Species Differences in Site of Shoot Uptake and Tolerance to EPTC

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Abstract
We determined the effects of ethylN,N-dipropylthiocarbamate (EPTC) in soil placed at different shoot zones of barley (Hordeum vulgareL.), wheat (Triticum aestivumL.), oats (Avena sativaL.), and sorghum (Sorghum vulgarePers.) below the soil surface after emergence. A wax-barrier allowed separate exposure of the shoot zones to treated soil. Wheat, barley, and oats were severely injured when treated at the coleoptilar internode. Exposure of the remaining shoot did not affect growth. Sorghum was severely injured regardless of the shoot zone exposed. On this basis, sorghum was the most susceptible, while wheat, barley, and oats were equally tolerant. Uptake of14C-EPTC from the soil by the sorghum shoots was double that of wheat, a fact which might explain the differential susceptibilities. These studies indicate that growth responses of species to EPTC applied to shoots is dependent on the stage of plant development at which treatment occurs.