摘要:

Cell permeability as estimated by the plasmolytic method in various types of plants and for different classes of solute has been studied in relation to frost resistance and the seasonal cycle. Permeability is found to increase greatly with hardening, whether induced by low temperature or other conditions, and it seems to parallel closely the seasonal changes in frost resistance. As regards different species and varieties, cell permeability in the hardened state shows better correlation than any other character with ability to resist frost. The permeability change is greatest towards potassium nitrate—at least in cells (viz., those of hardy woody plants) that are definitely permeable to the salt; the change is more moderate towards polar non-electrolytes with small molecules, such as urea, but with these it occurs in all plants capable of hardening; towards apolar substances, such as urethane, there is no change. These relations point to a widening of the aqueous pores or increased hydration of the plasma membrane as the mechanism of the permeability increase. Hypotheses are put forward as to the means by which freer permeability to water may increase resistance to certain types of mechanical injury by frost.

ISSN:1923-4287    

DOI:10.1139/cjr36c-023

出版商:NRC Research Press    

年代:1936

数据来源: NRC

摘要:

The investigations reported here are concerned with isolations from diseased raspberry roots, preliminary inoculations with isolates, and microscopic examination of naturally and artificially infected roots.The following fungi were isolated from naturally infected roots:Coniothyrium Fuckelii,Cylindrocarpon radicicola,Fusariumsp., possiblyF.orthoceras,Cylindrocladiumsp.,Pythiumspp.,Rhizoctonia Solani,Rhizoctoniasp. (orchid type), and in preliminary inoculation experiments each fungus was found to be capable of producing necrotic lesions on healthy roots. Microscopic examinations of roots artificially inoculated with pure cultures of the above fungi, showed in the roots the presence of the fungus used for inoculation. In addition the "phycomycetous mycorrhizal" fungus already associated with root rot of strawberries and tobacco was observed to be almost always present in roots of affected raspberry plants, and, to a lesser extent, in apparently healthy roots from apparently normal plants. Nematodes, especiallyAnguillulina pratensis, the meadow nematode, were present in and on roots from certain soils, while they were absent from roots from other soils. Strawberry and raspberry seeds were sown in sterilized and non-sterilized affected soil with the result that the roots in sterilized soil appeared to be healthy, while those in the non-sterilized soil became affected with necrotic lesions.Evidence is given which shows not only that certain symptoms of raspberry root rot are similar to the symptoms of strawberry root rot, which is considered to be a major factor in the degeneration of strawberries in both Europe and America, but also that many of the fungi and nematodes generally conceded to be associated with root rots of strawberry are likewise associated with root rots of raspberry. In the Fraser Valley, British Columbia, where certain raspberry plantations appear to be heavily infected with root rots, the possibility that these root rots may play an important role in connection with the un-thriftiness of such plantations should not be overlooked.

ISSN:1923-4287    

DOI:10.1139/cjr36c-024

出版商:NRC Research Press    

年代:1936

数据来源: NRC