A Microradioautographic Study of14C-Trifluralin Absorption

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Abstract
The technique of microradioautography was used to study the absorption and translocation ofa,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) by cotton (Gossypium hirsutumL., var. Coker 201) and soybean (Glycine max(L.) Merr., var. Lee). Radioactivity from14C-trifluralin was retained primarily on the surfaces of the roots of cotton and soybean. This was apparently due to a tenacious adsorption or binding of the radioactivity to the epidermis and cuticle. Entrance of radioactivity into the roots of these species was greatly facilitated by breaks in the epidermis, such as might occur from seedling diseases or mechanical damage. Within the roots, radioactivity was noted in the walls of the xylem vessels and cortical cells. Little movement out of the soybean roots was observed, but limited movement of radioactivity into the leaves of cotton, apparently via the metaxylem, was noted. Radioactivity accumulated in the protoxylem of the cotton stem where many elements appeared to be plugged. Results of this study indicate that care should be used in interpreting data from studies where loss of radioactivity from nutrient media is used as a criterion of herbicide absorption, and where gross radio autography is used as an indicator of herbicide translocation.