Published online by Cambridge University Press: 12 June 2017
Relative vaporization losses of five C14 ring-labeled 2-chloro-4,6-alkylamino-s-triazines were studied at 25 and 60 C. Herbicide solutions in 95% ethanol were deposited on metal planchets, dried and counted at intervals. The herbicides, ranked in order of decreasing volatility, were: trietazine (2-chloro-4-diethylamino-6-ethylamino-s-triazine), ipazine (2-chloro-4-diethylamino-6-isopropylamino-s-triazine), atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), propazine (2-chloro-4,6-bis(isopropylamino)-s-triazine) and simazine (2-chloro-4,6-bis(ethylamino)-s-triazine). Prometone (2-methoxy-4,6-bis (isopropylamino)-s-triazine) and the 2-hydroxy analogues of simazine and propazine, dissolved in water at pH 2–3 (HC1) before plating, showed no detectible loss in 25 hours at 60 C. Foliar penetration and acute toxicity following drop application of the five 2-chloro-triazines and prometone to corn, soybean, tomato, cotton, oat and sorghum appeared to be correlated with their water solubilities. A surfactant tended to enhance activity. Important differences were noted among species, although apparently not related to inherent herbicidal tolerance or susceptibility. Tomato was most sensitive to acute toxicity; soybean cotyledons were least permeable. Basipetal translocation was negligible under all conditions (e.g. 6 herbicides, 6 species, 2 solvents, with or without a surfactant). The 2-hydroxy analogues tended to translocate downward but appeared restricted by acute, acid (pH 2–3) destruction of the transport mechanism. Acropetal (apoplastic) movement of all compounds occurred readily with transpiration, reflecting the vasculature of the species. All 2-chlorotriazines and prometone (but not the two 2-hydroxy compounds) showed pronounced accumulation of C14 in the lysigenous glands of cotton. Root uptake and distribution of C14 within the plant body occurred generally for all compounds and species.