| Abstrakt: |
Abstract: In pumpkin plants suffering from calcium deficiency growth of the root system is characteristically suppressed. A biochemical symptom of calcium deficiency is a decrease or even complete disappearance of activity of one of the isoperoxidases (isoperoxidase D). In the present study the two characteristics were used to compare the effects of calcium deficiency and of IAA in the supraoptimal concentration of 10-5 M. Peroxidases were separated by centrifugal fractionation: peroxidases A and B were found in the sediment corresponding to the mitochondrial fraction, peroxidase D in the supernatant. It was not possible, however, to obtain the sediment completely free of peroxidase D. A negative correlation between the activity of isoperoxidase D and the logarithm of concentration of IAA in nutritive solution was found and similarities in the effects of IAA in supraoptimal concentration and of calcium deficiency on the development of root system were demonstrated. Still, it would be difficult to imagine that the mechanism of the action of the two factors is the same. For this reason, a scheme of possible interactions was suggested with the aim to explain how similar changes in the content of isoperoxidases are brought about by the two factors. In this scheme, calcium is considered chiefly as a substance regulating membrane permeability. |
