Species Differences in Site of Root Uptake and Tolerance to EPTC

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Abstract
We studied the uptake of ethyl N,N-dipropylthiocarbamate (EPTC) by barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oats (Avena sativa L.), sorghum (Sorghum vulgare Pers.), and giant foxtail (Setaria faberii Herrm.) using a double plastic pot technique that allowed separate exposure of the shoot and root zones to treated soil. Barley was more tolerant than wheat, whereas oats, sorghum, and giant foxtail were the most susceptible to EPTC at 1/4 to 1 1/2 lb/A-inch. The roots were the major site of uptake in barley, but injury to the other species from root exposure was equal to or slightly less than that from shoot exposure. The seed, or first 2 to 4 mm of shoot or both, were more sensitive in wheat than in barley. Such differential sensitivity was not evident in the shoot zone of the other species. These experiments, coupled with 14C-EPTC studies, indicated that differences in tolerance can be associated with the sites of uptake.