IMPACT OF AMINOTRIAZOLE AND PARAQUAT ON THE OXIDATIVE DEFENSE SYSTEM OF SPRUCE MONITORED BY MONODEHYDROASCORBIC ACID - A TEST ASSAY FOR OXIDATIVE STRESS CAUSING AGENTS IN FOREST DECLINE

Treatment of young spruces with the herbicides aminotriazole and paraquat leads to oxidative stress resulting in a drastically increased production of ascorbic acid radical (monodehydroascorbic acid, MDAA) which could be demonstrated by in vivo EPR-analysis. While paraquat action is accompanied by a rapid decrease in reduced ascorbic acid content, no change in ascorbic acid content was observed by aminotriazole treatment. Thus MDAA-measurements can undoubtedly verify an existing oxidative stress of different origin in spruce needles. A decision between both radical generating mechanisms based on the radical kinetics is possible.