Effect of Purine and Phenylurea Cytokinins on Peroxidase Activity in Relation to Apical Dominance of in Vitro Cultivated Rosa Hybrida L

The formation of active oxygen species affects the morphogenesis of plant cells and tissues and inhibits the process of development during in vitro cultivation. Cytokinins have been found to be effective free radical scavengers. Peroxidase (EC 1.11.1.7) is among enzymes expressing antioxidative functions. The present study was focused on the effect of N6-benzyladenine (BA), and N1-(2-chloro-4-pyridyl)-N2-phenylurea (4PU-30) on guaiacol-peroxidase activity regarding the break and growth of axilary buds in rose (Rosa hybrida L.) in vitro. The activity of peroxidase was determined by the method of Hart et al. (1971). Three concentrations of cytokinins (1.0 μM; 1.6 μM; 2.2 μM) were tested. An increase of peroxidase activity was established on day 1 after the transfer of single nodes on the media that was probably caused by a mechanical stress in the process of explant isolation or was contributed to the composition of nutrient media. When the explants were cultured on media with 1.0 μM BA a stimulation of enzyme activity was found later than in variants with 1.6 and 2.2 μM BA. The applied lower concentration of 4PU30 (1.0 μM) caused opening of more axilary buds and obvious enhancement of peroxidase activity in comparison to the highest concentration of BA. These results supported the view that phenylurea cytokinins could be more active than purine cytokinins. Acceleration of peroxidase activity was associated with increased number of open axilary buds. Since the activity of peroxidase in our experiments was stimulated in response to cytokinin application we suppose that cytokinins might make this enzyme active thus control-