Antagonistic Interaction of EPTC and 2,4-D

An antagonistic interaction betweenS-ethyl dipropylthiocarbamate (EPTC) and (2,4-dichlorophenoxy)acetic acid (2,4-D) was observed on sorghum(Sorghum vulgarePers.) and corn(Zea maysL.) after 21 days growth in soil incorporated treatments. Increasing the 2,4-D concentration increased the antagonism to EPTC. The antagonistic interaction was alsoobserved onsorghum grown in solution culture. The antagonistic interaction occurred when the site of uptake was restricted to either the root or shoot zone of sorghum. Uptake studies with14C-EPTC indicated that 2,4-D does not interfere with uptake or subsequent movement of14C radioactivity within sorghum plants. Respiration of sorghum treated with the combination EPTC-2,4-D appeared to be normal. Respiration of EPTC-treated plants was inhibited.