Novel physiological properties of two cytokinin antagonists

The promotive effect of two cytokinin antagonists 2-chloro-4-cyclobutyl-ami no-6-ethylamino-1,3,5-triazine and N-(4-pyridyl)-O-(4-chlorophenyl) carbama te on somatic embryos production directly or through callus in leaf explant s of the grass Dactylis glomerata L. (orchardgrass) was established. The da ta for the endogenous contents of hydrogen peroxide and lipid peroxidation products during the earliest stages of somatic embryogenesis suggest that a nticytokinins induce some alterations in the production of active oxygen sp ecies. Both compounds activated the defence enzymes 5 days after culture in itiation. The triazine derivative enhanced catalase activity in more differ entiated leaf segments while the phenylurea-type anticytokinin had the same effect on peroxidase activity. Additional activation of catalase and sligh t reduction of peroxidase activity were determined in 10-day-old cultures. During induction of somatic embryogenesis in Dactylis leaf explants the mai n difference in the physiological action of the cytokinin antagonists teste d was related to IAA-oxidase activity. A possible role of the anticytokinin -induced changes in cell oxidative status on the explant embryogenic respon se is discussed.