OXIDATIVE STRESS OF CROPS MONITORED BY EPR

Treatment of leaves of spinach, corn, and peas with the herbicides paraquat, amitrole or acifluorfen leads to oxidative stress resulting in a light driven drastically increased production of ascorbic acid radical (monodehydroascorbic acid, MDAA) which could be demonstrated by in vivo EPR analysis. A discrimination of the MDAA formation between the action of electron uncouplers and catalase inhibitors can be achieved by observation of the radical rise kinetics. Significant MDAA signal intensities are detected in the darkness likewise. These signals are probably due to the action of ascorbic acid oxidase activated by membrane destruction.