| Abstrakt: |
The effects of γ-radiation on the permeability of carrot tissue were studied by means of various methods. The loss of sugar and ions to water and the uptake of sucrose in 1 M sucrose were shown lo increase strongly with increasing doses. The weight loss in 1 M sucrose plus the weight loss in water as compared to untreated samples were reduced considerably with increasing doses of radiation. In the presence of 0.01 M CaCl2 the uptake of sucrose was considerably lower and the weight loss was considerably higher in 1 M sucrose, but the overall course of the curves was the same as in the absence of CaCl2. All of these gains and losses of matter proceeded exponentially with increasing doses. The weight loss in I M sucrose was accompanied at low doses by shrinking and plasmolysis of the cells. At higher doses there was no such reaction. In addition it was shown that the rates of uptake and release of matter were dependent on temperature and on the ratio: area of cut surface/volume, while the final result was independent of these values. The extent of exudation through the periderm was very slight at low doses. It was also shown that Ca induced rigidity of the cell walls and reduced the permeability of cells lo sucrose. Na had a reverse effect. Low pH values (c 2) caused a direct loss of matter from the cells to water. It was not possible to demonstrate any certain effect of oxalate ions (0.01 M) on the uptake of water. Freezing of the tissue gave the same curves as the highest dose of radiation used, but the effect on its structure were different. Fixing fluids appeared to have the reverse effect of irradiation on permeability. Respiration experiments showed the respiration intensity to decrease simultaneously with the strong increase in permeability. On the basis of present results it appears to be reasonable to assume that a combination of the radiation induced injuries to the tissues (impairment of the wound healing mechanism, deterioration of wall material and increased permeability) was sufficient to provide the saprophytes with the same growth possibilities which the parasites obtain independently on untreated material, and that treatment with low concentrations of CaCl2 might reduce the effects. [ABSTRACT FROM AUTHOR] |
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