Seedlings of wheat were grown for 24 h in control nutrient solution and in solutions containing haloxyfop, alloxydim, diquat or paraquat, and thereafter the roots were used for microsomal preparations. Phosphatidylcholine or diacylglycerol with various 1-(14)C-labelled fatty acids (oleic, linoleic, linolenic or ricinoleic acids) in position sn-2 were added to the prepared microsomes. After incubation for 2 h at 30 degrees C, the lipids were extracted and the distribution of radioactivity among lipid classes was determined. In the microsomal preparations of plants treated with diquat and paraquat, the amounts of fatty acids released were similar to the control, whereas they were 1.4-2 times higher in the microsomal preparation of plants treated with haloxyfop and alloxydim. Thus, the data indicate that graminicides could increase lipid catabolism in sensitive plants and that this is not a general phenomenon connected with inhibition of growth.