The mode of action of BAS 517 in a susceptible plant species, corn, was investigated using an excised root system and14C-tracer techniques. The root system of a tolerant species, soybean, was used for comparison. When UL-14C- glucose was used as a precursor,14C incorporation into lipids was reduced in BAS 517-treated corn roots, although14C incorporation from UL-14C-glucose into lipids was relatively low. Inhibition of14C incorporation into water-soluble compounds was not definite because of a high degree of variability. Using14C-acetate as a precursor, 49, 43, and 34% of the recovered radioactivity was found in the lipid fractions of root tips treated with 0, 1.0, and 10 μM BAS 517, respectively. In nontreated soybean root tips, 47% of the recovered radioactivity was found in the lipid fraction compared to 49% in root tips treated with 10 μM BAS 517. Further analysis of lipids showed that BAS 517 inhibited the incorporation of14C from14C-acetate into phosphatidylethanolamine, a phospholipid, whereas the labeling of sterols in treated corn roots was not adversely affected. Acetyl CoA carboxylase extracted from root systems of corn and soybean showed different sensitivity to BAS 517, suggesting its role as the herbicide target site and as a basis for the selectivity.
Effect of Valinomycin and Gramicidin D on the Reflection Coefficient of Soybean Root Systems
