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Absorption and translocation of (2,4-dichlorophenoxy)-acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram) were measured in defoliated and intact field bindweed (Convolvulus arvensisL.) plants. Radioactivity was applied as 5 μl of triethylamine salts of 2,4-D and picloram with an activity of 0.15 μc to a middle leaf in intact and partially-defoliated plants. After treatment for 96 hr,14C-activity in untreated leaves, stems, growing tips, and roots was measured. Removal of all leaves significantly reduced absorption but not translocation of both 2,4-D and picloram. A greater percentage of the applied picloram than 2,4-D was absorbed in all treatments. Translocation of14C of both 2,4-D and picloram was greater when (a) upper and lower leaves were removed, (b) upper leaves only were removed, and (c) lower leaves only were removed than (d) when plants were intact. Removal of lower (older) leaves reduced translocation more than removal of upper (younger) leaves.

The effect of stage of growth of field bindweed (Convolvulus arvensis L.) on absorption and translocation of 14C-labeled 2,4-D and picloram was studied. Three stages of growth investigated were s-week old seedlings, and 7-week old and 16-week old vegetatively propagated plants. One middle leaf of each plant was treated with either 14C-labeled (2,4-dichlorophenoxy)-acetic acid (2,4-D) or 4-amino-3,5,6-trichloropicolinic acid (picloram). Treated plants were harvested after 48 hr and assayed for radioactive 14C. The percent of 2,4-D applied which was absorbed by seedlings was less than that absorbed by adult plants. Picloram absorption was not different in seedlings and 7-week old adult plants, but the 16-week old adult plants absorbed more picloram than either the 5-week old seedlings or 7-week old adult plants. More picloram than 2,4-D was absorbed at all stages of growth. Translocation of both 2,4-D and picloram was greater in seedlings than in older plants. No difference was found in amounts of 2,4-D and picloram translocated by adult field bindweed plants. More 2,4-D than picloram was translocated by seedlings.

Field bindweed (Convolvulus arvensisL.) was sprayed with a mixture of (2,4-dichlorophenoxy)acetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram). A mixture of picloram and 2,4-D each at 0.01 lb and 0.001 lb/A killed tops of plants faster than 2,4-D alone or picloram alone at the same rates. Higher rates of 1 lb/A picloram plus 1 lb/A 2,4-D and 0.1 lb/A picloram plus 0.1 lb/A 2,4-D were not consistently synergistic or antagonistic. The percent of plants which produced new growth were 0 for picloram alone at 1 lb/A, 20 for a mixture of 2,4-D and picloram each at 1 lb/A, and 40 for 2,4-D alone at 1 lb/A. Other rates of 0.1 lb/A, 0.01 lb/A, and 0.001 lb/A did not control regrowth of field bindweed. Application of unlabeled picloram simultaneously with14C-2,4-D increased translocation of14C-2,4-D, but the reverse was not true.