STUDIES ON DIFFERENTIAL TOLERANCE OF 2 LAMBS-QUARTERS SELECTIONS TO TRIAZINE HERBICIDES

The uptake, translocation and metabolism of 14C-atrazine [2-chloro-4-(ethylamino)-6 (iso-propylamino)-s-triazine] was investigated in an atrazine-resistant and an atrazine-susceptible selection of lamb''s-quarters (Chenopodium album L.). There were no differences between the 2 selections in foliar or root uptake of 14C-atrazine, or in translocation and accumulation of 14C-atrazine within the plants following root uptake. Both selections metabolized 14C-atrazine hydroxylation, N-dealkylation and conjugation to peptides. Although 14C-atrazine was detoxified more rapidly in roots of the resistant selection, this could not account for the large difference observed in tolerance. The atrazine resistant selection was also resistant to a number of other 2-chloro-, 2-methylthio- and 2-methoxy-s-triazine herbicides, and showed greater tolerance to other heterocyclic herbicides which inhibit photosynthesis than did the susceptible selection.