Mode of Action of Atrazine and Simazine in Susceptible and Resistant Lines of Corn

Two lines of corn (Zea mays L.)—one, GT112 RfRf, resistant to 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), and the other, GT112, susceptible to both—were used. Both glucose and sucrose, supplied to the treated plant through a severed leaf tip, were found to protect GT112 from the toxic effect of atrazine and simazine. Glucose gave a slightly better protection. Oxygen uptake in excised roots of GT112 treated with atrazine gradually declined with age until death, while leaf discs of treated and untreated lines showed no distinct trend in oxygen uptake. Atrazine decreased root respiration in GT112 but had no effect on that of GT112 RfRf. Root respiration in untreated GT112 was higher than in untreated GT112 RfRf. Atrazine decreased leaf respiration when both lines were considered.