Published online by Cambridge University Press: 12 June 2017
Dalapon–2–C14, applied as droplets, was employed in tracer studies by autoradiography and counting. That dalapon remained non-metabolized throughout the experiment was confirmed by chromatography. Surfactants greatly enhanced (cuticular) penetration. Small amounts of herbicide were sorbed almost instantaneously (15–30 seconds). Movement away from the treated area “showed” or “appeared as” first a diffusional pattern, but soon became channelized in veinlets and larger vascular bundles. Dalapon applied off the midvein did not enter the midvein in appreciable quantities during basipetal transport. Dalapon which entered the midrib originally remained highly concentrated in this channel. During transport, some dalapon was retained or retarded by tissues through which it passed. Retention was greatest in the basal sections (intercalary meristem regions) of young grass blades. A 10-fold build-up of dalapon was demonstrated following drop application off the main vein, but not after treatment on the midrib. Results are explicable on the basis of the known anatomy of Zea and the translocation of dalapon with assimilates.