Shoot Zone Uptake and Translocation of Soil-Applied Herbicides

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Abstract
Diphenamid (N,N-dimethyl-2,2-diphenylacetamide) severely inhibited adventitious roots in the shoot zone of sorghum (Sorghum bicolor(L.) Moench., var. RS 610) and corn (Zea maysL., var. WF9 X B37) without decreasing foliage growth. Using diphenamid to inhibit shoot zone roots, the presence of adventitious roots was shown to increase foliage injury to corn, sorghum, or both when exposed to 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron), 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryne), or 3-tert-butyl-5-chloro-6-methyluracil (terbacil) in the shoot zone. Inhibition of adventitious roots was associated with a decrease in uptake of14C-diuron and14C-ametryne in both corn and sorghum. Inhibition of the adventitious roots did not alter the response of corn or sorghum, as measured by top growth, when treated with dimethyl tetrachloroterephthalate (DCPA), isopropyl-m-chlorocarbanilate (chlorpropham),S-ethyl dipropylthiocarbamate (EPTC), andα,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). The meristematic region of the sorghum shoot before emergence was more sensitive than other regions of the shoot to DCPA and chlorpropham. Injury from other application sites depended upon uptake from the treated area and movement to the meristematic region, where both herbicides appear to be acting.