose only as a result of a much greater dehydration (depending on the degree of hardiness). The refractive index of the protoplasmic surface increased more on dehydration in the case of non-hardy than of hardy cells. Plasmolysis, if maintained for some time, induced a clumping of plastids and granules (systrophy) in non-hardy but not in hardy cells. All these facts indicate a greater hydrophily in hardy than in non-hardy cells—both of the surface membrane of the protoplasm and, as shown in Part I, of the protoplasm as a whole, although it is probably less marked in the latter.

ISSN:1923-4287    

DOI:10.1139/cjr41c-002

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

DormantTaxus cuspidatacuttings were treated with talc dusts containing 1- and 2-γ-naphthylbutyric acid at concentrations of 0, 500, 1000, and 2000 p.p.m., each taken separately and in combination with 0, 0.1, 1, and 10% of a mixture of nutrient salts and 0 and 50 p.p.m. of ethyl mercuric bromide. Data on the number of rooted cuttings failed to disclose any significant treatment effects. However, the number and length of roots per rooted cutting were increased by the phytohormone in all concentrations, the effect increasing with ascending concentration. Data for most of the other criteria indicated injurious effects from the phytohormone. The average length of new growth was increased by both the 1 and 10% concentrations of nutrient salt in the presence, but not in the absence, of 1000 p.p.m. of the phytohormone. The 10% concentration of nutrient salts decreased the number of cuttings with new growth and the number of such cuttings that were rooted. Organic mercury treatment failed to have any significant effects.

ISSN:1923-4287    

DOI:10.1139/cjr41c-003

出版商:NRC Research Press    

年代:1941

数据来源: NRC