Novel Physiological Properties of Two Cytokinin Antagonists

The promotive effect of two cytokinin antagonists 2-chloro-4-cyclobutyl-amino-6-ethylamino-1,3,5-triazine and N-(4-pyridyl)-O-(4-chlorophenyl) carbamate on somatic embryos production directly or through callus in leaf explants of the grass Dactylis glomerata L. (orchardgrass) was established. The data for the endogenous contents of hydrogen peroxide and lipid peroxidation products during the earliest stages of somatic embryogenesis suggest that anticytokinins induce some alterations in the production of active oxygen species. Both compounds activated the defence enzymes 5 days after culture initiation. The triazine derivative enhanced catalase activity in more differentiated leaf segments while the phenyl ureatype anticytokinin had the same effect on peroxidase activity. Additional activation of catalase and slight reduction of peroxidase activity were determined in 10-day-old cultures. During induction of somatic embryogenesis in Dactylis leaf explants the main difference in the physiological action of the cytokinin antagonists tested was related to IAA-oxidase activity. A possible role of the anti cytokinin-induced changes in cell oxidative status on the explant embryogenic response is discussed.