Enhanced Degradation of Atrazine by Corn (Zea mays)

Photosynthesis in corn (Zea maysL. ‘Pioneer 3369A’) was inhibited 25% by atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] after a 2-h root exposure in nutrient solution. Photosynthesis of the treated plants had completely recovered 21.4 h after removal from the treatment solution. Recovery of photosynthesis from second and third successive atrazine treatments required only 10.3 h and 4.0 h, respectively. Atrazine metabolism rates in corn plants after 1, 2, or 3 successive 4-h treatment periods, where each treatment period was followed by a 12-h recovery period, showed increased rates of metabolism of atrazine during each recovery time. An increased level of glutathione-S-atrazine was found following the first 4-h atrazine treatment and 12-h recovery. The enhanced production of GS-atrazine was maintained throughout subsequent exposures and recoveries. An inverse correlation (r2= 0.992) was found between the increase in GS-atrazine production following each 4-h atrazine exposure and the time required for corn plants to recover from atrazine-induced photosynthesis inhibition. Enhanced detoxification of atrazine by corn plants pretreated with atrazine was indicated. No enhanced tolerance to other herbicides was observed from atrazine pretreatment. This phenomenon is similar to that described for the enhanced detoxification of several insecticides in animal systems.