Subdoses de sulfosate sobre a inibição da atividade da EPSPS em plantas de milho

Abstract

To evaluate the effect of herbicide sub-lethal rates of sulfosate on absorption, EPSP synthase activity, and visual symptoms of corn plants (Zea mays), two greenhouse experiments were established at EMBRAPA (Brazilian Agricultural and Livestock Research Institute), in Sete Lagoas-MG, Brazil, in 2001. In one experiment, 10% of the recommended field rate (1.44 g ha-1) was tested to determine herbicide absorption time by corn plants and in the second experiment 0, 2, 4, 6, 8, 10, 12, 14 and 16% of the recommended rate were tested to study EPSPs activity and visual symptoms of phytotoxicity on corn plants. Corn plants absorbed 25.2% of sulfosate 24 hours after application and absorption increased to 65.4% at 96 hours. The higher the sulfosate rate, the higher was the EPSPs activity inhibition, 24 hours of application, and more evident the phytotoxicity symptoms on corn plants. At 16% of the recommended rate, this inhibition reached 72.6%.